Sample records for galaxies ii nebular

  1. Nebular Metallicities in Two Isolated Local Void Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A.; Basurah, Hassan

    2014-01-01

    Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

  2. Synthetic nebular emission from massive galaxies - I: origin of the cosmic evolution of optical emission-line ratios

    NASA Astrophysics Data System (ADS)

    Hirschmann, Michaela; Charlot, Stephane; Feltre, Anna; Naab, Thorsten; Choi, Ena; Ostriker, Jeremiah P.; Somerville, Rachel S.

    2017-12-01

    Galaxies occupy different regions of the [O III]λ5007/H β-versus-[N II]λ6584/H α emission-line ratio diagram in the distant and local Universe. We investigate the origin of this intriguing result by modelling self-consistently, for the first time, nebular emission from young stars, accreting black holes (BHs) and older, post-asymptotic giant branch (post-AGB) stellar populations in galaxy formation simulations in a full cosmological context. In post-processing, we couple new-generation nebular-emission models with high-resolution, cosmological zoom-in simulations of massive galaxies to explore which galaxy physical properties drive the redshift evolution of the optical-line ratios [O III]λ5007/H β, [N II]λ6584/H α, [S II]λλ6717, 6731/H α and [O I]λ6300/H α. The line ratios of simulated galaxies agree well with observations of both star-forming and active local Sloan Digital Sky Survey galaxies. Towards higher redshifts, at fixed galaxy stellar mass, the average [O III]/H β is predicted to increase and [N II]/H α, [S II]/H α and [O I]/H α to decrease - widely consistent with observations. At fixed stellar mass, we identify star formation history, which controls nebular emission from young stars via the ionization parameter, as the primary driver of the cosmic evolution of [O III]/H β and [N II]/H α. For [S II]/H α and [O I]/H α, this applies only to redshifts greater than z = 1.5, the evolution at lower redshift being driven in roughly equal parts by nebular emission from active galactic nuclei and post-AGB stellar populations. Instead, changes in the hardness of ionizing radiation, ionized-gas density, the prevalence of BH accretion relative to star formation and the dust-to-metal mass ratio (whose impact on the gas-phase N/O ratio we model at fixed O/H) play at most a minor role in the cosmic evolution of simulated galaxy line ratios.

  3. Properties of z ~ 3-6 Lyman break galaxies. II. Impact of nebular emission at high redshift

    NASA Astrophysics Data System (ADS)

    de Barros, S.; Schaerer, D.; Stark, D. P.

    2014-03-01

    Context. To gain insight on the mass assembly and place constraints on the star formation history (SFH) of Lyman break galaxies (LBGs), it is important to accurately determine their properties. Aims: We estimate how nebular emission and different SFHs affect parameter estimation of LBGs. Methods: We present a homogeneous, detailed analysis of the spectral energy distribution (SED) of ~1700 LBGs from the GOODS-MUSIC catalogue with deep multi-wavelength photometry from the U band to 8 μm to determine stellar mass, age, dust attenuation, and star formation rate. Using our SED fitting tool, which takes into account nebular emission, we explore a wide parameter space. We also explore a set of different star formation histories. Results: Nebular emission is found to significantly affect the determination of the physical parameters for the majority of z ~ 3-6 LBGs. We identify two populations of galaxies by determining the importance of the contribution of emission lines to broadband fluxes. We find that ~65% of LBGs show detectable signs of emission lines, whereas ~35% show weak or no emission lines. This distribution is found over the entire redshift range. We interpret these groups as actively star-forming and more quiescent LBGs, respectively. We find that it is necessary to considerer SED fits with very young ages (<50 Myr) to reproduce some colours affected by strong emission lines. Other arguments favouring episodic star formation and relatively short star formation timescales are also discussed. Considering nebular emission generally leads to a younger age, lower stellar mass, higher dust attenuation, higher star formation rate, and a large scatter in the SFR-M⋆ relation. Our analysis yields a trend of increasing specific star formation rate with redshift, as predicted by recent galaxy evolution models. Conclusions: The physical parameters of approximately two thirds of high redshift galaxies are significantly modified when we account for nebular emission. The

  4. Nebular Continuum and Line Emission in Stellar Population Synthesis Models

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Byler, Nell; Dalcanton, Julianne J.; Conroy, Charlie

    Accounting for nebular emission when modeling galaxy spectral energy distributions (SEDs) is important, as both line and continuum emissions can contribute significantly to the total observed flux. In this work, we present a new nebular emission model integrated within the Flexible Stellar Population Synthesis code that computes the line and continuum emission for complex stellar populations using the photoionization code Cloudy. The self-consistent coupling of the nebular emission to the matched ionizing spectrum produces emission line intensities that correctly scale with the stellar population as a function of age and metallicity. This more complete model of galaxy SEDs will improvemore » estimates of global gas properties derived with diagnostic diagrams, star formation rates based on H α , and physical properties derived from broadband photometry. Our models agree well with results from other photoionization models and are able to reproduce observed emission from H ii regions and star-forming galaxies. Our models show improved agreement with the observed H ii regions in the Ne iii/O ii plane and show satisfactory agreement with He ii emission from z = 2 galaxies, when including rotating stellar models. Models including post-asymptotic giant branch stars are able to reproduce line ratios consistent with low-ionization emission regions. The models are integrated into current versions of FSPS and include self-consistent nebular emission predictions for MIST and Padova+Geneva evolutionary tracks.« less

  5. Nebular and Stellar Dust Extinction Across the Disk of Emission-line Galaxies on Kiloparsec Scales

    NASA Astrophysics Data System (ADS)

    Hemmati, Shoubaneh; Mobasher, Bahram; Darvish, Behnam; Nayyeri, Hooshang; Sobral, David; Miller, Sarah

    2015-11-01

    We investigate the resolved kiloparsec-scale stellar and nebular dust distribution in eight star-forming galaxies at z ∼ 0.4 in the Great Observatories Origins Deep Survey fields. This is to get a better understanding of the effect of dust attenuation on measurements of physical properties and its variation with redshift. Constructing the observed spectral energy distributions (SEDs) per pixel, based on seven bands of photometric data from Hubble Space Telescope/Advanced Camera for Surveys and WFC3, we performed pixel-by-pixel SED fits to population synthesis models and estimated the small-scale distribution of stellar dust extinction. We use Hα/Hβ nebular emission line ratios from Keck/DEIMOS high-resolution spectra at each spatial resolution element to measure the amount of attenuation faced by ionized gas at different radii from the centers of galaxies. We find a good agreement between the integrated and median of resolved color excess measurements in our galaxies. The ratio of integrated nebular to stellar dust extinction is always greater than unity, but does not show any trend with stellar mass or star formation rate (SFR). We find that inclination plays an important role in the variation of the nebular to stellar excess ratio. The stellar color excess profiles are found to have higher values at the center compared to outer parts of the disk. However, for lower mass galaxies, a similar trend is not found for the nebular color excess. We find that the nebular color excess increases with stellar mass surface density. This explains the absence of radial trend in the nebular color excess in lower mass galaxies which lack a large radial variation of stellar mass surface density. Using standard conversions of SFR surface density to gas mass surface density, and the relation between dust mass surface density and color excess, we find no significant variation in the dust-to-gas ratio in regions with high gas mass surface densities over the scales probed in this

  6. NEBULAR AND STELLAR DUST EXTINCTION ACROSS THE DISK OF EMISSION-LINE GALAXIES ON KILOPARSEC SCALES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hemmati, Shoubaneh; Mobasher, Bahram; Darvish, Behnam

    We investigate the resolved kiloparsec-scale stellar and nebular dust distribution in eight star-forming galaxies at z ∼ 0.4 in the Great Observatories Origins Deep Survey fields. This is to get a better understanding of the effect of dust attenuation on measurements of physical properties and its variation with redshift. Constructing the observed spectral energy distributions (SEDs) per pixel, based on seven bands of photometric data from Hubble Space Telescope/Advanced Camera for Surveys and WFC3, we performed pixel-by-pixel SED fits to population synthesis models and estimated the small-scale distribution of stellar dust extinction. We use Hα/Hβ nebular emission line ratios from Keck/DEIMOS high-resolutionmore » spectra at each spatial resolution element to measure the amount of attenuation faced by ionized gas at different radii from the centers of galaxies. We find a good agreement between the integrated and median of resolved color excess measurements in our galaxies. The ratio of integrated nebular to stellar dust extinction is always greater than unity, but does not show any trend with stellar mass or star formation rate (SFR). We find that inclination plays an important role in the variation of the nebular to stellar excess ratio. The stellar color excess profiles are found to have higher values at the center compared to outer parts of the disk. However, for lower mass galaxies, a similar trend is not found for the nebular color excess. We find that the nebular color excess increases with stellar mass surface density. This explains the absence of radial trend in the nebular color excess in lower mass galaxies which lack a large radial variation of stellar mass surface density. Using standard conversions of SFR surface density to gas mass surface density, and the relation between dust mass surface density and color excess, we find no significant variation in the dust-to-gas ratio in regions with high gas mass surface densities over the scales probed

  7. Reconciling the Stellar and Nebular Spectra of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Steidel, Charles C.; Strom, Allison L.; Pettini, Max; Rudie, Gwen C.; Reddy, Naveen A.; Trainor, Ryan F.

    2016-08-01

    We present a combined analysis of rest-frame far-UV (FUV; 1000-2000 Å) and rest-frame optical (3600-7000 Å) composite spectra formed from very deep Keck/LRIS and Keck/MOSFIRE observations of a sample of 30 star-forming galaxies with z=2.40+/- 0.11, selected to be broadly representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the FUV stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity ({Z}* /{Z}⊙ ≃ 0.1) but relatively high nebular (ionized gas-phase) abundances ({Z}{{neb}}/{Z}⊙ ≃ 0.5), can successfully match all of the observational constraints. We show that this apparent discrepancy is naturally explained by highly super-solar O/Fe (≃ 4{--}5 {({{O}}/{Fe})}⊙ ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. While O dominates the physics of the ionized gas (and thus the nebular emission lines), Fe dominates the extreme-UV (EUV) and FUV opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. This high nebular excitation—caused by the hard EUV spectra of Fe-poor massive stars—is much more common at high redshift (z≳ 2) than low redshift due to systematic differences in the star formation history of typical galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

  8. On the Lack of Correlation Between Mg II 2796, 2803 Angstrom and Lyman alpha Emission in Lensed Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Rigby, Jane Rebecca; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.

    2014-01-01

    We examine the Mg II 2796, 2803 Angstrom, Lyman alpha, and nebular line emission in five bright star-forming galaxies at 1.66 less than z less than 1.91 that have been gravitationally lensed by foreground galaxy clusters. All five galaxies show prominent Mg II emission and absorption in a P Cygni profile. We find no correlation between the equivalent widths of Mg II and Lyman alpha emission. The Mg II emission has a broader range of velocities than do the nebular emission line profiles; the Mg II emission is redshifted with respect to systemic by 100 to 200 km s(exp-1). When present, Lyman alpha is even more redshifted. The reddest components of Mg II and Lyman alpha emission have tails to 500-600 km s(exp-1), implying a strong outflow. The lack of correlation in the Mg II and Lyman alpha equivalent widths, the differing velocity profiles, and the high ratios of Mg II to nebular line fluxes together suggest that the bulk of Mg II emission does not ultimately arise as nebular line emission, but may instead be reprocessed stellar continuum emission.

  9. Near-infrared line and continuum emission from the blue dwarf galaxy II Zw 40

    NASA Technical Reports Server (NTRS)

    Joy, Marshall; Lester, Daniel F.

    1988-01-01

    A multicolor analysis of new near-infrared line and continuum measurements indicates that nebular recombination emission and photospheric radiation from young blue stars produce most of the near-infrared continuum emission in the central 6 arcsec of the dwarf galaxy II Zw 40. The derived nebular recombination level is in excellent agreement with independent observations of the radio free-free continuum. It is found that evolved stars, which dominate the near-infrared emission from normal galaxies, contribute no more than 25 percent of the total 2.2 micron flux in the central region of II Zw 40. It is concluded that the total mass of the evolved stellar population in the central 400 pc of the galaxy is less than about two hundred million solar. The total mass of recently formed stars is about two million solar, and the stellar mass ratio is exceptionally large. Thus, II Zw 40 is a quintessential starburst galaxy.

  10. Nebular line emission from z > 7 galaxies in a cosmological simulation: rest-frame UV to optical lines

    NASA Astrophysics Data System (ADS)

    Shimizu, Ikkoh; Inoue, Akio K.; Okamoto, Takashi; Yoshida, Naoki

    2016-10-01

    We have performed very large and high-resolution cosmological hydrodynamic simulations in order to investigate detectability of nebular lines in the rest-frame ultraviolet (UV) to optical wavelength range from galaxies at z > 7. We find that the expected line fluxes are very well correlated with the apparent UV magnitudes. The C IV 1549 Å and C III] 1909 Å lines of galaxies brighter than 26 AB magnitudes are detectable with current facilities such as the Very Large Telescope (VLT) XShooter and the Keck Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE). Metal lines such as C IV 1549 Å, C III] 1909 Å, [O II] 3727 Å and [O III] 4959/5007 Å are good targets for spectroscopic observation with the Thirty-Metre Telescope (TMT), European Extremely Large Telescope (E-ELT), Giant Magellan Telescope (GMT) and James Webb Space Telescope (JWST). We also expect Hα and Hβ lines to be detectable with these telescopes. Additionally, we predict the detectability of nebular lines for z > 10 galaxies, which will be found with JWST, the Wide-Field Infrared Survey Telescope (WFIRST) and First Light And Reionization Explorer (FLARE) (11 ≤ z ≤ 15). We conclude that the C IV 1549 Å, C III] 1909 Å, [O III] 4959/5007 Å and Hβ lines from even z ˜15 galaxies could be strong targets for TMT, E-ELT and JWST. We also find that magnification by gravitational lensing is of great help in detecting such high-z galaxies. According to our model, the C III] 1909 Å line in z > 9 galaxy candidates is detectable even using current facilities.

  11. Nebular Emission Line Ratios in z ≃ 2-3 Star-forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio

    NASA Astrophysics Data System (ADS)

    Strom, Allison L.; Steidel, Charles C.; Rudie, Gwen C.; Trainor, Ryan F.; Pettini, Max; Reddy, Naveen A.

    2017-02-01

    We present a detailed study of the rest-optical (3600-7000 Å) nebular spectra of ˜380 star-forming galaxies at z≃ 2{--}3, obtained with Keck/Multi-object Spectrometer for Infrared Exploration (MOSFIRE) as part of the Keck Baryonic Structure Survey (KBSS). The KBSS-MOSFIRE sample is representative of star-forming galaxies at these redshifts, with stellar masses {M}* ={10}9{--}{10}11.5 {M}⊙ and star formation rates SFR = 3-1000 {M}⊙ yr-1. We focus on robust measurements of many strong diagnostic emission lines for individual galaxies: [O II]λλ3727, 3729, [Ne III]λ3869, Hβ, [O III]λ λ 4960, 5008, [N II]λλ 6549, 6585, Hα, and [S II]λλ6718, 6732. Comparisons with observations of typical local galaxies from the Sloan Digital Sky Survey and between subsamples of KBSS-MOSFIRE show that high-redshift galaxies exhibit a number of significant differences in addition to the well-known offset in log([O III]λ 5008/Hβ) and log([N II]λ 6585/Hα). We argue that the primary difference between H II regions in z˜ 2.3 galaxies and those at z˜ 0 is an enhancement in the degree of nebular excitation, as measured by [O III]/Hβ and {{R}}23\\equiv {log}[([O III]λ λ 4960,5008+[O II]λ λ 3727,3729)/Hβ]. At the same time, KBSS-MOSFIRE galaxies are ˜10 times more massive than z˜ 0 galaxies with similar ionizing spectra and have higher N/O (likely accompanied by higher O/H) at fixed excitation. These results indicate the presence of harder ionizing radiation fields at fixed N/O and O/H relative to typical z˜ 0 galaxies, consistent with Fe-poor stellar population models that include massive binaries, and highlight a population of massive, high-specific star formation rate galaxies at high redshift with systematically different star formation histories than galaxies of similar stellar mass today. The data presented in this paper were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the

  12. Nebular Line Emission and Stellar Mass of Bright z 8 Galaxies "Super-Eights"

    NASA Astrophysics Data System (ADS)

    Holwerda, Benne; Bouwens, Rychard; Trenti, Michele; Oesch, Pascal; Labbe, Ivo; Smit, Renske; Roberts-Borsani, Guido; Bernard, Stephanie; Bridge, Joanna

    2018-05-01

    Searches for the Lyman-alpha emission from the very first galaxies ionizing the Universe have proved to be extremely difficult with limited success beyond z 7 (<3% detections). However, a search of all CANDELS yielded four bright z 8 sources with associated strong Lyman-alpha lines, despite the Universe expected to be 70% neutral at this time. The key to their selection is an extremely red IRAC color ([3.6]-[4.5]> 0.5, Roberts-Borsani+ 2016), indicative of very strong nebular line emission. Do such extreme line emitting galaxies produce most of the photons to reionize the Universe? We propose to expand the sample of bright z 8 galaxies with reliable IRAC colors with seven more Y-band dropouts found with HST and confirmed through HST/Spitzer. The Spitzer observations will test how many of bright z 8 galaxies are IRAC-red and measure both their stellar mass and [OIII]+Hbeta line strength. Together with Keck/VLT spectroscopy, they will address these questions: I) Do all luminous z 8 galaxies show such red IRAC colors ([OIII] emission / hard spectra)? II) Is luminosity or a red IRAC color the dominant predictor for Lyman-alpha emission? III) Or are these sources found along exceptionally transparent sightlines into the early Universe? With 11 bright z 8 sources along different lines-of-sight, all prime targets for JWST, we will aim to determine which of the considered factors (luminosity, color, sight-line) drives the high Lyman-alpha prevalence (100%) and insight into the sources reionizing the Universe.

  13. Ionization correction factors for H II regions in blue compact dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Holovatyi, V. V.; Melekh, B. Ya.

    2002-08-01

    Energy distributions in the spectra of the ionizing nuclei of H II regions beyond λ <= 91.2 nm were calculated. A grid of photoionization models of 270 H II regions was constructed. The free parameters of the model grid are the hydrogen density nH in the nebular gas, filling factor, energy Lc-spectrum of ionizing nuclei, and metallicity. The chemical composition from the studies of Izotov et al. were used for model grid initialization. The integral linear spectra calculated for the photoionization models were used to determine the concentration ne, temperatures Te of electrons, and ionic concentrations n(A+i)/n(H+) by the nebular gas diagnostic method. The averaged relative ionic abundances n(A+i)/n(H+) thus calculated were used to determine new expressions for ionization correction factors which we recommend for the determination of abundances in the H II regions of blue compact dwarf galaxies.

  14. Nebular emission and the Lyman continuum photon escape fraction in CALIFA early-type galaxies

    NASA Astrophysics Data System (ADS)

    Papaderos, P.; Gomes, J. M.; Vílchez, J. M.; Kehrig, C.; Lehnert, M. D.; Ziegler, B.; Sánchez, S. F.; Husemann, B.; Monreal-Ibero, A.; García-Benito, R.; Bland-Hawthorn, J.; Cortijo-Ferrero, C.; de Lorenzo-Cáceres, A.; del Olmo, A.; Falcón-Barroso, J.; Galbany, L.; Iglesias-Páramo, J.; López-Sánchez, Á. R.; Marquez, I.; Mollá, M.; Mast, D.; van de Ven, G.; Wisotzki, L.

    2013-07-01

    We use deep integral field spectroscopy data from the CALIFA survey to study the warm interstellar medium (wim) over the entire extent and optical spectral range of 32 nearby early-type galaxies (ETGs). We find that faint nebular emission is extended in all cases, and its surface brightness decreases roughly as ∝ r-α. The large standard deviation in the derived α (1.09 ± 0.67) argues against a universal power-law index for the radial drop-off of nebular emission in ETGs. Judging from the properties of their extranuclear component, our sample ETGs span a broad, continuous sequence with respect to their α, Hα equivalent width (EW) and Lyman continuum (Lyc) photon leakage fraction (plf). We propose a tentative subdivision into two groups: Type i ETGs are characterized by rather steep Hα profiles (α ≃ 1.4), comparatively large (≳1 Å), nearly radially constant EWs, and plf ≃ 0. Photoionization by post-AGB stars appears to be the main driver of extended nebular emission in these systems, with nonthermal sources being potentially important only in their nuclei. Typical properties of type II ETGs are shallower Hα profiles (α ≃ 0.8), very low (≲0.5 Å) EWs with positive radial gradients, and a mean plf ≳ 0.7, rising to ≳0.9 in their centers. Such properties point to a low, and inwardly decreasing wim density and/or volume filling factor. We argue that, because of extensive Lyc photon leakage, emission-line luminosities and EWs are reduced in type II ETG nuclei by at least one order of magnitude. Consequently, the line weakness of these ETGs is by itself no compelling evidence for their containing merely "weak"(sub-Eddington accreting) active galactic nuclei (AGN). In fact, Lyc photon escape, which has heretofore not been considered, may constitute a key element in understanding why many ETGs with prominent signatures of AGN activity in radio continuum and/or X-ray wavelengths show only faint emission lines and weak signatures of AGN activity in

  15. Dependence of Nebular Heavy-element Abundance on H I Content for Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Robertson, Paul; Shields, Gregory A.; Davé, Romeel; Blanc, Guillermo A.; Wright, Audrey

    2013-08-01

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  16. Extended nebular emission in CALIFA early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gomes, J. M.; Papaderos, P.; Kehrig, C.; Vílchez, J. M.; Lehnert, M. D.

    2015-02-01

    The morphological, spectroscopic and kinematical properties of the warm interstellar medium ( wim ) in early-type galaxies (ETGs) hold key observational constraints to nuclear activity and the buildup history of these massive quiescent systems. High-quality integral field spectroscopy (IFS) data with a wide spectral and spatial coverage, such as those from the CALIFA survey, offer a precious opportunity for advancing our understanding in this respect. We use deep IFS data from CALIFA (califa.caha.es) to study the wim over the entire extent and optical spectral range of 32 nearby ETGs. We find that all ETGs in our sample show faint (Hα equivalent width EW(Hα)~0.5 ... 2 Å) extranuclear nebular emission extending out to >=2 Petrosian50 radii. Confirming and strengthening our conclusions in Papaderos et al. (2013, hereafter P13) we argue that ETGs span a broad continuous sequence with regard to the properties of their wim , and they can be roughly subdivided into two characteristic classes. The first one (type i) comprises ETGs with a nearly constant EW(Hα)~1-3 Å in their extranuclear component, in quantitative agreement with (even though, no proof for) the hypothesis of photoionization by the post-AGB stellar component being the main driver of extended wim emission. The second class (type ii) consists of virtually wim -evacuated ETGs with a large Lyman continuum (Ly c) photon escape fraction and a very low (<=0.5 Å) EW(Hα) in their nuclear zone. These two ETG classes appear indistinguishable from one another by their LINER-specific emission-line ratios. Additionally, here we extend the classification by P13 by the class i+ which stands for a subset of type i ETGs with low-level star-forming activity in contiguous spiral-arm like features in their outermost periphery. These faint features, together with traces of localized star formation in several type i&i+ systems point to a non-negligible contribution from young massive stars to the global ionizing photon

  17. Average [O II] nebular emission associated with Mg II absorbers: dependence on Fe II absorption

    NASA Astrophysics Data System (ADS)

    Joshi, Ravi; Srianand, Raghunathan; Petitjean, Patrick; Noterdaeme, Pasquier

    2018-05-01

    We investigate the effect of Fe II equivalent width (W2600) and fibre size on the average luminosity of [O II] λλ3727, 3729 nebular emission associated with Mg II absorbers (at 0.55 ≤ z ≤ 1.3) in the composite spectra of quasars obtained with 3 and 2 arcsec fibres in the Sloan Digital Sky Survey. We confirm the presence of strong correlations between [O II] luminosity (L_{[O II]}) and equivalent width (W2796) and redshift of Mg II absorbers. However, we show L_{[O II]} and average luminosity surface density suffer from fibre size effects. More importantly, for a given fibre size, the average L_{[O II]} strongly depends on the equivalent width of Fe II absorption lines and found to be higher for Mg II absorbers with R ≡W2600/W2796 ≥ 0.5. In fact, we show the observed strong correlations of L_{[O II]} with W2796 and z of Mg II absorbers are mainly driven by such systems. Direct [O II] detections also confirm the link between L_{[O II]} and R. Therefore, one has to pay attention to the fibre losses and dependence of redshift evolution of Mg II absorbers on W2600 before using them as a luminosity unbiased probe of global star formation rate density. We show that the [O II] nebular emission detected in the stacked spectrum is not dominated by few direct detections (i.e. detections ≥3σ significant level). On an average, the systems with R ≥ 0.5 and W2796 ≥ 2 Å are more reddened, showing colour excess E(B - V) ˜ 0.02, with respect to the systems with R < 0.5 and most likely trace the high H I column density systems.

  18. BOND: A quantum of solace for nebular abundance determinations

    NASA Astrophysics Data System (ADS)

    Vale Asari, N.; Stasińska, G.; Morisset, C.; Cid Fernandes, R.

    2017-11-01

    The abundances of chemical elements other than hydrogen and helium in a galaxy are the fossil record of its star formation history. Empirical relations such as mass-metallicity relation are thus seen as guides for studies on the history and chemical evolution of galaxies. Those relations usually rely on nebular metallicities measured with strong-line methods, which assume that H II regions are a one- (or at most two-) parameter family where the oxygen abundance is the driving quantity. Nature is however much more complex than that, and metallicities from strong lines may be strongly biased. We have developed the method BOND (Bayesian Oxygen and Nitrogen abundance Determinations) to simultaneously derive oxygen and nitrogen abundances in giant H II regions by comparing strong and semi-strong observed emission lines to a carefully-defined, finely-meshed grid of photoionization models. Our code and results are public and available at http://bond.ufsc.br.

  19. The multifaceted Type II-L supernova 2014G from pre-maximum to nebular phase

    NASA Astrophysics Data System (ADS)

    Terreran, G.; Jerkstrand, A.; Benetti, S.; Smartt, S. J.; Ochner, P.; Tomasella, L.; Howell, D. A.; Morales-Garoffolo, A.; Harutyunyan, A.; Kankare, E.; Arcavi, I.; Cappellaro, E.; Elias-Rosa, N.; Hosseinzadeh, G.; Kangas, T.; Pastorello, A.; Tartaglia, L.; Turatto, M.; Valenti, S.; Wiggins, P.; Yuan, F.

    2016-10-01

    We present multiband ultraviolet, optical, and near-infrared photometry, along with visual-wavelength spectroscopy, of supernova (SN) 2014G in the nearby galaxy NGC 3448 (25 Mpc). The early-phase spectra show strong emission lines of the high ionization species He II/N IV/C IV during the first 2-3 d after explosion, traces of a metal-rich circumstellar material (CSM) probably due to pre-explosion mass-loss events. These disappear by day 9 and the spectral evolution then continues matching that of normal Type II SNe. The post-maximum light curve declines at a rate typical of Type II-L class. The extensive photometric coverage tracks the drop from the photospheric stage and constrains the radioactive tail, with a steeper decline rate than that expected from the 56Co decay if γ-rays are fully trapped by the ejecta. We report the appearance of an unusual feature on the blue side of H α after 100 d, which evolves to appear as a flat spectral feature linking H α and the [O I] doublet. This may be due to interaction of the ejecta with a strongly asymmetric, and possibly bipolar CSM. Finally, we report two deep spectra at ˜190 and 340 d after explosion, the latter being arguably one of the latest spectra for a Type II-L SN. By modelling the spectral region around the [Ca II], we find a supersolar Ni/Fe production. The strength of the [O I] λλ6300,6363 doublet, compared with synthetic nebular spectra, suggests a progenitor with a zero-age main-sequence mass between 15 and 19 M⊙.

  20. A New Probe of Dust Attenuation in Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Leitherer, Claus

    2017-08-01

    We propose to develop, calibrate and test a new technique to measure dust attenuation in star-forming galaxies. The technique utilizes the strong stellar-wind emission lines in Wolf-Rayet stars, which are routinely observed in galaxy spectra locally and up to redshift 3. The He II 1640 and 4686 features are recombination lines whose intrinsic ratio is almost exclusively determined by atomic physics. Therefore it can serve as a stellar dust probe in the same way as the nebular hydrogen-line ratio can be used to measure the reddening of the gas phase. Archival spectra of Wolf-Rayet stars will be analyzed to calibrate the method, and panchromatic FOS and STIS spectra of nearby star-forming galaxies will be used as a first application. The new technique allows us to study stellar and nebular attenuation in galaxies separately and to test its effects at different stellar age and mass regimes.

  1. A Close Relationship between Lyα and Mg II in Green Pea Galaxies

    NASA Astrophysics Data System (ADS)

    Henry, Alaina; Berg, Danielle A.; Scarlata, Claudia; Verhamme, Anne; Erb, Dawn

    2018-03-01

    The Mg II λλ2796, 2803 doublet is often used to measure interstellar medium absorption in galaxies, thereby serving as a diagnostic for feedback and outflows. However, the interpretation of Mg II remains confusing, due to resonant trapping and re-emission of the photons, analogous to Lyα. Therefore, in this paper, we present new MMT Blue Channel Spectrograph observations of Mg II for a sample of 10 Green Pea galaxies at z ∼ 0.2–0.3, where Lyα was previously observed with the Cosmic Origins Spectrograph on the Hubble Space Telescope. With strong, (mostly) double-peaked Lyα profiles, these galaxies allow us to observe Mg II in the limit of low H I column density. We find strong Mg II emission and little-to-no absorption. We use photoionization models to show that nebular Mg II from H II regions is non-negligible, and the ratios of Mg II λλ2796, 2803/[O III] λ5007 versus [O III] λ5007/[O II] λ3727 form a tight sequence. Using this relation, we predict intrinsic Mg II flux, and show that Mg II escape fractions range from 0 to 0.9. We find that the Mg II escape fraction correlates tightly with the Lyα escape fraction, and the Mg II line profiles show evidence for broader and more redshifted emission when the escape fractions are low. These trends are expected if the escape fractions and velocity profiles of Lyα and Mg II are shaped by resonant scattering in the same low column density gas. As a consequence of a close relation with Lyα, Mg II may serve as a useful diagnostic in the epoch of reionization, where Lyα and Lyman continuum photons are not easily observed.

  2. The peculiar type II supernova 1993J in M81: Transition to the nebular phase

    NASA Technical Reports Server (NTRS)

    Filippenko, Alexei V.; Matheson, Thomas; Barth, Aaron J.

    1994-01-01

    We present optical spectra of the bright, peculiar Type II supernova 1993J in M81 spanning the first 14 months of its existence, revealing its transition to the nebular phase. Unlike the case in normal Type II supernovae, during the first 2-10 months the H-alpha emission line gradually becomes less prominent relative to other features such as (O I) lambda lambda 6300, 6364 and (Ca II) lambda lambda 7291, 7324, as we had predicted based on early-time (tau less than or approximately equal to 2 months) spectra. The nebular spectrum resembles those of the Type Ib/Ic supernovae 1985F and 1987M, although weak H-alpha emission is easily visible even at late times in SN 1993J. At tau = 8 months a close similarity is found with the spectrum of SN 1987K, the only other Type II supernova known to have undergone such a metamorphosis. The emission lines are considerably broader than those of normal Type II supernovae at comparable phases, consistent with the progenitor having lost a majority of its hydrogen envelope prior to exploding. Consequently, there is now little doubt that Type Ib, and probably Type Ic, supernovae result from core collapse in stripped, massive stars; models of the chemical evolution of galaxies in which these subtypes are ascribed to exploding white dwarfs must be appropriately modified. Although all of the emission lines in spectra of SN 1993J fade roughly exponentially for a considerable time, the fading of H-alpha begins to slow down at tau approximately = 8 months, and in the interval tau = 10-14 months its flux is constant, or even slightly rising in the wings of the line. This behavior, together with the box-like shape and great breadth (full width at half maximum (FWHM) approximately = 17 000 km/s) of the line profile, suggests that the H-alpha emission is being produced by the high-velocity outer layer of hydrogen ejecta interacting with circumstellar gas released by the progenitor prior to its explosion. A similar phenomenon has previously been

  3. The II Zw 40 Supernebula

    NASA Astrophysics Data System (ADS)

    Leitherer, C.; Byler, N.; Lee, J. C.; Levesque, E. M.

    2017-11-01

    We obtained HST COS G140L spectroscopy of the enigmatic nearby blue compact dwarf galaxy II Zw 40. The galaxy hosts a nuclear super star cluster with a luminosity 10 times that of 30 Doradus, the most powerful giant HII region in the Local Group. The super star cluster has been suggested to be the ionizing source of a ”supernebula” detected via its free-free radiation in the radio. The physical conditions, however, are much more complex, as demonstrated by the detection of the nebular He II and the mid-infrared line of [O IV] 25.9. These lines are unlikely to be related to hot stars and require a different powering source. II Zw 40 shares many similarities with the related blue compact dwarfs NGC 5253 and Henize 2-10. However, II Zw 40’s UV spectrum is unique in terms of the exceptional strength of He II 1640, O III 1663 and CIII 1909. We determined reddening, age, and the stellar initial mass function and perform a comparison with the local benchmark 30 Doradus. Photoionization modeling is used to determine the origin of the nebular lines as due to stellar ionization, shocks, or powering by a black hole.

  4. Extreme Wolf-Rayet Galaxies with HST/COS: Understanding CIII] Emission in the Reionization Era

    NASA Astrophysics Data System (ADS)

    Stark, Daniel

    2017-08-01

    The first deep spectra of reionization-era galaxies have revealed strong UV nebular emission in high-ionization lines. This is in striking contrast to massive galaxies at lower redshifts, where emission from CIII], OIII], HeII, and CIV is rarely seen. These lines will likely be the only probe available for the most distant galaxies JWST will detect; but we are still unprepared to interpret them. Modeling predicts that intense UV nebular emission can only be produced below a tenth solar metallicity. However, recent HST/COS observations of local galaxies suggest that extreme populations of Wolf-Rayet (WR) stars, the hot exposed cores of massive O stars, may be capable of powering CIII] at metallicities as high as a half-solar. If these moderately metal-poor extreme WR galaxies are indeed a viable source of strong CIII] emission, our interpretation of CIII] detections in the reionization era will be dramatically altered; but we presently have sufficient UV coverage for only three examples. Here, we propose HST/COS G160M and G185M observations of an additional seven extreme WR galaxies spanning 0.5 dex in metallicity around half-solar. These observations will constrain the maximum CIII] equivalent width these galaxies can power as a function of metallicity. The moderate resolution gratings will robustly characterize the massive O and WR star populations, allowing us to link the nebular emission directly to the massive stars responsible. These data will provide a stringent test for the population synthesis codes which will be applied to JWST observations. Without this empirical baseline, our understanding of the most distant galaxies JWST finds will be severely limited.

  5. Optical spectrophotometry of Wolf-Rayet galaxies

    NASA Technical Reports Server (NTRS)

    Vacca, William D.; Conti, Peter S.

    1992-01-01

    We have obtained long-slit optical spectra of 10 Wolf-Rayet galaxies and four other starburst galaxies. Using the nebular emission lines we have determined the electron temperatures, electron densities, extinctions, oxygen abundances, mass of ionized hydrogen, and numbers of ionizing photons due to hot stars in these galaxies. The various forbidden line ratios clearly indicate a stellar origin for the emission-line spectrum. From the flux of the broad He II 4686 A emission feature we have estimated the number of Wolf-Rayet stars present. We have accounted for the contribution of these stars to the total ionizing flux and have calculated the ratio of the number of these stars to the number of O stars. Wolf-Rayet galaxies are among the youngest examples of the starburst phenomenon, which we observed at a propitious moment.

  6. Internal Variations in Empirical Oxygen Abundances for Giant H II Regions in the Galaxy NGC 2403

    NASA Astrophysics Data System (ADS)

    Mao, Ye-Wei; Lin, Lin; Kong, Xu

    2018-02-01

    This paper presents a spectroscopic investigation of 11 {{H}} {{II}} regions in the nearby galaxy NGC 2403. The {{H}} {{II}} regions are observed with a long-slit spectrograph mounted on the 2.16 m telescope at XingLong station of National Astronomical Observatories of China. For each of the {{H}} {{II}} regions, spectra are extracted at different nebular radii along the slit-coverage. Oxygen abundances are empirically estimated from the strong-line indices R23, N2O2, O3N2, and N2 for each spectrophotometric unit, with both observation- and model-based calibrations adopted into the derivation. Radial profiles of these diversely estimated abundances are drawn for each nebula. In the results, the oxygen abundances separately estimated with the prescriptions on the basis of observations and models, albeit from the same spectral index, systematically deviate from each other; at the same time, the spectral indices R23 and N2O2 are distributed with flat profiles, whereas N2 and O3N2 exhibit apparent gradients with the nebular radius. Because our study naturally samples various ionization levels, which inherently decline at larger radii within individual {{H}} {{II}} regions, the radial distributions indicate not only the robustness of R23 and N2O2 against ionization variations but also the sensitivity of N2 and O3N2 to the ionization parameter. The results in this paper provide observational corroboration of the theoretical prediction about the deviation in the empirical abundance diagnostics. Our future work is planned to investigate metal-poor {{H}} {{II}} regions with measurable T e, in an attempt to recalibrate the strong-line indices and consequently disclose the cause of the discrepancies between the empirical oxygen abundances.

  7. Far-Infrared and Nebular Star-Formation Rate of Dusty Star Forming Galaxies from Herschel, CANDELS and 3D-HST at z~1

    NASA Astrophysics Data System (ADS)

    Hasan, Farhanul; Nayyeri, Hooshang; Cooray, Asantha R.; Herschel Group: University of California Irvine. Dept. of Physics & Astronomy. Led by professor Asantha Cooray, Reed College Undergraduate Research Committee

    2017-06-01

    We present a combined Herschel/PACS and SPIRE and HST/WFC3 observations of the five CANDELS fields, EGS, GOODS-N, GOODS-S, COSMOS and UDS, to study star-formation activity in dusty star-forming galaxies (DSFGs) at z~1. We use 3D-HST photometry and Grism spectroscopic redshifts to construct the Spectral Energy Distributions (SED) of galaxies in the near UV, optical and near infrared, along with IRAC measurements at 3.6-8 μm in the mid-infrared, and Herschel data at 250-500 μm in the far-infrared. The 3D-HST grism line measurements are used to estimate the star-formation rate from nebular emission. In particular, we compare the H-alpha measured SFRs (corrected for attenuation) to that of direct observations of the far-infrared from Herschel. We further look at the infrared excess in this sample of dusty star-forming galaxies (denoted by LIR/LUV) as a function of the UV slope. We find that the population of high-z DSFGs sit above the trend expected for normal star-forming galaxies. Additionally, we study the dependence of SFR on total dust attenuation and confirm a strong correlation between SFR(Ha) and the balmer decrement (Hα/Hβ).

  8. A GMOS-N IFU study of the central H II region in the blue compact dwarf galaxy NGC 4449: kinematics, nebular metallicity and star formation

    NASA Astrophysics Data System (ADS)

    Kumari, Nimisha; James, Bethan L.; Irwin, Mike J.

    2017-10-01

    We use integral field spectroscopic (IFS) observations from the Gemini Multi-Object Spectrograph North (GMOS-N) to study the central H II region in a nearby blue compact dwarf (BCD) galaxy NGC 4449. The IFS data enable us to explore the variation of physical and chemical conditions of the star-forming region and the surrounding gas on spatial scales as small as 5.5 pc. Our kinematical analysis shows possible signatures of shock ionization and shell structures in the surroundings of the star-forming region. The metallicity maps of the region, created using direct Te and indirect strong line methods (R23, O3N2 and N2), do not show any chemical variation. From the integrated spectrum of the central H II region, we find a metallicity of 12 + log(O/H) = 7.88 ± 0.14 ({˜ }0.15^{+0.06}_{-0.04} Z⊙) using the direct method. Comparing the central H II region metallicity derived here with those of H II regions throughout this galaxy from previous studies, we find evidence of increasing metallicity with distance from the central nucleus. Such chemical inhomogeneities can be due to several mechanisms, including gas loss via supernova blowout, galactic winds or metal-poor gas accretion. However, we find that the localized area of decreased metallicity aligns spatially with the peak of star-forming activity in the galaxy, suggesting that gas accretion may be at play here. Spatially resolved IFS data for the entire galaxy are required to confirm the metallicity inhomogeneity found in this study and determine its possible cause.

  9. Physical Conditions of the Interstellar Medium in Star-forming Galaxies at z1.5

    NASA Technical Reports Server (NTRS)

    Hayashi, Masao; Ly, Chun; Shimasaku, Kazuhiro; Motohara, Kentaro; Malkan, Matthew A.; Nagao, Tohru; Kashikawa, Nobunari; Goto, Ryosuke; Naito, Yoshiaki

    2015-01-01

    We present results from Subaru/FMOS near-infrared (NIR) spectroscopy of 118 star-forming galaxies at z approximately equal to 1.5 in the Subaru Deep Field. These galaxies are selected as [O II] lambda 3727 emitters at z approximately equal to 1.47 and 1.62 from narrow-band imaging. We detect H alpha emission line in 115 galaxies, [O III] lambda 5007 emission line in 45 galaxies, and H Beta, [N II] lambda 6584, and [S II]lambda lambda 6716, 6731 in 13, 16, and 6 galaxies, respectively. Including the [O II] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate physical conditions of the interstellar medium in star-forming galaxies at z approximately equal to 1.5. We find a tight correlation between H alpha and [O II], which suggests that [O II] can be a good star formation rate (SFR) indicator for galaxies at z approximately equal to 1.5. The line ratios of H alpha / [O II] are consistent with those of local galaxies. We also find that [O II] emitters have strong [O III] emission lines. The [O III]/[O II] ratios are larger than normal star-forming galaxies in the local Universe, suggesting a higher ionization parameter. Less massive galaxies have larger [O III]/[O II] ratios. With evidence that the electron density is consistent with local galaxies, the high ionization of galaxies at high redshifts may be attributed to a harder radiation field by a young stellar population and/or an increase in the number of ionizing photons from each massive star.

  10. Physical conditions of the interstellar medium in star-forming galaxies at z ˜ 1.5

    NASA Astrophysics Data System (ADS)

    Hayashi, Masao; Ly, Chun; Shimasaku, Kazuhiro; Motohara, Kentaro; Malkan, Matthew A.; Nagao, Tohru; Kashikawa, Nobunari; Goto, Ryosuke; Naito, Yoshiaki

    2015-10-01

    We present results from Subaru Fiber Multi Object Spectrograph near-infrared spectroscopy of 118 star-forming galaxies at z ˜ 1.5 in the Subaru Deep Field. These galaxies are selected as [O II]λ3727 emitters at z ≈ 1.47 and 1.62 from narrow-band imaging. We detect the Hα emission line in 115 galaxies, the [O III]λ5007 emission line in 45 galaxies, and Hβ, [N II]λ6584, and [S II]λλ6716, 6731 in 13, 16, and 6 galaxies, respectively. Including the [O II] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate the physical conditions of the interstellar medium in star-forming galaxies at z ˜ 1.5. We find a tight correlation between Hα and [O II], which suggests that [O II] can be a good star formation rate indicator for galaxies at z ˜ 1.5. The line ratios of Hα/[O II] are consistent with those of local galaxies. We also find that [O II] emitters have strong [O III] emission lines. The [O III]/[O II] ratios are larger than normal star-forming galaxies in the local universe, suggesting a higher ionization parameter. Less massive galaxies have larger [O III]/[O II] ratios. With evidence that the electron density is consistent with local galaxies, the high ionization of galaxies at high redshifts may be attributed to a harder radiation field by a young stellar population and/or an increase in the number of ionizing photons from each massive star.

  11. On the determination of the number of O stars in H II regions and starburst galaxies

    NASA Technical Reports Server (NTRS)

    Vacca, William D.

    1994-01-01

    The hot star population in H II regions, H II galaxies, and starburst galaxies is often described in terms of the number of 'equivalent' O stars of a single representative subtype and luminosity class needed to produce the ionizing luminosity deduced from the nebular recombination lines in the optical spectra. In this paper we define conversion factors eta(sub 0), eta(sub 1), and zeta(sub 5000) with which the total number of O V stars and their flux contribution at 5000 A can be derived from the number of these 'equivalent' stars. These quantities depend primarily on three parameters: the slope and upper mass limit of the stellar mass function and the metallicity of the region. Using the latest stellar atmosphere and evolution models, we calculate eta(sub 0), eta(sub 1), and zeta(sub 5000) for a large number of values of these parameters. The results are presented in tabular as well as graphical form. We apply our results to two H II regions for which the hot star population are known and find that the predicted numbers of O stars agree well the observed counts. In addition, we describe a method by which the values of eta(sub 0) and eta(sub 1) and the observed emission-line fluxes can be used to place constraints on the allowed values of the slope and upper mass limit of the stellar mass function in a region.

  12. A photometrically and spectroscopically confirmed population of passive spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fraser-McKelvie, Amelia; Brown, Michael J. I.; Pimbblet, Kevin A.; Dolley, Tim; Crossett, Jacob P.; Bonne, Nicolas J.

    2016-10-01

    We have identified a population of passive spiral galaxies from photometry and integral field spectroscopy. We selected z < 0.035 spiral galaxies that have WISE colours consistent with little mid-infrared emission from warm dust. Matched aperture photometry of 51 spiral galaxies in ultraviolet, optical and mid-infrared show these galaxies have colours consistent with passive galaxies. Six galaxies form a spectroscopic pilot study and were observed using the Wide-Field Spectrograph to check for signs of nebular emission from star formation. We see no evidence of substantial nebular emission found in previous red spiral samples. These six galaxies possess absorption-line spectra with 4000 Å breaks consistent with an average luminosity-weighted age of 2.3 Gyr. Our photometric and integral field spectroscopic observations confirm the existence of a population of local passive spiral galaxies, implying that transformation into early-type morphologies is not required for the quenching of star formation.

  13. Emission-line diagnostics of nearby H II regions including interacting binary populations

    NASA Astrophysics Data System (ADS)

    Xiao, Lin; Stanway, Elizabeth R.; Eldridge, J. J.

    2018-06-01

    We present numerical models of the nebular emission from H II regions around young stellar populations over a range of compositions and ages. The synthetic stellar populations include both single stars and interacting binary stars. We compare these models to the observed emission lines of 254 H II regions of 13 nearby spiral galaxies and 21 dwarf galaxies drawn from archival data. The models are created using the combination of the BPASS (Binary Population and Spectral Synthesis) code with the photoionization code CLOUDY to study the differences caused by the inclusion of interacting binary stars in the stellar population. We obtain agreement with the observed emission line ratios from the nearby star-forming regions and discuss the effect of binary-star evolution pathways on the nebular ionization of H II regions. We find that at population ages above 10 Myr, single-star models rapidly decrease in flux and ionization strength, while binary-star models still produce strong flux and high [O III]/H β ratios. Our models can reproduce the metallicity of H II regions from spiral galaxies, but we find higher metallicities than previously estimated for the H II regions from dwarf galaxies. Comparing the equivalent width of H β emission between models and observations, we find that accounting for ionizing photon leakage can affect age estimates for H II regions. When it is included, the typical age derived for H II regions is 5 Myr from single-star models, and up to 10 Myr with binary-star models. This is due to the existence of binary-star evolution pathways, which produce more hot Wolf-Rayet and helium stars at older ages. For future reference, we calculate new BPASS binary maximal starburst lines as a function of metallicity, and for the total model population, and present these in Appendix A.

  14. Type II supernovae in low luminosity host galaxies

    NASA Astrophysics Data System (ADS)

    Gutiérrez, C. P.; Anderson, J. P.; Sullivan, M.; Dessart, L.; González-Gaitan, S.; Galbany, L.; Dimitriadis, G.; Arcavi, I.; Bufano, F.; Chen, T.-W.; Dennefeld, M.; Gromadzki, M.; Haislip, J. B.; Hosseinzadeh, G.; Howell, D. A.; Inserra, C.; Kankare, E.; Leloudas, G.; Maguire, K.; McCully, C.; Morrell, N.; E, F. Olivares; Pignata, G.; Reichart, D. E.; Reynolds, T.; Smartt, S. J.; Sollerman, J.; Taddia, F.; Takáts, K.; Terreran, G.; Valenti, S.; Young, D. R.

    2018-06-01

    We present an analysis of a new sample of type II core-collapse supernovae (SNe II) occurring within low-luminosity galaxies, comparing these with a sample of events in brighter hosts. Our analysis is performed comparing SN II spectral and photometric parameters and estimating the influence of metallicity (inferred from host luminosity differences) on SN II transient properties. We measure the SN absolute magnitude at maximum, the light-curve plateau duration, the optically thick duration, and the plateau decline rate in the V -band, together with expansion velocities and pseudo-equivalent-widths (pEWs) of several absorption lines in the SN spectra. For the SN host galaxies, we estimate the absolute magnitude and the stellar mass, a proxy for the metallicity of the host galaxy. SNe II exploding in low luminosity galaxies display weaker pEWs of Fe II λ5018, confirming the theoretical prediction that metal lines in SN II spectra should correlate with metallicity. We also find that SNe II in low-luminosity hosts have generally slower declining light curves and display weaker absorption lines. We find no relationship between the plateau duration or the expansion velocities with SN environment, suggesting that the hydrogen envelope mass and the explosion energy are not correlated with the metallicity of the host galaxy. This result supports recent predictions that mass-loss for red supergiants is independent of metallicity.

  15. Interaction effects on galaxy pairs with Gemini/GMOS- III: stellar population synthesis

    NASA Astrophysics Data System (ADS)

    Krabbe, A. C.; Rosa, D. A.; Pastoriza, M. G.; Hägele, G. F.; Cardaci, M. V.; Dors, O. L., Jr.; Winge, C.

    2017-05-01

    We present an observational study of the impacts of interactions on the stellar population in a sample of galaxy pairs. Long-slit spectra in the wavelength range 3440-7300 Å obtained with the Gemini Multi-Object Spectrograph (GMOS) at Gemini South for 15 galaxies in nine close pairs were used. The spatial distributions of the stellar population contributions were obtained using the stellar population synthesis code starlight. Taking into account the different contributions to the emitted light, we found that most of the galaxies in our sample are dominated by young/intermediate stellar populations. This result differs from the one derived for isolated galaxies, where the old stellar population dominates the disc surface brightness. We interpreted such different behaviour as being due to the effect of gas inflows along the discs of interacting galaxies on the star formation over a time-scale of the order of about 2 Gyr. We also found that, in general, the secondary galaxy of a pair has a higher contribution from the young stellar population than the primary one. We compared the estimated values of stellar and nebular extinction derived from the synthesis method and the Hα/Hβ emission-line ratio, finding that nebular extinctions are systematically higher than stellar ones by about a factor of 2. We did not find any correlation between nebular and stellar metallicities. Neither did we find a correlation between stellar metallicities and ages, while a positive correlation between nebular metallicities and stellar ages was obtained, with older regions being the most metal-rich.

  16. Inferring physical properties of galaxies from their emission-line spectra

    NASA Astrophysics Data System (ADS)

    Ucci, G.; Ferrara, A.; Gallerani, S.; Pallottini, A.

    2017-02-01

    We present a new approach based on Supervised Machine Learning algorithms to infer key physical properties of galaxies (density, metallicity, column density and ionization parameter) from their emission-line spectra. We introduce a numerical code (called GAME, GAlaxy Machine learning for Emission lines) implementing this method and test it extensively. GAME delivers excellent predictive performances, especially for estimates of metallicity and column densities. We compare GAME with the most widely used diagnostics (e.g. R23, [N II] λ6584/Hα indicators) showing that it provides much better accuracy and wider applicability range. GAME is particularly suitable for use in combination with Integral Field Unit spectroscopy, both for rest-frame optical/UV nebular lines and far-infrared/sub-millimeter lines arising from photodissociation regions. Finally, GAME can also be applied to the analysis of synthetic galaxy maps built from numerical simulations.

  17. NEBULAR: Spectrum synthesis for mixed hydrogen-helium gas in ionization equilibrium

    NASA Astrophysics Data System (ADS)

    Schirmer, Mischa

    2016-08-01

    NEBULAR synthesizes the spectrum of a mixed hydrogen helium gas in collisional ionization equilibrium. It is not a spectral fitting code, but it can be used to resample a model spectrum onto the wavelength grid of a real observation. It supports a wide range of temperatures and densities. NEBULAR includes free-free, free-bound, two-photon and line emission from HI, HeI and HeII. The code will either return the composite model spectrum, or, if desired, the unrescaled atomic emission coefficients. It is written in C++ and depends on the GNU Scientific Library (GSL).

  18. VizieR Online Data Catalog: Cobalt emission in nebular phase spectra (Childress+, 2015)

    NASA Astrophysics Data System (ADS)

    Childress, M. J.; Hillier, D. J.; Seitenzahl, I.; Sullivan, M.; Maguire, K.; Taubenberger, S.; Scalzo, R.; Ruiter, A.; Blagorodnova, N.; Camacho, Y.; Castillo, J.; Elias-Rosa, N.; Fraser, M.; Gal-Yam, A.; Graham, M.; Howell, D. A.; Inserra, C.; Jha, S. W.; Kumar, S.; Mazzali, P. A.; McCully, C.; Morales-Garoffolo, A.; Pandya, V.; Polshaw, J.; Schmidt, B.; Smartt, S.; Smith, K. W.; Sollerman, J.; Spyromilio, J.; Tucker, B.; Valenti, S.; Walton, N.; Wolf, C.; Yaron, O.; Young, D. R.; Yuan, F.; Zhang, B.

    2018-01-01

    The analysis in this work relies on a compilation of SN Ia nebular spectra from the literature as well as new observations. We obtained new late-phase (+50=nebular (t>=+150 d) spectra of several nearby SNe Ia from numerous telescopes. Several late-phase spectra of very nearby SNe Ia were collected with the Wide Field Spectrograph (WiFeS; Dopita et al. 2007Ap&SS.310..255D, 2010Ap&SS.327..245D) on the Australian National University (ANU) 2.3 m telescope at Siding Spring Observatory in northern New South Wales, Australia. New nebular spectra for three nearby SNe Ia were collected with DEIMOS (Faber et al. 2003SPIE.4841.1657F) on the Keck-II telescope on Mauna Kea, Hawaii. (4 data files).

  19. The Star Formation Reference Survey - II. Activity demographics and host-galaxy properties for infrared-selected galaxies

    NASA Astrophysics Data System (ADS)

    Maragkoudakis, A.; Zezas, A.; Ashby, M. L. N.; Willner, S. P.

    2018-04-01

    We present activity demographics and host-galaxy properties of infrared-selected galaxies in the local Universe, using the representative Star Formation Reference Survey (SFRS). Our classification scheme is based on a combination of optical emission-line diagrams (BPT) and infrared (IR)-colour diagnostics. Using the weights assigned to the SFRS galaxies based on its parent sample, a far-IR-selected sample comprises 71 per cent H II galaxies, 13 per cent Seyferts, 3 per cent transition objects (TOs), and 13 per cent low-ionization nuclear emission-line regions (LINERs). For the SFRS H II galaxies, we derive nuclear star formation rates and gas-phase metallicities. We measure host-galaxy metallicities for all galaxies with available long-slit spectroscopy and abundance gradients for a subset of 12 face-on galaxies. The majority of H II galaxies show a narrow range of metallicities, close to solar, and flat metallicity profiles. Based on their host-galaxy and nuclear properties, the dominant ionizing source in the far-infrared selected TOs is star-forming activity. LINERs are found mostly in massive hosts (median of 1010.5 M⊙), median L(60 μm) = 109 L⊙, median dust temperatures of F60/F100 = 0.36, and median LH α surface density of 1040.2 erg s-1kpc-2, indicating older stellar populations as their main ionizing source rather than active galactic nucleus activity.

  20. The II Zw 40 Supernebula: 30 Doradus on Steroids

    NASA Astrophysics Data System (ADS)

    Leitherer, Claus

    2015-10-01

    We propose COS G140L spectroscopy of the enigmatic nearby blue compact dwarf galaxy II Zw 40. The galaxy hosts a nuclear super star cluster with a luminosity 10 times that of 30 Doradus, the most powerful giant HII region in the Local Group. The super star cluster has been suggested to be the ionizing source of a supernebula detected via its free-free radiation in the radio. The physical conditions, however, are much more complex, as demonstrated by the detection of the nebular He II and the mid-infrared line of [O IV] 25.9. These lines are unlikely to be related to hot stars and require a different powering source. II Zw 40 shares many similarities with the related blue compact dwarfs NGC 5253 and Henize 2-10, both of which have been studied extensively with HST, yet no ultraviolet spectroscopy has ever been obtained for II Zw 40. This small 4-orbit proposal will provide the necessary UV data to study the massive-star content directly. We will determine reddening, age, and the stellar initial mass function and perform a comparison with the local benchmark 30 Doradus. In particular we will investigate whether the hot stars are able to power the supernebula and the nebular high-excitation lines. Our modeling will utilize the latest generation of stellar evolutionary tracks with and without stellar rotation. If the stars fall short in terms of spectral hardness and luminosity, II Zw 40 may become the second candidate for a central black hole in a young starburst after Henize 2-10.

  1. Mg II-Absorbing Galaxies in the UltraVISTA Survey

    NASA Astrophysics Data System (ADS)

    Stroupe, Darren; Lundgren, Britt

    2018-01-01

    Light that is emitted from distant quasars can become partially absorbed by intervening gaseous structures, including galaxies, in its path toward Earth, revealing information about the chemical content, degree of ionization, organization and evolution of these structures through time. In this project, quasar spectra are used to probe the halos of foreground galaxies at a mean redshift of z=1.1 in the COSMOS Field. Mg II absorption lines in Sloan Digital Sky Survey quasar spectra are paired with galaxies in the UltraVISTA catalog at an impact parameter less than 200 kpc. A sample of 77 strong Mg II absorbers with a rest-frame equivalent width ≥ 0.3 Å and redshift from 0.34 < z < 2.21 are investigated to find equivalent width ratios of Mg II, C IV and Fe II absorption lines, and their relation to the impact parameter and the star formation rates, stellar masses, environments and redshifts of their host galaxies.

  2. Stellar populations in local star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Perez-Gonzalez, P. G.

    2003-11-01

    The main goal of this thesis work is studying the main properties of the stellar populations embedded in a statistically complete sample of local active star-forming galaxies: the Universidad Complutense de Madrid (UCM) Survey of emission-line galaxies. This sample contains 191 local star-forming galaxies at an average redshift of 0.026. The survey was carried out using an objective-prism technique centered at the wavelength of the Halpha nebular emission-line (a common tracer of recent star formation). (continues)

  3. Revealing the nebular properties and Wolf-Rayet population of IC10 with Gemini/GMOS

    NASA Astrophysics Data System (ADS)

    Tehrani, Katie; Crowther, Paul A.; Archer, I.

    2017-12-01

    We present a deep imaging and spectroscopic survey of the Local Group irregular galaxy IC10 using Gemini North and GMOS to unveil its global Wolf-Rayet (WR) population. We obtain a star formation rate (SFR) of 0.045 ± 0.023 M⊙ yr-1, for IC10 from the nebular H α luminosity, which is comparable to the Small Magellanic Cloud. We also present a revised nebular oxygen abundance of log(O/H) + 12 = 8.40 ± 0.04, comparable to the LMC. It has previously been suggested that for IC10 to follow the WR subtype-metallicity dependance seen in other Local Group galaxies, a large WN population awaits discovery. Our search revealed three new WN stars, and six candidates awaiting confirmation, providing little evidence to support this claim. The new global WR star total of 29 stars is consistent with the Large Magellanic Cloud population when scaled to the reduced SFR of IC10. For spectroscopically confirmed WR stars, the WC/WN ratio is lowered to 1.0; however, including all potential candidates, and assuming those unconfirmed to be WN stars, would reduce the ratio to ∼0.7. We attribute the high WC/WN ratio to the high star formation surface density of IC10 relative to the Magellanic Clouds, which enhances the frequency of high-mass stars capable of producing WC stars.

  4. II Zw 40 - 30 Doradus on Steroids

    NASA Astrophysics Data System (ADS)

    Leitherer, Claus; Lee, Janice C.; Levesque, Emily M.

    2017-11-01

    We obtained HST COS G140L spectra of the enigmatic nearby blue compact dwarf galaxy II Zw 40. The galaxy hosts a nuclear super star cluster embedded in a radio-bright nebula, similar to those observed in the related blue compact dwarfs NGC 5253 and Henize 2-10. The ultraviolet spectrum of II Zw 40 is exceptional in terms of the strength of He II 1640, O III] 1666 and C III] 1909. We determined reddening, age, and the cluster mass from the ultraviolet data. The super nebula and the ionizing cluster exceed the ionizing luminosity and stellar mass of the local benchmark 30 Doradus by an order of magnitude. Comparison with stellar evolution models accounting for rotation reveals serious short-comings: these models do not account for the presence of Wolf-Rayet-like stars at young ages observed in II Zw 40. Photoionization modeling is used to probe the origin of the nebular lines and determine gas phase abundances. C/O is solar, in agreement with the result of the stellar-wind modeling.

  5. The inclination of the dwarf irregular galaxy Holmberg II

    NASA Astrophysics Data System (ADS)

    Sánchez-Salcedo, F. J.; Hidalgo-Gámez, A. M.; Martínez-García, E. E.

    2014-10-01

    We provide constraints on the inclination angle of the H I disk of the dwarf irregular galaxy Holmberg II (Ho II) from a stability analysis of the outer gaseous disk. We point out that a mean inclination angle of 27(°) and thus a flat circular velocity of ≈ 60 km s(-1) , is required to have a level of gravitational stability similar to that found in other galaxies. Adopting this inclination angle, we find that Ho II lies on the right location in the baryonic Tully-Fisher relation. Moreover, for this inclination, its rotation curve is consistent with MOND. However, the corresponding analysis of the stability under MOND indicates that this galaxy could be problematic for MOND because its outer parts are marginally unstable in this gravity theory. We urge MOND simulators to study numerically the non-linear stability of gas-rich dwarf galaxies since this may provide a new key test for MOND.

  6. FR II radio galaxies in the Sloan Digital Sky Survey: observational facts

    NASA Astrophysics Data System (ADS)

    Kozieł-Wierzbowska, D.; Stasińska, G.

    2011-08-01

    Starting from the Cambridge Catalogues of radio sources, we have created a sample of 401 Fanaroff-Riley type II (FR II) radio sources that have counterparts in the main galaxy sample of the seventh Data release of the Sloan Digital Sky Survey (SDSS) and analyse their radio and optical properties. We find that the luminosity in the Hα line - which we argue gives a better measure of the total emission-line flux than the widely used luminosity in [O III]- is strongly correlated with the radio luminosity P1.4 GHz. We show that the absence of emission lines in about one third of our sample is likely due to a detection threshold and not to a lack of optical activity. We also find a very strong correlation between the values of LHα and P1.4 GHz when scaled by ‘MBH’, an estimate of the black hole mass. We find that the properties of FR II galaxies are mainly driven by the Eddington parameter LHα/‘MBH’ or, equivalently, P1.4 GHz/‘MBH’. Radio galaxies with hotspots are found among the ones with the highest values of P1.4 GHz/‘MBH’. Compared to classical active galactic nuclei (AGN) hosts in the main galaxy sample of the SDSS, our FR II galaxies show a larger proportion of objects with very hard ionizing radiation field and large ionization parameter. A few objects are, on the contrary, ionized by a softer radiation field. Two of them have double-peaked emission lines and deserve more attention. We find that the black hole masses and stellar masses in FR II galaxies are very closely related: ‘MBH’∝M1.13* with very little scatter. A comparison sample of line-less galaxies in the SDSS follows exactly the same relation, although the masses are, on average, smaller. This suggests that the FR II radio phenomenon occurs in normal elliptical galaxies, preferentially in the most massive ones. Although most FR II galaxies are old, some contain traces of young stellar populations. Such young populations are not seen in normal line-less galaxies, suggesting that

  7. COS Views of Local Galaxies Approaching Primeval Conditions

    NASA Astrophysics Data System (ADS)

    Wofford, Aida

    2014-10-01

    We will use COS G160M+G185M to observe the cosmollogically important lines C IV 1548+1551 A, He II 1640 A, O III] 1661+1666 A, and C III] 1907+1909 A in the three closest most metal-poor blue compact dwarf galaxies known. These galaxies approach primeval insterstellar and stellar conditions. One of the galaxies has no existing spectroscopic coverage in the UV. Available spectroscopy of the most metal-poor galaxies in the local universe are scarce, inhomogeneous, mostly low spectral-resolution, and are either noisy in main UV lines or lack their coverage. The proposed spectral resolution of about 20 km/s represents an order of magnitude improvement over existing HST data and allows us to disentangle stellar, nebular, and/or shock components to the lines. The high-quality constraints obtained in the framework of this proposal will make it possible to assess the relative likelihood of new spectral models of star-forming galaxies from different groups, in the best possible way achievable with current instrumentation. This will ensure that the best possible studies of early chemical enrichment of the universe can be achieved. The proposed observations are necessary to minimize large existing systematic uncertainties in the determination of high-redshift galaxy properties that JWST was in large part designed to measure.

  8. The MOSDEF Survey: First Measurement of Nebular Oxygen Abundance at z > 4

    NASA Astrophysics Data System (ADS)

    Shapley, Alice E.; Sanders, Ryan L.; Reddy, Naveen A.; Kriek, Mariska; Freeman, William R.; Mobasher, Bahram; Siana, Brian; Coil, Alison L.; Leung, Gene C. K.; deGroot, Laura; Shivaei, Irene; Price, Sedona H.; Azadi, Mojegan; Aird, James

    2017-09-01

    We present the first spectroscopic measurement of multiple rest-frame optical emission lines at z > 4. During the MOSFIRE Deep Evolution Field survey, we observed the galaxy GOODSN-17940 with the Keck I/MOSFIRE spectrograph. The K-band spectrum of GOODSN-17940 includes significant detections of the [O II]λλ3726,3729, [Ne III]λ3869, and Hγ emission lines and a tentative detection of Hδ, indicating z spec = 4.4121. GOODSN-17940 is an actively star-forming z > 4 galaxy based on its K-band spectrum and broadband spectral energy distribution. A significant excess relative to the surrounding continuum is present in the Spitzer/IRAC channel 1 photometry of GOODSN-17940, due primarily to strong Hα emission with a rest-frame equivalent width of EW(Hα) = 1200 Å. Based on the assumption of 0.5 Z ⊙ models and the Calzetti attenuation curve, GOODSN-17940 is characterized by {M}* ={5.0}-0.2+4.3× {10}9 {M}⊙ . The Balmer decrement inferred from Hα/Hγ is used to dust correct the Hα emission, yielding {{SFR(H}}α )={320}-140+190 {M}⊙ {{{yr}}}-1. These M * and star formation rate (SFR) values place GOODSN-17940 an order of magnitude in SFR above the z ˜ 4 star-forming “main sequence.” Finally, we use the observed ratio of [Ne III]/[O II] to estimate the nebular oxygen abundance in GOODSN-17940, finding O/H ˜ 0.2 (O/H)⊙. Combining our new [Ne III]/[O II] measurement with those from stacked spectra at z ˜ 0, 2, and 3, we show that GOODSN-17940 represents an extension to z > 4 of the evolution toward higher [Ne III]/[O II] (I.e., lower O/H) at fixed stellar mass. It will be possible to perform the measurements presented here out to z ˜ 10 using the James Webb Space Telescope. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of

  9. PopIII-star siblings in IZw18 and metal-poor WR galaxies unveiled from integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    Kehrig, C.; Vílchez, J. M.; Pérez-Montero, E.; Iglesias-Páramo, J.; Brinchmann, J.; Crowther, P. A.; Durret, F.; Kunth, D.

    Here, we highlight our recent results from the IFS study of Mrk178, the closest metal-poor WR galaxy, and of IZw18, the most metal-poor star-forming galaxy known in the local Universe. The IFS data of Mrk178 show the importance of aperture effects on the search for WR features, and the extent to which physical variations in the ISM properties can be detected. Our IFS data of IZw18 reveal its entire nebular HeIIλ4686-emitting region, and indicate for the very first time that peculiar, hot (nearly) metal-free ionizing stars (called here PopIII-star siblings) might hold the key to the HeII-ionization in IZw18.

  10. Star Formation in low mass galaxies

    NASA Astrophysics Data System (ADS)

    Mehta, Vihang

    2018-01-01

    Our current hierarchical view of the universe asserts that the large galaxies we see today grew via mergers of numerous smaller galaxies. As evidenced by recent literature, the collective impact of these low mass galaxies on the universe is more substantial than previously thought. Studying the growth and evolution of these low mass galaxies is critical to our understanding of the universe as a whole. Star formation is one of the most important ongoing processes in galaxies. Forming stars is fundamental to the growth of a galaxy. One of the main goals of my thesis is to analyze the star formation in these low mass galaxies at different redshifts.Using the Hubble UltraViolet Ultra Deep Field (UVUDF), I investigate the star formation in galaxies at the peak of the cosmic star formation history using the ultraviolet (UV) light as a star formation indicator. Particularly, I measure the UV luminosity function (LF) to probe the volume-averaged star formation properties of galaxies at these redshifts. The depth of the UVUDF is ideal for a direct measurement of the faint end slope of the UV LF. This redshift range also provides a unique opportunity to directly compare UV to the "gold standard" of star formation indicators, namely the Hα nebular emission line. A joint analysis of the UV and Hα LFs suggests that, on average, the star formation histories in low mass galaxies (~109 M⊙) are more bursty compared to their higher mass counterparts at these redshifts.Complementary to the analysis of the average star formation properties of the bulk galaxy population, I investigate the details of star formation in some very bursty galaxies at lower redshifts selected from Spitzer Large Area Survey with Hyper-Suprime Cam (SPLASH). Using a broadband color-excess selection technique, I identify a sample of low redshift galaxies with bright nebular emission lines in the Subaru-XMM Deep Field (SXDF) from the SPLASH-SXDF catalog. These galaxies are highly star forming and have

  11. Integral field spectroscopy of a sample of nearby galaxies. II. Properties of the H ii regions

    NASA Astrophysics Data System (ADS)

    Sánchez, S. F.; Rosales-Ortega, F. F.; Marino, R. A.; Iglesias-Páramo, J.; Vílchez, J. M.; Kennicutt, R. C.; Díaz, A. I.; Mast, D.; Monreal-Ibero, A.; García-Benito, R.; Bland-Hawthorn, J.; Pérez, E.; González Delgado, R.; Husemann, B.; López-Sánchez, Á. R.; Cid Fernandes, R.; Kehrig, C.; Walcher, C. J.; Gil de Paz, A.; Ellis, S.

    2012-10-01

    We analyse the spectroscopic properties of thousands of H ii regions identified in 38 face-on spiral galaxies. All galaxies were observed out to 2.4 effective radii using integral field spectroscopy (IFS) over the wavelength range ~3700 to ~6900 Å. The near uniform sample has been assembled from the PPAK IFS Nearby Galaxy (PINGS) survey and a sample described in Paper I. We develop a new automatic procedure to detect H ii regions, based on the contrast of the Hα intensity maps extracted from the datacubes. Once detected, the algorithm provides us with the integrated spectra of each individual segmented region. In total, we derive good quality spectroscopic information for ~2600 independent H ii regions/complexes. This is by far the largest H ii region survey of its kind. Our selection criteria and the use of 3D spectroscopy guarantee that we cover the regions in an unbiased way. A well-tested automatic decoupling procedure has been applied to remove the underlying stellar population, deriving the main properties (intensity, dispersion and velocity) of the strongest emission lines in the considered wavelength range (covering from [O ii] λ3727 to [S ii] λ6731). A final catalogue of the spectroscopic properties of H ii regions has been created for each galaxy, which includes information on morphology, spiral structure, gaskinematics, and surface brightness of the underlying stellar population. In the current study, we focus on the understanding of the average properties of the H ii regions and their radial distributions. We find a significant change in the ionisation characteristics of H ii regions within r < 0.25 re due to contamination from sources with different ionising characteristics, as we discuss. We find that the gas-phase oxygen abundance and the Hα equivalent width present a negative and positive gradient, respectively. The distribution of slopes is statistically compatible with a random Gaussian distribution around the mean value, if the radial

  12. Metallicities of Galaxies in the Local Universe

    NASA Astrophysics Data System (ADS)

    Hirschauer, Alec Seth

    2018-01-01

    The degree of heavy-element enrichment for star-forming galaxies in the universe is a fundamental astrophysical characteristic which traces the amount of stellar nucleosynthesis undertaken by the constituent population of stars. Estimating this quantity via the so-called "direct-method" is observationally challenging and requires measurement of intrinsically weak temperature-sensitive nebular emission lines, however these are typically not found for galaxies unless their emission lines are exceptionally bright. Metal abundances ("metallicities") must then therefore be estimated by empirical means utilizing ratios of strong emission lines, calibrated to sources of known abundance and/or theoretical models, which are measurable in essentially any nebular spectrum of a star-forming system. Relationships concerning metallicities in galaxies such as the luminosity-metallicity and mass-metallicity are critically dependent upon reliable estimations of abundances. Therefore, having a reliable observational constraint is paramount to developing models which accurately reflect the universe. This dissertation presentation explores metallicities for galaxies in the local universe through a variety of means. First, an attempt is made to improve calibrations of empirical relationships for estimating abundances for star-forming galaxies at high-metallicities, finding some intrinsic shortcomings but also revealing some interesting new findings regarding the computation of the electron gas of star-forming systems, as well as detecting some anomalously under-abundant, overly-luminous galaxies. Second, the development of a self-consistent scale for estimating metallicities allows for the creation of luminosity-metallicity and mass-metallicity relations for a statistically representative sample of star-forming galaxies in the local universe. Finally, a discovery is made of an extremely metal-poor star-forming galaxy, which opens the possibility to find more similar systems and to

  13. On the Nature of Ultra-faint Dwarf Galaxy Candidates. II. The Case of Cetus II

    NASA Astrophysics Data System (ADS)

    Conn, Blair C.; Jerjen, Helmut; Kim, Dongwon; Schirmer, Mischa

    2018-04-01

    We obtained deep Gemini GMOS-S g, r photometry of the ultra-faint dwarf galaxy candidate Cetus II with the aim of providing stronger constraints on its size, luminosity, and stellar population. Cetus II is an important object in the size–luminosity plane, as it occupies the transition zone between dwarf galaxies and star clusters. All known objects smaller than Cetus II (r h ∼ 20 pc) are reported to be star clusters, while most larger objects are likely dwarf galaxies. We found a prominent excess of main-sequence stars in the color–magnitude diagram of Cetus II, best described by a single stellar population with an age of 11.2 Gyr, metallicity of [Fe/H] = ‑1.28 dex, an [α/Fe] = 0.0 dex at a heliocentric distance of 26.3 ± 1.2 kpc. As well as being spatially located within the Sagittarius dwarf tidal stream, these properties are well matched to the Sagittarius galaxy’s Population B stars. Interestingly, like our recent findings on the ultra-faint dwarf galaxy candidate Tucana V, the stellar field in the direction of Cetus II shows no evidence of a concentrated overdensity despite tracing the main sequence for over six magnitudes. These results strongly support the picture that Cetus II is not an ultra-faint stellar system in the Milky Way halo, but made up of stars from the Sagittarius tidal stream.

  14. Host galaxy properties of calcium II and sodium I quasar absorption-line systems

    NASA Astrophysics Data System (ADS)

    Cherinka, Brian

    Many questions remain within the areas of galaxy formation and evolution. Understanding the origin of gas in galaxy environments, whether as tidal debris, infalling High Velocity Clouds, galaxy outflows, or as gaseous material residing in galaxy disks, is an important step in answering those questions. Quasar absorption-lines can often be used to probe the environments of intervening galaxies. Traditionally, quasar absorption-lines are studied independently of the host galaxy but this method denies us the exploration of the connection between galaxy and environment. Instead, one can select pairs of known galaxies and quasars. This gives much more information regarding the host galaxy and allows us to better connect galaxy properties with associated absorbers. We use the seventh data release of the Sloan Digital Sky Survey to generate a sample of spectroscopic galaxy-quasar pairs. We cross-correlated a sample of 105,000 quasars and ˜800,000 galaxies to produce ˜98,000 galaxy-quasar pairs, with the quasar projected within 100 kpc of the galaxy. Adopting an automated line-finding algorithm and using the galaxy redshift as a prior, we search through all quasar spectra and identify Ca II and Na I absorption due to the intervening galaxy. This procedure produced 1745 Ca II absorbers and 4500 Na I absorbers detected at or above 2σ. Stacking analysis of a subset of absorbers at z > 0.01, with significances at or above 3σ, showed strong Ca II and Na I features around external galaxies. Using the same subset of absorbers at z > 0.01, we looked for correlations between absorber and galaxy properties and examined differences in galaxy properties between the absorbers and non-absorbers. We found no correlations with absorber strength or differences between many galaxy properties at the 3σ level. The lack of correlations and differences between absorbers and non-absorbers suggest a ubiquitous nature for Ca II and Na I around all types of galaxies, with the absorbers showing

  15. Far Outer Galaxy H II Regions

    NASA Technical Reports Server (NTRS)

    Rudolph, A. L.; deGues, E. J.; Brand, J.; Wouterloot, J. G. A.; Gross, Anthony R. (Technical Monitor)

    1994-01-01

    We have made a multifrequency (6, 3.6, and 2 cm), high-resolution (3"-6"), radio continuum survey of IRAS selected sources from the catalogue of Wouterloot & Brand (1989) to search for and study H II regions in the far outer Galaxy. We identified 31 sources in this catalog with well determined galactocentric distances, and with R approx.. greater than 15 kpc and L(sub FIR) approx.greater than 10(exp 4) solar luminosity, indicating the presence of high-mass star-formation. We have observed 11 of these sources with the Very Large Array (VLA). We observed the sources at 6 and 2 cm using "scaled arrays", making possible a direct and reliable comparison of the data at these two wavelengths for the determination of spectral indices. We detected a total of 12 radio sources, of which 10 have spectral indices consistent with optically-thin free-free emission from H II regions. Combined with previous VLA observations by other investigators, we have data on a total of 15 H II regions at galactocentric distances of 15 to 18.2kpc, among the most remote H II regions found in our Galaxy. The sizes of the H II regions range from approx. less than 0.10 to 2.3 pc. Using the measured fluxes and sizes, we determine the electron densities, emission measures, and excitation parameters of the H II regions, as well as the fluxes of Lyman continuum photons needed to keep the nebulae ionized. The sizes and electron densities are consistent with most of the sources detected in this survey being compact or ultracompact H II regions. Seven of the fifteen H II regions have sizes approx. less than 0.20 pc. Assuming simple pressure-driven expansion of the H II regions, these sizes indicate ages approx. less than 5 x 10(exp 4) yr, or only 1% of the lifetime of an O star, which implies an unlikely overabundance of O stars in the outer Galaxy. Thus, the large number of compact H II regions suggests that the time these regions spend in a compact phase must be much longer than their dynamical

  16. Stellar Absorption Line Analysis of Local Star-forming Galaxies: The Relation between Stellar Mass, Metallicity, Dust Attenuation, and Star Formation Rate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jabran Zahid, H.; Kudritzki, Rolf-Peter; Ho, I-Ting

    We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass–star formation rate and the stellar mass–gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass–stellar metallicity relationsmore » obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.« less

  17. The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rutkowski, Michael J.; Hayes, Matthew; Scarlata, Claudia

    Recent work suggests that strong emission line, star-forming galaxies (SFGs) may be significant Lyman continuum leakers. We combine archival Hubble Space Telescope broadband ultraviolet and optical imaging (F275W and F606W, respectively) with emission line catalogs derived from WFC3 IR G141 grism spectroscopy to search for escaping Lyman continuum (LyC) emission from homogeneously selected z ∼ 2.5 SFGs. We detect no escaping Lyman continuum from SFGs selected on [O ii] nebular emission ( N = 208) and, within a narrow redshift range, on [O iii]/[O ii]. We measure 1 σ upper limits to the LyC escape fraction relative to the non-ionizingmore » UV continuum from [O ii] emitters, f {sub esc} ≲ 5.6%, and strong [O iii]/[O ii] > 5 ELGs, f {sub esc} ≲ 14.0%. Our observations are not deep enough to detect f {sub esc} ∼ 10% typical of low-redshift Lyman continuum emitters. However, we find that this population represents a small fraction of the star-forming galaxy population at z ∼ 2. Thus, unless the number of extreme emission line galaxies grows substantially to z ≳ 6, such galaxies may be insufficient for reionization. Deeper survey data in the rest-frame ionizing UV will be necessary to determine whether strong line ratios could be useful for pre-selecting LyC leakers at high redshift.« less

  18. SILVERRUSH. III. Deep optical and near-infrared spectroscopy for Lyα and UV-nebular lines of bright Lyα emitters at z = 6-7

    NASA Astrophysics Data System (ADS)

    Shibuya, Takatoshi; Ouchi, Masami; Harikane, Yuichi; Rauch, Michael; Ono, Yoshiaki; Mukae, Shiro; Higuchi, Ryo; Kojima, Takashi; Yuma, Suraphong; Lee, Chien-Hsiu; Furusawa, Hisanori; Konno, Akira; Martin, Crystal L.; Shimasaku, Kazuhiro; Taniguchi, Yoshiaki; Kobayashi, Masakazu A. R.; Kajisawa, Masaru; Nagao, Tohru; Goto, Tomotsugu; Kashikawa, Nobunari; Komiyama, Yutaka; Kusakabe, Haruka; Momose, Rieko; Nakajima, Kimihiko; Tanaka, Masayuki; Wang, Shiang-Yu

    2018-01-01

    We present Lyα and UV-nebular emission line properties of bright Lyα emitters (LAEs) at z = 6-7 with a luminosity of log LLyα/[erg s-1] = 43-44 identified in the 21 deg2 area of the SILVERRUSH early sample developed with the Subaru Hyper Suprime-Cam survey data. Our optical spectroscopy newly confirms 21 bright LAEs with clear Lyα emission, and contributes to making a spectroscopic sample of 96 LAEs at z = 6-7 in SILVERRUSH. From the spectroscopic sample, we select seven remarkable LAEs as bright as Himiko and CR7 objects, and perform deep Keck/MOSFIRE and Subaru/nuMOIRCS near-infrared spectroscopy reaching the 3 σ flux limit of ˜2 × 10-18 erg s-1 for the UV-nebular emission lines of He II λ1640, C IV λλ1548,1550, and O III]λλ1661,1666. Except for one tentative detection of C IV, we find no strong UV-nebular lines down to the flux limit, placing the upper limits of the rest-frame equivalent widths (EW0) of ˜2-4 Å for C IV, He II, and O III] lines. We also investigate the VLT/X-SHOOTER spectrum of CR7 whose 6 σ detection of He II is claimed by Sobral et al. Although two individuals and the ESO archive service carefully reanalyzed the X-SHOOTER data that are used in the study of Sobral et al., no He II signal of CR7 is detected, supportive of weak UV-nebular lines of the bright LAEs even for CR7. The spectral properties of these bright LAEs are thus clearly different from those of faint dropouts at z ˜ 7 that have strong UV-nebular lines shown in the various studies. Comparing these bright LAEs and the faint dropouts, we find anti-correlations between the UV-nebular line EW0 and the UV-continuum luminosity, which are similar to those found at z ˜ 2-3.

  19. ALMA Reveals Weak [N II] Emission in "Typical" Galaxies and Intense Starbursts at z = 5-6

    NASA Astrophysics Data System (ADS)

    Pavesi, Riccardo; Riechers, Dominik A.; Capak, Peter L.; Carilli, Christopher L.; Sharon, Chelsea E.; Stacey, Gordon J.; Karim, Alexander; Scoville, Nicholas Z.; Smolčić, Vernesa

    2016-12-01

    We report interferometric measurements of [N II] 205 μm fine-structure line emission from a representative sample of three galaxies at z = 5-6 using the Atacama Large (sub)Millimeter Array (ALMA). These galaxies were previously detected in [C II] and far-infrared continuum emission and span almost two orders of magnitude in star formation rate (SFR). Our results show at least two different regimes of ionized interstellar medium properties for galaxies in the first billion years of cosmic time, separated by their {L}[{{C}{{II}}]}/{L}[{{N}{{II}}]} ratio. We find extremely low [N II] emission compared to [C II] ({L}[{{C}{{II}}]}/{L}[{{N}{{II}}]}={68}-28+200) from a “typical” ˜ {L}{UV}* star-forming galaxy, likely directly or indirectly (by its effect on the radiation field) related to low dust abundance and low metallicity. The infrared-luminous modestly star-forming Lyman-break galaxy (LBG) in our sample is characterized by an ionized-gas fraction ({L}[{{C}{{II}}]}/{L}[{{N}{{II}}]}≲ 20) typical of local star-forming galaxies and shows evidence for spatial variations in its ionized-gas fraction across an extended gas reservoir. The extreme SFR, warm and compact dusty starburst AzTEC-3 shows an ionized fraction higher than expected given its SFR surface density ({L}[{{C}{{II}}]}/{L}[{{N}{{II}}]}=22+/- 8) suggesting that [N II] dominantly traces a diffuse ionized medium rather than star-forming H II regions in this type of galaxy. This highest redshift sample of [N II] detections provides some of the first constraints on ionized and neutral gas modeling attempts and on the structure of the interstellar medium at z = 5-6 in “normal” galaxies and starbursts.

  20. Starburst in the Interacting HII Galaxy II Zw 40 and in Non-Interacting HII Galaxies

    NASA Astrophysics Data System (ADS)

    Telles, E.

    2010-06-01

    In this poster, I summarize the results of our integral field spectroscopic observations of the nearby prototype of HII galaxies, II Zw 40. Observations with GMOS-IFU on GEMINI-North in the optical allowed us to make a detailed kinematic picture of the central starburst, while SINFONI with adaptive optics on the ESO-VLT gave us a near-IR view of the interplay between the ISM phases. Here, I also address the question that not all starbursts require an external trigger such as a galaxy-galaxy encounter, as it seems to be the case for a fraction of low luminosity HII galaxies. We speculate that these may form stars spontaneously like "popcorn in a pan".

  1. Detecting Galaxy Formation with He II Cooling Radiation

    NASA Astrophysics Data System (ADS)

    Yang, Yujin; Zabludoff, Ann; Davé, Romeel; Eisenstein, Daniel

    2006-08-01

    Galaxies obtain material to form their stars from the intergalactic medium, but direct observations of such accretion do not yet exist. Motivated by our theoretical work, we propose the first direct search for gravitational cooling radiation arising from the infall of gas into forming galaxies at z=3. While ``Lyα blobs'' are the best candidates for gas-accreting galaxies at high redshift, and are therefore the focus of our proposed study, their nature remains unknown due to intrinsic difficulties in interpreting their Lyα emission. Here, we propose to survey 10 of the Lyα blobs from the Matsuda et al. sample for He II. Compared to Lyα, Heha is optically thin, less sensitive to the UV background, and less contaminated by the recombination lines from star-forming galaxies, making it an ideal diagnostic line to uncover the processes by which galaxies acquire their baryons. This proposal is a resubmission in which we have explicitly addressed the concerns raised by the TAC last year. This project represents a new approach, which has the potential to revolutionize studies of galaxy formation.

  2. The remnant of a merger between two dwarf galaxies in Andromeda II.

    PubMed

    Amorisco, N C; Evans, N W; van de Ven, G

    2014-03-20

    Driven by gravity, massive structures like galaxies and clusters of galaxies are believed to grow continuously through hierarchical merging and accretion of smaller systems. Observational evidence of accretion events is provided by the coherent stellar streams crossing the outer haloes of massive galaxies, such as the Milky Way or Andromeda. At similar mass scales, around 10(11) solar masses in stars, further evidence of merging activity is also ample. Mergers of lower-mass galaxies are expected within the hierarchical process of galaxy formation, but have hitherto not been seen for galaxies with less than about 10(9) solar masses in stars. Here we report the kinematic detection of a stellar stream in one of the satellite galaxies of Andromeda, the dwarf spheroidal Andromeda II, which has a mass of only 10(7) solar masses in stars. The properties of the stream show that we are observing the remnant of a merger between two dwarf galaxies. This had a drastic influence on the dynamics of the remnant, which is now rotating around its projected major axis. The stellar stream in Andromeda II illustrates the scale-free character of the formation of galaxies, down to the lowest galactic mass scales.

  3. COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r -PROCESS GALAXY RETICULUM II

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ji, Alexander P.; Frebel, Anna; Chiti, Anirudh

    We present chemical abundances derived from high-resolution Magellan /Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven of the nine stars have extremely high levels of r -process material ([Eu/Fe] ∼ 1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H] < −3), and they have neutron-capture elementmore » abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r -process halo stars, but they are ∼0.5 dex lower than the solar r -process pattern. If the universal r -process pattern extends to those elements, the stars in Ret II display the least contaminated known r -process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r -process sites besides the source of r -process elements in Ret II. Galaxies like Ret II may be the original birth sites of r -process enhanced stars now found in the halo.« less

  4. Papanicolaou's nebular cells are related to HPV infection and HSIL.

    PubMed

    Roeters, Anne M E; Boon, Mathilde E; van Haaften, Maarten; Vernooij, Floor; Bontekoe, Tj Romke; Heintz, A Peter M

    2012-03-01

    Metaplastic cells with nebular cytoplasmic changes in the cervical smear are classified in the Dutch coding system for cervical screening as KOPAC O8 cells. Since these nebulated cells are already documented by Papanicolaou, we refer to these cells as Papanicolaou's nebular cells. We examined the simultaneous presence of these characteristic metaplastic cells and high-grade squamous intraepithelial lesion (HSIL) in a population-based data base from January 1991 and December 1996. The odds ratio (OR) of nebular cells concurring with HSIL increases with age. For the age cohort 30 years, the OR was 7.8 with a 95% confidence interval (CI) of 4.4-13.9. For the age cohort 60 years, the OR was 35.3 with a 95% CI of 7.8-159.2. Aiming to determine the nature of these nebular metaplastic cells, we performed Chlamydia and HPV PCR on 587 and 1,483 smears, respectively. With an OR of 0.9 [0.3-2.4] it is unlikely that Chlamydia plays a role in the appearance of these nebular cells in the smear. This study shows that with an OR of 5.9 [1.7-21.3] HPV is not only related to large koilocytosis but also to a nebular change of small metaplastic cells. This study reports that nebular changes of small metaplastic cells are related to cervical cancer and to HPV infection. Copyright © 2010 Wiley Periodicals, Inc.

  5. Outflows in low-mass galaxies at z >1

    NASA Astrophysics Data System (ADS)

    Maseda, Michael V.; MUSE GTO Consortium

    2017-03-01

    Star formation histories of local dwarf galaxies, derived through resolved stellar populations, appear complex and varied. The general picture derived from hydrodynamical simulations is one of cold gas accretion and bursty star formation, followed by feedback from supernovae and winds that heat and eject the central gas reservoirs. This ejection halts star formation until the material cools and re-accretes, resulting in an episodic SFH, particularly at stellar masses below ~ 109 M⊙. Such feedback has often been cited as the driving force behind the observed slowly-rising rotation curves in local dwarfs, due to an under-density of dark matter compared to theoretical models, which is one of the primary challenges to LCDM cosmology. However, these events have not yet been directly observed at high-redshift. Recently, using HST imaging and grism spectroscopy, we have uncovered an abundant population of low-mass galaxies (M* < 109 M⊙) at z = 1 - 2 that are undergoing strong bursts of star formation, in agreement with the theoretical predictions. These Extreme Emission Line Galaxies, with high specific SFRs and shallow gravitational potential wells, are ideal places to test the theoretical prediction of strong feedback-driven outflows. Here we use deep MUSE spectroscopy to search these galaxies for signatures of outflowing material, namely kinematic offsets between absorption lines (in the restframe optical and UV), which trace cool gas, and the nebular emission lines, which define the systemic redshift of the galaxy. Although the EELGs are intrinsically very faint, stacked spectra reveal blueshifted velocity centroids for Fe II absorption, which is indicative of outflowing cold gas. This represents the first constraint on outflows in M* < 109 M⊙ galaxies at z = 1 - 2. These outflows should regulate the star formation histories of low-mass galaxies at early cosmic times and thus play a crucial role in galaxy growth and evolution.

  6. HERSCHEL EXTREME LENSING LINE OBSERVATIONS: [C ii] VARIATIONS IN GALAXIES AT REDSHIFTS z = 1–3

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Malhotra, Sangeeta; Rhoads, James E.; Yang, Huan

    We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3 σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel . The [C ii] luminosity in this sample ranges from 8 × 10{sup 7} L {sub ⊙} to 3.7 × 10{sup 9} L {sub ⊙} (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to themore » total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.« less

  7. The Origins of [C ii] Emission in Local Star-forming Galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Croxall, K. V.; Smith, J. D.; Pellegrini, E.

    The [C ii] 158 μ m fine-structure line is the brightest emission line observed in local star-forming galaxies. As a major coolant of the gas-phase interstellar medium, [C ii] balances the heating, including that due to far-ultraviolet photons, which heat the gas via the photoelectric effect. However, the origin of [C ii] emission remains unclear because C{sup +} can be found in multiple phases of the interstellar medium. Here we measure the fractions of [C ii] emission originating in the ionized and neutral gas phases of a sample of nearby galaxies. We use the [N ii] 205 μ m fine-structuremore » line to trace the ionized medium, thereby eliminating the strong density dependence that exists in the ratio of [C ii]/[N ii] 122 μ m. Using the FIR [C ii] and [N ii] emission detected by the KINGFISH (Key Insights on Nearby Galaxies: a Far- Infrared Survey with Herschel ) and Beyond the Peak Herschel programs, we show that 60%–80% of [C ii] emission originates from neutral gas. We find that the fraction of [C ii] originating in the neutral medium has a weak dependence on dust temperature and the surface density of star formation, and has a stronger dependence on the gas-phase metallicity. In metal-rich environments, the relatively cooler ionized gas makes substantially larger contributions to total [C ii] emission than at low abundance, contrary to prior expectations. Approximate calibrations of this metallicity trend are provided.« less

  8. THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jaskot, A. E.; Oey, M. S.

    2013-04-01

    Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with themore » highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.« less

  9. Insights to Galaxy Evolution Utilizing a Multivariate Comparison of Circumgalactic OVI and MgII

    NASA Astrophysics Data System (ADS)

    Lewis, James; Churchill, Christopher; Nielsen, Nikole; Kacprzak, Glenn; Muzahid, Sowgat; Charlton, Jane

    2018-01-01

    We present a promising multivariate method to categorize inter-related astronomical data in meaningful ways. We use data from the MAGIICAT and "Multiphase Galaxy Halos" surveys and limit our sample to those galaxies which are imaged with the Hubble Space Telescope and for which the Circumgalactic Medium (CGM) is measured using high-resolution quasar spectra (HIRES/COS). Utilizing the method to categorize data about the CGM and its host galaxy yields distinct categories of CGM-galaxy pairs that imply a common fate for the outflows of MgII and OVI in redder galaxies. The analysis reveals a lack of circumgalactic OVI in lower mass, bluer (younger) galaxies, and that as the blue galaxies gain mass and age along the green valley strong OVI appears in the CGM predominately along the minor axes. But as the galaxies continue to gain mass and age into the red sequence strong OVI gas is found primarily along the major axes. Furthermore, we find a population of low mass red galaxies in which only weak, uniform, circumgalactic OVI is found. Incorporating our multivariate results for circumgalactic MgII, including evidence for quenching of star formation via weak circumgalactic MgII preferentially found along the minor axes of redder galaxies, and invoking the similarity of OVI column densities and kinematic spreads along the major and minor axes, we infer that OVI is ancient gas in the CGM.

  10. Galaxy properties in clusters. II. Backsplash galaxies

    NASA Astrophysics Data System (ADS)

    Muriel, H.; Coenda, V.

    2014-04-01

    Aims: We explore the properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies. Methods: We analyse the properties of more than 1000 galaxies brighter than M0.1r = - 19.6 on the outskirts of 90 clusters (1 < r/rvir < 2) in the redshift range 0.05 < z < 0.10. Using the line of sight velocity of galaxies relative to the cluster's mean, we selected low and high velocity subsamples. Theoretical predictions indicate that a significant fraction of the first subsample should be backsplash galaxies, that is, objects that have already orbited near the cluster centre. A significant proportion of the sample of high relative velocity (HV) galaxies seems to be composed of infalling objects. Results: Our results suggest that, at fixed stellar mass, late-type galaxies in the low-velocity (LV) sample are systematically older, redder, and have formed fewer stars during the last 3 Gyrs than galaxies in the HV sample. This result is consistent with models that assume that the central regions of clusters are effective in quenching the star formation by means of processes such as ram pressure stripping or strangulation. At fixed stellar mass, LV galaxies show some evidence of having higher surface brightness and smaller size than HV galaxies. These results are consistent with the scenario where galaxies that have orbited the central regions of clusters are more likely to suffer tidal effects, producing loss of mass as well as a re-distribution of matter towards more compact configurations. Finally, we found a higher fraction of ET galaxies in the LV sample, supporting the idea that the central region of clusters of galaxies may contribute to the transformation of morphological types towards earlier types.

  11. Photometry of resolved galaxies. IV - Holmberg I and Holmberg II

    NASA Technical Reports Server (NTRS)

    Hoessel, J. G.; Danielson, G. E.

    1984-01-01

    Colors and magnitudes are presented for 279 resolved stars in the Holmberg I dwarf galaxy and 468 resolved stars in Holmberg II. Both systems are Magellanic type dwarf members of the M81-NGC 2403 Group, which lies at approximately 3 Mpc from the Local Group. The photometry was done in the GRI passbands using CCD detectors. Color-magnitude diagrams and luminosity functions are constructed; these are compared with results for several Local Group galaxies and with theoretical work. Holmberg I is found to have a low present star formation rate, while Holmberg II is very active at present.

  12. Stellar kinematics and metallicities in the ultra-faint dwarf galaxy Reticulum II

    DOE PAGES

    Simon, J. D.

    2015-07-23

    With this study, we present Magellan/M2FS, Very Large Telescope/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity ofmore » $$62.8\\pm 0.5\\;\\mathrm{km}\\;{\\rm{s}}^{-1}$$ and a velocity dispersion of $$3.3\\pm 0.7\\;\\mathrm{km}\\;{\\rm{s}}^{-1}$$. The mass-to-light ratio of Ret II within its half-light radius is $$470\\pm 210\\ {M}_{\\odot }/{L}_{\\odot }$$, demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 $$\\mathrm{km}\\ {{\\rm{s}}}^{-1}$$, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 ± 0.09 dex, and we identify several extremely metal-poor stars with $${\\rm{[Fe/H]}}\\lt -3$$. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of $${\\rm{[Fe/H]}}=-2.65\\pm 0.07$$, Ret II matches Segue 1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is $${\\mathrm{log}}_{10}(J)=18.8\\pm 0.6\\;\\;\\mathrm{GeV}{\\;}^{2}\\;{\\mathrm{cm}}^{-5}\\;$$ within 0fdg2, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies.« less

  13. Unusual broad-line Mg II emitters among luminous galaxies in the baryon oscillation spectroscopic survey

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roig, Benjamin; Blanton, Michael R.; Ross, Nicholas P.

    2014-02-01

    Many classes of active galactic nuclei (AGNs) have been observed and recorded since the discovery of Seyfert galaxies. In this paper, we examine the sample of luminous galaxies in the Baryon Oscillation Spectroscopic Survey. We find a potentially new observational class of AGNs, one with strong and broad Mg II λ2799 line emission, but very weak emission in other normal indicators of AGN activity, such as the broad-line Hα, Hβ, and the near-ultraviolet AGN continuum, leading to an extreme ratio of broad Hα/Mg II flux relative to normal quasars. Meanwhile, these objects' narrow-line flux ratios reveal AGN narrow-line regions withmore » levels of activity consistent with the Mg II fluxes and in agreement with that of normal quasars. These AGN may represent an extreme case of the Baldwin effect, with very low continuum and high equivalent width relative to typical quasars, but their ratio of broad Mg II to broad Balmer emission remains very unusual. They may also be representative of a class of AGN where the central engine is observed indirectly with scattered light. These galaxies represent a small fraction of the total population of luminous galaxies (≅ 0.1%), but are more likely (about 3.5 times) to have AGN-like nuclear line emission properties than other luminous galaxies. Because Mg II is usually inaccessible for the population of nearby galaxies, there may exist a related population of broad-line Mg II emitters in the local universe which is currently classified as narrow-line emitters (Seyfert 2 galaxies) or low ionization nuclear emission-line regions.« less

  14. Galaxy clustering dependence on the [O II] emission line luminosity in the local Universe

    NASA Astrophysics Data System (ADS)

    Favole, Ginevra; Rodríguez-Torres, Sergio A.; Comparat, Johan; Prada, Francisco; Guo, Hong; Klypin, Anatoly; Montero-Dorta, Antonio D.

    2017-11-01

    We study the galaxy clustering dependence on the [O II] emission line luminosity in the SDSS DR7 Main galaxy sample at mean redshift z ∼ 0.1. We select volume-limited samples of galaxies with different [O II] luminosity thresholds and measure their projected, monopole and quadrupole two-point correlation functions. We model these observations using the 1 h-1 Gpc MultiDark-Planck cosmological simulation and generate light cones with the SUrvey GenerAtoR algorithm. To interpret our results, we adopt a modified (Sub)Halo Abundance Matching scheme, accounting for the stellar mass incompleteness of the emission line galaxies. The satellite fraction constitutes an extra parameter in this model and allows to optimize the clustering fit on both small and intermediate scales (i.e. rp ≲ 30 h-1 Mpc), with no need of any velocity bias correction. We find that, in the local Universe, the [O II] luminosity correlates with all the clustering statistics explored and with the galaxy bias. This latter quantity correlates more strongly with the SDSS r-band magnitude than [O II] luminosity. In conclusion, we propose a straightforward method to produce reliable clustering models, entirely built on the simulation products, which provides robust predictions of the typical ELG host halo masses and satellite fraction values. The SDSS galaxy data, MultiDark mock catalogues and clustering results are made publicly available.

  15. Nebular chemistry and theories of lunar origin

    NASA Technical Reports Server (NTRS)

    Larimer, John W.

    1986-01-01

    The cosmic history of planetary matter is traced from nucleosynthesis through accretion in an attempt to understand the origin of the moon. It is noted that nebular processes must be considered in any theory of lunar origin and that planetary differentiation and volcanism determine the final character of lunar rocks. The moon's unique blend of nebular components suggests that the earth and moon accreted from the same mix of components as the proto-moon orbited the proto-earth, with the earth winning and the moon progressively losing, its solar complement of the components.

  16. Active galactic nuclei from He II: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Bär, Rudolf E.; Weigel, Anna K.; Sartori, Lia F.; Oh, Kyuseok; Koss, Michael; Schawinski, Kevin

    2017-04-01

    In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the He II λ4685 emission line diagnostic diagram by Shirazi & Brinchmann (2012) in addition to the standard methods based on other optical emission lines. The He II-based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 63 915 galaxies from the Sloan Digital Sky Survey Data Release 7 at 0.02 < z < 0.05 and use both the conventional BPT emission line diagnostic diagrams, as well as the He II diagram to identify AGN. In this sample, 1075 galaxies are selected as AGN using the BPT diagram, while additional 234 galaxies are identified as AGN using the He II diagnostic diagram, representing a 22 per cent increase of AGN in the parent galaxy sample. We explore the host galaxy properties of these new He II-selected AGN candidates and find that they are most common in star-forming galaxies on the blue cloud and on the main sequence where ionization from star formation is most likely to mask AGN emission in the BPT lines. We note in particular a high He II AGN fraction in galaxies above the high-mass end of the main sequence where quenching is expected to occur. We use archival Chandra observations to confirm the AGN nature of candidates selected through He II-based diagnostic. Finally, we discuss how this technique can help inform galaxy/black hole coevolution scenarios.

  17. Spectroscopic Confirmation of the Dwarf Galaxies Hydra II and Pisces II and the Globular Cluster Laevens 1

    NASA Astrophysics Data System (ADS)

    Kirby, Evan N.; Simon, Joshua D.; Cohen, Judith G.

    2015-09-01

    We present Keck/DEIMOS spectroscopy of stars in the recently discovered Milky Way satellites Hydra II, Pisces II, and Laevens 1. We measured a velocity dispersion of {5.4}-2.4+3.6 km s-1 for Pisces II, but we did not resolve the velocity dispersions of Hydra II or Laevens 1. We marginally resolved the metallicity dispersions of Hydra II and Pisces II but not Laevens 1. Furthermore, Hydra II and Pisces II obey the luminosity-metallicity relation for Milky Way dwarf galaxies (< [{Fe}/{{H}}]> =-2.02+/- 0.08 and -2.45+/- 0.07, respectively), whereas Laevens 1 does not (< [{Fe}/{{H}}]> =-1.68+/- 0.05). The kinematic and chemical properties suggest that Hydra II and Pisces II are dwarf galaxies, and Laevens 1 is a globular cluster. We determined that two of the previously observed blue stars near the center of Laevens 1 are not members of the cluster. A third blue star has ambiguous membership. Hydra II has a radial velocity < {v}{helio}> =303.1+/- 1.4 km s-1, similar to the leading arm of the Magellanic stream. The mass-to-light ratio for Pisces II is {370}-240+310 {M}⊙ /{L}⊙ . It is not among the most dark matter-dominated dwarf galaxies, but it is still worthy of inclusion in the search for gamma-rays from dark matter self-annihilation. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  18. Workshop on Parent-Body and Nebular Modification of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E. (Editor); Krot, A. N. (Editor); Scott, E. R. D. (Editor)

    1997-01-01

    Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

  19. The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MegaSaura). II. Stacked Spectra

    NASA Astrophysics Data System (ADS)

    Rigby, J. R.; Bayliss, M. B.; Chisholm, J.; Bordoloi, R.; Sharon, K.; Gladders, M. D.; Johnson, T.; Paterno-Mahler, R.; Wuyts, E.; Dahle, H.; Acharyya, A.

    2018-01-01

    We stack the rest-frame ultraviolet spectra of N = 14 highly magnified gravitationally lensed galaxies at redshifts 1.6< z< 3.6. The resulting new composite spans 900< {λ }{rest}< 3000 Å, with a peak signal-to-noise ratio (S/N) of 103 per spectral resolution element (∼100 km s‑1). It is the highest S/N, highest spectral resolution composite spectrum of z ∼ 2–3 galaxies yet published. The composite reveals numerous weak nebular emission lines and stellar photospheric absorption lines that can serve as new physical diagnostics, particularly at high redshift with the James Webb Space Telescope (JWST). We report equivalent widths to aid in proposing for and interpreting JWST spectra. We examine the velocity profiles of strong absorption features in the composite, and in a matched composite of z∼ 0 COS/HST galaxy spectra. We find remarkable similarity in the velocity profiles at z∼ 0 and z∼ 2, suggesting that similar physical processes control the outflows across cosmic time. While the maximum outflow velocity depends strongly on ionization potential, the absorption-weighted mean velocity does not. As such, the bulk of the high-ionization absorption traces the low-ionization gas, with an additional blueshifted absorption tail extending to at least ‑2000 km s‑1. We interpret this tail as arising from the stellar wind and photospheres of massive stars. Starburst99 models are able to replicate this high-velocity absorption tail. However, these theoretical models poorly reproduce several of the photospheric absorption features, indicating that improvements are needed to match observational constraints on the massive stellar content of star-forming galaxies at z∼ 2. We publicly release our composite spectra.

  20. Tidal disruption of dwarf spheroidal galaxies: the strange case of Crater II

    NASA Astrophysics Data System (ADS)

    Sanders, Jason L.; Evans, N. W.; Dehnen, W.

    2018-05-01

    Dwarf spheroidal galaxies of the Local Group obey a relationship between the line-of-sight velocity dispersion and half-light radius, although there are a number of dwarfs that lie beneath this relation with suppressed velocity dispersion. The most discrepant of these (in the Milky Way) is the `feeble giant' Crater II. Using analytic arguments supported by controlled numerical simulations of tidally-stripped flattened two-component dwarf galaxies, we investigate interpretations of Crater II within standard galaxy formation theory. Heavy tidal disruption is necessary to explain the velocity-dispersion suppression which is plausible if the proper motion of Crater II is (μα*, μδ) = ( - 0.21 ± 0.09, -0.24 ± 0.09)mas yr-1. Furthermore, we demonstrate that the velocity dispersion of tidally-disrupted systems is solely a function of the total mass loss even for weakly-embedded and flattened systems. The half-light radius evolution depends more sensitively on orbital phase and the properties of the dark matter profile. The half-light radius of weakly-embedded cusped systems rapidly decreases producing some tension with the Crater II observations. This tension is alleviated by cored dark matter profiles, in which the half-light radius can grow after tidal disruption. The evolution of flattened galaxies is characterised by two competing effects: tidal shocking makes the central regions rounder whilst tidal distortion produces a prolate tidally-locked outer envelope. After ˜70% of the central mass is lost, tidal distortion becomes the dominant effect and the shape of the central regions of the galaxy tends to a universal prolate shape irrespective of the initial shape.

  1. Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8

    NASA Astrophysics Data System (ADS)

    Smit, Renske; Bouwens, Rychard J.; Carniani, Stefano; Oesch, Pascal A.; Labbé, Ivo; Illingworth, Garth D.; van der Werf, Paul; Bradley, Larry D.; Gonzalez, Valentino; Hodge, Jacqueline A.; Holwerda, Benne W.; Maiolino, Roberto; Zheng, Wei

    2018-01-01

    The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this ‘epoch of reionization’ involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C II] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C II] luminosities than would be expected from local scaling relations, and searches for the [C II] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C II] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C II] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C II] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation

  2. Rotation in [C ii]-emitting gas in two galaxies at a redshift of 6.8.

    PubMed

    Smit, Renske; Bouwens, Rychard J; Carniani, Stefano; Oesch, Pascal A; Labbé, Ivo; Illingworth, Garth D; van der Werf, Paul; Bradley, Larry D; Gonzalez, Valentino; Hodge, Jacqueline A; Holwerda, Benne W; Maiolino, Roberto; Zheng, Wei

    2018-01-10

    The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this 'epoch of reionization' involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C ii] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C ii] luminosities than would be expected from local scaling relations, and searches for the [C ii] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C ii] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C ii] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C ii] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation-dominated disks

  3. A chemical confirmation of the faint Boötes II dwarf spheroidal galaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koch, Andreas; Rich, R. Michael, E-mail: akoch@lsw.uni-heidelberg.de

    2014-10-10

    We present a chemical abundance study of the brightest confirmed member star of the ultra-faint dwarf galaxy Boötes II from Keck/HIRES high-resolution spectroscopy at moderate signal-to-noise ratios. At [Fe/H] = –2.93 ± 0.03(stat.) ± 0.17(sys.), this star chemically resembles metal-poor halo field stars and the signatures of other faint dwarf spheroidal galaxies at the same metallicities in that it shows enhanced [α/Fe] ratios, Solar Fe-peak element abundances, and low upper limits on the neutron-capture element Ba. Moreover, this star shows no chemical peculiarities in any of the eight elements we were able to measure. This implies that the chemical outliersmore » found in other systems remain outliers pertaining to the unusual enrichment histories of the respective environments, while Boo II appears to have experienced an enrichment history typical of its very low mass. We also re-calibrated previous measurements of the galaxy's metallicity from the calcium triplet (CaT) and find a much lower value than reported before. The resulting broad metallicity spread, in excess of one dex, the very metal-poor mean, and the chemical abundance patterns of the present star imply that Boötes II is a low-mass, old, metal-poor dwarf galaxy and not an overdensity associated with the Sagittarius Stream as has been previously suggested based on its sky position and kinematics. The low, mean CaT metallicity of –2.7 dex falls right on the luminosity-metallicity relation delineated over four orders of magnitude from the more luminous to the faintest galaxies. Thus Boötes II's chemical enrichment appears representative of the galaxy's original mass, while tidal stripping and other mass loss mechanisms were probably not significant as for other low-mass satellites.« less

  4. A representative survey of the dynamics and energetics of FR II radio galaxies

    NASA Astrophysics Data System (ADS)

    Ineson, J.; Croston, J. H.; Hardcastle, M. J.; Mingo, B.

    2017-05-01

    We report the first large, systematic study of the dynamics and energetics of a representative sample of Fanaroff-Riley type II (FR II) radio galaxies with well-characterized group/cluster environments. We used X-ray inverse-Compton and radio synchrotron measurements to determine the internal radio-lobe conditions, and these were compared with external pressures acting on the lobes, determined from measurements of the thermal X-ray emission of the group/cluster. Consistent with previous work, we found that FR II radio lobes are typically electron dominated by a small factor relative to equipartition, and are overpressured relative to the external medium in their outer parts. These results suggest that there is typically no energetically significant proton population in the lobes of FR II radio galaxies (unlike for FR Is), and so for this population, inverse-Compton modelling provides an accurate way of measuring total energy content and estimating jet power. We estimated the distribution of Mach numbers for the population of expanding radio lobes, finding that at least half of the radio galaxies are currently driving strong shocks into their group/cluster environments. Finally, we determined a jet power-radio luminosity relation for FR II radio galaxies based on our estimates of lobe internal energy and Mach number. The slope and normalization of this relation are consistent with theoretical expectations, given the departure from equipartition and environmental distribution for our sample.

  5. A Spectroscopic Survey of Lensed Dwarf Galaxies at 1

    NASA Astrophysics Data System (ADS)

    Alavi, Anahita; Siana, Brian; gburek, Timothy; Richard, Johan; Teplitz, Harry; Rafelski, Marc; Stark, Daniel P.; Anahita Alavi

    2018-01-01

    High-redshift dwarf galaxies (M<109 M⊙) are one of the primary targets of the James Web Space Telescope. Recent studies have suggested that these galaxies are different than their bright counterparts, as they follow a divergent evolutionary history of star formation. In our previous study, utilizing the magnification from massive clusters of galaxies (Hubble Frontier Fields), we found a large sample of dwarf star-forming galaxies at the peak epoch of star formation (1galaxies, we have conducted a spectroscopic survey of these lensed faint galaxies using the Multi-Object Near-IR Spectrograph (MOSFIRE) at the Keck observatory. In this talk, I will present their nebular dust attenuation measurements using the ratio of Balmer lines (i.e., Balmer decrement) and compare with their stellar dust attenuation (i.e., from UV spectral slopes). I will also show that these faint galaxies follow a steep dust extinction curve (i.e., SMC like).

  6. The MUSE Hubble Ultra Deep Field Survey. VII. Fe II* emission in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Finley, Hayley; Bouché, Nicolas; Contini, Thierry; Paalvast, Mieke; Boogaard, Leindert; Maseda, Michael; Bacon, Roland; Blaizot, Jérémy; Brinchmann, Jarle; Epinat, Benoît; Feltre, Anna; Marino, Raffaella Anna; Muzahid, Sowgat; Richard, Johan; Schaye, Joop; Verhamme, Anne; Weilbacher, Peter M.; Wisotzki, Lutz

    2017-11-01

    Non-resonant Fe II* (λ2365, λ2396, λ2612, λ2626) emission can potentially trace galactic winds in emission and provide useful constraints to wind models. From the 3.15' × 3.15' mosaic of the Hubble Ultra Deep Field (UDF) obtained with the VLT/MUSE integral field spectrograph, we identify a statistical sample of 40 Fe II* emitters and 50 MgIII (λλ2796,2803) emitters from a sample of 271 [O II]λλ3726,3729 emitters with reliable redshifts from z = 0.85-1.50 down to 2 × 10-18 (3σ) ergs s-1 cm-2 (for [O II]), covering the M⋆ range from 108-1011 M⊙. The Fe II* and Mg II emitters follow the galaxy main sequence, but with a clear dichotomy. Galaxies with masses below 109 M⊙ and star formation rates (SFRs) of ≲ 1 M⊙ yr-1 have MgIII emission without accompanying Fe II* emission, whereas galaxies with masses above 1010 M⊙ and SFRs ≳ 10 M⊙ yr-1 have Fe II* emission without accompanying MgIII emission. Between these two regimes, galaxies have both MgIII and Fe II* emission, typically with MgIII P Cygni profiles. Indeed, the MgIII profile shows a progression along the main sequence from pure emission to P Cygni profiles to strong absorption, due to resonant trapping. Combining the deep MUSE data with HST ancillary information, we find that galaxies with pure MgIII emission profiles have lower SFR surface densities than those with either MgIII P Cygni profiles or Fe II* emission. These spectral signatures produced through continuum scattering and fluorescence, MgIII P Cygni profiles and Fe II* emission, are better candidates for tracing galactic outflows than pure MgIII emission, which may originate from HIII regions. We compare the absorption and emission rest-frame equivalent widths for pairs of FeIII transitions to predictions from outflow models and find that the observations consistently have less total re-emission than absorption, suggesting either dust extinction or non-isotropic outflow geometries.

  7. A two-point diagnostic for the H II galaxy Hubble diagram

    NASA Astrophysics Data System (ADS)

    Leaf, Kyle; Melia, Fulvio

    2018-03-01

    A previous analysis of starburst-dominated H II galaxies and H II regions has demonstrated a statistically significant preference for the Friedmann-Robertson-Walker cosmology with zero active mass, known as the Rh = ct universe, over Λcold dark matter (ΛCDM) and its related dark-matter parametrizations. In this paper, we employ a two-point diagnostic with these data to present a complementary statistical comparison of Rh = ct with Planck ΛCDM. Our two-point diagnostic compares, in a pairwise fashion, the difference between the distance modulus measured at two redshifts with that predicted by each cosmology. Our results support the conclusion drawn by a previous comparative analysis demonstrating that Rh = ct is statistically preferred over Planck ΛCDM. But we also find that the reported errors in the H II measurements may not be purely Gaussian, perhaps due to a partial contamination by non-Gaussian systematic effects. The use of H II galaxies and H II regions as standard candles may be improved even further with a better handling of the systematics in these sources.

  8. CHEMICAL DIVERSITY IN THE ULTRA-FAINT DWARF GALAXY TUCANA II

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ji, Alexander P.; Frebel, Anna; Ezzeddine, Rana

    We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II, based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicities of these stars range from [Fe/H] = −3.2 to −2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < −1). However, a number of anomalous chemical signatures are present. One star is relatively metal-rich ([Fe/H] = −2.6) and shows [Na, α , Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and SNe Ia. Two stars with [Fe/H] < −3 are mildly carbon-enhanced ([C/Fe] ∼more » 0.7) and may be consistent with enrichment by faint supernovae, if such supernovae can produce neutron-capture elements. A fourth star with [Fe/H] = −3 is carbon-normal, and exhibits distinct light element abundance ratios from the carbon-enhanced stars. This carbon-normal star implies that at least two distinct nucleosynthesis sources, both possibly associated with Population III stars, contributed to the early chemical enrichment of this galaxy. Despite its very low luminosity, Tucana II shows a diversity of chemical signatures that preclude it from being a simple “one-shot” first galaxy yet still provide a window into star and galaxy formation in the early universe.« less

  9. Chemical Abundances of New Member Stars in the Tucana II Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Chiti, Anirudh; Frebel, Anna; Ji, Alexander P.; Jerjen, Helmut; Kim, Dongwon; Norris, John E.

    2018-04-01

    We present chemical abundance measurements for seven stars with metallicities ranging from Fe/H] = ‑3.3 to [Fe/H] = ‑2.4 in the Tucana II ultra-faint dwarf galaxy (UFD), based on high-resolution spectra obtained with the MIKE spectrograph on the 6.5 m Magellan-Clay Telescope. For three stars, we present detailed chemical abundances for the first time. Of those, two stars are newly discovered members of Tucana II and were selected as probable members from deep narrowband photometry of the Tucana II UFD taken with the SkyMapper telescope. This result demonstrates the potential for photometrically identifying members of dwarf galaxy systems based on chemical composition. One new star was selected from the membership catalog of Walker et al. The other four stars in our sample have been reanalyzed, following additional observations. Overall, six stars have chemical abundances that are characteristic of the UFD stellar population. The seventh star shows chemical abundances that are discrepant from the other Tucana II members and an atypical, higher strontium abundance than what is expected for typical UFD stars. While unlikely, its strontium abundance raises the possibility that it may be a foreground metal-poor halo star with the same systemic velocity as Tucana II. If we were to exclude this star, Tucana II would satisfy the criteria to be a surviving first galaxy. Otherwise, this star implies that Tucana II has likely experienced somewhat extended chemical evolution. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  10. Galaxies at redshifts 5 to 6 with systematically low dust content and high [C II] emission

    NASA Astrophysics Data System (ADS)

    Capak, P. L.; Carilli, C.; Jones, G.; Casey, C. M.; Riechers, D.; Sheth, K.; Carollo, C. M.; Ilbert, O.; Karim, A.; Lefevre, O.; Lilly, S.; Scoville, N.; Smolcic, V.; Yan, L.

    2015-06-01

    The rest-frame ultraviolet properties of galaxies during the first three billion years of cosmic time (redshift z > 4) indicate a rapid evolution in the dust obscuration of such galaxies. This evolution implies a change in the average properties of the interstellar medium, but the measurements are systematically uncertain owing to untested assumptions and the inability to detect heavily obscured regions of the galaxies. Previous attempts to measure the interstellar medium directly in normal galaxies at these redshifts have failed for a number of reasons, with two notable exceptions. Here we report measurements of the forbidden C II emission (that is, [C II]) from gas, and the far-infrared emission from dust, in nine typical star-forming galaxies about one billion years after the Big Bang (z ~ 5-6). We find that these galaxies have thermal emission that is less than 1/12 that of similar systems about two billion years later, and enhanced [C II] emission relative to the far-infrared continuum, confirming a strong evolution in the properties of the interstellar medium in the early Universe. The gas is distributed over scales of one to eight kiloparsecs, and shows diverse dynamics within the sample. These results are consistent with early galaxies having significantly less dust than typical galaxies seen at z < 3 and being comparable in dust content to local low-metallicity systems.

  11. Galaxies at redshifts 5 to 6 with systematically low dust content and high [C II] emission.

    PubMed

    Capak, P L; Carilli, C; Jones, G; Casey, C M; Riechers, D; Sheth, K; Carollo, C M; Ilbert, O; Karim, A; LeFevre, O; Lilly, S; Scoville, N; Smolcic, V; Yan, L

    2015-06-25

    The rest-frame ultraviolet properties of galaxies during the first three billion years of cosmic time (redshift z > 4) indicate a rapid evolution in the dust obscuration of such galaxies. This evolution implies a change in the average properties of the interstellar medium, but the measurements are systematically uncertain owing to untested assumptions and the inability to detect heavily obscured regions of the galaxies. Previous attempts to measure the interstellar medium directly in normal galaxies at these redshifts have failed for a number of reasons, with two notable exceptions. Here we report measurements of the forbidden C ii emission (that is, [C II]) from gas, and the far-infrared emission from dust, in nine typical star-forming galaxies about one billion years after the Big Bang (z ≈ 5-6). We find that these galaxies have thermal emission that is less than 1/12 that of similar systems about two billion years later, and enhanced [C II] emission relative to the far-infrared continuum, confirming a strong evolution in the properties of the interstellar medium in the early Universe. The gas is distributed over scales of one to eight kiloparsecs, and shows diverse dynamics within the sample. These results are consistent with early galaxies having significantly less dust than typical galaxies seen at z < 3 and being comparable in dust content to local low-metallicity systems.

  12. The Taxonomy of Blue Amorphous Galaxies. II. Structure and Evolution

    NASA Astrophysics Data System (ADS)

    Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.

    1999-09-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution, and starbursts are believed to affect the structure and evolution of dwarf galaxies strongly. We have therefore embarked on a systematic study of 12 of the nearest dwarf galaxies thought to be undergoing bursts of star formation. These were selected primarily by their morphological type (blue ``amorphous'' galaxies). We show that these blue amorphous galaxies are not physically distinguishable from dwarfs selected as starbursting by other methods, such as blue compact dwarfs (BCDs) and H II galaxies. All these classes exhibit surface brightness profiles that are exponential in the outer regions (r>~1.5re) but often have a predominantly central blue excess, suggesting a young burst in an older, redder galaxy. Typically, the starbursting ``cores'' are young (~107-108 yr) events compared to the older (~109-1010 yr) underlying galaxy (the ``envelope''). The ratio of the core to envelope in blue light ranges from essentially zero to about 2. These starbursts are therefore modest events involving only a few percent of the stellar mass. The envelopes have surface brightnesses that are much higher than typical dwarf irregular (dI) galaxies, so it is unlikely that there is a straightforward evolutionary relation between typical dIs and dwarf starburst galaxies. Instead we suggest that amorphous galaxies may repeatedly cycle through starburst and quiescent phases, corresponding to the galaxies with strong and weak/absent cores, respectively. Once amorphous galaxies use up the available gas (either through star formation or galactic winds) so that star formation is shut off, the faded remnants would strongly resemble dwarf elliptical galaxies. However, in the current cosmological epoch, this is evidently a slow process that is the aftermath of a series of many weak, recurring bursts. Present-day dE's must have experienced more rapid and intense evolution than this in the distant past.

  13. Exploring the Dust Content, Metallicity, Star Formation and AGN Activity in Distant Dusty, Star-Forming Galaxies Using Cosmic Telescope

    NASA Astrophysics Data System (ADS)

    Walth, Gregory; Egami, Eiichi; Clément, Benjamin; Rujopakarn, Wiphu; Rawle, Tim; Richard, Johan; Dessauges, Miroslava; Perez-Gonzalez, Pablo; Ebeling, Harald; Vayner, Andrey; Wright, Shelley; Cosens, Maren; Herschel Lensing Survey

    2018-01-01

    We present our recent ALMA observations of Herschel-detected gravitationally lensed dusty, star-forming galaxies (DSFGs) and how they compliment our near-infrared spectroscopic observations of their rest-frame optical nebular emission. This provides the complete picture of star formation; from the molecular gas that fuels star formation, to the dust emission which are the sites of star formation, and the nebular emission which is the gas excited by the young stars. DSFGs undergo the largest starbursts in the Universe, contributing to the bulk of the cosmic star formation rate density between redshifts z = 1 - 4. Internal processes within high-redshift DSFGs remains largely unexplored; such as feedback from star formation, the role of turbulence, gas surface density of molecular gas, AGN activity, and the rates of metal production. Much that is known about DSFGs star formation properties comes from their CO and dust emission. In order to fully understand the star formation history of DSFGs, it is necessary to observe their optical nebular emission. Unfortunately, UV/optical emission is severely attenuated by dust, making it challenging to detect. With the Herschel Lensing Survey, a survey of the cores of almost 600 massive galaxy clusters, we are able to probe faint dust-attenuated nebular emission. We are currently conducting a new survey using Keck/OSIRIS to resolve a sample of gravitationally lensed DSFGs from the Herschel Lensing Survey (>100 mJy, with SFRs >100 Msun/yr) at redshifts z=1-4 with magnifications >10x all with previously detected nebular emission lines. We present the physical and resolved properties of gravitationally lensed DSFGs at unprecedented spatial scales; such as ionization, metallicity, AGN activity, and dust attenuation.

  14. Chondritic Meteorites: Nebular and Parent-Body Formation Processes

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Lindstrom, David (Technical Monitor)

    2002-01-01

    It is important to identify features in chondrites that formed as a result of parent-body modification in order to disentangle nebular and asteroidal processes. However, this task is difficult because unmetamorphosed chondritic meteorites are mixtures of diverse components including various types of chondrules, chondrule fragments, refractory and mafic inclusions, metal-sulfide grains and fine-grained matrix material. Shocked chondrites can contain melt pockets, silicate-darkened material, metal veins, silicate melt veins, and impact-melt-rock clasts. This grant paid for several studies that went far in helping to distinguish primitive nebular features from those produced during asteroidal modification processes.

  15. What the UV SED Tells us About Stellar Populations and Galaxies

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.

    2011-01-01

    The UV SED parameter b as in f(sub 1) 1(sup b), is commonly used to estimate fundamental properties of high-redshift galaxies including age and metallicity. However, sources and processes other than age and metallicity can influence the value of b. We use the local starforming dwarf galaxy, I Zw 18, in a case study to investigate uncertainties in age and metallicity inferred from b due errors or uncertainties in: mode of star formation (instantaneous starburst vs. continuous SF), dust extinction, nebular continuous emission (2-photon emission, Balmer continuum flux), and presence of older stars.

  16. ELSA: An integrated, semi-automated nebular abundance package

    NASA Astrophysics Data System (ADS)

    Johnson, Matthew D.; Levitt, Jesse S.; Henry, Richard B. C.; Kwitter, Karen B.

    We present ELSA, a new modular software package, written in C, to analyze and manage spectroscopic data from emission-line objects. In addition to calculating plasma diagnostics and abundances from nebular emission lines, the software provides a number of convenient features including the ability to ingest logs produced by IRAF's splot task, to semi-automatically merge spectra in different wavelength ranges, and to automatically generate various data tables in machine-readable or LaTeX format. ELSA features a highly sophisticated interstellar reddening correction scheme that takes into account temperature and density effects as well as He II contamination of the hydrogen Balmer lines. Abundance calculations are performed using a 5-level atom approximation with recent atomic data, based on R. Henry's ABUN program. Downloading and detailed documentation for all aspects of ELSA are available at the following URL:

  17. VizieR Online Data Catalog: Barred & unbarred galaxies N, O abundance ratio (Florido+, 2015)

    NASA Astrophysics Data System (ADS)

    Florido, E.; Zurita, A.; Perez, I.; Perez-Montero, E.; Coelho, P. R. T.; Gadotti, D. A.

    2015-11-01

    The tables contain nebular emission line fluxes for the central region of 251 barred and 324 unbarred galaxies. The sample contains all spiral face-on galaxies (axial ratio b/a>=0.9) in the SDSS DR-2, with stellar masses larger than 1010 the solar mass, redshift 0.02galaxy sample. (2 data files).

  18. Oxygen abundance distributions in six late-type galaxies based on SALT spectra of H II regions

    NASA Astrophysics Data System (ADS)

    Zinchenko, I. A.; Kniazev, A. Y.; Grebel, E. K.; Pilyugin, L. S.

    2015-10-01

    Spectra of 34 H ii regions in the late-type galaxies NGC 1087, NGC 2967, NGC 3023, NGC 4030, NGC 4123, and NGC 4517A were observed with the South African Large Telescope (SALT). In all 34 H ii regions, oxygen abundances were determined through the "counterpart" method (C method). Additionally, in two H ii regions in which we detected auroral lines, we measured oxygen abundances with the classic Te method. We also estimated the abundances in our H ii regions using the O3N2 and N2 calibrations and compared those with the C-based abundances. With these data, we examined the radial abundance distributions in the disks of our target galaxies. We derived surface-brightness profiles and other characteristics of the disks (the surface brightness at the disk center and the disk scale length) in three photometric bands for each galaxy using publicly available photometric imaging data. The radial distributions of the oxygen abundances predicted by the relation between abundance and disk surface brightness in the W1 band obtained for spiral galaxies in our previous study are close to the radial distributions of the oxygen abundances determined from the analysis of the emission line spectra for four galaxies where this relation is applicable. Hence, when the surface-brightness profile of a late-type galaxy is known, this parametric relation can be used to estimate the likely present-day oxygen abundance in the disk of the galaxy. Based on observations made with the Southern African Large Telescope, programs 2012-1-RSA_OTH-001, 2012-2-RSA_OTH-003 and 2013-1-RSA_OTH-005.

  19. The Extended Northern ROSAT Galaxy Cluster Survey (NORAS II). I. Survey Construction and First Results

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Böhringer, Hans; Chon, Gayoung; Trümper, Joachim

    As the largest, clearly defined building blocks of our universe, galaxy clusters are interesting astrophysical laboratories and important probes for cosmology. X-ray surveys for galaxy clusters provide one of the best ways to characterize the population of galaxy clusters. We provide a description of the construction of the NORAS II galaxy cluster survey based on X-ray data from the northern part of the ROSAT All-Sky Survey. NORAS II extends the NORAS survey down to a flux limit of 1.8 × 10{sup −12} erg s{sup −1} cm{sup −2} (0.1–2.4 keV), increasing the sample size by about a factor of two. The NORAS IImore » cluster survey now reaches the same quality and depth as its counterpart, the southern REFLEX II survey, allowing us to combine the two complementary surveys. The paper provides information on the determination of the cluster X-ray parameters, the identification process of the X-ray sources, the statistics of the survey, and the construction of the survey selection function, which we provide in numerical format. Currently NORAS II contains 860 clusters with a median redshift of z  = 0.102. We provide a number of statistical functions, including the log N –log S and the X-ray luminosity function and compare these to the results from the complementary REFLEX II survey. Using the NORAS II sample to constrain the cosmological parameters, σ {sub 8} and Ω{sub m}, yields results perfectly consistent with those of REFLEX II. Overall, the results show that the two hemisphere samples, NORAS II and REFLEX II, can be combined without problems into an all-sky sample, just excluding the zone of avoidance.« less

  20. Large-scale correlations in gas traced by Mg II absorbers around low-mass galaxies

    NASA Astrophysics Data System (ADS)

    Kauffmann, Guinevere

    2018-03-01

    The physical origin of the large-scale conformity in the colours and specific star formation rates of isolated low-mass central galaxies and their neighbours on scales in excess of 1 Mpc is still under debate. One possible scenario is that gas is heated over large scales by feedback from active galactic nuclei (AGNs), leading to coherent modulation of cooling and star formation between well-separated galaxies. In this Letter, the metal line absorption catalogue of Zhu & Ménard is used to probe gas out to large projected radii around a sample of a million galaxies with stellar masses ˜1010M⊙ and photometric redshifts in the range 0.4 < z < 0.8 selected from Sloan Digital Sky Survey imaging data. This galaxy sample covers an effective volume of 2.2 Gpc3. A statistically significant excess of Mg II absorbers is present around the red-low-mass galaxies compared to their blue counterparts out to projected radii of 10 Mpc. In addition, the equivalent width distribution function of Mg II absorbers around low-mass galaxies is shown to be strongly affected by the presence of a nearby (Rp < 2 Mpc) radio-loud AGNs out to projected radii of 5 Mpc.

  1. The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MegaSaura). I. The Sample and the Spectra

    NASA Astrophysics Data System (ADS)

    Rigby, J. R.; Bayliss, M. B.; Sharon, K.; Gladders, M. D.; Chisholm, J.; Dahle, H.; Johnson, T.; Paterno-Mahler, R.; Wuyts, E.; Kelson, D. D.

    2018-03-01

    We introduce Project MEGaSaURA: the Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises medium-resolution, rest-frame ultraviolet spectroscopy of N = 15 bright gravitationally lensed galaxies at redshifts of 1.68 < z < 3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range 3200 < λ o < 8280 Å the average spectral resolving power is R = 3300. The median spectrum has a signal-to-noise ratio (S/N) = 21 per resolution element at 5000 Å. As such, the MEGaSaURA spectra have superior S/N and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum. We provide the MEGaSaURA spectra to the astronomical community through a data release.

  2. Chasing passive galaxies in the early Universe: a critical analysis in CANDELS GOODS-South

    NASA Astrophysics Data System (ADS)

    Merlin, E.; Fontana, A.; Castellano, M.; Santini, P.; Torelli, M.; Boutsia, K.; Wang, T.; Grazian, A.; Pentericci, L.; Schreiber, C.; Ciesla, L.; McLure, R.; Derriere, S.; Dunlop, J. S.; Elbaz, D.

    2018-01-01

    We search for passive galaxies at z > 3 in the GOODS-South field, using different techniques based on photometric data, and paying attention to develop methods that are sensitive to objects that have become passive shortly before the epoch of observation. We use CANDELS HST catalogues, ultra-deep Ks data and new IRAC photometry, performing spectral energy distribution fitting using models with abruptly quenched star formation histories. We then single out galaxies which are best fitted by a passively evolving model, and having only low probability (<5 per cent) star-forming solutions. We verify the effects of including nebular lines emission, and we consider possible solutions at different redshifts. The number of selected sources dramatically depends on the models used in the spectral energy distribution (SED) fitting. Without including emission lines and with photometric redshifts fixed at the CANDELS estimate, we single out 30 candidates; the inclusion of nebular lines emission reduces the sample to 10 objects; allowing for solutions at different redshifts, only two galaxies survive as robust candidates. Most of the candidates are not far-infrared emitters, corroborating their association with passive galaxies. Our results translate into an upper limit in the number density of ∼0.173 arcmin2 above the detection limit. However, we conclude that the selection of passive galaxies at z > 3 is still subject to significant uncertainties, being sensitive to assumptions in the SED modelling adopted and to the relatively low S/N of the objects. By means of dedicated simulations, we show that JWST will greatly enhance the accuracy, allowing for a much more robust classification.

  3. Addressing the [O III] / Hβ offset in metal poor star forming galaxies found in the RESOLVE survey and ECO catalog

    NASA Astrophysics Data System (ADS)

    Richardson, Chris T.; Kannappan, Sheila; Moffett, Amanda J.; RESOLVE survey team

    2018-06-01

    Metal poor star forming galaxies sit on the far left wing of the BPT diagram just below traditional demarcation lines. The basic approach to reproducing their emission lines by coupling photoionization models to stellar population synthesis models underestimates the observed [O III] / Hβ ratio by a factor 0.3-0.5 dex. We classified galaxies as metal poor in the REsolved Spectroscopy of a Local VolumE (RESOLVE) survey and the Environmental COntext (ECO) catalog by using the IZI code based off of Bayesian inference. We used a variety of stellar population synthesis codes to generate SEDs covering a range of starburst ages and metallicities including both secular and binary stellar evolution. Here, we show that multiple SPS codes can produce SEDs hard enough to reduce the offset assuming that simple, and perhaps unjustified, nebular conditions hold. Adopting more realistic nebular conditions shows that, despite the recent emphasis placed on binary evolution to fit high O III ratios, none of our SEDs can reduce the offset. We propose several new solutions including using ensembles of nebular clouds and improved microphysics to address this issue. This work is supported by National Science Foundation awards OCI-1053575, though XSEDE award TG-AST140040, and NSF awards AST-0955368 and CISE/ACI-1156614.

  4. ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [C II] Emission in "Typical" Galaxies and Dusty Starbursts ≈1 Billion Years after the Big Bang

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Carilli, Christopher L.; Capak, Peter L.; Scoville, Nicholas Z.; Smolčić, Vernesa; Schinnerer, Eva; Yun, Min; Cox, Pierre; Bertoldi, Frank; Karim, Alexander; Yan, Lin

    2014-12-01

    We report interferometric imaging of [C II](2 P 3/2→2 P 1/2) and OH(2Π1/2 J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II](2 P 3/2→2 P 1/2) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 1010 M ⊙, and a star formation rate (SFR) surface density of ΣSFR = 530 M ⊙ yr-1 kpc-2. This suggests that AzTEC-3 forms stars at ΣSFR approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II](2 P 3/2→2 P 1/2) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ~95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 M ⊙ yr-1, consistent with a UV-based estimate of 22 M ⊙ yr-1. The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, "normal" star-forming galaxies at z > 5, showing that ALMA can detect the interstellar medium in "typical" galaxies in the very early universe.

  5. Kinematics, turbulence, and star formation of z ˜ 1 strongly lensed galaxies seen with MUSE

    NASA Astrophysics Data System (ADS)

    Patrício, V.; Richard, J.; Carton, D.; Contini, T.; Epinat, B.; Brinchmann, J.; Schmidt, K. B.; Krajnović, D.; Bouché, N.; Weilbacher, P. M.; Pelló, R.; Caruana, J.; Maseda, M.; Finley, H.; Bauer, F. E.; Martinez, J.; Mahler, G.; Lagattuta, D.; Clément, B.; Soucail, G.; Wisotzki, L.

    2018-06-01

    We analyse a sample of eight highly magnified galaxies at redshift 0.6 < z < 1.5 observed with MUSE, exploring the resolved properties of these galaxies at sub-kiloparsec scales. Combining multiband HST photometry and MUSE spectra, we derive the stellar mass, global star formation rates (SFRs), extinction and metallicity from multiple nebular lines, concluding that our sample is representative of z ˜ 1 star-forming galaxies. We derive the 2D kinematics of these galaxies from the [O II ] emission and model it with a new method that accounts for lensing effects and fits multiple images simultaneously. We use these models to calculate the 2D beam-smearing correction and derive intrinsic velocity dispersion maps. We find them to be fairly homogeneous, with relatively constant velocity dispersions between 15 and 80 km s-1 and Gini coefficient of {≲ }0.3. We do not find any evidence for higher (or lower) velocity dispersions at the positions of bright star-forming clumps. We derive resolved maps of dust attenuation and attenuation-corrected SFRs from emission lines for two objects in the sample. We use this information to study the relation between resolved SFR and velocity dispersion. We find that these quantities are not correlated, and the high-velocity dispersions found for relatively low star-forming densities seems to indicate that, at sub-kiloparsec scales, turbulence in high-z discs is mainly dominated by gravitational instability rather than stellar feedback.

  6. Dwarf galaxy populations in present-day galaxy clusters - II. The history of early-type and late-type dwarfs

    NASA Astrophysics Data System (ADS)

    Lisker, Thorsten; Weinmann, Simone M.; Janz, Joachim; Meyer, Hagen T.

    2013-06-01

    How did the dwarf galaxy population of present-day galaxy clusters form and grow over time? We address this question by analysing the history of dark matter subhaloes in the Millennium II cosmological simulation. A semi-analytic model serves as the link to observations. We argue that a reasonable analogue to early morphological types or red-sequence dwarf galaxies are those subhaloes that experienced strong mass-loss, or alternatively those that have spent a long time in massive haloes. This approach reproduces well the observed morphology-distance relation of dwarf galaxies in the Virgo and Coma clusters, and thus provides insight into their history. Over their lifetime, present-day late types have experienced an amount of environmental influence similar to what the progenitors of dwarf ellipticals had already experienced at redshifts above 2. Therefore, dwarf ellipticals are more likely to be a result of early and continuous environmental influence in group- and cluster-size haloes, rather than a recent transformation product. The observed morphological sequences of late-type and early-type galaxies have developed in parallel, not consecutively. Consequently, the characteristics of today's late-type galaxies are not necessarily representative for the progenitors of today's dwarf ellipticals. Studies aiming to reproduce the present-day dwarf population thus need to start at early epochs, model the influence of various environments, and also take into account the evolution of the environments themselves.

  7. Evolutionary behaviour of AGN: Investigations on BL Lac objects and Seyfert II galaxies

    NASA Astrophysics Data System (ADS)

    Beckmann, V.

    2000-12-01

    The evolution and nature of AGN is still one of the enigmatic questions in astrophysics. While large and complete Quasar samples are available, special classes of AGN, like BL Lac objects and Seyfert II galaxies, are still rare objects. In this work I present two new AGN samples. The first one is the HRX-BL Lac survey, resulting in a sample of X-ray selected BL Lac objects. This sample results from 223 BL Lac candidates based on a correlation of X-ray sources with radio sources. The identification of this sample is 98% complete. 77 objects have been identified as BL Lac objects and form the HRX-BL Lac complete sample, the largest homogeneous sample of BL Lac objects existing today. For this sample, redshifts are now known for 62 objects (81 %). In total I present 101 BL Lac objects in the enlarged HRX-BL Lac survey, for which redshift information is available for 84 objects. During the HRX-BL Lac survey I found several objects of special interest. 1ES 1517+656 turned out to be the brightest known BL Lac object in the universe. 1ES 0927+500 could be the first BL Lac object with a line detected in the X-ray region. RX J1211+2242 is probably the the counterpart of the up to now unidentified gamma-ray source 3EG J1212+2304. Additionally I present seven candidates for ultra high frequency peaked BL Lac objects. RX J1054+3855 and RX J1153+3517 are rare high redshift X-ray bright QSO or accreting binary systems with huge magnetic fields. For the BL Lac objects I suggest an unified scenario in which giant elliptical galaxies, formed by merging events of spiral galaxies at z > 2, start as powerful, radio dominated BL Lacs. As the jet gets less powerful, the BL Lacs start to get more X-ray dominated, showing less total luminosities (for z < 1). This effect is seen in the different evolutionary behavior detected in high and low frequency cut off BL Lac objects (HBL and LBL, respectively). The model of negative evolution is supported by assumptions about the energetic effects

  8. Dynamical Characterization of Galaxies at z ˜ 4-6 via Tilted Ring Fitting to ALMA [C II] Observations

    NASA Astrophysics Data System (ADS)

    Jones, G. C.; Carilli, C. L.; Shao, Y.; Wang, R.; Capak, P. L.; Pavesi, R.; Riechers, D. A.; Karim, A.; Neeleman, M.; Walter, F.

    2017-12-01

    Until recently, determining the rotational properties of galaxies in the early universe (z> 4, universe age < 1.5 Gyr) was impractical, with the exception of a few strongly lensed systems. Combining the high resolution and sensitivity of ALMA at (sub-)millimeter wavelengths with the typically high strength of the [C II] 158 μm emission line from galaxies and long-developed dynamical modeling tools raises the possibility of characterizing the gas dynamics in both extreme starburst galaxies and normal star-forming disk galaxies at z˜ 4{--}7. Using a procedure centered around GIPSY’s ROTCUR task, we have fit tilted ring models to some of the best available ALMA [C II] data of a small set of galaxies: the MS galaxies HZ9 and HZ10, the damped Lyα absorber host galaxy ALMA J0817+1351, the submm galaxies AzTEC/C159 and COSMOS J1000+0234, and the quasar host galaxy ULAS J1319+0950. This procedure directly derives rotation curves and dynamical masses as functions of radius for each object. In one case, we present evidence for a dark matter halo of { O }({10}11) {M}⊙ . We present an analysis of the possible velocity dispersions of two sources based on matching simulated observations to the integrated [C II] line profiles. Finally, we test the effects of observation resolution and sensitivity on our results. While the conclusions remain limited at the resolution and signal-to-noise ratios of these observations, the results demonstrate the viability of the modeling tools at high redshift, and the exciting potential for detailed dynamical analysis of the earliest galaxies, as ALMA achieves full observational capabilities.

  9. HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ji, Alexander P.; Frebel, Anna; Simon, Joshua D.

    2016-01-20

    We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Itsmore » variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.« less

  10. Uncovering multiple Wolf-Rayet star clusters and the ionized ISM in Mrk 178: the closest metal-poor Wolf-Rayet H II galaxy

    NASA Astrophysics Data System (ADS)

    Kehrig, C.; Pérez-Montero, E.; Vílchez, J. M.; Brinchmann, J.; Kunth, D.; García-Benito, R.; Crowther, P. A.; Hernández-Fernández, J.; Durret, F.; Contini, T.; Fernández-Martín, A.; James, B. L.

    2013-07-01

    New integral field spectroscopy (IFS) has been obtained for the nearby metal-poor Wolf-Rayet (WR) galaxy Mrk 178 to examine the spatial correlation between its WR stars and the neighbouring ionized interstellar medium (ISM). The strength of the broad WR features and its low metallicity make Mrk 178 an intriguing object. We have detected the blue and red WR bumps in different locations across the field of view (˜300 pc × 230 pc) in Mrk 178. The study of the WR content has been extended, for the first time, beyond its brightest star-forming knot uncovering new WR star clusters. Using Large/Small Magellanic Cloud-template WR stars, we empirically estimate a minimum of ˜20 WR stars within the region sampled. Maps of the spatial distribution of the emission lines and of the physical-chemical properties of the ionized ISM have been created and analysed. Here, we refine the statistical methodology by Pérez-Montero et al. (2011) to probe the presence of variations in the ISM properties. An error-weighted mean of 12+log(O/H) = 7.72 ± 0.01 is taken as the representative oxygen abundance for Mrk 178. A localized N and He enrichment, spatially correlated with WR stars, is suggested by this analysis. Nebular He II λ4686 emission is shown to be spatially extended reaching well beyond the location of the WR stars. This spatial offset between WRs and He II emission can be explained based on the mechanical energy input into the ISM by the WR star winds, and does not rule out WR stars as the He II ionization source. We study systematic aperture effects on the detection and measurement of the WR features, using Sloan Digital Sky Survey spectra combined with the power of IFS. In this regard, the importance of targeting low metallicity nearby systems is discussed.

  11. 3-Helium in Obscure H II Regions

    NASA Astrophysics Data System (ADS)

    Bania, T. M.; Rood, R. T.; Balser, D. S.

    1999-05-01

    The light isotope of helium, (3) He, can serve as a probe of cosmology, the evolution of low mass stars, and the chemical evolution of the Galaxy. Its abundance can be determined via measurements of the 3.46 cm hyperfine transition of (3) He(+) . Potentially observable sources of ionized gas include H ii regions and planetary nebulae. The selection of (3) He targets is counter-intuitive because the (3) He(+) hyperfine line strength is proportional to the source density, while one usually thinks of H ii regions in terms of radio continuum or recombination line strength both of which depend on the square of the density. The (3) He(+) line strength depends on the (3) He(+) abundance ratio and a number of other factors: $ TL(A}({) (3) He(+)) ~ frac {N((3) He(+)}{N() H(+)}) frac {({TC(A}}D)({1/2)) Te(1/4) (theta_obs (2) - theta_beam (2})({3/4}}{Delta {v}({)) (3) He(+)) [ln(5.717 x 10(-3}Te({3/2})]^{1/2)) theta_obs } where T_L^A and Delta v are the antenna temperature and FWHM of the ^3He^+ line, D is the nebular distance, T_C^A and theta_obs are the antenna temperature and observed FWHM angular size of the continuum emission, theta_beam is the telescope's FWHM beam, and Te is the nebular electron temperature. For H {sc ii} regions much larger than the telescope beam we can select targets using the criterion: TLA(^3He^+)\\sim\\sqrt{TCA D\\theta_obs}. This is the case since we can neglect the weak dependence on T_e and because we do not know either ^3He^{+}/H^+ or Delta v. Thus big, distant H ii regions could be potential ^3He^+ targets even if their continuum emission is weak. Armed with this knowledge we included H ii regions like S209 in our early observing list along with more famous sources like W43. Still we did not have the temerity to push this reasoning to the limit. We have now found, however, that this selection criterion is valid for even the wimpiest known H ii regions. Here we report on the detection of ^3He^+$ emission in 8 distant, low density H ii regions.

  12. EVIDENCE THAT GAMMA-RAY BURST 130702A EXPLODED IN A DWARF SATELLITE OF A MASSIVE GALAXY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kelly, Patrick L.; Filippenko, Alexei V.; Fox, Ori D.

    2013-09-20

    GRB 130702A is a nearby long-duration gamma-ray burst (LGRB) discovered by the Fermi satellite whose associated afterglow was detected by the Palomar Transient Factory. Subsequent photometric and spectroscopic monitoring has identified a coincident broad-lined Type Ic supernova (SN), and nebular emission detected near the explosion site is consistent with a redshift of z = 0.145. The SN-GRB exploded at an offset of {approx}7.''6 from the center of an inclined r = 18.1 mag red disk-dominated galaxy, and {approx}0.''6 from the center of a much fainter r = 23 mag object. We obtained Keck-II DEIMOS spectra of the two objects andmore » find a 2{sigma} upper limit on their line-of-sight velocity offset of {approx}<60 km s{sup -1}. If we calculate the inclination angle of the massive red galaxy from its axis ratio and assume that its light is dominated by a very thin disk, the explosion would have a {approx}60 kpc central offset, or {approx}9 times the galaxy's half-light radius. A significant bulge or a thicker disk would imply a higher inclination angle and greater central offset. The substantial offset suggests that the faint source is a separate dwarf galaxy. The star-formation rate of the dwarf galaxy is {approx}0.05 M{sub Sun} yr{sup -1}, and we place an upper limit on its oxygen abundance of 12 + log(O/H) < 8.16 dex. The identification of an LGRB in a dwarf satellite of a massive, metal-rich primary galaxy suggests that recent detections of LGRBs spatially coincident with metal-rich galaxies may be, in some cases, superpositions.« less

  13. ALMA imaging of gas and dust in a galaxy protocluster at redshift 5.3: [C II] emission in 'typical' galaxies and dusty starbursts ≈1 billion years after the big bang

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Riechers, Dominik A.; Carilli, Christopher L.; Capak, Peter L.

    2014-12-01

    We report interferometric imaging of [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) and OH({sup 2}Π{sub 1/2} J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 10{sup 10} M {sub ☉}, and a star formation rate (SFR)more » surface density of Σ{sub SFR} = 530 M {sub ☉} yr{sup –1} kpc{sup –2}. This suggests that AzTEC-3 forms stars at Σ{sub SFR} approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ∼95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 M {sub ☉} yr{sup –1}, consistent with a UV-based estimate of 22 M {sub ☉} yr{sup –1}. The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, 'normal' star-forming galaxies at z > 5, showing that ALMA can detect the interstellar medium in 'typical' galaxies in the very early universe.« less

  14. The One Micron Fe II Lines in Active Galaxies and Emission Line Stars

    NASA Astrophysics Data System (ADS)

    Rudy, R. J.; Mazuk, S.; Puetter, R. C.; Hamann, F. W.

    1999-05-01

    The infrared multiplet of Fe II lines at 0.9997, 1.0501, 1.0863, and 1.1126 microns are particularly strong relative to other red and infrared Fe II features. They reach their greatest strength, relative to the hydrogen lines, in the Seyfert 1 galaxy I Zw 1, and are a common, although not ubiquitous feature, in the broad line regions of active galaxies. In addition, they are seen in a diverse assortment of Galactic sources including young stars, Herbig Ae and Be stars, luminous blue variables, proto-planetary nebulae, and symbiotic novae. They are probably excited by Lyman alpha florescence but the exact path of the cascade to their upper levels is uncertain. They arise in dense, sheltered regions of low ionization and are frequently observed together with the infrared Ca II triplet and the Lyman beta excited O I lines 8446 and 11287. The strengths of the four Fe II features, relative to each other, are nearly constant from object to object suggesting a statistical population of their common upper multiplet. Their intensities, in comparison to the Paschen lines, indicate that they can be important coolants for regions with high optical depths in the hydrogen lines. In addition to I Zw 1 and other active galaxies, we present spectra for the Galactic sources MWC 17, MWC 84, MWC 340, MWC 922, PU Vul, and M 1-92. We review the status of the Fe II observations and discuss the excitation process and possible implications. This work was supported by the IR&D program of the Aerospace Corporation. RCP and FWH acknowledge support from NASA.

  15. A Foreground Masking Strategy for [C II] Intensity Mapping Experiments Using Galaxies Selected by Stellar Mass and Redshift

    NASA Astrophysics Data System (ADS)

    Sun, G.; Moncelsi, L.; Viero, M. P.; Silva, M. B.; Bock, J.; Bradford, C. M.; Chang, T.-C.; Cheng, Y.-T.; Cooray, A. R.; Crites, A.; Hailey-Dunsheath, S.; Uzgil, B.; Hunacek, J. R.; Zemcov, M.

    2018-04-01

    Intensity mapping provides a unique means to probe the epoch of reionization (EoR), when the neutral intergalactic medium was ionized by energetic photons emitted from the first galaxies. The [C II] 158 μm fine-structure line is typically one of the brightest emission lines of star-forming galaxies and thus a promising tracer of the global EoR star formation activity. However, [C II] intensity maps at 6 ≲ z ≲ 8 are contaminated by interloping CO rotational line emission (3 ≤ J upp ≤ 6) from lower-redshift galaxies. Here we present a strategy to remove the foreground contamination in upcoming [C II] intensity mapping experiments, guided by a model of CO emission from foreground galaxies. The model is based on empirical measurements of the mean and scatter of the total infrared luminosities of galaxies at z < 3 and with stellar masses {M}* > {10}8 {M}ȯ selected in the K-band from the COSMOS/UltraVISTA survey, which can be converted to CO line strengths. For a mock field of the Tomographic Ionized-carbon Mapping Experiment, we find that masking out the “voxels” (spectral–spatial elements) containing foreground galaxies identified using an optimized CO flux threshold results in a z-dependent criterion {m}{{K}}AB}≲ 22 (or {M}* ≳ {10}9 {M}ȯ ) at z < 1 and makes a [C II]/COtot power ratio of ≳10 at k = 0.1 h/Mpc achievable, at the cost of a moderate ≲8% loss of total survey volume.

  16. THE NATURE OF A GALAXY ALONG THE SIGHT LINE TO PKS 0454+039

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Takamiya, Marianne; Chun, Mark; Kulkarni, Varsha P.

    2012-10-01

    We report on the properties of a faint blue galaxy (G1) along the line of sight to the QSO PKS 0454+039 from spectroscopic and imaging data. We measured emission lines of H{alpha}, [S II] {lambda}{lambda}6716, 6732, and [N II] {lambda}6584 in the spectrum of G1 obtained with the Gemini/GMOS instrument. The spectroscopic redshift of G1 is z = 0.0715 {+-} 0.0002. From the extinction-corrected H{alpha} flux, we determine a modest star formation rate of SFR = 0.07 M{sub Sun} yr{sup -1} and a specific SFR of log (sSFR) -8.4. Using three different abundance indicators, we determine a nebular abundance 12more » + log (O/H) ranging from 7.6 to 8.2. Based on the velocity dispersion inferred from the emission line widths and the observed surface brightness profile, we estimate the virial mass of G1 to be M{sub vir} {approx} 6.7 Multiplication-Sign 10{sup 9} M{sub Sun} with an effective radius of 2.0 kpc. We estimate the stellar mass of G1 using spectral energy distribution fitting to be M{sub *} Almost-Equal-To 1.2 Multiplication-Sign 10{sup 7} M{sub Sun} and an r'-luminosity of L{sub r'} = 1.5x10{sup 8} L{sub Sun }. Overall, G1 is a faint, low-mass, low-metallicity Im/H II galaxy. We also report on the line flux limits of another source (G3) which is the most likely candidate for the absorber system at z = 0.8596. From the spectrum of the QSO itself, we report a previously undetected Mg II {lambda}{lambda}2796, 2803 absorption line system at z = 1.245.« less

  17. [C ii] 158-μm emission from the host galaxies of damped Lyman-alpha systems.

    PubMed

    Neeleman, Marcel; Kanekar, Nissim; Prochaska, J Xavier; Rafelski, Marc; Carilli, Chris L; Wolfe, Arthur M

    2017-03-24

    Gas surrounding high-redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. However, it has proven difficult to identify and characterize the galaxies associated with these absorbers due to the intrinsic faintness of the galaxies compared with the quasars at optical wavelengths. Using the Atacama Large Millimeter/Submillimeter Array, we report on detections of [C ii] 158-μm line and dust-continuum emission from two galaxies associated with two such absorbers at a redshift of z ~ 4. Our results indicate that the hosts of these high-metallicity absorbers have physical properties similar to massive star-forming galaxies and are embedded in enriched neutral hydrogen gas reservoirs that extend well beyond the star-forming interstellar medium of these galaxies. Copyright © 2017, American Association for the Advancement of Science.

  18. The Ly(alpha) Line Profiles of Ultraluminous Infrared Galaxies: Fast Winds and Lyman Continuum Leakage

    NASA Technical Reports Server (NTRS)

    Martin, Crystal L.; Dijkstra, Mark; Henry, Alaina L.; Soto, Kurt T.; Danforth, Charles W.; Wong, Joseph

    2015-01-01

    We present new Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet (far-UV) spectroscopy and Keck Echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ULIRGs), a rare population of local galaxies experiencing massive gas inflows, extreme starbursts, and prominent outflows. We detect Ly(alpha) emission from eight ULIRGs and the companion to IRAS09583+4714. In contrast to the P Cygni profiles often seen in galaxy spectra, the Ly(alpha) profiles exhibit prominent, blueshifted emission out to Doppler shifts exceeding -1000 km/s in three H II-dominated and two AGN-dominated ULIRGs. To better understand the role of resonance scattering in shaping the Ly(alpha) line profiles, we directly compare them to non-resonant emission lines in optical spectra. We find that the line wings are already present in the intrinsic nebular spectra, and scattering merely enhances the wings relative to the line core. The Ly(alpha) attenuation (as measured in the COS aperture) ranges from that of the far-UV continuum to over 100 times more. A simple radiative transfer model suggests the Ly(alpha) photons escape through cavities which have low column densities of neutral hydrogen and become optically thin to the Lyman continuum in the most advanced mergers. We show that the properties of the highly blueshifted line wings on the Ly(alpha) and optical emission-line profiles are consistent with emission from clumps of gas condensing out of a fast, hot wind. The luminosity of the Ly(alpha) emission increases nonlinearly with the ULIRG bolometric luminosity and represents about 0.1-1% of the radiative cooling from the hot winds in the H II-dominated ULIRGs.

  19. Can Lightning Produce Significant Levels of Mass-Independent Oxygen Isotopic Fractionation in Nebular Dust?

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A.; Paquette, John A.; Farquhar, Adam

    2012-01-01

    Based on recent evidence that oxide grains condensed from a plasma will contain oxygen that is mass independently fractionated compared to the initial composition of the vapor, we present a first attempt to evaluate the potential magnitude of this effect on dust in the primitive solar nebula. This assessment relies on previous studies of nebular lightning to provide reasonable ranges of physical parameters to form a very simple model to evaluate the plausibility that lightning could affect a significant fraction of nebular dust and that such effects could cause a significant change in the oxygen isotopic composition of solids in the solar nebula over time. If only a small fraction of the accretion energy is dissipated as lightning over the volume of the inner solar nebula, then a large fraction of nebular dust will be exposed to lightning. If the temperature of such bolts is a few percent of the temperatures measured in terrestrial discharges, then dust will vaporize and recondense in an ionized environment. Finally, if only a small average decrease is assumed in the O-16 content of freshly condensed dust, then over the last 5 million years of nebular accretion the average delta O-17 of the dust could increase by more than 30 per mil. We conclude that it is possible that the measured " slope 1" oxygen isotope line measured in meteorites and their components represents a time-evolution sequence of nebular dust over the last several million years of nebular evolution O-16-rich materials formed first, then escaped further processing as the average isotopic composition of the dust graduaUy became increasingly depleted in O-16 .

  20. The Nebular Hypothesis - A False Paradigm Misleading Scientists

    NASA Astrophysics Data System (ADS)

    Myers, L. S.

    2005-05-01

    Science has reached a turning point in history after being misled for 250 years by Immanuel Kant's nebular hypothesis, the most fundamental assumption in science. The nebular hypothesis assumes all nine planets were created 4.5 billion years ago (Ga) as molten bodies that cooled with the same size and chemical composition they have today. Reevaluation of the nebular hypothesis proves it has been wrong since its inception. The proof has lain in plain sight for centuries-coal beds that could not have existed at the assumed time of creation because they formed on Earth's surface after creation of the planet when forests and swamps were exposed to solar energy. The coal beds were subsequently buried under overburden accreted in later millennia, steadily increasing Earth's mass and diameter. The coal beds and layers of overburden are proof Earth was not created 4.5 Ga but is growing and expanding by accretion of extraterrestrial mass and core expansion-a process termed "Accreation" (creation by accretion). Each process accelerates over time, but internal expansion exceeds the rate of external accretion. Because the nebular hypothesis is erroneous researchers assumed Earth's diameter never changes, and, faced with the possibility the Earth might be expanding after the Atlantic basin was discovered to be widening, this assumption led to the unworkable concept of subduction to maintain a constant diameter Earth. Subduction will prove to be one of the greatest errors in the history of science. Nullification of the nebular hypothesis also nullifies subduction and rejuvenates Carey's earth expansion theory. Accreation provides Carey's missing energy source and mechanism of expansion. Expansion is proved by morphologic evidence today's continents were once a single planetary landmass on a smaller Earth when today's oceans, covering 70% of the planet, did not exist 200-250 Ma. Despite hundreds of tons of meteorites and dust known to accrete daily, its cumulative effect has been

  1. Exploring the Nature of Galaxies with Abundance Gradient Anomalies in the SDSS-IV/MaNGA Survey

    NASA Astrophysics Data System (ADS)

    Keith, Celeste; Tremonti, Christy; Pace, Zach; Schaefer, Adam

    2018-01-01

    Disk galaxies are known to have radial oxygen abundance gradients with their centers being more chemically enriched than their outskirts. The steepness of the abundance gradient has recently been shown to correlate with galaxy stellar mass, on average. However, individual galaxies sometimes show pronounced deviations from the expected trends, such as flatter or steeper slopes than expected for their mass, abrupt changes in slope, or azimuthal asymmetries. Here we report on a systematic search for galaxies with abundance gradient anomalies using 2-D spectroscopy from the Sloan Digital Sky Survey IV MaNGA. We construct nebular oxygen and nitrogen abundance maps for 300 moderately inclined non-interacting disk galaxies and use visual inspection to identify the most interesting cases. We use this training set to develop an automated pipeline to flag galaxies with abundance anomalies from the larger MaNGA dataset for visual inspection. We combine the metallicity maps with kinematic data and measurements of the galaxies' local environments to better understand the processes that shape the radial abundance gradients of disk galaxies.

  2. Detectability of [C II] 158 μm Emission from High-Redshift Galaxies: Predictions for ALMA and SPICA

    NASA Astrophysics Data System (ADS)

    Nagamine, Kentaro; Wolfe, Arthur M.; Hernquist, Lars

    2006-08-01

    We discuss the detectability of high-redshift galaxies via [C II] 158 μm line emission by coupling an analytic model with cosmological smoothed particle hydrodynamics (SPH) simulations that are based on the concordance Λ cold dark matter (CDM) model. Our analytic model describes a multiphase interstellar medium (ISM) irradiated by the far-ultraviolet (FUV) radiation from local star-forming regions, and it calculates thermal and ionization equilibrium between cooling and heating. The model allows us to predict the mass fraction of a cold neutral medium (CNM) embedded in a warm neutral medium (WNM). Our cosmological SPH simulations include a treatment of radiative cooling/heating, star formation, and feedback effects from supernovae and galactic winds. Using our method, we make predictions for the [C II] luminosity from high-redshift galaxies that can be directly compared with upcoming observations by the Atacama Large Millimeter Array (ALMA) and the Space Infrared Telescope for Cosmology and Astrophysics (SPICA). We find that the number density of high-redshift galaxies detectable by ALMA and SPICA via [C II] emission depends significantly on the amount of neutral gas, which is highly uncertain. Our calculations suggest that, in a CDM universe, most [C II] sources at z=3 are faint objects with Sν<0.01 mJy. Lyman break galaxies (LBGs) brighter than RAB=23.5 mag are expected to have flux densities Sν=1-3 mJy depending on the strength of galactic wind feedback. The recommended observing strategy for ALMA and SPICA is to aim at very bright LBGs or star-forming DRG/BzK galaxies.

  3. Physical Conditions of a Lensed Star-Forming Galaxy at Z=1.7

    NASA Technical Reports Server (NTRS)

    Rigby, Jane; Wuyts, E.; Gladders, M.; Sharon, K.; Becker, G. D.

    2010-01-01

    We report rest-frame optical Keck/NIRSPEC spectroscopy of the brightest lensed galaxy yet discovered, RCSGA 032727-132609 at z=1.7037. From precise measurements of the nebular lines, we infer a number of physical properties: redshift, extinction, star formation rate, ionization parameter, electron density, electron temperature, oxygen abundance, and N/O, Ne/O, and Ar/O abundance ratios. The limit on [O III] 4363 A tightly constrains the oxygen abundance via the "direct" or Tc method, for the first time in all metallicity galaxy at z approx.2. We compare this result to several standard "bright-line" O abundance diagnostics, thereby testing these empirically calibrated diagnostics in situ. Finally, we explore the positions of lensed and unlensed galaxies in standard diagnostic diagrams, and explore the diversity of ionization conditions and mass-metallicity ratios at z=2.

  4. Dust Emission at 8 and 24 μm as Diagnostics of H II Region Radiative Transfer

    NASA Astrophysics Data System (ADS)

    Oey, M. S.; López-Hernández, J.; Kellar, J. A.; Pellegrini, E. W.; Gordon, K. D.; Jameson, K. E.; Li, A.; Madden, S. C.; Meixner, M.; Roman-Duval, J.; Bot, C.; Rubio, M.; Tielens, A. G. G. M.

    2017-07-01

    We use the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) survey of the Magellanic Clouds to evaluate the relationship between the 8 μm polycyclic aromatic hydrocarbon (PAH) emission, 24 μm hot dust emission, and H II region radiative transfer. We confirm that in the higher-metallicity Large Magellanic Cloud, PAH destruction is sensitive to optically thin conditions in the nebular Lyman continuum: objects identified as optically thin candidates based on nebular ionization structure show six times lower median 8 μm surface brightness (0.18 mJy arcsec-2) than their optically thick counterparts (1.2 mJy arcsec-2). The 24 μm surface brightness also shows a factor of three offset between the two classes of objects (0.13 versus 0.44 mJy arcsec-2, respectively), which is driven by the association between the very small dust grains and higher density gas found at higher nebular optical depths. In contrast, PAH and dust formation in the low-metallicity Small Magellanic Cloud is strongly inhibited such that we find no variation in either 8 μm or 24 μm emission between our optically thick and thin samples. This is attributable to extremely low PAH and dust production together with high, corrosive UV photon fluxes in this low-metallicity environment. The dust mass surface densities and gas-to-dust ratios determined from dust maps using Herschel HERITAGE survey data support this interpretation.

  5. VizieR Online Data Catalog: MgII/FeII absorption profile for 0.3galaxies (Rubin+, 2014)

    NASA Astrophysics Data System (ADS)

    Rubin, K. H. R.; Prochaska, J. X.; Koo, D. C.; Phillips, A. C.; Martin, C. L.; Winstrom, L. O.

    2017-05-01

    In this work, we use rest-frame near-UV spectroscopy of a sample of 105 galaxies at 0.3II λλ2796, 2803 and Fe II λλ2586, 2600 absorption. This sample, drawn from redshift surveys of the GOODS and EGS fields (e.g., Wirth et al. 2004, J/AJ/127/3121; Davis et al. 2003SPIE.4834..161D; Le Fevre et al. 2005A&A...439..845L; Szokoly et al. 2004, J/ApJS/155/271), fully covers the SFR-M* parameter space occupied by star-forming galaxies with logM*/Msun>~9.6 down to a SFR limit>~2 Msun/yr at z~0.5, permitting exploration of outflow properties over the entire breadth of the star-forming sequence at z>0.3 for the first time. Our galaxy sample is drawn from pre-existing photometric and spectroscopic redshift surveys in fields with deep imaging taken with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). (3 data files).

  6. Optical/Near-IR spatially resolved study of the H II galaxy Tol 02★

    NASA Astrophysics Data System (ADS)

    Torres-Campos, A.; Terlevich, E.; Rosa-González, D.; Terlevich, R.; Telles, E.; Díaz, A. I.

    2017-11-01

    The main goal of this study is to characterize the stellar populations in very low-metallicity galaxies. We have obtained broad U, B, R, I, J, H, K, intermediate Strömgren y and narrow H α and [O III] deep images of the Wolf-Rayet, blue compact dwarf, H II galaxy Tol 02. We have analysed the low surface brightness component, the stellar cluster complexes and the H II regions. The stellar populations in the galaxy have been characterized by comparing the observed broad-band colours with those of single stellar population models. The main results are consistent with Tol 02 being formed by a 1.5 Gyr old disc component at the centre of which a group of eight massive (>104 M⊙) stellar cluster clumps is located. Six of these clumps are 10 Myr old and their near-infrared colours suggest that their light is dominated by Red Supergiant (RSG) stars, the other two are young Wolf-Rayet cluster candidates of ages 3 and 5 Myr, respectively. 12 H II regions in the star-forming region of the galaxy are also identified. These are immersed in a diffuse H α and [O III] emission that spreads towards the north and south covering the old stellar disc. Our spatial-temporal analysis shows that star formation is more likely stochastic and simultaneous within short time-scales. The mismatch between observations and models cannot be attributed alone to a mistreat of the RSG phase and still needs to be further investigated.

  7. POX 186: the ultracompact blue compact dwarf galaxy reveals its nature

    NASA Astrophysics Data System (ADS)

    Doublier, V.; Kunth, D.; Courbin, F.; Magain, P.

    2000-01-01

    High resolution, ground based R and I band observations of the ultra compact dwarf galaxy POX 186 are presented. The data, obtained with the ESO New Technology Telescope (NTT), are analyzed using a new deconvolution algorithm which allows one to resolve the innermost regions of this stellar-like object into three Super-Star Clusters (SSC). Upper limits to both masses (M ~ 105 Msun) and physical sizes (<=60pc) of the SSCs are set. In addition, and maybe most importantly, extended light emission underlying the compact star-forming region is clearly detected in both bands. The R-I color rules out nebular Hα contamination and is consistent with an old stellar population. This casts doubt on the hypothesis that Blue Compact Dwarf Galaxies (BCDG) are young galaxies. based on observations carried out at NTT in La Silla, operated by the European Southern Observatory, during Director's Discretionary Time.

  8. Spectroscopic aperture biases in inside-out evolving early-type galaxies from CALIFA

    NASA Astrophysics Data System (ADS)

    Gomes, J. M.; Papaderos, P.; Vílchez, J. M.; Kehrig, C.; Iglesias-Páramo, J.; Breda, I.; Lehnert, M. D.; Sánchez, S. F.; Ziegler, B.; Dos Reis, S. N.; Bland-Hawthorn, J.; Galbany, L.; Bomans, D. J.; Rosales-Ortega, F. F.; Walcher, C. J.; García-Benito, R.; Márquez, I.; Del Olmo, A.; Mollá, M.; Marino, R. A.; Catalán-Torrecilla, C.; González Delgado, R. M.; López-Sánchez, Á. R.; Califa Collaboration

    2016-02-01

    Integral field spectroscopy (IFS) studies based on CALIFA survey data have recently revealed ongoing low-level star formation (SF) in the periphery of a small fraction (~10%) of local early-type galaxies (ETGs), witnessing a still ongoing inside-out galaxy growth process. A distinctive property of the nebular component in these ETGs, classified I+, is a structure with two radial zones, the inner of which displays LINER emission with a Hα equivalent width EW(Hα) ≃ 1 Å, the outer (3 Å nebular emission to the galaxy periphery leads to a strong aperture (or, correspondingly, redshift) bias in spectroscopic single-fiber studies of type I+ ETGs: at low redshift (z ≲ 0.45), SDSS spectroscopy is restricted to the inner (SF-devoid LINER) zone, which causes the galaxies to be erroneously classified as "retired", that is, systems entirely lacking SF, and whose faint nebular emissionis solely powered by the post-AGB stellar component. The SDSS aperture progressively encompasses the outer SF zone only at higher z, at which the galaxies are unambiguously classified as "composite SF/LINER". We also empirically demonstrate that the principal effect of a decreasing spectroscopic aperture on the classification of I+ ETGs through standard [Nii]/Hα vs. [Oiii]/Hβ emission-line (BPT) ratios consists of a monotonic shift upward and to the right precisely along the upper right wing of the "seagull" distribution on the BPT plane, that is, along the pathway connecting composite SF/Hii galaxies with AGN/LINERs. Motivated by these observational insights, we also investigate theoretically observational biases in aperture-limited studies of inside-out growing galaxies as a function of z. To this end, we devise a simple 1D model that involves an outward-propagating exponentially decreasing SF process since z ~ 10 and reproduces the radial extent and two-zone EW

  9. A HERSCHEL SURVEY OF THE [N II] 205 {mu}m LINE IN LOCAL LUMINOUS INFRARED GALAXIES: THE [N II] 205 {mu}m EMISSION AS A STAR FORMATION RATE INDICATOR

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao Yinghe; Gao Yu; Lu, Nanyao

    2013-03-01

    We present, for the first time, a statistical study of [N II] 205 {mu}m line emission for a large sample of local luminous infrared galaxies using Herschel Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (SPIRE FTS) data. For our sample of galaxies, we investigate the correlation between the [N II] luminosity (L{sub [N{sub II]}}) and the total infrared luminosity (L{sub IR}), as well as the dependence of L{sub [N{sub II]}}/L{sub IR} ratio on L{sub IR}, far-infrared colors (IRAS f{sub 60}/f{sub 100}), and the [O III] 88 {mu}m to [N II] luminosity ratio. We find that L{sub [N{sub II]}} correlatesmore » almost linearly with L{sub IR} for non-active galactic nucleus galaxies (all having L{sub IR} < 10{sup 12} L{sub Sun }) in our sample, which implies that L{sub [N{sub II]}} can serve as a star formation rate tracer which is particularly useful for high-redshift galaxies that will be observed with forthcoming submillimeter spectroscopic facilities such as the Atacama Large Millimeter/submillimeter Array. Our analysis shows that the deviation from the mean L{sub [N{sub II]}}-L{sub IR} relation correlates with tracers of the ionization parameter, which suggests that the scatter in this relation is mainly due to the variations in the hardness, and/or ionization parameter, of the ambient galactic UV field among the sources in our sample.« less

  10. Galactic-scale Feedback Observed in the 3C 298 Quasar Host Galaxy

    NASA Astrophysics Data System (ADS)

    Vayner, Andrey; Wright, Shelley A.; Murray, Norman; Armus, Lee; Larkin, James E.; Mieda, Etsuko

    2017-12-01

    We present high angular resolution multiwavelength data of the 3C 298 radio-loud quasar host galaxy (z = 1.439) taken using the W.M. Keck Observatory OSIRIS integral field spectrograph (IFS) with adaptive optics, the Atacama Large Millimeter/submillimeter Array (ALMA), the Hubble Space Telescope (HST) WFC3, and the Very Large Array (VLA). Extended emission is detected in the rest-frame optical nebular emission lines Hβ, [O III], Hα, [N II], and [S II], as well as in the molecular lines CO (J = 3‑2) and (J = 5‑4). Along the path of the relativistic jets of 3C 298, we detect conical outflows in ionized gas emission with velocities of up to 1700 {km} {{{s}}}-1 and an outflow rate of 450–1500 {M}ȯ {{yr}}-1 extended over 12 kpc. Near the spatial center of the conical outflow, CO (J = 3‑2) emission shows a molecular gas disk with a rotational velocity of ±150 {km} {{{s}}}-1 and total molecular mass ({M}{{{H}}2}) of 6.6+/- 0.36× {10}9 {M}ȯ . On the blueshifted side of the molecular disk, we observe broad extended emission that is due to a molecular outflow with a rate of 2300 {M}ȯ {{yr}}-1 and depletion timescale of 3 Myr. We detect no narrow Hα emission in the outflow regions, suggesting a limit on star formation of 0.3 {M}ȯ {{yr}}-1 {{kpc}}-2. Quasar-driven winds are evacuating the molecular gas reservoir, thereby directly impacting star formation in the host galaxy. The observed mass of the supermassive black hole is {10}9.37{--9.56} {M}ȯ , and we determine a dynamical bulge mass of {M}{bulge}=1{--}1.7× {10}10\\tfrac{R}{1.6 {kpc}} {M}ȯ . The bulge mass of 3C 298 lies 2–2.5 orders of magnitude below the expected value from the local galactic bulge—supermassive black hole mass ({M}{bulge}{--}{M}{BH}) relationship. A second galactic disk observed in nebular emission is offset from the quasar by 9 kpc, suggesting that the system is an intermediate-stage merger. These results show that galactic-scale negative feedback is occurring early in the merger

  11. The Dragonfly Nearby Galaxies Survey. II. Ultra-Diffuse Galaxies near the Elliptical Galaxy NGC 5485

    NASA Astrophysics Data System (ADS)

    Merritt, Allison; van Dokkum, Pieter; Danieli, Shany; Abraham, Roberto; Zhang, Jielai; Karachentsev, I. D.; Makarova, L. N.

    2016-12-01

    We present the unexpected discovery of four ultra-diffuse galaxies (UDGs) in a group environment. We recently identified seven extremely low surface brightness galaxies in the vicinity of the spiral galaxy M101, using data from the Dragonfly Telephoto Array. The galaxies have effective radii of 10″-38″ and central surface brightnesses of 25.6-27.7 mag arcsec-2 in the g-band. We subsequently obtained follow-up observations with HST to constrain the distances to these galaxies. Four remain persistently unresolved even with the spatial resolution of HST/ACS, which implies distances of D\\gt 17.5 Mpc. We show that the galaxies are most likely associated with a background group at ˜27 Mpc containing the massive ellipticals NGC 5485 and NGC 5473. At this distance, the galaxies have sizes of 2.6-4.9 kpc, and are classified as UDGs, similar to the populations that have been revealed in clusters such as Coma, Virgo, and Fornax, yet even more diffuse. The discovery of four UDGs in a galaxy group demonstrates that the UDG phenomenon is not exclusive to cluster environments. Furthermore, their morphologies seem less regular than those of the cluster populations, which may suggest a different formation mechanism or be indicative of a threshold in surface density below which UDGs are unable to maintain stability.

  12. The Physical Conditions of a Lensed Star-Forming Galaxy at Z=1.7

    NASA Technical Reports Server (NTRS)

    Rigby, Jane; Wuyts, E.; Gladders, M.; Sharon, K.; Becker, G.

    2011-01-01

    We report rest-frame optical Keck/NIRSPEC spectroscopy of the brightest lensed galaxy yet discovered, RCSGA 032727-132609 at z=1.7037. From precise measurements of the nebular lines, we infer a number of physical properties: redshift ' extinction, star formation rate ' ionization parameter, electron density, electron temperature, oxygen abundance, and N/O, Ne/O, and Ar/O abundance ratios, The limit on [O III] 4363 A tightly constrains the oxygen abundance via the "direct" or Te method, for the first time in an average-metallicity galaxy at z approx.2. We compare this result to several standard "bright-line" O abundance diagnostics, thereby testing these empirically-calibrated diagnostics in situ. Finally, we explore the positions of lensed and unlensed galaxies in standard diagnostic diagrams, to explore the diversity of ionization conditions and mass-metallicity ratios at z=2.

  13. AGN jet power, formation of X-ray cavities, and FR I/II dichotomy in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Fujita, Yutaka; Kawakatu, Nozomu; Shlosman, Isaac

    2016-04-01

    We investigate the ability of jets in active galactic nuclei to break out of the ambient gas with sufficiently large advance velocities. Using observationally estimated jet power, we analyze 28 bright elliptical galaxies in nearby galaxy clusters. Because the gas density profiles in the innermost regions of galaxies have not been resolved so far, we consider two extreme cases for temperature and density profiles. We also follow two types of evolution for the jet cocoons: being driven by the pressure inside the cocoon [Fanaroff-Riley (FR) type I], and being driven by the jet momentum (FR type II). Our main result is that regardless of the assumed form of the density profiles, jets with observed powers of ≲1044 erg s-1 are not powerful enough to evolve as FR II sources. Instead, they evolve as FR I sources and appear to be decelerated below the buoyant velocities of the cocoons when jets were propagating through the central dense regions of the host galaxies. This explains why FR I sources are more frequent than FR II sources in clusters. Furthermore, we predict the sizes of X-ray cavities from the observed jet powers and compare them with the observed ones-they are consistent within a factor of two if the FR I type evolution is realized. Finally, we find that the jets with a power ≳1044 erg s-1 are less affected by the ambient medium, and some of them, but not all, could serve as precursors of the FR II sources.

  14. THE STELLAR POPULATION AND STAR FORMATION RATES OF z Almost-Equal-To 1.5-1.6 [O II]-EMITTING GALAXIES SELECTED FROM NARROWBAND EMISSION-LINE SURVEYS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ly, Chun; Malkan, Matthew A.; Ross, Nathaniel R.

    We present the first detailed study of the stellar populations of star-forming galaxies at z {approx} 1.5, which are selected by their [O II] emission line, detected in narrowband surveys. We identified {approx}1300 [O II] emitters at z = 1.47 and z = 1.62 in the Subaru Deep Field with rest-frame equivalent widths (EWs) above 13 A. Optical and near-infrared spectroscopic observations for Almost-Equal-To 10% of our samples show that our separation of [O II] from [O III] emission-line galaxies in two-color space is 99% successful. We analyze the multi-wavelength properties of a subset of {approx}1200 galaxies with the bestmore » photometry. They have average rest-frame EW of 45 A, stellar mass of 3 Multiplication-Sign 10{sup 9} M{sub Sun }, and stellar age of 100 Myr. In addition, our spectral energy distribution (SED) fitting and broadband colors indicate that [O II] emitters span the full range of galaxy populations at z {approx} 1.5. We also find that 80% of [O II] emitters are also photometrically classified as 'BX/BM' (UV) galaxies and/or the star-forming 'BzK' (near-IR) galaxies. Our [O II] emission line survey produces a far more complete and somewhat deeper sample of z {approx} 1.5 galaxies than either the BX/BM or sBzK selection alone. We constructed average SEDs and find that higher [O II] EW galaxies have somewhat bluer continua. SED model-fitting shows that they have on average half the stellar mass of galaxies with lower [O II] EW. The observed [O II] luminosity is well correlated with the far-UV continuum with a logarithmic slope of 0.89 {+-} 0.22. The scatter of the [O II] luminosity against the far-UV continuum suggests that [O II] can be used as a star formation rate indicator with a reliability of 0.23 dex.« less

  15. The Extremely Metal-Poor Dwarf Galaxy AGC 198691

    NASA Astrophysics Data System (ADS)

    Hirschauer, Alec S.; Salzer, John Joseph; Cannon, John M.; Skillman, Evan D.; SHIELD II Team

    2016-01-01

    We present spectroscopic observations of the nearby dwarf irregular galaxy AGC 198691. This object is part of the Survey of HI in Extremely Low-Mass Dwarfs (SHIELD) sample, which consists of ultra-low HI mass galaxies discovered by the Arecibo Legacy Fast-Acting ALFA (ALFALFA) survey. SHIELD is a multi-configuration Expanded Very Large Array (EVLA) study of the neutral gas content and dynamics of galaxies with HI masses in the range of 106-107 M⊙. Our spectral data were obtained using the new high-throughput KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m telescope as part of a systematic study of the nebular abundances in the SHIELD galaxy sample. These observations enable measurement of the temperature sensitive [OIII]λ4363 line and hence the determination of a "direct" oxygen abundance for AGC 198691. We find this system to be an extremely metal-deficient (XMD) galaxy with an oxygen abundance comparable to such objects as I Zw 18, SBS 0335-052W, Leo P, and DDO 68 - the lowest metallicity star-forming systems known. It is worth noting that two of the five lowest-abundance galaxies currently recognized were discovered via the ALFALFA blind HI survey. These XMD galaxies are potential analogues to the first star-forming systems, which through hierarchical accretion processes built up the large galaxies we observe today in the local Universe. Detailed analysis of such XMD systems offers observational constraint to models of galactic evolution and star formation histories to allow a better understanding of the processes that govern the chemical evolution of low-mass galaxies.

  16. Shocked POststarbust Galaxy Survey. I. Candidate Post-starbust Galaxies with Emission Line Ratios Consistent with Shocks

    NASA Astrophysics Data System (ADS)

    Alatalo, Katherine; Cales, Sabrina L.; Rich, Jeffrey A.; Appleton, Philip N.; Kewley, Lisa J.; Lacy, Mark; Lanz, Lauranne; Medling, Anne M.; Nyland, Kristina

    2016-06-01

    There are many mechanisms by which galaxies can transform from blue, star-forming spirals, to red, quiescent early-type galaxies, but our current census of them does not form a complete picture. Recent observations of nearby case studies have identified a population of galaxies that quench “quietly.” Traditional poststarburst searches seem to catch galaxies only after they have quenched and transformed, and thus miss any objects with additional ionization mechanisms exciting the remaining gas. The Shocked POststarburst Galaxy Survey (SPOGS) aims to identify transforming galaxies, in which the nebular lines are excited via shocks instead of through star formation processes. Utilizing the Oh-Sarzi-Schawinski-Yi (OSSY) measurements on the Sloan Digital Sky Survey Data Release 7 catalog, we applied Balmer absorption and shock boundary criteria to identify 1067 SPOG candidates (SPOGs*) within z = 0.2. SPOGs* represent 0.2% of the OSSY sample galaxies that exceed the continuum signal-to-noise cut (and 0.7% of the emission line galaxy sample). SPOGs* colors suggest that they are in an earlier phase of transition than OSSY galaxies that meet an “E+A” selection. SPOGs* have a 13% 1.4 GHz detection rate from the Faint Images of the Radio Sky at Twenty Centimeters Survey, higher than most other subsamples, and comparable only to low-ionization nuclear emission line region hosts, suggestive of the presence of active galactic nuclei (AGNs). SPOGs* also have stronger Na I D absorption than predicted from the stellar population, suggestive of cool gas being driven out in galactic winds. It appears that SPOGs* represent an earlier phase in galaxy transformation than traditionally selected poststarburst galaxies, and that a large proportion of SPOGs* also have properties consistent with disruption of their interstellar media, a key component to galaxy transformation. It is likely that many of the known pathways to transformation undergo a SPOG phase. Studying this sample of

  17. The Lyα properties of faint galaxies at z ∼ 2-3 with systemic redshifts and velocity dispersions from Keck-MOSFIRE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Erb, Dawn K.; Steidel, Charles C.; Trainor, Ryan F.

    2014-11-01

    We study the Lyα profiles of 36 spectroscopically detected Lyα-emitters (LAEs) at z ∼ 2-3, using Keck MOSFIRE to measure systemic redshifts and velocity dispersions from rest-frame optical nebular emission lines. The sample has a median optical magnitude R=26.0, and ranges from R≃23 to R>27, corresponding to rest-frame UV absolute magnitudes M {sub UV} ≅ –22 to M {sub UV} > –18.2. Dynamical masses range from M {sub dyn} < 1.3 × 10{sup 8} M {sub ☉} to M {sub dyn} = 6.8 × 10{sup 9} M {sub ☉}, with a median value of M {sub dyn} = 6.3 ×more » 10{sup 8} M {sub ☉}. Thirty of the 36 Lyα emission lines are redshifted with respect to the systemic velocity with at least 1σ significance, and the velocity offset with respect to systemic Δv {sub Lyα} is correlated with the R-band magnitude, M {sub UV}, and the velocity dispersion measured from nebular emission lines with >3σ significance: brighter galaxies with larger velocity dispersions tend to have larger values of Δv {sub Lyα}. We also make use of a comparison sample of 122 UV-color-selected R<25.5 galaxies at z ∼ 2, all with Lyα emission and systemic redshifts measured from nebular emission lines. Using the combined LAE and comparison samples for a total of 158 individual galaxies, we find that Δv {sub Lyα} is anti-correlated with the Lyα equivalent width with 7σ significance. Our results are consistent with a scenario in which the Lyα profile is determined primarily by the properties of the gas near the systemic redshift; in such a scenario, the opacity to Lyα photons in lower mass galaxies may be reduced if large gaseous disks have not yet developed and if the gas is ionized by the harder spectrum of young, low metallicity stars.« less

  18. ON THE COMPACT H II GALAXY UM 408 AS SEEN BY GMOS-IFU: PHYSICAL CONDITIONS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lagos, Patricio; Telles, Eduardo; Munoz-Tunon, Casiana

    2009-06-15

    We present Integral Field Unit GMOS-IFU data of the compact H II galaxy UM 408, obtained at the Gemini South telescope, in order to derive the spatial distribution of emission lines and line ratios, kinematics, plasma parameters, and oxygen abundances as well the integrated properties over an area of 3''x4.''4 equivalent with {approx}750 pc x 1100 pc located in the central part of the galaxy. The starburst in this area is resolved into two giant regions of about 1.''5 and 1'' ({approx}375 and {approx}250 pc) diameter, respectively and separated 1.5-2'' ({approx}500 pc). The extinction distribution concentrate its highest values closemore » but not coincident with the maxima of H{alpha} emission around each one of the detected regions. This indicates that the dust has been displaced from the exciting clusters by the action of their stellar winds. The ages of these two regions, estimated using H{beta} equivalent widths, suggest that they are coeval events of {approx}5 Myr with stellar masses of {approx}10{sup 4} M {sub sun}. We have also used [O III]/H{beta} and [S II]/H{alpha} ratio maps to explore the excitation mechanisms in this galaxy. Comparing the data points with theoretical diagnostic models, we found that all of them are consistent with excitation by photoionization by massive stars. The H{alpha} emission line was used to measure the radial velocity and velocity dispersion. The heliocentric radial velocity shows an apparent systemic motion where the east part of the galaxy is blueshifted, while the west part is redshifted, with a relative motion of {approx}10 km s{sup -1}. The velocity dispersion map shows supersonic values typical for extragalactic H II regions. We derived an integrated oxygen abundance of 12+log(O/H) = 7.87 summing over all spaxels in our field of view. An average value of 12+log(O/H) = 7.77 and a difference of {delta}(O/H) = 0.47 between the minimum and maximum values (7.58 {+-} 0.06-8.05 {+-} 0.04) were found, considering all data

  19. A massive, quiescent, population II galaxy at a redshift of 2.1.

    PubMed

    Kriek, Mariska; Conroy, Charlie; van Dokkum, Pieter G; Shapley, Alice E; Choi, Jieun; Reddy, Naveen A; Siana, Brian; van de Voort, Freeke; Coil, Alison L; Mobasher, Bahram

    2016-12-07

    Unlike spiral galaxies such as the Milky Way, the majority of the stars in massive elliptical galaxies were formed in a short period early in the history of the Universe. The duration of this formation period can be measured using the ratio of magnesium to iron abundance ([Mg/Fe]) in spectra, which reflects the relative enrichment by core-collapse and type Ia supernovae. For local galaxies, [Mg/Fe] probes the combined formation history of all stars currently in the galaxy, including younger and metal-poor stars that were added during late-time mergers. Therefore, to directly constrain the initial star-formation period, we must study galaxies at earlier epochs. The most distant galaxy for which [Mg/Fe] had previously been measured is at a redshift of z ≈ 1.4, with [Mg/Fe] = . A slightly earlier epoch (z ≈ 1.6) was probed by combining the spectra of 24 massive quiescent galaxies, yielding an average [Mg/Fe] = 0.31 ± 0.12 (ref. 7). However, the relatively low signal-to-noise ratio of the data and the use of index analysis techniques for both of these studies resulted in measurement errors that are too large to allow us to form strong conclusions. Deeper spectra at even earlier epochs in combination with analysis techniques based on full spectral fitting are required to precisely measure the abundance pattern shortly after the major star-forming phase (z > 2). Here we report a measurement of [Mg/Fe] for a massive quiescent galaxy at a redshift of z = 2.1, when the Universe was three billion years old. With [Mg/Fe] = 0.59 ± 0.11, this galaxy is the most Mg-enhanced massive galaxy found so far, having twice the Mg enhancement of similar-mass galaxies today. The abundance pattern of the galaxy is consistent with enrichment exclusively by core-collapse supernovae and with a star-formation timescale of 0.1 to 0.5 billion years-characteristics that are similar to population II stars in the Milky Way. With an average past star

  20. On The gamma-ray emission from Reticulum II and other dwarf galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hooper, Dan; Linden, Tim

    2015-09-01

    The recent discovery of ten new dwarf galaxy candidates by the Dark Energy Survey (DES) and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) could increase the Fermi Gamma-Ray Space Telescope's sensitivity to annihilating dark matter particles, potentially enabling a definitive test of the dark matter interpretation of the long-standing Galactic Center gamma-ray excess. In this paper, we compare the previous analyses of Fermi data from the directions of the new dwarf candidates (including the relatively nearby Reticulum II) and perform our own analysis, with the goal of establishing the statistical significance of any gamma-ray signal from these sources.more » We confirm the presence of an excess from Reticulum II, with a spectral shape that is compatible with the Galactic Center signal. The significance of this emission is greater than that observed from 99.84% of randomly chosen high-latitude blank-sky locations, corresponding to a local detection significance of 3.2σ. We caution that any dark matter interpretation of this excess must be validated through observations of additional dwarf spheroidal galaxies, and improved calculations of the relative J-factor of dwarf spheroidal galaxies. We improve upon the standard blank-sky calibration approach through the use of multi-wavelength catalogs, which allow us to avoid regions that are likely to contain unresolved gamma-ray sources.« less

  1. Deep infrared galaxies

    NASA Technical Reports Server (NTRS)

    Ashby, Matthew; Houck, J. R.; Hacking, Perry B.

    1992-01-01

    High signal-to-noise ratio optical spectra of 17 infrared-bright emission-line galaxies near the north ecliptic pole are presented. Reddening-corrected line ratios forbidden O III 5007/H-beta, N II 6583/H-alpha, S II (6716 + 6731)/H-alpha, and O I 6300/H-alpha are used to discriminate between candidate energy generation mechanisms in each galaxy. These criteria have frequently been applied to optically selected samples of galaxies in the past, but this is the first time they have been applied to a set of faint flux-limited infrared-selected objects. The analysis indicates the sample contains seven starburst galaxies and three (AGN). However, seven galaxies in the present sample elude the classification scheme based on these line ratios. It is concluded that a two-component (starburst plus AGN) model for energy generation is inadequate for infrared galaxies.

  2. The Near-Infrared Ca II Triplet-σ Relation for Bulges of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Falcón-Barroso, Jesús; Peletier, Reynier F.; Vazdekis, Alexandre; Balcells, Marc

    2003-05-01

    We present measurements of the near-infrared Ca II triplet (CaT, CaT*), Paschen (PaT), and magnesium (Mg I) indices for a well-studied sample of 19 bulges of early to intermediate spiral galaxies. We find that both the CaT* and CaT indices decrease with central velocity dispersion σ with small scatter. This dependence is similar to that recently found by Cenarro for elliptical galaxies, implying a uniform CaT*-σ relation that applies to galaxies from ellipticals to intermediate-type spirals. The decrease of CaT and CaT* with σ contrasts with the well-known increase of another α-element index, Mg2, with σ. We discuss the role of Ca underabundance ([Ca/Fe]<0) and initial mass function variations in the onset of the observed relations.

  3. Star formation history and chemical enrichment in the early Universe: clues from the rest-optical and rest-UV spectra of z~2-3 star-forming galaxies in the Keck Baryonic Structure Survey

    NASA Astrophysics Data System (ADS)

    Strom, Allison L.

    2017-01-01

    Galaxies at the peak of cosmic star formation (z~2-3) exhibit significantly higher star formation rates and gas fractions at fixed stellar mass than nearby galaxies. These z~2-3 galaxies are also distinct in terms of their nebular spectra, reflecting important differences not only in the physical conditions of their interstellar medium (e.g., electron density and gas-phase metallicity), but also in the details of their massive stellar populations, especially their ionizing radiation fields. Jointly observing galaxies' HII regions, at rest-UV and rest-optical wavelengths, and massive stars, at rest-UV wavelengths, is central to constructing a framework for understanding the differences between z~2-3 and z~0 star-forming galaxies and for self-consistently explaining the trends observed in the high-redshift population. My thesis is based on data from the Keck Baryonic Structure Survey (KBSS), which uniquely combines observations of individual galaxies in these two bandpasses. In total, the near-infrared component of the KBSS includes spectra of >700 z~2-3 galaxies obtained with Keck/MOSFIRE. I will present these results along with a detailed analysis of the full rest-optical (3600-7000 Ang) nebular spectra of ~400 galaxies, showing that high-redshift galaxies exhibit uniformly high degrees of ionization and excitation with respect to most z~0 galaxies. Combined with observations of the same galaxies' rest-UV spectra (obtained with Keck/LRIS) and photoionization model predictions, these results suggest that the disparity arises from differences in the shape of the ionizing radiation field at fixed gas-phase oxygen abundance, most likely due to the effects of Fe-poor massive binary stars. My comprehensive spectroscopic study of an unprecedentedly large sample of z~2-3 galaxies offers compelling evidence that the distinct chemical abundance patterns observed in these galaxies are the result of systematic differences in their star formation histories.

  4. The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA

    NASA Astrophysics Data System (ADS)

    Bolatto, Alberto D.; Wong, Tony; Utomo, Dyas; Blitz, Leo; Vogel, Stuart N.; Sánchez, Sebastián F.; Barrera-Ballesteros, Jorge; Cao, Yixian; Colombo, Dario; Dannerbauer, Helmut; García-Benito, Rubén; Herrera-Camus, Rodrigo; Husemann, Bernd; Kalinova, Veselina; Leroy, Adam K.; Leung, Gigi; Levy, Rebecca C.; Mast, Damián; Ostriker, Eve; Rosolowsky, Erik; Sandstrom, Karin M.; Teuben, Peter; van de Ven, Glenn; Walter, Fabian

    2017-09-01

    We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3σ sensitivity {{{Σ }}}{mol}˜ 11 {M}⊙ {{pc}}-2 before inclination correction, resolution ˜1.4 kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.

  5. SDSS-II SUPERNOVA SURVEY: AN ANALYSIS OF THE LARGEST SAMPLE OF TYPE IA SUPERNOVAE AND CORRELATIONS WITH HOST-GALAXY SPECTRAL PROPERTIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wolf, Rachel C.; Gupta, Ravi R.; Sako, Masao

    2016-04-20

    Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HRs). Our sample consists of 345 photometrically classified or spectroscopically confirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric host-galaxy properties frommore » the SDSS-SNS data release such as host stellar mass and star formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6 σ significance of a nonzero linear slope. We also recover correlations between HR and host-galaxy gas-phase metallicity and specific star formation rate as they are reported in the literature. With our large data set, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically confirmed and photometrically classified SNe Ia and comment on the significance of similar combined data sets for future surveys.« less

  6. Non-equilibrium effects on the chemistry of nebular condensates - Implications for the planets and asteroids

    NASA Technical Reports Server (NTRS)

    Blander, M.

    1979-01-01

    Kinetic effects, for example nucleation constraints and slow reactions, should have been important in nebular condensation. Consideration of these effects leads to the prediction of pressure-dependent compositions and physical properties of nebular condensates which is consistent with (1) the differences between different classes of chondritic meteorites, (2) some of the differences between planets, and (3) the presence of oxidized iron on the moon and in the eucrite parent body (presumably an asteroid) despite the low abundance of volatiles. Diffusion effects appear to be important for understanding oxygen isotope anomalies in refractory inclusions in Allende. The consideration of kinetic effects leads to more information concerning nebular processes than if equilibrium is assumed.

  7. Peas in a Pod: Environment and Ionization in Green Pea Galaxies

    NASA Astrophysics Data System (ADS)

    Kurtz, Heather; Jaskot, Anne; Drew, Patrick; Pare, Dylan; Griffin, Jon; Petersen, Michael

    2016-01-01

    The Green Peas are extreme, highly ionized, starburst galaxies with strong [OIII] 5007 emission. Using the Sloan Digital Sky Survey, we present statistics on the environment of Green Peas and investigate its effects on their ionized gas properties. Although most dwarf starburst galaxies are in low-density environments, we identify a sample of Green Peas in dense environments. Emission line observations with the WIYN 0.9-meter telescope at Kitt Peak reveal that one cluster Green Pea is more highly ionized in the direction of the cluster center. Ram pressure stripping likely generates this ionization gradient. We explore the role of the environment in enhancing star formation rates and ionization, and we compare the nebular properties of Green Peas in high-density environments to those in low-density environments.

  8. Dust Emission at 8 and 24 μ m as Diagnostics of H ii Region Radiative Transfer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Oey, M. S.; López-Hernández, J.; Kellar, J. A.

    We use the Spitzer Surveying the Agents of Galaxy Evolution (SAGE) survey of the Magellanic Clouds to evaluate the relationship between the 8 μ m polycyclic aromatic hydrocarbon (PAH) emission, 24 μ m hot dust emission, and H ii region radiative transfer. We confirm that in the higher-metallicity Large Magellanic Cloud, PAH destruction is sensitive to optically thin conditions in the nebular Lyman continuum: objects identified as optically thin candidates based on nebular ionization structure show six times lower median 8 μ m surface brightness (0.18 mJy arcsec{sup −2}) than their optically thick counterparts (1.2 mJy arcsec{sup −2}). The 24more » μ m surface brightness also shows a factor of three offset between the two classes of objects (0.13 versus 0.44 mJy arcsec{sup −2}, respectively), which is driven by the association between the very small dust grains and higher density gas found at higher nebular optical depths. In contrast, PAH and dust formation in the low-metallicity Small Magellanic Cloud is strongly inhibited such that we find no variation in either 8 μ m or 24 μ m emission between our optically thick and thin samples. This is attributable to extremely low PAH and dust production together with high, corrosive UV photon fluxes in this low-metallicity environment. The dust mass surface densities and gas-to-dust ratios determined from dust maps using Herschel HERITAGE survey data support this interpretation.« less

  9. Ultrahigh-energy Cosmic Rays from Fanaroff Riley class II radio galaxies

    NASA Astrophysics Data System (ADS)

    Rachen, Joerg; Biermann, Peter L.

    1992-08-01

    The hot spots of very powerful radio galaxies (Fanaroff Riley class II) are argued to be the sources of the ultrahigh energy component in Cosmic Rays. We present calculations of Cosmic Ray transport in an evolving universe, taking the losses against the microwave background properly into account. As input we use the models for the cosmological radio source evolution derived by radioastronomers (mainly Peacock 1985). The model we adopt for the acceleration in the radio hot spots has been introduced by Biermann and Strittmatter (1987), and Meisenheimer et al. (1989) and is based on first order Fermi theory of particle acceleration at shocks (see, e.g., Drury 1983). As an unknown the actual proportion of energy density in protons enters, which together with structural uncertainties in the hot spots should introduce no more than one order of magnitude in uncertainty: We easily reproduce the observed spectra of high energy cosmic rays. It follows that scattering of charged energetic particles in intergalactic space must be sufficiently small in order to obtain contributions from sources as far away as even the nearest Fanaroff Riley class II radio galaxies. This implies a strong constraint on the turbulent magnetic field in intergalactic space.

  10. Stellar Populations of Lyα Emitters at z ~ 6-7: Constraints on the Escape Fraction of Ionizing Photons from Galaxy Building Blocks

    NASA Astrophysics Data System (ADS)

    Ono, Yoshiaki; Ouchi, Masami; Shimasaku, Kazuhiro; Dunlop, James; Farrah, Duncan; McLure, Ross; Okamura, Sadanori

    2010-12-01

    We investigate the stellar populations of Lyα emitters (LAEs) at z = 5.7 and 6.6 in a 0.65 deg2 sky of the Subaru/XMM-Newton Deep Survey (SXDS) Field, using deep images taken with the Subaru/Suprime-Cam, United Kingdom Infrared Telescope/Wide Field Infrared Camera, and Spitzer/Infrared Array Camera (IRAC). We produce stacked multiband images at each redshift from 165 (z = 5.7) and 91 (z = 6.6) IRAC-undetected objects to derive typical spectral energy distributions (SEDs) of z ~ 6-7 LAEs for the first time. The stacked LAEs have as blue UV continua as the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) z-dropout galaxies of similar M UV, with a spectral slope β ~ -3, but at the same time they have red UV-to-optical colors with detection in the 3.6 μm band. Using SED fitting we find that the stacked LAEs have low stellar masses of ~(3-10) × 107 M sun, very young ages of ~1-3 Myr, negligible dust extinction, and strong nebular emission from the ionized interstellar medium, although the z = 6.6 object is fitted similarly well with high-mass models without nebular emission; inclusion of nebular emission reproduces the red UV-to-optical colors while keeping the UV colors sufficiently blue. We infer that typical LAEs at z ~ 6-7 are building blocks of galaxies seen at lower redshifts. We find a tentative decrease in the Lyα escape fraction from z = 5.7 to 6.6, which may imply an increase in the intergalactic medium neutral fraction. From the minimum contribution of nebular emission required to fit the observed SEDs, we place an upper limit on the escape fraction of ionizing photons of f ion esc ~ 0.6 at z = 5.7 and ~0.9 at z = 6.6. We also compare the stellar populations of our LAEs with those of stacked HST/WFC3 z-dropout galaxies. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  11. Analogues of primeval galaxies two billion years after the Big Bang

    NASA Astrophysics Data System (ADS)

    Amorín, Ricardo; Fontana, Adriano; Pérez-Montero, Enrique; Castellano, Marco; Guaita, Lucia; Grazian, Andrea; Le Fèvre, Olivier; Ribeiro, Bruno; Schaerer, Daniel; Tasca, Lidia A. M.; Thomas, Romain; Bardelli, Sandro; Cassarà, Letizia; Cassata, Paolo; Cimatti, Andrea; Contini, Thierry; de Barros, Stephane; Garilli, Bianca; Giavalisco, Mauro; Hathi, Nimish; Koekemoer, Anton; Le Brun, Vincent; Lemaux, Brian C.; Maccagni, Dario; Pentericci, Laura; Pforr, Janine; Talia, Margherita; Tresse, Laurence; Vanzella, Eros; Vergani, Daniela; Zamorani, Giovanni; Zucca, Elena; Merlin, Emiliano

    2017-03-01

    Deep observations are revealing a growing number of young galaxies in the first billion years of cosmic time1. Compared to typical galaxies at later times, they show more extreme emission-line properties2, higher star formation rates3, lower masses4, and smaller sizes5. However, their faintness precludes studies of their chemical abundances and ionization conditions, strongly limiting our understanding of the physics driving early galaxy build-up and metal enrichment. Here we study a rare population of ultraviolet-selected, low-luminosity galaxies at redshift 2.4 < z < 3.5 that exhibit all the rest-frame properties expected from primeval galaxies. These low-mass, highly compact systems are rapidly forming galaxies able to double their stellar mass in only a few tens of millions of years. They are characterized by very blue ultraviolet spectra with weak absorption features and bright nebular emission lines, which imply hard radiation fields from young hot massive stars6,7. Their highly ionized gas phase has strongly sub-solar carbon and oxygen abundances, with metallicities more than a factor of two lower than that found in typical galaxies of similar mass and star formation rate at z≤2.58. These young galaxies reveal an early and short stage in the assembly of their galactic structures and their chemical evolution, a vigorous phase that is likely to be dominated by the effects of gas-rich mergers, accretion of metal-poor gas and strong outflows.

  12. A Wide Area Survey for High-Redshift Massive Galaxies. II. Near-Infrared Spectroscopy of BzK-Selected Massive Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Onodera, Masato; Arimoto, Nobuo; Daddi, Emanuele; Renzini, Alvio; Kong, Xu; Cimatti, Andrea; Broadhurst, Tom; Alexander, Dave M.

    2010-05-01

    Results are presented from near-infrared spectroscopic observations of a sample of BzK-selected, massive star-forming galaxies (sBzKs) at 1.5 < z < 2.3 that were obtained with OHS/CISCO at the Subaru telescope and with SINFONI at the Very Large Telescope. Among the 28 sBzKs observed, Hα emission was detected in 14 objects, and for 11 of them the [N II] λ6583 flux was also measured. Multiwavelength photometry was also used to derive stellar masses and extinction parameters, whereas Hα and [N II] emissions have allowed us to estimate star formation rates (SFRs), metallicities, ionization mechanisms, and dynamical masses. In order to enforce agreement between SFRs from Hα with those derived from rest-frame UV and mid-infrared, additional obscuration for the emission lines (that originate in H II regions) was required compared to the extinction derived from the slope of the UV continuum. We have also derived the stellar mass-metallicity relation, as well as the relation between stellar mass and specific SFR (SSFR), and compared them to the results in other studies. At a given stellar mass, the sBzKs appear to have been already enriched to metallicities close to those of local star-forming galaxies of similar mass. The sBzKs presented here tend to have higher metallicities compared to those of UV-selected galaxies, indicating that near-infrared selected galaxies tend to be a chemically more evolved population. The sBzKs show SSFRs that are systematically higher, by up to ~2 orders of magnitude, compared to those of local galaxies of the same mass. The empirical correlations between stellar mass and metallicity, and stellar mass and SSFR are then compared with those of evolutionary population synthesis models constructed either with the simple closed-box assumption, or within an infall scenario. Within the assumptions that are built-in such models, it appears that a short timescale for the star formation (sime100 Myr) and large initial gas mass appear to be required

  13. Lyα emitters in the GOODS-S field. A powerful pure nebular SED with N IV] emission at z = 5.563

    NASA Astrophysics Data System (ADS)

    Raiter, A.; Fosbury, R. A. E.; Teimoorinia, H.

    2010-02-01

    Context. The Great Observatories Origins Deep Survey (GOODS) has provided us with one of the deepest multi-wavelength views of the distant universe. The combination of multi-band photometry and optical spectroscopy has resulted in the identification of sources whose redshifts extend to values in excess of six. Amongst these distant sources are Lyα emitters whose nature must be deduced by clearly identifying the different components that contribute to the measured SED. Aims: From a sample of Lyα emitters in the GOODS-S field with uncontaminated photometry and optical (red) spectroscopy, we select a spatially compact object at a redshift of 5.563 (Lyα) that shows a second emission line, identified as N IV] 1486 Å. The SED is modelled in a way that accounts for both the N IV] line emission and the photometry in a self-consistent way. Methods: The photoionization code CLOUDY is used to calculate a range of nebular models as a function of stellar ionizing source temperature, ionization parameter, density and nebular metallicity. We compare the theoretical and observed magnitudes and search for the model parameters that also reproduce the observed N IV] luminosity and equivalent width. Results: A nebular model with a hot blackbody ionizing source of around 100 kK and a nebular metallicity of ~5% of solar is able to fit the observed SED and, in particular, explain the large apparent Balmer break which is inferred from the pure stellar population model fitting conventionally applied to multi-band photometric observations. In our model, an apparent spectral break is produced by strong [O III] 4959, 5007 Å emission falling in one of the IR bands (IRAC1 in this case). A lower limit on the total baryonic mass of a model of this type is 3.2 ×10^8~M⊙. Conclusions: It is argued that objects with Lyα emission at high redshift that show an apparent Balmer break may have their SED dominated by nebular emission and so could possibly be identified with very young starbursting

  14. A gravitationally lensed starburst galaxy at z=1.03 detected by SOFIA/HAWC+

    NASA Astrophysics Data System (ADS)

    Brown, Arianna; Ma, Jingzhe; Cooray, Asantha; Nayyeri, Hooshang; Timmons, Nicholas

    2018-01-01

    We present a high S/N~20 detection at 89 micron (in 15 mins) of the Herschel-selected gravitationally lensed starburst galaxy HATLASJ1429-0028 with the High-resolution Airborne Wideband Camera-plus (HAWC+) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The spectacular lensing system consists of an edge-on foreground disk galaxy at z=0.22 and a nearly complete Einstein ring of an intrinsic ultra-luminous infrared galaxy at z=1.03. Is this high luminosity powered by pure star formation (SF) or an active galactic nucleus (AGN)? Previous nebular line diagnostics indicate that it is star-formation dominated. SOFIA/HAWC+ allows the broad-band spectral energy distribution of the galaxy to be studied between 20 - 100 micron, which is an important wavelength range for further constraining the fractional AGN contribution to the total IR luminosity. Multi-wavelength SED modeling constrains the AGN fraction to be < 1%. The detection of a source at z of 1 shows the potential of utilizing SOFIA/HAWC+ for distant galaxy studies and the potential to decompose SF/AGN that cannot be obtained with other current facilities.

  15. Properties of the giant H II regions and bar in the nearby spiral galaxy NGC 5430

    NASA Astrophysics Data System (ADS)

    Brière, É.; Cantin, S.; Spekkens, K.

    2012-09-01

    In order to better understand the impact of the bar on the evolution of spiral galaxies, we measure the properties of giant H II regions and the bar in the SB(s)b galaxy NGC 5430. We use two complementary data sets, both obtained at the Observatoire du Mont-Mégantic: a hyperspectral data cube from the imaging Fourier transform spectrograph SpIOMM (Spectromètre-Imageur à transformée de Fourier de l-Observatoire du Mont-Mégantic) and high-resolution spectra across the bar from a long-slit spectrograph. We flux-calibrate SpIOMM spectra for the first time, and produce Hα and [N II]λ6584 Å intensity maps from which we identify 51 giant H II regions in the spiral arms and bar. We evaluate the type of activity, the oxygen abundance and the age of the young populations contained in these giant H II regions and in the bar. Thus, we confirm that NGC 5430 does not harbour a strong active galactic nucleus, and that its Wolf-Rayet knot shows a pure H II region nature. We find no variation in abundance or age between the bar and spiral arms, nor as a function of galactocentric radius. These results are consistent with the hypothesis that a chemical mixing mechanism is at work in the galaxy's disc to flatten the oxygen abundance gradient. Using the STARBURST99 model, we estimate the ages of the young populations, and again find no variations in age between the bar and the arms or as a function of radius. Instead, we find evidence for two galaxy-wide waves of star formation, about 7.1 and 10.5 Myr ago. While the bar in NGC 5430 is an obvious candidate to trigger these two episodes, it is not clear how the bar could induce widespread star formation on such a short time-scale.

  16. Dynamics of Galaxies in Compact Groups II.

    NASA Astrophysics Data System (ADS)

    Amram, P.; Mendes de Oliveira, C.

    We show partial results of a program based on Fabry-Perot Hα velocity field data of compact groups taken at the ESO and the CFH 3.6m telescopes in order to analyze the kinematics of compact group galaxies. This project has three main goals: 1. determine the evolutionary stages of the groups; 2. search for tidal dwarf galaxies and 3. determine the Tully-Fisher relation for the group galaxies. We classify the compact groups studied so far into the following subclasses : (1) merging groups, (2) strongly interacting, (3) mildly interacting, (4) kinematically undisturbed and (5) false groups/single galaxy (details are given in the companion paper Mendes de Oliveira and Amram, 2000). We present examples of velocity fields of galaxies in compact groups that are in different evolutionary stages as classified from the kinematic disturbances. Spiral-only groups have often been considered chance alignments or groups in the very early stages of dynamical evolution. However, we find that the kinematics of the member galaxies for spiral-only groups in classes (1), (2) and (3) above display peculiarities which suggest that the galaxies know of the presence of their neighbors.

  17. Polar ring galaxies in the Galaxy Zoo

    NASA Astrophysics Data System (ADS)

    Finkelman, Ido; Funes, José G.; Brosch, Noah

    2012-05-01

    We report observations of 16 candidate polar-ring galaxies (PRGs) identified by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) data base. Deep images of five galaxies are available in the SDSS Stripe82 data base, while to reach similar depth we observed the remaining galaxies with the 1.8-m Vatican Advanced Technology Telescope. We derive integrated magnitudes and u-r colours for the host and ring components and show continuum-subtracted Hα+[N II] images for seven objects. We present a basic morphological and environmental analysis of the galaxies and discuss their properties in comparison with other types of early-type galaxies. Follow-up photometric and spectroscopic observations will allow a kinematic confirmation of the nature of these systems and a more detailed analysis of their stellar populations.

  18. Empirical Modeling of the Redshift Evolution of the [{\\rm{N}}\\,{\\rm{II}}]/Hα Ratio for Galaxy Redshift Surveys

    NASA Astrophysics Data System (ADS)

    Faisst, Andreas L.; Masters, Daniel; Wang, Yun; Merson, Alexander; Capak, Peter; Malhotra, Sangeeta; Rhoads, James E.

    2018-03-01

    We present an empirical parameterization of the [N II]/Hα flux ratio as a function of stellar mass and redshift valid at 0 < z < 2.7 and 8.5< {log}(M/{M}ȯ )< 11.0. This description can (i) easily be applied to simulations for modeling [N II]λ6584 line emission, (ii) deblend [N II] and Hα in current low-resolution grism and narrow-band observations to derive intrinsic Hα fluxes, and (iii) reliably forecast the number counts of Hα emission-line galaxies for future surveys, such as those planned for Euclid and the Wide Field Infrared Survey Telescope (WFIRST). Our model combines the evolution of the locus on the Baldwin, Phillips & Terlevich (BPT) diagram measured in spectroscopic data out to z ∼ 2.5 with the strong dependence of [N II]/Hα on stellar mass and [O III]/Hβ observed in local galaxy samples. We find large variations in the [N II]/Hα flux ratio at a fixed redshift due to its dependency on stellar mass; hence, the assumption of a constant [N II] flux contamination fraction can lead to a significant under- or overestimate of Hα luminosities. Specifically, measurements of the intrinsic Hα luminosity function derived from current low-resolution grism spectroscopy assuming a constant 29% contamination of [N II] can be overestimated by factors of ∼8 at {log}(L)> 43.0 for galaxies at redshifts z ∼ 1.5. This has implications for the prediction of Hα emitters for Euclid and WFIRST. We also study the impact of blended Hα and [N II] on the accuracy of measured spectroscopic redshifts.

  19. THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zackrisson, Erik; Rydberg, Claes-Erik; Oestlin, Goeran

    The James Webb Space Telescope (JWST) is expected to revolutionize our understanding of the high-redshift universe, and may be able to test the prediction that the first, chemically pristine (Population III) stars are formed with very high characteristic masses. Since isolated Population III stars are likely to be beyond the reach of JWST, small Population III galaxies may offer the best prospects of directly probing the properties of metal-free stars. Here, we present Yggdrasil, a new spectral synthesis code geared toward the first galaxies. Using this model, we explore the JWST imaging detection limits for Population III galaxies and investigatemore » to what extent such objects may be identified based on their JWST colors. We predict that JWST should be able to detect Population III galaxies with stellar population masses as low as {approx}10{sup 5} M{sub sun} at z {approx} 10 in ultra deep exposures. Over limited redshift intervals, it may also be possible to use color criteria to select Population III galaxy candidates for follow-up spectroscopy. The colors of young Population III galaxies dominated by direct starlight can be used to probe the stellar initial mass function (IMF), but this requires almost complete leakage of ionizing photons into the intergalactic medium. The colors of objects dominated by nebular emission show no corresponding IMF sensitivity. We also note that a clean selection of Population III galaxies at z {approx} 7-8 can be achieved by adding two JWST/MIRI filters to the JWST/NIRCam filter sets usually discussed in the context of JWST ultra deep fields.« less

  20. VizieR Online Data Catalog: Galaxy properties in clusters. II. (Muriel+, 2014)

    NASA Astrophysics Data System (ADS)

    Muriel, H.; Coenda, V.

    2014-06-01

    In paper I (Coenda & Muriel, 2009A&A...504..347C, Cat. J/A+A/504/347), we selected an X-ray sample of 49 clusters of galaxies from Popesso et al. (2004A&A...423..449P, Cat. J/A+A/423/449, hereafter P04) in the redshift range 0.05Galaxies in these clusters were identified using the Main Galaxy Sample (MGS; Strauss et al. 2002AJ....124.1810S) of the Fifth Data Release (DR5; Adelman-McCarthy et al. 2007ApJS..172..634A, Cat. II/276) of SDSS, which includes spectroscopic redshifts down to a Petrosian magnitude r=17.77. In this paper, we expand the X-ray cluster sample using the cross-correlation between NORAS and SDSS. We identify a subsample from Bohringer et al. (2000ApJS..129..435B, Cat. J/ApJS/129/435, hereafter B00), which we labelled C-B00-I, using the MGS of the Seventh Data Release (DR7; Abazajian et al. 2009ApJS..182..543A) of SDSS. This subsample comprises 55 galaxy clusters in the redshift range 0.05

  1. Circumstantial Starbirth in Starbursts: Systematic Variations in the Stellar and Nebular Content of Giant HII Regions in the Local Group Galaxy M33

    NASA Astrophysics Data System (ADS)

    Waller, W. H.; Murphy, E. J.; Gherz, R. D.; Polomski, E.; Woodward, C. E.; Fazio, G. G.; Rieke, G. H.; Spitzer/M33 Research Team

    2005-12-01

    From the Orion Nebula to the Hubble Deep Field, starburst activity can be seen transforming galaxian clouds of gas into populous clusters of stars. The pyrotechnics and chemical enrichment associated with this activity have led to outcomes as ubiquitous as interstellar dust and as exquisite as life on Earth. In this talk, I will focus on the circumstances of star formation in the environmental context of ongoing starburst activity. I begin with the premises that (1) the formation of a single star takes time, (2) the formation of a populous cluster takes even more time, and (3) ''stuff'' happens in the interim. Hubble images of the Orion Nebula and Eagle Nebula show how hot stars can excavate neighboring clouds of gas and photoevaporate the star-forming cores that are exposed. Hubble observations of giant HII regions in M33 reveal a significant variation in the stellar populations, such that the most metal-rich HII regions contain the greatest proportions of the most massive stars. ISO and Spitzer observations of these same HII regions reveal corresponding variations in the nebular content. These multi-wavelength diagnostics of the stellar-nebular feedback in galaxian starbursts suggest a star-forming mechanism which is subject to photo-evaporative ablation -- an erosive process that is systematically mediated by the metal abundance and corresponding amounts of protective dust in the starbursting environment.

  2. ALMA [N ii] 205 μ m Imaging Spectroscopy of the Interacting Galaxy System BRI 1202-0725 at Redshift 4.7

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lu, Nanyao; Xu, C. Kevin; Zhu, Lei

    We present the results from Atacama Large Millimeter/submillimeter Array imaging in the [N ii] 205 μ m fine-structure line (hereafter [N ii]) and the underlying continuum of BRI 1202-0725, an interacting galaxy system at z = 4.7, consisting of a quasi-stellar object (QSO), a submillimeter galaxy (SMG), and two Ly α emitters, all within ∼25 kpc of the QSO. We detect the QSO and SMG in both [N ii] and continuum. At the ∼1″ (or 6.6 kpc) resolution, both the QSO and SMG are resolved in [N ii], with the de-convolved major axes of ∼9 and ∼14 kpc, respectively. Inmore » contrast, their continuum emissions are much more compact and unresolved even at an enhanced resolution of ∼0.″7. The ratio of the [N ii] flux to the existing CO(7−6) flux is used to constrain the dust temperature ( T {sub dust}) for a more accurate determination of the FIR luminosity L {sub FIR}. Our best estimated T {sub dust} equals 43 (±2) K for both galaxies (assuming an emissivity index β = 1.8). The resulting L {sub CO(7−6)}/ L {sub FIR} ratios are statistically consistent with that of local luminous infrared galaxies, confirming that L {sub CO(7−6)} traces the star formation (SF) rate (SFR) in these galaxies. We estimate that the ongoing SF of the QSO (SMG) has an SFR of 5.1 (6.9) × 10{sup 3} M {sub ⊙} yr{sup −1} (±30%) assuming Chabrier initial mass function, takes place within a diameter (at half maximum) of 1.3 (1.5) kpc, and will consume the existing 5 (5) × 10{sup 11} M {sub ⊙} of molecular gas in 10 (7) × 10{sup 7} years.« less

  3. The H IX galaxy survey - II. H I kinematics of H I eXtreme galaxies

    NASA Astrophysics Data System (ADS)

    Lutz, K. A.; Kilborn, V. A.; Koribalski, B. S.; Catinella, B.; Józsa, G. I. G.; Wong, O. I.; Stevens, A. R. H.; Obreschkow, D.; Dénes, H.

    2018-05-01

    By analysing a sample of galaxies selected from the H I Parkes All Sky Survey (HIPASS) to contain more than 2.5 times their expected H I content based on their optical properties, we investigate what drives these H I eXtreme (H IX) galaxies to be so H I-rich. We model the H I kinematics with the Tilted Ring Fitting Code TiRiFiC and compare the observed H IX galaxies to a control sample of galaxies from HIPASS as well as simulated galaxies built with the semi-analytic model DARK SAGE. We find that (1) H I discs in H IX galaxies are more likely to be warped and more likely to host H I arms and tails than in the control galaxies, (2) the average H I and average stellar column density of H IX galaxies is comparable to the control sample, (3) H IX galaxies have higher H I and baryonic specific angular momenta than control galaxies, (4) most H IX galaxies live in higher spin haloes than most control galaxies. These results suggest that H IX galaxies are H I-rich because they can support more H I against gravitational instability due to their high specific angular momentum. The majority of the H IX galaxies inherits their high specific angular momentum from their halo. The H I content of H IX galaxies might be further increased by gas-rich minor mergers. This paper is based on data obtained with the Australia Telescope Compact Array through the large program C 2705.

  4. Diffuse ionized gas in galaxies across the Hubble sequence at the CALIFA resolution

    NASA Astrophysics Data System (ADS)

    Lacerda, E. A. D.; Cid Fernandes, R.; Couto, G. S.; Stasińska, G.; García-Benito, R.; Vale Asari, N.; Pérez, E.; Gonzalez Delgado, R. M.; Sánchez, S. F.; de Amorim, A. L.

    2017-11-01

    We use spatially resolved spectroscopy from the CALIFA survey to study the nature of the line emitting gas in galaxies of different Hubble types, focusing on the separation of star-forming (SF) regions from those better characterized as diffuse ionized gas (DIG). The diagnosis is carried out in terms of the equivalent width of Hα (W_{Hα}). Three nebular regimes are identified: Regions where W_{Hα} < 3 Å define what we call the hDIG, the component of the DIG where photoionization is dominated by hot, low mass, evolved stars. Regions where W_{Hα} > 14 Å trace SF complexes. W_{Hα} values in the intermediate 3-14 Å range reflect a mixed regime (mDIG) where more than one process contributes.This three-tier scheme is inspired both by theoretical and empirical considerations. Its application to CALIFA galaxies of different types and inclinations leads to the following results: (i) The hDIG component is prevalent throughout ellipticals and S0's as well as in bulges, and explains the strongly bimodal distribution of W_{{Hα} both among and within galaxies. (ii) Early type spirals have some hDIG in their disks, but this component becomes progressively less relevant for later Hubble types. (iii) hDIG emission is also present above and below galactic disks, as seen in several edge-on spirals in our sample. (iv) The SF/mDIG proportion grows steadily from early to late types spirals, and from inner to outer radii. (v) Besides circumventing basic inconsistencies in conventional DIG/SF separation criteria based on the &Hα surface brightness, our W_{Hα}-based method produces results in agreement with a classical excitation diagram analysis.

  5. Herschel Spectroscopy of the Taffy Galaxies (UGC 12914/12915 = VV 254): Enhanced [C II] Emission in the Collisionally Formed Bridge

    NASA Astrophysics Data System (ADS)

    Peterson, B. W.; Appleton, P. N.; Bitsakis, T.; Guillard, P.; Alatalo, K.; Boulanger, F.; Cluver, M.; Duc, P.-A.; Falgarone, E.; Gallagher, S.; Gao, Y.; Helou, G.; Jarrett, T. H.; Joshi, B.; Lisenfeld, U.; Lu, N.; Ogle, P.; Pineau des Forêts, G.; van der Werf, P.; Xu, C. K.

    2018-03-01

    Using the PACS and SPIRE spectrometers on board Herschel, we obtained observations of the Taffy galaxies (UGC 12914/12915) and bridge. The Taffy system is believed to be the result of a face-on collision between two gas-rich galaxies, in which the stellar disks passed through each other, but the gas was dispersed into a massive H I and molecular bridge between them. Emission is detected and mapped in both galaxies and the bridge in the [C II]157.7 μm and [O I]63.2 μm fine-structure lines. Additionally, SPIRE FTS spectroscopy detects the [C I] {}3{{{P}}}2\\to {}3{{{P}}}1(809.3 {GHz}) and [C I] {}3{{{P}}}1\\to 3{{{P}}}0(492.2 {GHz}) neutral carbon lines, and weakly detects high-J CO transitions in the bridge. These results indicate that the bridge is composed of a warm multi-phase medium consistent with shock and turbulent heating. Despite low star formation rates in the bridge, the [C II] emission appears to be enhanced, reaching [C II]/FIR ratios of 3.3% in parts of the bridge. Both the [C II] and [O I] lines show broad intrinsic multi-component profiles, similar to those seen in previous CO (1–0) and H I observations. The [C II] emission shares similar line profiles with both the double-peaked H I profiles and shares a high-velocity component with single-peaked CO profiles in the bridge, suggesting that the [C II] emission originates in both the neutral and molecular phases. We show that it is feasible that a combination of turbulently heated H2 and high column-density H I, resulting from the galaxy collision, is responsible for the enhanced [C II] emission.

  6. Gemini NIFS survey of feeding and feedback processes in nearby active galaxies - II. The sample and surface mass density profiles

    NASA Astrophysics Data System (ADS)

    Riffel, R. A.; Storchi-Bergmann, T.; Riffel, R.; Davies, R.; Bianchin, M.; Diniz, M. R.; Schönell, A. J.; Burtscher, L.; Crenshaw, M.; Fischer, T. C.; Dahmer-Hahn, L. G.; Dametto, N. Z.; Rosario, D.

    2018-02-01

    We present and characterize a sample of 20 nearby Seyfert galaxies selected for having BAT 14-195 keV luminosities LX ≥ 1041.5 erg s-1, redshift z ≤ 0.015, being accessible for observations with the Gemini Near-Infrared Field Spectrograph (NIFS) and showing extended [O III]λ5007 emission. Our goal is to study Active Galactic Nucleus (AGN) feeding and feedback processes from near-infrared integral-field spectra, which include both ionized (H II) and hot molecular (H2) emission. This sample is complemented by other nine Seyfert galaxies previously observed with NIFS. We show that the host galaxy properties (absolute magnitudes MB, MH, central stellar velocity dispersion and axial ratio) show a similar distribution to those of the 69 BAT AGN. For the 20 galaxies already observed, we present surface mass density (Σ) profiles for H II and H2 in their inner ˜500 pc, showing that H II emission presents a steeper radial gradient than H2. This can be attributed to the different excitation mechanisms: ionization by AGN radiation for H II and heating by X-rays for H2. The mean surface mass densities are in the range (0.2 ≤ ΣH II ≤ 35.9) M⊙ pc-2, and (0.2 ≤ ΣH2 ≤ 13.9)× 10-3 M⊙ pc-2, while the ratios between the H II and H2 masses range between ˜200 and 8000. The sample presented here will be used in future papers to map AGN gas excitation and kinematics, providing a census of the mass inflow and outflow rates and power as well as their relation with the AGN luminosity.

  7. Do stellar and nebular abundances in the Cocoon nebula agree?

    NASA Astrophysics Data System (ADS)

    García-Rojas, J.; Simón-Díaz, S.; Esteban, C.

    2015-05-01

    The Cocoon nebula is an apparently spherical Galactic HII region ionized by a single star (BD+46 3474). This nebula seems to be appropriate to investigate the chemical behavior of oxygen and other heavy elements from two different points of view: a detailed analysis of the chemical content of the ionized gas through nebular spectrophotometry and a detailed spectroscopic analysis of the spectrum of the ionizing star using the state-of-the-art stellar atmosphere modelling. In this poster we present the results from a set of high-quality observations, from 2m-4m class telescopes, including the optical spectrum of the ionizing star BD+46 3474, along with long-slit spatially resolved spectroscopy of the nebula. We have used state-of-the-art stellar atmosphere codes to determine stellar parameters and the chemical content of several heavy elements. Traditional nebular techniques along with updated atomic data have been used to compute gaseous abundances of O, N and S in the Cocoon nebula. Thanks to the low ionization degree of the nebula, we could determine total abundances directly from observable ions (no ionization correction factors were needed) for three of the analyzed elements (O, S, and N). The derived stellar and nebular abundances are compared and the influence of the possible presence of the so-called temperature fluctuations on the nebula is discussed. The results of this study are presented in more detail in García-Rojas, Simón-Díaz & Esteban 2014, A&A, 571, A93.

  8. THE NUCLEAR ACTIVITIES OF NEARBY S0 GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xiao, Meng-Yuan; Gu, Qiu-Sheng; Chen, Yan-Mei

    2016-11-01

    We present a study of nuclear activities in nearby S0 galaxies. After cross-matching the Sloan Digital Sky Survey Data Release 7 with the Third Reference Catalog of Bright Galaxies (RC3) and visually checking the SDSS images, we derive a sample of 583 S0 galaxies with the central spectrophotometric information. In order to separate nebular emission lines from the underlying stellar contribution, we fit the stellar population model to the SDSS spectra of these S0 galaxies. According to the BPT diagram, we find that 8% of S0 galaxies show central star-forming activity, while the fractions of Seyfert, Composite, and low-ionization nuclearmore » emission-line regions (LINERs) are 2%, 8%, and 21.4%, respectively. We also find that star-forming S0s have the lowest stellar masses, over one magnitude lower than the others, and that the active S0s are mainly located in the sparse environment, while the normal S0s are located in the dense environment, which might suggest that the environment plays an important role in quenching star formation and/or AGN activity in S0 galaxies. By performing bulge-disk decomposition of 45 star-forming S0s in g - and r -bands with the 2D fitting software Galfit, as well as exploiting the catalog of 2D photometric decompositions of Meert et al., we find that the bulges of approximately one-third of star-forming S0 galaxies (16/45) are bluer than their disks, while for other types of S0s the bulge and disk components show similar color distributions. Besides, the Sérsic index of most star-forming S0s bulges is less than two, while for normal S0s, it is between two and six.« less

  9. Luminosity function of [OII] emission-line galaxies in the MassiveBlack-II simulation

    DOE PAGES

    Park, KwangHo; Khandai, Nishikanta; Matteo, Tiziana Di; ...

    2015-09-18

    We examine the luminosity function (LF) of [OII] emission-line galaxies in the high-resolution cosmological simulation MassiveBlack-II (MBII). From the spectral energy distribution of each galaxy, we select a sub-sample of star-forming galaxies at 0.06 ≤ z ≤ 3.0 using the [OII] emission line luminosity L([OII]). We confirm that the specific star formation rate matches that in the Galaxy And Mass Assembly survey. We show that the [OII] LF at z = 1.0 from the MBII shows good agreement with the LFs from several surveys below L([OII]) = 10 43.0 erg s –1 while the low redshifts (z ≤ 0.3) showmore » an excess in the prediction of bright [OII] galaxies, but still displaying a good match with observations below L([OII]) = 10 41.6 erg s –1. Based on the validity in reproducing the properties of [OII] galaxies at low redshift (z ≤ 1), we forecast the evolution of the [OII] LF at high redshift (z ≤ 3), which can be tested by upcoming surveys such as the Hobby-Eberly Telescope Dark Energy Experiment and Dark Energy Spectroscopic Instrument. The slopes of the LFs at bright and faint ends range from –3 to –2 showing minima at z = 2. The slope of the bright end evolves approximately as (z + 1) –1 at z ≤ 2 while the faint end evolves as ~3(z + 1) –1 at 0.6 ≤ z ≤ 2. In addition, a similar analysis is applied for the evolution of [OIII] LFs, which is to be explored in the forthcoming survey Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets. As a result, we show that the auto-correlation function of [OII] and [OIII] emitting galaxies shows a rapid evolution from z = 2 to 1.« less

  10. Intrinsic alignments of galaxies in the MassiveBlack-II simulation: Analysis of two-point statistics

    DOE PAGES

    Tenneti, Ananth; Singh, Sukhdeep; Mandelbaum, Rachel; ...

    2015-03-11

    The intrinsic alignment of galaxies with the large-scale density field in an important astrophysical contaminant in upcoming weak lensing surveys. We present detailed measurements of the galaxy intrinsic alignments and associated ellipticity-direction (ED) and projected shape (w g₊) correlation functions for galaxies in the cosmological hydrodynamic MassiveBlack-II (MB-II) simulation. We carefully assess the effects on galaxy shapes, misalignment of the stellar component with the dark matter shape and two-point statistics of iterative weighted (by mass and luminosity) definitions of the (reduced and unreduced) inertia tensor. We find that iterative procedures must be adopted for a reliable measurement of the reducedmore » tensor but that luminosity versus mass weighting has only negligible effects. Both ED and w g₊ correlations increase in amplitude with subhalo mass (in the range of 10¹⁰ – 6.0 X 10¹⁴h⁻¹ M ⊙), with a weak redshift dependence (from z = 1 to z = 0.06) at fixed mass. At z ~ 0.3, we predict a w g₊ that is in reasonable agreement with SDSS LRG measurements and that decreases in amplitude by a factor of ~ 5–18 for galaxies in the LSST survey. We also compared the intrinsic alignment of centrals and satellites, with clear detection of satellite radial alignments within the host halos. Finally, we show that w g₊ (using subhalos as tracers of density and w δ (using dark matter density) predictions from the simulations agree with that of non-linear alignment models (NLA) at scales where the 2-halo term dominates in the correlations (and tabulate associated NLA fitting parameters). The 1-halo term induces a scale dependent bias at small scales which is not modeled in the NLA model.« less

  11. The NIR Ca ii triplet at low metallicity. Searching for extremely low-metallicity stars in classical dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Starkenburg, E.; Hill, V.; Tolstoy, E.; González Hernández, J. I.; Irwin, M.; Helmi, A.; Battaglia, G.; Jablonka, P.; Tafelmeyer, M.; Shetrone, M.; Venn, K.; de Boer, T.

    2010-04-01

    The NIR Ca ii triplet absorption lines have proven to be an important tool for quantitative spectroscopy of individual red giant branch stars in the Local Group, providing a better understanding of metallicities of stars in the Milky Way and dwarf galaxies and thereby an opportunity to constrain their chemical evolution processes. An interesting puzzle in this field is the significant lack of extremely metal-poor stars, below [Fe/H] = -3, found in classical dwarf galaxies around the Milky Way using this technique. The question arises whether these stars are really absent, or if the empirical Ca ii triplet method used to study these systems is biased in the low-metallicity regime. Here we present results of synthetic spectral analysis of the Ca ii triplet, that is focused on a better understanding of spectroscopic measurements of low-metallicity giant stars. Our results start to deviate strongly from the widely-used and linear empirical calibrations at [Fe/H] < -2. We provide a new calibration for Ca ii triplet studies which is valid for -0.5 ≥ [Fe/H] ≥ -4. We subsequently apply this new calibration to current data sets and suggest that the classical dwarf galaxies are not so devoid of extremely low-metallicity stars as was previously thought. Using observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile proposal 171.B-0588.

  12. SDSS-II Supernova survey. An analysis of the largest sample of type IA supernovae and correlations with host-galaxy spectral properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wolf, Rachel C.; D’Andrea, Chris B.; Gupta, Ravi R.

    2016-04-20

    Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HR). Our sample consists of 345 photometrically-classified or spectroscopicallyconfirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric hostgalaxy properties from themore » SDSS-SNS data release (Sako et al. 2014) such as host stellar mass and star-formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6σ significance of a non-zero linear slope. We also recover correlations between HR and hostgalaxy gas-phase metallicity and specific star-formation rate as they are reported in the literature. With our large dataset, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically-confirmed and photometrically-classified SNe Ia and comment on the significance of similar combined datasets for future surveys.« less

  13. High resolution radio and optical observations of the central starburst in the low-metallicity dwarf galaxy II Zw 40

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kepley, Amanda A.; Reines, Amy E.; Johnson, Kelsey E.

    2014-02-01

    The extent to which star formation varies in galaxies with low masses, low metallicities, and high star formation rate surface densities is not well constrained. To gain insight into star formation under these physical conditions, this paper estimates the ionizing photon fluxes, masses, and ages for young massive clusters in the central region of II Zw 40—the prototypical low-metallicity dwarf starburst galaxy—from radio continuum and optical observations. Discrete, cluster-sized sources only account for half the total radio continuum emission; the remainder is diffuse. The young (≲ 5 Myr) central burst has a star formation rate surface density that significantly exceedsmore » that of the Milky Way. Three of the 13 sources have ionizing photon fluxes (and thus masses) greater than R136 in 30 Doradus. Although isolating the effects of galaxy mass and metallicity is difficult, the H II region luminosity function and the internal extinction in the center of II Zw 40 appear to be primarily driven by a merger-related starburst. The relatively flat H II region luminosity function may be the result of an increase in interstellar medium pressure during the merger and the internal extinction is similar to that generated by the clumpy and porous dust in other starburst galaxies.« less

  14. Variable Stars in the Field of the Hydra II Ultra-faint Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Vivas, A. Katherina; Olsen, Knut; Blum, Robert; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas F.; Besla, Gurtina; Gallart, Carme; van der Marel, Roeland P.; Majewski, Steven R.; Kaleida, Catherine C.; Muñoz, Ricardo R.; Saha, Abhijit; Conn, Blair C.; Jin, Shoko

    2016-05-01

    We report the discovery of one RR Lyrae star in the ultra-faint satellite galaxy Hydra II based on time series photometry in the g, r and I bands obtained with the Dark Energy Camera at Cerro Tololo Inter-American Observatory, Chile. The association of the RR Lyrae star discovered here with Hydra II is clear because is located at 42\\prime\\prime from the center of the dwarf, well within its half-light radius of 102\\prime\\prime . The RR Lyrae star has a mean magnitude of I=21.30+/- 0.04 which is too faint to be a field halo star. This magnitude translates to a heliocentric distance of 151 ± 8 kpc for Hydra II; this value is ˜ 13% larger than the estimate from the discovery paper based on the average magnitude of several blue horizontal branch star candidates. The new distance implies a slightly larger half-light radius of {76}-10+12 pc and a brighter absolute magnitude of {M}V=-5.1+/- 0.3, which keeps this object within the realm of the dwarf galaxies. A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.

  15. Gas and Dust Properties in Dwarf Irregular Galaxies

    NASA Technical Reports Server (NTRS)

    Jones, A. P.; Madden, S. C.; Colgan, S. W. J.; Geis, N.; Haas, M.; Maloney, P.; Nikola, T.; Poglitsch, A.

    1997-01-01

    We present a study of the 158 (micron)meter [C II] fine structure emission line from a sample of 11 low metallicity irregular galaxies using the NASA Kuiper Airborne Observatory (KAO). Our preliminary results demonstrate that the ratio of the 158 (micron)meter [C II] emission to the CO-12(1 yields 0) emission ranges from 6,000 to 46,000. These ratios are significantly enhanced relative to clouds within the Galaxy and to normal metallicity galaxies, which typically have values in the range 2,000 to 6,300. We also find that the [C II] emission in dwarf irregular galaxies can be up to 5% of the far-infrared (FIR) emission, a higher fraction of the FIR than in normal metallicity galaxies. We discuss these results for the dwarf irregular galaxies and compare them to those observed in normal metallicity galaxies. The enhanced 158 (micron)meter [C II] emission relative to CO-12(1 yields 0) emission can be understood in terms of the increased penetration depth of ultraviolet (UV) photons into the clouds in low metallicity environments.

  16. A Window on the Earliest Star Formation: Extreme Photoionization Conditions of a High-ionization, Low-metallicity Lensed Galaxy at z ∼ 2*

    NASA Astrophysics Data System (ADS)

    Berg, Danielle A.; Erb, Dawn K.; Auger, Matthew W.; Pettini, Max; Brammer, Gabriel B.

    2018-06-01

    We report new observations of SL2S J021737–051329, a lens system consisting of a bright arc at z = 1.84435, magnified ∼17× by a massive galaxy at z = 0.65. SL2S0217 is a low-mass (M < 109 M ⊙), low-metallicity (Z ∼ 1/20 Z ⊙) galaxy, with extreme star-forming conditions that produce strong nebular UV emission lines in the absence of any apparent outflows. Here we present several notable features from rest-frame UV Keck/LRIS spectroscopy: (1) Very strong narrow emission lines are measured for C IV λλ1548, 1550, He II λ1640, O III] λλ1661, 1666, Si III] λλ1883, 1892, and C III] λλ1907, 1909. (2) Double-peaked Lyα emission is observed with a dominant blue peak and centered near the systemic velocity. (3) The low- and high-ionization absorption features indicate very little or no outflowing gas along the sight line to the lensed galaxy. The relative emission-line strengths can be reproduced with a very high ionization, low-metallicity starburst with binaries, with the exception of He II, which indicates that an additional ionization source is needed. We rule out large contributions from active galactic nuclei and shocks to the photoionization budget, suggesting that the emission features requiring the hardest radiation field likely result from extreme stellar populations that are beyond the capabilities of current models. Therefore, SL2S0217 serves as a template for the extreme conditions that are important for reionization and thought to be more common in the early universe.

  17. A catalog of low surface brightness galaxies - List II

    NASA Technical Reports Server (NTRS)

    Schombert, James M.; Bothun, Gregory D.; Schneider, Stephen E.; Mcgaugh, Stacy S.

    1992-01-01

    A list of galaxies characterized by low surface brightness (LSB) is presented which facilitates the recognition of galaxies with brightnesses close to that of the sky. A total of 198 objects and 140 objects are listed in the primary and secondary catalogs respectively, and LSB galaxies are examined by means of H I redshift distributions. LSB disk galaxies are shown to have similar sizes and masses as the high-surface-brightness counterparts, and ellipticals and SOs are rarely encountered. Many LSB spirals have stellarlike nuclei, and most of the galaxies in the present catalog are late-type galaxies in the Sc, Sm, and Im classes. The LSB region of observational parameter space is shown to encompass a spectrum of types as full as that of the Hubble sequence. It is suggested that studies of LSB galaxies can provide important data regarding the formation and star-formation history of all galaxies.

  18. Indirect dark matter searches in the dwarf satellite galaxy Ursa Major II with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Baack, D.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berse, R. Ch.; Berti, A.; Bhattacharyya, W.; Biland, A.; Blanch, O.; Bonnoli, G.; Carosi, R.; Carosi, A.; Ceribella, G.; Chatterjee, A.; Colak, S. M.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Delfino, M.; Delgado, J.; Di Pierro, F.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Elsaesser, D.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Masuda, S.; Mazin, D.; Mielke, K.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Nagayoshi, T.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pedaletti, G.; Peresano, M.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saito, T.; Satalecka, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takahashi, M.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Albà, N.; Treves, A.; Tsujimoto, S.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Zarić, D.

    2018-03-01

    The dwarf spheroidal galaxy Ursa Major II (UMaII) is believed to be one of the most dark-matter dominated systems among the Milky Way satellites and represents a suitable target for indirect dark matter (DM) searches. The MAGIC telescopes carried out a deep observation campaign on UMaII between 2014 and 2016, collecting almost one hundred hours of good-quality data. This campaign enlarges the pool of DM targets observed at very high energy (E gtrsim 50 GeV) in search for signatures of DM annihilation in the wide mass range between ~100 GeV and ~100 TeV. To this end, the data are analyzed with the full likelihood analysis, a method based on the exploitation of the spectral information of the recorded events for an optimal sensitivity to the explored DM models. We obtain constraints on the annihilation cross-section for different channels that are among the most robust and stringent achieved so far at the TeV mass scale from observations of dwarf satellite galaxies.

  19. First Characterization of the Neutral ISM in Two Local Volume Dwarf Galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bralts-Kelly, Lilly; Bulatek, Alyssa M.; Chinski, Sarah

    We present the first H i spectral-line images of the nearby, star-forming dwarf galaxies UGC 11411 and UGC 8245, acquired as part of the “Observing for University Classes” program with the Karl G. Jansky Very Large Array (VLA). These low-resolution images localize the H i gas and reveal the bulk kinematics of each system. Comparing with Hubble Space Telescope ( HST ) broadband and ground-based H α imaging, we find that the ongoing star formation in each galaxy is associated with the highest H i mass surface density regions. UGC 8245 has a much lower current star formation rate thanmore » UGC 11411, which harbors very high surface brightness H α emission in the inner disk and diffuse, lower surface brightness nebular gas that extends well beyond the stellar disk as traced by HST . We measure the dynamical masses of each galaxy and find that the halo of UGC 11411 is more than an order of magnitude more massive than the halo of UGC 8245, even though the H i and stellar masses of the sources are similar. We show that UGC 8245 shares similar physical properties with other well-studied low-mass galaxies, while UGC 11411 is more highly dark matter dominated. Both systems have negative peculiar velocities that are associated with a coherent flow of nearby galaxies at high supergalactic latitude.« less

  20. On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions

    NASA Technical Reports Server (NTRS)

    Simpson, Janet P.; Rubin, Robert H.; Colgan, Sean W. J.; Erickson, Edwin F.; Haas, Michael R.

    2004-01-01

    Although abundance gradients in the Milky Way Galaxy certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in G333.6-0.2 with the Kuiper Airborne Observatory and reobserved the central position with the Infrared Space Observatory's Long Wavelength Spectrometer in far-infrared lines of S++, N++, N+, and O++. We also added the N+ lines at 122 and 205 microns to the suite of lines measured in W43 by Simpson et al.. The measured electron densities range from approx. 40 to over 4000 per cu cm in a single HII region, indicating that abundance analyses must consider density variations, since the critical densities of the observed lines range from 40 to 9000 per cu cm. We propose a method to handle density variations and make new estimates of the S/H and N/H abundance ratios. We find that our sulfur abundance estimates for G333.6-0.2 and W43 agree with the S/H abundance ratios expected for the gradient previously reported by Simpson et al., with the S/H values revised to be smaller owing to changes in collisional excitation cross sections. The estimated N/H, S/H, and N/S ratios are the most reliable because of their small corrections for unseen ionization states (< or approx. 10%). The estimated N/S ratios for the two sources are smaller than what would be calculated from the N/H and S/H ratios in our previous paper. If all low excitation H II regions had similar changes to their N/S ratios as a result of adding measurements of N+ to previous measurements of N++, there would be no or only a very small gradient in N/S. This is interesting because nitrogen is considered to be a secondary element and sulfur is a primary element in galactic chemical evolution calculations. We compute models of the two H II regions to estimate corrections for the other

  1. Mass Distribution in Galaxy Cluster Cores

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hogan, M. T.; McNamara, B. R.; Pulido, F.

    Many processes within galaxy clusters, such as those believed to govern the onset of thermally unstable cooling and active galactic nucleus feedback, are dependent upon local dynamical timescales. However, accurate mapping of the mass distribution within individual clusters is challenging, particularly toward cluster centers where the total mass budget has substantial radially dependent contributions from the stellar ( M {sub *}), gas ( M {sub gas}), and dark matter ( M {sub DM}) components. In this paper we use a small sample of galaxy clusters with deep Chandra observations and good ancillary tracers of their gravitating mass at both largemore » and small radii to develop a method for determining mass profiles that span a wide radial range and extend down into the central galaxy. We also consider potential observational pitfalls in understanding cooling in hot cluster atmospheres, and find tentative evidence for a relationship between the radial extent of cooling X-ray gas and nebular H α emission in cool-core clusters. At large radii the entropy profiles of our clusters agree with the baseline power law of K ∝ r {sup 1.1} expected from gravity alone. At smaller radii our entropy profiles become shallower but continue with a power law of the form K ∝ r {sup 0.67} down to our resolution limit. Among this small sample of cool-core clusters we therefore find no support for the existence of a central flat “entropy floor.”.« less

  2. ALMA observation of 158 μm [C II] line and dust continuum of a z = 7 normally star-forming galaxy in the epoch of reionization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ota, Kazuaki; Walter, Fabian; Da Cunha, Elisabete

    We present ALMA observations of the [C II] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z = 6.96 Lyα emitter (LAE) IOK-1. Probing to sensitivities of σ{sub line} = 240 μJy beam{sup –1} (40 km s{sup –1} channel) and σ{sub cont} = 21 μJy beam{sup –1}, we found the galaxy undetected in both [C II] and continuum. Comparison of ultraviolet (UV)-FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum)more » suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3σ FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M {sub dust} < 6.4 × 10{sup 7} M {sub ☉}, FIR luminosity L {sub FIR} < 3.7 × 10{sup 10} L {sub ☉} (42.5-122.5 μm), total IR luminosity L {sub IR} < 5.7 × 10{sup 10} L {sub ☉} (8-1000 μm), and dust-obscured star formation rate (SFR) < 10 M {sub ☉} yr{sup –1}, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that <29% of the star formation is obscured by dust. Meanwhile, our 3σ [C II] flux limit translates into [C II] luminosity, L {sub [C} {sub II]} < 3.4 × 10{sup 7} L {sub ☉}. Locations of IOK-1 and previously observed LAEs on the L {sub [C} {sub II]} versus SFR and L {sub [C} {sub II]}/L {sub FIR} versus L {sub FIR} diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.« less

  3. Diffuse ionized gas in galaxies across the Hubble sequence at the CALIFA resolution

    NASA Astrophysics Data System (ADS)

    Lacerda, E. A. D.; Cid Fernandes, R.; Couto, G. S.; Stasińska, G.; García-Benito, R.; Vale Asari, N.; Pérez, E.; González Delgado, R. M.; Sánchez, S. F.; de Amorim, A. L.

    2018-03-01

    We use spatially resolved spectroscopy from the Calar Alto Legacy Integral Field Area (CALIFA) survey to study the nature of the line emitting gas in galaxies of different Hubble types, focusing on the separation of star-forming (SF) regions from those better characterized as diffuse ionized gas (DIG). The diagnosis is carried out in terms of the equivalent width of H α (WH α). Three nebular regimes are identified. Regions where WH α < 3 Å define what we call the hDIG, the component of the DIG where photoionization is dominated by hot, low-mass, evolved stars. Regions where WH α > 14 Å trace SF complexes. WH α values in the intermediate 3-14 Å range reflect a mixed regime (mDIG) where more than one process contributes. This three-tier scheme is inspired both by theoretical and empirical considerations. Its application to CALIFA galaxies of different types and inclinations leads to the following results: (i) the hDIG component is prevalent throughout ellipticals and S0's as well as in bulges, and explains the strongly bimodal distribution of WH α both among and within galaxies. (ii) Early-type spirals have some hDIG in their discs, but this component becomes progressively less relevant for later Hubble types. (iii) hDIG emission is also present above and below galactic discs, as seen in several edge-on spirals in our sample. (iv) The SF/mDIG proportion grows steadily from early- to late-type spirals, and from inner to outer radii. (v) Besides circumventing basic inconsistencies in conventional DIG/SF separation criteria based on the H α surface brightness, our WH α-based method produces results in agreement with a classical excitation diagram analysis.

  4. Modelling ultraviolet-line diagnostics of stars, the ionized and the neutral interstellar medium in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Vidal-García, A.; Charlot, S.; Bruzual, G.; Hubeny, I.

    2017-09-01

    We combine state-of-the-art models for the production of stellar radiation and its transfer through the interstellar medium (ISM) to investigate ultraviolet-line diagnostics of stars, the ionized and the neutral ISM in star-forming galaxies. We start by assessing the reliability of our stellar population synthesis modelling by fitting absorption-line indices in the ISM-free ultraviolet spectra of 10 Large Magellanic Cloud clusters. In doing so, we find that neglecting stochastic sampling of the stellar initial mass function in these young (∼10-100 Myr), low-mass clusters affects negligibly ultraviolet-based age and metallicity estimates but can lead to significant overestimates of stellar mass. Then, we proceed and develop a simple approach, based on an idealized description of the main features of the ISM, to compute in a physically consistent way the combined influence of nebular emission and interstellar absorption on ultraviolet spectra of star-forming galaxies. Our model accounts for the transfer of radiation through the ionized interiors and outer neutral envelopes of short-lived stellar birth clouds, as well as for radiative transfer through a diffuse intercloud medium. We use this approach to explore the entangled signatures of stars, the ionized and the neutral ISM in ultraviolet spectra of star-forming galaxies. We find that, aside from a few notable exceptions, most standard ultraviolet indices defined in the spectra of ISM-free stellar populations are prone to significant contamination by the ISM, which increases with metallicity. We also identify several nebular-emission and interstellar-absorption features, which stand out as particularly clean tracers of the different phases of the ISM.

  5. Accurate Distances to Important Spiral Galaxies: M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dolphin, Andrew E.

    Accurate distances are fundamental for interpreting various measured properties of galaxies. Surprisingly, many of the best-studied spiral galaxies in the Local Volume have distance uncertainties that are much larger than can be achieved with modern observation techniques. Using Hubble Space Telescope optical imaging, we use the tip of the red giant branch method to measure the distances to six galaxies that are included in the Spitzer Infrared Nearby Galaxies Survey program and its offspring surveys. The sample includes M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398. We compare our results with distances reported to these galaxies basedmore » on a variety of methods. Depending on the technique, there can be a wide range in published distances, particularly from the Tully–Fisher relation. In addition, differences between the planetary nebular luminosity function and surface brightness fluctuation techniques can vary between galaxies, suggesting inaccuracies that cannot be explained by systematics in the calibrations. Our distances improve upon previous results, as we use a well-calibrated, stable distance indicator, precision photometry in an optimally selected field of view, and a Bayesian maximum likelihood technique that reduces measurement uncertainties.« less

  6. The Puzzlingly Small Ca II Triplet Absorption in Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Saglia, R. P.; Maraston, Claudia; Thomas, Daniel; Bender, Ralf; Colless, Matthew

    2002-11-01

    We measure the central values (within Re/8) of the Ca II triplet line indices CaT* and CaT and the Paschen index PaT at 8600 Å for a 93% complete sample of 75 nearby early-type galaxies with BT<12 mag and Vgal<2490 km s-1. We find that the values of CaT* are constant to within 5% over the range of central velocity dispersions 100 km s-1<=σ<=340 km s-1, while the PaT (and CaT) values are mildly anticorrelated with σ. Using simple and composite stellar population models, we show the following: (1) The measured CaT* and CaT are lower than expected from simple stellar population (SSP) models with Salpeter initial mass functions (IMFs) and with metallicities and ages derived from optical Lick (Fe, Mg, and Hβ) indices. Uncertainties in the calibration, the fitting functions, and the SSP modeling taken separately cannot explain the discrepancy. On average, the observed PaT values are within the range allowed by the models and the large uncertainties in the fitting functions. (2) The steepening of the IMF at low masses required to lower the CaT* and CaT indices to the observed values is incompatible with the measured FeH index at 9916 Å and the dynamical mass-to-light ratios of elliptical galaxies. (3) Composite stellar populations with a low-metallicity component reduce the disagreement, but rather artificial metallicity distributions are needed. Another explanation may be that calcium is indeed underabundant in elliptical galaxies.

  7. Addressing Ionization and Depletion in the ISM of Nearby Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Aloisi, Alessandra

    2017-08-01

    Measuring galaxy metallicity with cosmic time is of paramount importance to understand galaxy formation. ISM abundances are typically determined using emission-line spectroscopy of HII regions. However, HII regions may be self-enriched and not typical of the whole galaxy. This is particularly true for star-forming galaxies (SFGs) where the bulk of metals may be in the neutral gas. Quantifying metals in the ISM is thus important to assess how reliably HII regions trace galaxy abundances at any redshift. We were awarded 34 HST orbits (Cycle 17) to measure abundances in the neutral ISM of 9 nearby SFGs using absorption lines in the COS G130M/1291 spectra of bright UV background sources within the galaxy itself. We found metallicities that differ by up to 2 dex depending on the element. These variations could be real or due to observational effects. Here we request 22 orbits in the new G130M/1222 and in G160M/1623 to access new FUV spectral transitions that will help us characterize ionized-gas contamination and dust depletion, and ultimately nail down the abundances of the different elements. These new data will nicely complement our Cycle 17 COS and Gemini/GMOS IFU programs, the latter aimed at deriving nebular abundances along the same COS sightlines. This first detailed and spatially-accurate comparison between neutral- and ionized-gas abundances in local (z 0) SFGs will provide crucial insights into the metallicity of galaxies at any redshift. If this UV spectroscopic study is not undertaken before HST ceases operation, the (in)homogeneity of the ISM in galaxies of the local Universe will continue to remain uncertain for at least another decade.

  8. Herschel Spectroscopy of Early-type Galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lapham, Ryen Carl; Young, Lisa M.; Crocker, Alison, E-mail: ryen.lapham@student.nmt.edu, E-mail: lyoung@physics.nmt.edu, E-mail: crockera@reed.edu

    We present Herschel spectroscopy of atomic lines arising in photodissociation regions as well as ionization regions of nearby early-type galaxies (ETGs), focusing on the volume-limited Atlas3D sample. Our data include the [C ii], [O i], and [N ii] 122 and 205 μ m lines, along with ancillary data including CO and H i maps. We find that ETGs have [C ii]/FIR ratios slightly lower than spiral galaxies in the KINGFISH sample, and several ETGs have unusually large [N ii] 122/[C ii] ratios. The [N ii] 122/[C ii] ratio is correlated with UV colors and there is a strong anti-correlation ofmore » [C ii]/FIR with NUV-K seen in both spirals and ETGs, likely due to a softer radiation field with fewer photons available to ionize carbon and heat the gas. The correlation thus makes a [C ii] deficit in galaxies with redder stellar populations. The high [N ii] 122/[C ii] (and low [C ii]/FIR) line ratios could also be affected by the removal of much of the diffuse, low-density gas, which is consistent with the low H i/H{sub 2} ratios. [C ii] is now being used as a star-formation indicator, and we find that it is just as good for ETGs as in spirals. The [C ii]/CO ratios found are also similar to those found in spiral galaxies. Through the use of the [N ii] 205 μ m line, estimates of the percentage of [C ii] emission arising from ionized gas indicate that a significant portion could arise in ionized regions.« less

  9. EXPLAINING THE [C II]157.7 {mu}m DEFICIT IN LUMINOUS INFRARED GALAXIES-FIRST RESULTS FROM A HERSCHEL/PACS STUDY OF THE GOALS SAMPLE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Diaz-Santos, T.; Armus, L.; Howell, J. H.

    We present the first results of a survey of the [C II]157.7 {mu}m emission line in 241 luminous infrared galaxies (LIRGs) comprising the Great Observatories All-sky LIRG Survey (GOALS) sample, obtained with the PACS instrument on board the Herschel Space Observatory. The [C II] luminosities, L{sub [C{sub II]}}, of the LIRGs in GOALS range from {approx}10{sup 7} to 2 Multiplication-Sign 10{sup 9} L{sub Sun }. We find that LIRGs show a tight correlation of [C II]/FIR with far-IR (FIR) flux density ratios, with a strong negative trend spanning from {approx}10{sup -2} to 10{sup -4}, as the average temperature of dustmore » increases. We find correlations between the [C II]/FIR ratio and the strength of the 9.7 {mu}m silicate absorption feature as well as with the luminosity surface density of the mid-IR emitting region ({Sigma}{sub MIR}), suggesting that warmer, more compact starbursts have substantially smaller [C II]/FIR ratios. Pure star-forming LIRGs have a mean [C II]/FIR {approx} 4 Multiplication-Sign 10{sup -3}, while galaxies with low polycyclic aromatic hydrocarbon (PAH) equivalent widths (EWs), indicative of the presence of active galactic nuclei (AGNs), span the full range in [C II]/FIR. However, we show that even when only pure star-forming galaxies are considered, the [C II]/FIR ratio still drops by an order of magnitude, from 10{sup -2} to 10{sup -3}, with {Sigma}{sub MIR} and {Sigma}{sub IR}, implying that the [C II]157.7 {mu}m luminosity is not a good indicator of the star formation rate (SFR) for most local LIRGs, for it does not scale linearly with the warm dust emission most likely associated to the youngest stars. Moreover, even in LIRGs in which we detect an AGN in the mid-IR, the majority (2/3) of galaxies show [C II]/FIR {>=} 10{sup -3} typical of high 6.2 {mu}m PAH EW sources, suggesting that most AGNs do not contribute significantly to the FIR emission. We provide an empirical relation between the [C II]/FIR and the specific SFR for star

  10. Galaxy Formation through Filamentary Accretion at z = 6.1

    NASA Astrophysics Data System (ADS)

    Jones, G. C.; Willott, C. J.; Carilli, C. L.; Ferrara, A.; Wang, R.; Wagg, J.

    2017-08-01

    We present Atacama Large Millimeter/submillimeter Array observations of the dust continuum and [C II] 158 μm line emission from the z = 6.0695 Lyman-Break Galaxy (LBG) WMH5. These observations at 0.″3 spatial resolution show a compact (˜3 kpc) main galaxy in dust and [C II] emission, with a “tail” of emission extending to the east by about 5 kpc (in projection). The [C II] tail is comprised predominantly of two distinct sub-components in velocity, separated from the core by ˜100 and 250 km s-1, with narrow intrinsic widths of about 80 km s-1, which we call “sub-galaxies.” The sub-galaxies themselves are extended east-west by about 3 kpc in individual channel images. The [C II] tail joins smoothly into the main galaxy velocity field. The [C II] line to continuum ratios are comparable for the main and sub-galaxy positions, within a factor two. In addition, these ratios are comparable to z˜ 5.5 LBGs. We conjecture that the WMH5 system represents the early formation of a galaxy through the accretion of smaller satellite galaxies, embedded in a smoother gas distribution, along a possibly filamentary structure. The results are consistent with current cosmological simulations of early galaxy formation and support the idea of very early enrichment with dust and heavy elements of the accreting material.

  11. Spiral-like star-forming patterns in CALIFA early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gomes, J. M.; Papaderos, P.; Vílchez, J. M.; Kehrig, C.; Iglesias-Páramo, J.; Breda, I.; Lehnert, M. D.; Sánchez, S. F.; Ziegler, B.; Dos Reis, S. N.; Bland-Hawthorn, J.; Galbany, L.; Bomans, D. J.; Rosales-Ortega, F. F.; Walcher, C. J.; García-Benito, R.; Márquez, I.; Del Olmo, A.; Mollá, M.; Marino, R. A.; Catalán-Torrecilla, C.; González Delgado, R. M.; López-Sánchez, Á. R.; Califa Collaboration

    2016-01-01

    Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 <μr mag/□″< 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified I+, is a two-radial-zone structure, with the inner zone that displays faint (EW(Hα) ≃ 1 Å) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3 Å nebular emission in two physically distinct concentric zones calls for an examination of aperture effects in studies of type I+ ETGs with single-fiber spectroscopic data. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie (MPIA) and the Instituto de Astrofísica de Andalucía (CSIC).

  12. GRB 080517: a local, low-luminosity gamma-ray burst in a dusty galaxy at z = 0.09

    NASA Astrophysics Data System (ADS)

    Stanway, Elizabeth R.; Levan, Andrew J.; Tanvir, Nial; Wiersema, Klaas; van der Horst, Alexander; Mundell, Carole G.; Guidorzi, Cristiano

    2015-02-01

    We present an analysis of the photometry and spectroscopy of the host galaxy of Swift-detected GRB 080517. From our optical spectroscopy, we identify a redshift of z = 0.089 ± 0.003, based on strong emission lines, making this a rare example of a very local, low-luminosity, long gamma-ray burst. The galaxy is detected in the radio with a flux density of S4.5 GHz = 0.22 ± 0.04 mJy - one of relatively few known gamma-ray bursts hosts with a securely measured radio flux. Both optical emission lines and a strong detection at 22 μm suggest that the host galaxy is forming stars rapidly, with an inferred star formation rate ˜16 M⊙ yr-1 and a high dust obscuration (E(B - V) > 1, based on sightlines to the nebular emission regions). The presence of a companion galaxy within a projected distance of 25 kpc, and almost identical in redshift, suggests that star formation may have been triggered by galaxy-galaxy interaction. However, fitting of the remarkably flat spectral energy distribution from the ultraviolet through to the infrared suggests that an older, 500 Myr post-starburst stellar population is present along with the ongoing star formation. We conclude that the host galaxy of GRB 080517 is a valuable addition to the still very small sample of well-studied local gamma-ray burst hosts.

  13. First light: exploring the spectra of high-redshift galaxies in the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    Barrow, Kirk S. S.; Wise, John H.; Norman, Michael L.; O'Shea, Brian W.; Xu, Hao

    2017-08-01

    We present synthetic observations for the first generations of galaxies in the Universe and make predictions for future deep field observations for redshifts greater than 6. Due to the strong impact of nebular emission lines and the relatively compact scale of H II regions, high-resolution cosmological simulations and a robust suite of analysis tools are required to properly simulate spectra. We created a software pipeline consisting of fsps, hyperion, cloudy and our own tools to generate synthetic IR observations from a fully three-dimensional arrangement of gas, dust, and stars. Our prescription allows us to include emission lines for a complete chemical network and tackle the effect of dust extinction and scattering in the various lines of sight. We provide spectra, 2D binned photon imagery for both HST and JWST IR filters, luminosity relationships, and emission-line strengths for a large sample of high-redshift galaxies in the Renaissance Simulations. Our resulting synthetic spectra show high variability between galactic haloes with a strong dependence on stellar mass, metallicity, gas mass fraction, and formation history. Haloes with the lowest stellar mass have the greatest variability in [O III]/Hβ, [O III], and C III], while haloes with higher masses are seen to show consistency in their spectra and [O III] equivalent widths between 1 and 10 Å. Viewing angle accounted for threefold difference in flux due to the presence of ionized gas channels in a halo. Furthermore, JWST colour plots show a discernible relationship between redshift, colour, and mean stellar age.

  14. Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra

    NASA Astrophysics Data System (ADS)

    Leonard, Douglas

    2006-02-01

    The progenitor systems of Type Ia supernovae (SNe Ia) are observationally unconstrained. Prevailing theory invokes a carbon- oxygen white dwarf accreting matter from a companion until a thermonuclear runaway ensues that incinerates the white dwarf. While models of exploding carbon-oxygen white dwarfs faithfully reproduce the main characteristics of SNe Ia, we are ignorant about the nature of the proposed companion star. Simulations resulting from this single- degenerate binary channel, however, demand the presence of low-velocity, H(alpha) emission in spectra taken in the nebular phase (250 - 400 days after maximum light), since a portion of the companion's envelope becomes entrained in the ejecta. This hydrogen has never been detected, and only generally weak limits have heretofore been set from ~ 6 SNe Ia observed during the nebular phase at low resolution and often with a low signal-to-noise ratio (S/N). We propose to remedy this situation through high S/N observations of two nearby, nebular-phase SNe Ia, with sufficient sensitivity and resolution to detect ~ 0.01 Msun of solar abundance material in the ejecta. The detection of late- time H(alpha) emission would be considered a ``smoking gun'' for the binary scenario. If H(alpha) is not detected, the limits will effectively rule out sub-giant, red giant, and all but the most widely separated main-sequence companions.

  15. Ultraviolet spectra of extreme nearby star-forming regions - approaching a local reference sample for JWST

    NASA Astrophysics Data System (ADS)

    Senchyna, Peter; Stark, Daniel P.; Vidal-García, Alba; Chevallard, Jacopo; Charlot, Stéphane; Mainali, Ramesh; Jones, Tucker; Wofford, Aida; Feltre, Anna; Gutkin, Julia

    2017-12-01

    Nearby dwarf galaxies provide a unique laboratory in which to test stellar population models below Z⊙/2. Such tests are particularly important for interpreting the surprising high-ionization ultraviolet (UV) line emission detected at z > 6 in recent years. We present HST/COS UV spectra of 10 nearby metal-poor star-forming galaxies selected to show He II emission in SDSS optical spectra. The targets span nearly a dex in gas-phase oxygen abundance (7.8 < 12 + log O/H < 8.5) and present uniformly large specific star formation rates (sSFR ∼102 Gyr-1). The UV spectra confirm that metal-poor stellar populations can power extreme nebular emission in high-ionization UV lines, reaching C III] equivalent widths comparable to those seen in systems at z ∼ 6-7. Our data reveal a marked transition in UV spectral properties with decreasing metallicity, with systems below 12 + log O/H ≲ 8.0 (Z/Z⊙ ≲ 1/5) presenting minimal stellar wind features and prominent nebular emission in He II and C IV. This is consistent with nearly an order of magnitude increase in ionizing photon production beyond the He+-ionizing edge relative to H-ionizing flux as metallicity decreases below a fifth solar, well in excess of standard stellar population synthesis predictions. Our results suggest that often-neglected sources of energetic radiation such as stripped binary products and very massive O-stars produce a sharper change in the ionizing spectrum with decreasing metallicity than expected. Consequently, nebular emission in C IV and He II powered by these stars may provide useful metallicity constraints in the reionization era.

  16. FR II radio galaxies at low frequencies - I. Morphology, magnetic field strength and energetics.

    PubMed

    Harwood, Jeremy J; Croston, Judith H; Intema, Huib T; Stewart, Adam J; Ineson, Judith; Hardcastle, Martin J; Godfrey, Leith; Best, Philip; Brienza, Marisa; Heesen, Volker; Mahony, Elizabeth K; Morganti, Raffaella; Murgia, Matteo; Orrú, Emanuela; Röttgering, Huub; Shulevski, Aleksandar; Wise, Michael W

    2016-06-01

    Due to their steep spectra, low-frequency observations of Fanaroff-Riley type II (FR II) radio galaxies potentially provide key insights in to the morphology, energetics and spectrum of these powerful radio sources. However, limitations imposed by the previous generation of radio interferometers at metre wavelengths have meant that this region of parameter space remains largely unexplored. In this paper, the first in a series examining FR IIs at low frequencies, we use LOFAR (LOw Frequency ARray) observations between 50 and 160 MHz, along with complementary archival radio and X-ray data, to explore the properties of two FR II sources, 3C 452 and 3C 223. We find that the morphology of 3C 452 is that of a standard FR II rather than of a double-double radio galaxy as had previously been suggested, with no remnant emission being observed beyond the active lobes. We find that the low-frequency integrated spectra of both sources are much steeper than expected based on traditional assumptions and, using synchrotron/inverse-Compton model fitting, show that the total energy content of the lobes is greater than previous estimates by a factor of around 5 for 3C 452 and 2 for 3C 223. We go on to discuss possible causes of these steeper-than-expected spectra and provide revised estimates of the internal pressures and magnetic field strengths for the intrinsically steep case. We find that the ratio between the equipartition magnetic field strengths and those derived through synchrotron/inverse-Compton model fitting remains consistent with previous findings and show that the observed departure from equipartition may in some cases provide a solution to the spectral versus dynamical age disparity.

  17. Chondritic Mn/Na ratio and limited post-nebular volatile loss of the Earth

    NASA Astrophysics Data System (ADS)

    Siebert, Julien; Sossi, Paolo A.; Blanchard, Ingrid; Mahan, Brandon; Badro, James; Moynier, Frédéric

    2018-03-01

    The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth's core. Here we quantify the metal-silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P-T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth's Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post

  18. H II regions as probes of galaxy evolution and the properties of massive stars

    NASA Technical Reports Server (NTRS)

    Garnett, Donald R.

    1993-01-01

    The use of H II regions as probes to study the chemical evolution of galaxies and the spectral properties of hot, massive stars is reviewed. The observable parameters for this task are the physical conditions, elemental abundances, and ionization balance in the ionized gas. Some outstanding uncertainties in the determination of these parameters and some approaches to remedy or circumvent the problems are discussed.

  19. The Taxonomy of Blue Amorphous Galaxies. I. Hα and UBVI Data

    NASA Astrophysics Data System (ADS)

    Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.; Schommer, Robert

    1997-10-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution. We have embarked on a systematic study of 12 nearby dwarf galaxies (most of which have been classified as amorphous) selected preferentially by their blue colors. The properties of the galaxies in the sample suggest that they are in a burst or postburst state. It seems likely that these amorphous galaxies are closely related to other ``starburst'' dwarfs such as blue compact dwarfs (BCDs) and H II galaxies but are considerably closer and therefore easier to study. If so, these galaxies may offer important insights into dwarf galaxy evolution. In an effort to clarify the role of starbursts in evolutionary scenarios for dwarf galaxies, we present Hα and UBVI data for our sample. Blue amorphous galaxies, like BCDs and H II galaxies, have surface brightness profiles that are exponential in the outer regions (r >~ 1.5re) but have a predominantly blue central excess, which suggests a young burst in an older, redder galaxy. Seven of the galaxies have the bubble or filamentary Hα morphology and double-peaked emission lines that are the signature of superbubbles or superwind activity. These galaxies are typically the ones with the strongest central excesses. The underlying exponential galaxies are very similar to those found in BCDs and H II galaxies. How amorphous galaxies fit into the dwarf irregular-``starburst dwarf''-dwarf elliptical evolutionary debate is less clear. In this paper, we present our data and make some preliminary comparisons between amorphous galaxies and other classes of dwarf galaxies. In a future companion paper, we will compare this sample more quantitatively with other dwarf galaxy samples in an effort to determine if amorphous galaxies are a physically different class of object from other starburst dwarfs such as BCDs and H II galaxies and also investigate their place in dwarf galaxy evolution scenarios.

  20. Stellar Populations and Radial Migrations in Virgo Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Roediger, Joel C.; Courteau, Stéphane; Sánchez-Blázquez, Patricia; McDonald, Michael

    2012-10-01

    We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ("U-shapes") in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third (<=36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks (~11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail (>=50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely focused on field

  1. Blue compact dwarf galaxies. I - Neutral hydrogen observations of 115 galaxies

    NASA Technical Reports Server (NTRS)

    Thuan, T. X.; Martin, G. E.

    1981-01-01

    HI observations are reported for a sample of 115 blue compact dwarf (M sub B greater than approximately -18) galaxies or 'extragalactic H II regions' chosen mostly from the objective prism surveys of Markarian (1967-1974) and Haro (1956), with a few objects from Zwicky (1971) and other investigators. Ninety-three galaxies are detected. H I profiles, neutral hydrogen masses, total masses, and all available optical data are given for the 115 galaxies in a consistent and homogeneous system and in a useful format for statistical studies. The data are used in a companion paper to study the stochastic mode of star formation in galaxies.

  2. The nature of extreme emission line galaxies at z = 1-2: kinematics and metallicities from near-infrared spectroscopy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maseda, Michael V.; Van der Wel, Arjen; Rix, Hans-Walter

    2014-08-10

    We present near-infrared spectroscopy of a sample of 22 Extreme Emission Line Galaxies at redshifts 1.3 < z < 2.3, confirming that these are low-mass (M{sub *} = 10{sup 8}-10{sup 9} M{sub ☉}) galaxies undergoing intense starburst episodes (M{sub *}/SFR ∼ 10-100 Myr). The sample is selected by [O III] or Hα emission line flux and equivalent width using near-infrared grism spectroscopy from the 3D-HST survey. High-resolution NIR spectroscopy is obtained with LBT/LUCI and VLT/X-SHOOTER. The [O III]/Hβ line ratio is high (≳ 5) and [N II]/Hα is always significantly below unity, which suggests a low gas-phase metallicity. We aremore » able to determine gas-phase metallicities for seven of our objects using various strong-line methods, with values in the range 0.05-0.30 Z{sub ☉} and with a median of 0.15 Z{sub ☉}; for three of these objects we detect [O III] λ4363, which allows for a direct constraint on the metallicity. The velocity dispersion, as measured from the nebular emission lines, is typically ∼50 km s{sup –1}. Combined with the observed star-forming activity, the Jeans and Toomre stability criteria imply that the gas fraction must be large (f{sub gas} ≳ 2/3), consistent with the difference between our dynamical and stellar mass estimates. The implied gas depletion timescale (several hundred Myr) is substantially longer than the inferred mass-weighted ages (∼50 Myr), which further supports the emerging picture that most stars in low-mass galaxies form in short, intense bursts of star formation.« less

  3. Low-redshift Lyman continuum leaking galaxies with high [O III]/[O II] ratios

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Worseck, G.; Schaerer, D.; Guseva, N. G.; Thuan, T. X.; Fricke, K. J.; Verhamme, A.; Orlitová, I.

    2018-05-01

    We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of five star-forming galaxies at redshifts z in the range 0.2993 - 0.4317 and with high emission-line flux ratios O32 = [O III]λ5007/[O II]λ3727 ˜ 8 - 27 aiming to detect the Lyman continuum (LyC) emission. We detect LyC emission in all galaxies with the escape fractions fesc(LyC) in a range of 2 - 72 per cent. A narrow Lyα emission line with two peaks in four galaxies and with three peaks in one object is seen in medium-resolution COS spectra with a velocity separation between the peaks Vsep varying from ˜153 km s-1 to ˜ 345 km s-1. We find a general increase of the LyC escape fraction with increasing O32 and decreasing stellar mass M⋆, but with a large scatter of fesc(LyC). A tight anti-correlation is found between fesc(LyC) and Vsep making Vsep a good parameter for the indirect determination of the LyC escape fraction. We argue that one possible source driving the escape of ionizing radiation is stellar winds and radiation from hot massive stars.

  4. Characterizing the Interstellar and Circumgalactic Medium in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Du, Xinnan; Shapley, Alice; Crystal Martin, Alison Coil, Charles Steidel, Tucker Jones, Daniel Stark, Allison Strom

    2018-01-01

    Rest-frame UV and optical spectroscopy provide valuable information on the physical properties of the neutral and ionized interstellar medium (ISM) in star-forming galaxies, including both the systemic interstellar component originating from HII regions, and the multi-phase outflowing component associated with star-formation feedback. My thesis focuses on both the systemic and outflowing ISM in star-forming galaxies at redshift z ~ 1-4. With an unprecedented sample at z~1 with the rest-frame near-UV coverage, we examined how the kinematics of the warm and cool phrases of gas, probed by the interstellar CIV and low-ionization features, respectively, relate to each other. The spectral properties of CIV strongly correlate with the current star-formation rate, indicating a distinct nature of highly-ionized outflowing gas being driven by massive star formation. Additionally, we used the same set of z~1 galaxies to study the properties of the systemic ISM in HII regions by analyzing the nebular CIII] emission. CIII] emission tends to be stronger in lower-mass, bluer, and fainter galaxies with lower metallicity, suggesting that the strong CIII] emitters at lower redshifts can be ideal analogs of young, bursty galaxies at z > 6, which are possibly responsible for reionizing the universe. We are currently investigating the redshift evolution of the neutral, circumgalactic gas in a sample of ~1100 Lyman Break Galaxies at z ~ 2-4. The negative correlation between Lya emission and low-ionization interstellar absorption line strengths appears to be universal across different redshifts, but the fine-structure line emitting regions are found to be more compact for higher-redshift galaxies. With the detailed observational constraints provided by the rest-UV and rest-optical spectroscopy, our study sheds light on how the interstellar and circumgalactic gas components and different phases of gas connect to each other, and therefore provides a comprehensive picture of the overall

  5. Probing star formation and feedback in dwarf galaxies. Integral field view of the blue compact galaxy Tololo 1937-423

    NASA Astrophysics Data System (ADS)

    Cairós, L. M.; González-Pérez, J. N.

    2017-12-01

    Context. Blue compact galaxies (BCG) are gas-rich, low-mass, small systems that form stars at unusually high rates. This makes them excellent laboratories for investigating the process of star-formation (SF) at galactic scales and the effects of massive stellar feedback on the interstellar (and intergalactic) medium. Aims: We analyzed the BCG Tololo 1937-423 using optical integral field spectroscopy to probe its morphology, stellar content, nebular excitation and ionization properties, and the kinematics of its warm ionized gas. Methods: Tololo 1937-423 was observed with the Visible Multi-Object Spectrograph at the Very Large Telescope. We took data in the wavelength range 4150-7400 Å, covering a field of view of 27″× 27″ on the sky with a spatial sampling of 0.̋67. From these data we built maps in the continuum and brighter emission lines, diagnostic line ratio maps, and velocity dispersion fields. We also generated the integrated spectrum of the main H II regions and young stellar clusters to determine reliable physical parameters and oxygen abundances. Results: We found that Tololo 1937-423 is currently undergoing an extended starburst. In the Hα maps we identified nine major clumps, aligned mostly northeast-southwest, and stretching to galactocentric distances ≥2 kpc. The galaxy presents a single continuum peak that is not cospatial with any knot in emission lines, indicating at least two relatively recent episodes of SF. The inhomogeneous dust distribution reachs its maximum (E(B-V) 0.97) roughly at the position of the continuum peak. We found shocked regions in the galaxy outer regions and at the edges of the SF knots. The oxygen abundance, 12 + log(O/H) 8.20 ± 0.1, is similar in all the SF regions, suggesting a chemically homogeneous ionized interstellar medium over spatial scales of several kpc. The ionized gas kinematics displays an overall regular rotation around a northwest-southeast axis, with a maximum velocity of 70 ± 7 km s-1. Conclusions

  6. Galaxy interactions in compact groups - II. Abundance and kinematic anomalies in HCG 91c

    NASA Astrophysics Data System (ADS)

    Vogt, Frédéric P. A.; Dopita, Michael A.; Borthakur, Sanchayeeta; Verdes-Montenegro, Lourdes; Heckman, Timothy M.; Yun, Min S.; Chambers, Kenneth C.

    2015-07-01

    Galaxies in Hickson Compact Group 91 (HCG 91) were observed with the WiFeS integral field spectrograph as part of our ongoing campaign targeting the ionized gas physics and kinematics inside star-forming members of compact groups. Here, we report the discovery of H II regions with abundance and kinematic offsets in the otherwise unremarkable star-forming spiral HCG 91c. The optical emission line analysis of this galaxy reveals that at least three H II regions harbour an oxygen abundance ˜0.15 dex lower than expected from their immediate surroundings and from the abundance gradient present in the inner regions of HCG 91c. The same star-forming regions are also associated with a small kinematic offset in the form of a lag of 5-10 km s-1 with respect to the local circular rotation of the gas. H I observations of HCG 91 from the Very Large Array and broad-band optical images from Pan-STARRS (Panoramic Survey Telescope And Rapid Response System) suggest that HCG 91c is caught early in its interaction with the other members of HCG 91. We discuss different scenarios to explain the origin of the peculiar star-forming regions detected with WiFeS, and show that evidence points towards infalling and collapsing extraplanar gas clouds at the disc-halo interface, possibly as a consequence of long-range gravitational perturbations of HCG 91c from the other group members. As such, HCG 91c provides evidence that some of the perturbations possibly associated with the early phase of galaxy evolution in compact groups impact the star-forming disc locally, and on sub-kpc scales.

  7. KEPLER OBSERVATIONS OF THE SEYFERT 1 GALAXY II ZW 229.015

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carini, M. T.; Ryle, Wesley T., E-mail: mike.carini@wku.edu

    2012-04-10

    The Seyfert 1 galaxy II ZW 229.015 has been observed with the Kepler spacecraft since quarter 4 of Kepler science operations. The results of the quarters 4-7 (1 year) Kepler observations are presented in this paper. We find the source to be highly variable on multiple timescales, with discrete variations occurring on timescales as short as tens of hours with amplitudes as small as 0.5%. Such small amplitude, rapid variability has never before been detected in active galactic nuclei. The presence of a strong galaxy component dilutes the variability determined from the photometric aperture used in the standard Kepler PDCmore » analysis. Using the tools provided by the Kepler Guest Observer Office and simultaneous V-band photometry found in the literature, we determine an optimal customized aperture for photometry of this source with Kepler. The results of a PSRESP analysis reveal tentative evidence of a characteristic variability timescale in the power spectrum. Using this timescale, we estimate the mass of the central supermassive black hole and this estimate is consistent with the virial mass estimate from reverberation mapping studies.« less

  8. “Direct” Gas-phase Metallicity in Local Analogs of High-redshift Galaxies: Empirical Metallicity Calibrations for High-redshift Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Bian, Fuyan; Kewley, Lisa J.; Dopita, Michael A.

    2018-06-01

    We study the direct gas-phase oxygen abundance using the well-detected auroral line [O III]λ4363 in the stacked spectra of a sample of local analogs of high-redshift galaxies. These local analogs share the same location as z ∼ 2 star-forming galaxies on the [O III]λ5007/Hβ versus [N II]λ6584/Hα Baldwin–Phillips–Terlevich diagram. This type of analog has the same ionized interstellar medium (ISM) properties as high-redshift galaxies. We establish empirical metallicity calibrations between the direct gas-phase oxygen abundances (7.8< 12+{log}({{O}}/{{H}})< 8.4) and the N2 (log([N II]λ6584/Hα))/O3N2 (log(([O III]λ5007/Hβ)/([N II]λ6584/Hα))) indices in our local analogs. We find significant systematic offsets between the metallicity calibrations for our local analogs of high-redshift galaxies and those derived from the local H II regions and a sample of local reference galaxies selected from the Sloan Digital Sky Survey (SDSS). The N2 and O3N2 metallicities will be underestimated by 0.05–0.1 dex relative to our calibration, if one simply applies the local metallicity calibration in previous studies to high-redshift galaxies. Local metallicity calibrations also cause discrepancies of metallicity measurements in high-redshift galaxies using the N2 and O3N2 indicators. In contrast, our new calibrations produce consistent metallicities between these two indicators. We also derive metallicity calibrations for R23 (log(([O III]λλ4959,5007+[O II]λλ3726,3729)/Hβ)), O32(log([O III]λλ4959,5007/[O II]λλ3726,3729)), {log}([O III]λ5007/Hβ), and log([Ne III]λ3869/[O II]λ3727) indices in our local analogs, which show significant offset compared to those in the SDSS reference galaxies. By comparing with MAPPINGS photoionization models, the different empirical metallicity calibration relations in the local analogs and the SDSS reference galaxies can be shown to be primarily due to the change of ionized ISM conditions. Assuming that temperature structure

  9. High chemical abundances in stripped Virgo spiral galaxies

    NASA Technical Reports Server (NTRS)

    Skillman, E. D.; Kennicutt, R. C.; Shields, G. A.

    1993-01-01

    Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).

  10. Fundamental properties of Fanaroff-Riley type II radio galaxies investigated via Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Kapińska, A. D.; Uttley, P.; Kaiser, C. R.

    2012-08-01

    Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large-scale structure. We explore the intrinsic and extrinsic properties of the population of Fanaroff-Riley type II (FR II) objects, i.e. their kinetic luminosities, lifetimes and the central densities of their environments. In particular, the radio and kinetic luminosity functions of these powerful radio sources are investigated using the complete, flux-limited radio catalogues of the Third Cambridge Revised Revised Catalogue (3CRR) and Best et al. We construct multidimensional Monte Carlo simulations using semi-analytical models of FR II source time evolution to create artificial samples of radio galaxies. Unlike previous studies, we compare radio luminosity functions found with both the observed and simulated data to explore the best-fitting fundamental source parameters. The new Monte Carlo method we present here allows us to (i) set better limits on the predicted fundamental parameters of which confidence intervals estimated over broad ranges are presented and (ii) generate the most plausible underlying parent populations of these radio sources. Moreover, as has not been done before, we allow the source physical properties (kinetic luminosities, lifetimes and central densities) to co-evolve with redshift, and we find that all the investigated parameters most likely undergo cosmological evolution. Strikingly, we find that the break in the kinetic luminosity function must undergo redshift evolution of at least (1 + z)3. The fundamental parameters are strongly degenerate, and independent constraints are necessary to draw more precise conclusions. We use the estimated kinetic luminosity functions to set constraints on the duty cycles of these powerful radio sources. A comparison of the duty cycles of powerful FR IIs with those determined from radiative luminosities of active galactic nuclei of

  11. LOSS Revisited. II. The Relative Rates of Different Types of Supernovae Vary between Low- and High-mass Galaxies

    NASA Astrophysics Data System (ADS)

    Graur, Or; Bianco, Federica B.; Modjaz, Maryam; Shivvers, Isaac; Filippenko, Alexei V.; Li, Weidong; Smith, Nathan

    2017-03-01

    In Paper I of this series, we showed that the ratio between stripped-envelope (SE) supernova (SN) and Type II SN rates reveals a significant SE SN deficiency in galaxies with stellar masses ≲ {10}10 {M}⊙ . Here, we test this result by splitting the volume-limited subsample of the Lick Observatory Supernova Search (LOSS) SN sample into low- and high-mass galaxies and comparing the relative rates of various SN types found in them. The LOSS volume-limited sample contains 180 SNe and SN impostors and is complete for SNe Ia out to 80 Mpc and core-collapse SNe out to 60 Mpc. All of these transients were recently reclassified by us in Shivvers et al. We find that the relative rates of some types of SNe differ between low- and high-mass galaxies: SNe Ib and Ic are underrepresented by a factor of ˜3 in low-mass galaxies. These galaxies also contain the only examples of SN 1987A-like SNe in the sample and host about nine times as many SN impostors. Normal SNe Ia seem to be ˜30% more common in low-mass galaxies, making these galaxies better sources for homogeneous SN Ia cosmology samples. The relative rates of SNe IIb are consistent in both low- and high-mass galaxies. The same is true for broad-line SNe Ic, although our sample includes only two such objects. The results presented here are in tension with a similar analysis from the Palomar Transient Factory, especially as regards SNe IIb.

  12. Dynamics of Galaxies

    NASA Astrophysics Data System (ADS)

    Bertin, Giuseppe

    2000-08-01

    Part I. Basic Phenomenology: 1. Scales; 2. Observational windows; 3. Classifications; 4. Photometry, kinematics, dark matter; 5. Basic questions, semi-empirical approach, dynamical window; Part II. Physical Models: 6. Self-gravity and relation with plasma physics; 7. Relaxation times, absence of thermodynamical equilibrium; 8. Models; 9. Equilibrium and stability: symmetry and symmetry breaking; 10. Classical ellipsoids; 11. Introduction to dispersive waves; 12. Jeans instability; Part III. Spiral Galaxies: 13. Orbits; 14. The basic state: vertical and horizontal equilibrium in the disk; 15. Density waves; 16. Role of gas; 17. Global spiral modes; 18. Spiral structure in galaxies; 19. Bending waves; 20. Dark matter in spiral galaxies; Part IV. Elliptical Galaxies: 21. Orbits; 22. Stellar dynamical approach; 23. Stability; 24. Dark matter in elliptical galaxies; Part V. In Perspective: 25. Selected aspects of formation and evolution; Notes; Index.

  13. Stellar feedback in galaxies and the origin of galaxy-scale winds

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Quataert, Eliot; Murray, Norman

    2012-04-01

    Feedback from massive stars is believed to play a critical role in driving galactic super-winds that enrich the intergalactic medium and shape the galaxy mass function, mass-metallicity relation and other global galaxy properties. In previous papers, we have introduced new numerical methods for implementing stellar feedback on sub-giant molecular cloud (sub-GMC) through galactic scales in numerical simulations of galaxies; the key physical processes include radiation pressure in the ultraviolet through infrared, supernovae (Type I and Type II), stellar winds ('fast' O star through 'slow' asymptotic giant branch winds), and H II photoionization. Here, we show that these feedback mechanisms drive galactic winds with outflow rates as high as ˜10-20 times the galaxy star formation rate. The mass-loading efficiency (wind mass-loss rate divided by the star formation rate) scales roughly as ? (where Vc is the galaxy circular velocity), consistent with simple momentum-conservation expectations. We use our suite of simulations to study the relative contribution of each feedback mechanism to the generation of galactic winds in a range of galaxy models, from Small Magellanic Cloud like dwarfs and Milky Way (MW) analogues to z˜ 2 clumpy discs. In massive, gas-rich systems (local starbursts and high-z galaxies), radiation pressure dominates the wind generation. By contrast, for MW-like spirals and dwarf galaxies the gas densities are much lower and sources of shock-heated gas such as supernovae and stellar winds dominate the production of large-scale outflows. In all of our models, however, the winds have a complex multiphase structure that depends on the interaction between multiple feedback mechanisms operating on different spatial scales and time-scales: any single feedback mechanism fails to reproduce the winds observed. We use our simulations to provide fitting functions to the wind mass loading and velocities as a function of galaxy properties, for use in cosmological

  14. Intrinsic alignments of galaxies in the MassiveBlack-II simulation: analysis of two-point statistics

    NASA Astrophysics Data System (ADS)

    Tenneti, Ananth; Singh, Sukhdeep; Mandelbaum, Rachel; di Matteo, Tiziana; Feng, Yu; Khandai, Nishikanta

    2015-04-01

    The intrinsic alignment of galaxies with the large-scale density field is an important astrophysical contaminant in upcoming weak lensing surveys. We present detailed measurements of the galaxy intrinsic alignments and associated ellipticity-direction (ED) and projected shape (wg+) correlation functions for galaxies in the cosmological hydrodynamic MassiveBlack-II simulation. We carefully assess the effects on galaxy shapes, misalignment of the stellar component with the dark matter shape and two-point statistics of iterative weighted (by mass and luminosity) definitions of the (reduced and unreduced) inertia tensor. We find that iterative procedures must be adopted for a reliable measurement of the reduced tensor but that luminosity versus mass weighting has only negligible effects. Both ED and wg+ correlations increase in amplitude with subhalo mass (in the range of 1010-6.0 × 1014 h-1 M⊙), with a weak redshift dependence (from z = 1 to 0.06) at fixed mass. At z ˜ 0.3, we predict a wg+ that is in reasonable agreement with Sloan Digital Sky Survey luminous red galaxy measurements and that decreases in amplitude by a factor of ˜5-18 for galaxies in the Large Synoptic Survey Telescope survey. We also compared the intrinsic alignments of centrals and satellites, with clear detection of satellite radial alignments within their host haloes. Finally, we show that wg+ (using subhaloes as tracers of density) and wδ+ (using dark matter density) predictions from the simulations agree with that of non-linear alignment (NLA) models at scales where the two-halo term dominates in the correlations (and tabulate associated NLA fitting parameters). The one-halo term induces a scale-dependent bias at small scales which is not modelled in the NLA model.

  15. The Rise and Fall of Star Formation Histories of Blue Galaxies at Redshifts 0.2 < z < 1.4

    NASA Technical Reports Server (NTRS)

    Pacifici, Camilla; Kassin, Susan A.; Weiner, Benjamin; Charlot, Stephane; Gardner, Jonathan P.

    2012-01-01

    Popular cosmological scenarios predict that galaxies form hierarchically from the merger of many progenitor, each with their own unique star formation history (SFH). We use the approach recently developed by Pacifici et al. to constrain the SFHs of 4517 blue (presumably star-forming) galaxies with spectroscopic redshifts in the range O.2 < z < 1:4 from the All-Wavelength Extended Groth Strip International Survey (AEGIS). This consists in the Bayesian analysis of the observed galaxy spectral ' energy distributions with a comprehensive library of synthetic spectra assembled using state-of-the-art models of star formation and chemical enrichment histories, stellar population synthesis, nebular emission and attenuation by dust. We constrain the SFH of each galaxy in our sample by comparing the observed fluxes in the B, R,l and K(sub s) bands and rest-frame optical emission-line luminosities with those of one million model spectral energy distributions. We explore the dependence of the resulting SFH on galaxy stellar mass and redshift. We find that the average SFHs of high-mass galaxies rise and fall in a roughly symmetric bell-shaped manner, while those of low-mass galaxies rise progressively in time, consistent with the typically stronger activity of star formation in low-mass compared to high-mass galaxies. For galaxies of all masses, the star formation activity rises more rapidly at high than at low redshift. These findings imply that the standard approximation of exponentially declining SFHs wIdely used to interpret observed galaxy spectral energy distributions is not appropriate to constrain the physical parameters of star-forming galaxies at intermediate redshifts.

  16. A Redshift Survey of IRAS Galaxies. II. Methods for Determining Self-consistent Velocity and Density Fields: Erratum

    NASA Astrophysics Data System (ADS)

    Yahil, Amos; Strauss, Michael A.; Davis, Marc; Huchra, John P.

    1991-11-01

    In the paper, "A Redshift Survey of IRAS Galaxies. II. Methods for Determining Self-consistent Velocity and Density Fields" by Amos Yahil, Michael A. Strauss, Marc Davis, and John P. Huchra (ApJ, 372,380 [1991]), Figures 14 and 15 were presented out of order, with their legends reversed. Thus, the figure at the bottom of page 391 is Figure 15, and should have the legend: "Fig. 15.-As in Fig. 13, for the method 3 results." The figure at the top of page 392 is Figure 14, and should have the legend: "Fig. 14.-Plot in Galactic coordinates of the quantity V_diff_ for galaxies within 3000 km s^-1^ of the LG. The symbol size is proportional to V_diff_ - 400 km s^-1^, which measures the deviation of the redshift- distance relation along the line of sight to that galaxy from pure Hubble flow."

  17. H I OBSERVATIONS OF THE Ca II ABSORBING GALAXIES Mrk 1456 AND SDSS J211701.26-002633.7

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cherinka, B.; Schulte-Ladbeck, R. E.; Rosenberg, J. L.

    2009-12-15

    In an effort to study Damped Ly{alpha} (DLA) galaxies at low redshift, we have been using the Sloan Digital Sky Survey (SDSS) to identify galaxies projected onto quasi-stellar object (QSO) sight lines and to characterize their optical properties. For low-redshift galaxies, the H I 21 cm emission line can be used as an alternate tool for identifying possible DLA galaxies, since H I-emitting galaxies typically exhibit H I columns that are larger than the classical DLA limit. Here, we report on follow-up H I 21 cm emission-line observations of two DLA candidates that are both low-redshift spiral galaxies, Mrk 1456more » and SDSS J211701.26-002633.7. The observations were made using the Green Bank Telescope (GBT) and Arecibo telescope, respectively. Analysis of their H I properties reveal the galaxies to be about one and two M*{sub HI} galaxies, respectively, and to have average H I mass, gas richness, and gas-mass fraction for their morphological types. We consider Mrk 1456 and SDSS J211701.26-002633.7 to be candidate DLA systems based upon the strength of the Ca II absorption lines they cause in their QSO's spectra, and impact parameters to the QSO that are smaller than the stellar disk. Compared to the small numbers of other H I detected DLA and candidate DLA galaxies, Mrk 1456 and SDSS J211701.26-002633.7 have high H I masses. Mrk 1456 and SDSS J211701.26-002633.7 have also been found to lie in galaxy groups that are high in H I gas mass compared to the group containing SBS 1543+593, the only DLA galaxy previously known to be situated in a galaxy group. When compared with the expected properties of low-z DLAs from an H I-detected sample of galaxies, Mrk 1456 and SDSS J211701.26-002633.7 fall within the ranges for impact parameter and M{sub B} ; and the H I mass distribution for the H I-detected DLAs agrees with that of the expected H I mass distribution for low-z DLAs. Our observations support galaxy-evolution models in which high-mass galaxies make up an

  18. Morphology Dependence of Stellar Age in Quenched Galaxies at Redshift ˜1.2: Massive Compact Galaxies Are Older than More Extended Ones

    NASA Astrophysics Data System (ADS)

    Williams, Christina C.; Giavalisco, Mauro; Bezanson, Rachel; Cappelluti, Nico; Cassata, Paolo; Liu, Teng; Lee, Bomee; Tundo, Elena; Vanzella, Eros

    2017-04-01

    We report the detection of morphology-dependent stellar age in massive quenched galaxies (QGs) at z ˜ 1.2. The sense of the dependence is that compact QGs are 0.5-2 Gyr older than normal-sized ones. The evidence comes from three different age indicators—{D}n4000, {{{H}}}δ , and fits to spectral synthesis models—applied to their stacked optical spectra. All age indicators consistently show that the stellar populations of compact QGs are older than those of their normal-sized counterparts. We detect weak [O II] emission in a fraction of QGs, and the strength of the line, when present, is similar between the two samples; however, compact galaxies exhibit a significantly lower frequency of [O II] emission than normal ones. Fractions of both samples are individually detected in 7 Ms Chandra X-ray images (luminosities ˜1040-1041 erg s-1). The 7 Ms stacks of nondetected galaxies show similarly low luminosities in the soft band only, consistent with a hot gas origin for the X-ray emission. While both [O II] emitters and nonemitters are also X-ray sources among normal galaxies, no compact galaxy with [O II] emission is an X-ray source, arguing against an active galactic nucleus (AGN) powering the line in compact galaxies. We interpret the [O II] properties as further evidence that compact galaxies are older and further along in the process of quenching star formation and suppressing gas accretion. Finally, we argue that the older age of compact QGs is evidence of progenitor bias: compact QGs simply reflect the smaller sizes of galaxies at their earlier quenching epoch, with stellar density most likely having nothing directly to do with cessation of star formation.

  19. Effects of Pop III to PopII transition on the lowest metallicity stars in dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Zhang, Yimiao; Keres, Dusan; FIRE Team

    2018-01-01

    We examine the effects of the enrichments from Population III (Pop III) stars on the formation and properties of the first generation of the Population II (Pop II) stars. Pop III stars begin to transition towards Pop II stars when the metals dispersed in Pop III supernovae pollute the nearby gas. However, details of this transition are still largely unknown. We use dwarf galaxy simulations from the Feedback In Realistic Environments (FIRE) project to identify the star-forming gas that is likely to be pre-enriched by Pop III supernovae and follow the stars that form in such gas. This pre-enrichment will leave the signature in the lowest metallicity stars that can be used to better constrain the details of the Pop III-to-Pop II transition.

  20. Baryonic distributions in galaxy dark matter haloes - II. Final results

    NASA Astrophysics Data System (ADS)

    Richards, Emily E.; van Zee, L.; Barnes, K. L.; Staudaher, S.; Dale, D. A.; Braun, T. T.; Wavle, D. C.; Dalcanton, J. J.; Bullock, J. S.; Chandar, R.

    2018-06-01

    Re-creating the observed diversity in the organization of baryonic mass within dark matter haloes represents a key challenge for galaxy formation models. To address the growth of galaxy discs in dark matter haloes, we have constrained the distribution of baryonic and non-baryonic matter in a statistically representative sample of 44 nearby galaxies defined from the Extended Disk Galaxy Exploration Science (EDGES) Survey. The gravitational potentials of each galaxy are traced using rotation curves derived from new and archival radio synthesis observations of neutral hydrogen (H I). The measured rotation curves are decomposed into baryonic and dark matter halo components using 3.6 μm images for the stellar content, the H I observations for the atomic gas component, and, when available, CO data from the literature for the molecular gas component. The H I kinematics are supplemented with optical integral field spectroscopic (IFS) observations to measure the central ionized gas kinematics in 26 galaxies, including 13 galaxies that are presented for the first time in this paper. Distributions of baryonic-to-total mass ratios are determined from the rotation curve decompositions under different assumptions about the contribution of the stellar component and are compared to global and radial properties of the dominant stellar populations extracted from optical and near-infrared photometry. Galaxies are grouped into clusters of similar baryonic-to-total mass distributions to examine whether they also exhibit similar star and gas properties. The radial distribution of baryonic-to-total mass in a galaxy does not appear to correlate with any characteristics of its star formation history.

  1. Star Formation Rate Distribution in the Galaxy NGC 1232

    NASA Astrophysics Data System (ADS)

    Araújo de Souza, Alexandre; Martins, Lucimara P.; Rodríguez-Ardila, Alberto; Fraga, Luciano

    2018-06-01

    NGC 1232 is a face-on spiral galaxy and a great laboratory for the study of star formation due to its proximity. We obtained high spatial resolution Hα images of this galaxy, with adaptive optics, using the SAM instrument at the SOAR telescope, and used these images to study its H II regions. These observations allowed us to produce the most complete H II region catalog for it to date, with a total of 976 sources. This doubles the number of H II regions previously found for this object. We used these data to construct the H II luminosity function, and obtained a power-law index lower than the typical values found for Sc galaxies. This shallower slope is related to the presence of a significant number of high-luminosity H II regions (log L > 39 dex). We also constructed the size distribution function, verifying that, as for most galaxies, NGC 1232 follows an exponential law. We also used the Hα luminosity to calculate the star formation rate. An extremely interesting fact about this galaxy is that X-ray diffuse observations suggest that NGC 1232 recently suffered a collision with a dwarf galaxy. We found an absence of star formation around the region where the X-ray emission is more intense, which we interpret as a star formation quenching due to the collision. Along with that, we found an excess of star-forming regions in the northeast part of the galaxy, where the X-ray emission is less intense.

  2. Spatially resolved galactic wind in lensed galaxy RCSGA 032727-132609

    NASA Astrophysics Data System (ADS)

    Bordoloi, Rongmon; Rigby, Jane R.; Tumlinson, Jason; Bayliss, Matthew B.; Sharon, Keren; Gladders, Michael G.; Wuyts, Eva

    2016-05-01

    We probe the spatial distribution of outflowing gas along four lines of sight separated by up to 6 kpc in a gravitationally lensed star-forming galaxy at z = 1.70. Using Mg II and Fe II emission and absorption as tracers, we find that the clumps of star formation are driving galactic outflows with velocities of -170 to -250 km s-1. The velocities of Mg II emission are redshifted with respect to the systemic velocities of the galaxy, consistent with being back-scattered. By contrast, the Fe II fluorescent emission lines are either slightly blueshifted or at the systemic velocity of the galaxy. Taken together, the velocity structure of the Mg II and Fe II emission is consistent with arising through scattering in galactic winds. Assuming a thin shell geometry for the outflowing gas, the estimated masses carried out by these outflows are large (≳30-50 M⊙ yr- 1), with mass loading factors several times the star formation rate. Almost 20 per cent to 50 per cent of the blueshifted absorption probably escapes the gravitational potential of the galaxy. In this galaxy, the outflow is `locally sourced', that is, the properties of the outflow in each line of sight are dominated by the properties of the nearest clump of star formation; the wind is not global to the galaxy. The mass outflow rates and the momentum flux carried out by outflows in individual star-forming knots of this object are comparable to that of starburst galaxies in the local Universe.

  3. Spatially Resolved Galactic Wind in Lensed Galaxy RCSGA 032727-132609

    NASA Technical Reports Server (NTRS)

    Bordoloi, Rongmon; Rigby, Jane R.; Tumlinson, Janson; Bayliss, Matthew B.; Sharon, Keren; Gladders, Michael G.; Wuyts, Eva

    2016-01-01

    We probe the spatial distribution of outflowing gas along four lines of sight separated by up to 6 kpc in a gravitationally lensed star-forming galaxy at z = 1.70. Using Mg II and Fe II emission and absorption as tracers, we find that the clumps of star formation are driving galactic outflows with velocities of - 170 to - 250 km/s. The velocities of Mg II emission are redshifted with respect to the systemic velocities of the galaxy, consistent with being backscattered. By contrast, the Fe II fluorescent emission lines are either slightly blueshifted or at the systemic velocity of the galaxy. Taken together, the velocity structure of the Mg II and Fe II emission is consistent with arising through scattering in galactic winds. Assuming a thin shell geometry for the outflowing gas, the estimated masses carried out by these outflows are large (approx 30-50 M/yr), with mass loading factors several times the star formation rate. Almost 20 per cent to 50 per cent of the blueshifted absorption probably escapes the gravitational potential of the galaxy. In this galaxy, the outflow is 'locally sourced', that is, the properties of the outflow in each line of sight are dominated by the properties of the nearest clump of star formation; the wind is not global to the galaxy. The mass outflow rates and the momentum flux carried out by outflows in individual star-forming knots of this object are comparable to that of starburst galaxies in the local Universe.

  4. HERSCHEL SPECTROSCOPIC OBSERVATIONS OF LITTLE THINGS DWARF GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cigan, Phil; Young, Lisa; Cormier, Diane

    We present far-infrared (FIR) spectral line observations of five galaxies from the Little Things sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data extend the observed parameter space into the regime of low surface brightness dwarf galaxies with low metallicities and moderate star formation rates. Our targets were observed with Herschel at the [C ii] 158 μm, [O i] 63 μm, [O iii] 88 μm, and [N ii] 122 μm emission lines using the PACS Spectrometer. These high-resolution maps allow usmore » for the first time to study the FIR properties of these systems on the scales of larger star-forming complexes. The spatial resolution in our maps, in combination with star formation tracers, allows us to identify separate photodissociation regions (PDRs) in some of the regions we observed. Our systems have widespread [C ii] emission that is bright relative to continuum, averaging near 0.5% of the total infrared (TIR) budget—higher than in solar-metallicity galaxies of other types. [N ii] is weak, suggesting that the [C ii] emission in our galaxies comes mostly from PDRs instead of the diffuse ionized interstellar medium (ISM). These systems exhibit efficient cooling at low dust temperatures, as shown by ([O i]+[C ii])/TIR in relation to 60 μm/100 μm, and low [O i]/[C ii] ratios which indicate that [C ii] is the dominant coolant of the ISM. We observe [O iii]/[C ii] ratios in our galaxies that are lower than those published for other dwarfs, but similar to levels noted in spirals.« less

  5. The Sloan Lens ACS Survey. I. A Large Spectroscopically Selected Sample of Massive Early-Type Lens Galaxies

    NASA Technical Reports Server (NTRS)

    Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Moustakas, Leonidas A.

    2006-01-01

    The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple nebular emission lines at a redshift significantly higher than that of the SDSS target galaxy. The SLACS survey is optimized to detect bright early-type lens galaxies with faint lensed sources in order to increase the sample of known gravitational lenses suitable for detailed lensing, photometric, and dynamical modeling. In this paper, the first in a series on the current results of our HST Cycle 13 imaging survey, we present a catalog of 19 newly discovered gravitational lenses, along with nine other observed candidate systems that are either possible lenses, nonlenses, or nondetections. The survey efficiency is thus >=68%. We also present Gemini 8 m and Magellan 6.5 m integral-field spectroscopic data for nine of the SLACS targets, which further support the lensing interpretation. A new method for the effective subtraction of foreground galaxy images to reveal faint background features is presented. We show that the SLACS lens galaxies have colors and ellipticities typical of the spectroscopic parent sample from which they are drawn (SDSS luminous red galaxies and quiescent MAIN sample galaxies), but are somewhat brighter and more centrally concentrated. Several explanations for the latter bias are suggested. The SLACS survey provides the first statistically significant and homogeneously selected sample of bright early-type lens galaxies, furnishing a powerful probe of the structure of early-type galaxies within the half-light radius. The high confirmation rate of lenses in the SLACS survey suggests consideration of spectroscopic lens discovery as an explicit science goal of future spectroscopic galaxy surveys.

  6. Galaxy gas as obscurer - II. Separating the galaxy-scale and nuclear obscurers of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Buchner, Johannes; Bauer, Franz E.

    2017-03-01

    The 'torus' obscurer of active galactic nuclei (AGN) is poorly understood in terms of its density, sub-structure and physical mechanisms. Large X-ray surveys provide model boundary constraints, for both Compton-thin and Compton-thick levels of obscuration, as obscured fractions are mean covering factors fcov. However, a major remaining uncertainty is host-galaxy obscuration. In Paper I, we discovered a relation of {NH} ∝ M_{star }^{1/3} for the obscuration of galaxy-scale gas. Here, we apply this observational relation to the AGN population, and find that galaxy-scale gas is responsible for a luminosity-independent fraction of Compton-thin AGN, but does not produce Compton-thick columns. With the host-galaxy obscuration understood, we present a model of the remaining nuclear obscurer, which is consistent with a range of observations. Our radiation-lifted torus model consists of a Compton-thick component (fcov ∼ 35 per cent) and a Compton-thin component (fcov ∼ 40 per cent), which depends on both black hole mass and luminosity. This provides a useful summary of observational constraints for torus modellers who attempt to reproduce this behaviour. It can also be employed as a sub-grid recipe in cosmological simulations that do not resolve the torus. We also investigate host-galaxy X-ray obscuration inside cosmological, hydrodynamic simulations (Evolution and Assembly of Galaxies and their Environment; Illustris). The obscuration from ray-traced galaxy gas can agree with observations, but is highly sensitive to the chosen feedback assumptions.

  7. Ca II and Na I absorption in the QSO S4 0248 + 430 due to an intervening galaxy

    NASA Technical Reports Server (NTRS)

    Womble, Donna S.; Junkkarinen, Vesa T.; Cohen, Ross D.; Burbidge, E. Margaret

    1990-01-01

    Observations of the QSO S4 0248 + 430 and a nearby anonymous galaxy are presented. Two absorption components are found in both Ca II H and K and Na I D1 and D2 at z(a) = 0.0515, 0.0523. Column densities of log N(Ca II) = 13.29, 13.50, and log N(Na I) = 13.79, 14.18 are found for z(a) = 0.0515, 0.0523 absorption systems, respectively. The column density ratios imply considerable calcium depletion and disk-type absorbing gas. At least one and possibly both absorption components are produced by high-velocity gas. A broadband image of the field shows an asymmetrical armlike feature or possible tidal tail covering and extending past the position of the QSO. The presence of this extended feature and the apparent difference between the absorption velocities and galaxy rotation velocity suggest that the absorbing gas is not ordinary disk gas, but rather is a result of tidal disruption.

  8. Reconstructing the galaxy density field with photometric redshifts - II. Environment-dependent galaxy evolution since z ≃ 3

    NASA Astrophysics Data System (ADS)

    Malavasi, Nicola; Pozzetti, Lucia; Cucciati, Olga; Bardelli, Sandro; Ilbert, Olivier; Cimatti, Andrea

    2017-09-01

    Although extensively investigated, the role of the environment in galaxy formation is still not well understood. In this context, the galaxy stellar mass function (GSMF) is a powerful tool to understand how environment relates to galaxy mass assembly and the quenching of star formation. In this work, we make use of the high-precision photometric redshifts of the UltraVISTA Survey to study the GSMF in different environments up to z ˜ 3, on physical scales from 0.3 to 2 Mpc, down to masses of M ˜ 1010 M⊙. We witness the appearance of environmental signatures for both quiescent and star-forming galaxies. We find that the shape of the GSMF of quiescent galaxies is different in high- and low-density environments up to z ˜ 2 with the high-mass end (M ≳ 1011 M⊙) being enhanced in high-density environments. On the contrary, for star-forming galaxies, a difference between the GSMF in high- and low-density environments is present for masses M ≲ 1011 M⊙. Star-forming galaxies in this mass range appear to be more frequent in low-density environments up to z < 1.5. Differences in the shape of the GSMF are not visible anymore at z > 2. Our results, in terms of general trends in the shape of the GSMF, are in agreement with a scenario in which galaxies are quenched when they enter hot gas-dominated massive haloes that are preferentially in high-density environments.

  9. A study of star formation by Hα emission of galaxies in the galaxy group NGC 4213

    NASA Astrophysics Data System (ADS)

    Maungkorn, Sakdawoot; Kriwattanawong, Wichean

    2017-09-01

    This research aims to study hydrogen alpha emission, corresponding to star formation of galaxies in the NGC 4213 group that has an average recession velocity of 6,821 km/s. The imaging observations with broad-band filters (B, V and RC) and narrow-band filters ([S II] and Red-continuum) were carried out from the 2.4-m reflecting telescope at Thai National Observatory (TNO). There are 11 sample galaxies in this study, consisting of 2 elliptical, 2 lenticular and 7 spiral galaxies. It was found that the late-type galaxies tend to be bluer than early-type galaxies, due to these galaxies consist of relatively high proportion of blue stars. Furthermore, the equivalent width of hydrogen alpha (EW(Hα)) tends to increase as a function of morphological type. This indicates that star formation in late-type galaxies taking place more than the early-type galaxies. Furthermore, a ratio of the star formation rate to galaxy mass also increases slightly with the galaxy type. This could be due to the interaction between galaxy-galaxy or tidal interaction occurring within the galaxy group.

  10. The chemical abundances of the stellar populations in the Leo I and II dSph galaxies

    NASA Astrophysics Data System (ADS)

    Bosler, Tammy L.; Smecker-Hane, Tammy A.; Stetson, Peter B.

    2007-06-01

    We have obtained calcium abundances and radial velocities for 102 red giant branch (RGB) stars in the Leo I dwarf spheroidal galaxy (dSph) and 74 RGB stars in the Leo II dSph using the low-resolution spectrograph (LRIS) on the Keck I 10-m telescope. We report on the calcium abundances [Ca/H] derived from the strengths of the CaII triplet absorption lines at 8498, 8542 and 8662 Å in the stellar spectra using a new empirical CaII triplet calibration to [Ca/H]. The two galaxies have different average [Ca/H] values of -1.34 +/- 0.02 for Leo I and -1.65 +/- 0.02 for Leo II with intrinsic abundance dispersions of 1.2 and 1.0 dex, respectively. The typical random and total errors in derived abundances are 0.10 and 0.17 dex per star. For comparison to the existing literature, we also converted our CaII measurements to [Fe/H] on the scale of Carretta and Gratton (1997) though we discuss why this may not be the best determinant of metallicity; Leo I has a mean [Fe/H] = -1.34 and Leo II has a mean [Fe/H] = -1.59. The metallicity distribution function of Leo I is approximately Gaussian in shape with an excess at the metal-rich end, while that of Leo II shows an abrupt cut-off at the metal-rich end. The lower mean metallicity of Leo II is consistent with the fact that it has a lower luminosity, hence lower the total mass than Leo I; thus, the evolution of Leo II may have been affected more by mass lost in galactic winds. Our direct and independent measurement of the metallicity distributions in these dSph will allow a more accurate star-formation histories to be derived from future analysis of their colour-magnitude diagrams(CMDs). Data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. E

  11. On the [CII]-SFR Relation in High Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Vallini, L.; Gallerani, S.; Ferrara, A.; Pallottini, A.; Yue, B.

    2015-11-01

    After two Atacama Large Millimeter/submillimeter Array (ALMA) observing cycles, only a handful of [C ii] 158 μm emission line searches in z > 6 galaxies have reported a positive detection, questioning the applicability of the local [C ii]-star formation rate (SFR) relation to high-z systems. To investigate this issue we use the Vallini et al. (V13) model,based on high-resolution, radiative transfer cosmological simulations to predict the [C ii] emission from the interstellar medium of a z ≈ 7 (halo mass Mh = 1.17 × 1011 M⊙) galaxy. We improve the V13 model by including (a) a physically motivated metallicity (Z) distribution of the gas, (b) the contribution of photodissociation regions (PDRs), and (c) the effects of cosmic microwave background (CMB) on the [C ii] line luminosity. We study the relative contribution of diffuse neutral gas to the total [C ii] emission (Fdiff/Ftot) for different SFR and Z values. We find that the [C ii] emission arises predominantly from PDRs: regardless of the galaxy properties, Fdiff/Ftot ≤ 10%, since at these early epochs the CMB temperature approaches the spin temperature of the [C ii] transition in the cold neutral medium (TCMB ˜ {T}s{{CNM}} ˜ 20 K). Our model predicts a high-z [C ii]-SFR relation, consistent with observations of local dwarf galaxies (0.02 < Z/Z⊙ < 0.5). The [C ii] deficit suggested by actual data (LCii < 2.0 × 107 L⊙ in BDF3299 at z ≈ 7.1) if confirmed by deeper ALMA observations, can be ascribed to negative stellar feedback disrupting molecular clouds around star formation sites. The deviation from the local [C ii]-SFR would then imply a modified Kennicutt-Schmidt relation in z > 6 galaxies. Alternatively/in addition, the deficit might be explained by low gas metallicities (Z < 0.1 Z⊙).

  12. Peering Into an Early Galaxy

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2018-04-01

    reports on what weve learned peering into CR7s interior with ALMA.ALMA observations of [C II] (white contours) are overlaid on an ultraviolet image of the galaxy CR7 taken with Hubble (background image). The presence of [C II] throughout the galaxy indicate that CR7 does not primarily consist of metal-free gas, as had been previously proposed. [Matthee et al. 2017]Metals yet No Dust?Matthee and collaborators deep spectroscopic observations of CR7 targeted the far-infrared dust continuum emission and a gas emission line, [C II]. The authors detected [C II] emission in a large region in and around the galaxy, including near the ultraviolet clumps. This clearly indicates the presence of metals in these star-forming regions, and it rules out the possibility that CR7s gas is mostly primordial and forming metal-free Pop III stars.The authors do not detect far infrared continuum emission from dust, which sets an unusually low upper limit on the amount of dust that may be present in this galaxy. This limit allows them to better interpret their measurements of star formation rates in CR7, providing more information about the galaxys properties.Lastly, Matthee and collaborators note that the [C II] emission is detected in multiple different components that have different velocities. The authors propose that these components are accreting satellite galaxies. If this is correct, then CR7 is not only a target to learn about early sources of light in the universe its also a rare opportunity to directly witness the build-up of a central galaxy in the early universe.CitationJ. Matthee et al 2017 ApJ 851 145. doi:10.3847/1538-4357/aa9931

  13. Galaxies clustering around QSOs with z = 0.9-1.5 and the origin of blue field galaxies

    NASA Technical Reports Server (NTRS)

    Hintzen, Paul; Romanishin, W.; Valdes, Francisco

    1991-01-01

    Deep CCD images were obtained in Mould-Cousins R and I passbands of 16 radio quasars with z values between 0.9 and 1.5 and absolute values of b above 35 deg, chosen from the Veron-Cetty and Veron (1984) catalog. Results indicate that, in this population of radio quasars, there is a statistically significant excess of galaxies within 15 arcsec of the quasars and brighter than R = 23 and I = 22. However, contrary to the report of Tyson (1986), no excess was found of galaxies with R less than 21 lying within 30 arcsec of quasars in this redshift range. Data were also obtained for very blue galaxies seen among objects in the general field, all of which are bluer in R-I than Magellanic irregulars at any redshift less than 3. It is suggested that this population might be comprised of low-redshift low-luminosity (H II region) galaxies of the type studied by French (1980) and/or higher redshift galaxies with strong cooling flows and forbidden O II lines.

  14. Modeling Fe II Emission and Revised Fe II (UV) Empirical Templates for the Seyfert 1 Galaxy I Zw 1

    NASA Astrophysics Data System (ADS)

    Bruhweiler, F.; Verner, E.

    2008-03-01

    We use the narrow-lined broad-line region (BLR) of the Seyfert 1 galaxy, I Zw 1, as a laboratory for modeling the ultraviolet (UV) Fe II 2100-3050 Å emission complex. We calculate a grid of Fe II emission spectra representative of BLR clouds and compare them with the observed I Zw 1 spectrum. Our predicted spectrum for log [nH/(cm -3) ] = 11.0, log [ΦH/(cm -2 s-1) ] = 20.5, and ξ/(1 km s-1) = 20, using Cloudy and an 830 level model atom for Fe II with energies up to 14.06 eV, gives a better fit to the UV Fe II emission than models with fewer levels. Our analysis indicates (1) the observed UV Fe II emission must be corrected for an underlying Fe II pseudocontinuum; (2) Fe II emission peaks can be misidentified as that of other ions in active galactic nuclei (AGNs) with narrow-lined BLRs possibly affecting deduced physical parameters; (3) the shape of 4200-4700 Å Fe II emission in I Zw 1 and other AGNs is a relative indicator of narrow-line region (NLR) and BLR Fe II emission; (4) predicted ratios of Lyα, C III], and Fe II emission relative to Mg II λ2800 agree with extinction corrected observed I Zw 1 fluxes, except for C IV λ1549 (5) the sensitivity of Fe II emission strength to microturbulence ξ casts doubt on existing relative Fe/Mg abundances derived from Fe II (UV)/Mg II flux ratios. Our calculated Fe II emission spectra, suitable for BLRs in AGNs, are available at http://iacs.cua.edu/people/verner/FeII. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 05-26555.

  15. VizieR Online Data Catalog: SPOGS. I. SDSS Shocked POststarburst Galaxy cand. (Alatalo+, 2016)

    NASA Astrophysics Data System (ADS)

    Alatalo, K.; Cales, S. L.; Rich, J. A.; Appleton, P. N.; Kewley, L. J.; Lacy, M.; Lanz, L.; Medling, A. M.; Nyland, K.

    2016-07-01

    There are many mechanisms by which galaxies can transform from blue, star-forming spirals, to red, quiescent early-type galaxies, but our current census of them does not form a complete picture. Recent observations of nearby case studies have identified a population of galaxies that quench "quietly". Traditional poststarburst searches seem to catch galaxies only after they have quenched and transformed, and thus miss any objects with additional ionization mechanisms exciting the remaining gas. The Shocked POststarburst Galaxy Survey (SPOGS) aims to identify transforming galaxies, in which the nebular lines are excited via shocks instead of through star formation processes. Utilizing the Oh-Sarzi-Schawinski-Yi (OSSY, 2011ApJS..195...13O) measurements on the Sloan Digital Sky Survey Data Release 7 catalog, we applied Balmer absorption and shock boundary criteria to identify 1067 SPOG candidates (SPOGs*) within z=0.2. SPOGs* represent 0.2% of the OSSY sample galaxies that exceed the continuum signal-to-noise cut (and 0.7% of the emission line galaxy sample). SPOGs* colors suggest that they are in an earlier phase of transition than OSSY galaxies that meet an "E+A" selection. SPOGs* have a 13% 1.4GHz detection rate from the Faint Images of the Radio Sky at Twenty Centimeters Survey, higher than most other subsamples, and comparable only to low-ionization nuclear emission line region hosts, suggestive of the presence of active galactic nuclei (AGNs). SPOGs* also have stronger Na i D absorption than predicted from the stellar population, suggestive of cool gas being driven out in galactic winds. It appears that SPOGs* represent an earlier phase in galaxy transformation than traditionally selected poststarburst galaxies, and that a large proportion of SPOGs* also have properties consistent with disruption of their interstellar media, a key component to galaxy transformation. It is likely that many of the known pathways to transformation undergo a SPOG phase. Studying this

  16. H II regions in the dwarf galaxy UGC-A 86

    NASA Technical Reports Server (NTRS)

    Miller, Bryan W.; Hodge, Paul

    1993-01-01

    The uncertain nature of the dwarf irregular galaxy UGC-A 86 (VIIZw009) makes it a very interesting object for studying star formation at the low end of the galaxy luminosity function. Saha and Hoessel (1991) find that this object is composed of two main parts, one of which appears more resolved than the other. The more resolved component has an excess of blue stars, suggesting that it is currently undergoing star formation. Thus, they argue that UGC-A 86 could be either a superposition of unrelated galaxies, two interacting galaxies, or a single galaxy. However, surface photometry performed by Richter et al. (1991) indicates that it is a single galaxy with an exponential luminosity profile. Richter et al. also find UGC-A 86 to be extremely dusty and to be associated with the infrared source IRAS 3550+6657. The uncertainty is compounded by the large ambiguity in the distance, though a heliocentric H1 velocity of 80 plus or minus 7 km s(sup -1) suggests that it is either a member of the Local Group or perhaps the IC 342 group. A distance of 1.5 Mpc and a reddening of E(B - V) = 0.65 is adopted. UGC-A 86 in H-alpha was observed in order to measure its current star formation rate. This is part of a larger project to study the star formation rates and histories of a complete sample of dwarf galaxies in the Local Group and other nearby groups. The H region luminosity function and size distribution for UGC-A 86 are presented and compared with previous observations of similar dwarf galaxies.

  17. Unveiling the nature of bright z ≃ 7 galaxies with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Bowler, R. A. A.; Dunlop, J. S.; McLure, R. J.; McLeod, D. J.

    2017-04-01

    We present new Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) imaging of 25 extremely luminous (-23.2 ≤ MUV ≲ -21.2) Lyman-break galaxies (LBGs) at z ≃ 7. The sample was initially selected from 1.65 deg2 of ground-based imaging in the UltraVISTA/COSMOS and UDS/SXDS fields, and includes the extreme Lyman α emitters, 'Himiko' and 'CR7'. A deconfusion analysis of the deep Spitzer photometry available suggests that these galaxies exhibit strong rest-frame optical nebular emission lines (EW0(Hβ + [O III]) > 600 Å). We find that irregular, multiple-component morphologies suggestive of clumpy or merging systems are common (fmulti > 0.4) in bright z ≃ 7 galaxies, and ubiquitous at the very bright end (MUV < -22.5). The galaxies have half-light radii in the range r1/2 ˜ 0.5-3 kpc. The size measurements provide the first determination of the size-luminosity relation at z ≃ 7 that extends to MUV ˜ -23. We find the relation to be steep with r1/2 ∝ L1/2. Excluding clumpy, multicomponent galaxies however, we find a shallower relation that implies an increased star formation rate surface density in bright LBGs. Using the new, independent, HST/WFC3 data we confirm that the rest-frame UV luminosity function at z ≃ 7 favours a power-law decline at the bright end, compared to an exponential Schechter function drop-off. Finally, these results have important implications for the Euclid mission, which we predict will detect >1000 similarly bright galaxies at z ≃ 7. Our new HST imaging suggests that the vast majority of these galaxies will be spatially resolved by Euclid, mitigating concerns over dwarf star contamination.

  18. H I-SELECTED GALAXIES IN THE SLOAN DIGITAL SKY SURVEY. II. THE COLORS OF GAS-RICH GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.

    2009-09-15

    We utilize color information for an H I-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the H I selection creates a significant offset toward bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the H I selection restricts the sample to bluer, actively star-forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g - r< 0.3. We also demonstratemore » that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r - i colors but leave the g - r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.« less

  19. Extraplanar H II Regions in Spiral Galaxies. II. In Situ Star Formation in the Interstellar Thick Disk of NGC 4013

    NASA Astrophysics Data System (ADS)

    Howk, J. Christopher; Rueff, Katherine M.; Lehner, Nicolas; Wotta, Christopher B.; Croxall, Kevin; Savage, Blair D.

    2018-04-01

    We present observations of an Hα-emitting knot in the thick disk of NGC 4013, demonstrating it is an H II region surrounding a cluster of young hot stars z = 860 pc above the plane of this edge-on spiral galaxy. With LBT/MODS spectroscopy we show that this H II region has an Hα luminosity ∼4–7 times that of the Orion nebula, with an implied ionizing photon production rate log Q 0 ≈ 49.4 (photons s‑1). HST/WFPC2 imaging reveals an associated blue continuum source with M V = ‑8.21 ± 0.24. Together, these properties demonstrate that the H II region is powered by a young cluster of stars formed in situ in the thick disk, with an ionizing photon flux equivalent to ∼6 O7 V stars. If we assume ≈6 other extraplanar Hα-emitting knots are H II regions, the total thick disk star formation rate of NGC 4013 is ∼5 × 10‑4 M ⊙ yr‑1. The star formation likely occurs in the dense clouds of the interstellar thick disk seen in optical images of dust extinction and CO emission.

  20. Galaxies Probing Galaxies in PRIMUS. I. Sample, Spectroscopy, and Characteristics of the z\\sim 0.5 Mg II–absorbing Circumgalactic Medium

    NASA Astrophysics Data System (ADS)

    Rubin, Kate H. R.; Diamond-Stanic, Aleksandar M.; Coil, Alison L.; Crighton, Neil H. M.; Moustakas, John

    2018-01-01

    The spectroscopy of background QSO sightlines passing close to foreground galaxies is a potent technique for studying the circumgalactic medium (CGM). However, QSOs are effectively point sources, limiting their potential to constrain the size of circumgalactic gaseous structures. Here we present the first large Keck/Low-resolution Imaging Spectrometer (LRIS) and Very Large Telescope (VLT)/Focal Reducer/Low-dispersion Spectrograph 2 (FORS2) spectroscopic survey of bright ({B}{AB}< 22.3) background galaxies whose lines of sight probe Mg II λ λ 2796,2803 absorption from the CGM around close projected foreground galaxies at transverse distances 10 {kpc}< {R}\\perp < 150 {kpc}. Our sample of 72 projected pairs, drawn from the PRIsm MUlti-object Survey, includes 48 background galaxies that do not host bright active galactic nuclei, and both star-forming and quiescent foreground galaxies with stellar masses of 9.0< {log}{M}* /{M}ȯ < 11.2 at redshifts of 0.35< {z}{{f}/{{g}}}< 0.8. We detect Mg II absorption associated with these foreground galaxies with equivalent widths of 0.25 \\mathring{{A}} < {W}2796< 2.6 \\mathring{{A}} at > 2σ significance in 20 individual background sightlines passing within {R}\\perp < 50 {kpc} and place 2σ upper limits on W 2796 of ≲ 0.5 \\mathring{{A}} in an additional 11 close sightlines. Within {R}\\perp < 50 {kpc}, W 2796 is anticorrelated with R ⊥, consistent with analyses of Mg II absorption detected along background QSO sightlines. Subsamples of these foreground hosts divided at {log}{M}* /{M}ȯ =9.9 exhibit statistically inconsistent W 2796 distributions at 30 {kpc}< {R}\\perp < 50 {kpc}, with the higher-M * galaxies yielding a larger median W 2796 by 0.9 \\mathring{{A}} . Finally, we demonstrate that foreground galaxies with similar stellar masses exhibit the same median W 2796 at a given R ⊥ to within < 0.2 \\mathring{{A}} toward both background galaxies and toward QSO sightlines drawn from the literature. Analysis of these

  1. Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks

    NASA Astrophysics Data System (ADS)

    Mai, Chuhong; Desch, Steven J.; Boley, Aaron C.; Weiss, Benjamin P.

    2018-04-01

    Recent laboratory efforts have constrained the remanent magnetizations of chondrules and the magnetic field strengths to which the chondrules were exposed as they cooled below their Curie points. An outstanding question is whether the inferred paleofields represent the background magnetic field of the solar nebula or were unique to the chondrule-forming environment. We investigate the amplification of the magnetic field above background values for two proposed chondrule formation mechanisms, large-scale nebular shocks and planetary bow shocks. Behind large-scale shocks, the magnetic field parallel to the shock front is amplified by factors of ∼10–30, regardless of the magnetic diffusivity. Therefore, chondrules melted in these shocks probably recorded an amplified magnetic field. Behind planetary bow shocks, the field amplification is sensitive to the magnetic diffusivity. We compute the gas properties behind a bow shock around a 3000 km radius planetary embryo, with and without atmospheres, using hydrodynamics models. We calculate the ionization state of the hot, shocked gas, including thermionic emission from dust, thermal ionization of gas-phase potassium atoms, and the magnetic diffusivity due to Ohmic dissipation and ambipolar diffusion. We find that the diffusivity is sufficiently large that magnetic fields have already relaxed to background values in the shock downstream where chondrules acquire magnetizations, and that these locations are sufficiently far from the planetary embryos that chondrules should not have recorded a significant putative dynamo field generated on these bodies. We conclude that, if melted in planetary bow shocks, chondrules probably recorded the background nebular field.

  2. On the association between core-collapse supernovae and H ii regions

    NASA Astrophysics Data System (ADS)

    Crowther, Paul A.

    2013-01-01

    Previous studies of the location of core-collapse supernovae (ccSNe) in their host galaxies have variously claimed an association with H ii regions; no association or an association only with hydrogen-deficient ccSNe. Here, we examine the immediate environments of 39 ccSNe whose positions are well known in nearby (≤15 Mpc), low-inclination (≤65°) hosts using mostly archival, continuum-subtracted Hα ground-based imaging. We find that 11 out of 29 hydrogen-rich ccSNe are spatially associated with H ii regions (38 ± 11 per cent), versus 7 out of 10 hydrogen-poor ccSNe (70 ± 26 per cent). Similar results from Anderson et al. led to an interpretation that the progenitors of Type Ib/c ccSNe are more massive than those of Type II ccSNe. Here, we quantify the luminosities of H ii region either coincident with or nearby to the ccSNe. Characteristic nebulae are long-lived (˜20 Myr) giant H ii regions rather than short-lived (˜4 Myr) isolated, compact H ii regions. Therefore, the absence of an H ii region from most Type II ccSNe merely reflects the longer lifetime of stars with ⪉12 M⊙ than giant H ii regions. Conversely, the association of an H ii region with most Type Ib/c ccSNe is due to the shorter lifetime of stars with >12 M⊙ stars than the duty cycle of giant H ii regions. Therefore, we conclude that the observed association between certain ccSNe and H ii provides only weak constraints upon their progenitor masses. Nevertheless, we do favour lower mass progenitors for two Type Ib/c ccSNe that lack associated nebular emission, a host cluster or a nearby giant H ii region. Finally, we also reconsider the association between long gamma-ray bursts and the peak continuum light from their (mostly) dwarf hosts, and conclude that this is suggestive of very high mass progenitors, in common with previous studies.

  3. Stellar Populations and Physical Conditions at 100 pc Resolution in a Lensed Galaxy at z 4

    NASA Astrophysics Data System (ADS)

    Berg, Danielle

    2015-10-01

    Large surveys of star-forming galaxies at high redshift (z > 1.5) have provided us with a broad understanding of how galaxies assemble and evolve, but the spatial and spectral limitations inherent in observing faint, distant objects mean that many of the physical processes regulating this dynamic evolution are poorly constrained. Much of our most detailed knowledge of the physical conditions in distant galaxies comes from careful studies of gravitationally lensed sources, few of which are at z>3.5. FOR J0332-3557 is a gravitationally lensed galaxy at z 4 for which we and other groups have obtained a total of 37.3 hours of VLT spectroscopy. The rest-frame UV spectrum is notable for its unusual combination of both strong emission lines in the rest-frame UV and strong Lya and interstellar absorption, and for the unusual spatial variation seen in the nebular emission lines, which are less extended than the underlying stellar continuum. We propose high spatial resolution imaging of FOR J0332-3557 with four broadband filters on WFC3, taking advantage of both the HST resolution and the lensing magnification to study star formation and extinction on 100 pc scales. Because the interpretation of our unusual rest-frame UV and optical spectra requires an accurate reddening estimate, combining these observations with ground-based spectroscopy will give the most complete picture to date of chemical evolution in a distant galaxy.

  4. Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3*

    NASA Technical Reports Server (NTRS)

    Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, K.; Yang, Huan; Carilli, Chris; Combes, Francoise; Dassas, Karine; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; hide

    2017-01-01

    We observed the [C II] line in 15 lensed galaxies at redshifts 1 less than z less than 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3sigma or better. High magnifications enable even modestly luminous galaxies to be detected in [C II] with Herschel. The [C II] luminosity in this sample ranges from 8 × 10(exp 7) solar luminosity to 3.7 × 10(exp 9) solar luminosity (after correcting for magnification), confirming that [C II] is a strong tracer of the ISM at high redshifts. The ratio of the [C II] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C II]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C II]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C II]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C II]/FIR correlates most strongly with dust temperature. The [C II] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

  5. The Kinematics of Multiple-peaked Lyα Emission in Star-forming Galaxies at z ~ 2-3

    NASA Astrophysics Data System (ADS)

    Kulas, Kristin R.; Shapley, Alice E.; Kollmeier, Juna A.; Zheng, Zheng; Steidel, Charles C.; Hainline, Kevin N.

    2012-01-01

    We present new results on the Lyα emission-line kinematics of 18 z ~ 2-3 star-forming galaxies with multiple-peaked Lyα profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that ~30% of such objects with detectable Lyα emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Lyα photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Lyα from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of Hα (z ~ 2) and [O III]λ5007 (z ~ 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Lyα profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of langΔv absrang = -230 km s-1. A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Lyα profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the predictions of simple models for outflowing and infalling gas distributions around

  6. The Least Luminous Galaxies in the Universe

    NASA Astrophysics Data System (ADS)

    Willman, Beth

    2011-05-01

    In the past six years, more than two dozen dwarf galaxies have been discovered around the Milky Way and M31. Many of these discoveries are 100 times less luminous than any galaxy previously known, and a million times less luminous than the Milky Way itself. These discoveries have made astronomers question the very meaning of the word "galaxy", and hint that such ultra-faint dwarf galaxies may be the most numerous type of galaxy in the universe. This talk will highlight i. how we can see galaxies that are effectively invisible in images of the sky, ii. the brewing controversy over the definition of the term "galaxy", and iii. what ultra-faint galaxies can reveal about the distribution of dark matter in our Universe.

  7. THE OPTICAL STRUCTURE OF THE STARBURST GALAXY M82. II. NEBULAR PROPERTIES OF THE DISK AND INNER WIND

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Westmoquette, M. S.; Smith, L. J.; Konstantopoulos, I. S.

    2009-12-01

    compact clouds and wind sources provides an ideal environment for broad line emission, and explains the large observed broad/narrow-line flux ratios. We have examined in more detail the discrete outflow channel identified within the inner wind in Paper I. The channel appears as a coherent, expanding cylindrical structure of length >120 pc and width 35-50 pc. The walls maintain an approximately constant (but subsonic) expansion velocity of approx60 km s{sup -1}, and are defined by peaks and troughs in the densities of the different line components. We hypothesize that as the hot wind fluid flows down the channel cavity, it interacts with the cooler, denser walls of the channel and with entrained material within the flow to produce broad-line emission, while the walls themselves emit primarily the narrow lines. We use the channel to examine further the relationship between the narrow and broad component emitting gas within the inner wind. Within the starburst energy injection zone, we find that turbulent motions (as traced by the broad component) appear to play an increasing role with height. Finally, we have argued that a point-like knot identified in GMOS position 4, exhibiting blueshifted (by approx140 km s{sup -1}), broad (approx<350 km s{sup -1}) Halpha emission and enhanced [S II]/Halpha and [N II]/Halpha ratios, is most likely an ejected luminous blue variable-type object.« less

  8. Constraining the Active Galactic Nucleus Contribution in a Multiwavelength Study of Seyfert Galaxies

    NASA Technical Reports Server (NTRS)

    Melendez, M.; Kraemer, S.B.; Schmitt, H.R.; Crenshaw, D.M.; Deo, R.P.; Mushotzky, R.F.; Bruhweiler, F.C.

    2008-01-01

    We have studied the relationship between the high- and low-ionization [O IV] (lambda)25.89 microns, [Ne III] (lambda)15.56 microns, and [Ne II] (lambda)12.81 microns emission lines with the aim of constraining the active galactic nuclei (AGNs) and star formation contributions for a sample of 103 Seyfert galaxies.We use the [O IV] and [Ne II] emission as tracers for the AGN power and star formation to investigate the ionization state of the emission-line gas.We find that Seyfert 2 galaxies have, on average, lower [O IV]/[Ne II] ratios than Seyfert 1 galaxies. This result suggests two possible scenarios: (1) Seyfert 2 galaxies have intrinsically weaker AGNs, or (2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. We estimate the fraction of [Ne II] directly associated with the AGNs and find that Seyfert 2 galaxies have a larger contribution from star formation, by a factor of approx.1.5 on average, than what is found in Seyfert 1 galaxies. Using the stellar component of [Ne II] as a tracer of the current star formation, we found similar star formation rates in Seyfert 1 and Seyfert 2 galaxies.We examined the mid- and far-infrared continua and found that [Ne II] is well correlated with the continuum luminosity at 60 microns and that both [Ne III] and [O IV] are better correlated with the 25 micron luminosities than with the continuum at longer wavelengths, suggesting that the mid-infrared continuum luminosity is dominated by the AGN, while the far-infrared luminosity is dominated by star formation. Overall, these results test the unified model of AGNs and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.

  9. Star Formation in a Complete Spectroscopic Survey of Galaxies

    NASA Astrophysics Data System (ADS)

    Carter, B. J.; Fabricant, D. G.; Geller, M. J.; Kurtz, M. J.; McLean, B.

    2001-10-01

    The 15R-North galaxy redshift survey is a uniform spectroscopic survey (S/N~10) covering the range 3650-7400 Å for 3149 galaxies with median redshift 0.05. The sample is 90% complete to R=15.4. The median slit covering fraction is 24% of the galaxy, apparently sufficient to minimize the effects of aperture bias on the EW(Hα). Forty-nine percent of the galaxies in the survey have one or more emission lines detected at >=2 σ. In agreement with previous surveys, the fraction of absorption-line galaxies increases steeply with galaxy luminosity. We use Hβ, [O III], Hα, and [N II] to discriminate between star-forming galaxies and AGNs. At least 20% of the galaxies are star-forming, at least 17% have AGN-like emission, and 12% have unclassifiable emission. The unclassified 12% may include a ``hybrid'' population of galaxies with both star formation and AGN activity. The AGN fraction increases steeply with luminosity; the fraction of star-forming galaxies decreases. We use the EW(Hα+[N II]) to estimate the Scalo birthrate parameter, b, the ratio of the current star formation rate to the time averaged star formation rate. The median birthrate parameter is inversely correlated with luminosity in agreement with the conclusions based on smaller samples (Kennicutt, Tamblyn, & Congdon). Because our survey is large, we identify 33 vigorously star-forming galaxies with b>3. We confirm the conclusion of Jansen, Franx, & Fabricant that EW([O II]) must be used with caution as a measure of current star formation. Finally, we examine the way galaxies of different spectroscopic type trace the large-scale galaxy distribution. As expected the absorption-line fraction decreases and the star-forming emission-line fraction increases as the galaxy density decreases. The AGN fraction is insensitive to the surrounding galaxy density; the unclassified fraction declines slowly as the density increases. For the star-forming galaxies, the EW(Hα) increases very slowly as the galaxy number

  10. Variable Stars in the Field of the Hydra II Ultra-Faint Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Vivas, Anna Katherina; Olsen, Knut A.; Blum, Robert D.; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas; Besla, Gurtina; Gallart, Carme; Van Der Marel, Roeland P.; Majewski, Steven R.; Munoz, Ricardo; Kaleida, Catherine C.; Saha, Abhijit; Conn, Blair; Jin, Shoko

    2016-06-01

    We searched for variable stars in Hydra II, one of the recently discovered ultra-faint dwarf satellites of the Milky Way, using gri time-series obtained with the Dark Energy Camera (DECam) at Cerro Tololo Inter-American Observatory, Chile. We discovered one RR Lyrae star in the galaxy which was used to derive a distance of 154±8 kpc to this system and to re-calculate its absolute magnitude and half-light radius.A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.

  11. After the Fall: The Dust and Gas in E+A Post-starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Smercina, A.; Smith, J. D. T.; Dale, D. A.; French, K. D.; Croxall, K. V.; Zhukovska, S.; Togi, A.; Bell, E. F.; Crocker, A. F.; Draine, B. T.; Jarrett, T. H.; Tremonti, C.; Yang, Yujin; Zabludoff, A. I.

    2018-03-01

    The traditional picture of post-starburst galaxies as dust- and gas-poor merger remnants, rapidly transitioning to quiescence, has been recently challenged. Unexpected detections of a significant interstellar medium (ISM) in many post-starburst galaxies raise important questions. Are they truly quiescent, and if so, what mechanisms inhibit further star formation? What processes dominate their ISM energetics? We present an infrared spectroscopic and photometric survey of 33 E+A post-starbursts selected by the Sloan Digital Sky Survey, aimed at resolving these questions. We find compact, warm dust reservoirs with high PAH abundances and total gas and dust masses significantly higher than expected from stellar recycling alone. Both polycyclic aromatic hydrocarbon (PAH)/total infrared (TIR) and dust-to-burst stellar mass ratios are seen to decrease with post-burst age, indicative of the accumulating effects of dust destruction and an incipient transition to hot, early-type ISM properties. Their infrared spectral properties are unique, with dominant PAH emission, very weak nebular lines, unusually strong H2 rotational emission, and deep [C II] deficits. There is substantial scatter among star formation rate (SFR) indicators, and both PAH and TIR luminosities provide overestimates. Even as potential upper limits, all tracers show that the SFR has typically experienced a decline of more than two orders of magnitude since the starburst and that the SFR is considerably lower than expected given both their stellar masses and molecular gas densities. These results paint a coherent picture of systems in which star formation was, indeed, rapidly truncated, but in which the ISM was not completely expelled, and is instead supported against collapse by latent or continued injection of turbulent or mechanical heating. The resulting aging burst populations provide a “high-soft” radiation field that seemingly dominates the E+A galaxies’ unusual ISM energetics.

  12. Blue compact dwarf galaxies. II - Near-infrared studies and stellar populations

    NASA Technical Reports Server (NTRS)

    Thuan, T. X.

    1983-01-01

    An IR photometric survey was performed of 36 blue compact dwarf galaxies (BCDG) where intense bursts of star formation have been observed. The survey covered the J, H, and K lines, with all readings taken at the level of a few mJy. Although the near-IR fluxes observed in the galaxies are due to K and M giants, the bursts have calculated ages of less than 50 million yr. However, the BCDG galaxies surveyed are not young, with the least chemically evolved galaxy observed, I Zw 18, featuring 50 pct of its stars formed prior to its last burst, but with a missing mass that is not accounted for by H I interferometric observations. It is concluded that the old stars must be more spatially extended than the young stars, and a mixture of OB stars with the K and M giants is projected as capable of displaying the colors observed. The star formation processes in the BCDG galaxies is defined as dependent on the total mass of the galaxies, with low mass galaxies having a high ratio of star formation, compared to their previous rates.

  13. Dwarf Galaxies in the Coma Cluster. II. Photometry and Analysis

    NASA Astrophysics Data System (ADS)

    Secker, J.; Harris, W. E.; Plummer, J. D.

    1997-12-01

    We use the data set derived in our previous paper (Secker & Harris 1997) to study the dwarf galaxy population in the central =~ 700 arcmin(2) of the Coma cluster, the majority of which are early-type dwarf elliptical (dE) galaxies. Analysis of the statistically-decontaminated dE galaxy sequence in the color-magnitude diagram reveals that the mean dE color at R = 18.0 mag is (B-R) =~ 1.4 mag, but that a highly significant trend of color with magnitude exists (Delta (B-R)/Delta R = -0.056+/-0.002 mag) in the sense that fainter dEs are bluer and thus presumably more metal-poor. The mean color of the faintest dEs in our sample is (B-R) =~ 1.15 mag, consistent with a color measurement of the diffuse intracluster light in the Coma core. This intracluster light could then have originated from the tidal disruption of faint dEs in the cluster core. The total galaxy luminosity function (LF) is well modeled as the sum of a log-normal distribution for the giant galaxies, and a Schechter function for the dE galaxies with a faint-end slope alpha = -1.41+/-0.05. This value of alpha is consistent with those measured for the Virgo and Fornax clusters. The spatial distribution of the faint dE galaxies (19.0 < R <= 22.5 mag) is well fit by a standard King model with a central surface density of Sigma_0 = 1.17 dEs arcmin(-2) and a core radius R_c = 22.15 arcmin ( =~ 0.46h(-1) Mpc). This core is significantly larger than the R_c = 13.71 arcmin ( =~ 0.29h(-1) Mpc) found for the cluster giants and the brighter dEs (R <= 19.0 mag), again consistent with the idea that faint dEs in the dense core have been disrupted. Finally, we find that most dEs belong to the general Coma cluster potential rather than as satellites of individual giant galaxies: An analysis of the number counts around 10 cluster giants reveals that they each have on average 4+/- 1 dE companions within a projected radius of 13.9h(-1) kpc. (SECTION: Galaxies)

  14. The Luminosity Function of OB Associations in the Galaxy

    NASA Astrophysics Data System (ADS)

    McKee, Christopher F.; Williams, Jonathan P.

    1997-02-01

    OB associations ionize the interstellar medium, producing both localized H II regions and diffuse ionized gas. The supernovae resulting from these associations pressurize and stir the interstellar medium. Using Smith, Biermann, & Mezger's compilation of radio H II regions in the Galaxy, and Kennicutt, Edgar, & Hodge's optical study of H II regions in nearby galaxies, we show that the luminosity distribution of giant OB associations in the Galaxy can be fit by a truncated power law of the form \\Nscra(>S)=\\Nscrau[(Su/S)-1], where S is the ionizing photon luminosity, \\Nscra(>S) is the number of associations with a luminosity of at least S, and Su is the upper limit to the distribution. The coefficient \\Nscrau is the number of the most luminous associations, with a luminosity between 0.5Su and Su. For the Galaxy, \\Nscrau=6.1 the fact that the number of the most luminous associations is significantly larger than unity indicates that there is a physical limit to the maximum size of H II regions in the Galaxy. To extend the luminosity distribution to small H II regions, we assume that the birthrate of associations, \\Nscr\\dota(>\\Nscr*), is also a truncated power law, \\Nscr\\dota(>\\Nscr*)~[(\\Nscr*u/\\Nscr*)-1], where \\Nscr* is the number of stars in the association. For large associations, the ionizing luminosity is proportional to the number of stars, S~\\Nscr* for smaller associations, we use both an analytic and a Monte Carlo approach to find the resulting luminosity distribution \\Nscra(>S). H II regions are generally centrally concentrated, with only the dense central regions being bright enough to appear in radio catalogs. Anantharamaiah postulated that radio H II regions have extended envelopes in order to account for diffuse radio recombination line emission in the Galaxy. Some of these envelopes are visible as the ionized ``worms'' discussed by Heiles and coworkers. We estimate that on the average the envelopes of radio H II regions absorb about twice

  15. Characterizing the stellar population of a sample of star forming galaxies with high emission of both [OIV]25.9um and [NeII]12.8um

    NASA Astrophysics Data System (ADS)

    Martínez-Paredes, M.; Bruzual, G.; Meléndez, M.; González-Martín, O.

    2017-11-01

    The optical diagnostic diagram te{BPT81, VO87} allow us to discriminate between the different excitation mechanism, like that produce by young stars and that produce by the AGN during the accretion of matter onto the super massive black hole. This kind of tool are important because allow us to study the connection between starburst and AGN. However, despite the great success, the identification of the most heavily dust-obscured systems remains a challenge for optical diagrams. Mid-infrared diagnostic are more suitable to study dust-enshrouded systems, where the effect of dust obscuration can hamper the interpretation of traditional optical diagnostics, since in this spectral range we have access to low-ionization lines (as [Ne II]12.8μm) typical of star forming regions and high ionization lines typical of active galaxies ([OIV]25.9μm), while intermediate ionization-lines ([Ne III]15.3μm) provide a unique scenario where the AGN coexist with active star formation in the host galaxy. In a previous work te{Melendez14} we have carried out extensive and detailed photoionization modeling to successfully separate the different excitation mechanism in the mid-infrared diagnostic diagrams proposed by te{Weaver10}. We successfully modelled the AGN and starburst galaxies ratios lines of [NeIII]/[NeII] Vs [OIV]/[NeIII]. However, we failed in modelling the observed ratio lines in galaxies with a normal star formation activity ([NeIII]/[NeII]<1 and [OIV]/[NeIII]<1). These results suggest the presence of a more complex excitation mechanism in these galaxies. In this project we are using the update stellar population models from te{BC17} that include massive stars, and the update photoionization models from CLOUDY from te{Ferland17}, to characterize the properties of the stellar population that produce the high ionization conditions in these galaxies.

  16. ZOMG - II. Does the halo assembly history influence central galaxies and gas accretion?

    NASA Astrophysics Data System (ADS)

    Romano-Díaz, Emilio; Garaldi, Enrico; Borzyszkowski, Mikolaj; Porciani, Cristiano

    2017-08-01

    The growth rate and the internal dynamics of galaxy-sized dark-matter haloes depend on their location within the cosmic web. Haloes that sit at the nodes grow in mass till the present time and are dominated by radial orbits. Conversely, haloes embedded in prominent filaments do not change much in size and are dominated by tangential orbits. Using zoom hydrodynamical simulations including star formation and feedback, we study how gas accretes on to these different classes of objects, which, for simplicity, we dub 'accreting' and 'stalled' haloes. We find that all haloes get a fresh supply of newly accreted gas in their inner regions, although this slowly decreases with time, in particular for the stalled haloes. The inflow of new gas is always higher than (but comparable with) that of recycled material. Overall, the cold-gas fraction increases (decreases) with time for the accreting (stalled) haloes. In all cases, a stellar disc and a bulge form at the centre of the simulated haloes. The total stellar mass is in excellent agreement with expectations based on the abundance-matching technique. Many properties of the central galaxies do not seem to correlate with the large-scale environment in which the haloes reside. However, there are two notable exceptions that characterize stalled haloes with respect to their accreting counterparts: (I) The galaxy disc contains much older stellar populations. (II) Its vertical scaleheight is larger by a factor of 2 or more. This thickening is likely due to the heating of the long-lived discs by mergers and close flybys.

  17. Studying the highly bent spectra of FR II-type radio galaxies with the KDA EXT model

    NASA Astrophysics Data System (ADS)

    Kuligowska, Elżbieta

    2018-04-01

    Context. The Kaiser, Dennett-Thorpe & Alexander (KDA, 1997, MNRAS, 292, 723) EXT model, that is, the extension of the KDA model of Fanaroff & Riley (FR) II-type source evolution, is applied and confronted with the observational data for selected FR II-type radio sources with significantly aged radio spectra. Aim. A sample of FR II-type radio galaxies with radio spectra strongly bent at their highest frequencies is used for testing the usefulness of the KDA EXT model. Methods: The dynamical evolution of FR II-type sources predicted with the KDA EXT model is briefly presented and discussed. The results are then compared to the ones obtained with the classical KDA approach, assuming the source's continuous injection and self-similarity. Results: The results and corresponding diagrams obtained for the eight sample sources indicate that the KDA EXT model predicts the observed radio spectra significantly better than the best spectral fit provided by the original KDA model.

  18. Investigating early-type galaxy evolution with a multiwavelength approach. II. The UV structure of 11 galaxies with Swift-UVOT

    NASA Astrophysics Data System (ADS)

    Rampazzo, R.; Mazzei, P.; Marino, A.; Uslenghi, M.; Trinchieri, G.; Wolter, A.

    2017-06-01

    Context. GALEX detected a significant fraction of early-type galaxies, in particular S0s, showing far-UV bright structures, sometimes involving an entire galaxy out to its outskirts. These features suggest the presence of either recent ongoing and/or prolonged star formation episodes, shedding new light on the evolution of these systems. Aims: We aim at understanding the evolutionary path[s] of these early-type galaxies and the mechanisms at the origin of their UV-bright structures. We investigate with a multiwavelength approach the link between the inner and outer galaxy regions of a set of 11 early-type galaxies that were selected because of their nearly passive stage of evolution in the nuclear region. Methods: This paper, second of a series, focuses on the information coming from the comparison between UV features detected by Swift-UVOT, which trace recent star formation, and the galaxy optical structure, which maps older stellar populations. We performed a surface photometric study of these early-type galaxies, observed with the Swift-UVOT UV filters W2 2030 Å λ0, M2 2231 Å λ0, W1 2634 Å λ0 and the UBV bands. BVRI photometry from other sources in the literature was also used. Our integrated magnitude measurements were analyzed and compared with corresponding values in the literature. We characterize the overall galaxy structure that best fits the UV and optical luminosity profiles using a single Sérsic law. Results: The galaxies NGC 1366, NGC 1426, NGC 3818, NGC 3962, and NGC 7192 show featureless luminosity profiles. Excluding NGC 1366, which has a clear edge-on disk (n ≈ 1-2), and NGC 3818, the remaining three galaxies have Sérsic's indices n ≈ 3-4 in the optical and a lower index in the UV. Bright ring- or arm-like structures are revealed by UV images and luminosity profiles of NGC 1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974, and IC 2006. The ring- or arm-like structures differ from galaxy to galaxy. Sérsic indices of UV profiles for these

  19. On the efficiency of jet production in FR II radio galaxies and quasars

    NASA Astrophysics Data System (ADS)

    Rusinek, Katarzyna; Sikora, Marek; Kozieł-Wierzbowska, Dorota; Godfrey, Leith

    2017-04-01

    Jet powers in many radio galaxies with extended radio structures appear to exceed their associated accretion luminosities. In systems with very low accretion rates, this is likely due to the very low accretion luminosities resulting from radiatively inefficient accretion flows. In systems with high accretion rates, the accretion flows are expected to be radiatively efficient, and the production of such powerful jets may require an accretion scenario, which involves magnetically arrested discs (MADs). However, numerical simulations of the MAD scenario indicate that jet production efficiency is large only for geometrically thick accretion flows and scales roughly with (H/R)2, where H is the disc height and R is the distance from the black hole. Using samples of FR II radio galaxies and quasars accreting at moderate accretion rates, we show that their jets are much more powerful than predicted by the MAD scenario. We discuss possible origins of this discrepancy, suggesting that it can be related to approximations adopted in magnetohydrodynamic simulations to treat optically thick accretion flow within the MAD zone, or may indicate that accretion discs are geometrically thicker than the standard theory predicts.

  20. OMEGA - OSIRIS Mapping of Emission-line Galaxies in A901/2 - II. Environmental influence on integrated star formation properties and AGN activity

    NASA Astrophysics Data System (ADS)

    Rodríguez del Pino, Bruno; Aragón-Salamanca, Alfonso; Chies-Santos, Ana L.; Weinzirl, Tim; Bamford, Steven P.; Gray, Meghan E.; Böhm, Asmus; Wolf, Christian; Maltby, David T.

    2017-06-01

    We present a study of the star formation and AGN activity for galaxies in CP 15051 the Abell 901/2 multicluster system at z ˜ 0.167 as part of the OSIRIS Mapping of Emission-line Galaxies in A901/2 (OMEGA) survey. Using Tuneable Filter data obtained with the OSIRIS instrument at the Gran Telescopio Canarias, we produce spectra covering the Hα and [N II] spectral lines for more than 400 galaxies. Using optical emission-line diagnostics, we identify a significant number of galaxies hosting AGN, which tend to have high masses and a broad range of morphologies. Moreover, within the environmental densities probed by our study, we find no environmental dependence on the fraction of galaxies hosting AGN. The analysis of the integrated Hα emission shows that the specific star formation rates of a majority of the cluster galaxies are below the field values for a given stellar mass. We interpret this result as evidence for a slow decrease in the star formation activity of star-forming galaxies as they fall into higher density regions, contrary to some previous studies that suggested a rapid truncation of star formation. We find that most of the intermediate- and high-mass spiral galaxies go through a phase in which their star formation is suppressed but still retain significant star formation activity. During this phase, these galaxies tend to retain their spiral morphology while their colours become redder. The presence of this type of galaxies in high-density regions indicates that the physical mechanism responsible for suppressing star formation affects mainly the gas component of the galaxies, suggesting that ram-pressure stripping or starvation is potentially responsible.

  1. The MassiveBlack-II simulation: The evolution of haloes and galaxies to z ~ 0

    DOE PAGES

    Khandai, Nishikanta; Di Matteo, Tiziana; Croft, Rupert; ...

    2015-04-24

    We investigate the properties and clustering of halos, galaxies and blackholes to z = 0 in the high resolution hydrodynamical simulation MassiveBlack-II (MBII). MBII evolves a ΛCDM cosmology in a cubical comoving volume V box = (100Mpc/h)³. It is the highest resolution simulation of this size which includes a self-consistent model for star formation, black hole accretion and associated feedback. We provide a simulation browser web application which enables interactive search and tagging of the halos, subhalos and their properties and publicly release our galaxy catalogs to the scientific community. Our analysis of the halo mass function in MBII revealsmore » that baryons have strong effects with changes in the halo abundance of 20–35% below the knee of the mass function (M halo 10 13.2 M ⊙ h at z = 0) when compared to dark-matter-only simulations. We provide a fitting function for the halo MF out to redshift z = 11 and discuss its limitations.« less

  2. The Kinematics of the Permitted C II λ6578 Line in a Large Sample of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Richer, Michael G.; Suárez, Genaro; López, José Alberto; García Díaz, María Teresa

    2017-03-01

    We present spectroscopic observations of the C II λ6578 permitted line for 83 lines of sight in 76 planetary nebulae at high spectral resolution, most of them obtained with the Manchester Echelle Spectrograph on the 2.1 m telescope at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir. We study the kinematics of the C II λ6578 permitted line with respect to other permitted and collisionally excited lines. Statistically, we find that the kinematics of the C II λ6578 line are not those expected if this line arises from the recombination of C2+ ions or the fluorescence of C+ ions in ionization equilibrium in a chemically homogeneous nebular plasma, but instead its kinematics are those appropriate for a volume more internal than expected. The planetary nebulae in this sample have well-defined morphology and are restricted to a limited range in Hα line widths (no large values) compared to their counterparts in the Milky Way bulge; both these features could be interpreted as the result of young nebular shells, an inference that is also supported by nebular modeling. Concerning the long-standing discrepancy between chemical abundances inferred from permitted and collisionally excited emission lines in photoionized nebulae, our results imply that multiple plasma components occur commonly in planetary nebulae.

  3. Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3

    NASA Astrophysics Data System (ADS)

    Malhotra, Sangeeta; Rhoads, James E.; Finkelstein, K.; Yang, Huan; Carilli, Chris; Combes, Françoise; Dassas, Karine; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; Guillard, Pierre; Nesvadba, Nicole; Rigby, Jane; Shin, Min-Su; Spaans, Marco; Strauss, Michael A.; Papovich, Casey

    2017-01-01

    We observed the [C II] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C II] with Herschel. The [C II] luminosity in this sample ranges from 8 × 107 L⊙ to 3.7 × 109 L⊙ (after correcting for magnification), confirming that [C II] is a strong tracer of the ISM at high redshifts. The ratio of the [C II] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C II]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C II]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C II]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C II]/FIR correlates most strongly with dust temperature. The [C II] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  4. The evolutionary sequence of post-starburst galaxies

    NASA Astrophysics Data System (ADS)

    Wilkinson, C. L.; Pimbblet, K. A.; Stott, J. P.

    2017-12-01

    There are multiple ways in which to select post-starburst galaxies in the literature. In this work, we present a study into how two well-used selection techniques have consequences on observable post-starburst galaxy parameters, such as colour, morphology and environment, and how this affects interpretations of their role in the galaxy duty cycle. We identify a master sample of H δ strong (EWH δ > 3Å) post-starburst galaxies from the value-added catalogue in the seventh data release of the Sloan Digital Sky Survey (SDSS DR7) over a redshift range 0.01 < z < 0.1. From this sample we select two E+A subsets, both having a very little [O II] emission (EW_[O II] > -2.5 Å) but one having an additional cut on EWHα (>-3 Å). We examine the differences in observables and AGN fractions to see what effect the H α cut has on the properties of post-starburst galaxies and what these differing samples can tell us about the duty cycle of post-starburst galaxies. We find that H δ strong galaxies peak in the 'blue cloud', E+As in the 'green valley' and pure E+As in the 'red sequence'. We also find that pure E+As have a more early-type morphology and a higher fraction in denser environments compared with the H δ strong and E+A galaxies. These results suggest that there is an evolutionary sequence in the post-starburst phase from blue discy galaxies with residual star formation to passive red early-types.

  5. CO-SPATIAL LONG-SLIT UV/OPTICAL SPECTRA OF TEN GALACTIC PLANETARY NEBULAE WITH HST/STIS. II. NEBULAR MODELS, CENTRAL STAR PROPERTIES, AND He+CNO SYNTHESIS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Henry, R. B. C.; Miller, T. R.; Balick, B.

    The goal of the present study is twofold. First, we employ new HST/STIS spectra and photoionization modeling techniques to determine the progenitor masses of eight planetary nebulae (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC 5315, NGC 5882, NGC 7662, and PB 6). Second, for the first time we are able to compare each object’s observed nebular abundances of helium, carbon, and nitrogen with abundance predictions of these same elements by a stellar model that is consistent with each object’s progenitor mass. Important results include the following: (1) the mass range of our objects’ central stars matches well withmore » the mass distribution of other central stars of planetary nebulae and white dwarfs; (2) He/H is above solar in all of our objects, in most cases likely due to the predicted effects of first dredge-up; (3) most of our objects show negligible C enrichment, probably because their low masses preclude third dredge-up; (4) C/O versus O/H for our objects appears to be inversely correlated, which is perhaps consistent with the conclusion of theorists that the extent of atmospheric carbon enrichment from first dredge-up is sensitive to a parameter whose value increases as metallicity declines; (5) stellar model predictions of nebular C and N enrichment are consistent with observed abundances for progenitor star masses ≤1.5 M{sub ⊙}. Finally, we present the first published photoionization models of NGC 5315 and NGC 5882.« less

  6. The Arecibo Galaxy Environment Survey - VI. The Virgo cluster (II)

    NASA Astrophysics Data System (ADS)

    Taylor, R.; Davies, J. I.; Auld, R.; Minchin, R. F.; Smith, R.

    2013-01-01

    We present 21-cm observations of a 5 × 1 deg2 region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 13 cluster members are detected, together with 36 objects in the background. We compare and contrast the results from this area with a larger 10 × 2 deg2 region. We combine the two data sets to produce an H i mass function, which shows a higher detection rate at low masses (but finds fewer massive galaxies) than less sensitive wider area surveys, such as ALFALFA. We find that the H i-detected galaxies are distributed differently to the non-detections, both spatially and in velocity, providing further evidence that the cluster is still assembling. We use the Tully-Fisher relation to examine the possibility of morphological evolution. We find that highly deficient galaxies, as well as some early-type galaxies, have much lower velocity widths than the Tully-Fisher relation predicts, indicating gas loss via ram-pressure stripping. We also find that H i detections without optical counterparts do not fit the predictions of the baryonic Tully-Fisher relation, implying that they are not primordial objects.

  7. H0LiCOW – II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE 0435-1223

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sluse, D.; Sonnenfeld, A.; Rumbaugh, N.

    Galaxies located in the environment or on the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H 0 from the time-delay technique. We present the results of a systematic spectroscopic identi cation of the galaxies in the field of view of the lensed quasar HE0435-1223 using the W. M. Keck, Gemini and ESO-Very Large telescopes. Our new catalog triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 30more » from the lens. We complement our catalog with literature data to gather redshifts up to 150 from the lens, and search for galaxy groups or clusters projected towards HE0435-1223. We con rm that the lens is a member of a small group that includes at least 12 galaxies, and nd 8 other group candidates near the line of sight of the lens. The flexion shift, namely the shift of lensed images produced by high order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. This analysis demonstrates that i) at most three of the five brightest galaxies projected within 1200 of the lens need to be explicitly used in the lens models, and ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.« less

  8. H0LiCOW – II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE 0435-1223

    DOE PAGES

    Sluse, D.; Sonnenfeld, A.; Rumbaugh, N.; ...

    2017-06-15

    Galaxies located in the environment or on the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H 0 from the time-delay technique. We present the results of a systematic spectroscopic identi cation of the galaxies in the field of view of the lensed quasar HE0435-1223 using the W. M. Keck, Gemini and ESO-Very Large telescopes. Our new catalog triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 30more » from the lens. We complement our catalog with literature data to gather redshifts up to 150 from the lens, and search for galaxy groups or clusters projected towards HE0435-1223. We con rm that the lens is a member of a small group that includes at least 12 galaxies, and nd 8 other group candidates near the line of sight of the lens. The flexion shift, namely the shift of lensed images produced by high order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. This analysis demonstrates that i) at most three of the five brightest galaxies projected within 1200 of the lens need to be explicitly used in the lens models, and ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.« less

  9. THE VIRUS-P EXPLORATION OF NEARBY GALAXIES (VENGA): SURVEY DESIGN, DATA PROCESSING, AND SPECTRAL ANALYSIS METHODS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Blanc, Guillermo A.; Weinzirl, Tim; Song, Mimi

    2013-05-15

    We present the survey design, data reduction, and spectral fitting pipeline for the VIRUS-P Exploration of Nearby Galaxies (VENGA). VENGA is an integral field spectroscopic survey, which maps the disks of 30 nearby spiral galaxies. Targets span a wide range in Hubble type, star formation activity, morphology, and inclination. The VENGA data cubes have 5.''6 FWHM spatial resolution, {approx}5 A FWHM spectral resolution, sample the 3600 A-6800 A range, and cover large areas typically sampling galaxies out to {approx}0.7R{sub 25}. These data cubes can be used to produce two-dimensional maps of the star formation rate, dust extinction, electron density, stellarmore » population parameters, the kinematics and chemical abundances of both stars and ionized gas, and other physical quantities derived from the fitting of the stellar spectrum and the measurement of nebular emission lines. To exemplify our methods and the quality of the data, we present the VENGA data cube on the face-on Sc galaxy NGC 628 (a.k.a. M 74). The VENGA observations of NGC 628 are described, as well as the construction of the data cube, our spectral fitting method, and the fitting of the stellar and ionized gas velocity fields. We also propose a new method to measure the inclination of nearly face-on systems based on the matching of the stellar and gas rotation curves using asymmetric drift corrections. VENGA will measure relevant physical parameters across different environments within these galaxies, allowing a series of studies on star formation, structure assembly, stellar populations, chemical evolution, galactic feedback, nuclear activity, and the properties of the interstellar medium in massive disk galaxies.« less

  10. Deep Imaging of Extremely Metal-Poor Galaxies

    NASA Astrophysics Data System (ADS)

    Corbin, Michael

    2006-07-01

    Conflicting evidence exists regarding whether the most metal-poor and actively star-forming galaxies in the local universe such as I Zw 18 contain evolved stars. We propose to help settle this issue by obtaining deep ACS/HRC U, narrow-V, I, and H-alpha images of nine nearby {z < 0.01} extremely metal-poor {12 + O/H < 7.65} galaxies selected from the Sloan Digital Sky Survey. These objects are only marginally resolved from the ground and appear uniformly blue, strongly motivating HST imaging. The continuum images will establish: 1.} If underlying populations of evolved stars are present, by revealing the objects' colors on scales 10 pc, and 2.} The presence of any faint tidal features, dust lanes, and globular or super star clusters, all of which constrain the objects' evolutionary states. The H-alpha images, in combination with ground-based echelle spectroscopy, will reveal 1.} Whether the objects are producing "superwinds" that are depleting them of their metals; ground-based images of some of them indeed show large halos of ionized gas, and 2.} The correspondence of their nebular and stellar emission on scales of a few parsecs, which is important for understanding the "feedback" process by which supernovae and stellar winds regulate star formation. One of the sample objects, CGCG 269-049, lies only 2 Mpc away, allowing the detection of individual red giant stars in it if any are present. We have recently obtained Spitzer images and spectra of this galaxy to determine its dust content and star formation history, which will complement the proposed HST observations. [NOTE: THIS PROPOSAL WAS REDUCED TO FIVE ORBITS, AND ONLY ONE OF THE ORIGINAL TARGETS, CGCG 269-049, AFTER THE PHASE I REVIEW

  11. The Next Generation Fornax Survey (NGFS). II. The Central Dwarf Galaxy Population

    NASA Astrophysics Data System (ADS)

    Eigenthaler, Paul; Puzia, Thomas H.; Taylor, Matthew A.; Ordenes-Briceño, Yasna; Muñoz, Roberto P.; Ribbeck, Karen X.; Alamo-Martínez, Karla A.; Zhang, Hongxin; Ángel, Simón; Capaccioli, Massimo; Côté, Patrick; Ferrarese, Laura; Galaz, Gaspar; Grebel, Eva K.; Hempel, Maren; Hilker, Michael; Lançon, Ariane; Mieske, Steffen; Miller, Bryan; Paolillo, Maurizio; Powalka, Mathieu; Richtler, Tom; Roediger, Joel; Rong, Yu; Sánchez-Janssen, Ruben; Spengler, Chelsea

    2018-03-01

    We present a photometric study of the dwarf galaxy population in the core region (≲r vir/4) of the Fornax galaxy cluster based on deep u‧g‧i‧ photometry from the Next Generation Fornax Cluster Survey. All imaging data were obtained with the Dark Energy Camera mounted on the 4 m Blanco telescope at the Cerro Tololo Interamerican Observatory. We identify 258 dwarf galaxy candidates with luminosities ‑17 ≲ M g‧ ≲ ‑8 mag, corresponding to typical stellar masses of 9.5≳ {log}{{ \\mathcal M }}\\star /{M}ȯ ≳ 5.5, reaching ∼3 mag deeper in point-source luminosity and ∼4 mag deeper in surface brightness sensitivity compared to the classic Fornax Cluster Catalog. Morphological analysis shows that the dwarf galaxy surface-brightness profiles are well represented by single-component Sérsic models with average Sérsic indices of < n{> }u\\prime ,g\\prime ,i\\prime =(0.78{--}0.83)+/- 0.02 and average effective radii of < {r}e{> }u\\prime ,g\\prime ,i\\prime =(0.67{--}0.70)+/- 0.02 {kpc}. Color–magnitude relations indicate a flattening of the galaxy red sequence at faint galaxy luminosities, similar to the one recently discovered in the Virgo cluster. A comparison with population synthesis models and the galaxy mass–metallicity relation reveals that the average faint dwarf galaxy is likely older than ∼5 Gyr. We study galaxy scaling relations between stellar mass, effective radius, and stellar mass surface density over a stellar mass range covering six orders of magnitude. We find that over the sampled stellar mass range several distinct mechanisms of galaxy mass assembly can be identified: (1) dwarf galaxies assemble mass inside the half-mass radius up to {log}{{ \\mathcal M }}\\star ≈ 8.0, (2) isometric mass assembly occurs in the range 8.0 ≲ {log}{{ \\mathcal M }}\\star /{M}ȯ ≲ 10.5, and (3) massive galaxies assemble stellar mass predominantly in their halos at {log}{{ \\mathcal M }}\\star ≈ 10.5 and above.

  12. The unusual N IV] -emitter galaxy GDS J033218.92-275302.7: star formation or AGN-driven winds from a massive galaxy at z = 5.56

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; Grazian, A.; Hayes, M.; Pentericci, L.; Schaerer, D.; Dickinson, M.; Cristiani, S.; Giavalisco, M.; Verhamme, A.; Nonino, M.; Rosati, P.

    2010-04-01

    Aims: We investigate the nature of the source GDS J033218.92-275302.7 at redshift ~5.56. Methods: The spectral energy distribution of the source is well-sampled by 16 bands photometry from UV-optical (HST and VLT), near infrared, near infrared (VLT) to mid-infrared (Spitzer). The detection of a signal in the mid-infrared Spitzer/IRAC bands 5.8, 8.0 μm - where the nebular emission contribution is less effective - suggests that there is a Balmer break, the signature of an underlying stellar population formed at earlier epochs. The high-quality VLT/FORS2 spectrum shows a clear Lyα emission line, together with semi-forbidden N iv] 1483.3-1486.5 also in emission. These lines imply a young stellar population. In particular, the N iv] 1483.3-1486.5 feature (if the source is not hosting an AGN) is a signature of massive and hot stars with an associated nebular emission. Conversely, it may be a signature of an AGN. The observed SED and the Lyα emission line profile were modeled carefully to investigate the internal properties of the source. Results: From the SED-fitting with a single and a double stellar population and from the Lyα modeling, it turns out that the source seems to have an evolved component with a stellar mass of ~5 × 1010 M⊙ and age ~0.4 Gyr, and a young component with an age of ~0.01 Gyr and star formation rate in the range of 30-200 M⊙ yr-1. The limits on the effective radius derived from the ACS/z850 and VLT/Ks bands indicate that this galaxy is denser than the local ones with similar mass. A relatively high nebular gas column density is favored from the Lyα line modeling (NHI ⪆ 1021 cm-2). A vigorous outflow (~ 450 km s-1) has been measured from the optical spectrum, consistent with the Lyα modeling. From ACS observations it turns out that the region emitting Lyα photons is spatially compact and has a similar effective radius (~0.1 kpc physical) estimated at the ~1400 Å rest-frame wavelength, whose emission is dominated by the stellar

  13. Rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6

    NASA Astrophysics Data System (ADS)

    Decarli, R.; Walter, F.; Venemans, B. P.; Bañados, E.; Bertoldi, F.; Carilli, C.; Fan, X.; Farina, E. P.; Mazzucchelli, C.; Riechers, D.; Rix, H.-W.; Strauss, M. A.; Wang, R.; Yang, Y.

    2017-05-01

    The existence of massive (1011 solar masses) elliptical galaxies by redshift z ≈ 4 (refs 1, 2, 3; when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. The only known galaxies with very high star-formation rates at z > 6 are, with one exception, the host galaxies of quasars, but these galaxies also host accreting supermassive (more than 109 solar masses) black holes, which probably affect the properties of the galaxies. Here we report observations of an emission line of singly ionized carbon ([C II] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. The discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. On the basis of the [C II] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. These sources are similar to the host galaxies of the quasars in [C II] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. Similar systems have previously been found at lower redshift. We find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations. If they are representative of the bright end of the [C II] luminosity function, then they can account for the population of massive elliptical galaxies at z ≈ 4 in terms of the density of cosmic space.

  14. Rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6.

    PubMed

    Decarli, R; Walter, F; Venemans, B P; Bañados, E; Bertoldi, F; Carilli, C; Fan, X; Farina, E P; Mazzucchelli, C; Riechers, D; Rix, H-W; Strauss, M A; Wang, R; Yang, Y

    2017-05-24

    The existence of massive (10 11 solar masses) elliptical galaxies by redshift z ≈ 4 (refs 1, 2, 3; when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. The only known galaxies with very high star-formation rates at z > 6 are, with one exception, the host galaxies of quasars, but these galaxies also host accreting supermassive (more than 10 9 solar masses) black holes, which probably affect the properties of the galaxies. Here we report observations of an emission line of singly ionized carbon ([C ii] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. The discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. On the basis of the [C ii] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. These sources are similar to the host galaxies of the quasars in [C ii] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. Similar systems have previously been found at lower redshift. We find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations. If they are representative of the bright end of the [C ii] luminosity function, then they can account for the population of massive elliptical galaxies at z ≈ 4 in terms of the density of cosmic space.

  15. A Study of Nine High-Redshift Clusters of Galaxies. II. Photometry, Spectra, and Ages of Clusters 0023+0423 and 1604+4304

    NASA Astrophysics Data System (ADS)

    Postman, Marc; Lubin, Lori M.; Oke, J. B.

    1998-08-01

    studies. We find that an exponentially decaying star formation rate is required to produce the observed amount of star formation for the majority of the galaxies in our sample. A time constant of tau = 0.6 Gyr appears to be optimal. We also detect several interesting galaxies at z > 1. Two of these galaxies are extremely luminous, with strong Mg ii lambda2800 absorption and Fe ii resonance-line absorption. These lines are so strong that we conclude that they must be generated within the atmospheres of a large population of young, hot stars.

  16. On the population of remnant Fanaroff-Riley type II radio galaxies and implications for radio source dynamics

    NASA Astrophysics Data System (ADS)

    Godfrey, L. E. H.; Morganti, R.; Brienza, M.

    2017-10-01

    The purpose of this work is two-fold: (1) to quantify the occurrence of ultrasteep spectrum remnant Fanaroff-Riley type II (FRII) radio galaxies in a 74 MHz flux-limited sample, and (2) perform Monte Carlo simulations of the population of active and remnant FRII radio galaxies to confront models of remnant lobe evolution, and to provide guidance for further investigation of remnant radio galaxies. We find that fewer than 2 per cent of FRII radio galaxies with S74 MHz > 1.5 Jy are candidate ultrasteep spectrum remnants, where we define ultrasteep spectrum as α _74 MHz^1400 MHz > 1.2. Our Monte Carlo simulations demonstrate that models involving Sedov-like expansion in the remnant phase, resulting in rapid adiabatic energy losses, are consistent with this upper limit, and predict the existence of nearly twice as many remnants with normal (not ultrasteep) spectra in the observed frequency range as there are ultrasteep spectrum remnants. This model also predicts an ultrasteep remnant fraction approaching 10 per cent at redshifts z < 0.5. Importantly, this model implies the lobes remain overpressured with respect to the ambient medium well after their active lifetime, in contrast with existing observational evidence that many FRII radio galaxy lobes reach pressure equilibrium with the external medium whilst still in the active phase. The predicted age distribution of remnants is a steeply decreasing function of age. In other words, young remnants are expected to be much more common than old remnants in flux-limited samples. For this reason, incorporating higher frequency data ≳5 GHz will be of great benefit to future studies of the remnant population.

  17. Galaxy And Mass Assembly (GAMA): galaxy close pairs, mergers and the future fate of stellar mass

    NASA Astrophysics Data System (ADS)

    Robotham, A. S. G.; Driver, S. P.; Davies, L. J. M.; Hopkins, A. M.; Baldry, I. K.; Agius, N. K.; Bauer, A. E.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Cluver, M.; De Propris, R.; Drinkwater, M. J.; Holwerda, B. W.; Kelvin, L. S.; Lara-Lopez, M. A.; Liske, J.; López-Sánchez, Á. R.; Loveday, J.; Mahajan, S.; McNaught-Roberts, T.; Moffett, A.; Norberg, P.; Obreschkow, D.; Owers, M. S.; Penny, S. J.; Pimbblet, K.; Prescott, M.; Taylor, E. N.; van Kampen, E.; Wilkins, S. M.

    2014-11-01

    We use a highly complete subset of the Galaxy And Mass Assembly II (GAMA-II) redshift sample to fully describe the stellar mass dependence of close pairs and mergers between 108 and 1012 M⊙. Using the analytic form of this fit we investigate the total stellar mass accreting on to more massive galaxies across all mass ratios. Depending on how conservatively we select our robust merging systems, the fraction of mass merging on to more massive companions is 2.0-5.6 per cent. Using the GAMA-II data we see no significant evidence for a change in the close pair fraction between redshift z = 0.05 and 0.2. However, we find a systematically higher fraction of galaxies in similar mass close pairs compared to published results over a similar redshift baseline. Using a compendium of data and the function γM = A(1 + z)m to predict the major close pair fraction, we find fitting parameters of A = 0.021 ± 0.001 and m = 1.53 ± 0.08, which represents a higher low-redshift normalization and shallower power-law slope than recent literature values. We find that the relative importance of in situ star formation versus galaxy merging is inversely correlated, with star formation dominating the addition of stellar material below M^* and merger accretion events dominating beyond M^*. We find mergers have a measurable impact on the whole extent of the galaxy stellar mass function (GSMF), manifest as a deepening of the `dip' in the GSMF over the next ˜Gyr and an increase in M^* by as much as 0.01-0.05 dex.

  18. Extent of warm haloes around medium-redshift galaxies

    NASA Technical Reports Server (NTRS)

    Burbidge, E. M.; Barlow, T. A.; Cohen, R. D.; Junkkarinen, V. T.; Womble, D. S.

    1989-01-01

    The properties of low-to-medium ionization gaseous haloes around galaxies are briefly reviewed. New observations concerning such haloes are presented. For the galaxy-QSO pair in the field of the radio source 3C303, the higher-redshift QSO has been found to show Mg II absorption at the lower redshift of the faint nearby galaxy. Secondly, new data are presented on one of the galaxies in the environment of the well-known BL Lac object AO 0235 + 164.

  19. Integrated Properties of Nearby Seyfert Galaxies Measured by 2-D Spectroscopy

    NASA Astrophysics Data System (ADS)

    Xia, Junjie; Malkan, Matthew Arnold

    2017-01-01

    We present our measurements of mosaicing long-slit spectra of 12 nearby Seyfert galaxies. We obtained these data cubes at ~6‧‧ spatial resolution using the Kast double spectrograph on the 3-m Shane telescope of Lick Observatory. We have measured the integrated emission lines of [O III], Hβ, Hα, [N II], and [S II]. We compare the relative strength of these lines from the galaxy nucleus with the total emission from the entire galaxy. In classification line ratio diagrams (BPT), the individual galaxy moves from the Seyfert region to the composite/star-forming locus as the effective absorbing aperture grows. This trend means that Seyfert galaxies observed at higher redshifts will become increasingly misclassified. We use our sample to quantify this systematic trend. We also estimate the rates of star formation in the host galaxies based on the emission lines.

  20. Star-formation complexes in the `galaxy-sized' supergiant shell of the galaxy Holmberg I

    NASA Astrophysics Data System (ADS)

    Egorov, Oleg V.; Lozinskaya, Tatiana A.; Moiseev, Alexei V.; Smirnov-Pinchukov, Grigory V.

    2018-05-01

    We present the results of observations of the galaxy Holmberg I carried out at the Russian 6-m telescope in the narrow-band imaging, long-slit spectroscopy, and scanning Fabry-Perot interferometer modes. A detailed analysis of gas kinematics, ionization conditions, and metallicity of star-forming regions in the galaxy is presented. The aim of the paper is to analyse the propagation of star formation in the galaxy and to understand the role of the ongoing star formation in the evolution of the central `galaxy-sized' supergiant H I shell (SGS), where all regions of star formation are observed. We show that star formation in the galaxy occurs in large unified complexes rather than in individual giant H II regions. Evidence of the triggered star formation is observed both on scales of individual complexes and of the whole galaxy. We identified two supernova-remnant candidates and one late-type WN star and analysed their spectrum and surrounding-gas kinematics. We provide arguments indicating that the SGS in Holmberg I is destructing by the influence of star formation occurring on its rims.

  1. NGC628 with SITELLE: I. Imaging spectroscopy of 4285 H II region candidates

    NASA Astrophysics Data System (ADS)

    Rousseau-Nepton, L.; Robert, C.; Martin, R. P.; Drissen, L.; Martin, T.

    2018-07-01

    This is the first paper of a series dedicated to nebular physics and the chemical evolution of nearby galaxies by investigating large samples of H II regions with the Canada-France-Hawaii Telescope imaging spectrograph SITELLE (Spectro-Imageur à Transformée de Fourier pour l'Étude en Long et en Large des raies d'Émission). We present a technique adapted to imaging spectroscopy to identify and extract parameters from 4285 H II region candidates found in the disc of NGC 628. Using both the spatial and spectral capabilities of SITELLE, our technique enables the extraction of the position, dust extinction, velocity, H α profile, diffuse ionized gas (DIG) background, luminosity, size, morphological type, and the emission-line fluxes for individual spaxels and the integrated spectrum for each region. We have produced a well-sampled H II region luminosity function and studied its variation with galactocentric radius and level of the DIG background. We found a slope α of -1.12 ± 0.03 with no evidence of a break at high luminosity. Based on the width of the region profile, bright regions are rather compact, while faint regions are seen over a wide range of sizes. The radius function reveals a slope of -1.81 ± 0.02. BPT diagrams of the individual spaxels and integrated line ratios confirm that most detections are H II regions. Also, maps of the line ratios show complex variations of the ionization conditions within H II regions. All this information is compiled in a new catalogue for H II regions. The objective of this data base is to provide a complete sample which will be used to study the whole parameter space covered by the physical conditions in active star-forming regions.

  2. The MICE Grand Challenge lightcone simulation - II. Halo and galaxy catalogues

    NASA Astrophysics Data System (ADS)

    Crocce, M.; Castander, F. J.; Gaztañaga, E.; Fosalba, P.; Carretero, J.

    2015-10-01

    This is the second in a series of three papers in which we present an end-to-end simulation from the MICE collaboration, the MICE Grand Challenge (MICE-GC) run. The N-body contains about 70 billion dark-matter particles in a (3 h-1 Gpc)3 comoving volume spanning five orders of magnitude in dynamical range. Here, we introduce the halo and galaxy catalogues built upon it, both in a wide (5000 deg2) and deep (z < 1.4) lightcone and in several comoving snapshots. Haloes were resolved down to few 1011 h-1 M⊙. This allowed us to model galaxies down to absolute magnitude Mr < -18.9. We used a new hybrid halo occupation distribution and abundance matching technique for galaxy assignment. The catalogue includes the spectral energy distributions of all galaxies. We describe a variety of halo and galaxy clustering applications. We discuss how mass resolution effects can bias the large-scale two-pt clustering amplitude of poorly resolved haloes at the ≲5 per cent level, and their three-pt correlation function. We find a characteristic scale-dependent bias of ≲6 per cent across the BAO feature for haloes well above M⋆ ˜ 1012 h-1 M⊙ and for luminous red galaxy like galaxies. For haloes well below M⋆ the scale dependence at 100 h-1 Mpc is ≲2 per cent. Lastly, we discuss the validity of the large-scale Kaiser limit across redshift and departures from it towards non-linear scales. We make the current version of the lightcone halo and galaxy catalogue (MICECATv1.0) publicly available through a dedicated web portal to help develop and exploit the new generation of astronomical surveys.

  3. Star Formation Histories of Dwarf Irregular Galaxies

    NASA Astrophysics Data System (ADS)

    Skillman, Evan

    1995-07-01

    We propose to obtain deep WFPC2 `BVI' color-magnitude diagrams {CMDs} for the dwarf irregular {dI} Local Group galaxies GR 8, Leo A, Pegasus, and Sextans A. In addition to resolved stars, we will use star clusters, and especially any globulars, to probe the history of intense star formation. These data will allow us to map the Pop I and Pop II stellar components, and thereby construct the first detailed star formation histories for non-interacting dI galaxies. Our results will bear on a variety of astrophysical problems, including the evolution of small galaxies, distances in the Local Group, age-metallicity distributions in small galaxies, ages of dIs, and the physics of star formation. The four target galaxies are typical dI systems in terms of luminosity, gas content, and H II region abundance, and represent a range in current star forming activity. They are sufficiently near to allow us to reach to stars at M_V = 0, have 0.1 of the luminosity of the SMC and 0.25 of its oxygen abundance. Unlike the SMC, these dIs are not near giant galaxies. This project will allow the extension of our knowledge of stellar populations in star forming galaxies from the spirals in the Local Group down to its smallest members. We plan to take maximum advantage of the unique data which this project will provide. Our investigator team brings extensive and varied experience in studies of dwarf galaxies, stellar populations, imaging photometry, and stellar evolution to this project.

  4. Spectroscopic Constraints on UV Metal Line Emission at z ≃ 6 - 9 The Nature of Lyα Emitting Galaxies in the Reionization-Era

    NASA Astrophysics Data System (ADS)

    Mainali, Ramesh; Zitrin, Adi; Stark, Daniel P.; Ellis, Richard S.; Richard, Johan; Tang, Mengtao; Laporte, Nicolas; Oesch, Pascal; McGreer, Ian

    2018-06-01

    Recent studies have revealed intense UV metal emission lines in a modest sample of z > 7 Lyman-α emitters, indicating a hard ionizing spectrum is present. If such high ionization features are shown to be common, it may indicate that extreme radiation fields play a role in regulating the visibility of Lyα in the reionization era. Here we present deep near-infrared spectra of seven galaxies with Lyα emission at 5.4 < z < 8.7 (including a newly-confirmed lensed galaxy at zLyα = 6.031) and three bright z ≃ 7 photometric targets. In nine sources we do not detect UV metal lines. However in the zLyα = 8.683 galaxy EGSY8p7, we detect a 4.6σ emission line in the narrow spectral window expected for NVλ1243. The feature is unresolved (FWHM<90 km s-1) and is likely nebular in origin. A deep H-band spectrum of EGSY8p7 reveals non-detections of CIV, He II, and OIII]. The presence of NV requires a substantial flux of photons above 77 eV, pointing to a hard ionizing spectrum powered by an AGN or fast radiative shocks. Regardless of its origin, the intense radiation field of EGSY8p7 may aid the transmission of Lyα through what is likely a partially neutral IGM. With this new detection, five of thirteen known Lyα emitters at z > 7 have now been shown to have intense UV line emission, suggesting that extreme radiation fields are commonplace among the Lyα population. Future observations with JWST will eventually clarify the origin of these features and explain their role in the visibility of Lyα in the reionization era.

  5. UV, optical and infrared properties of star forming galaxies

    NASA Technical Reports Server (NTRS)

    Huchra, John P.

    1987-01-01

    The UVOIR properties of galaxies with extreme star formation rates are examined. These objects seem to fall into three distinct classes which can be called (1) extragalactic H II regions, (2) clumpy irregulars, and (3) starburst galaxies. Extragalactic H II regions are dominated by recently formed stars and may be considered 'young' galaxies if the definition of young is having the majority of total integrated star formation occurring in the last billion years. Clumpy irregulars are bursts of star formation superposed on an old population and are probably good examples of stochastic star formation. It is possible that star formation in these galaxies is triggered by the infall of gas clouds or dwarf companions. Starburst galaxies are much more luminous, dustier and more metal rich than the other classes. These objects show evidence for shock induced star formation where shocks may be caused by interaction with massive companions or are the result of an extremely strong density wave.

  6. Properties of Narrow line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Rakshit, Suvendu; Stalin, Chelliah Subramonian; Chand, Hum; Zhang, Xue-Guang

    2018-04-01

    Narrow line Seyfert 1 (NLSy1) galaxies constitute a class of active galactic nuclei characterized by the full width at half maximum (FWHM) of the Hα broad emission line <2000 km s-1 and the flux ratio of [O III] to Hα <3. Their properties are not well understood since only a few NLSy1 galaxies were known earlier. We have studied various properties of NLSy1 galaxies using an enlarged sample and compared them with the conventional broad-line Seyfert 1 (BLSy1) galaxies. Both the sample of sources have z˜ 0.8 and their optical spectra from SDSS-DR12 that are used to derive various physical parameters have a median signal to noise (S/N) ratio >10 pixel-1. A strong correlation between the Hα and Hα emission lines is found both in the FWHM and flux. The nuclear continuum luminosity is found to be strongly correlated with the luminosity of Hα, Hα and [O III] emission lines. The black hole mass in NLSy1 galaxies is lower compared to their broad line counterparts. Compared to BLSy1 galaxies, NLSy1 galaxies have a stronger FeII emission and a higher Eddington ratio that place them in the extreme upper right corner of the R4570 - λEdd diagram. The distribution of the radio-loudness parameter (R) in NLSy1 galaxies drops rapidly at R>10 compared to the BLSy1 galaxies that have powerful radio jets. The soft X-ray photon index in NLSy1 galaxies is on average higher (2.9 ± 0.9) than BLSy1 galaxies (2.4 ± 0.8). It is anti-correlated with the Hα width but correlated with the FeII strength. NLSy1 galaxies on average have a lower amplitude of optical variability compared to their broad lines counterparts. These results suggest Eddington ratio as the main parameter that drives optical variability in these sources.

  7. THE JAMES CLERK MAXWELL TELESCOPE NEARBY GALAXIES LEGACY SURVEY. II. WARM MOLECULAR GAS AND STAR FORMATION IN THREE FIELD SPIRAL GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Warren, B. E.; Wilson, C. D.; Sinukoff, E.

    2010-05-01

    We present the results of large-area {sup 12}CO J = 3-2 emission mapping of three nearby field galaxies, NGC 628, NGC 3521, and NGC 3627, completed at the James Clerk Maxwell Telescope as part of the Nearby Galaxies Legacy Survey. These galaxies all have moderate to strong {sup 12}CO J = 3-2 detections over large areas of the fields observed by the survey, showing resolved structure and dynamics in their warm/dense molecular gas disks. All three galaxies were part of the Spitzer Infrared Nearby Galaxies Survey sample, and as such have excellent published multiwavelength ancillary data. These data sets allowmore » us to examine the star formation properties, gas content, and dynamics of these galaxies on sub-kiloparsec scales. We find that the global gas depletion time for dense/warm molecular gas in these galaxies is consistent with other results for nearby spiral galaxies, indicating this may be independent of galaxy properties such as structures, gas compositions, and environments. Similar to the results from The H I Nearby Galaxy Survey, we do not see a correlation of the star formation efficiency with the gas surface density consistent with the Schmidt-Kennicutt law. Finally, we find that the star formation efficiency of the dense molecular gas traced by {sup 12}CO J = 3-2 is potentially flat or slightly declining as a function of molecular gas density, the {sup 12}CO J = 3-2/J = 1-0 ratio (in contrast to the correlation found in a previous study into the starburst galaxy M83), and the fraction of total gas in molecular form.« less

  8. NGC 3934: a shell galaxy in a compact galaxy environment

    NASA Astrophysics Data System (ADS)

    Bettoni, D.; Galletta, G.; Rampazzo, R.; Marino, A.; Mazzei, P.; Buson, L. M.

    2011-10-01

    Context. Mergers/accretions are considered the main drivers of the evolution of galaxies in groups. We investigate the NGC 3933 poor galaxy association that contains NGC 3934, which is classified as a polar-ring galaxy. Aims: The multi-band photometric analysis of NGC 3934 allows us to investigate the nature of this galaxy and to re-define the NGC 3933 group members with the aim to characterize the group's dynamical properties and its evolutionary phase. Methods: We imaged the group in the far (FUV, λeff = 1539 Å) and near (NUV, λeff = 2316 Å) ultraviolet (UV) bands of the Galaxy Evolution Explorer (GALEX). From the deep optical imaging we determined the fine structure of NGC 3934. We measured the recession velocity of PGC 213894 which shows that it belongs to the NGC 3933 group. We derived the spectral energy distribution (SED) from FUV to far-IR emission of the two brightest members of the group. We compared a grid of smooth particle hydrodynamical (SPH) chemo-photometric simulations with the SED and the integrated properties of NGC 3934 and NGC 3933 to devise their possible formation/evolutionary scenarios. Results: The NGC 3933 group has six bright members: a core composed of five galaxies, which have Hickson's compact group characteristics, and a more distant member, PGC 37112. The group velocity dispersion is relatively low (157 ± 44 km s-1). The projected mass, from the NUV photometry, is ~7 × 1012 M⊙ with a crossing time of 0.04 Hubble times, suggesting that at least in the center the group is virialized. We do not find evidence that NGC 3934 is a polar-ring galaxy, as suggested by the literature, but find that it is a disk galaxy with a prominent dust-lane structure and a wide type-II shell structure. Conclusions: NGC 3934 is a quite rare example of a shell galaxy in a likely dense galaxy region. The comparison between physically motivated SPH simulations with multi-band integrated photometry suggests that NGC 3934 is the product of a major merger.

  9. The role of stellar radial motions in shaping galaxy surface brightness profiles

    NASA Astrophysics Data System (ADS)

    Ruiz-Lara, T.; Few, C. G.; Florido, E.; Gibson, B. K.; Pérez, I.; Sánchez-Blázquez, P.

    2017-12-01

    Aims: The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods: We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results: Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as

  10. Revisiting The First Galaxies: The epoch of Population III stars

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Muratov, Alexander L.; Gnedin, Oleg Y.; Gnedin, Nickolay Y.

    2013-07-19

    We investigate the transition from primordial Population III (Pop III) star formation to normal Pop II star formation in the first galaxies using new cosmological hydrodynamic simulations. We find that while the first stars seed their host galaxies with metals, they cannot sustain significant outflows to enrich the intergalactic medium, even assuming a top-heavy initial mass function. This means that Pop III star formation could potentially continue until z 6 in different unenriched regions of the universe, before being ultimately shut off by cosmic reionization. Within an individual galaxy, the metal production and stellar feedback from Pop II stars overtake Pop III stars inmore » 20-200 Myr, depending on galaxy mass.« less

  11. ISM Parameters in the Normal Galaxy NGC 5713

    NASA Technical Reports Server (NTRS)

    Lord, S. D.; Malhotra, S.; Lim, T.; Helou, G.; Beichman, C. A.; Dinerstein, H.; Hollenbach, D. J.; Hunter, D. A.; Lo, K. Y.; Lu, N. Y.; hide

    1996-01-01

    We report ISO Long Wavelength Spectrometer (LWS) observations fo the Sbc(s) pec galaxy NGC 5713. We have obtained strong detections of the fine-structure forbidden transitions [C(sub ii)] 158(micro)m, [O(sub i)]63(micro)m, and [O(sub iii)] 88(micro)m, and significant upper limits for[N(sub ii)]122(micro)m, [O(sub iii)] 52(micro)m, and [N(sub iii)] 57(micro)m. We also detect the galaxy's dust continuum emission between 43 and 197 microns.

  12. The Physical Conditions, Metallicity and Metal Abundance Ratios in a Highly Magnified Galaxy at z = 3.6252

    NASA Astrophysics Data System (ADS)

    Bayliss, Matthew B.; Rigby, Jane R.; Sharon, Keren; Wuyts, Eva; Florian, Michael; Gladders, Michael D.; Johnson, Traci; Oguri, Masamune

    2014-08-01

    We present optical and near-IR imaging and spectroscopy of SGAS J105039.6+001730, a strongly lensed galaxy at z = 3.6252 magnified by >30×, and derive its physical properties. We measure a stellar mass of log(M */M ⊙) = 9.5 ± 0.35, star formation rates from [O II] λλ3727 and Hβ of 55 ± 25 and 84 ± 24 M ⊙ yr-1, respectively, an electron density of ne <= 103 cm-2, an electron temperature of Te <= 14,000 K, and a metallicity of 12 + log(O/H) = 8.3 ± 0.1. The strong C III] λλ1907,1909 emission and abundance ratios of C, N, O, and Si are consistent with well-studied starbursts at z ~ 0 with similar metallicities. Strong P Cygni lines and He II λ1640 emission indicate a significant population of Wolf-Rayet stars, but synthetic spectra of individual populations of young, hot stars do not reproduce the observed integrated P Cygni absorption features. The rest-frame UV spectral features are indicative of a young starburst with high ionization, implying either (1) an ionization parameter significantly higher than suggested by rest-frame optical nebular lines, or (2) differences in one or both of the initial mass function and the properties of ionizing spectra of massive stars. We argue that the observed features are likely the result of a superposition of star forming regions with different physical properties. These results demonstrate the complexity of star formation on scales smaller than individual galaxies, and highlight the importance of systematic effects that result from smearing together the signatures of individual star forming regions within galaxies. Based on observations from the Magellan Telescopes at Las Campanas Observatory, from Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the United States, Canada, Chile, Australia, Brazil and Argentina, with additional supporting data obtained at the Subaru telescope

  13. Blueberry Galaxies: The Lowest Mass Young Starbursts

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Wang, Junxian

    2017-09-01

    Searching for extreme emission line galaxies allows us to find low-mass metal-poor galaxies that are good analogs of high redshift Lyα emitting galaxies. These low-mass extreme emission line galaxies are also potential Lyman-continuum leakers. Finding them at very low redshifts (z≲ 0.05) allows us to be sensitive to even lower stellar masses and metallicities. We report on a sample of extreme emission line galaxies at z≲ 0.05 (blueberry galaxies). We selected them from SDSS broadband images on the basis of their broadband colors and studied their properties with MMT spectroscopy. From the entire SDSS DR12 photometric catalog, we found 51 photometric candidates. We spectroscopically confirm 40 as blueberry galaxies. (An additional seven candidates are contaminants, and four remain without spectra.) These blueberries are dwarf starburst galaxies with very small sizes (<1 kpc) and very high ionization ([O III]/[O II] ˜ 10-60). They also have some of the lowest stellar masses ({log}(M/{M}⊙ )˜ 6.5{--}7.5) and lowest metallicities (7.1< 12+{log}({{O}}/{{H}})< 7.8) of starburst galaxies. Thus, they are small counterparts to green pea galaxies and high redshift Lyα emitting galaxies.

  14. Probing the Galactic Structure of the Milky Way with H II Regions

    NASA Astrophysics Data System (ADS)

    Red, Wesley Alexander; Wenger, Trey V.; Balser, Dana; Anderson, Loren; Bania, Thomas

    2018-01-01

    Mapping the structure of the Milky Way is challenging since we reside within the Galactic disk and distances are difficult to determine. Elemental abundances provide important constraints on theories of the formation and evolution of the Milky Way. HII regions are the brightest objects in the Galaxy at radio wavelengths and are detected across the entire Galactic disk. We use the Jansky Very Large Array (VLA) to observe the radio recombination line (RRL) and continuum emission of 120 Galactic HII regions located across the Galactic disk. In thermal equilibrium, metal abundances are expected to set the nebular electron temperature with high abundances producing low temperatures. We derive the metallicity of HII regions using an empirical relation between an HII region's radio recombination line-to-continuum ratio and nebular metallicity. Here we focus on a subset of 20 HII regions from our sample that have been well studied with the Green Bank Telescope (GBT) to test our data reduction pipeline and analysis methods. Our goal is to expand this study to the Southern skies with the Australia Telescope Compact Array and create a metallicity map of the entire Galactic disk.

  15. Nebular phase observations of the Type-Ib supernova iPTF13bvn favour a binary progenitor

    NASA Astrophysics Data System (ADS)

    Kuncarayakti, H.; Maeda, K.; Bersten, M. C.; Folatelli, G.; Morrell, N.; Hsiao, E. Y.; González-Gaitán, S.; Anderson, J. P.; Hamuy, M.; de Jaeger, T.; Gutiérrez, C. P.; Kawabata, K. S.

    2015-07-01

    Aims: We present and analyse late-time observations of the Type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, which were done ~300 days after the explosion. We discuss them in the context of constraints on the supernova's progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lower-mass star in a close binary system. Methods: Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg I]λλ4571, [O I]λλ6300, 6364, and [Ca II]λλ7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compared the [O I]/[Ca II] line ratio with other supernovae. Results.The core oxygen mass of the supernova progenitor was estimated to be ≲0.7 M⊙, which implies initial progenitor mass that does not exceed ~15-17 M⊙.Since the derived mass is too low for a single star to become a Wolf-Rayet star, this result lends more support to the binary nature of the progenitor star of iPTF13bvn. The comparison of [O I]/[Ca II] line ratio with other supernovae also shows that iPTF13bvn appears to be in close association with the lower mass progenitors of stripped-envelope and Type-II supernovae. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU); Chilean Telescope Time Allocation Committee proposal CN2014A-91.

  16. A Multi-epoch Kinematic Study of the Remote Dwarf Spheroidal Galaxy Leo II

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Spencer, Meghin E.; Mateo, Mario; Walker, Matthew G.

    2017-02-20

    We conducted a large spectroscopic survey of 336 red giants in the direction of the Leo II dwarf galaxy using Hectochelle on the Multiple Mirror Telescope, and we conclude that 175 of them are members based on their radial velocities and surface gravities. Of this set, 40 stars have never before been observed spectroscopically. The systemic velocity of the dwarf is 78.3 ± 0.6 km s{sup −1} with a velocity dispersion of 7.4 ± 0.4 km s{sup −1}. We identify one star beyond the tidal radius of Leo II but find no signatures of uniform rotation, kinematic asymmetries, or streams.more » The stars show a strong metallicity gradient of −1.53 ± 0.10 dex kpc{sup −1} and have a mean metallicity of −1.70 ± 0.02 dex. There is also evidence of two different chemodynamic populations, but the signal is weak. A larger sample of stars would be necessary to verify this feature.« less

  17. PROBING THE PHYSICS OF NARROW LINE REGIONS IN ACTIVE GALAXIES. II. THE SIDING SPRING SOUTHERN SEYFERT SPECTROSCOPIC SNAPSHOT SURVEY (S7)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dopita, Michael A.; Davies, Rebecca; Kewley, Lisa

    2015-03-15

    Here we describe the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) and present results on 64 galaxies drawn from the first data release. The S7 uses the Wide Field Spectrograph mounted on the ANU 2.3 m telescope located at the Siding Spring Observatory to deliver an integral field of 38 × 25 arcsec at a spectral resolution of R = 7000 in the red (530–710 nm), and R = 3000 in the blue (340–560 nm). From these data cubes we have extracted the narrow-line region spectra from a 4 arcsec aperture centered on the nucleus. We also determine themore » Hβ and [O iii] λ5007 fluxes in the narrow lines, the nuclear reddening, the reddening-corrected relative intensities of the observed emission lines, and the Hβ and [O iii] λ5007 luminosities determined from spectra for which the stellar continuum has been removed. We present a set of images of the galaxies in [O iii] λ5007, [N ii] λ6584, and Hα, which serve to delineate the spatial extent of the extended narrow-line region and also to reveal the structure and morphology of the surrounding H ii regions. Finally, we provide a preliminary discussion of those Seyfert 1 and Seyfert 2 galaxies that display coronal emission lines in order to explore the origin of these lines.« less

  18. Starburst Galaxies. II. Imaging and Spectroscopy of a Radio-selected Sample

    NASA Astrophysics Data System (ADS)

    Smith, Denise A.; Herter, Terry; Haynes, Martha P.; Beichman, C. A.; Gautier, T. N., III

    1996-06-01

    We present J-, H-, and K-band images and low-resolution K-band spectra of the 20 most luminous starburst galaxies from the survey of Condon, Frayer, & Broderick. Optical rotation curves are also shown for 10 of these galaxies. Near-infrared colors, optical depths, CO indices, and dynamical masses are calculated. The near-infrared colors of the starburst nuclei are significantly redder than those observed in "normal" galaxies. Together, the Brγ and radio fluxes available for five of the galaxies imply that the starbursts are heavily obscured; an average extinction of A_V_~ 25 is derived. Strong CO absorption features indicate that late-type evolved stars are present in many of the starbursts. The average dynamical mass of the starburst region is found to be (1.0 +/- 0.4) x 10^9^ M_sun_.

  19. ALMA WILL DETERMINE THE SPECTROSCOPIC REDSHIFT z > 8 WITH FIR [O III] EMISSION LINES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Inoue, A. K.; Shimizu, I.; Tamura, Y.

    We investigate the potential use of nebular emission lines in the rest-frame far-infrared (FIR) for determining spectroscopic redshift of z > 8 galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA). After making a line emissivity model as a function of metallicity, especially for the [O III] 88 μm line which is likely to be the strongest FIR line from H II regions, we predict the line fluxes from high-z galaxies based on a cosmological hydrodynamics simulation of galaxy formation. Since the metallicity of galaxies reaches at ∼0.2 Z {sub ☉} even at z > 8 in our simulation, we expectmore » the [O III] 88 μm line as strong as 1.3 mJy for 27 AB objects, which is detectable at a high significance by <1 hr integration with ALMA. Therefore, the [O III] 88 μm line would be the best tool to confirm the spectroscopic redshifts beyond z = 8.« less

  20. The ring galaxy HRG 54 103: a first study

    NASA Astrophysics Data System (ADS)

    Faúndez-Abans, M.; Fernandes, I. F.; de Oliveira-Abans, M.; Poppe, P. C. R.; Martin, V. A. F.

    2009-12-01

    Aims: We report the first study of the peculiar ring galaxy HRG 54103 which was previously classified as a Saturn-like type galaxy. Methods: The study is based on low resolution spectroscopy and photometric observations in the optical band to highlight the characteristics of this almost isolated galaxy. The colour distribution of HRG 54103 was examined through direct CCD BVRI Kron-Cousins system imagery. Color-color diagrams of the bulge and ring are displayed and further compared with the star-forming ring galaxy HRG 2302. Results: The results of image enhancement of the morphological structure of this galaxy are discussed. The nuclear emission-line spectrum resembles that of a Seyfert2/LINER object, with z = 0.022 and heliocentric V = 6483 ± 18 km s-1, in agreement with the literature. The nuclear, bulge and ring section radial velocities along the ring major axis show a peculiar distribution, which together with the [N ii]/Hα and [S ii]/Hα ratios and image enhancement suggest an offset nucleus and an internal tilted ring or shell. Conclusions: HRG 54103 is a peculiar galaxy with an intermediate activity region, probably due to a residual excitation effect through the central AGN phenomenon. The individual sections of the color-color map are redder than a typical star-forming ring galaxy, in agreement with the behavior of the [S ii]/Hα versus [N ii]/Hα diagnostic diagram. The two bulge satellites, the plume-like appendix, and the disk-ring asymmetry suggest a possible merger event in the recent past of this object, which could also have caused its formation. Based on observations made at: (a) Observatório do Pico dos Dias, operated by MCT/Laboratório Nacional de Astrofísica, Brazil, and (b) Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, which are operated by AURA, Inc., under contract to the National Science Foundation.

  1. GREEN GALAXIES IN THE COSMOS FIELD

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pan, Zhizheng; Kong, Xu; Fan, Lulu, E-mail: panzz@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn

    2013-10-10

    We present research on the morphologies, spectra, and environments of ≈2350 'green valley' galaxies at 0.2 < z < 1.0 in the COSMOS field. The bimodality of dust-corrected NUV–r {sup +} color is used to define 'green valley'; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the red sequence. Morphological parameters of green galaxies are intermediate between those of blue and red galaxy populations, both on the Gini-asymmetry and the Gini-M{sub 20} planes. Approximately 60%-70% of green disk galaxies have intermediate or big bulges, and only 5%-10% are pure disk systems, basedmore » on morphological classification using the Zurich Estimator of Structural Types. The obtained average spectra of green galaxies are intermediate between blue and red ones in terms of [O II], Hα, and Hβ emission lines. Stellar population synthesis on the average spectra shows that green galaxies are on average older than blue galaxies but younger than red galaxies. Green galaxies and blue galaxies have similar projected galaxy density (Σ{sub 10}) distributions at z > 0.7. At z < 0.7, the fractions of M{sub *} < 10{sup 10.0} M{sub ☉} green galaxies located in a dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transitioning population between the blue cloud and the red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of active galactic nucleus feedback cannot be well constrained in our study. Finally, our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M{sub *} < 10{sup 10.0} M{sub ☉} blue galaxies into red galaxies, especially at z < 0.5.« less

  2. VizieR Online Data Catalog: Dwarf galaxies surface brightness profiles. II. (Herrmann+, 2016)

    NASA Astrophysics Data System (ADS)

    Herrmann, K. A.; Hunter, D. A.; Elmegreen, B. G.

    2016-07-01

    Our galaxy sample (see Table1) is derived from the survey of nearby (>30Mpc) late-type galaxies conducted by Hunter & Elmegreen 2006 (cat. J/ApJS/162/49). The full survey includes 94 dwarf Irregulars (dIms), 26 Blue Compact Dwarfs (BCDs), and 20 Magellanic-type spirals (Sms). The 141 dwarf sample presented in the first paper of the present series (Paper I; Herrmann et al. 2013, Cat. J/AJ/146/104) contains one fewer Sm galaxy and two additional dIm systems than the original survey. A multi-wavelength data set has been assembled for these galaxies. The data include Hα images (129 galaxies with detections) to trace star formation over the past 10Myr (Hunter & Elmegreen 2004, Cat. J/AJ/128/2170) and satellite UV images (61 galaxies observed) obtained with the Galaxy Evolution Explorer (GALEX) to trace star formation over the past ~200Myr. The GALEX data include images from two passbands with effective wavelengths of 1516Å (FUV) and 2267Å (NUV) and resolutions of 4'' and 5.6'', respectively. Three of the galaxies in our sample with NUV data do not have FUV data. To trace older stars we have UBV images, which are sensitive to stars formed over the past 1Gyr for on-going star formation, and images in at least one band of JHK for 40 galaxies in the sample, which integrates the star formation over the galaxy's lifetime. Note that nine dwarfs are missing UB data and three more are missing U-band data. In addition we made use of 3.6μm images (39 galaxies) obtained with the Infrared Array Camera (IRAC) in the Spitzer archives also to probe old stars. (3 data files).

  3. COMPARATIVE STUDY OF ASYMMETRY ORIGIN OF GALAXIES IN DIFFERENT ENVIRONMENTS. II. NEAR-INFRARED OBSERVATIONS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Plauchu-Frayn, I.; Coziol, R., E-mail: plauchuf@astro.ugto.m, E-mail: rcoziol@astro.ugto.m

    2010-08-15

    In this second paper of two analyses, we present near-infrared (NIR) morphological and asymmetry studies performed in a sample of 92 galaxies found in different density environments: galaxies in compact groups (CGs; HCGs in the Hickson Catalog of Compact Groups of Galaxies), isolated pairs of galaxies (KPGs in Karachentsev's list of isolated pairs of galaxies), and isolated galaxies (KIGs in Karachentseva's Catalog of Isolated Galaxies). Both studies have proved useful for identifying the effect of interactions on galaxies. In the NIR, the properties of the galaxies in HCGs, KPGs, and KIGs are more similar than they are in the optical.more » This is because the NIR band traces the older stellar populations, which formed earlier and are more relaxed than the younger populations. However, we found asymmetries related to interactions in both KPG and HCG samples. In HCGs, the fraction of asymmetric galaxies is even higher than what we found in the optical. In the KPGs the interactions look like very recent events, while in the HCGs galaxies are more morphologically evolved and show properties suggesting they suffered more frequent interactions. The key difference seems to be the absence of star formation in the HCGs; while interactions produce intense star formation in the KPGs, we do not see this effect in the HCGs. This is consistent with the dry merger hypothesis; the interaction between galaxies in CGs is happening without the presence of gas. If the gas was spent in stellar formation (to build the bulge of the numerous early-type galaxies), then the HCGs possibly started interacting sometime before the KPGs. On the other hand, the dry interaction condition in CGs suggests that the galaxies are on merging orbits, and consequently such system cannot be that much older either. Cosmologically speaking, the difference in formation time between pairs of galaxies and CGs may be relatively small. The two phenomena are typical of the formation of structures in low

  4. H II Regions in the Disks of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Rozas, M.

    1997-06-01

    The objective of the research presented in the thesis is to use photometrically calibrated high quality images in \\ha\\ of the disks of spiral galaxies to study their global star forming properties. In the first part of the study we catalog and study statistically the \\hii\\ regions in a set of spirals, imaged in \\ha\\ . The observed parameters of each region are its fluxes and diameters, from which we can also derive the mean surface brightness and its internal radial gradient (the latter for the largest most luminous regions). Plotting the luminosity function (LF) for a given galaxy (the number of regions versus \\ha\\ flux) we find a characteristic discontinuity: a peak accompanied by a change in gradient of the function, at a luminosity of 10$^{38.6}$ erg s$^{-1}$ per region. We attribute this to the change from ionization-bounded \\hii\\ regions, at luminosities below the transition, to density-bounded regions above the transition, and explain with a quantitative model based on this assumption why the transition takes place at a well-defined luminosity, and one which varies very little from galaxy to galaxy. In the six galaxies observed and analyzed in this way, the variance is 0.07 mag., making the transition a good prima facie candidate to be a powerful standard candle for accurate extragalactic distance measurements. Confirmation of the nature of the transition is provided by measurements of the internal brightness gradients, which show a jump from a constant value (predicted for ionization bounded regions) below the transition to a larger and increasing value above the transition. The theoretical model which can account for the transition was used to show how the gradients of the LF in the ionization bounded and the density bounded regimes can be used to derive the mass function of the ionizing stars in regions close to the transition luminosity, yielding a mean value for the slope of the MF in the galaxies observed of -2.4; the brightest stars in these

  5. The formation of giant low surface brightness galaxies

    NASA Technical Reports Server (NTRS)

    Hoffman, Yehuda; Silk, Joseph; Wyse, Rosemary F. G.

    1992-01-01

    It is demonstrated that the initial structure of galaxies can be strongly affected by their large-scale environments. In particular, rare (about 3 sigma) massive galaxies in voids will have normal bulges, but unevolved, extended disks; it is proposed that the low surface brightness objects Malin I and Malin II are prototypes of this class of object. The model predicts that searches for more examples of 'crouching giants' should be fruitful, but that such galaxies do not provide a substantial fraction of mass in the universe. The identification of dwarf galaxies is relatively unaffected by their environment.

  6. Demographics of Starbursts in Nearby Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Schinnerer, E.; Colbert, E.; Armus, L.; Scoville, N. Z.; Heckman, T.

    2002-12-01

    We investigate the frequency of circumnuclear starbursts in Seyfert galaxies using medium-resolution H and K band spectroscopy. An unbiased sample of ~20 nearby Seyfert galaxies was observed at the KeckII telescope with an average seeing of ~0.7''. Preliminary analysis shows strong stellar absorption lines for most galaxies in our sample. Comparison of stellar equivalent widths in the H and K band will allow us to determine the average age of the dominating stellar population. Evidence for an age trend with Seyfert type would provide a strong hint toward a starburst/AGN connection.

  7. A CCD Study of the Environment of Seyfert Galaxies. II. Testing the Interaction Hypothesis

    NASA Astrophysics Data System (ADS)

    De Robertis, M. M.; Yee, H. K. C.; Hayhoe, K.

    1998-03-01

    An analysis of the environment of a sample of 33 CfA Seyfert galaxies and a control sample of 45 nonactive galaxies matched in luminosity, redshift, and morphology to the Seyfert galaxies as reported in Paper I is presented. The covariance function amplitudes of the Seyfert and control samples are not statistically significantly different from one another and from the general field. Moreover, the companion frequency of the Seyfert galaxies, the probability of finding a companion galaxy brighter than -17.5 in R within 50 kpc (0.30 +/- 0.11), is not statistically significantly different from that for the nonactive control sample (0.23 +/- 0.09). The mean environment of Seyfert 1 galaxies is found to be different from that of Seyfert 2 galaxies at greater than the 95% confidence level, in the sense that the latter have a larger covariance amplitude. Such evidence is problematic for the Unified Model, which attributes spectroscopic differences between the classes to purely geometric effects on the order of parsec scales. It cannot, however, account for differences on the order of 100 kpc scales. It is argued that triggering of activity in galactic nuclei may involve a variety of mechanisms and may depend on the luminosity of the class. That is, while there is excellent evidence that QSOs, radio galaxies, and BL Lac objects inhabit environments significantly richer than the field, the same does not seem to be true for Seyfert galaxies and perhaps for LINERs. Finally, because a significant fraction of Seyfert host galaxies show little or no evidence for a recent merger, it is suggested that ``minor mergers,'' mergers that involve a gas-rich disk galaxy and a bound companion or satellite galaxy, may play a significant role in triggering activity in Seyfert galaxies.

  8. Are star formation rates of galaxies bimodal?

    NASA Astrophysics Data System (ADS)

    Feldmann, Robert

    2017-09-01

    Star formation rate (SFR) distributions of galaxies are often assumed to be bimodal with modes corresponding to star-forming and quiescent galaxies, respectively. Both classes of galaxies are typically studied separately, and SFR distributions of star-forming galaxies are commonly modelled as lognormals. Using both observational data and results from numerical simulations, I argue that this division into star-forming and quiescent galaxies is unnecessary from a theoretical point of view and that the SFR distributions of the whole population can be well fitted by zero-inflated negative binomial distributions. This family of distributions has three parameters that determine the average SFR of the galaxies in the sample, the scatter relative to the star-forming sequence and the fraction of galaxies with zero SFRs, respectively. The proposed distributions naturally account for (I) the discrete nature of star formation, (II) the presence of 'dead' galaxies with zero SFRs and (III) asymmetric scatter. Excluding 'dead' galaxies, the distribution of log SFR is unimodal with a peak at the star-forming sequence and an extended tail towards low SFRs. However, uncertainties and biases in the SFR measurements can create the appearance of a bimodal distribution.

  9. Ultraviolet to optical spectral distributions of northern star-forming galaxies

    NASA Technical Reports Server (NTRS)

    Mcquade, Kerry; Calzetti, Daniela; Kinney, Anne L.

    1995-01-01

    We report spectral energy distribution from the UV to the optical for a sample of 31 northern star-forming galaxies. We also present measurements for emission-line fluxes, continuum levels, and equivalent widths of absorption features for each individual spectrum as well as averages for the eight galactic activity classes, including normal, starburst, Seyfert 2, blue compact dwarf, blue compact, Low-Inonization Nuclear Emission Regions (LINER), H II, and combination LINER-H II galaxies.

  10. A New Scaling Relation for H II Regions in Spiral Galaxies: Unveiling the True Nature of the Mass-Metallicity Relation

    NASA Astrophysics Data System (ADS)

    Rosales-Ortega, F. F.; Sánchez, S. F.; Iglesias-Páramo, J.; Díaz, A. I.; Vílchez, J. M.; Bland-Hawthorn, J.; Husemann, B.; Mast, D.

    2012-09-01

    We demonstrate the existence of a local mass, metallicity, star formation relation using spatially resolved optical spectroscopy of H II regions in the local universe. One of the projections of this distribution—the local mass-metallicity relation—extends over a wide range in this parameter space: three orders of magnitude in mass and a factor of eight in metallicity. We explain the new relation as the combined effect of the differential distributions of mass and metallicity in the disks of galaxies, and a selective star formation efficiency. We use this local relation to reproduce—with a noticeable agreement—the mass-metallicity relation seen in galaxies, and conclude that the latter is a scale-up integrated effect of a local relation, supporting the inside-out growth and downsizing scenarios of galaxy evolution. Based on observations collected at the Centro Astronómico Hispano-Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).

  11. Deep spectroscopy of nearby galaxy clusters - II. The Hercules cluster

    NASA Astrophysics Data System (ADS)

    Agulli, I.; Aguerri, J. A. L.; Diaferio, A.; Dominguez Palmero, L.; Sánchez-Janssen, R.

    2017-06-01

    We carried out the deep spectroscopic observations of the nearby cluster A 2151 with AF2/WYFFOS@WHT. The caustic technique enables us to identify 360 members brighter than Mr = -16 and within 1.3R200. We separated the members into subsamples according to photometrical and dynamical properties such as colour, local environment and infall time. The completeness of the catalogue and our large sample allow us to analyse the velocity dispersion and the luminosity functions (LFs) of the identified populations. We found evidence of a cluster still in its collapsing phase. The LF of the red population of A 2151 shows a deficit of dwarf red galaxies. Moreover, the normalized LFs of the red and blue populations of A 2151 are comparable to the red and blue LFs of the field, even if the blue galaxies start dominating 1 mag fainter and the red LF is well represented by a single Schechter function rather than a double Schechter function. We discuss how the evolution of cluster galaxies depends on their mass: bright and intermediate galaxies are mainly affected by dynamical friction and internal/mass quenching, while the evolution of dwarfs is driven by environmental processes that need time and a hostile cluster environment to remove the gas reservoirs and halt the star formation.

  12. Hα Imaging of Nearby Seyfert Host Galaxies

    NASA Astrophysics Data System (ADS)

    Theios, Rachel L.; Malkan, Matthew A.; Ross, Nathaniel R.

    2016-05-01

    We used narrowband (Δλ = 70 Å) interference filters with the CCD imaging camera on the Nickel 1.0 m telescope at Lick Observatory to observe 31 nearby (z < 0.03) Seyfert galaxies in the 12 μm active galaxy sample. We obtained pure emission-line images of each galaxy, which reach down to a flux limit of 7.3 × 10-15 erg cm-2 s-1 arcsec-2, and corrected these images for [N II] emission and extinction. We separated the Hα emission line of the “nucleus” (central 100-1000 pc) from that of the host galaxy. The extended Hα emission is expected to be powered by newly formed hot stars, and indeed correlates well with other indicators of current star formation rates (SFRs) in these galaxies: extended 7.7 μm polycyclic aromatic hydrocarbon, total far-infrared, and radio luminosity. Relative to what would be expected from recent star formation, there is a 0.8 dex excess of radio emission in our Seyfert galaxies. The Hα luminosity we measured in the centers of our galaxies is dominated by the active galactic nucleus (AGN), and is linearly correlated with the hard X-ray luminosity. There is, however, an upward offset of 1 dex in this correlation for the Seyfert 1s, because their nuclear Hα emission includes a strong additional contribution from the broad-line region. We found a correlation between SFR and AGN luminosity. In spite of selection effects, we concluded that the absence of bright Seyfert nuclei in galaxies with low SFRs is real, albeit only weakly significant. Finally, we used our measured spatial distributions of Hα emission to determine what these Seyfert galaxies would look like when observed through fixed apertures (e.g., a spectroscopic fiber) at high redshifts. We found that although all of these Seyfert galaxies would be detectable emission-line galaxies at any redshift, most of them would appear to be dominated by (>67%) their H II region emission. Only the most luminous AGNs (log(L Hα /erg s-1) > 41.5) would still be identified as such at z

  13. A support vector machine for spectral classification of emission-line galaxies from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Shi, Fei; Liu, Yu-Yan; Sun, Guang-Lan; Li, Pei-Yu; Lei, Yu-Ming; Wang, Jian

    2015-10-01

    The emission-lines of galaxies originate from massive young stars or supermassive blackholes. As a result, spectral classification of emission-line galaxies into star-forming galaxies, active galactic nucleus (AGN) hosts, or compositions of both relates closely to formation and evolution of galaxy. To find efficient and automatic spectral classification method, especially in large surveys and huge data bases, a support vector machine (SVM) supervised learning algorithm is applied to a sample of emission-line galaxies from the Sloan Digital Sky Survey (SDSS) data release 9 (DR9) provided by the Max Planck Institute and the Johns Hopkins University (MPA/JHU). A two-step approach is adopted. (i) The SVM must be trained with a subset of objects that are known to be AGN hosts, composites or star-forming galaxies, treating the strong emission-line flux measurements as input feature vectors in an n-dimensional space, where n is the number of strong emission-line flux ratios. (ii) After training on a sample of emission-line galaxies, the remaining galaxies are automatically classified. In the classification process, we use a 10-fold cross-validation technique. We show that the classification diagrams based on the [N II]/Hα versus other emission-line ratio, such as [O III]/Hβ, [Ne III]/[O II], ([O III]λ4959+[O III]λ5007)/[O III]λ4363, [O II]/Hβ, [Ar III]/[O III], [S II]/Hα, and [O I]/Hα, plus colour, allows us to separate unambiguously AGN hosts, composites or star-forming galaxies. Among them, the diagram of [N II]/Hα versus [O III]/Hβ achieved an accuracy of 99 per cent to separate the three classes of objects. The other diagrams above give an accuracy of ˜91 per cent.

  14. VizieR Online Data Catalog: Chandra ACIS survey in nearby galaxies. II (Wang+, 2016)

    NASA Astrophysics Data System (ADS)

    Wang, S.; Qiu, Y.; Liu, J.; Bregman, J. N.

    2018-03-01

    Based on the recently completed Chandra/ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library of 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm with good statistics that the XLF slope flattens from lenticular (α{\\sim}1.50{\\pm}0.07) to elliptical ({\\sim}1.21{\\pm}0.02), to spirals ({\\sim}0.80{\\pm}0.02), to peculiars ({\\sim}0.55{\\pm}0.30), and to irregulars ({\\sim}0.26{\\pm}0.10). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosities for different types of galaxies. A radial dependency is found for ellipticals, with a flatter XLF slope for sources located between D25 and 2D25, suggesting the XLF slopes in the outer region of early-type galaxies are dominated by low-mass X-ray binaries in globular clusters. This study shows that the ULX rate in early-type galaxies is 0.24{\\pm}0.05 ULXs per surveyed galaxy, on a 5σ confidence level. The XLF for ULXs in late-type galaxies extends smoothly until it drops abruptly around 4x1040erg/s, and this break may suggest a mild boundary between the stellar black hole population possibly including 30M{\\sun} black holes with super-Eddington radiation and intermediate mass black holes. (1 data file).

  15. H-alpha Fabry-Perot interferometric observations of blue compact dwarf galaxies

    NASA Technical Reports Server (NTRS)

    Thuan, Trinh Xuan; Williams, T. B.; Malumuth, E.

    1987-01-01

    H-alpha Fabry-Perot interferometric observations of the two blue compact dwarf galaxies (BCDs) 7 Zw 403 and 1 Zw 49 are presented. The velocity field of 7 Zw 403 shows no clear large-scale organized motion but the velocity field is not completely chaotic either. The gas associated with the 8 H II regions in 7 Zw 403 has neither the highest nor lowest velocities. The BCD 1 Zw 49 is dominated by a single H II region which is about 50 times brighter than any other feature in the galaxy. There is a chain of fainter H II regions extending across the galaxy. The velocity field is well ordered along the H II region chain, but it is very complex around the dominant H II region, suggesting H-alpha loops and filaments around the latter. Both BCDs show velocity gradients of about 25 km/s on scales of about 10 pc in 7 Zw 403 and of about 50 pc in 1 Zw 49. These velocity discontinuities compress the gas and are probably responsible for the star formation.

  16. Halo histories versus galaxy properties at z = 0 II: large-scale galactic conformity

    NASA Astrophysics Data System (ADS)

    Tinker, Jeremy L.; Hahn, ChangHoon; Mao, Yao-Yuan; Wetzel, Andrew R.; Conroy, Charlie

    2018-06-01

    Using group catalogues from the Sloan Digital Sky Survey (SDSS) Data Release 7, we measure galactic conformity in the local universe. We measure the quenched fraction of neighbour galaxies around isolated primary galaxies, dividing the isolated sample into star-forming and quiescent objects. We restrict our measurements to scales >1 Mpc to probe the correlations between halo formation histories. Over the stellar mass range 109.7 ≤ M*/M⊙ ≤ 1010.9, we find minimal evidence for conformity. We further compare these data to predictions of the halo age-matching model, in which the oldest galaxies are associated with the oldest haloes. For models with strong correlations between halo and stellar age, the conformity is too large to be consistent with the data. Weaker implementations of the age-matching model would not produce a detectable signal in SDSS data. We reproduce the results of Kauffmann et al., in which the star formation rates of neighbour galaxies are reduced around primary galaxies when the primaries are low star formers. However, we find this result is mainly driven by contamination in the isolation criterion; when removing the small fraction of satellite galaxies in the sample, the conformity signal largely goes away. Lastly, we show that small conformity signals, i.e. 2-5 per cent differences in the quenched fractions of neighbour galaxies, can be produced by mechanisms other than halo assembly bias. For example, if passive galaxies occupy more massive haloes than star-forming galaxies of the same stellar mass, a conformity signal that is consistent with recent measurements from PRIMUS (Berti et al.) can be produced.

  17. VizieR Online Data Catalog: Luminosity and redshift of galaxies from WISE/SDSS (Toba+, 2014)

    NASA Astrophysics Data System (ADS)

    Toba, Y.; Oyabu, S.; Matsuhara, H.; Malkan, M. A.; Gandhi, P.; Nakagawa, T.; Isobe, N.; Shirahata, M.; Oi, N.; Ohyama, Y.; Takita, S.; Yamauchi, C.; Yano, K.

    2017-07-01

    We selected 12 and 22 um flux-limited galaxies based on the WISE (Cat. II/311) and SDSS (Cat. II/294) catalogs, and these galaxies were then classified into five types according to their optical spectroscopic information in the SDSS catalog. For spectroscopically classified galaxies, we constructed the luminosity functions using the 1/Vmax method, considering the detection limit of the WISE and SDSS catalogs. (1 data file).

  18. CHARACTERISTICS OF SPIRAL ARMS IN LATE-TYPE GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Honig, Z. N.; Reid, M. J., E-mail: mreid@cfa.harvard.edu

    2015-02-10

    We have measured the positions of large numbers of H II regions in four nearly face-on, late-type, spiral galaxies: NGC 628 (M74), NGC 1232, NGC 3184, and NGC 5194 (M51). Fitting log-periodic spiral models to segments of each arm yields local estimates of spiral pitch angle and arm width. While pitch angles vary considerably along individual arms, among arms within a galaxy, and among galaxies, we find no systematic trend with galactocentric distance. We estimate the widths of the arm segments from the scatter in the distances of the H II regions from the spiral model. All major arms in these galaxies show spiralmore » arm width increasing with distance from the galactic center, similar to the trend seen in the Milky Way. However, in the outermost parts of the galaxies, where massive star formation declines, some arms reverse this trend and narrow. We find that spiral arms often appear to be composed of segments of ∼5 kpc length, which join to form kinks and abrupt changes in pitch angle and arm width; these characteristics are consistent with properties seen in the large N-body simulations of D'Onghia et al. and others.« less

  19. A dwarf galaxy near the sight line to PKS 0454+0356 - A fading 'faint blue galaxy'?

    NASA Technical Reports Server (NTRS)

    Steidel, Charles C.; Dickinson, Mark; Bowen, David V.

    1993-01-01

    We report the discovery of a dwarf galaxy (MB = -17.2 for H0 = 50 km/s per Mpc) at z = 0.072 which is only 4 arcsec (3.7/h(100) kpc) in projection from the line of sight to the bright quasar PKS 0454+0356 (z(em) = 1.345). The dwarf has very blue optical and optical/IR colors and exhibits line emission indicative of ongoing or recent star formation. However, there is no detection of Ca II 3934 A, 3969 A absorption at z(abs) = 0.072 to equivalent width limits (3 sigma) of about 40 mA, which would suggest an H I column density along the line of sight of less than 5 x 10 exp 19/sq cm, if the Ca II/H I ratio is similar to sight lines in the Galaxy. Based on the absence of Ca II absorption and the unusually weak line emission given the very blue color of the dwarf, we speculate that it may be close to exhausting its supply of gas. As its star formation rate declines, the galaxy's blue magnitude should fade substantially, eventually reaching a quiescent state in accord with its K luminosity of about 0.005 L*. Future observations of the sight line to PKS 0454+0356 using HST in search of Mg II resonance lines, or a search for 21 cm absorption against the quasar radio continuum, could place even more stringent limits on the extent of the gas associated with an intrinsically faint, star-forming dwarf.

  20. Towards a library of synthetic galaxy spectra and preliminary results of classification and parametrization of unresolved galaxies for Gaia. II

    NASA Astrophysics Data System (ADS)

    Tsalmantza, P.; Kontizas, M.; Rocca-Volmerange, B.; Bailer-Jones, C. A. L.; Kontizas, E.; Bellas-Velidis, I.; Livanou, E.; Korakitis, R.; Dapergolas, A.; Vallenari, A.; Fioc, M.

    2009-09-01

    Aims: This paper is the second in a series, implementing a classification system for Gaia observations of unresolved galaxies. Our goals are to determine spectral classes and estimate intrinsic astrophysical parameters via synthetic templates. Here we describe (1) a new extended library of synthetic galaxy spectra; (2) its comparison with various observations; and (3) first results of classification and parametrization experiments using simulated Gaia spectrophotometry of this library. Methods: Using the PÉGASE.2 code, based on galaxy evolution models that take account of metallicity evolution, extinction correction, and emission lines (with stellar spectra based on the BaSeL library), we improved our first library and extended it to cover the domain of most of the SDSS catalogue. Our classification and regression models were support vector machines (SVMs). Results: We produce an extended library of 28 885 synthetic galaxy spectra at zero redshift covering four general Hubble types of galaxies, over the wavelength range between 250 and 1050 nm at a sampling of 1 nm or less. The library is also produced for 4 random values of redshift in the range of 0-0.2. It is computed on a random grid of four key astrophysical parameters (infall timescale and 3 parameters defining the SFR) and, depending on the galaxy type, on two values of the age of the galaxy. The synthetic library was compared and found to be in good agreement with various observations. The first results from the SVM classifiers and parametrizers are promising, indicating that Hubble types can be reliably predicted and several parameters estimated with low bias and variance.

  1. The Very Small Scale Clustering of SDSS-II and SDSS-III Galaxies

    NASA Astrophysics Data System (ADS)

    Piscionere, Jennifer

    2015-01-01

    We measure the angular clustering of galaxies from the Sloan Digital Sky Survey Data Release 7 in order to probe the spatial distribution of satellite galaxies within their dark matter halos. Specifically, we measure the angular correlation function on very small scales (7 - 320‧‧) in a range of luminosity threshold samples (absolute r-band magnitudes of -18 up to -21) that are constructed from the subset of SDSS that has been spectroscopically observed more than once (the so-called plate overlap region). We choose to measure angular clustering in this reduced survey footprint in order to minimize the effects of fiber collision incompleteness, which are otherwise substantial on these small scales. We model our clustering measurements using a fully numerical halo model that populates dark matter halos in N-body simulations to create realistic mock galaxy catalogs. The model has free parameters that specify both the number and spatial distribution of galaxies within their host halos. We adopt a flexible density profile for the spatial distribution of satellite galaxies that is similar to the dark matter Navarro-Frenk-White (NFW) profile, except that the inner slope is allowed to vary. We find that the angular clustering of our most luminous samples (Mr < -20 and -21) suggests that luminous satellite galaxies have substantially steeper inner density profiles than NFW. Lower luminosity samples are less constraining, however, and are consistent with satellite galaxies having shallow density profiles. Our results confirm the findings of Watson et al. (2012) while using different clustering measurements and modeling methodology. With the new SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS; Dawson et al., 2013), we can measure how the same class of galaxy evolves over time. The BOSS CMASS sample is of roughly constant stellar mass and number density out to z ˜ 0.6. The clustering of these samples appears to evolve very little with redshift, and each of the

  2. Galactic Outflows and Their Correlation with Galaxy Properties at 0.8 < z < 1.6

    NASA Astrophysics Data System (ADS)

    Whiting, Lindsey M.

    Out. ows have been shown to be ubiquitous in galaxies between z = 1 and z=2, and many models and observations have attempted to correlate the absorption line. properties of these out. ows with morphological characteristics of their host galaxies. In this study, we examined the spectra of 71 galaxies with redshifts 1< z<2, paying. particular attention to the FeII and MgII absorption lines. We plotted the equivalent. width, velocity, and maximum velocity of the absorption features against various. physical properties of the galaxies, obtained from catalogues created by Skelton et. al., (2014) and van der Wel et al., (2012). We conrmed the presence of out. ows in. our galaxy sample, and found a signicant trend between the equivalent width and. star formation rate - out. owing gas has stronger absorption lines in galaxies with. higher star formation rates.

  3. 2D modelling of the light distribution of early-type galaxies in a volume-limited sample - II. Results for real galaxies

    NASA Astrophysics Data System (ADS)

    D'Onofrio, M.

    2001-10-01

    In this paper we analyse the results of the two-dimensional (2D) fit of the light distribution of 73 early-type galaxies belonging to the Virgo and Fornax clusters, a sample volume- and magnitude-limited down to MB=-17.3, and highly homogeneous. In our previous paper (Paper I) we have presented the adopted 2D models of the surface-brightness distribution - namely the r1/n and (r1/n+exp) models - we have discussed the main sources of error affecting the structural parameters, and we have tested the ability of the chosen minimization algorithm (MINUIT) in determining the fitting parameters using a sample of artificial galaxies. We show that, with the exception of 11 low-luminosity E galaxies, the best fit of the real galaxy sample is always achieved with the two-component (r1/n+exp) model. The improvement in the χ2 due to the addition of the exponential component is found to be statistically significant. The best fit is obtained with the exponent n of the generalized r1/n Sersic law different from the classical de Vaucouleurs value of 4. Nearly 42 per cent of the sample have n<2, suggesting the presence of exponential `bulges' also in early-type galaxies. 20 luminous E galaxies are fitted by the two-component model, with a small central exponential structure (`disc') and an outer big spheroid with n>4. We believe that this is probably due to their resolved core. The resulting scalelengths Rh and Re of each component peak approximately at ~1 and ~2kpc, respectively, although with different variances in their distributions. The ratio Re/Rh peaks at ~0.5, a value typical for normal lenticular galaxies. The first component, represented by the r1/n law, is probably made of two distinct families, `ordinary' and `bright', on the basis of their distribution in the μe-log(Re) plane, a result already suggested by Capaccioli, Caon and D'Onofrio. The bulges of spirals and S0 galaxies belong to the `ordinary' family, while the large spheroids of luminous E galaxies form the

  4. OSO 8 X-ray spectra of clusters of galaxies. II - Discussion

    NASA Technical Reports Server (NTRS)

    Smith, B. W.; Mushotzky, R. F.; Serlemitsos, P. J.

    1979-01-01

    An observational description of X-ray clusters of galaxies is given based on OSO 8 X-ray results for spatially integrated spectra of 20 such clusters and various correlations obtained from these results. It is found from a correlation between temperature and velocity dispersion that the X-ray core radius should be less than the galaxy core radius or, alternatively, that the polytropic index is about 1.1 for most of the 20 clusters. Analysis of a correlation between temperature and emission integral yields evidence that more massive clusters accumulate a larger fraction of their mass as intracluster gas. Galaxy densities and optical morphology, as they correlate with X-ray properties, are reexamined for indications as to how mass injection by galaxies affects the density structure of the gas. The physical arguments used to derive iron abundances from observed equivalent widths of iron line features in X-ray spectra are critically evaluated, and the associated uncertainties in abundances derived in this manner are estimated to be quite large.

  5. Vacuum ultraviolet imagery of the Virgo Cluster region. II - Total far-ultraviolet flux of galaxies

    NASA Astrophysics Data System (ADS)

    Kodaira, K.; Watanabe, T.; Onaka, T.; Tanaka, W.

    1990-11-01

    The total flux in the far-ultraviolet region around 150 nm was measured for more than 40 galaxies in the central region of the Virgo Cluster, using two imaging telescopes on board a sounding rocket. The observed far-ultraviolet flux shows positive correlations with the H I 21 cm flux and the far-infrared flux for spiral galaxies, and with the X-ray flux and the radio continuum flux for elliptical galaxies. The former correlations of spiral galaxies are interpreted in terms of star formation activity, which indicates substantial depletion in the Virgo galaxies in accordance with the H I stripping. The latter correlations of elliptical galaxies indicate possible far-ultraviolet sources of young population, in addition to evolved hot stars. Far-ultraviolet fluxes from two dwarf elliptical galaxies were obtained tentatively, indicating star formation activity in elliptical galaxies. A high-resolution UV imagery by HST would be effective to distinguish the young population and the old population in elliptical galaxies.

  6. Chondritic Meteorites: Nebular and Parent-Body Formation Process

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Chondritic meteorites are the products of condensation, agglomeration and accretion of material in the solar nebula; these objects are the best sources of information regarding processes occurring during the early history of the solar system. We obtain large amounts of high-quality chemical and petrographic data and use them to infer chemical fractionation processes that occurred in the solar nebula and on meteorite parent bodies during thermal metamorphism, shock metamorphism and aqueous alteration. We compare diverse groups of chondrites and model their different properties in terms of processes that differed at different nebular locations or on different parent-bodies. In order to expand our set of geochemically important elements (particularly Si, C, P and S) and to distinguish the different oxidation states of Fe, Greg Kallemeyn spent three months (1 Sept. - 30 Nov. 1995) at the Smithsonian Institution to learn Eugene Jarosewich's wet chemical techniques. Key specimens from the recently established CK, CR and R chondrite groups were analyzed.

  7. How Do Type Ia Supernova Nebular Spectra Depend on Explosion Properties? Insights from Systematic Non-LTE Modeling

    NASA Astrophysics Data System (ADS)

    Botyánszki, János; Kasen, Daniel

    2017-08-01

    We present a radiative transfer code to model the nebular phase spectra of supernovae (SNe) in non-LTE (NLTE). We apply it to a systematic study of SNe Ia using parameterized 1D models and show how nebular spectral features depend on key physical parameters, such as the time since explosion, total ejecta mass, kinetic energy, radial density profile, and the masses of 56Ni, intermediate-mass elements, and stable iron-group elements. We also quantify the impact of uncertainties in atomic data inputs. We find the following. (1) The main features of SN Ia nebular spectra are relatively insensitive to most physical parameters. Degeneracy among parameters precludes a unique determination of the ejecta properties from spectral fitting. In particular, features can be equally well fit with generic Chandrasekhar mass ({M}{ch}), sub-{M}{Ch}, and super-{M}{Ch} models. (2) A sizable (≳0.1 {M}⊙ ) central region of stable iron-group elements, often claimed as evidence for {M}{Ch} models, is not essential to fit the optical spectra and may produce an unusual flat-top [Co III] profile. (3) The strength of [S III] emission near 9500 Å can provide a useful diagnostic of explosion nucleosynthesis. (4) Substantial amounts (≳0.1 {M}⊙ ) of unburned C/O mixed throughout the ejecta produce [O III] emission not seen in observations. (5) Shifts in the wavelength of line peaks can arise from line-blending effects. (6) The steepness of the ejecta density profile affects the line shapes, offering a constraint on explosion models. (7) Uncertainties in atomic data limit the ability to infer physical parameters.

  8. Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

    NASA Astrophysics Data System (ADS)

    Sanders, Ryan L.; Shapley, Alice E.; Zhang, Kai; Yan, Renbin

    2017-12-01

    Galaxy metallicity scaling relations provide a powerful tool for understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase oxygen abundances requires proper treatment of the various line-emitting sources within spectroscopic apertures. We present a model framework that treats galaxies as ensembles of H II and diffuse ionized gas (DIG) regions of varying metallicities. These models are based upon empirical relations between line ratios and electron temperature for H II regions, and DIG strong-line ratio relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG contamination can significantly affect properties inferred from global galaxy spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We use observationally motivated inputs to construct a model matched to typical local star-forming galaxies, and quantify the biases in strong-line ratios, electron temperatures, and direct-method metallicities as inferred from global galaxy spectra relative to the median values of the H II region distributions in each galaxy. We also provide a generalized set of models that can be applied to individual galaxies or galaxy samples in atypical regions of parameter space. We use these models to correct for the effects of flux-weighting and DIG contamination in the local direct-method mass-metallicity and fundamental metallicity relations, and in the mass-metallicity relation based on strong-line metallicities. Future photoionization models of galaxy line emission need to include DIG emission and represent galaxies as ensembles of emitting regions with varying metallicity, instead of as single H II regions with effective properties, in order to obtain unbiased estimates of key underlying physical properties.

  9. Galaxy and Mass Assembly (GAMA): active galactic nuclei in pairs of galaxies

    NASA Astrophysics Data System (ADS)

    Gordon, Yjan A.; Owers, Matt S.; Pimbblet, Kevin A.; Croom, Scott M.; Alpaslan, Mehmet; Baldry, Ivan K.; Brough, Sarah; Brown, Michael J. I.; Cluver, Michelle E.; Conselice, Christopher J.; Davies, Luke J. M.; Holwerda, Benne W.; Hopkins, Andrew M.; Gunawardhana, Madusha L. P.; Loveday, Jonathan; Taylor, Edward N.; Wang, Lingyu

    2017-03-01

    There exist conflicting observations on whether or not the environment of broad- and narrow-line active galatic nuclei (AGN) differ and this consequently questions the validity of the AGN unification model. The high spectroscopic completeness of the Galaxy and Mass Assembly (GAMA) survey makes it ideal for a comprehensive analysis of the close environment of galaxies. To exploit this, and conduct a comparative analysis of the environment of broad- and narrow-line AGN within GAMA, we use a double-Gaussian emission line fitting method to model the more complex line profiles associated with broad-line AGN. We select 209 type 1 (I.e. unobscured), 464 type 1.5-1.9 (partially obscured), and 281 type 2 (obscured) AGN within the GAMA II data base. Comparing the fractions of these with neighbouring galaxies out to a pair separation of 350 kpc h-1 and Δz < 0.012 shows no difference between AGN of different type, except at separations less than 20 kpc h-1 where our observations suggest an excess of type 2 AGN in close pairs. We analyse the properties of the galaxies neighbouring our AGN and find no significant differences in colour or the star formation activity of these galaxies. Further to this, we find that Σ5 is also consistent between broad- and narrow-line AGN. We conclude that the observations presented here are consistent with AGN unification.

  10. The PAndAS View of the Andromeda Satellite System. II. Detailed Properties of 23 M31 Dwarf Spheroidal Galaxies

    NASA Astrophysics Data System (ADS)

    Martin, Nicolas F.; Ibata, Rodrigo A.; Lewis, Geraint F.; McConnachie, Alan; Babul, Arif; Bate, Nicholas F.; Bernard, Edouard; Chapman, Scott C.; Collins, Michelle M. L.; Conn, Anthony R.; Crnojević, Denija; Fardal, Mark A.; Ferguson, Annette M. N.; Irwin, Michael; Mackey, A. Dougal; McMonigal, Brendan; Navarro, Julio F.; Rich, R. Michael

    2016-12-01

    We present a comprehensive analysis of the structural properties and luminosities of the 23 dwarf spheroidal galaxies that fall within the footprint of the Pan-Andromeda Archaeological Survey (PAndAS). These dwarf galaxies represent the large majority of Andromeda’s known satellite dwarf galaxies and cover a wide range in luminosity (-11.6≲ {M}V≲ -5.8 or {10}4.2≲ L≲ {10}6.5 {L}⊙ ) and surface brightness (25.1≲ {μ }0≲ 29.3 mag arcsec-2). We confirm most previous measurements, but we find And XIX to be significantly larger than before ({r}h={3065}-935+1065 {pc}, {M}V=-{10.1}-0.4+0.8) and cannot derive parameters for And XXVII as it is likely not a bound stellar system. We also significantly revise downward the luminosities of And XV and And XVI, which are now {M}V˜ -7.5 or L˜ {10}5 {L}⊙ . Finally, we provide the first detailed analysis of Cas II/And XXX, a fairly faint system ({M}V=-{8.0}-0.3+0.4) of typical size ({r}h=270+/- 50 {pc}), located in close proximity to the two bright elliptical dwarf galaxies NGC 147 and NGC 185. Combined with the set of homogeneous distances published in an earlier contribution, our analysis dutifully tracks all relevant sources of uncertainty in the determination of the properties of the dwarf galaxies from the PAndAS photometric catalog. We further publish the posterior probability distribution functions of all the parameters we fit for in the form of MCMC chains available online; these inputs should be used in any analysis that aims to remain truthful to the data and properly account for covariance between parameters.

  11. A Study of Galaxies and Quasars in the Background of the Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Dhara, Atirath; McConnell, Kaela; Guhathakurta, Puragra; Roy, Namrata; Waite, Jurij

    2018-01-01

    The SPLASH (Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo) survey is based on wide-field ground-based optical images (KPNO 4-m/Mosaic, CFHT 3.6-m/MegaCam imager, and Subaru 8-m/Suprime-Cam), deep Hubble Space Telescope ultraviolet/optical/near infrared images (ACS and WFC3), and medium resolution spectra (Keck II 10-m/DEIMOS). The SPLASH survey data set contains two main categories of (non-M31) contaminants (SPLASH trash, if you will): foreground Milky Way stars and compact background galaxies/quasars. In this poster, we present the discovery and characterization of galaxies and quasars behind M31. Such objects were identified based on the presence of redshifted emission lines and other galaxy/quasar spectral features (e.g., Ca H+K absorption and IGM absorption). The redshift of each galaxy was measured by cross-correlating its spectrum against an emission line galaxy spectral template. The cross-correlation results (spectrum and best-fit template) were visually inspected to identify cases of incorrect matching of emission lines. Many of these incorrect redshift estimates were corrected by using the second or third highest cross-correlation peak. Quasar redshifts were determined based on cross-correlation against a quasar spectral template. Most of the galaxies in our sample are star forming galaxies with strong emission lines. We analyze their emission line flux ratios in a BPT diagram to learn more about the ionization source and metallicity. Finally, the properties of these compact galaxies behind M31 are compared to those of galaxies selected in a more standard way in the DEEP2 redshift survey to explore the effects of morphological pre-selection (compact vs. extended) on the properties of the resulting galaxy sample.This research was supported by NASA/STScI and the National Science Foundation. Most of this work was carried out by high school students working under the auspices of the Science Internship Program (SIP) at UC Santa Cruz.

  12. The Luminous Polycyclic Aromatic Hydrocarbon Emission Features: Applications to High Redshift Galaxies and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Shipley, Heath V.

    2016-01-01

    For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.4, with mid-IR spectroscopy from the Spitzer Infrared Spectrograph (IRS), and data covering other SFR indicators (Hα emission and rest-frame 24μm continuum emission). The PAH luminosity correlates linearly with the SFR as measured by the Hα luminosity (corrected for attenuation using the mono-chromatic rest-frame 24μm emission), with a tight scatter of <0.15 dex. The scatter is comparable to that between SFRs derived from the Paα and dust-corrected Hα emission lines. We present a case study in advance of JWST, which will be capable of measuring SFRs (from 8μm rest-frame photometry, i.e. PAHs) in distant galaxies (z ≤ 2) with JWST/MIRI to SFRs as low as ~10 M⊙yr-1, because the PAH features are so bright. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs that agree with

  13. New observations and a photographic atlas of polar-ring galaxies

    NASA Technical Reports Server (NTRS)

    Whitmore, Bradley C.; Lucas, Ray A.; Mcelroy, Douglas B.; Steiman-Cameron, Thomas Y.; Sackett, Penny D.

    1990-01-01

    A photographic atlas of polar-ring galaxies and related objects is presented. The atlas includes kinematically confirmed polar-ring galaxies (category A), good candidates based on their morphological appearance (category B), possible candidates (category C), and possibly related objects (category D). New photometric and kinematic observations are reported for several galaxies in the catalog, including observations that show that UGC 7576 and UGC 9796 ( = II ZW 73) are S0 galaxies with polar rings. Roughly 0.5 percent of all nearby S0 galaxies appear to have polar rings. When corrected for various selection effects (e.g., nonoptimal viewing orientation, possible dimming, or limited lifetime of the ring) the percentage increases to about 5 percent of S0 galaxies which have, or have had a polar ring.

  14. NEAR-INFRARED SPECTROSCOPY OF NEARBY SEYFERT GALAXIES: IS THERE EVIDENCE FOR SHOCK EXCITATION IN NARROW-LINE REGIONS?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Terao, K.; Nagao, T.; Toba, Y.

    2016-12-20

    One of the important unsettled problems regarding active galactic nuclei (AGNs) is the major ionization mechanism of gas clouds in AGN narrow-line regions (NLRs). In order to investigate this issue, we present our J -band spectroscopic observations of a sample of 26 nearby Seyfert galaxies. In our study, we use the flux ratio of the following two forbidden emission lines, [Fe ii]1.257  μ m and [P ii]1.188  μ m, because it is known that this ratio is sensitive to the ionization mechanism. We obtain the [Fe ii]/[P ii] flux ratio or its lower limit for 19 objects. In addition tomore » our data, we compile this flux ratio (or its lower limit) for 23 nearby Seyfert galaxies from the literature. Based on the collected data, we find that three Seyfert galaxies show very large lower limits of the [Fe ii]/[P ii] flux ratios (≳10): NGC 2782, NGC 5005, and Mrk 463. It is thus suggested that the contribution of the fast shock in the gas excitation is significantly large for them. However, more than half of the Seyfert galaxies in our sample show moderate [Fe ii]/[P ii] flux ratios (∼2), which is consistent with pure photoionization by power-law ionizing continuum emission. We also find that the [Fe ii]/[P ii] flux ratio shows no clear correlation with the radio loudness, suggesting that the radio jet is not the primary origin of shocks in NLRs of Seyfert galaxies.« less

  15. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 3: Brightness profiles

    NASA Technical Reports Server (NTRS)

    Ferrarese, Laura; Bosch, Frank C. Van Den; Ford, Holland C.; Jaffe, Walter; O'Connell, Robert W.

    1994-01-01

    We have used the Planetary Camera on the Hubble Space Telescope (HST) to study the morphology and surface brightness parameters of a luminosity-limited sample of fourteen elliptical galaxies in the Virgo cluster. The total apparent blue magnitudes of the galaxies range between 9.4 and 13.4. In this paper, the core brightness profiles are presented, while the overall morphology and the isophotal shapes are discussed in two companion papers (Jaffe et al. (1994); van den Bosch et al. (1994)). We show that, in spite of the spherical aberration affecting the HST primary mirror, deconvolution techniques allow recovery of the brightness profile up to 0.2 arcsec from the center of the galaxies. We find that none of the galaxies has an isothermal core. On the basis of their morphological and photometrical properties, the galaxies can be divided in two physically distinct groups, referred to as Type I and Type II. All of the Type I galaxies are classified as E1 to E3 in the Revised Shapley Ames Catalog (Sandage & Tammann 1981), while Type II galaxies are classified as E5 to E7. The characteristics of Type II galaxies are explained by the presence of disks component on both the 1 arcsec and the 10 arcsec scales, while Type I galaxies correspond to the classical disk-free ellipticals.

  16. THE {gamma}-RAY EMISSION REGION IN THE FANAROFF-RILEY II RADIO GALAXY 3C 111

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grandi, P.; Torresi, E.; Stanghellini, C., E-mail: grandi@iasfbo.inaf.it, E-mail: torresi@iasfbo.inaf.it, E-mail: cstan@ira.inaf.it

    The broad-line radio galaxy 3C 111, characterized by a Fanaroff-Riley II (FRII) radio morphology, is one of the sources of the misaligned active galactic nucleus sample, consisting of radio galaxies and steep spectrum radio quasars, recently detected by the Fermi Large Area Telescope (LAT). Our analysis of the 24 month {gamma}-ray light curve shows that 3C 111 was only occasionally detected at high energies. It was bright at the end of 2008 and faint, below the Fermi-LAT sensitivity threshold, for the rest of the time. A multifrequency campaign of 3C 111, ongoing in the same period, revealed an increase ofmore » the millimeter, optical, and X-ray fluxes in 2008 September-November, interpreted by Chatterjee et al. as due to the passage of a superluminal knot through the jet core. The temporal coincidence of the millimeter-optical-X-ray outburst with the GeV activity suggests a cospatiality of the events, allowing, for the first time, the localization of the {gamma}-ray dissipative zone in an FRII jet. We argue that the GeV photons of 3C 111 are produced in a compact region confined within 0.1 pc and at a distance of about 0.3 pc from the black hole.« less

  17. Galaxy modelling. II. Multi-wavelength faint counts from a semi-analytic model of galaxy formation

    NASA Astrophysics Data System (ADS)

    Devriendt, J. E. G.; Guiderdoni, B.

    2000-11-01

    This paper predicts self-consistent faint galaxy counts from the UV to the submm wavelength range. The stardust spectral energy distributions described in Devriendt et al. \\citeparyear{DGS99} (Paper I) are embedded within the explicit cosmological framework of a simple semi-analytic model of galaxy formation and evolution. We begin with a description of the non-dissipative and dissipative collapses of primordial perturbations, and plug in standard recipes for star formation, stellar evolution and feedback. We also model the absorption of starlight by dust and its re-processing in the IR and submm. We then build a class of models which capture the luminosity budget of the universe through faint galaxy counts and redshift distributions in the whole wavelength range spanned by our spectra. In contrast with a rather stable behaviour in the optical and even in the far-IR, the submm counts are dramatically sensitive to variations in the cosmological parameters and changes in the star formation history. Faint submm counts are more easily accommodated within an open universe with a low value of Omega_0 , or a flat universe with a non-zero cosmological constant. We confirm the suggestion of Guiderdoni et al. \\citeparyear{GHBM98} that matching the current multi-wavelength data requires a population of heavily-extinguished, massive galaxies with large star formation rates ( ~ 500 M_sun yr-1) at intermediate and high redshift (z >= 1.5). Such a population of objects probably is the consequence of an increase of interaction and merging activity at high redshift, but a realistic quantitative description can only be obtained through more detailed modelling of such processes. This study illustrates the implementation of multi-wavelength spectra into a semi-analytic model. In spite of its simplicity, it already provides fair fits of the current data of faint counts, and a physically motivated way of interpolating and extrapolating these data to other wavelengths and fainter flux

  18. DISCOVERY OF A GAS-RICH COMPANION TO THE EXTREMELY METAL-POOR GALAXY DDO 68

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cannon, John M.; Alfvin, Erik D.; Johnson, Megan

    2014-05-20

    We present H I spectral-line imaging of the extremely metal-poor galaxy DDO 68. This system has a nebular oxygen abundance of only ∼3% Z {sub ☉}, making it one of the most metal-deficient galaxies known in the local volume. Surprisingly, DDO 68 is a relatively massive and luminous galaxy for its metal content, making it a significant outlier in the mass-metallicity and luminosity-metallicity relationships. The origin of such a low oxygen abundance in DDO 68 presents a challenge for models of the chemical evolution of galaxies. One possible solution to this problem is the infall of pristine neutral gas, potentially initiated during amore » gravitational interaction. Using archival H I spectral-line imaging obtained with the Karl G. Jansky Very Large Array, we have discovered a previously unknown companion of DDO 68. This low-mass (M{sub H} {sub I} = 2.8 × 10{sup 7} M {sub ☉}), recently star-forming (SFR{sub FUV} = 1.4 × 10{sup –3} M {sub ☉} yr{sup –1}, SFR{sub Hα} < 7 × 10{sup –5} M {sub ☉} yr{sup –1}) companion has the same systemic velocity as DDO 68 (V {sub sys} = 506 km s{sup –1}; D = 12.74 ± 0.27 Mpc) and is located at a projected distance of ∼42 kpc. New H I maps obtained with the 100 m Robert C. Byrd Green Bank Telescope provide evidence that DDO 68 and this companion are gravitationally interacting at the present time. Low surface brightness H I gas forms a bridge between these objects.« less

  19. Broad [C II] Line Wings as Tracer of Molecular and Multi-phase Outflows in Infrared Bright Galaxies

    NASA Astrophysics Data System (ADS)

    Janssen, A. W.; Christopher, N.; Sturm, E.; Veilleux, S.; Contursi, A.; González-Alfonso, E.; Fischer, J.; Davies, R.; Verma, A.; Graciá-Carpio, J.; Genzel, R.; Lutz, D.; Sternberg, A.; Tacconi, L.; Burtscher, L.; Poglitsch, A.

    2016-05-01

    We report a tentative correlation between the outflow characteristics derived from OH absorption at 119 μm and [C II] emission at 158 μm in a sample of 22 local and bright ultraluminous infrared galaxies (ULIRGs). For this sample, we investigate whether [C II] broad wings are a good tracer of molecular outflows, and how the two tracers are connected. Fourteen objects in our sample have a broad wing component as traced by [C II], and all of these also show OH119 absorption indicative of an outflow (in one case an inflow). The other eight cases, where no broad [C II] component was found, are predominantly objects with no OH outflow or a low-velocity (≤100 km s-1) OH outflow. The FWHM of the broad [C II] component shows a trend with the OH119 blueshifted velocity, although with significant scatter. Moreover, and despite large uncertainties, the outflow masses derived from OH and broad [C II] show a 1:1 relation. The main conclusion is therefore that broad [C II] wings can be used to trace molecular outflows. This may be particularly relevant at high redshift, where the usual tracers of molecular gas (like low-J CO lines) become hard to observe. Additionally, observations of blueshifted Na I D λλ 5890, 5896 absorption are available for 10 of our sources. Outflow velocities of Na I D show a trend with OH velocity and broad [C II] FWHM. These observations suggest that the atomic and molecular gas phases of the outflow are connected.

  20. Interactions of galaxies outside clusters and massive groups

    NASA Astrophysics Data System (ADS)

    Yadav, Jaswant K.; Chen, Xuelei

    2018-06-01

    We investigate the dependence of physical properties of galaxies on small- and large-scale density environment. The galaxy population consists of mainly passively evolving galaxies in comparatively low-density regions of Sloan Digital Sky Survey (SDSS). We adopt (i) local density, ρ _{20}, derived using adaptive smoothing kernel, (ii) projected distance, r_p, to the nearest neighbor galaxy and (iii) the morphology of the nearest neighbor galaxy as various definitions of environment parameters of every galaxy in our sample. In order to detect long-range interaction effects, we group galaxy interactions into four cases depending on morphology of the target and neighbor galaxies. This study builds upon an earlier study by Park and Choi (2009) by including improved definitions of target and neighbor galaxies, thus enabling us to better understand the effect of "the nearest neighbor" interaction on the galaxy. We report that the impact of interaction on galaxy properties is detectable at least up to the pair separation corresponding to the virial radius of (the neighbor) galaxies. This turns out to be mostly between 210 and 360 h^{-1}kpc for galaxies included in our study. We report that early type fraction for isolated galaxies with r_p > r_{vir,nei} is almost ignorant of the background density and has a very weak density dependence for closed pairs. Star formation activity of a galaxy is found to be crucially dependent on neighbor galaxy morphology. We find star formation activity parameters and structure parameters of galaxies to be independent of the large-scale background density. We also exhibit that changing the absolute magnitude of the neighbor galaxies does not affect significantly the star formation activity of those target galaxies whose morphology and luminosities are fixed.

  1. The Lopsidedness of Satellite Galaxy Systems in ΛCDM Simulations

    NASA Astrophysics Data System (ADS)

    Pawlowski, Marcel S.; Ibata, Rodrigo A.; Bullock, James S.

    2017-12-01

    The spatial distribution of satellite galaxies around pairs of galaxies in the Sloan Digital Sky Survey (SDSS) have been found to bulge significantly toward the respective partner. Highly anisotropic, planar distributions of satellite galaxies are in conflict with expectations derived from cosmological simulations. Does the lopsided distribution of satellite systems around host galaxy pairs constitute a similar challenge to the standard model of cosmology? We investigate whether such satellite distributions are present around stacked pairs of hosts extracted from the ΛCDM simulations Millennium-I, Millennium-II, Exploring the Local Volume in Simulations, and Illustris-1. By utilizing this set of simulations covering different volumes, resolutions, and physics, we implicitly test whether a lopsided signal exists for different ranges of satellite galaxy masses, and whether the inclusion of hydrodynamical effects produces significantly different results. All simulations display a lopsidedness similar to the observed situation. The signal is highly significant for simulations containing a sufficient number of hosts and resolved satellite galaxies (up to 5 σ for Millennium-II). We find a projected signal that is up to twice as strong as that reported for the SDSS systems for certain opening angles (∼16% more satellites in the direction between the pair than expected for uniform distributions). Considering that the SDSS signal is a lower limit owing to likely back- and foreground contamination, the ΛCDM simulations appear to be consistent with this particular empirical property of galaxy pairs.

  2. The host dark matter haloes of [O II] emitters at 0.5 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Gonzalez-Perez, V.; Comparat, J.; Norberg, P.; Baugh, C. M.; Contreras, S.; Lacey, C.; McCullagh, N.; Orsi, A.; Helly, J.; Humphries, J.

    2018-03-01

    Emission line galaxies (ELGs) are used in several ongoing and upcoming surveys (SDSS-IV/eBOSS, DESI) as tracers of the dark matter distribution. Using a new galaxy formation model, we explore the characteristics of [O II] emitters, which dominate optical ELG selections at z ≃ 1. Model [O II] emitters at 0.5 < z < 1.5 are selected to mimic the DEEP2, VVDS, eBOSS and DESI surveys. The luminosity functions of model [O II] emitters are in reasonable agreement with observations. The selected [O II] emitters are hosted by haloes with Mhalo ≥ 1010.3h-1M⊙, with ˜90 per cent of them being central star-forming galaxies. The predicted mean halo occupation distributions of [O II] emitters have a shape typical of that inferred for star-forming galaxies, with the contribution from central galaxies, < N > _{[O II] cen}, being far from the canonical step function. The < N > _{[O II] cen}} can be described as the sum of an asymmetric Gaussian for discs and a step function for spheroids, which plateau below unity. The model [O II] emitters have a clustering bias close to unity, which is below the expectations for eBOSS and DESI ELGs. At z ˜ 1, a comparison with observed g-band-selected galaxy, which is expected to be dominated by [O II] emitters, indicates that our model produces too few [O II] emitters that are satellite galaxies. This suggests the need to revise our modelling of hot gas stripping in satellite galaxies.

  3. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Barrows, R. Scott; Comerford, Julia M.; Greene, Jenny E.

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence formore » a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (∼0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.« less

  4. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    NASA Astrophysics Data System (ADS)

    Barrows, R. Scott; Comerford, Julia M.; Greene, Jenny E.; Pooley, David

    2017-04-01

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (˜0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.

  5. LBT/LUCIFER Observations of the z ~ 2 Lensed Galaxy J0900+2234

    NASA Astrophysics Data System (ADS)

    Bian, Fuyan; Fan, Xiaohui; Bechtold, Jill; McGreer, Ian D.; Just, Dennis W.; Sand, David J.; Green, Richard F.; Thompson, David; Peng, Chien Y.; Seifert, Walter; Ageorges, Nancy; Juette, Marcus; Knierim, Volker; Buschkamp, Peter

    2010-12-01

    We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z = 2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared (NIR) instrument mounted on the Large Binocular Telescope. We fitted lens models to the rest-frame optical images and found that the galaxy has an intrinsic effective radius of 7.4 ± 0.8 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high signal-to-noise ratio rest-frame spectra covered by the H + K band, we detected Hβ, [O III], Hα, [N II], and [S II] emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction toward the ionized H II regions (Eg (B - V)) was computed from the flux ratio of Hα and Hβ and appears to be much higher than that toward the stellar continuum (Es (B - V)), derived from the optical and NIR broadband photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of 1/5-1/3 solar abundance, which is much lower than for typical z ~ 2 star-forming galaxies. From the flux ratio of [S II]λ6717 and [S II]λ6732, we found that the electron number density of the H II regions in the high-z galaxy was sime1000 cm-3, consistent with other z ~ 2 galaxies but much higher than that in local H II regions. The star formation rate was estimated via the Hα luminosity, after correction for the lens magnification, to be about 365 ± 69 M sun yr-1. Combining the FWHM of Hα emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 ± 0.9) × 1010 M sun. The gas mass is (5.1 ± 1.1) × 1010 M sun from the Hα flux surface density using global Kennicutt-Schmidt law, indicating a very high gas fraction of 0.79 ± 0.19 in J0900+2234. Based on data acquired

  6. DETERMINING THE LARGE-SCALE ENVIRONMENTAL DEPENDENCE OF GAS-PHASE METALLICITY IN DWARF GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Douglass, Kelly A.; Vogeley, Michael S., E-mail: kelly.a.douglass@drexel.edu

    2017-01-10

    We study how the cosmic environment affects galaxy evolution in the universe by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the fluxes of emission lines, particularly those of the forbidden [O iii] and [S ii] transitions, provide estimates of a region’s electron temperature and number density. From these two quantities and the emission line fluxes [O ii] λ 3727, [O iii] λ 4363, and [O iii] λλ 4959, 5007, we estimate the abundance of oxygen with the direct T{sub e}  method. We estimate the metallicity of 42 blue, star-forming voidmore » dwarf galaxies and 89 blue, star-forming dwarf galaxies in more dense regions using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, as reprocessed in the MPA-JHU value-added catalog. We find very little difference between the two sets of galaxies, indicating little influence from the large-scale environment on their chemical evolution. Of particular interest are a number of extremely metal-poor dwarf galaxies that are less prevalent in voids than in the denser regions.« less

  7. Weighing Galaxy Clusters with Gas. II. On the Origin of Hydrostatic Mass Bias in ΛCDM Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Nelson, Kaylea; Lau, Erwin T.; Nagai, Daisuke; Rudd, Douglas H.; Yu, Liang

    2014-02-01

    The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (lsim 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

  8. Chemical enrichment in isolated barred spiral galaxies.

    NASA Astrophysics Data System (ADS)

    Martel, Hugo; Carles, Christian; Robichaud, Fidéle; Ellison, Sara L.; Williamson, David J.

    2018-04-01

    To investigate the role of bars in the chemical evolution of isolated disc galaxies, we performed a series of 39 gas dynamical simulations of isolated barred and unbarred galaxies with various masses, initial gas fractions, and AGN feedback models. The presence of a bar drives a substantial amount of gas toward the central region of the galaxy. In the most massive galaxies, this results in a violent starburst, followed by a drop in star formation resulting from gas exhaustion. The time delay between Type Ia and Type II supernovae explosions means that barred galaxies experience a rapid increase in [O/H] in the central region, and a much more gradual increase in [Fe/H]. In unbarred galaxies, star formation proceeds at a slow and steady rate, and oxygen and iron are produced at steady rates which are similar except for a time offset. Comparing the abundance ratios in barred and unbarred galaxies with the same central stellar mass M*, we find in barred galaxies an enhancement of 0.07 dex in [O/H], 0.05 dex in [Fe/H], and 0.05 dex in [O/Fe]. The [O/H] enhancement is in excellent agreement with observations from the SDSS. The initial gas fraction has very little effect on the abundance ratios in barred and unbarred galaxies, unless the galaxies experience a starburst. We considered AGN-host galaxies located near the bottom of the AGN regime, M* ≳ 3 × 1010M⊙, where AGN feedback dominates over supernovae feedback. We found that the impact of AGN feedback on the central abundances is marginal.

  9. Dark-ages reionization and galaxy formation simulation V: morphology and statistical signatures of reionization

    NASA Astrophysics Data System (ADS)

    Geil, Paul M.; Mutch, Simon J.; Poole, Gregory B.; Angel, Paul W.; Duffy, Alan R.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2016-10-01

    We use the Dark-ages, Reionization And Galaxy formation Observables from Numerical Simulations (DRAGONS) framework to investigate the effect of galaxy formation physics on the morphology and statistics of ionized hydrogen (H II) regions during the Epoch of Reioinization (EoR). DRAGONS self-consistently couples a semi-analytic galaxy formation model with the inhomogeneous ionizing UV background, and can therefore be used to study the dependence of morphology and statistics of reionization on feedback phenomena of the ionizing source galaxy population. Changes in galaxy formation physics modify the sizes of H II regions and the amplitude and shape of 21-cm power spectra. Of the galaxy physics investigated, we find that supernova feedback plays the most important role in reionization, with H II regions up to ≈20 per cent smaller and a fractional difference in the amplitude of power spectra of up to ≈17 per cent at fixed ionized fraction in the absence of this feedback. We compare our galaxy formation-based reionization models with past calculations that assume constant stellar-to-halo mass ratios and find that with the correct choice of minimum halo mass, such models can mimic the predicted reionization morphology. Reionization morphology at fixed neutral fraction is therefore not uniquely determined by the details of galaxy formation, but is sensitive to the mass of the haloes hosting the bulk of the ionizing sources. Simple EoR parametrizations are therefore accurate predictors of reionization statistics. However, a complete understanding of reionization using future 21-cm observations will require interpretation with realistic galaxy formation models, in combination with other observations.

  10. Revisiting The First Galaxies: The effects of Population III stars on their host galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Muratov, Alexander L.; Gnedin, Oleg Y.; Gnedin, Nickolay Y.

    2013-07-12

    We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the adaptive refinement tree code. Our simulations feature a recently developed model for H 2 formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III (Pop III) stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch duringmore » which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies that host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 10 8 years after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with a total mass in excess of 3 × 10 6 M ⊙ re-accrete most of their baryons and transition to metal-enriched Pop II star formation.« less

  11. REVISITING THE FIRST GALAXIES: THE EFFECTS OF POPULATION III STARS ON THEIR HOST GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Muratov, Alexander L.; Gnedin, Oleg Y.; Zemp, Marcel

    2013-08-01

    We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the adaptive refinement tree code. Our simulations feature a recently developed model for H{sub 2} formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III (Pop III) stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch duringmore » which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies that host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 10{sup 8} years after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with a total mass in excess of 3 Multiplication-Sign 10{sup 6} M{sub Sun} re-accrete most of their baryons and transition to metal-enriched Pop II star formation.« less

  12. Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Vincenzo, Fiorenzo; Kobayashi, Chiaki

    2018-04-01

    We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. We identify 33 galaxies in the simulation, lying within dark matter halos with virial mass in the range 1011 ≤ MDM ≤ 1013 M⊙ and reconstruct how they evolved with redshift. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients which have settled in the galaxy interstellar medium, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where - at any redshift - less massive galaxies have lower average O/H and N/O ratios than the more massive ones. We do not find a strong dependence on the environment. For both local and global relations, the predicted N/O-O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy interstellar medium gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O-O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially-resolved galaxy.

  13. Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Vincenzo, Fiorenzo; Kobayashi, Chiaki

    2018-07-01

    We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual interstellar medium (ISM) regions within single spatially resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. We identify 33 galaxies in the simulation, lying within dark matter haloes with virial mass in the range 1011 ≤ MDM ≤ 1013 M⊙ and reconstruct how they evolved with redshift. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients that have settled in the galaxy ISM, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where - at any redshift - less massive galaxies have lower average O/H and N/O ratios than the more massive ones. We do not find a strong dependence on the environment. For both local and global relations, the predicted N/O-O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy ISM gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O-O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially resolved galaxy.

  14. The reliability of [C II] as an indicator of the star formation rate

    NASA Astrophysics Data System (ADS)

    De Looze, Ilse; Baes, Maarten; Bendo, George J.; Cortese, Luca; Fritz, Jacopo

    2011-10-01

    The [C II] 157.74 μm line is an important coolant for the neutral interstellar gas. Since [C II] is the brightest spectral line for most galaxies, it is a potentially powerful tracer of star formation activity. In this paper, we present a calibration of the star formation rate (SFR) as a function of the [C II] luminosity for a sample of 24 star-forming galaxies in the nearby Universe. This sample includes objects classified as H II regions or low-ionization nuclear emission-line regions, but omits all Seyfert galaxies with a significant contribution from the active galactic nucleus to the mid-infrared photometry. In order to calibrate the SFR against the line luminosity, we rely on both Galaxy Evolution Explorer far-ultraviolet data, which is an ideal tracer of the unobscured star formation, and MIPS 24 μm, to probe the dust-enshrouded fraction of star formation. In the case of normal star-forming galaxies, the [C II] luminosity correlates well with the SFR. However, the extension of this relation to more quiescent (Hα EW ≤ 10 Å) or ultraluminous galaxies should be handled with caution, since these objects show a non-linearity in the ?-to-LFIR ratio as a function of LFIR (and thus, their star formation activity). We provide two possible explanations for the origin of the tight correlation between the [C II] emission and the star formation activity on a global galaxy-scale. A first interpretation could be that the [C II] emission from photodissociation regions (PDRs) arises from the immediate surroundings of star-forming regions. Since PDRs are neutral regions of warm dense gas at the boundaries between H II regions and molecular clouds and they provide the bulk of [C II] emission in most galaxies, we believe that a more or less constant contribution from these outer layers of photon-dominated molecular clumps to the [C II] emission provides a straightforward explanation for this close link between the [C II] luminosity and SFR. Alternatively, we consider the

  15. Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: physical properties and implications for studies at z > 7

    NASA Astrophysics Data System (ADS)

    Stark, Daniel P.; Richard, Johan; Siana, Brian; Charlot, Stéphane; Freeman, William R.; Gutkin, Julia; Wofford, Aida; Robertson, Brant; Amanullah, Rahman; Watson, Darach; Milvang-Jensen, Bo

    2014-12-01

    We present deep spectroscopy of 17 very low mass (M⋆ ≃ 2.0 × 106-1.4 × 109 M⊙) and low luminosity (MUV ≃ -13.7 to -19.9) gravitationally lensed galaxies in the redshift range z ≃ 1.5-3.0. Deep rest-frame ultraviolet spectra reveal large equivalent width emission from numerous emission lines (N IV], O III], C IV, Si III], C III]) which are rarely seen in individual spectra of more massive star-forming galaxies. C III] is detected in 16 of 17 low-mass star-forming systems with rest-frame equivalent widths as large as 13.5 Å. Nebular C IV emission is present in the most extreme C III] emitters, requiring an ionizing source capable of producing a substantial component of photons with energies in excess of 47.9 eV. Photoionization models support a picture whereby the large equivalent widths are driven by the increased electron temperature and enhanced ionizing output arising from metal-poor gas and stars (0.04-0.13 Z⊙), young stellar populations (6-50 Myr), and large ionization parameters (log U = -2.16 to -1.84). The young ages implied by the emission lines and continuum spectral energy distributions (SEDs) indicate that the extreme line emitters in our sample are in the midst of a significant upturn in their star formation activity. The low stellar masses, blue UV colours, and large specific star formation rates of our sample are similar to those of typical z ≳ 6 galaxies. Given the strong attenuation of Lyα in z ≳ 6 galaxies, we suggest that C III] is likely to provide our best probe of early star-forming galaxies with ground-based spectrographs and one off the most efficient means of confirming z ≳ 10 galaxies with the James Webb Space Telescope.

  16. The Galaxy Evolution Probe

    NASA Astrophysics Data System (ADS)

    Glenn, Jason; Galaxy Evolution Probe Team

    2018-01-01

    The Galaxy Evolution Probe (GEP) is a concept for a far-infrared observatory to survey large regions of sky for star-forming galaxies from z = 0 to beyond z = 3. Our knowledge of galaxy formation is incomplete and requires uniform surveys over a large range of redshifts and environments to accurately describe mass assembly, star formation, supermassive black hole growth, interactions between these processes, and what led to their decline from z ~ 2 to the present day. Infrared observations are sensitive to dusty, star-forming galaxies, which have bright polycyclic aromatic hydrocarbon (PAH) emission features and warm dust continuum in the rest-frame mid infrared and cooler thermal dust emission in the far infrared. Unlike previous far-infrared continuum surveys, the GEP will measure photometric redshifts commensurate with galaxy detections from PAH emission and Si absorption features, without the need for obtaining spectroscopic redshifts of faint counterparts at other wavelengths.The GEP design includes a 2 m diameter telescope actively cooled to 4 K and two instruments: (1) An imager covering 10 to 300 um with 25 spectral resolution R ~ 8 bands (with lower R at the longest wavelengths) to detect star-forming galaxies and measure their redshifts photometrically. (2) A 23 – 190 um, R ~ 250 dispersive spectrometer for redshift confirmation and identification of obscured AGN using atomic fine-structure lines. Lines including [Ne V], [O IV], [O III], [O I], and [C II] will probe gas physical conditions, radiation field hardness, and metallicity. Notionally, the GEP will have a two-year mission: galaxy surveys with photometric redshifts in the first year and a second year devoted to follow-up spectroscopy. A comprehensive picture of star formation in galaxies over the last 10 billion years will be assembled from cosmologically relevant volumes, spanning environments from field galaxies and groups, to protoclusters, to dense galaxy clusters.Commissioned by NASA, the

  17. Following the Cosmic Evolution of Pristine Gas. II. The Search for Pop III–bright Galaxies

    NASA Astrophysics Data System (ADS)

    Sarmento, Richard; Scannapieco, Evan; Cohen, Seth

    2018-02-01

    Direct observational searches for Population III (Pop III) stars at high redshift are faced with the question of how to select the most promising targets for spectroscopic follow-up. To help answer this, we use a large-scale cosmological simulation, augmented with a new subgrid model that tracks the fraction of pristine gas, to follow the evolution of high-redshift galaxies and the Pop III stars they contain. We generate rest-frame ultraviolet (UV) luminosity functions for our galaxies and find that they are consistent with current z≥slant 7 observations. Throughout the redshift range 7≤slant z≤slant 15, we identify “Pop III–bright” galaxies as those with at least 75% of their flux coming from Pop III stars. While less than 1% of galaxies brighter than {m}UV,{AB}}=31.4 mag are Pop III–bright in the range 7≤slant z≤slant 8, roughly 17% of such galaxies are Pop III–bright at z = 9, immediately before reionization occurs in our simulation. Moving to z = 10, {m}UV,{AB}}=31.4 mag corresponds to larger, more luminous galaxies, and the Pop III–bright fraction falls off to 5%. Finally, at the highest redshifts, a large fraction (29% at z = 14 and 41% at z = 15) of all galaxies are Pop III–bright regardless of magnitude. While {m}UV,{AB}}=31.4 mag galaxies are extremely rare during this epoch, we find that 13% of galaxies at z = 14 are Pop III–bright with {m}UV,{AB}}≤slant 33 mag, a intrinsic magnitude within reach of the James Webb Space Telescope using lensing. Thus, we predict that the best redshift to search for luminous Pop III–bright galaxies is just before reionization, while lensing surveys for fainter galaxies should push to the highest redshifts possible.

  18. The origin of chromitic chondrules and the volatility of Cr under a range of nebular conditions

    NASA Technical Reports Server (NTRS)

    Krot, Alexander; Ivanova, Marina A.; Wasson, John T.

    1993-01-01

    We characterize ten chromatic chondrules, two spinelian chondrules andd one spinel-bearing chondrule and summarize data for 120 chromitic inclusions discovered in an extensive survey of ordinary chondrites. Compositional and petrographic evidence suggests that chromitic chondrules and inclusions are closely related. The Cr/(Cr + Al) ratios in the spinal of these objects range from 0.5 to 0.9 and bulk Al2O3 contents are uniformly high (greater than 10 wt%, except for one with 8 wt%). No other elements having comparable solar abundances are so stongly enriched, and alkali feldspar and merrillite are more common than in normal chondrules. The Cr/Mg ratios in chromitic chondrules are 180-750 times the ratios in the bulk chondrite. With the possible exception of magnetic clumping of chromite in the presolar cloud, mechanical processes cannot account for this enrichment. Examination of nebular equilibrium processes shows that 50%-condensation temperatures of Cr at pH2/pH2O of 1500 are several tens of degrees below those of Mg as Mg2SiO4; the condensation of Cr is primarily as MgCr2O4 dissolved in MgAl2O4 at nebular pressures of 10(exp -4) atm or below. At pH2 = 10(exp -3) atm condesation as Cr in Fe-Ni is favored. Making the nebula much more oxidizing reduces the difference in condensation temperatures but Mg remains more refractory. We conclude that nebular equilibrium processes are not responsible for the enhanced Cr/Mg ratios. We propose that both Cr and Al became enriched in residues formed by incomplete evaporation of presolar lumps. We suggest that spinals remained as solid phases when the bulk of the silicates were incorporated into the evaporating melt; vaporization of Al and Cr were inhibited by the slow kinetics of diffusion. Subsequent melting and crystallization of these residues fractionated Cr from Al. The resulting materials constituted major components in the precursors of chromitic chondrules. Our model implies that chromitic chondrules and inclusions

  19. Diffuse Optical Light in Galaxy Clusters. II. Correlations with Cluster Properties

    NASA Astrophysics Data System (ADS)

    Krick, J. E.; Bernstein, R. A.

    2007-08-01

    We have measured the flux, profile, color, and substructure in the diffuse intracluster light (ICL) in a sample of 10 galaxy clusters with a range of mass, morphology, redshift, and density. Deep, wide-field observations for this project were made in two bands at the 1 m Swope and 2.5 m du Pont telescopes at Las Campanas Observatory. Careful attention in reduction and analysis was paid to the illumination correction, background subtraction, point-spread function determination, and galaxy subtraction. ICL flux is detected in both bands in all 10 clusters ranging from 7.6×1010 to 7.0×1011 h-170 Lsolar in r and 1.4×1010 to 1.2×1011 h-170 Lsolar in the B band. These fluxes account for 6%-22% of the total cluster light within one-quarter of the virial radius in r and 4%-21% in the B band. Average ICL B-r colors range from 1.5 to 2.8 mag when k- and evolution corrected to the present epoch. In several clusters we also detect ICL in group environments near the cluster center and up to 1 h-170 Mpc distant from the cluster center. Our sample, having been selected from the Abell sample, is incomplete in that it does not include high-redshift clusters with low density, low flux, or low mass, and it does not include low-redshift clusters with high flux, high mass, or high density. This bias makes it difficult to interpret correlations between ICL flux and cluster properties. Despite this selection bias, we do find that the presence of a cD galaxy corresponds to both centrally concentrated galaxy profiles and centrally concentrated ICL profiles. This is consistent with ICL either forming from galaxy interactions at the center or forming at earlier times in groups and later combining in the center.

  20. Hubble Spotlight on Irregular Galaxy

    NASA Image and Video Library

    2017-12-08

    This delicate blue group of stars — actually an irregular galaxy named IC 3583 — sits some 30 million light-years away in the constellation of Virgo (The Virgin). It may seem to have no discernable structure, but IC 3583 has been found to have a bar of stars running through its center. These structures are common throughout the Universe, and are found within the majority of spiral, many irregular, and some lenticular galaxies. Two of our closest cosmic neighbors, the Large and Small Magellanic Clouds, are barred, indicating that they may have once been barred spiral galaxies that were disrupted or torn apart by the gravitational pull of the Milky Way. Researchers at the University of Leicester, England note there are two types of irregular galaxy. Type I's are usually single galaxies of peculiar appearance. They contain a large fraction of young stars, and show the luminous nebulae that are also visible in spiral galaxies. Type II irregulars include the group known as interacting or disrupting galaxies, in which the strange appearance is due to two or more galaxies colliding, merging or otherwise interacting gravitationally. Something similar might be happening with IC 3583. This small galaxy is thought to be gravitationally interacting with one of its neighbors, the spiral Messier 90. Together, the duo form a pairing known as Arp 76. It’s still unclear whether these flirtations are the cause of IC 3583’s irregular appearance — but whatever the cause, the galaxy makes for a strikingly delicate sight in this NASA/ESA Hubble Space Telescope image, glimmering in the blackness of space. Image Credit: ESA/Hubble & NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on

  1. Weighing galaxy clusters with gas. II. On the origin of hydrostatic mass bias in ΛCDM galaxy clusters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nelson, Kaylea; Nagai, Daisuke; Yu, Liang

    2014-02-20

    The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to themore » bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (≲ 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.« less

  2. SDSS IV MaNGA: Deep observations of extra-planar, diffuse ionized gas around late-type galaxies from stacked IFU spectra

    NASA Astrophysics Data System (ADS)

    Jones, A.; Kauffmann, G.; D'Souza, R.; Bizyaev, D.; Law, D.; Haffner, L.; Bahé, Y.; Andrews, B.; Bershady, M.; Brownstein, J.; Bundy, K.; Cherinka, B.; Diamond-Stanic, A.; Drory, N.; Riffel, R. A.; Sánchez, S. F.; Thomas, D.; Wake, D.; Yan, R.; Zhang, K.

    2017-03-01

    We have conducted a study of extra-planar diffuse ionized gas using the first year data from the MaNGA IFU survey. We have stacked spectra from 49 edge-on, late-type galaxies as a function of distance from the midplane of the galaxy. With this technique we can detect the bright emission lines Hα, Hβ, [O II]λλ3726, 3729, [O III]λ5007, [N II]λλ6549, 6584, and [S II]λλ6717, 6731 out to about 4 kpc above the midplane. With 16 galaxies we can extend this analysis out to about 9 kpc, I.e. a distance of 2Re, vertically from the midplane. In the halo, the surface brightnesses of the [O II] and Hα emission lines are comparable, unlike in the disk where Hα dominates. When we split the sample by specific star-formation rate, concentration index, and stellar mass, each subsample's emission line surface brightness profiles and ratios differ, indicating that extra-planar gas properties can vary. The emission line surface brightnesses of the gas around high specific star-formation rate galaxies are higher at all distances, and the line ratios are closer to ratios characteristic of H II regions compared with low specific star-formation rate galaxies. The less concentrated and lower stellar mass samples exhibit line ratios that are more like H II regions at larger distances than their more concentrated and higher stellar mass counterparts. The largest difference between different subsamples occurs when the galaxies are split by stellar mass. We additionally infer that gas far from the midplane in more massive galaxies has the highest temperatures and steepest radial temperature gradients based on their [N II]/Hα and [O II]/Hα ratios between the disk and the halo. SDSS IV.

  3. LeMMINGs - I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

    NASA Astrophysics Data System (ADS)

    Baldi, R. D.; Williams, D. R. A.; McHardy, I. M.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Muxlow, T. W. B.; Aalto, S.; Alberdi, A.; Bendo, G. J.; Corbel, S.; Evans, R.; Fenech, D. M.; Green, D. A.; Klöckner, H.-R.; Körding, E.; Kharb, P.; Maccarone, T. J.; Martí-Vidal, I.; Mundell, C. G.; Panessa, F.; Peck, A. B.; Pérez-Torres, M. A.; Saikia, D. J.; Saikia, P.; Shankar, F.; Spencer, R. E.; Stevens, I. R.; Uttley, P.; Westcott, J.

    2018-05-01

    We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H II galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H II galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s-1: LINERs and H II galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ˜107 M⊙, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H II galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H II galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

  4. Hot Dust in Ultraluminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Shchekinov, Yu. A.; Vasiliev, E. O.

    2017-12-01

    Ultraluminous infrared galaxies with total luminosities an order of magnitude greater than that of our galaxy over wavelengths of λλ = 10-800 μm are characterized by a high mass concentration of dust. Because of this, the optical thickness of the interstellar gas is extremely high, especially in the central regions of the galaxies, ranging from 1 at millimeter wavelengths to 104 in the visible. The average temperature of the dust in them is about Td=30 K, but the variations from one galaxy to another are large, with Td=20-70 K. The main source of dust in these galaxies seems to be type II supernova bursts and the main heating source is stars. In addition, given that shock waves from supernovae are an effective mechanism for destruction of interstellar dust in our galaxy and the high optical thickness of the gas with respect to the heating radiation from the stars, this conclusion merits detailed analysis. This paper provides estimates of the dust mass balance and details of its heating in these galaxies based on the example of the ultraluminous galaxy closest to us, Arp 220. It is shown that when supernovae are dominant in the production and destruction of dust in the interstellar gas, the resultant dust mass fraction is close to the observed value for Arp 220. It is also found that the observed stellar population of this galaxy can support a high ( Td ≃ 67 K ) temperature if the dust in its central region is concentrated in small, dense (n 105 cm-3) clouds with radii of 0.003 ≲ pc. Mechanisms capable of maintaining an interstellar gas structure in this state are discussed.

  5. Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA. II. Star formation properties of galaxies in the Virgo cluster and surroundings

    NASA Astrophysics Data System (ADS)

    Gavazzi, G.; Fumagalli, M.; Fossati, M.; Galardo, V.; Grossetti, F.; Boselli, A.; Giovanelli, R.; Haynes, M. P.

    2013-05-01

    Context. We present the analysis of Hα3, an Hα narrow-band imaging follow-up survey of 409 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster, in the region 11h < RA < 16h ; 4o < Dec < 16°; 350 < cz < 2000 km s-1. Aims: Taking advantage of Hα3, which provides the complete census of the recent massive star formation rate (SFR) in HI-rich galaxies in the local Universe and of ancillary optical data from SDSS we explore the relations between the stellar mass, the HI mass, and the current, massive SFR of nearby galaxies in the Virgo cluster. We compare these with those of isolated galaxies in the Local Supercluster, and we investigate the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. Methods: By using the Hα hydrogen recombination line as a tracer of recent star formation, we investigated the relationships between atomic neutral gas and newly formed stars in different environments (cluster and field), for many morphological types (spirals and dwarfs), and over a wide range of stellar masses (107.5 to 1011.5 M⊙). To quantify the degree of environmental perturbation, we adopted an updated calibration of the HI deficiency parameter which we used to divide the sample into three classes: unperturbed galaxies (DefHI ≤ 0.3), perturbed galaxies (0.3 < DefHI < 0.9), and highly perturbed galaxies (DefHI ≥ 0.9). Results: Studying the mean properties of late-type galaxies in the Local Supercluster, we find that galaxies in increasing dense local galaxy conditions (or decreasing projected angular separation from M 87) show a significant decrease in the HI content and in the mean specific SFR, along with a progressive reddening of their stellar populations. The gradual quenching of the star formation occurs outside-in, consistently with the predictions of the ram pressure model. Once considered as a whole, the Virgo cluster is

  6. LOCAL TADPOLE GALAXIES: DYNAMICS AND METALLICITY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sanchez Almeida, J.; Munoz-Tunon, C.; Mendez-Abreu, J.

    2013-04-10

    Tadpole galaxies, with a bright peripheral clump on a faint tail, are morphological types unusual in the nearby universe but very common early on. Low mass local tadpoles were identified and studied photometrically in a previous work, which we complete here analyzing their chemical and dynamical properties. We measure H{alpha} velocity curves of seven local tadpoles, representing 50% of the initial sample. Five of them show evidence for rotation ({approx}70%), and a sixth target hints at it. Often the center of rotation is spatially offset with respect to the tadpole head (three out of five cases). The size and velocitymore » dispersion of the heads are typical of giant H II regions, and three of them yield dynamical masses in fair agreement with their stellar masses as inferred from photometry. In four cases the velocity dispersion at the head is reduced with respect to its immediate surroundings. The oxygen metallicity estimated from [N II] {lambda}6583/H{alpha} often shows significant spatial variations across the galaxies ({approx}0.5 dex), being smallest at the head and larger elsewhere. The resulting chemical abundance gradients are opposite to the ones observed in local spirals, but agrees with disk galaxies at high redshift. We interpret the metallicity variation as a sign of external gas accretion (cold-flows) onto the head of the tadpole. The galaxies are low-metallicity outliers of the mass-metallicity relationship. In particular, two of the tadpole heads are extremely metal poor, with a metallicity smaller than a tenth of the solar value. These two targets are also very young (ages smaller than 5 Myr). All these results combined are consistent with the local tadpole galaxies being disks in early stages of assembling, with their star formation sustained by accretion of external metal-poor gas.« less

  7. The γ-ray emission region in the Fanaroff-Riley II radio galaxy 3C 111

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grandi, P.; Torresi, E.; Stanghellini, C.

    The broad-line radio galaxy 3C 111, characterized by a Fanaroff-Riley II (FRII) radio morphology, is one of the sources of the misaligned active galactic nucleus sample, consisting of radio galaxies and steep spectrum radio quasars, recently detected by the Fermi Large Area Telescope (LAT). In this analysis of the 24 month γ-ray light curve shows that 3C 111 was only occasionally detected at high energies. It was bright at the end of 2008 and faint, below the Fermi-LAT sensitivity threshold, for the rest of the time. A multifrequency campaign of 3C 111, ongoing in the same period, revealed an increasemore » of the millimeter, optical, and X-ray fluxes in 2008 September-November, interpreted by Chatterjee et al. as due to the passage of a superluminal knot through the jet core. Furthermore, the temporal coincidence of the millimeter-optical-X-ray outburst with the GeV activity suggests a cospatiality of the events, allowing, for the first time, the localization of the γ-ray dissipative zone in an FRII jet. Here, we argue that the GeV photons of 3C 111 are produced in a compact region confined within 0.1 pc and at a distance of about 0.3 pc from the black hole.« less

  8. The γ-ray emission region in the Fanaroff-Riley II radio galaxy 3C 111

    DOE PAGES

    Grandi, P.; Torresi, E.; Stanghellini, C.

    2012-04-30

    The broad-line radio galaxy 3C 111, characterized by a Fanaroff-Riley II (FRII) radio morphology, is one of the sources of the misaligned active galactic nucleus sample, consisting of radio galaxies and steep spectrum radio quasars, recently detected by the Fermi Large Area Telescope (LAT). In this analysis of the 24 month γ-ray light curve shows that 3C 111 was only occasionally detected at high energies. It was bright at the end of 2008 and faint, below the Fermi-LAT sensitivity threshold, for the rest of the time. A multifrequency campaign of 3C 111, ongoing in the same period, revealed an increasemore » of the millimeter, optical, and X-ray fluxes in 2008 September-November, interpreted by Chatterjee et al. as due to the passage of a superluminal knot through the jet core. Furthermore, the temporal coincidence of the millimeter-optical-X-ray outburst with the GeV activity suggests a cospatiality of the events, allowing, for the first time, the localization of the γ-ray dissipative zone in an FRII jet. Here, we argue that the GeV photons of 3C 111 are produced in a compact region confined within 0.1 pc and at a distance of about 0.3 pc from the black hole.« less

  9. Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area. V - Luminosity functions of Virgo Cluster galaxies

    NASA Technical Reports Server (NTRS)

    Binggeli, B.; Tammann, G. A.; Sandage, A.

    1985-01-01

    The present catalog of 2096 galaxies within an area of about 140 sq deg approximately centered on the Virgo cluster should be an essentially complete listing of all certain and possible cluster members, independent of morphological type. Cluster membership is essentially decided by galaxy morphology; for giants and the rare class of high surface brightness dwarfs, membership rests on velocity data. While 1277 of the catalog entries are considered members of the Virgo cluster, 574 are possible members and 245 appear to be background Zwicky galaxies. Major-to-minor axis ratios are given for all galaxies brighter than B(T) = 18, as well as for many fainter ones.

  10. Chemical enrichment in isolated barred spiral galaxies

    NASA Astrophysics Data System (ADS)

    Martel, Hugo; Carles, Christian; Robichaud, Fidèle; Ellison, Sara L.; Williamson, David J.

    2018-07-01

    To investigate the role of bars in the chemical evolution of isolated disc galaxies, we performed a series of 39 gas dynamical simulations of isolated barred and unbarred galaxies with various masses, initial gas fractions, and active galactic nucleus (AGN) feedback models. The presence of a bar drives a substantial amount of gas towards the central region of the galaxy. In the most massive galaxies, this results in a violent starburst, followed by a drop in star formation resulting from gas exhaustion. The time delay between Type Ia and Type II supernovae explosions means that barred galaxies experience a rapid increase in [O/H] in the central region, and a much more gradual increase in [Fe/H]. In unbarred galaxies, star formation proceeds at a slow and steady rate, and oxygen and iron are produced at steady rates which are similar except for a time offset. Comparing the abundance ratios in barred and unbarred galaxies with the same central stellar mass M*, we find in barred galaxies an enhancement of 0.07 dex in [O/H], 0.05 dex in [Fe/H], and 0.05 dex in [O/Fe]. The [O/H] enhancement is in excellent agreement with observations from the SDSS. The initial gas fraction has very little effect on the abundance ratios in barred and unbarred galaxies, unless the galaxies experience a starburst. We considered AGN-host galaxies located near the bottom of the AGN regime, M* ≳ 3 × 1010M⊙, where AGN feedback dominates over supernovae feedback. We found that the impact of AGN feedback on the central abundances is marginal.

  11. The final data release of ALLSMOG: a survey of CO in typical local low-M∗ star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Cicone, C.; Bothwell, M.; Wagg, J.; Møller, P.; De Breuck, C.; Zhang, Z.; Martín, S.; Maiolino, R.; Severgnini, P.; Aravena, M.; Belfiore, F.; Espada, D.; Flütsch, A.; Impellizzeri, V.; Peng, Y.; Raj, M. A.; Ramírez-Olivencia, N.; Riechers, D.; Schawinski, K.

    2017-08-01

    We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2-1) emission line observations of 88 nearby, low-mass (108.5galaxies carried out with the 230 GHz APEX-1 receiver on the APEX telescope. The main goal of ALLSMOG is to probe the molecular gas content of more typical and lower stellar mass galaxies than have been studied by previous CO surveys. We also present IRAM 30 m observations of the CO(1-0) and CO(2-1) emission lines in nine galaxies aimed at increasing the M∗< 109M⊙ sample size. In this paper we describe the observations, data reduction and analysis methods and we present the final CO spectra together with archival Hi 21 cm line observations for the entire sample of 97 galaxies. At the sensitivity limit of ALLSMOG, we register a total CO detection rate of 47%. Galaxies with higher M∗, SFR, nebular extinction (AV), gas-phase metallicity (O/H), and Hi gas mass have systematically higher CO detection rates. In particular, the parameter according to which CO detections and non-detections show the strongest statistical differences is the gas-phase metallicity, for any of the five metallicity calibrations examined in this work. We investigate scaling relations between the CO(1-0) line luminosity (L'CO(1-0)) and galaxy-averaged properties using ALLSMOG and a sub-sample of COLD GASS for a total of 185 sources that probe the local main sequence (MS) of star-forming galaxies and its ± 0.3 dex intrinsic scatter from M∗ = 108.5M⊙ to M∗ = 1011M⊙. L'CO(1-0) is most strongly correlated with the SFR, but the correlation with M∗ is closer to linear and almost comparably tight. The relation between L'CO(1-0) and metallicity is the steepest one, although deeper CO observations of galaxies with AV< 0.5 mag may reveal an as much steep correlation with AV. Our results suggest that star-forming galaxies across more than two orders of magnitude in M∗ obey similar

  12. Deep spectroscopy of nearby galaxy clusters - IV. The quench of the star formation in galaxies in the infall region of Abell 85

    NASA Astrophysics Data System (ADS)

    Aguerri, J. A. L.; Agulli, I.; Méndez-Abreu, J.

    2018-06-01

    Our aim is to understand the role of the environment in the quenching of star formation of galaxies located in the infall cluster region of Abell 85 (A85). This is achieved by studying the post-starburst galaxy population as tracer of recent quenching. By measuring the equivalent width (EW) of the [O II] and Hδ spectral lines, we classify the galaxies into three groups: passive (PAS), emission line (EL), and post-starburst (PSB) galaxies. The PSB galaxy population represents ˜ 4.5 per cent of the full sample. Dwarf galaxies (Mr > -18.0) account for ˜ 70 - 80 per cent of PSBs, which indicates that most of the galaxies undergoing recent quenching are low-mass objects. Independently of the environment, PSB galaxies are disc-like objects with g - r colour between the blue ELs and the red PAS ones. The PSB and EL galaxies in low-density environments show similar luminosities and local galaxy densities. The dynamics and local galaxy density of the PSB population in high-density environments are shared with PAS galaxies. However, PSB galaxies inside A85 are at shorter clustercentric radius than PAS and EL ones. The value of the EW(Hδ) is larger for those PSBs closer to the cluster centre. We propose two different physical mechanisms producing PSB galaxies depending on the environment. In low-density environments, gas-rich minor mergers or accretions could produce the PSB galaxies. For high-density environments like A85, PSBs would be produced by the removal of the gas reservoirs of EL galaxies by ram-pressure stripping when they pass near the cluster centre.

  13. Examining Gaseous Behavior of Galaxies and their Environments

    NASA Astrophysics Data System (ADS)

    Ivory, KeShawn; Barger, Kathleen

    2017-01-01

    The development of galaxies hinges upon the behavior of the gas within and around them, as this is paramount to understanding the regulation of star formation. To investigate these processes, we analyzed data from the MaNGA survey for two galaxies with nearby background quasars for which Hubble Space Telescope data exists. We plotted and analyzed spectra for various elemental transitions, especially [N II] , [O III], and H-alpha, to gain information about gas properties such as temperature, ionization fraction, and star formation. We also plotted velocity fields based upon the gas motions as determined through Doppler shift. One of the galaxies displayed signs of heavy star formation and the other displayed signs of Active Galactic Nucleus activity. The stellar and gaseous velocity fields of the AGN galaxy were very disparate which suggests some sort of interaction with another galaxy in the galaxy’s past. The properties of the gas in these galaxies could potentially teach us more about the evolutionary path of the Milky Way, which forms stars itself while interacting heavily with other galaxies. This work base on data from the forth-generation Sloan Digital Sky Survey (SDSS-IV)/Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), and is part of the Project No.0034 in SDSS-IV.

  14. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jaskot, A. E.; Ravindranath, S.

    The increasing neutrality of the intergalactic medium at z  > 6 suppresses Ly α emission, and spectroscopic confirmation of galaxy redshifts requires the detection of alternative ultraviolet lines. The strong [C iii]  λ 1907+C iii]  λ 1909 doublet frequently observed in low-metallicity, actively star-forming galaxies is a promising emission feature. We present CLOUDY photoionization model predictions for C iii] equivalent widths (EWs) and line ratios as a function of starburst age, metallicity, and ionization parameter. Our models include a range of C/O abundances, dust content, and gas density. We also examine the effects of varying the nebular geometry and optical depth. Onlymore » the stellar models that incorporate binary interaction effects reproduce the highest observed C iii] EWs. The spectral energy distributions from the binary stellar population models also generate observable C iii] over a longer timescale relative to single-star models. We show that diagnostics using C iii] and nebular He ii  λ 1640 can separate star-forming regions from shock-ionized gas. We also find that density-bounded systems should exhibit weaker C iii] EWs at a given ionization parameter, and C iii] EWs could, therefore, select candidate Lyman continuum-leaking systems. In almost all models, C iii] is the next strongest line at <2700 Å after Ly α , and C iii] reaches detectable levels for a wide range of conditions at low metallicity. C iii] may therefore serve as an important diagnostic for characterizing galaxies at z  > 6.« less

  15. Surface Photometric Properties of HII Galaxies

    NASA Astrophysics Data System (ADS)

    Vajgel, B.; Telles, E.

    2009-05-01

    HII galaxies are dwarf galaxies undergoing violent star formation. They were firstly selected by objective-prism spectroscopy and were object of extensive studies to characterize their physical conditions of the interstellar medium. Their SFR together with their low Z raised the question whether some of them can be truly ``young'' galaxies. To infer the SFH, one needs information in a large spectral range. We obtained images in the optical region of the spectrum with the 0.6 m B&C and the 1.6 m telescopes at the Laboratório Nacional de Astrofísica, for a sample of 50 objects in B, V, R and I, which combined with recent evolutionary models, enable us to deduce the stellar population content and its spatial distribution. These seem to be the nearest youngest galaxies that can be studied in detail, and their structural properties offer important indications about the evolutionary relation and the origin of dwarf galaxies in the universe. With this sample we built a morphological catalogue with broad-band photometry, including the structural analysis through the brightness profiles. The initial analysis suggests that the galaxies can be segregated in two broad classes, in agreement with what had already been proposed in the literature; Type I have irregular envelopes with signs of perturbation and turn out to the more luminous sub-sample; while Type II have regular external isophotes and are less luminous. The brightness profiles are well represented by exponential fits, as in irregular and elliptical dwarf galaxies. However, HII galaxies are more compact in comparison with their more diffuse counterparts. We study the behavior of the HII galaxies in the metallicity-luminosity plane. This relation, interpreted as a relation between the mass and the metallicity of dwarf galaxies of low surface brightness (dE and dIrr), has direct implications for their formation and evolution, and over the possible evolutionary links between HII galaxies and other types of dwarf

  16. CONSTRAINING VERY HIGH MASS POPULATION III STARS THROUGH He II EMISSION IN GALAXY BDF-521 AT z = 7.01

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cai, Zheng; Fan, Xiaohui; Davé, Romeel

    2015-01-30

    Numerous theoretical models have long proposed that a strong He II λ1640 emission line is the most prominent and unique feature of massive Population III (Pop III) stars in high-redshift galaxies. The He II λ1640 line strength can constrain the mass and initial mass function (IMF) of Pop III stars. We use F132N narrowband filter on the Hubble Space Telescope's (HST) Wide Field Camera 3 to look for strong He II λ1640 emission in the galaxy BDF-521 at z = 7.01, one of the most distant spectroscopically confirmed galaxies to date. Using deep F132N narrowband imaging, together with our broadband imaging with F125Wmore » and F160W filters, we do not detect He II emission from this galaxy, but place a 2σ upper limit on the flux of 5.3×10{sup −19} erg s{sup −1} cm{sup −2}. This measurement corresponds to a 2σ upper limit on the Pop III star formation rate (SFR{sub PopIII}) of ∼0.2 M {sub ☉} yr{sup –1}, assuming a Salpeter IMF with 50 ≲ M/M {sub ☉} ≲ 1000. From the high signal-to-noise broadband measurements in F125W and F160W, we fit the UV continuum for BDF-521. The spectral flux density is ∼3.6×10{sup −11}×λ{sup −2.32} erg s{sup −1} cm{sup −2} Å{sup –1}, which corresponds to an overall unobscured SFR of ∼5 M {sub ☉} yr{sup –1}. Our upper limit on SFR{sub PopIII} suggests that massive Pop III stars represent ≲ 4% of the total star formation. Further, the HST high-resolution imaging suggests that BDF-521 is an extremely compact galaxy, with a half-light radius of 0.6 kpc.« less

  17. A whiff of nebular gas in Titan's atmosphere - Potential implications for the conditions and timing of Titan's formation

    NASA Astrophysics Data System (ADS)

    Glein, Christopher R.

    2017-09-01

    In situ data from the GCMS instrument on the Huygens probe indicate that Titan's atmosphere contains small amounts of the primordial noble gases 36Ar and 22Ne (tentative detection), but it is unknown how they were obtained by the satellite. Based on the apparent similarity in the 22Ne/36Ar (atom) ratio between Titan's atmosphere and the solar composition, a previously neglected hypothesis for the origin of primordial noble gases in Titan's atmosphere is suggested - these species may have been acquired near the end of Titan's formation, when the moon could have gravitationally captured some nebular gas that would have been present in its formation environment (the Saturnian subnebula). These noble gases may be remnants of a primary atmosphere. This could be considered the simplest hypothesis to explain the 22Ne/36Ar ratio observed at Titan. However, the 22Ne/36Ar ratio may not be exactly solar if these species can be fractionated by external photoevaporation in the solar nebula, atmospheric escape from Titan, or sequestration on the surface of Titan. While the GCMS data are consistent with a 22Ne/36Ar ratio of 0.05 to 2.5 times solar (1σ range), simple estimates that attempt to account for some of the effects of these evolutionary processes suggest a sub-solar ratio, which may be depleted by approximately one order of magnitude. Models based on capture of nebular gas can explain why the GCMS did not detect any other primordial noble gas isotopes, as their predicted abundances are below the detection limits (especially for 84Kr and 132Xe). It is also predicted that atmospheric Xe on Titan should be dominated by radiogenic 129Xe if the source of primordial Xe is nebular gas. Of order 10-2-10-1 bar of primordial H2 may have been captured along with the noble gases from a gas-starved disk, but this H2 would have quickly escaped from the initial atmosphere. To have the opportunity to capture nebular gas, Titan should have formed within ∼10 Myr of the formation of the

  18. Galaxy and mass assembly (GAMA): dust obscuration in galaxies and their recent star formation histories

    NASA Astrophysics Data System (ADS)

    Wijesinghe, D. B.; Hopkins, A. M.; Sharp, R.; Gunawardhana, M.; Brough, S.; Sadler, E. M.; Driver, S.; Baldry, I.; Bamford, S.; Liske, J.; Loveday, J.; Norberg, P.; Peacock, J.; Popescu, C. C.; Tuffs, R. J.; Bland-Hawthorn, J.; Cameron, E.; Croom, S.; Frenk, C.; Hill, D.; Jones, D. H.; van Kampen, E.; Kelvin, L.; Kuijken, K.; Madore, B.; Nichol, B.; Parkinson, H.; Pimbblet, K. A.; Prescott, M.; Robotham, A. S. G.; Seibert, M.; Simmat, E.; Sutherland, W.; Taylor, E.; Thomas, D.

    2011-02-01

    We present self-consistent star formation rates derived through pan-spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Hα, [O II] and UV luminosities. These corrections are applied to a sample of 31 508 galaxies from the GAMA survey at z < 0.35. We consider several different obscuration curves, including those of Milky Way, Calzetti and Fischera & Dopita curves and their effects on the observed luminosities. At the core of this technique is the observed Balmer decrement, and we provide a prescription to apply optimal obscuration corrections using the Balmer decrement. We carry out an analysis of the star formation history (SFH) using stellar population synthesis tools to investigate the evolutionary history of our sample of galaxies as well as to understand the effects of variation in the initial mass function (IMF) and the effects this has on the evolutionary history of galaxies. We find that the Fischera & Dopita obscuration curve with an Rv value of 4.5 gives the best agreement between the different SFR indicators. The 2200 Å feature needed to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission. We also find that the UV dust obscuration is strongly dependent on the SFR.

  19. The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

    NASA Astrophysics Data System (ADS)

    Medling, Anne M.; Cortese, Luca; Croom, Scott M.; Green, Andrew W.; Groves, Brent; Hampton, Elise; Ho, I.-Ting; Davies, Luke J. M.; Kewley, Lisa J.; Moffett, Amanda J.; Schaefer, Adam L.; Taylor, Edward; Zafar, Tayyaba; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V.; Brough, Sarah; Bryant, Julia J.; Catinella, Barbara; Cecil, Gerald; Colless, Matthew; Couch, Warrick J.; Drinkwater, Michael J.; Driver, Simon P.; Federrath, Christoph; Foster, Caroline; Goldstein, Gregory; Goodwin, Michael; Hopkins, Andrew; Lawrence, J. S.; Leslie, Sarah K.; Lewis, Geraint F.; Lorente, Nuria P. F.; Owers, Matt S.; McDermid, Richard; Richards, Samuel N.; Sharp, Robert; Scott, Nicholas; Sweet, Sarah M.; Taranu, Dan S.; Tescari, Edoardo; Tonini, Chiara; van de Sande, Jesse; Walcher, C. Jakob; Wright, Angus

    2018-04-01

    We present the ˜800 star formation rate maps for the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey based on H α emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1. We mask out spaxels contaminated by non-stellar emission using the [O III]/H β, [N II]/H α, [S II]/H α, and [O I]/H α line ratios. Using these maps, we examine the global and resolved star-forming main sequences of SAMI galaxies as a function of morphology, environmental density, and stellar mass. Galaxies further below the star-forming main sequence are more likely to have flatter star formation profiles. Early-type galaxies split into two populations with similar stellar masses and central stellar mass surface densities. The main-sequence population has centrally concentrated star formation similar to late-type galaxies, while galaxies >3σ below the main sequence show significantly reduced star formation most strikingly in the nuclear regions. The split populations support a two-step quenching mechanism, wherein halo mass first cuts off the gas supply and remaining gas continues to form stars until the local stellar mass surface density can stabilize the reduced remaining fuel against further star formation. Across all morphologies, galaxies in denser environments show a decreased specific star formation rate from the outside in, supporting an environmental cause for quenching, such as ram-pressure stripping or galaxy interactions.

  20. Galaxy interactions in the Hickson Compact Group 88

    NASA Astrophysics Data System (ADS)

    Brosch, Noah

    2015-12-01

    I present observations of the Hickson Compact Group 88 (HCG88) obtained during the commissioning of a new 28-inch telescope at the Wise Observatory. This galaxy group was advertized to be non-interacting, or to be in a very early interaction stage, but this is not the case. The observations reported here were done using a `luminance' filter, essentially a very broad R filter, reaching a low surface brightness level of ≈26 mag arcsec-2. Additional observations were obtained in a narrow spectral band approximately centred on the rest-frame H α line from the group. Contrary to previous studies, my observations show that at least two of the major galaxies have had significant interactions in the past, although probably not between themselves. I report the discovery of a faint extended tail emerging from the brightest of the group galaxies, severe isophote twisting and possible outer shells around another galaxy, and map the H II regions in all the galaxies.

  1. A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA

    NASA Astrophysics Data System (ADS)

    Sánchez, S. F.; Rosales-Ortega, F. F.; Iglesias-Páramo, J.; Mollá, M.; Barrera-Ballesteros, J.; Marino, R. A.; Pérez, E.; Sánchez-Blazquez, P.; González Delgado, R.; Cid Fernandes, R.; de Lorenzo-Cáceres, A.; Mendez-Abreu, J.; Galbany, L.; Falcon-Barroso, J.; Miralles-Caballero, D.; Husemann, B.; García-Benito, R.; Mast, D.; Walcher, C. J.; Gil de Paz, A.; García-Lorenzo, B.; Jungwiert, B.; Vílchez, J. M.; Jílková, Lucie; Lyubenova, M.; Cortijo-Ferrero, C.; Díaz, A. I.; Wisotzki, L.; Márquez, I.; Bland-Hawthorn, J.; Ellis, S.; van de Ven, G.; Jahnke, K.; Papaderos, P.; Gomes, J. M.; Mendoza, M. A.; López-Sánchez, Á. R.

    2014-03-01

    We present the largest and most homogeneous catalog of H ii regions and associations compiled so far. The catalog comprises more than 7000 ionized regions, extracted from 306 galaxies observed by the CALIFA survey. We describe the procedures used to detect, select, and analyze the spectroscopic properties of these ionized regions. In the current study we focus on characterizing of the radial gradient of the oxygen abundance in the ionized gas, based on the study of the deprojecteddistribution of H ii regions. We found that all galaxies without clear evidence of an interaction present a common gradient in the oxygen abundance, with a characteristic slope of αO/H = -0.1 dex/re between 0.3 and 2 disk effective radii (re), and a scatter compatible with random fluctuations around this value, when the gradient is normalized to the disk effective radius. The slope is independent of morphology, the incidence of bars, absolute magnitude, or mass. Only those galaxies with evidence of interactions and/or clear merging systems present a significantly shallower gradient, consistent with previous results. The majority of the 94 galaxies with H ii regions detected beyond two disk effective radii present a flattening in the oxygen abundance. The flattening is statistically significant. We cannot provide a conclusive answer regarding the origin of this flattening. However, our results indicate that its origin is most probably related to the secular evolution of galaxies. Finally, we find a drop/truncation of the oxygen abundance in the inner regions for 26 of the galaxies. All of them are non-interacting, mostly unbarred Sb/Sbc galaxies. This feature is associated with a central star-forming ring, which suggests that both features are produced by radial gas flows induced by resonance processes. Our result suggests that galaxy disks grow inside-out, with metal enrichment driven by the local star formation history and with a small variation galaxy-by-galaxy. At a certain

  2. Interstellar matter in early-type galaxies. II - The relationship between gaseous components and galaxy types

    NASA Technical Reports Server (NTRS)

    Bregman, Joel N.; Hogg, David E.; Roberts, Morton S.

    1992-01-01

    Interstellar components of early-type galaxies are established by galactic type and luminosity in order to search for relationships between the different interstellar components and to test the predictions of theoretical models. Some of the data include observations of neutral hydrogen, carbon monoxide, and radio continuum emission. An alternative distance model which yields LX varies as LB sup 2.45, a relation which is in conflict with simple cooling flow models, is discussed. The dispersion of the X-ray luminosity about this regression line is unlikely to result from stripping. The striking lack of clear correlations between hot and cold interstellar components, taken together with their morphologies, suggests that the cold gas is a disk phenomenon while the hot gas is a bulge phenomenon, with little interaction between the two. The progression of galaxy type from E to Sa is not only a sequence of decreasing stellar bulge-to-disk ratio, but also of hot-to-cold-gas ratio.

  3. Forming disc galaxies in major mergers - III. The effect of angular momentum on the radial density profiles of disc galaxies

    NASA Astrophysics Data System (ADS)

    Peschken, N.; Athanassoula, E.; Rodionov, S. A.

    2017-06-01

    We study the effect of angular momentum on the surface density profiles of disc galaxies, using high-resolution simulations of major mergers whose remnants have downbending radial density profiles (type II). As described in the previous papers of this series, in this scenario, most of the disc mass is acquired after the collision via accretion from a hot gaseous halo. We find that the inner and outer disc scalelengths, as well as the break radius, correlate with the total angular momentum of the initial merging system, and are larger for high-angular momentum systems. We follow the angular momentum redistribution in our simulated galaxies, and find that like the mass, the disc angular momentum is acquired via accretion, I.e. to the detriment of the gaseous halo. Furthermore, high-angular momentum systems give more angular momentum to their discs, which directly affects their radial density profile. Adding simulations of isolated galaxies to our sample, we find that the correlations are valid also for disc galaxies evolved in isolation. We show that the outer part of the disc at the end of the simulation is populated mainly by inside-out stellar migration, and that in galaxies with higher angular momentum, stars travel radially further out. This, however, does not mean that outer disc stars (in type II discs) were mostly born in the inner disc. Indeed, generally the break radius increases over time, and not taking this into account leads to overestimating the number of stars born in the inner disc.

  4. A Near Infrared Study of Blue Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Vanzi, L.

    1997-09-01

    Blue Dwarf Galaxies (BDG) are objects of low luminosity (M_Vge-18) and very blue visible colors. Both the colors and the presence of narrow emission lines in their spectra are usually interpreted to result from intense episodes of star formation. The metallicity of the BDG is usually low with values in the range 10^{-2}-1~Zodot. Wolf-Rayet (WR) features are detected in many cases in the optical spectra. This is an unexpected characteristic since according to stellar evolution, the number of WR stars in a star forming region should increase with the metallicity while WR features are only rarely detected in solar metallicity galaxies. Different morphologies are found among BDG including compact elliptical, irregular, magellanic, interacting. Due to the low luminosity in most of these objects the starburst (SB) episode dominates the emitted radiation. Therefore starbursts can be studied in more detail in dwarf galaxies than in giant spiral galaxies where the presence of a quiescent stellar population is important in defining the observed characteristics. Moreover BDG are a unique laboratory to study the star formation process in low metallicity environments. We have used new imaging and spectroscopy in the near infrared to study both the star formation history and the excitation mechanism of the near infrared lines in BDG. The observations were taken with the Steward Observatory telescopes. We concentrated on 8 objects selected to be a representative but bright sample of BDG, they are: II Zw 40, He2-10, NGC 3077, NGC 4214, NGC 4449, NGC 1569, NGC 4861 and NGC 5253. The data were used to constrain a starburst model. For II Zw 40 we were able to fit the observations using a gaussian star formation rate with FWHM=5 My and a solar neiborhood IMF. The star formation episode appears to have occured about 4 Myr ago with aproximately one tenth of the total mass of the galaxy involved. Evidence for an evolved population was found in the outer parts of II Zw 40. We also studied

  5. Characterizing ultraviolet and infrared observational properties for galaxies. II. Features of attenuation law

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mao, Ye-Wei; Kong, Xu; Lin, Lin, E-mail: ywmao@pmo.ac.cn, E-mail: xkong@ustc.edu.cn, E-mail: linlin@shao.ac.cn

    Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-β relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies,more » we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Å bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Å bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.« less

  6. Characterizing Ultraviolet and Infrared Observational Properties for Galaxies. II. Features of Attenuation Law

    NASA Astrophysics Data System (ADS)

    Mao, Ye-Wei; Kong, Xu; Lin, Lin

    2014-07-01

    Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-β relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Å bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Å bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.

  7. A photometric determination of twists in early-type galaxies. II

    NASA Technical Reports Server (NTRS)

    Williams, T. B.; Schwarzschild, M.

    1979-01-01

    In continuation of previous work, detailed photometric data have been obtained for two elliptical galaxies by using the Mount Lemmon 1.5-m telescope and a large SEC television camera. As before, the aim of this photometry is to gain additional information on the occurrence of twists in such galaxies; i.e., on the change of the position angle of the major axes of the isophotes from the center outward. No significant twist was found in NGC 1052. However, NGC 584 was found to have a securely observed twist of about 10 deg within 10 kpc from its center. These data strengthen previous indications that many ellipticals contain twists in their inner, bright portions.

  8. Modeling MgII Absorbers from SDSS Spectroscopic and Imaging Catalogs

    NASA Astrophysics Data System (ADS)

    Rimoldini, L. G.; Menard, B.; Nestor, D. B.; Rao, S. M.; Sheth, R. K.; Turnshek, D. A.; Zibetti, S.; Feather, S.; Quider, A.

    2005-12-01

    The detection of more than 14,000 MgII absorption doublets along the sight-lines to SDSS DR4 QSOs (pursued by Turnshek, Nestor, Rao, and collaborators) has produced the largest sample of MgII absorbers to date in the redshift interval 0.37 < z < 2.30. The statistical relation between galaxies and MgII systems is investigated by cross-correlating the spectroscopic MgII catalog with the SDSS imaging catalog of galaxies in the neighborhood of QSO sight-lines. A model for MgII absorbers is derived to account for the measured MgII rest equivalent width distribution and the absorbing galaxy properties (e.g., luminosity, impact parameter, and morphological type). Some preliminary results of our analysis are presented. This work was supported in part by the National Science Foundation. L.G.R. acknowledges further support from the Z. Daniel's Predoctoral Fellowship.

  9. An XMM-Newton spectral survey of 12 μm selected galaxies - II. Implications for AGN selection and unification

    NASA Astrophysics Data System (ADS)

    Brightman, Murray; Nandra, Kirpal

    2011-07-01

    We present a multi-waveband analysis of a 126-galaxy sub-sample of the 12 μm galaxy sample (12MGS), for which we have carried out a detailed X-ray spectral analysis in a previous paper. We determine the activity class of the galaxies by way of optical-line ratio diagnostics and characterize the optical classes by their X-ray, 12 μm and [O III] luminosities and X-ray spectral properties. Our most interesting results from this investigation are as follows. (i) Seyfert (Sy) 1s and Sy2s show a significantly different X-ray luminosity distributions from each other. (ii) Sy2 galaxies with a detection of a hidden broad-line region show a significantly higher X-ray luminosity than those without a detection, supporting the findings of Tran. (iii) Sy1s also present a significantly different 12 μm luminosity distribution from both intermediate Sy types and Sy2s. (iv) The Sy2 fraction decreases towards high X-ray luminosities. (v) X-ray indications of active galactic nuclei (AGN) power agree well with the optical classifications. (vi) There is X-ray evidence for the presence of an AGN in 17 per cent of H II/AGN composite galaxies and 40 per cent of LINERs. (vii) We advocate the use of a 2-10 keV X-ray luminosity of 1041 erg s-1 in the X-ray selection of AGN, rather than 1042 erg s-1, which we find gives a contamination rate of only 3 per cent from star-forming galaxies. (viii) From an analysis of the X-ray power-law index, Γ, we find that Sy1s and Sy2 have the same intrinsic distributions, implying that the central engines are the same, in support of AGN unification schemes. (ix) In 24 per cent of cases the absorption measured in the X-ray spectra does not correspond directly to that implied in the optical band from the visibility of the broad-line regions (BLRs), which is in conflict with AGN unification schemes. (x) We confirm the previous work showing that the obscured fraction in AGN declines at high X-ray luminosity, but also find a decrease at low luminosity having

  10. Understanding r-process nucleosynthesis with dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Ji, Alexander P.

    2018-06-01

    The Milky Way's faintest dwarf galaxy satellites each sample short, independent bursts of star formation from the first 1-2 Gyr of the universe. Their simple formation history makes them ideal systems to understand how rare events like neutron star mergers contribute to early enrichment of r-process elements. I will focus on the ultra-faint galaxy Reticulum II, which experienced a single prolific r-process event that left ~80% of its stars extremely enriched in r-process elements. I will present abundances of ~40 elements derived from the highest signal-to-noise high-resolution spectrum ever taken for an ultra-faint dwarf galaxy star. Precise measurements of elements from all three r-process peaks reaffirm the universal nature of the r-process abundance pattern from Ba to Ir. The first r-process peak is significantly lower than solar but matches other r-process enhanced stars. This constrains the neutron-richness of r-process ejecta in neutron star mergers. The radioactive element thorium is detected with a somewhat low abundance. Naive application of currently predicted initial production ratios could imply an age >20 Gyr, but more likely indicates that the initial production ratios require revision. The abundance of lighter elements up to Zn are consistent with extremely metal-poor Milky Way halo stars. These elements may eventually provide a way to test for other hypothesized r-process sites, but only after a more detailed understanding of the chemical evolution in this galaxy. Reticulum II provides a clean view of early r-process enrichment that can be used to understand the increasing number of r-process measurements in other dwarf galaxies.

  11. Galaxy triplets in Sloan Digital Sky Survey Data Release 7 - II. A connection with compact groups?

    NASA Astrophysics Data System (ADS)

    Duplancic, Fernanda; O'Mill, Ana Laura; Lambas, Diego G.; Sodré, Laerte; Alonso, Sol

    2013-08-01

    We analyse a sample of 71 triplets of luminous galaxies derived from the work of O'Mill et al. We compare the properties of triplets and their members with those of control samples of compact groups, the 10 brightest members of rich clusters and galaxies in pairs. The triplets are restricted to have members with spectroscopic redshifts in the range 0.01 ≤ z ≤ 0.14 and absolute r-band luminosities brighter than Mr = -20.5. For these member galaxies, we analyse the stellar mass content, the star formation rates, the Dn(4000) parameter and (Mg - Mr) colour index. Since galaxies in triplets may finally merge in a single system, we analyse different global properties of these systems. We calculate the probability that the properties of galaxies in triplets are strongly correlated. We also study total star formation activity and global colours, and define the triplet compactness as a measure of the percentage of the system total area that is filled by the light of member galaxies. We concentrate in the comparison of our results with those of compact groups to assess how the triplets are a natural extension of these compact systems. Our analysis suggests that triplet galaxy members behave similarly to compact group members and galaxies in rich clusters. We also find that systems comprising three blue, star-forming, young stellar population galaxies (blue triplets) are most probably real systems and not a chance configuration of interloping galaxies. The same holds for triplets composed of three red, non-star-forming galaxies, showing the correlation of galaxy properties in these systems. From the analysis of the triplet as a whole, we conclude that, at a given total stellar mass content, triplets show a total star formation activity and global colours similar to compact groups. However, blue triplets show a high total star formation activity with a lower stellar mass content. From an analysis of the compactness parameter of the systems we find that light is even more

  12. The edge of galaxy formation - II. Evolution of Milky Way satellite analogues after infall

    NASA Astrophysics Data System (ADS)

    Frings, Jonas; Macciò, Andrea; Buck, Tobias; Penzo, Camilla; Dutton, Aaron; Blank, Marvin; Obreja, Aura

    2017-12-01

    In the first paper, we presented 27 hydrodynamical cosmological simulations of galaxies with total masses between 5 × 108 and 1010 M⊙. In this second paper, we use a subset of these cosmological simulations as initial conditions (ICs) for more than 40 hydrodynamical simulations of satellite and host galaxy interaction. Our cosmological ICs seem to suggest that galaxies on these mass scales have very little rotational support and are velocity dispersion (σ) dominated. Accretion and environmental effects increase the scatter in the galaxy scaling relations (e.g. size-velocity dispersion) in very good agreement with observations. Star formation is substantially quenched after accretion. Mass removal due to tidal forces has several effects: it creates a very flat stellar velocity dispersion profile, and it reduces the dark matter content at all scales (even in the centre), which in turn lowers the stellar velocity on scales around 0.5 kpc even when the galaxy does not lose stellar mass. Satellites which start with a cored dark matter profile are more prone to either be destroyed or to end up in a very dark matter poor galaxy. Finally, we found that tidal effects always increase the 'cuspyness' of the dark matter profile, even for haloes that infall with a core.

  13. The association between gas and galaxies - II. The two-point correlation function

    NASA Astrophysics Data System (ADS)

    Wilman, R. J.; Morris, S. L.; Jannuzi, B. T.; Davé, R.; Shone, A. M.

    2007-02-01

    We measure the two-point correlation function, ξAG, between galaxies and quasar absorption-line systems at z < 1, using the data set of Morris & Jannuzi on 16 lines-of-sight (LOS) with ultraviolet (UV) spectroscopy and galaxy multi-object spectroscopy (Paper I). The measurements are made in 2D redshift space out to π = 20h-1 Mpc (comoving) along the LOS and out to σ = 2h-1 Mpc projected; as a function of HI column density in the range NHI = 1013-1019cm-2, also for CIV absorption systems, and as a function of galaxy spectral type. This extends the absorber-galaxy pair analysis of Paper I. We find that the amplitude of the peak in ξAG at the smallest separations increases slowly as the lower limit on NHI is increased from 1013 to 1016cm-2, and then jumps sharply (albeit with substantial uncertainties) for NHI > 1017cm-2. For CIV absorbers, the peak strength of ξAG is roughly comparable to that of HI absorbers with NHI > 1016.5cm-2, consistent with the finding that the CIV absorbers are associated with strong HI absorbers. We do not reproduce the differences reported by Chen et al. between 1D ξAG measurements using galaxy subsamples of different spectral types. However, the full impact on the measurements of systematic differences in our samples is hard to quantify. We compare the observations with smoothed particle hydrodynamical (SPH) simulations and discover that in the observations ξAG is more concentrated to the smallest separations than in the simulations. The latter also display a `finger of god' elongation of ξAG along the LOS in redshift space, which is absent from our data, but similar to that found by Ryan-Weber for the cross-correlation of quasar absorbers and HI-emission-selected galaxies. The physical origin of these `fingers of god' is unclear, and we thus highlight several possible areas for further investigation.

  14. A new method for finding and characterizing galaxy groups via low-frequency radio surveys

    NASA Astrophysics Data System (ADS)

    Croston, J. H.; Ineson, J.; Hardcastle, M. J.; Mingo, B.

    2017-09-01

    We describe a new method for identifying and characterizing the thermodynamic state of large samples of evolved galaxy groups at high redshifts using high-resolution, low-frequency radio surveys, such as those that will be carried out with LOFAR and the Square Kilometre Array. We identify a sub-population of morphologically regular powerful [Fanaroff-Riley type II (FR II)] radio galaxies and demonstrate that, for this sub-population, the internal pressure of the radio lobes is a reliable tracer of the external intragroup/intracluster medium (ICM) pressure, and that the assumption of a universal pressure profile for relaxed groups enables the total mass and X-ray luminosity to be estimated. Using a sample of well-studied FR II radio galaxies, we demonstrate that our method enables the estimation of group/cluster X-ray luminosities over three orders of magnitude in luminosity to within a factor of ˜2 from low-frequency radio properties alone. Our method could provide a powerful new tool for building samples of thousands of evolved galaxy groups at z > 1 and characterizing their ICM.

  15. On star formation in stellar systems. II - Photoionization in protodwarf galaxies

    NASA Technical Reports Server (NTRS)

    Noriega-Crespo, A.; Bodenheimer, P.; Lin, D. N. C.; Tenorio-Tagle, G.

    1989-01-01

    Numerical hydrodynamical calculations are used to study the effects of the onset of star formation on the residual gas in a primordial low-mass Local-Group dwarf spheroidal galaxy in the size range 0.3-1.0 kpc. It is demonstrated that photoionization in the presence of a moderate gas-density gradient can be responsible for gas ejection on a time-scale of a few times 10 to the 7th yr. The results indicate that, given a normal initial mass function, many protodwarf galaxies may have been dispersed by the onset of star formation.

  16. The kinematics and morphology of cool galactic winds and halo gas from galaxies at 0.3 < z < 1.4

    NASA Astrophysics Data System (ADS)

    Rubin, Kate H. R.

    Large-scale redshift surveys tracing the evolution of the luminous components of galaxies have revealed both an increase in the number density of "red and dead" galaxies and a concomitant decline in the star formation rates (SFRs) of blue galaxies since z ˜ 1. The latter is predicted to be due to a decreasing cool gas supply over time; whereas the former may be explained by the theory of merger-driven galaxy evolution, which suggests that the merging of blue galaxies expels the interstellar medium (ISM), thereby quenching star formation in the remnant. While these theoretical explanations provide robust predictions for the evolution of the gaseous components of distant galaxies, we have few direct measurements of the location and kinematics of cool gas around galaxies beyond the local universe. This thesis uses three complementary observational techniques to provide new constraints on the kinematics and morphology of cool gas in galaxies at 0.3 < z < 1.4. First, we use spectra of ˜470 galaxies at 0.7 < z < 1.5 drawn from the Team Keck Treasury Redshift Survey to study absorption line profiles for the Mg II lambdalambda2796, 2803 and Fe II lambdalambda2586, 2600 transitions, which probe cool, photoionized gas with temperature T ˜ 10 4 K. By coadding several sub-samples of galaxy spectra, we identify gaseous outflows via the Doppler shift of the absorption lines, and find that outflows are ubiquitous in galaxies having SFR > 10 M⊙ yr-1 and stellar masses ≳1010.5M⊙ . By comparing these results to those of Weiner et al. (2009), who present a similar study of outflows in star-forming galaxies at z ˜ 1.4, we find that these outflows persist in high-mass galaxies as they age between z ˜ 1.4 and z ˜ 1. Using HST/ACS imaging of our galaxy sample, we present evidence for a weak trend of increasing outflow absorption strength with increasing galaxy SFR surface density (SigmaSFR). Theoretical studies suggest that a minimum SigmaSFR must be exceeded in the host

  17. Formation and evolution of dwarf elliptical galaxies - II. Spatially resolved star formation histories

    NASA Astrophysics Data System (ADS)

    Koleva, Mina; de Rijcke, Sven; Prugniel, Philippe; Zeilinger, Werner W.; Michielsen, Dolf

    2009-07-01

    We present optical Very Large Telescope spectroscopy of 16 dwarf elliptical galaxies (dEs) comparable in mass to NGC 205, and belonging to the Fornax cluster and to nearby groups of galaxies. Using full-spectrum fitting, we derive radial profiles of the SSP-equivalent ages and metallicities. We make a detailed analysis with ULYSS and STECKMAP of the star formation history in the core of the galaxies and in an aperture of one effective radius. We resolved the history into one to four epochs. The statistical significance of these reconstructions was carefully tested; the two programs give remarkably consistent results. The old stellar population of the dEs, which dominates their mass, is likely coeval with that of massive ellipticals or bulges, but the star formation efficiency is lower. Important intermediate age (1-5 Gyr) populations and frequently tails of star formation until recent times are detected. These histories are reminiscent of their lower mass dwarf spheroidal counterparts of the Local Group. Most galaxies (10/16) show significant metallicity gradients, with metallicity declining by 0.5 dex over one half-light radius on average. These gradients are already present in the old population. The flattened (or discy), rotating objects (6/16) have flat metallicity profiles. This may be consistent with a distinct origin for these galaxies or it may be due to their geometry. The central single stellar population equivalent age varies between 1 and 6 Gyr, with the age slowly increasing with radius in the vast majority of objects. The group and cluster galaxies have similar radial gradients and star formation histories. The strong and old metallicity gradients place important constraints on the possible formation scenarios of dEs. Numerical simulations of the formation of spherical low-mass galaxies reproduce these gradients, but they require a longer time for them to build up. A gentle depletion of the gas, by ram pressure stripping or starvation, could drive the

  18. Detection of the 158 Micrometers[CII] Transition at z=1.3: Evidence for a Galaxy-Wide Starburst

    NASA Technical Reports Server (NTRS)

    Hailey-Dunsheath, S.; Nikola, T.; Stacey, G. J.; Oberst, T. E.; Parshley, S. C.; Benford, D. J.; Staguhn, J. G.; Tucker, C. E.

    2010-01-01

    We report the detection of 158 micrometer [C II] fine-structure line emission from MIPS J 142824.0+3526l9, a hyperluminous (L(sub IR) approx. 10(exp 13) Solar Luminosity starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L[C II]/L(sub FIR) approx. equals 2 x l0(exp -3) of the far-IR(FIR) continuum. The [C II], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n approx. 10(exp 4.2)/cu cm., and that are illuminated by a far-UV radiation field approx. 10(exp 3.2) times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L[C II]/L(sub F1R) ratio is higher than observed in local ultraluminous infrared galaxies or in the few high-redshift QSOs detected in [C II], but the L[CII]/L(sub FIR) and L(sub CO)/L(sub FIR) ratios are similar to the values seen in nearby starburst galaxies

  19. Reddening and extinction towards H II regions

    NASA Technical Reports Server (NTRS)

    Caplan, James; Deharveng, Lise

    1989-01-01

    The light emitted by the gas in H II regions is attenuated by dust. This extinction can be measured by comparing H alpha, H beta, and radio continuum fluxes, since the intrinsic ratios of the Balmer line and thermal radio continuum emissivities are nearly constant for reasonable conditions in H II regions. In the case of giant extragalactic H II regions, the extinction was found to be considerably greater than expected. The dust between the Earth and the emitting gas may have an optical thickness which varies. The dust may be close enough to the source that scattered light contributes to the flux, or the dust may be actually mixed with the emitting gas. It is difficult to decide which configuration is correct. A rediscussion of this question in light of recent observations, with the Fabry-Perot spectrophotometers, of the large Galactic H II region is presented. The color excesses are compared for stars embedded in these H II regions with those derived (assuming the standard law) from the nebular extinction and reddening.

  20. Hubble Sees Galaxies Spiraling around Leo

    NASA Image and Video Library

    2014-04-18

    Shown here is a spiral galaxy known as NGC 3455, which lies some 65 million light-years away from us in the constellation of Leo (the Lion). Galaxies are classified into different types according to their structure and appearance. This classification system is known as the Hubble Sequence, named after its creator Edwin Hubble. In this image released 14, April, 2014, NGC 3455 is known as a type SB galaxy — a barred spiral. Barred spiral galaxies account for approximately two thirds of all spirals. Galaxies of this type appear to have a bar of stars slicing through the bulge of stars at their center. The SB classification is further sub-divided by the appearance of a galaxy's pinwheeling spiral arms; SBa types have more tightly wound arms, whereas SBc types have looser ones. SBb types, such as NGC 3455, lie in between. NGC 3455 is part of a pair of galaxies — its partner, NGC 3454, lies out of frame. This cosmic duo belong to a group known as the NGC 3370 group, which is in turn one of the Leo II groups, a large collection of galaxies scattered some 30 million light-years to the right of the Virgo cluster. This image is from Hubble's Advanced Camera for Surveys. Credit: ESA/Hubble & NASA, Acknowledgement: Nick Rose NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  1. Nuclear Star Formation in the Hot-Spot Galaxy NGC 2903

    NASA Technical Reports Server (NTRS)

    Alonso-Herrero, A.; Ryder, S. D.; Knapen, J. H.

    1994-01-01

    We present high-resolution near-infrared imaging obtained using adaptive optics and HST/NICMOS and ground-based spectroscopy of the hot-spot galaxy NGC 2903. Our near-infrared resolution imaging enables us to resolve the infrared hot spots into individual young stellar clusters or groups of these. The spatial distribution of the stellar clusters is not coincident with that of the bright H II regions, as revealed by the HST/NICMOS Pace image. Overall, the circumnuclear star formation in NGC 2903 shows a ring-like morphology with an approximate diameter of 625 pc. The SF properties of the stellar clusters and H II regions have been studied using the photometric and spectroscopic information in conjunction with evolutionary synthesis models. The population of bright stellar clusters shows a very narrow range of ages, 4 to 7 x 10(exp 6) yr after the peak of star formation, or absolute ages 6.5 to 9.5 x 10(exp 6) yr (for the assumed short-duration Gaussian bursts), and luminosities similar to the clusters found in the Antennae interacting galaxy. This population of young stellar clusters accounts for some 7 - 12% of the total stellar mass in the central 625 pc of NGC 2903. The H II regions in the ring of star formation have luminosities close to that of the super-giant H II region 30 Doradus, they are younger than the stellar clusters, and will probably evolve into bright infrared stellar clusters similar to those observed today. We find that the star formation efficiency in the central regions of NGC 2903 is higher than in normal galaxies, approaching the lower end of infrared luminous galaxies.

  2. Exploring the dust content of galactic winds with Herschel - II. Nearby dwarf galaxies

    NASA Astrophysics Data System (ADS)

    McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

    2018-06-01

    We present the results from an analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20 per cent of the total dust mass in these galaxies resides outside of their stellar discs, but this fraction reaches ˜60 per cent in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disc by energy inputs from ongoing star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disc by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disc that lies below the sensitivity limit of the Spitzer 4.5 μm data.

  3. Stars and gas in the most metal-deficient galaxies in the Universe.

    NASA Astrophysics Data System (ADS)

    Wofford, Aida

    2017-08-01

    Improving our understanding of star formation at low metallicity is of large relevance for a variety of fields in astrophysics since it relates to multiple topical questions. These range from understanding the properties of galaxies that contributed to cosmic reionization to the evolution of metal poor massive stars that give rise to the formation of heavy binary black holes. Crucial are observational constraints for the theoretical predictions, which can be obtained from rest-frame UV spectra of local star-forming dwarf galaxies with ionized-gas oxygen abundances at the low-metallicity threshold of the nearby Universe.While samples of UV spectra exist for galaxies in the metallicity range above 1/20 solar, only two useful spectra covering from H I Lyman-alpha (LyA, 1216 Ang) to C III] 1909 are available at lower metallicites. We propose COS G140L observations of eight extremely-metal poor galaxies (XMPGs) with He II emission that will: i) provide three more spectra with 12+log(O/H)=<7.4 (suitable targets at such low Z are hard to find), and ii) leverage existing WFC3 and Chandra images which are useful for discrimintating among different sources of ionization. Combining this dataset with existing spectra at similar and higher metallicity will allow us to address three questions: 1) How does metallicity determine galaxy properties?, 2) Is narrow He II emission a good tracer of peculiar massive stars?, and 3) Can we probe star-formation at high redshift with UV lines other than LyA? Our study will provide valuable clues for interpreting rest-frame UV spectra of high-z galaxies that will challenge our understanding of star formation at low Z.

  4. HICOSMO: cosmology with a complete sample of galaxy clusters - II. Cosmological results

    NASA Astrophysics Data System (ADS)

    Schellenberger, G.; Reiprich, T. H.

    2017-10-01

    The X-ray bright, hot gas in the potential well of a galaxy cluster enables systematic X-ray studies of samples of galaxy clusters to constrain cosmological parameters. HIFLUGCS consists of the 64 X-ray brightest galaxy clusters in the Universe, building up a local sample. Here, we utilize this sample to determine, for the first time, individual hydrostatic mass estimates for all the clusters of the sample and, by making use of the completeness of the sample, we quantify constraints on the two interesting cosmological parameters, Ωm and σ8. We apply our total hydrostatic and gas mass estimates from the X-ray analysis to a Bayesian cosmological likelihood analysis and leave several parameters free to be constrained. We find Ωm = 0.30 ± 0.01 and σ8 = 0.79 ± 0.03 (statistical uncertainties, 68 per cent credibility level) using our default analysis strategy combining both a mass function analysis and the gas mass fraction results. The main sources of biases that we correct here are (1) the influence of galaxy groups (incompleteness in parent samples and differing behaviour of the Lx-M relation), (2) the hydrostatic mass bias, (3) the extrapolation of the total mass (comparing various methods), (4) the theoretical halo mass function and (5) other physical effects (non-negligible neutrino mass). We find that galaxy groups introduce a strong bias, since their number density seems to be over predicted by the halo mass function. On the other hand, incorporating baryonic effects does not result in a significant change in the constraints. The total (uncorrected) systematic uncertainties (∼20 per cent) clearly dominate the statistical uncertainties on cosmological parameters for our sample.

  5. The nebular spectra of the transitional Type Ia Supernovae 2007on and 2011iv: broad, multiple components indicate aspherical explosion cores

    NASA Astrophysics Data System (ADS)

    Mazzali, P. A.; Ashall, C.; Pian, E.; Stritzinger, M. D.; Gall, C.; Phillips, M. M.; Höflich, P.; Hsiao, E.

    2018-05-01

    The nebular-epoch spectrum of the rapidly declining, `transitional' Type Ia supernova (SN) 2007on showed double emission peaks, which have been interpreted as indicating that the SN was the result of the direct collision of two white dwarfs. The spectrum can be reproduced using two distinct emission components, one redshifted and one blueshifted. These components are similar in mass but have slightly different degrees of ionization. They recede from one another at a line-of-sight speed larger than the sum of the combined expansion velocities of their emitting cores, thereby acting as two independent nebulae. While this configuration appears to be consistent with the scenario of two white dwarfs colliding, it may also indicate an off-centre delayed detonation explosion of a near-Chandrasekhar-mass white dwarf. In either case, broad emission line widths and a rapidly evolving light curve can be expected for the bolometric luminosity of the SN. This is the case for both SNe 2007on and 2011iv, also a transitional SN Ia that exploded in the same elliptical galaxy, NGC 1404. Although SN 2011iv does not show double-peaked emission line profiles, the width of its emission lines is such that a two-component model yields somewhat better results than a single-component model. Most of the mass ejected is in one component, however, which suggests that SN 2011iv was the result of the off-centre ignition of a Chandrasekhar-mass white dwarf.

  6. The ionized gas in the CALIFA early-type galaxies. I. Mapping two representative cases: NGC 6762 and NGC 5966

    NASA Astrophysics Data System (ADS)

    Kehrig, C.; Monreal-Ibero, A.; Papaderos, P.; Vílchez, J. M.; Gomes, J. M.; Masegosa, J.; Sánchez, S. F.; Lehnert, M. D.; Cid Fernandes, R.; Bland-Hawthorn, J.; Bomans, D. J.; Marquez, I.; Mast, D.; Aguerri, J. A. L.; López-Sánchez, Á. R.; Marino, R. A.; Pasquali, A.; Perez, I.; Roth, M. M.; Sánchez-Blázquez, P.; Ziegler, B.

    2012-04-01

    As part of the ongoing CALIFA survey, we have conducted a thorough bidimensional analysis of the ionized gas in two E/S0 galaxies, NGC 6762 and NGC 5966, aiming to shed light on the nature of their warm ionized ISM. Specifically, we present optical (3745-7300 Å) integral field spectroscopy obtained with the PMAS/PPAK integral field spectrophotometer. Its wide field-of-view (1' × 1') covers the entire optical extent of each galaxy down to faint continuum surface brightnesses. To recover the nebular lines, we modeled and subtracted the underlying stellar continuum from the observed spectra using the STARLIGHT spectral synthesis code. The pure emission-line spectra were used to investigate the gas properties and determine the possible sources of ionization. We show the advantages of IFU data in interpreting the complex nature of the ionized gas in NGC 6762 and NGC 5966. In NGC 6762, the ionized gas and stellar emission display similar morphologies, while the emission line morphology is elongated in NGC 5966, spanning ~6 kpc, and is oriented roughly orthogonal to the major axis of the stellar continuum ellipsoid. Whereas gas and stars are kinematically aligned in NGC 6762, the gas is kinematically decoupled from the stars in NGC 5966. A decoupled rotating disk or an "ionization cone" are two possible interpretations of the elongated ionized gas structure in NGC 5966. The latter would be the first "ionization cone" of such a dimension detected within a weak emission-line galaxy. Both galaxies have weak emission-lines relative to the continuum[EW(Hα) ≲ 3 Å] and have very low excitation, log([Oiii]λ5007/Hβ) ≲ 0.5. Based on optical diagnostic ratios ([Oiii]λ5007/Hβ, [Nii]λ6584/Hα, [Sii]λ6717, 6731/Hα, [Oi]λ6300/Hα), both objects contain a LINER nucleus and an extended LINER-like gas emission. The emission line ratios do not vary significantly with radius or aperture, which indicates that the nebular properties are spatially homogeneous. The gas emission

  7. Radial Color and Mass Profile Trends of Dwarf Irregular Galaxies

    NASA Astrophysics Data System (ADS)

    Herrmann, Kimberly A.; Hunter, D. A.; THINGS, LITTLE

    2014-01-01

    Radial stellar surface brightness (SB) profiles of spiral galaxies can be classified into three types: (I) single exponential, (II) truncated: the light falls off with one exponential out to a break radius and then falls off more steeply, and (III) anti-truncated: the light falls off with one exponential out to a break radius and then falls off less steeply. Stellar SB profile breaks are also found in dwarf disk galaxies, but with an additional sub-category of Type II profiles: (FI) flat-inside: the light is roughly constant or increasing and then falls off beyond a break. Additionally, Bakos, Trujillo, & Pohlen (2008) showed that for spirals, each profile type has a characteristic color trend with respect to the break location which can be combined with color mass-to-light ratio relationships to examine radial mass profiles as well. Here we show radial color and mass profile trends for the three main SB types from a large multi-wavelength photometric study of dwarf irregular galaxies (the 141 dwarf parent sample of the LITTLE THINGS galaxies). We explore the similarities and differences between spirals and dwarfs and also between different colors.

  8. Far-infrared line emission from the galaxy. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Stacey, G. J.

    1985-01-01

    The diffuse 157.74 micron (CII) emission from the Galaxy was sampled at several galactic longitudes near the galactic plane including complete scan across the plane at (II) = 2.16 deg and (II) = 7.28 deg. The observed (CII) emission profiles follow closely the nearby (12)CO (J=1to0) emission profiles. The (CII) emission probably arises in neutral photodissociation regions near the edges of giant moleclar clouds (GMC's). These regions have densities of approximately 350 cm(-3) and temperatures of approximately 300 K, and amount to 4x10(8) solar mass of hydrogen in the inner Galaxy. The total 157.74 micron luminosity of the Galaxy is estimated to be 6x10(7) solar luminosity. Estimates were also made of the galactic emission in other far-infrared (FIR) cooling lines. The (CII) line was found to be the dominant FIR emission line from the galaxy and the primary coolant for the warm neutral gas near the galactic plane. Other cooling lines predicted to be prominent in the galactic spectrum are discussed. The 145.53 micron (OI) emission line from the Orion nebula was also measured.

  9. Galaxy Cluster Mass Reconstruction Project - II. Quantifying scatter and bias using contrasting mock catalogues

    DOE PAGES

    Old, L.; Wojtak, R.; Mamon, G. A.; ...

    2015-03-26

    Our paper is the second in a series in which we perform an extensive comparison of various galaxy-based cluster mass estimation techniques that utilize the positions, velocities and colours of galaxies. Our aim is to quantify the scatter, systematic bias and completeness of cluster masses derived from a diverse set of 25 galaxy-based methods using two contrasting mock galaxy catalogues based on a sophisticated halo occupation model and a semi-analytic model. Analysing 968 clusters, we find a wide range in the rms errors in log M200c delivered by the different methods (0.18–1.08 dex, i.e. a factor of ~1.5–12), with abundance-matchingmore » and richness methods providing the best results, irrespective of the input model assumptions. In addition, certain methods produce a significant number of catastrophic cases where the mass is under- or overestimated by a factor greater than 10. Given the steeply falling high-mass end of the cluster mass function, we recommend that richness- or abundance-matching-based methods are used in conjunction with these methods as a sanity check for studies selecting high-mass clusters. We also see a stronger correlation of the recovered to input number of galaxies for both catalogues in comparison with the group/cluster mass, however, this does not guarantee that the correct member galaxies are being selected. Finally, we did not observe significantly higher scatter for either mock galaxy catalogues. These results have implications for cosmological analyses that utilize the masses, richnesses, or abundances of clusters, which have different uncertainties when different methods are used.« less

  10. The ROSAT Brightest Cluster Sample - III. Optical spectra of the central cluster galaxies

    NASA Astrophysics Data System (ADS)

    Crawford, C. S.; Allen, S. W.; Ebeling, H.; Edge, A. C.; Fabian, A. C.

    1999-07-01

    We present new spectra of dominant galaxies in X-ray-selected clusters of galaxies, which combine with our previously published spectra to form a sample of 256 dominant galaxies in 215 clusters. 177 of the clusters are members of the ROSAT Brightest Cluster Sample (BCS; Ebeling et al.), and 17 have no previous measured redshift. This is the first paper in a series correlating the properties of brightest cluster galaxies and their host clusters in the radio, optical and X-ray wavebands. 27 per cent of the central dominant galaxies have emission-line spectra, all but five with line intensity ratios typical of cooling flow nebulae. A further 6 per cent show only [N ii]lambdalambda6548,6584 with Hα in absorption. We find no evidence for an increase in the frequency of line emission with X-ray luminosity. Purely X-ray-selected clusters at low redshift have a higher probability of containing line emission. The projected separation between the optical position of the dominant galaxy and its host cluster X-ray centroid is less for the line-emitting galaxies than for those without line emission, consistent with a closer association of the central galaxy and the gravitational centre in cooling flow clusters. The more Hα-luminous galaxies have larger emission-line regions and show a higher ratio of Balmer to forbidden line emission, although there is a continuous trend of ionization behaviour across four decades in Hα luminosity. Galaxies with the more luminous line emission [L(Hα)> 10^41ergs^-1] show a significantly bluer continuum, whereas lower luminosity and [N ii]-only line emitters have continua that differ little from those of non-line-emitting dominant galaxies. Values of the Balmer decrement in the more luminous systems commonly imply intrinsic reddening of E(B-V)~0.3 and, when this is corrected for, the excess blue light can be characterized by a population of massive young stars. Several of the galaxies require a large population of O stars, which also provide

  11. Seyfert Galaxies in the Infrared

    NASA Astrophysics Data System (ADS)

    Ruiz-Nishiky, Milagros

    1997-10-01

    This thesis contains complementary aspects of the Seyfert phenomenon, each of which is analysed to bring a better understanding of present unification theories. Observations of the nuclear regions of various types of Seyfert galaxies were mostly made at infrared wavelengths which allow the study of dusty environments and provide new information on the physical conditions of these objects. For example, near infrared spectroscopy of Seyfert 2 galaxies revealed that there is a subclass of type 2 Seyferts with hot IR excess at ~3μm with broad IR emission lines suggesting that some Seyfert 2s do in fact contain a hidden Seyfert 1 nucleus. Additional spectropolarimetry showed that the scattering screens, postulated in the standard model, are not always present in Seyfert 2s. At mid infrared wavelengths, it was found that the 10 μm nuclear emission of Seyferts with broad emission lines is intrinsically brighter than that of Seyferts with no broad lines. The extended 10μm emission shows that Seyfert 2 galaxies present enhanced star-formation when compared to Seyfert 1s. Both results pose obstacles for present unification ideas and I discuss possible interpretations to these observations. Seyfert galaxies were also observed at radio wavelengths to study their large scale emission of 1-0 CO. Surprisingly, this emission usually related with star formation activity was found to be similar in both types of Seyfert galaxies and therefore does not explain why Seyfert 2 galaxies have enhanced star formation as concluded in the 10μm study. A study of galaxy morphology and companions in this set of Seyferts shows at a significant statistical level that Seyfert 2s present a higher incidence of asymmetric morphologies compared to Seyfert 1s and field galaxies, and therefore are undergoing gravitational perturbations which may induce star formation. Near infrared spectroscopy of a large sample of Seyfert galaxies is analysed to study the excitation mechanisms of (FeII) and H2 lines

  12. 3D-HST emission line galaxies at z ∼ 2: discrepancies in the optical/UV star formation rates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zeimann, Gregory R.; Ciardullo, Robin; Gebhardt, Henry

    2014-08-01

    We use Hubble Space Telescope near-IR grism spectroscopy to examine the Hβ line strengths of 260 star-forming galaxies in the redshift range 1.90 < z < 2.35. We show that at these epochs, the Hβ star formation rate (SFR) is a factor of ∼1.8 higher than what would be expected from the systems' rest-frame UV flux density, suggesting a shift in the standard conversion between these quantities and SFR. We demonstrate that at least part of this shift can be attributed to metallicity, as Hβ is more enhanced in systems with lower oxygen abundance. This offset must be considered whenmore » measuring the SFR history of the universe. We also show that the relation between stellar and nebular extinction in our z ∼ 2 sample is consistent with that observed in the local universe.« less

  13. SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR–M ∗ Relations on Galaxy Properties

    NASA Astrophysics Data System (ADS)

    Pan, Hsi-An; Lin, Lihwai; Hsieh, Bau-Ching; Sánchez, Sebastián F.; Ibarra-Medel, Héctor; Boquien, Médéric; Lacerna, Ivan; Argudo-Fernández, Maria; Bizyaev, Dmitry; Cano-Díaz, Mariana; Drory, Niv; Gao, Yang; Masters, Karen; Pan, Kaike; Tabor, Martha; Tissera, Patricia; Xiao, Ting

    2018-02-01

    The galaxy integrated Hα star formation rate–stellar mass relation, or SFR(global)–M *(global) relation, is crucial for understanding star formation history and evolution of galaxies. However, many studies have dealt with SFR using unresolved measurements, which makes it difficult to separate out the contamination from other ionizing sources, such as active galactic nuclei and evolved stars. Using the integral field spectroscopic observations from SDSS-IV MaNGA, we spatially disentangle the contribution from different Hα powering sources for ∼1000 galaxies. We find that, when including regions dominated by all ionizing sources in galaxies, the spatially resolved relation between Hα surface density (ΣHα (all)) and stellar mass surface density (Σ*(all)) progressively turns over at the high Σ*(all) end for increasing M *(global) and/or bulge dominance (bulge-to-total light ratio, B/T). This in turn leads to the flattening of the integrated Hα(global)–M *(global) relation in the literature. By contrast, there is no noticeable flattening in both integrated Hα(H II)–M *(H II) and spatially resolved ΣHα (H II)–Σ*(H II) relations when only regions where star formation dominates the ionization are considered. In other words, the flattening can be attributed to the increasing regions powered by non-star-formation sources, which generally have lower ionizing ability than star formation. An analysis of the fractional contribution of non-star-formation sources to total Hα luminosity of a galaxy suggests a decreasing role of star formation as an ionizing source toward high-mass, high-B/T galaxies and bulge regions. This result indicates that the appearance of the galaxy integrated SFR–M * relation critically depends on their global properties (M *(global) and B/T) and relative abundances of various ionizing sources within the galaxies.

  14. A photometric study of the dwarf spheroidal galaxies Leo IV and Bootes II

    NASA Astrophysics Data System (ADS)

    Cheng, Haw

    A photometric study of the ultra-faint dwarf (UFD) galaxies Leo IV and Bootes II in the V and IC filters is here presented. The age of Leo IV relative to M92 were derived by fitting of Dartmouth isochrones, by a "standard" VHBTO method, and by the V HBTO method of VandenBerg et al. 2013. The age of Bootes II relative to M92 was derived by fitting of Dartmouth isochrones. Leo IV is found to be between 2 to 2.5 Gyr younger than M92 by these three methods. It is found to be predominantly old and metal poor and is well fit by isochrones of [Fe/H] = ---2.46 and [alpha/Fe] = 0.2 and 0.4. An age spread with a plausible value of ˜ 2 Gyr cannot be ruled out. A 10 Gyr old synthetic horizontal branch with [Fe/H] = ---1.70 and [alpha/Fe] of 0.2 is fit to Leo IV's red horizontal branch (RHB). The good fit of this model and its matching isochrone to Leo IV's CMD suggests that the RHB is real and not an observational artifact as proposed by Okamoto et al. 2012. Two RRab Lyraes previously observed by Moretti et al. 2009 were observed in Leo IV. One of the stars, V1, is observed to exhibit the Blazhko effect. No further RR Lyraes were uncovered in Leo IV. Comparison of the horizontal branch's observed V magnitude to the absolute magnitudes of the RR Lyraes yields a distance modulus of (m---M)0 = 21.01 +/- 0.07, in good agreement with previous studies. Leo IV's possible population of blue stragglers is found to show no signs of central concentration, though this study's sample and spatial coverage are too small for any detailed spatial distribution study. Bootes II's CMD is found to be consistent with that of a single age, mono-metallicity system. It is well fit by isochrones of [Fe/H] = ---1.79 and [alpha/Fe] = 0.2 and 0.4. Bootes II is found to be between 0.5 to 1.5 Gyr younger than M92. Distance was left as a free parameter in the fits. Bootes II is found to have distance modulus (m---M)0 lying between 18.02 to 18.15, in good agreement with previous studies. A single RRab Lyrae

  15. The Reliability of [c II] as a Star Formation Rate Indicator

    NASA Astrophysics Data System (ADS)

    De Looze, Ilse; Baes, Maarten; Fritz, Jacopo; Bendo, George J.; Cortese, Luca

    2011-08-01

    We present a calibration of the star formation rate (SFR) as a function of the [C II] 157.74 μ m luminosity for a sample of 24 star-forming galaxies in the nearby universe. In order to calibrate the SFR against the line luminosity, we rely on both GALEX FUV data, which is an ideal tracer of the unobscured star formation, and Spitzer MIPS 24 μ m, to probe the dust-enshrouded fraction of star formation. For this sample of normal star-forming galaxies, the [C II] luminosity correlates well with the star formation rate. However, the extension of this relation to more quiescent (Hα EW ≤ 10 Å) or ultra luminous galaxies (L TIR ≥ 1012 L⊙) should be handled with caution, since these objects show a non-linearity in the L [C II]-to-L FIR ratio as a function of L FIR (and thus, their star formation activity). Two possible scenarios can be invoked to explain the tight correlation between the [C II] emission and the star formation activity on a global galaxy-scale. The first interpretation could be that the [C II] emission from photo dissociation regions arises from the immediate surroundings of actively star-forming regions and contributes a more or less constant fraction on a global galaxy-scale. Alternatively, we consider the possibility that the [C II] emission is associated to the cold interstellar medium, which advocates an indirect link with the star formation activity in a galaxy through the Schmidt law.

  16. The growth of discs and bulges during hierarchical galaxy formation - II. Metallicity, stellar populations and dynamical evolution

    NASA Astrophysics Data System (ADS)

    Tonini, C.; Mutch, S. J.; Wyithe, J. S. B.; Croton, D. J.

    2017-03-01

    We investigate the properties of the stellar populations of model galaxies as a function of galaxy evolutionary history and angular momentum content. We use the new semi-analytic model presented in Tonini et al. This new model follows the angular momentum evolution of gas and stars, providing the base for a new star formation recipe, and treatment of the effects of mergers that depends on the central galaxy dynamical structure. We find that the new recipes have the effect of boosting the efficiency of the baryonic cycle in producing and recycling metals, as well as preventing minor mergers from diluting the metallicity of bulges and ellipticals. The model reproduces the stellar mass-stellar metallicity relation for galaxies above 1010 solar masses, including Brightest Cluster Galaxies. Model discs, galaxies dominated by instability-driven components, and merger-driven objects each stem from different evolutionary channels. These model galaxies therefore occupy different loci in the galaxy mass-size relation, which we find to be in accord with the ATLAS 3D classification of disc galaxies, fast rotators and slow rotators. We find that the stellar populations' properties depend on the galaxy evolutionary type, with more evolved stellar populations being part of systems that have lost or dissipated more angular momentum during their assembly history.

  17. Blue diffuse dwarf galaxies: a clearer picture

    NASA Astrophysics Data System (ADS)

    James, Bethan L.; Koposov, Sergey E.; Stark, Daniel P.; Belokurov, Vasily; Pettini, Max; Olszewski, Edward W.; McQuinn, Kristen B. W.

    2017-03-01

    The search for chemically unevolved galaxies remains prevalent in the nearby Universe, mostly because these systems provide excellent proxies for exploring in detail the physics of high-z systems. The most promising candidates are extremely metal-poor galaxies (XMPs), I.e. galaxies with <1/10 solar metallicity. However, due to the bright emission-line-based search criteria traditionally used to find XMPs, we may not be sampling the full XMP population. In 2014, we reoriented this search using only morphological properties and uncovered a population of ˜150 'blue diffuse dwarf (BDD) galaxies', and published a sub-sample of 12 BDD spectra. Here, we present optical spectroscopic observations of a larger sample of 51 BDDs, along with their Sloan Digital Sky Survey (SDSS) photometric properties. With our improved statistics, we use direct-method abundances to confirm that BDDs are chemically unevolved (7.43 < 12 + log(O/H) < 8.01), with ˜20 per cent of our sample classified as being XMP galaxies, and find that they are actively forming stars at rates of ˜1-33 × 10-2 M⊙ yr-1 in H II regions randomly embedded in a blue, low-surface-brightness continuum. Stellar masses are calculated from population synthesis models and estimated to be in the range log (M*/M⊙) ≃ 5-9. Unlike other low-metallicity star-forming galaxies, BDDs are in agreement with the mass-metallicity relation at low masses, suggesting that they are not accreting large amounts of pristine gas relative to their stellar mass. BDD galaxies appear to be a population of actively star-forming dwarf irregular (dIrr) galaxies which fall within the class of low-surface-brightness dIrr galaxies. Their ongoing star formation and irregular morphology make them excellent analogues for galaxies in the early Universe.

  18. First Detections of the [N II] 122 micron Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

    NASA Technical Reports Server (NTRS)

    Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

    2011-01-01

    We report the first detections of the [N II] 122 micron line from a high-redshift galaxy. The line was strongly (>6(sigma)) detected from SMMJ02399-0136, and H1413 + 117 (the Cloverleaf QSO) using the Redshift (zeta) and Early Universe Spectrometer on the Caltech Submillimeter Observatory. The lines from both sources are quite bright with line to far-infrared (FIR) continuum luminosity ratios that are approx.7.0 x 10(exp -4) (Cloverleaf) and 2.1 x 10(exo -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line to continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8%-17% of the molecUlar gas mass. The [O III]/[N II] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an active galactic nucleus (AGN). Using Our previous detection of the [O III] 88 micron line, the [O III]/[N II]line ratio for SMMJ02399-0136 indicates that the dominant source of the line emission is either stellar H II regions ionized by O9.5 stars, or the NLR of the AGN with ionization parameter log(U) = -3.3 to -4.0. A composite system, where 30%-50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82-like starbursts accounting for all of the FIR emission and 43% of the [N II]line. The remainder may come from the NLR. This war!< demonstrates the utility of the [N II] and [O III] lines in constraining properties of the ionized medium.

  19. VLA neutral hydrogen imaging of compact groups of galaxies. II - HCG 31, 44, and 79

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Williams, B.A.; Mcmahon, P.M.; Van gorkom, J.H.

    1991-06-01

    Neutral hydrogen images of three compact groups of galaxies are presented: HCG 31, 44, and 79. The images were obtained with the very large array (VLA), an on-line Hanning smoothing was applied to the data, and the H I spectral channel was isolated. The images were made on the Pipeline, and were produced by means of a method described by Gorkon and Ekers (1988). The images of HCG 44 are compared with earlier Arecibo observations. The H I emission in HCG 44 is discovered within the galaxies, whereas the emission in 31 and 79 can be found throughout the groupmore » in clouds that are larger than the galaxies. Evidence of a relationship between the compact groups is found in the H I data, and the groups are considered to be merging into a single object. Some of the groups are theorized to be young amorphous galaxies where the H I is still bound to individual galaxies, and which have just begun to condense from the intergalactic medium. The kinematics of the gas are shown to vary, and a common gaseous envelope contains the dwarf galaxies. 42 refs.« less

  20. Dynamical Models of Elliptical Galaxies in z = 0.5 Clusters. I. Data-Model Comparison and Evolution of Galaxy Rotation

    NASA Astrophysics Data System (ADS)

    van der Marel, Roeland P.; van Dokkum, Pieter G.

    2007-10-01

    We present spatially resolved stellar rotation velocity and velocity dispersion profiles from Keck/LRIS absorption-line spectra for 25 galaxies, mostly visually classified ellipticals, in three clusters at z~0.5. We interpret the kinematical data and HST photometry using oblate axisymmetric two-integral f(E,Lz) dynamical models based on the Jeans equations. This yields good fits, provided that the seeing and observational characteristics are carefully modeled. The fits yield for each galaxy the dynamical mass-to-light ratio (M/L) and a measure of the galaxy rotation rate. Paper II addresses the implied M/L evolution. Here we study the rotation-rate evolution by comparison to a sample of local elliptical galaxies of similar present-day luminosity. The brightest galaxies in the sample all rotate too slowly to account for their flattening, as is also observed at z=0. But the average rotation rate is higher at z~0.5 than locally. This may be due to a higher fraction of misclassified S0 galaxies (although this effect is insufficient to explain the observed strong evolution of the cluster S0 fraction with redshift). Alternatively, dry mergers between early-type galaxies may have decreased the average rotation rate over time. It is unclear whether such mergers are numerous enough in clusters to explain the observed trend quantitatively. Disk-disk mergers may affect the comparison through the so-called ``progenitor bias,'' but this cannot explain the direction of the observed rotation-rate evolution. Additional samples are needed to constrain possible environmental dependencies and cosmic variance in galaxy rotation rates. Either way, studies of the internal stellar dynamics of distant galaxies provide a valuable new approach for exploring galaxy evolution.

  1. Upper limits on the mass and luminosity of Population III-dominated galaxies

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Khochfar, Sadegh

    2017-05-01

    We here derive upper limits on the mass and luminosity of Population III (POPIII) dominated proto-galaxies based on the collapse of primordial gas under the effect of angular momentum loss via Lyα radiation drag and the gas accretion on to a galactic centre. Our model predicts that POPIII-dominated galaxies at z ˜ 7 are hosted by haloes with Mh ˜ 1.5 × 108-1.1 × 109 M⊙, that they have Lyα luminosities of LLyα ˜ 3.0 × 1042-2.1 × 1043 erg s- 1, stellar mass of Mstar ˜ 0.8 × 105-2.5 × 106 M⊙ and outflowing gas with velocities Vout ˜ 40 km s- 1 due to Lyα radiation pressure. We show that the POPIII galaxy candidate CR7 violates the derived limits on stellar mass and Lyα luminosity and thus is unlikely to be a POPIII galaxy. POPIII-dominated galaxies at z ˜ 7 have He II line emission that is ˜1-3 orders of magnitude lower than that of Lyα, they have high Lyα equivalent width of ≳ 300 Å and should be found close to bright star-forming galaxies. The He II 1640 Å line is in comfortable reach of next generation telescopes, like the James Webb Space Telescope (JWST) or Thirty Meter Telescope (TMT).

  2. Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 from the Radio to the Ultraviolet

    NASA Astrophysics Data System (ADS)

    Reines, Amy E.; Johnson, Kelsey E.; Goss, W. M.

    2008-06-01

    We present a multi-wavelength study of embedded massive clusters in the nearby (3.9 Mpc) starburst galaxy NGC 4449 in an effort to uncover the earliest phases of massive cluster evolution. By combining high-resolution imaging from the radio to the ultraviolet, we reveal these clusters to be in the process of emerging from their gaseous and dusty birth cocoons. We use Very Large Array (VLA) observations at centimeter wavelengths to identify young clusters surrounded by ultra-dense H II regions, detectable via their production of thermal free-free radio continuum. Ultraviolet, optical and infrared observations are obtained from the Hubble and Spitzer Space Telescope archives for comparison. We detect 39 compact radio sources toward NGC 4449 at 3.6 cm using the highest resolution (1farcs3) and sensitivity (~12 μJy) VLA image of the galaxy to date. We reliably identify 13 thermal radio sources and derive their physical properties using both nebular emission from the H II regions and spectral energy distribution fitting to the stellar continuum. These radio-detected clusters have ages lsim5 Myr and stellar masses of order 104 M sun. The measured extinctions are quite low: 12 of the 13 thermal radio sources have A V lsim 1.5, while the most obscured source has A V ≈ 4.3. By combining results from the nebular and stellar emission, we find an I-band excess that is anti-correlated with cluster age and an apparent mass-age correlation. Additionally, we find evidence that local processes such as supernovae and stellar winds likely play an important role in triggering the current bursts of star formation within NGC 4449.

  3. SPECTROSCOPY OF LUMINOUS COMPACT BLUE GALAXIES IN DISTANT CLUSTERS. II. PHYSICAL PROPERTIES OF dE PROGENITOR CANDIDATES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Crawford, S. M.; Wirth, Gregory D.; Bershady, M. A.

    2016-02-01

    Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M > 10{sup 15} M{sub ⊙}), intermediate redshift (0.5 < z < 0.9) galaxy clusters, we present their rest-frame properties including star formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size–luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs atmore » the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.« less

  4. Observational Searches for Star-Forming Galaxies at z > 6

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.

    2016-08-01

    Although the universe at redshifts greater than six represents only the first one billion years (< 10%) of cosmic time, the dense nature of the early universe led to vigorous galaxy formation and evolution activity which we are only now starting to piece together. Technological improvements have, over only the past decade, allowed large samples of galaxies at such high redshifts to be collected, providing a glimpse into the epoch of formation of the first stars and galaxies. A wide variety of observational techniques have led to the discovery of thousands of galaxy candidates at z > 6, with spectroscopically confirmed galaxies out to nearly z = 9. Using these large samples, we have begun to gain a physical insight into the processes inherent in galaxy evolution at early times. In this review, I will discuss (i) the selection techniques for finding distant galaxies, including a summary of previous and ongoing ground and space-based searches, and spectroscopic follow-up efforts, (ii) insights into galaxy evolution gleaned from measures such as the rest-frame ultraviolet luminosity function, the stellar mass function, and galaxy star-formation rates, and (iii) the effect of galaxies on their surrounding environment, including the chemical enrichment of the universe, and the reionisation of the intergalactic medium. Finally, I conclude with prospects for future observational study of the distant universe, using a bevy of new state-of-the-art facilities coming online over the next decade and beyond.

  5. Observational hints of radial migration in disc galaxies from CALIFA

    NASA Astrophysics Data System (ADS)

    Ruiz-Lara, T.; Pérez, I.; Florido, E.; Sánchez-Blázquez, P.; Méndez-Abreu, J.; Sánchez-Menguiano, L.; Sánchez, S. F.; Lyubenova, M.; Falcón-Barroso, J.; van de Ven, G.; Marino, R. A.; de Lorenzo-Cáceres, A.; Catalán-Torrecilla, C.; Costantin, L.; Bland-Hawthorn, J.; Galbany, L.; García-Benito, R.; Husemann, B.; Kehrig, C.; Márquez, I.; Mast, D.; Walcher, C. J.; Zibetti, S.; Ziegler, B.; Califa Team

    2017-07-01

    Context. According to numerical simulations, stars are not always kept at their birth galactocentric distances but they have a tendency to migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if radial migration is indeed important, galaxies with different surface brightness (SB) profiles must display differences in their stellar population properties. Aims: We investigate the role of radial migration in the light distribution and radial stellar content by comparing the inner colour, age, and metallicity gradients for galaxies with different SB profiles. We define these inner parts, avoiding the bulge and bar regions and up to around three disc scale lengths (type I, pure exponential) or the break radius (type II, downbending; type III, upbending). Methods: We analysed 214 spiral galaxies from the CALIFA survey covering different SB profiles. We made use of GASP2D and SDSS data to characterise the light distribution and obtain colour profiles of these spiral galaxies. The stellar age and metallicity profiles were computed using a methodology based on full-spectrum fitting techniques (pPXF, GANDALF, and STECKMAP) to the Integral Field Spectroscopic CALIFA data. Results: The distributions of the colour, stellar age, and stellar metallicity gradients in the inner parts for galaxies displaying different SB profiles are unalike as suggested by Kolmogorov-Smirnov and Anderson-Darling tests. We find a trend in which type II galaxies show the steepest profiles of all, type III show the shallowest, and type I display an intermediate behaviour. Conclusions: These results are consistent with a scenario in which radial migration is more efficient for type III galaxies than for type I systems, where type II galaxies present the lowest radial migration efficiency. In such a scenario, radial migration mixes the stellar content, thereby flattening the radial stellar properties and shaping different SB profiles. However

  6. Neutral hydrogen and optical properties of three amorphous galaxies

    NASA Technical Reports Server (NTRS)

    Hunter, Deidre A.; Woerden, Hugo Van; Gallagher, John S., III

    1994-01-01

    We present new interferometric H I and optical observations of three amorphous galaxies, systems with a smooth, high surface brightness but an asymmetrical distribution of light. All three galaxies are forming stars and have LMC-like emission-line ratios, low dust content, and high H I velocity dispersions. NGC 1140 has a boxy inner morphology with a hook off one corner. At low light levels unusual extensions of starlight are seen curving to the northwest and southeast. The galaxy contains a very luminous central star-forming region and a small chain of H II regions that coincide with the hook. The central H II region has broad H(alpha) velocity profiles full width at half maximum (FWHM) less than or equal to 140 km/s, and it is a radio continuum source. There is a rotating H I gas disk, 40 kpc in radius, at a position angle 51 deg from the optical major axis. The central gas ridge follows the chain of H II regions, and the H I peak is on the hook. The outer gas on the southeast side curves away from the H I major axis. The central gas density is high, and the surface density declines very slowly with radius. The rotation velocity yields a mass of 1 x 10(exp 11) solar mass at 3.3 Holmberg radii (R(sub H)). NGC 1800 has a hook that coincides with a large H II region, and an r(exp 1/4) luminosity distribution. There are numerous H II regions along the major axis and extraordinary filaments of ionized gas. Emanating from the major axis on either side of the galaxy are H(alpha) fingers approximately 750 pc long. About 2.3 kpc to the north is a web of filaments approximately 3 kpc in extent. H(alpha) profiles of H II regions and filaments are narrow. The H I gas disk has a position angle that is approximately 13 deg different from that of the optical axis. There are two peaks near the center, one of which is near the largest H II region. Beyond the Holmberg radius to the west is a 6 x 10(exp 6) solar mass H I cloud. Its velocity indicates a mass of approximately 6 x 10

  7. Very deep spectroscopy of the bright Saturn nebula NGC 7009 - II. Analysis of the rich optical recombination spectrum

    NASA Astrophysics Data System (ADS)

    Fang, X.; Liu, X.-W.

    2013-03-01

    In Paper I, we presented a deep, long-slit spectrum of the bright Saturn nebula NGC 7009. Numerous permitted lines emitted by the C+, N+, O+ and Ne+ ions were detected. Gaussian profile fitting to the spectrum yielded more than 1000 lines, the majority of which are optical recombination lines (ORLs) of heavy-element ions. In the current paper, we present a critical analysis of the rich optical recombination spectrum of NGC 7009, in the context of the bi-abundance nebular model proposed by Liu et al. Transitions from individual multiplets are checked carefully for potential blended lines. The observed relative intensities are compared with the theoretical predictions based on high-quality effective recombination coefficients, now available for the recombination line spectrum of a number of heavy-element ions. The possibility of plasma diagnostics using the ORLs of various heavy-element ions is discussed in detail. The line ratios that can be used to determine electron temperature are presented for each ion, although there is still a lack of adequate atomic data and some of the lines are still not detected in the spectrum of NGC 7009 due to weakness and/or line blending. Plasma diagnostics based on the N II and O II recombination spectra both yield electron temperatures close to 1000 K, which is lower than those derived from the collisionally excited line (CEL) ratios (e.g. the [O III] and [N II] nebular-to-auroral line ratios; see Paper I for details) by nearly one order of magnitude. The very low temperatures yielded by the O II and N II ORLs indicate that they originate from very cold regions. The C2+/H+, N2+/H+, O2+/H+ and Ne2+/H+ ionic abundance ratios derived from ORLs are consistently higher, by about a factor of 5, than the corresponding values derived from CELs. In calculating the ORL ionic abundance ratios, we have used the newly available high-quality effective recombination coefficients, and adopted an electron temperature of ˜1000 K, as given by the ORL

  8. The SELGIFS data challenge: generating synthetic observations of CALIFA galaxies from hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Guidi, G.; Casado, J.; Ascasibar, Y.; García-Benito, R.; Galbany, L.; Sánchez-Blázquez, P.; Sánchez, S. F.; Rosales-Ortega, F. F.; Scannapieco, C.

    2018-06-01

    In this work we present a set of synthetic observations that mimic the properties of the Integral Field Spectroscopy (IFS) survey CALIFA, generated using radiative transfer techniques applied to hydrodynamical simulations of galaxies in a cosmological context. The simulated spatially-resolved spectra include stellar and nebular emission, kinematic broadening of the lines, and dust extinction and scattering. The results of the radiative transfer simulations have been post-processed to reproduce the main properties of the CALIFA V500 and V1200 observational setups. The data has been further formatted to mimic the CALIFA survey in terms of field of view size, spectral range and sampling. We have included the effect of the spatial and spectral Point Spread Functions affecting CALIFA observations, and added detector noise after characterizing it on a sample of 367 galaxies. The simulated datacubes are suited to be analysed by the same algorithms used on real IFS data. In order to provide a benchmark to compare the results obtained applying IFS observational techniques to our synthetic datacubes, and test the calibration and accuracy of the analysis tools, we have computed the spatially-resolved properties of the simulations. Hence, we provide maps derived directly from the hydrodynamical snapshots or the noiseless spectra, in a way that is consistent with the values recovered by the observational analysis algorithms. Both the synthetic observations and the product datacubes are public and can be found in the collaboration website http://astro.ft.uam.es/selgifs/data_challenge/.

  9. The Rest-frame Optical Spectroscopic Properties of Lyalpha-emitters at Z~2.5: The Physical Origins of Strong Lyalpha Emission

    NASA Astrophysics Data System (ADS)

    Trainor, Ryan F.; Strom, Allison L.; Steidel, Charles C.; Rudie, Gwen C.

    2016-12-01

    We present the rest-frame optical spectroscopic properties of 60 faint (R AB ˜ 27; L ˜ 0.1 L *) Lyα-selected galaxies (LAEs) at z ≈ 2.56. These LAEs also have rest-UV spectra of their Lyα emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Lyα photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuum-selected galaxies selected at z ≈ 2-3. In particular, the LAEs have extremely high [O III] λ5008/Hβ ratios (log([O III]/Hβ) ˜ 0.8) and low [N II] λ6585/Hα ratios (log([N II]/Hα) < 1.15). Coupled with a detection of the [O III] λ4364 auroral line, these measurements indicate that the star-forming regions in faint LAEs are characterized by high electron temperatures (T e ≈ 1.8 × 104 K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z neb ≈ 0.22Z ⊙), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9-7.4 (Z neb ≈ 0.02-0.05Z ⊙). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionization-era galaxies. Furthermore, we investigate the physical trends accompanying Lyα emission across the largest current sample of combined Lyα and rest-optical galaxy spectroscopy, including both the 60 KBSS-Lyα LAEs and 368 more luminous galaxies at similar redshifts. We find that the net Lyα emissivity (parameterized by the Lyα equivalent width) is

  10. THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LY α -EMITTERS AT z  ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LY α EMISSION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Trainor, Ryan F.; Strom, Allison L.; Steidel, Charles C.

    We present the rest-frame optical spectroscopic properties of 60 faint ( R {sub AB} ∼ 27; L ∼ 0.1 L {sub *}) Ly α -selected galaxies (LAEs) at z  ≈ 2.56. These LAEs also have rest-UV spectra of their Ly α emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Ly α photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuum-selected galaxies selected at z  ≈ 2–3. In particular, the LAEs have extremely high [O iii]more » λ 5008/H β ratios (log([O iii]/H β ) ∼ 0.8) and low [N ii] λ 6585/H α ratios (log([N ii]/H α ) < 1.15). Coupled with a detection of the [O iii] λ 4364 auroral line, these measurements indicate that the star-forming regions in faint LAEs are characterized by high electron temperatures (T{sub e} ≈ 1.8 × 10{sup 4} K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z{sub neb} ≈ 0.22 Z {sub ⊙}), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9–7.4 (Z {sub neb} ≈ 0.02–0.05 Z{sub ⊙}). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionization-era galaxies. Furthermore, we investigate the physical trends accompanying Ly α emission across the largest current sample of combined Ly α and rest-optical galaxy spectroscopy, including both the 60 KBSS-Ly α LAEs and 368 more luminous galaxies at similar

  11. ON THE USE OF THE INDEX N2 TO DERIVE THE METALLICITY IN METAL-POOR GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Morales-Luis, A. B.; Almeida, J. Sánchez; Muñoz-Tuñón, C.

    2014-12-20

    The N2 index ([N II] λ6584/Hα) is used to determine emission line galaxy metallicities at all redshifts, including high redshift, where galaxies tend to be metal-poor. The initial aim of this work was to improve the calibrations used to infer oxygen abundance from N2 by employing updated low-metallicity galaxy databases. We compare N2 and the metallicity determined using the direct method for the set of extremely metal-poor galaxies compiled by Morales-Luis et al. To our surprise, the oxygen abundance presents a tendency to be constant with N2, with a very large scatter. Consequently, we find that the existing N2 calibrators overestimatemore » the oxygen abundance for most low-metallicity galaxies, and can therefore only be used to set upper limits to the true metallicity in low-metallicity galaxies. An explicit expression for this limit is given. In addition, we try to explain the observed scatter using photoionization models. It is mostly due to the different evolutionary state of the H II regions producing the emission lines, but it also arises due to differences in N/O among the galaxies.« less

  12. THE SPECTRALLY RESOLVED Lyα EMISSION OF THREE Lyα-SELECTED FIELD GALAXIES AT z ∼ 2.4 FROM THE HETDEX PILOT SURVEY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chonis, Taylor S.; Finkelstein, Steven L.; Gebhardt, Karl

    2013-10-01

    We present new results on the spectrally resolved Lyα emission of three Lyα-emitting field galaxies at z ∼ 2.4 with high Lyα equivalent width (>100 Å) and Lyα luminosity (∼10{sup 43} erg s{sup –1}). At 120 km s{sup –1} (FWHM) spectral resolution, the prominent double-peaked Lyα profile straddles the systemic velocity, where the velocity zero point is determined from spectroscopy of the galaxies' rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s{sup –1} while the average total separation between the redshifted and main blueshifted emissionmore » components is 380 km s{sup –1}. These measurements are a factor of ∼2 smaller than for UV-continuum-selected galaxies that show Lyα in emission with lower Lyα equivalent widths. We compare our Lyα spectra to the predicted line profiles of a spherical 'expanding shell' Lyα radiative transfer grid that models large-scale galaxy outflows. Specifically, blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by ∼1000 km s{sup –1}) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lyα line profile, we caution against equating the observed Lyα velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lyα velocity offset is a convoluted function of several degenerate parameters. Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging, we find that galaxy-galaxy interactions may play an important role in inducing a starburst that results in copious Lyα emission as well as perturbing the gas distribution and velocity field, both of which have strong influence over the Lyα emission line profile.« less

  13. [C II] 158 μm EMISSION AS A STAR FORMATION TRACER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Herrera-Camus, R.; Bolatto, A. D.; Wolfire, M. G.

    2015-02-10

    The [C II] 157.74 μm transition is the dominant coolant of the neutral interstellar gas, and has great potential as a star formation rate (SFR) tracer. Using the Herschel KINGFISH sample of 46 nearby galaxies, we investigate the relation of [C II] surface brightness and luminosity with SFR. We conclude that [C II] can be used for measurements of SFR on both global and kiloparsec scales in normal star-forming galaxies in the absence of strong active galactic nuclei (AGNs). The uncertainty of the Σ{sub [C} {sub II]} – Σ{sub SFR} calibration is ±0.21 dex. The main source of scatter in themore » correlation is associated with regions that exhibit warm IR colors, and we provide an adjustment based on IR color that reduces the scatter. We show that the color-adjusted Σ{sub [C} {sub II]} – Σ{sub SFR} correlation is valid over almost five orders of magnitude in Σ{sub SFR}, holding for both normal star-forming galaxies and non-AGN luminous infrared galaxies. Using [C II] luminosity instead of surface brightness to estimate SFR suffers from worse systematics, frequently underpredicting SFR in luminous infrared galaxies even after IR color adjustment (although this depends on the SFR measure employed). We suspect that surface brightness relations are better behaved than the luminosity relations because the former are more closely related to the local far-UV field strength, most likely the main parameter controlling the efficiency of the conversion of far-UV radiation into gas heating. A simple model based on Starburst99 population-synthesis code to connect SFR to [C II] finds that heating efficiencies are 1%-3% in normal galaxies.« less

  14. The concerted impact of galaxies and QSOs on the ionization and thermal state of the intergalactic medium

    NASA Astrophysics Data System (ADS)

    Kakiichi, Koki; Graziani, Luca; Ciardi, Benedetta; Meiksin, Avery; Compostella, Michele; Eide, Marius B.; Zaroubi, Saleem

    2017-07-01

    We present a detailed analysis of the ionization and thermal structure of the intergalactic medium (IGM) around a high-redshift (z = 10) QSO, using a large suite of cosmological, multifrequency radiative transfer simulations, exploring the contribution from galaxies as well as the QSO, and the effect of X-rays and secondary ionization. We show that in high-z QSO environments both the central QSO and the surrounding galaxies concertedly control the reionization morphology of hydrogen and helium and have a non-linear impact on the thermal structure of the IGM. A QSO imprints a distinctive morphology on H II regions if its total ionizing photon budget exceeds that of the surrounding galaxies since the onset of hydrogen reionization; otherwise, the morphology shows little difference from that of H II regions produced only by galaxies. In addition, the spectral shape of the collective radiation field from galaxies and QSOs controls the thickness of the I-fronts. While a UV-obscured QSO can broaden the I-front, the contribution from other UV sources, either galaxies or unobscured QSOs, is sufficient to maintain a sharp I-front. X-ray photons from the QSO are responsible for a prominent extended tail of partial ionization ahead of the I-front. QSOs leave a unique imprint on the morphology of He II/He III regions. We suggest that, while the physical state of the IGM is modified by QSOs, the most direct test to understand the role of galaxies and QSOs during reionization is to perform galaxy surveys in a region of sky imaged by 21 cm tomography.

  15. Exploring the Surface Brightness Breaks and Star Formation in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Malko, Bradley Ann; Hunter, Deidre Ann

    2018-06-01

    Stellar surface brightness profiles of both spirals and dwarf irregular galaxies often show breaks in which the exponential fall-off abruptly changes slope. Most often the profile is down-bending (Type II) in the outer disk, but sometimes it is up-bending (Type III). Stellar disks extend a long ways beyond the profile breaks, but we do not understand what happens physically at the breaks. To explore this we are examining the star formation activity, as traced with FUV emission, interior to the break compared to that exterior to the break in both dwarf irregulars and spiral galaxies. We present the results for the spiral galaxy NGC 2500 and compare it to the LITTLE THINGS dwarf irregular galaxies.

  16. A high-resolution image of the inner shell of the P Cygni nebula in the infrared [Fe II] line

    NASA Astrophysics Data System (ADS)

    Arcidiacono, C.; Ragazzoni, R.; Morossi, C.; Franchini, M.; di Marcantonio, P.; Kulesa, C.; McCarthy, D.; Briguglio, R.; Xompero, M.; Busoni, L.; Quirós-Pacheco, F.; Pinna, E.; Boutsia, K.; Paris, D.

    2014-09-01

    Using the adaptive optics system of the Large Binocular Telescope, we have obtained near-infrared camera PISCES images of the inner shell of the nebula around the luminous blue variable star P Cygni in the [Fe II] emission line at 1.6435 μm. We have combined the images in order to cover a field of view of about 20 arcsec around P Cygni, thus providing the high-resolution (0.08 arcsec) two-dimensional spatial distribution of the inner shell of the P Cygni nebula in [Fe II]. We have identified several nebular emission regions that are characterized by a signal-to-noise ratio > 3. A comparison of our results with those available in the literature shows full consistency with the findings of Smith & Hartigan, which are based on radial velocity measurements, and relatively good agreement with the extension of emission nebula in [N II] λ6584 found by Barlow et al. We have clearly also detected extended emission inside the radial distance R = 7.8 arcsec and outside R = 9.7 arcsec, which are the nebular boundaries proposed by Smith & Hartigan. New complementary spectroscopic observations are planned in order to measure radial velocities and to derive the three-dimensional distribution of the P Cygni nebula.

  17. C III] Emission in Star-forming Galaxies at z ∼ 1

    NASA Astrophysics Data System (ADS)

    Du, Xinnan; Shapley, Alice E.; Martin, Crystal L.; Coil, Alison L.

    2017-03-01

    The C III]λλ1907, 1909 rest-frame UV emission doublet has recently been detected in galaxies during the epoch of reionization (z > 6), with a high equivalent width (EW; 10 Å, rest frame). Currently, it is possible to obtain much more detailed information for star-forming galaxies at significantly lower redshift. Accordingly, studies of their far-UV spectra are useful for understanding the factors modulating the strength of C III] emission. We present the first statistical sample of C III] emission measurements in star-forming galaxies at z ∼ 1. Our sample is drawn from the DEEP2 survey and spans the redshifts 0.64 ≤slant z ≤slant 1.35 (< z> =1.08). We find that the median EW of individual C III] detections in our sample (1.30 Å) is much smaller than the typical value observed thus far at z > 6. Furthermore, out of 184 galaxies with coverage of C III], only 40 have significant detections. Galaxies with individual C III] detections have bluer colors and lower luminosities on average than those without, implying that strong C III] emitters are in general young and low-mass galaxies without significant dust extinction. Using stacked spectra, we further investigate how C III] strength correlates with multiple galaxy properties (M B , U ‑ B, M *, star formation rate, specific star formation rate) and rest-frame near-UV (Fe II* and Mg II) and optical ([O III] and Hβ) emission line strengths. These results provide a detailed picture of the physical environment in star-forming galaxies at z ∼ 1, and motivate future observations of strong C III] emitters at similar redshifts.

  18. R-process enrichment from a single event in an ancient dwarf galaxy.

    PubMed

    Ji, Alexander P; Frebel, Anna; Chiti, Anirudh; Simon, Joshua D

    2016-03-31

    Elements heavier than zinc are synthesized through the rapid (r) and slow (s) neutron-capture processes. The main site of production of the r-process elements (such as europium) has been debated for nearly 60 years. Initial studies of trends in chemical abundances in old Milky Way halo stars suggested that these elements are produced continually, in sites such as core-collapse supernovae. But evidence from the local Universe favours the idea that r-process production occurs mainly during rare events, such as neutron star mergers. The appearance of a plateau of europium abundance in some dwarf spheroidal galaxies has been suggested as evidence for rare r-process enrichment in the early Universe, but only under the assumption that no gas accretes into those dwarf galaxies; gas accretion favours continual r-process enrichment in these systems. Furthermore, the universal r-process pattern has not been cleanly identified in dwarf spheroidals. The smaller, chemically simpler, and more ancient ultrafaint dwarf galaxies assembled shortly after the first stars formed, and are ideal systems with which to study nucleosynthesis events such as the r-process. Reticulum II is one such galaxy. The abundances of non-neutron-capture elements in this galaxy (and others like it) are similar to those in other old stars. Here, we report that seven of the nine brightest stars in Reticulum II, observed with high-resolution spectroscopy, show strong enhancements in heavy neutron-capture elements, with abundances that follow the universal r-process pattern beyond barium. The enhancement seen in this 'r-process galaxy' is two to three orders of magnitude higher than that detected in any other ultrafaint dwarf galaxy. This implies that a single, rare event produced the r-process material in Reticulum II. The r-process yield and event rate are incompatible with the source being ordinary core-collapse supernovae, but consistent with other possible sources, such as neutron star mergers.

  19. Probing the Baryon Cycle of Galaxies with SPICA Mid- and Far-Infrared Observations

    NASA Astrophysics Data System (ADS)

    van der Tak, F. F. S.; Madden, S. C.; Roelfsema, P.; Armus, L.; Baes, M.; Bernard-Salas, J.; Bolatto, A.; Bontemps, S.; Bot, C.; Bradford, C. M.; Braine, J.; Ciesla, L.; Clements, D.; Cormier, D.; Fernández-Ontiveros, J. A.; Galliano, F.; Giard, M.; Gomez, H.; González-Alfonso, E.; Herpin, F.; Johnstone, D.; Jones, A.; Kaneda, H.; Kemper, F.; Lebouteiller, V.; De Looze, I.; Matsuura, M.; Nakagawa, T.; Onaka, T.; Pérez-González, P.; Shipman, R.; Spinoglio, L.

    2018-01-01

    The SPICA mid- and far-infrared telescope will address fundamental issues in our understanding of star formation and ISM physics in galaxies. A particular hallmark of SPICA is the outstanding sensitivity enabled by the cold telescope, optimised detectors, and wide instantaneous bandwidth throughout the mid- and far-infrared. The spectroscopic, imaging, and polarimetric observations that SPICA will be able to collect will help in clarifying the complex physical mechanisms which underlie the baryon cycle of galaxies. In particular, (i) the access to a large suite of atomic and ionic fine-structure lines for large samples of galaxies will shed light on the origin of the observed spread in star-formation rates within and between galaxies, (ii) observations of HD rotational lines (out to 10 Mpc) and fine structure lines such as [C ii] 158 μm (out to 100 Mpc) will clarify the main reservoirs of interstellar matter in galaxies, including phases where CO does not emit, (iii) far-infrared spectroscopy of dust and ice features will address uncertainties in the mass and composition of dust in galaxies, and the contributions of supernovae to the interstellar dust budget will be quantified by photometry and monitoring of supernova remnants in nearby galaxies, (iv) observations of far-infrared cooling lines such as [O i] 63 μm from star-forming molecular clouds in our Galaxy will evaluate the importance of shocks to dissipate turbulent energy. The paper concludes with requirements for the telescope and instruments, and recommendations for the observing strategy.

  20. Color Profile Trends of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Herrmann, Kimberly A.; LITTLE THINGS Team

    2012-01-01

    Radial stellar surface brightness profiles of spiral galaxies can be classified into three types: (I) single exponential, (II) truncated: the light falls off with one exponential out to a break radius and then falls off more steeply, and (III) anti-truncated: the light falls off with one exponential out to a break radius and then falls off less steeply. Stellar surface brightness profile breaks are also found in dwarf disk galaxies, but with an additional category: (FI) flat-inside: the light is roughly constant or increasing and then falls off beyond a break. Additionally, Bakos, Trujillo, & Pohlen (2008) showed that for spirals, each profile type has a characteristic color trend with respect to the break location. Furthermore, color trends reveal information about possible stellar population changes at the breaks. Here we show color trends for the four profile types from a large multi-wavelength photometric study of dwarf disk galaxies (the 141 dwarf parent sample of the LITTLE THINGS galaxies). We explore the similarities and differences between spirals and dwarfs and also between different colors. We gratefully acknowledge funding for this research from the National Science Foundation (AST-0707563).

  1. Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization

    NASA Astrophysics Data System (ADS)

    Rodríguez-Baras, M.; Díaz, A. I.; Rosales-Ortega, F. F.; Sánchez, S. F.

    2018-01-01

    Context. The knowledge of abundance distributions is central to understanding the formation and evolution of galaxies. Most of the relations employed for the derivation of gas abundances have so far been derived from observations of outer disk H ii regions, despite the known differences between inner and outer regions. Aims: Using integral field spectroscopy (IFS) observations we aim to perform a systematic study and comparison of two inner and outer H ii regions samples. The spatial resolution of the IFS, the number of objects and the homogeneity and coherence of the observations allow a complete characterization of the main observational properties and differences of the regions. Methods: We analyzed a sample of 725 inner H ii regions and a sample of 671 outer H ii regions, all of them detected and extracted from the observations of a sample of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey. Results: We find that inner H ii regions show smaller equivalent widths, greater extinction and luminosities, along with greater values of [N ii] λ6583/Hα and [O ii] λ3727/[O iii] λ5007 emission-line ratios, indicating higher metallicities and lower ionization parameters. Inner regions have also redder colors and higher photometric and ionizing masses, although MionMphot is slighty higher for the outer regions. Conclusions: This work shows important observational differences between inner and outer H ii regions in star forming galaxies not previously studied in detail. These differences indicate that inner regions have more evolved stellar populations and are in a later evolution state with respect to outer regions, which goes in line with the inside-out galaxy formation paradigm. Table 4 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A102

  2. Atomic Data for Nebular Abundance Determinations: Photoionization and Recombination Properties of Xenon Ions

    NASA Astrophysics Data System (ADS)

    Sterling, Nicholas C.; Kerlin, Austin B.

    2016-01-01

    We present preliminary results of a study of the photoionization (PI) and recombination properties of low-charge Xe ions. The abundances of neutron(n)-capture elements (atomic number Z > 30) are of interest in planetary nebulae (PNe) since they can be enriched by slow n-capture nucleosynthesis (the ``s-process'') in the progenitor asymptotic giant branch (AGB) stars. Xe is particularly valuable, because it is the most widely-observed ``heavy-s'' species (Z > 40) in PNe. Its abundance relative to lighter n-capture elements can be used to determine s-process neutron exposures, and constrain s-process enrichment patterns as a function of progenitor metallicity. Using the atomic structure code AUTOSTRUCTURE (Badnell 2011, Comp. Phys. Comm., 182, 1528), we have computed multi-configuration Breit-Pauli distorted-wave PI cross sections and radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for neutral through six-times ionized Xe, data which are critically needed for accurate Xe abundance determinations in ionized nebulae. We find good agreement between our computed direct PI cross sections and experimental measurements. Internal uncertainties are estimated for our calculations by using three different configuration interaction expansions for each ion, and by testing the sensitivity of our results to the radial orbital scaling parameters. As found for other n-capture elements (Sterling & Witthoeft 2011, A&A, 529, A147; Sterling 2011, A&A, 533, A62), DR is the dominant recombination mechanism for Xe ions at nebular temperatures (~104 K). Following Sterling et al. (2015, ApJS, 218, 25), these data will be added to nebular modeling codes to compute ionization correction factors for unobserved Xe ions in PNe, which will enable elemental Xe abundances to be determined with much higher accuracy than is currently possible. This work is supported by NSF award AST-1412928.

  3. A dwarf galaxy's transformation and a massive galaxy's edge: detailed modeling of the extended stream in NGC1097

    NASA Astrophysics Data System (ADS)

    Cristiano Amorisco, Nicola; Martinez-Delgado, David

    2015-08-01

    Low surface brightness tidal features around massive galaxies are the smoking gun of hierarchical galaxy formation. These debris are informative of: (i) the evolutionary struggles of the progenitor dwarf galaxies, transformed and partially destroyed by the tides; (ii) the formation history of the massive host, its halo populations and the structure of its dark matter halo. However, extracting reliable measurements of the progenitor’s initial mass, infall time, host halo mass and density profile has so far been difficult, as the parameter space is too wide to explore with N-body simulations.We use new deep imaging data of the extended, X shaped stream in NGC1097 [1,2] and a new dynamical technique to quantitatively reconstruct: (i) the density profile of the massive spiral host (inferred virial mass M200=1012.25±0.1 M⊙) ; and (ii) the dramatic evolution of the progenitor galaxy; by modeling its stream within a fully statistical framework. I will show that the current location of the remnant coincides with a nucleated dwarf Spheroidal, with a luminosity of ~3.3x106LV,⊙ [3], and a predicted total mass of M(<0.45±0.2 kpc)=107.8±0.6 M⊙. This is the result of a strong transformation: at its first interaction with the host, 4.4±0.4 Gyr and three pericentric passages ago, the progenitor was over two orders of magnitude more massive, with Mtot(3.2±0.7 kpc)=1010.4±0.2 M⊙. Its orbit has a pericenter of a few kpc, but reaches out to 150±12 kpc. In this range the stream’s morphology allows us to see the total density slope of the host bending and steepening towards large radii. For the first time in a single galaxy (rather than on stacked data), both central and outer slope are constrained by observations and can be compared to LCDM expectations [4]. Finally, I will discuss prospects of applying this technique to more known streams, to map the structure of a wider sample of galaxy haloes and unveil the evolutionary histories of more individual dwarf galaxies

  4. Direct Measurement of the Supernova Rate in Starburst Galaxies

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse D.; Temi, Pasquale; Rank, David; DeVincenzi, Donald L. (Technical Monitor)

    1999-01-01

    Supernovae play a key role in the dynamics, structure, and chemical evolution of galaxies. The massive stars that end their lives as supernovae live for short times. Many are still associated with dusty star formation regions when they explode, making them difficult to observe at visible wavelengths. In active star forming regions (galactic nuclei and starburst regions), dust extintion is especially severe. Thus, determining the supernova rate in the active star forming regions of galaxies, where the supernova rate can be one or two orders of magnitude higher than the average, has proven to be difficult. From observations of SN1987A, we know that the [NiII] 6.63 micron emission line was the strongest line in the infrared spectrum for a period of a year and a half after the explosion. Since dust extintion is much less at 6.63 pm than at visible wavelengths (A(sub 6.63)/A(sub V) = 0.025), the NiII line can be used as a sensitive probe for the detection of recent supernovae. We have observed a sample of starburst galaxies at 6.63 micron using ISOCAM to search for the NiII emission line characteristic of recent supernovae. We did not detect any NiII line emission brighter than a 5sigma limit of 5 mJy. We can set upper limits to the supernova rate in our sample, scaled to the rate in M82, of less than 0.3 per year at the 90% confidence level using Bayesian methods. Assuming that a supernova would have a NiII with the same luminosity as observed in SN1987A, we find less than 0.09 and 0.15 per year at the 50% and 67% confidence levels. These rates are somewhat less if a more normal type II supernovae has a NiII line luminosity greater than the line in SN1987A.

  5. Low-Surface-Brightness Galaxies: Hidden Galaxies Revealed

    NASA Astrophysics Data System (ADS)

    Bothun, G.; Impey, C.; McGaugh, S.

    1997-07-01

    In twenty years, low surface brightness (LSB) galaxies have evolved from being an idiosyncratic notion to being one of the major baryonic repositories in the Universe. The story of their discovery and the characterization of their properties is told here. Their recovery from the noise of the night sky background is a strong testament to the severity of surface brightness selection effects. LSB galaxies have a number of remarkable properties which distinguish them from the more familiar Hubble Sequence of spirals. The two most important are 1) they evolve at a significantly slower rate and may well experience star formation outside of the molecular cloud environment, 2) they are embedded in dark matter halos which are of lower density and more extended than the halos around high surface brightness (HSB) disk galaxies. Compared to HSB disks, LSB disks are strongly dark matter dominated at all radii and show a systematic increase in $M/L$ with decreasing central surface brightness. In addition, the recognition that large numbers of LSB galaxies actually exist has changed the form of the galaxy luminosity function and has clearly increased the space density of galaxies at z =0. Recent CCD surveys have uncovered a population of red LSB disks that may be related to the excess of faint blue galaxies detected at moderate redshifts. LSB galaxies offer us a new window into galaxy evolution and formation which is every bit as important as those processes which have produced easy to detect galaxies. Indeed, the apparent youth of some LSB galaxies suggest that galaxy formation is a greatly extended process. While the discovery of LSB galaxies have lead to new insights, it remains unwise to presume that we now have a representative sample which encompasses all galaxy types and forms. (SECTION: Invited Review Paper)

  6. ARE SOME MILKY WAY GLOBULAR CLUSTERS HOSTED BY UNDISCOVERED GALAXIES?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zaritsky, Dennis; Crnojević, Denija; Sand, David J., E-mail: dennis.zaritsky@gmail.com

    2016-07-20

    The confirmation of a globular cluster (GC) in the recently discovered ultrafaint galaxy Eridanus II (Eri II) motivated us to examine the question posed in the title. After estimating the halo mass of Eri II using a published stellar mass—halo mass relation, the one GC in this galaxy supports extending the relationship between the number of GCs hosted by a galaxy and the galaxy’s total mass about two orders of magnitude in stellar mass below the previous limit. For this empirically determined specific frequency of between 0.06 and 0.39 GCs per 10{sup 9} M {sub ⊙} of total mass, themore » surviving Milky Way (MW) subhalos with masses smaller than 10{sup 10} M {sub ⊙} could host as many as 5–31 GCs, broadly consistent with the actual population of outer halo MW GCs, although matching the radial distribution in detail remains a challenge. Using a subhalo mass function from published high-resolution numerical simulations and a Poissonian model for populating those halos with the aforementioned empirically constrained frequency, we find that about 90% of these GCs lie in lower-mass subhalos than that of Eri II. From what we know about the stellar mass–halo mass function, the subhalo mass function, and the mass-normalized GC specific frequency, we conclude that some of the MW’s outer halo GCs are likely to be hosted by undetected subhalos with extremely modest stellar populations.« less

  7. SLUG - stochastically lighting up galaxies - III. A suite of tools for simulated photometry, spectroscopy, and Bayesian inference with stochastic stellar populations

    NASA Astrophysics Data System (ADS)

    Krumholz, Mark R.; Fumagalli, Michele; da Silva, Robert L.; Rendahl, Theodore; Parra, Jonathan

    2015-09-01

    Stellar population synthesis techniques for predicting the observable light emitted by a stellar population have extensive applications in numerous areas of astronomy. However, accurate predictions for small populations of young stars, such as those found in individual star clusters, star-forming dwarf galaxies, and small segments of spiral galaxies, require that the population be treated stochastically. Conversely, accurate deductions of the properties of such objects also require consideration of stochasticity. Here we describe a comprehensive suite of modular, open-source software tools for tackling these related problems. These include the following: a greatly-enhanced version of the SLUG code introduced by da Silva et al., which computes spectra and photometry for stochastically or deterministically sampled stellar populations with nearly arbitrary star formation histories, clustering properties, and initial mass functions; CLOUDY_SLUG, a tool that automatically couples SLUG-computed spectra with the CLOUDY radiative transfer code in order to predict stochastic nebular emission; BAYESPHOT, a general-purpose tool for performing Bayesian inference on the physical properties of stellar systems based on unresolved photometry; and CLUSTER_SLUG and SFR_SLUG, a pair of tools that use BAYESPHOT on a library of SLUG models to compute the mass, age, and extinction of mono-age star clusters, and the star formation rate of galaxies, respectively. The latter two tools make use of an extensive library of pre-computed stellar population models, which are included in the software. The complete package is available at http://www.slugsps.com.

  8. Dust Attenuation and H(alpha) Star Formation Rates of Z Approx. 0.5 Galaxies

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Malkan, Matthew A.; Kashikawa, Nobunari; Ota, Kazuaki; Shimasaku, Kazuhiro; Iye, Masanori; Currie, Thayne

    2012-01-01

    Using deep narrow-band and broad-band imaging, we identify 401 z approximately 0.40 and 249 z approximately 0.49 H-alpha line-emitting galaxies in the Subaru Deep Field. Compared to other H-alpha surveys at similar redshifts, our samples are unique since they probe lower H-alpha luminosities, are augmented with multi-wavelength (rest-frame 1000AA--1.5 microns) coverage, and a large fraction (20%) of our samples has already been spectroscopically confirmed. Our spectra allow us to measure the Balmer decrement for nearly 60 galaxies with H-beta detected above 5-sigma. The Balmer decrements indicate an average extinction of A(H-alpha)=0.7(uparrow){+1.4}_{-0.7} mag. We find that the Balmer decrement systematically increases with higher H-alpha luminosities and with larger stellar masses, in agreement with previous studies with sparser samples. We find that the SFRs estimated from modeling the spectral energy distribution (SED) is reliable---we derived an "intrinsic" H-alpha luminosity which is then reddened assuming the color excess from SED modeling. The SED-predicted H-alpha luminosity agrees with H-alpha narrow-band measurements over 3 dex (rms of 0.25 dex). We then use the SED SFRs to test different statistically-based dust corrections for H-alpha and find that adopting one magnitude of extinction is inappropriate: galaxies with lower luminosities are less reddened. We find that the luminosity-dependent dust correction of Hopkins et al. yields consistent results over 3 dex (rms of 0.3 dex). Our comparisons are only possible by assuming that stellar reddening is roughly half of nebular reddening. The strong correspondence argue that with SED modeling, we can derive reliable intrinsic SFRs even in the absence of H-alpha measurements at z approximately 0.5.

  9. Atlas of Galaxies Useful for Measuring the Cosmological Distance Scale

    NASA Technical Reports Server (NTRS)

    Sandage, Allan; Bedke, John

    1988-01-01

    A critical first step in determining distances to galaxies is to measure some property of primary objects such as stars of specific types, H II regions, and supernovae remnants that are resolved out of the general galactic star content. With the completion of the Mount Wilson/Palomar/Las Campanas survey of bright galaxies in 1985, excellent large-scale photographs of the complete Shapley-Ames sample were on hand. Most of the galaxies useful for distance scale calibration are in this collection. This atlas contains photographs of 322 galaxies including the majority of all Shapley-Ames bright galaxies, plus cluster members in the Virgo Cluster core that might be usefully resolved by the Hubble Space Telescope (HST). Because of crowding and high background-disk surface brightness, the choice of field position is crucial for programs involving resolution of particular galaxies into stars. The purpose of this atlas is to facilitate this choice. Enough information is given herein (coordinates of the galaxy centers and the scale of the photography) to allow optimum placement of the HST wide-field planetary camera format of approximately 150 arc-seconds on a side.

  10. How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos

    NASA Astrophysics Data System (ADS)

    Tumlinson, Jason

    2009-07-01

    optical spectra of the QSOs to measure cold gas with Mg II, and optical spectra of the galaxies to measure SFRs and to look for outflows. In addition to our other science goals, these observations will help place the Milky Way's population of multiphase, accreting High Velocity Clouds {HVCs} into a global context by identifying analogous structures around other galaxies. Our program is designed to make optimal use of the unique capabilities of COS to address our science goals and also generate a rich dataset of other absorption-line systems along a significant total pathlength through the IGM {Delta z 20}.

  11. Emission-line galaxies in the third list of the Case Low-Dispersion Northern Sky Survey

    NASA Technical Reports Server (NTRS)

    Weistrop, Donna; Downes, Ronald A.

    1991-01-01

    Observations of 47 galaxies in the third Case list are reported. Thirty-five of the galaxies in the sample were selected for the presence of emission lines on the objective prism plates. At the higher spectral dispersion of the data, significant line emission was found in 46 of the 47 galaxies. Twenty-six galaxies are found to be undergoing significant bursts of star formation. Ten additional galaxies may be starburst galaxies with low-excitation spectra. Two galaxies are probably type Seyfert 2. The most distant object, CG 200, at a redshift of 0.144, has a strong broad H-alpha emission line, and is probably a Seyfert 1. Seventeen of the galaxies have been detected by IRAS. Eight of the IRAS galaxies have H-II-region-type spectra and eight have low-ionization starburst spectra. The galaxies represent a mixture of types, ranging from intrinsically faint dwarf galaxies with Mb equalling -16 mag, to powerful galaxies with MB equalling -23 mag. Galaxies CG 234 and CG 235 are interacting, as are galaxies CG 269 and CG 270.

  12. Galaxy bias from galaxy-galaxy lensing in the DES Science Verification Data

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Prat, J.; et al.

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited (more » $$i_{AB} < 22.5$$) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias $b$ and cross-correlation coefficient between the galaxy and dark matter overdensity fields $r$ in each bin, using scales above 4 Mpc/$h$ comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin ($$z\\sim0.3$$), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systematic effects. We measure $$b\\cdot r$$ to be $$0.87\\pm 0.11$$, $$1.12 \\pm 0.16$$ and $$1.24\\pm 0.23$$, respectively for the three redshift bins of width $$\\Delta z = 0.2$$ in the range $0.2« less

  13. Comparing cosmological hydrodynamic simulations with observations of high- redshift galaxy formation

    NASA Astrophysics Data System (ADS)

    Finlator, Kristian Markwart

    We use cosmological hydrodynamic simulations to study the impact of outflows and radiative feedback on high-redshift galaxies. For outflows, we consider simulations that assume (i) no winds, (ii) a "constant-wind" model in which the mass-loading factor and outflow speed are constant, and (iii) "momentum-driven" winds in which both parameters vary smoothly with mass. In order to treat radiative feedback, we develop a moment-based radiative transfer technique that operates in both post-processing and coupled radiative hydrodynamic modes. We first ask how outflows impact the broadband spectral energy distributions (SEDs) of six observed reionization-epoch galaxies. Simulations reproduce five regardless of the outflow prescription, while the sixth suggests an unusually bursty star formation history. We conclude that (i) simulations broadly account for available constraints on reionization-epoch galaxies, (ii) individual SEDs do not constrain outflows, and (iii) SED comparisons efficiently isolate objects that challenge simulations. We next study how outflows impact the galaxy mass metallicity relation (MZR). Momentum-driven outflows uniquely reproduce observations at z = 2. In this scenario, galaxies obey two equilibria: (i) The rate at which a galaxy processes gas into stars and outflows tracks its inflow rate; and (ii) The gas enrichment rate owing to star formation balances the dilution rate owing to inflows. Combining these conditions indicates that the MZR is dominated by the (instantaneous) variation of outflows with mass, with more-massive galaxies driving less gas into outflows per unit stellar mass formed. Turning to radiative feedback, we use post-processing simulations to study the topology of reionization. Reionization begins in overdensities and then "leaks" directly into voids, with filaments reionizing last owing to their high density and low emissivity. This result conflicts with previous findings that voids ionize last. We argue that it owes to the

  14. Local Group ultra-faint dwarf galaxies in the reionization era

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Boylan-Kolchin, Michael

    2017-07-01

    Motivated by the stellar fossil record of Local Group (LG) dwarf galaxies, we show that the star-forming ancestors of the faintest ultra-faint dwarf galaxies (UFDs; MV ˜ -2 or M⋆ ˜ 102 at z = 0) had ultraviolet (UV) luminosities of MUV ˜ -3 to -6 during reionization (z ˜ 6-10). The existence of such faint galaxies has substantial implications for early epochs of galaxy formation and reionization. If the faint-end slopes of the UV luminosity functions (UVLFs) during reionization are steep (α ≲ -2) to MUV ˜ -3, then (I) the ancestors of UFDs produced >50 per cent of UV flux from galaxies; (II) galaxies can maintain reionization with escape fractions that are more than two times lower than currently adopted values; (III) direct Hubble Space Telescope and James Webb Space Telescope observations may detect only ˜10-50 per cent of the UV light from galaxies; and (IV) the cosmic star formation history increases by ≳ 4-6 at z ≳ 6. Significant flux from UFDs, and resultant tensions with LG dwarf galaxy counts, is reduced if the high-redshift UVLF turns over. Independent of the UVLF shape, the existence of a large population of UFDs requires a non-zero luminosity function to MUV ˜ -3 during reionization.

  15. Anisotropic magnification distortion of the 3D galaxy correlation. II. Fourier and redshift space

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hui Lam; Department of Physics, Columbia University, New York, New York 10027; Institute of Theoretical Physics, Chinese University of Hong Kong

    2008-03-15

    In paper I of this series we discuss how magnification bias distorts the 3D correlation function by enhancing the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. This lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification and magnification-magnification correlations. Here we extend the discussion to the power spectrum and also to redshift space. In real space, pairs oriented close to the LOS direction are not protected against nonlinearity even if the pair separation is large; this is because nonlinear fluctuations can enter through gravitational lensing at a small transverse separation (or i.e.more » impact parameter). The situation in Fourier space is different: by focusing on a small wave number k, as is usually done, linearity is guaranteed because both the LOS and transverse wave numbers must be small. This is why magnification distortion of the galaxy correlation appears less severe in Fourier space. Nonetheless, the effect is non-negligible, especially for the transverse Fourier modes, and should be taken into account in interpreting precision measurements of the galaxy power spectrum, for instance those that focus on the baryon oscillations. The lensing induced anisotropy of the power spectrum has a shape that is distinct from the more well-known redshift space anisotropies due to peculiar motions and the Alcock-Paczynski effect. The lensing anisotropy is highly localized in Fourier space while redshift space distortions are more spread out. This means that one could separate the magnification bias component in real observations, implying that potentially it is possible to perform a gravitational lensing measurement without measuring galaxy shapes.« less

  16. Cosmological evolution of supermassive black holes in the centres of galaxies

    NASA Astrophysics Data System (ADS)

    Kapinska, Anna D.

    2012-06-01

    Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large scale structure. Their jets inject a significant amount of energy into the surrounding medium, hence they can provide useful information in the study of the density and evolution of the intergalactic and intracluster medium. The jet activity is also believed to regulate the growth of massive galaxies via the AGN feedback. In this thesis I explore the intrinsic and extrinsic physical properties of the population of Fanaroff-Riley II (FR II) objects, i.e. their kinetic luminosities, lifetimes, and central densities of their environments. In particular, the radio and kinetic luminosity functions of these powerful radio sources are investigated using the complete, flux limited radio catalogues of 3CRR and BRL. I construct multidimensional Monte Carlo simulations using semi-analytical models of FR II source time evolution to create artificial samples of radio galaxies. Unlike previous studies, I compare radio luminosity functions found with both the observed and simulated data to explore the best-fitting fundamental source parameters. The Monte Carlo method presented here allows one to: (i) set better limits on the predicted fundamental parameters of which confidence intervals estimated over broad ranges are presented, and (ii) generate the most plausible underlying parent populations of these radio sources. Moreover, I allow the source physical properties to co-evolve with redshift, and I find that all the investigated parameters most likely undergo cosmological evolution; however these parameters are strongly degenerate, and independent constraints are necessary to draw more precise conclusions. Furthermore, since it has been suggested that low luminosity FR IIs may be distinct from their powerful equivalents, I attempt to investigate fundamental properties of a sample of low redshift, low

  17. Starburst Galaxies. III. Properties of a Radio-selected Sample

    NASA Astrophysics Data System (ADS)

    Smith, Denise A.; Herter, Terry; Haynes, Martha P.

    1998-02-01

    We have analyzed the properties of the 20 most radio-luminous UGC starburst galaxies from Condon, Frayer, & Broderick. Near-infrared images, spectra, and optical rotation curves were presented in Smith et al. In this paper, we use these data and published radio data to assess the stellar populations, dust contents, ionizing conditions, and dynamics of the starbursts. Certain properties of the star formation occurring in these galaxies differ from those observed locally. The infrared excesses (IREs) are lower than and span a narrower range of values than those of Galactic H II regions. The starbursts appear to produce a higher proportion of ionizing photons than most Galactic H II regions. Consequently, the initial mass functions (IMFs) of the starbursts may be more strongly biased toward high-mass star formation. The starbursts may also contain fewer old H II regions than the Milky Way. Furthermore, the starburst IRE is likely to be influenced by the presence of large reservoirs of gas that absorb a larger fraction of the Lyman continuum photons. The OB stellar and far-infrared luminosities imply that the upper mass range of the starburst IMF (M > 10 M⊙) is characterized by a slope of 2.7 +/- 0.2. The starburst IMF thus bears a strong similarity to that observed in Magellanic OB associations. Optical line ratios indicate that a range of excitation conditions are present. We conclude that the near-infrared light from many of the starbursts is dominated by a heavily obscured mixture of emission from evolved red stars and young blue stars with small contributions (~5%) from thermal gas and hot dust, under the assumptions that a Galactic or SMC extinction law can be applied to these systems and that the true reddening curve follows one of the models currently existing in the literature. In some cases, larger amounts of emission from blue stars or hot dust may be required to explain the observed near-infrared colors. The amount of dust emission exceeds that predicted

  18. Star Cluster Properties in Two LEGUS Galaxies Computed with Stochastic Stellar Population Synthesis Models

    NASA Astrophysics Data System (ADS)

    Krumholz, Mark R.; Adamo, Angela; Fumagalli, Michele; Wofford, Aida; Calzetti, Daniela; Lee, Janice C.; Whitmore, Bradley C.; Bright, Stacey N.; Grasha, Kathryn; Gouliermis, Dimitrios A.; Kim, Hwihyun; Nair, Preethi; Ryon, Jenna E.; Smith, Linda J.; Thilker, David; Ubeda, Leonardo; Zackrisson, Erik

    2015-10-01

    We investigate a novel Bayesian analysis method, based on the Stochastically Lighting Up Galaxies (slug) code, to derive the masses, ages, and extinctions of star clusters from integrated light photometry. Unlike many analysis methods, slug correctly accounts for incomplete initial mass function (IMF) sampling, and returns full posterior probability distributions rather than simply probability maxima. We apply our technique to 621 visually confirmed clusters in two nearby galaxies, NGC 628 and NGC 7793, that are part of the Legacy Extragalactic UV Survey (LEGUS). LEGUS provides Hubble Space Telescope photometry in the NUV, U, B, V, and I bands. We analyze the sensitivity of the derived cluster properties to choices of prior probability distribution, evolutionary tracks, IMF, metallicity, treatment of nebular emission, and extinction curve. We find that slug's results for individual clusters are insensitive to most of these choices, but that the posterior probability distributions we derive are often quite broad, and sometimes multi-peaked and quite sensitive to the choice of priors. In contrast, the properties of the cluster population as a whole are relatively robust against all of these choices. We also compare our results from slug to those derived with a conventional non-stochastic fitting code, Yggdrasil. We show that slug's stochastic models are generally a better fit to the observations than the deterministic ones used by Yggdrasil. However, the overall properties of the cluster populations recovered by both codes are qualitatively similar.

  19. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  20. HI and Low Metal Ions at the Intersection of Galaxies and the CGM

    NASA Astrophysics Data System (ADS)

    Oppenheimer, Benjamin

    2017-08-01

    Over 1000 COS orbits have revealed a surprisingly complex picture of circumgalactic gas flows surrounding the diversity of galaxies in the evolved Universe. Cosmological hydrodynamic simulations have only begun to confront the vast amount of galaxy formation physics, chemistry, and dynamics revealed in the multi-ion CGM datasets. We propose the next generation of EAGLE zoom simulations, called EAGLE Cosmic Origins, to model HI and low metal ions (C II, Mg II, & Si II) throughout not just the CGM but also within the galaxies themselves. We will employ a novel, new chemistry solver, CHIMES, to follow time-dependent ionization, chemistry, and cooling of 157 ionic and molecular species, and include multiple ionization sources from the extra-galactic background, episodic AGN, and star formation. Our aim is to understand the complete baryon cycle of inflows, outflows, and gas recycling traced over 10 decades of HI column densities as well as the complex kinematic information encoded low ion absorption spectroscopy. This simulation project represents a pilot program for a larger suite of zoom simulations, which will be publicly released and lead to additional publications.

  1. Submillimeter Follow-up of WISE-selected Hyperluminous Galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R. M.; Stern, Daniel; Petty, Sara; Assef, Roberto; Bussmann, Shane; Comerford, Julia M.; Cutri, Roc; Evans, Neal J., II; Griffith, Roger; Jarrett, Thomas; Lake, Sean; Lonsdale, Carol; Rho, Jeonghee; Stanford, S. Adam; Weiner, Benjamin; Wright, Edward L.; Yan, Lin

    2012-09-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (~1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 μm, yet are clearly detected at 12 and 22 μm. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 μm, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 μm, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 1013 L ⊙. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  2. SUBMILLIMETER FOLLOW-UP OF WISE-SELECTED HYPERLUMINOUS GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wu Jingwen; Eisenhardt, Peter R. M.; Stern, Daniel

    2012-09-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare ({approx}1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 {mu}m, yet are clearly detected at 12 and 22 {mu}m. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 {mu}m, with nine detections, and observed 18 with Bolocam atmore » 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 {mu}m, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10{sup 13} L{sub Sun }. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.« less

  3. Submillimeter Follow-Up of WISE-Selected Hyperluminous Galaxies

    NASA Technical Reports Server (NTRS)

    Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R.; Stern, Daniel; Petty, Sara; Assef, Roberto; hide

    2012-01-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approx.1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 microns, yet are clearly detected at 12 and 22 microns. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 microns, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 microns, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60 C120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) Stellar Luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  4. Submillimeter Follow-up of Wise-Selected Hyperluminous Galaxies

    NASA Technical Reports Server (NTRS)

    Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R. M.; Stern, Daniel; Petty, Sara; Assef, Roberto; hide

    2013-01-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approximately 1000 all-sky) population of galaxies at high redshift (peaks at zeta = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 micrometers, yet are clearly detected at 12 and 22 micrometers. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (zeta greater than 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 micrometers, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 micrometers, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) solar luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  5. Galaxies Collide to Create Hot, Huge Galaxy

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy. The prolonged, violent collision has drastically altered the appearance of both galaxies and created huge amounts of heat turning NGC 6240 into an 'infrared luminous' active galaxy.

    A rich variety of active galaxies, with different shapes, luminosities and radiation profiles exist. These galaxies may be related astronomers have suspected that they may represent an evolutionary sequence. By catching different galaxies in different stages of merging, a story emerges as one type of active galaxy changes into another. NGC 6240 provides an important 'missing link' in this process.

    This image was created from combined data from the infrared array camera of NASA's Spitzer Space Telescope at 3.6 and 8.0 microns (red) and visible light from NASA's Hubble Space Telescope (green and blue).

  6. Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Schaerer, D.; Thuan, T. X.; Worseck, G.; Guseva, N. G.; Orlitová, I.; Verhamme, A.

    2016-10-01

    Following our first detection reported in Izotov et al., we present the detection of Lyman continuum (LyC) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. These galaxies, at redshifts of z ˜ 0.3, are characterized by high emission-line flux ratios [O III] λ5007/[O II] λ3727 ≳ 5. The escape fractions of the LyC radiation fesc(LyC) in these galaxies are in the range of ˜6-13 per cent, the highest values found so far in low-redshift star-forming galaxies. Narrow double-peaked Ly α emission lines are detected in the spectra of all four galaxies, compatible with predictions for LyC leakers. We find escape fractions of Ly α, fesc(Ly α) ˜ 20-40 per cent, among the highest known for Ly α emitting galaxies. Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the centre and exponential discs in the outskirts with disc scalelengths α in the range ˜0.6-1.4 kpc. Our galaxies are characterized by low metallicity, ˜1/8-1/5 solar, low stellar mass ˜(0.2-4) × 109 M⊙, high star formation rates, SFR ˜ 14-36 M⊙ yr-1, and high SFR densities, Σ ˜ 2-35 M⊙ yr-1 kpc-2. These properties are comparable to those of high-redshift star-forming galaxies. Finally, our observations, combined with our first detection reported in Izotov et al., reveal that a selection for compact star-forming galaxies showing high [O III] λ5007/[O II] λ3727 ratios appears to pick up very efficiently sources with escaping LyC radiation: all five of our selected galaxies are LyC leakers.

  7. Using r-process enhanced galaxies to estimate the neutron star merger rate at high redshift

    NASA Astrophysics Data System (ADS)

    Roederer, Ian

    2018-01-01

    The rapid neutron-capture process, or r-process, is one of the fundamental ways that stars produce heavy elements. I describe a new approach that uses the existence of r-process enhanced galaxies, like the recently discovered ultra-faint dwarf galaxy Reticulum II, to derive a rate for neutron star mergers at high redshift. This method relies on three assertions. First, several lines of reasoning point to neutron star mergers as a rare yet prolific producer of r-process elements, and one merger event is capable of enriching most of the stars in a low-mass dwarf galaxy. Second, the Local Group is cosmologically representative of the halo mass function at the mass scales of low-luminosity dwarf galaxies, and the volume that their progenitors spanned at high redshifts can be estimated from simulations. Third, many of these dwarf galaxies are extremely old, and the metals found in their stars today date from the earliest times at high redshift. These galaxies occupy a quantifiable volume of the Universe, from which the frequency of r-process enhanced galaxies can be estimated. This frequency may be interpreted as lower limit to the neutron star merger rate at a redshift (z ~ 5-10) that is much higher than is accessible to gravitational wave observatories. I will present a proof of concept demonstration using medium-resolution multi-object spectroscopy from the Michigan/Magellan Fiber System (M2FS) to recover the known r-process galaxy Reticulum II, and I will discuss future plans to apply this method to other Local Group dwarf galaxies.

  8. THE FMOS-COSMOS SURVEY OF STAR-FORMING GALAXIES AT z ∼ 1.6. I. Hα-BASED STAR FORMATION RATES AND DUST EXTINCTION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kashino, D.; Sugiyama, N.; Silverman, J. D.

    We present the first results from a near-IR spectroscopic survey of the COSMOS field, using the Fiber Multi-Object Spectrograph on the Subaru telescope, designed to characterize the star-forming galaxy population at 1.4 < z < 1.7. The high-resolution mode is implemented to detect Hα in emission between 1.6-1.8 μm with f {sub Hα} ∼> 4 × 10{sup –17} erg cm{sup –2} s{sup –1}. Here, we specifically focus on 271 sBzK-selected galaxies that yield a Hα detection thus providing a redshift and emission line luminosity to establish the relation between star formation rate and stellar mass. With further J-band spectroscopy formore » 89 of these, the level of dust extinction is assessed by measuring the Balmer decrement using co-added spectra. We find that the extinction (0.6 ∼< A {sub Hα} ∼< 2.5) rises with stellar mass and is elevated at high masses compared to low-redshift galaxies. Using this subset of the spectroscopic sample, we further find that the differential extinction between stellar and nebular emission E {sub star}(B – V)/E {sub neb}(B – V) is 0.7-0.8, dissimilar to that typically seen at low redshift. After correcting for extinction, we derive an Hα-based main sequence with a slope (0.81 ± 0.04) and normalization similar to previous studies at these redshifts.« less

  9. Petrologic evolution of CM chondrites: The difficulty of discriminating between nebular and parent-body effects

    NASA Astrophysics Data System (ADS)

    Kerridge, J. F.; McSween, H. Y., Jr.; Bunch, T. E.

    1994-07-01

    We wish to draw attention to a major controversy that has arisen in the area of CM-chondrite petrology. The problem is important because its resolution will have profound implications for ideas concerning nebular dynamics, gas-solid interactions in the nebula, and accretionary processes in the nebula, among other issues. On the one hand, cogent arguments have been presented that 'accretionary dust mantles,' were formed in the solar nebula prior to accretion of the CM parent asteroid(s). On the other hand, no-less-powerful arguments have been advanced that a significant fraction of the CM lithology is secondary, produced by aqueous alteration in the near-surface regions of an asteroid-sized object. Because most, if not all, CM chondrites are breccias, these two views could coexist harmoniously, were it not for the fact that some of the coarse-grained lithologies surrounded by 'accretion dust mantles' are themselves of apparently secondary origin. Such an observation must clearly force a reassessment of one or both of the present schools of thought. Our objective here is to stimulate such a reassessment. Four possible resolutions of this conflict may be postulated. First, perhaps nature found a way of permitting such secondary alteration to take place in the nebula. Second, maybe dust mantles could form in a regolith, rather than a nebular, environment. Third, it is possible that dust mantles around secondary lithologies are different from those around primary lithologies. Finally, perhaps formation of CM chondrites involved a more complex sequence of events than visualized so far, so that some apparently 'primary' processes postdated certain 'secondary' processes.

  10. MEASURING STAR FORMATION RATES AND FAR-INFRARED COLORS OF HIGH-REDSHIFT GALAXIES USING THE CO(7–6) AND [N II] 205 μm LINES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lu, Nanyao; Zhao, Yinghe; Xu, C. Kevin

    2015-03-20

    To better characterize the global star formation activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared color (e.g., the 60–100 μm color, C(60/100)) of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies ((U)LIRGs). To this end, here we exploit a new spectroscopic approach involving only two emission lines: CO(7–6) at 372 μm and [N ii] at 205 μm([N ii]{sub 205μm}). For local (U)LIRGs, the ratios ofmore » the CO(7–6) luminosity (L{sub CO(7–6)}) to the total infrared luminosity (L{sub IR}; 8–1000 μm) are fairly tightly distributed (to within ∼0.12 dex) and show little dependence on C(60/100). This makes L{sub CO(7–6)} a good SFR tracer, which is less contaminated by active galactic nuclei than L{sub IR} and may also be much less sensitive to metallicity than L{sub CO(1–0)}. Furthermore, the logarithmic [N ii]{sub 205μm}/CO(7–6) luminosity ratio depends fairly strongly (at a slope of ∼ −1.4) on C(60/100), with a modest scatter (∼0.23 dex). This makes it a useful estimator on C(60/100) with an implied uncertainty of ∼0.15 (or ≲4 K in the dust temperature (T{sub dust}) in the case of a graybody emission with T{sub dust} ≳ 30 K and a dust emissivity index β ≥ 1). Our locally calibrated SFR and C(60/100) estimators are shown to be consistent with the published data of (U)LIRGs of z up to ∼6.5.« less

  11. Low-redshift quasars in the SDSS Stripe 82: associated companion galaxies and signature of star formation

    NASA Astrophysics Data System (ADS)

    Bettoni, D.; Falomo, R.; Kotilainen, J. K.; Karhunen, K.

    2017-04-01

    We obtained optical spectroscopy of close (<80 kpc) companion objects of a sample of 12 low-redshift quasars (z < 0.3) selected from the SDSS Stripe82 area and that are in the subsample of 52 QSOs for which both multicolour host galaxies properties and galaxy environment were recently investigated in detail. We found that for 8 out of 12 sources the companion galaxy is associated with the QSO having a difference of radial velocity that is less than 400 km s-1. Many of these associated companions exhibit [OII] λ3727 Å emission lines suggestive of episodes of (recent) star formation possibly induced by past interactions. The star formation rate of the companion galaxies as derived from [O II] line luminosity is, however, modest, with a median value of 1.0 ± 0.8 M⊙ yr-1, and the emission lines are barely consistent with expectation from gas ionization by the QSO. The role of the QSO for inducing star formation in close companion galaxies appears meager. For three objects we also detect the starlight spectrum of the QSO host galaxy, which is characterized by absorption lines of old stellar population and [O II] emission line.

  12. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  13. Galaxies in the Illustris simulation as seen by the Sloan Digital Sky Survey - II. Size-luminosity relations and the deficit of bulge-dominated galaxies in Illustris at low mass

    NASA Astrophysics Data System (ADS)

    Bottrell, Connor; Torrey, Paul; Simard, Luc; Ellison, Sara L.

    2017-05-01

    The interpretive power of the newest generation of large-volume hydrodynamical simulations of galaxy formation rests upon their ability to reproduce the observed properties of galaxies. In this second paper in a series, we employ bulge+disc decompositions of realistic dust-free galaxy images from the Illustris simulation in a consistent comparison with galaxies from the Sloan Digital Sky Survey (SDSS). Examining the size-luminosity relations of each sample, we find that galaxies in Illustris are roughly twice as large and 0.7 mag brighter on average than galaxies in the SDSS. The trend of increasing slope and decreasing normalization of size-luminosity as a function of bulge fraction is qualitatively similar to observations. However, the size-luminosity relations of Illustris galaxies are quantitatively distinguished by higher normalizations and smaller slopes than for real galaxies. We show that this result is linked to a significant deficit of bulge-dominated galaxies in Illustris relative to the SDSS at stellar masses log M_{\\star }/M_{⊙}≲ 11. We investigate this deficit by comparing bulge fraction estimates derived from photometry and internal kinematics. We show that photometric bulge fractions are systematically lower than the kinematic fractions at low masses, but with increasingly good agreement as the stellar mass increases.

  14. WINGS: A WIde-field Nearby Galaxy-cluster Survey. II. Deep optical photometry of 77 nearby clusters

    NASA Astrophysics Data System (ADS)

    Varela, J.; D'Onofrio, M.; Marmo, C.; Fasano, G.; Bettoni, D.; Cava, A.; Couch, W. J.; Dressler, A.; Kjærgaard, P.; Moles, M.; Pignatelli, E.; Poggianti, B. M.; Valentinuzzi, T.

    2009-04-01

    Context: This is the second paper of a series devoted to the WIde Field Nearby Galaxy-cluster Survey (WINGS). WINGS is a long term project which is gathering wide-field, multi-band imaging and spectroscopy of galaxies in a complete sample of 77 X-ray selected, nearby clusters (0.04 < z < 0.07) located far from the galactic plane (|b|≥ 20°). The main goal of this project is to establish a local reference for evolutionary studies of galaxies and galaxy clusters. Aims: This paper presents the optical (B,V) photometric catalogs of the WINGS sample and describes the procedures followed to construct them. We have paid special care to correctly treat the large extended galaxies (which includes the brightest cluster galaxies) and the reduction of the influence of the bright halos of very bright stars. Methods: We have constructed photometric catalogs based on wide-field images in B and V bands using SExtractor. Photometry has been performed on images in which large galaxies and halos of bright stars were removed after modeling them with elliptical isophotes. Results: We publish deep optical photometric catalogs (90% complete at V ~ 21.7, which translates to ˜ M^*_V+6 at mean redshift), giving positions, geometrical parameters, and several total and aperture magnitudes for all the objects detected. For each field we have produced three catalogs containing galaxies, stars and objects of “unknown” classification (~6%). From simulations we found that the uncertainty of our photometry is quite dependent of the light profile of the objects with stars having the most robust photometry and de Vaucouleurs profiles showing higher uncertainties and also an additional bias of ~-0.2^m. The star/galaxy classification of the bright objects (V < 20) was checked visually making negligible the fraction of misclassified objects. For fainter objects, we found that simulations do not provide reliable estimates of the possible misclassification and therefore we have compared our data

  15. UV spectroscopy of the most metal-poor galaxies: clues for interpreting distant galaxy observations

    NASA Astrophysics Data System (ADS)

    Wofford, A.; Vidal-García, A.; Feltre, A.; Chevallard, J.; Herenz, E.; Charlot, S., Stark, D. P.; Hayes, M.

    2017-11-01

    Among the most metal-poor galaxies known, SBS 0335-052E is on one of the most well-studied. For this galaxy, we present Hubble Space Telescope (HST) / Cosmic Origins Spectrograph (COS) detections of the C IV λλ1549, 1551, He II λ1640, O III] λλ1661, 1666, [C III] λ1907, and C III] λ1909 UV emission lines; and a Very Large Telescope (VLT) / Multi Unit Spectroscopic Explorer (MUSE) spectrum covering from 4600 to 9400 Å, which is co-spatial with the UV data and integrated over the same area. Using these datasets we test: a) the latest Charlot & Bruzal spectral synthesis models with very massive (300 M_⊙) single non-rotating stars; b) the ability of the tool, BayEsian Analysis of GaLaxy sEds (BEAGLE) to reproduce the observed emission line fluxes; and c) the extent to which physical properties of the gas and dust derived independently from the UV and optical with BEAGLE are constrained. The UV observations are part of a pilot program where we also observed UGC 5340-1 and I Zw 18 SE, whose spectra we also present in this contribution.

  16. Carbon Abundances in Starburst Galaxies of the Local Universe

    NASA Astrophysics Data System (ADS)

    Peña-Guerrero, María A.; Leitherer, Claus; de Mink, Selma; Wofford, Aida; Kewley, Lisa

    2017-10-01

    The cosmological origin of carbon, the fourth most abundant element in the universe, is not well known and a matter of heavy debate. We investigate the behavior of C/O to O/H in order to constrain the production mechanism of carbon. We measured emission-line intensities in the spectral range from 1600 to 10000 Å on Space Telescope Imaging Spectrograph (STIS) long-slit spectra of 18 starburst galaxies in the local universe. We determined chemical abundances through traditional nebular analysis, and we used a Markov Chain Monte Carlo method to determine where our carbon and oxygen abundances lie in the parameter space. We conclude that our C and O abundance measurements are sensible. We analyzed the behavior of our sample in the [C/O] versus [O/H] diagram with respect to other objects such as DLAs, neutral ISM measurements, and disk and halo stars, finding that each type of object seems to be located in a specific region of the diagram. Our sample shows a steeper C/O versus O/H slope with respect to other samples, suggesting that massive stars contribute more to the production of C than N at higher metallicities, only for objects where massive stars are numerous; otherwise, intermediate-mass stars dominate the C and N production.

  17. The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey. A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)

    NASA Astrophysics Data System (ADS)

    Cormier, D.; Madden, S. C.; Lebouteiller, V.; Hony, S.; Aalto, S.; Costagliola, F.; Hughes, A.; Rémy-Ruyer, A.; Abel, N.; Bayet, E.; Bigiel, F.; Cannon, J. M.; Cumming, R. J.; Galametz, M.; Galliano, F.; Viti, S.; Wu, R.

    2014-04-01

    Context. Observations of nearby starburst and spiral galaxies have revealed that molecular gas is the driver of star formation. However, some nearby low-metallicity dwarf galaxies are actively forming stars, but CO, the most common tracer of this reservoir, is faint, leaving us with a puzzle about how star formation proceeds in these environments. Aims: We aim to quantify the molecular gas reservoir in a subset of 6 galaxies from the Herschel Dwarf Galaxy Survey with newly acquired CO data and to link this reservoir to the observed star formation activity. Methods: We present CO(1-0), CO(2-1), and CO(3-2) observations obtained at the ATNF Mopra 22-m, APEX, and IRAM 30-m telescopes, as well as [C ii] 157μm and [O i] 63μm observations obtained with the Herschel/PACS spectrometer in the 6 low-metallicity dwarf galaxies: Haro 11, Mrk 1089, Mrk 930, NGC 4861, NGC 625, and UM 311. We derived their molecular gas masses from several methods, including using the CO-to-H2 conversion factor XCO (both Galactic and metallicity-scaled values) and dust measurements. The molecular and atomic gas reservoirs were compared to the star formation activity. We also constrained the physical conditions of the molecular clouds using the non-LTE code RADEX and the spectral synthesis code Cloudy. Results: We detect CO in 5 of the 6 galaxies, including first detections in Haro 11 (Z ~ 0.4 Z⊙), Mrk 930 (0.2 Z⊙), and UM 311 (0.5 Z⊙), but CO remains undetected in NGC 4861 (0.2 Z⊙). The CO luminosities are low, while [C ii] is bright in these galaxies, resulting in [C ii]/CO(1-0) ≥ 10 000. Our dwarf galaxies are in relatively good agreement with the Schmidt-Kennicutt relation for total gas. They show short molecular depletion timescales, even when considering metallicity-scaled XCO factors. Those galaxies are dominated by their H i gas, except Haro 11, which has high star formation efficiency and is dominated by ionized and molecular gas. We determine the mass of each ISM phase in

  18. The planetary nebulae populations in five galaxies: abundance patterns and evolution

    NASA Astrophysics Data System (ADS)

    Stasińska, G.; Richer, M. G.; McCall, M. L.

    1998-08-01

    We have collected photometric and spectroscopic data on planetary nebulae (PNe) in 5 galaxies: the Milky Way (bulge), M 31 (bulge), M 32, the LMC and the SMC. We have computed the abundances of O, Ne and N and compared them from one galaxy to another. In each Galaxy, the distribution of oxygen abundances has a large dispersion. The average O/H ratio is larger in the M 31 and the Galactic bulge PNe than in those in the Magellanic Clouds. In a given galaxy, it is also larger for PNe with [O III] luminosities greater than 100 L_⊙, which are likely to probe more recent epochs in the galaxy history. We find that the M 31 and the Galactic bulge PNe extend the very tight Ne/H-O/H correlation observed in the Galactic disk and Magellanic Clouds PNe towards higher metallicities. We note that the anticorrelation between N/O and O/H that was known to occur in the Magellanic Clouds and in the disk PNe is also marginally found in the PNe of the Galactic bulge. Furthermore, we find that high N/O ratios are higher for less luminous PNe. In M 32, all PNe have a large N/O ratio, indicating that the stellar nitrogen abundance is enhanced in this galaxy. We have also compared the PN evolution in the different galactic systems by constructing diagrams that are independent of abundances, and have found strikingly different behaviours of the various samples. In order to help in the interpretation of these data, we have constructed a grid of expanding, PN photoionization models in which the central stars evolve according to the evolutionary tracks of Bl{öcker (1995). These models show that the apparent spectroscopic properties of PNe are extremely dependent, not only on the central stars, but also on the masses and expansion velocities of the nebular envelopes. The main conclusion of the confrontation of the observed samples with the model grids is that the PN populations are indeed not the same in the various parent galaxies. Both stars and nebulae are different. In particular, the

  19. Galaxy bias from galaxy-galaxy lensing in the DES science verification data

    NASA Astrophysics Data System (ADS)

    Prat, J.; Sánchez, C.; Miquel, R.; Kwan, J.; Blazek, J.; Bonnett, C.; Amara, A.; Bridle, S. L.; Clampitt, J.; Crocce, M.; Fosalba, P.; Gaztanaga, E.; Giannantonio, T.; Hartley, W. G.; Jarvis, M.; MacCrann, N.; Percival, W. J.; Ross, A. J.; Sheldon, E.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Fausti Neto, A.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lima, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.

    2018-01-01

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited (iAB < 22.5) sample of galaxies from the dark energy survey science verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias b and cross-correlation coefficient between the galaxy and dark matter overdensity fields r in each bin, using scales above 4 h-1 Mpc comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering and CMB lensing for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al., while, in the lowest redshift bin (z ∼ 0.3), they show some tension with the findings in Giannantonio et al. We measure b · r to be 0.87 ± 0.11, 1.12 ± 0.16 and 1.24 ± 0.23, respectively, for the three redshift bins of width Δz = 0.2 in the range 0.2 < z < 0.8, defined with the photometric-redshift algorithm BPZ. Using a different code to split the lens sample, TPZ, leads to changes in the measured biases at the 10-20 per cent level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. we do not find strong evidence for a cross-correlation parameter significantly below one in this galaxy sample, except possibly at the lowest redshift bin (z ∼ 0.3), where we find r = 0.71 ± 0.11 when using TPZ, and 0.83 ± 0.12 with BPZ.

  20. The Dependence of Galactic Outflows on the Properties and Orientation of zCOSMOS Galaxies at z ~ 1

    NASA Astrophysics Data System (ADS)

    Bordoloi, R.; Lilly, S. J.; Hardmeier, E.; Contini, T.; Kneib, J.-P.; Le Fevre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Zamorani, G.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Caputi, K.; Carollo, C. M.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Garilli, B.; Iovino, A.; Kampczyk, P.; Kovač, K.; Knobel, C.; Lamareille, F.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Mignoli, M.; Oesch, P.; Pello, R.; Peng, Y.; Perez Montero, E.; Presotto, V.; Silverman, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Cappi, A.; Cimatti, A.; Coppa, G.; Franzetti, P.; Koekemoer, A.; Moresco, M.; Nair, P.; Pozzetti, L.

    2014-10-01

    We present an analysis of cool outflowing gas around galaxies, traced by Mg II absorption lines in the coadded spectra of a sample of 486 zCOSMOS galaxies at 1 <= z <= 1.5. These galaxies span a range of stellar masses (9.45 <= log10[M */M ⊙] <= 10.7) and star formation rates (0.14 <= log10[SFR/M ⊙ yr-1] <= 2.35). We identify the cool outflowing component in the Mg II absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses, the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong correlation with the star formation surface density (ΣSFR) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from -150 km s-1 ~-200 km s-1 and, on average, the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit mass outflow rates >5-7 M ⊙ yr-1 and a mass loading factor ({ η = \\dot{M}out /SFR}) comparable to the star formation rates of the galaxies. Based on observations undertaken at the European Southern Observatory (ESO) Very Large Telescope (VLT) under Large Program 175.A-0839.

  1. Anisotropic magnification distortion of the 3D galaxy correlation. I. Real space

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hui, Lam; LoVerde, Marilena; Department of Physics, Columbia University, New York, New York 10027

    2007-11-15

    It has long been known that gravitational lensing, primarily via magnification bias, modifies the observed galaxy (or quasar) clustering. Such discussions have largely focused on the 2D angular correlation function. Here and in paper II [L. Hui, E. Gaztanaga, and M. LoVerde, arXiv:0710.4191] we explore how magnification bias distorts the 3D correlation function and power spectrum, as first considered by Matsubara [Astrophys. J. Lett. 537, L77 (2000).]. The interesting point is that the distortion is anisotropic. Magnification bias in general preferentially enhances the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. For instance, at a LOS separationmore » of {approx}100 Mpc/h, where the intrinsic galaxy-galaxy correlation is rather weak, the observed correlation can be enhanced by lensing by a factor of a few, even at a modest redshift of z{approx}0.35. This effect presents an interesting opportunity as well as a challenge. The opportunity: this lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification, and magnification-magnification correlations, without measuring galaxy shapes. The anisotropy is distinguishable from the well-known distortion due to peculiar motions, as will be discussed in paper II. The challenge: the magnification distortion of the galaxy correlation must be accounted for in interpreting data as precision improves. For instance, the {approx}100 Mpc/h baryon acoustic oscillation scale in the correlation function is shifted by up to {approx}3% in the LOS orientation, and up to {approx}0.6% in the monopole, depending on the galaxy bias, redshift, and number count slope. The corresponding shifts in the inferred Hubble parameter and angular diameter distance, if ignored, could significantly bias measurements of the dark energy equation of state. Lastly, magnification distortion offers a plausible explanation for the well-known excess correlations

  2. Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey: MMT and 3.5 m APO observations

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Thuan, T. X.; Guseva, N. G.

    2012-10-01

    We present 6.5-m MMT and 3.5 m APO spectrophotometry of 69 H ii regions in 42 low-metallicity emission-line galaxies, selected from the data release 7 of the Sloan Digital Sky Survey to have mostly [O iii]λ4959/Hβ ≲ 1 and [N ii]λ6583/Hβ ≲ 0.1. The electron temperature-sensitive emission line [O iii] λ4363 is detected in 53 H ii regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 H ii regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12 + log O/H ~ 7.1 to ~7.9, with 14 H ii regions in 7 galaxies with 12 + log O/H ≤ 7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12 + log O/H ≤ 7.35) emission-line galaxies known in the local universe. There appears to be a metallicity floor at 12 + log O/H ~ 6.9, suggesting that the matter from which dwarf emission-line galaxies formed was pre-enriched to that level by e.g. Population III stars. Based on observations with the Multiple Mirror telescope (MMT) and the 3.5 m Apache Point Observatory (APO). The MMT is operated by the MMT Observatory (MMTO), a joint venture of the Smithsonian Institution and the University of Arizona. The Apache Point Observatory 3.5-m telescope is owned and operated by the Astrophysical Research Consortium.Figures 1-3 and Tables 2-8 are available in electronic form at http://www.aanda.org

  3. CLUMPY GALAXIES IN CANDELS. I. THE DEFINITION OF UV CLUMPS AND THE FRACTION OF CLUMPY GALAXIES AT 0.5 < z < 3

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guo, Yicheng; Koo, David C.; Barro, Guillermo

    Although giant clumps of stars are thought to be crucial to galaxy formation and evolution, the most basic demographics of clumps are still uncertain, mainly because the definition of clumps has not been thoroughly discussed. In this paper, we carry out a study of the basic demographics of clumps in star-forming galaxies at 0.5 < z < 3, using our proposed physical definition that UV-bright clumps are discrete star-forming regions that individually contribute more than 8% of the rest-frame UV light of their galaxies. Clumps defined this way are significantly brighter than the H II regions of nearby large spiral galaxies,more » either individually or blended, when physical spatial resolution and cosmological dimming are considered. Under this definition, we measure the fraction of star-forming galaxies that have at least one off-center clump (f {sub clumpy}) and the contributions of clumps to the rest-frame UV light and star formation rate (SFR) of star-forming galaxies in the CANDELS/GOODS-S and UDS fields, where our mass-complete sample consists of 3239 galaxies with axial ratio q > 0.5. The redshift evolution of f {sub clumpy} changes with the stellar mass (M {sub *}) of the galaxies. Low-mass (log (M {sub *}/M {sub ☉}) < 9.8) galaxies keep an almost constant f {sub clumpy} of ∼60% from z ∼ 3 to z ∼ 0.5. Intermediate-mass and massive galaxies drop their f {sub clumpy} from 55% at z ∼ 3 to 40% and 15%, respectively, at z ∼ 0.5. We find that (1) the trend of disk stabilization predicted by violent disk instability matches the f {sub clumpy} trend of massive galaxies; (2) minor mergers are a viable explanation of the f {sub clumpy} trend of intermediate-mass galaxies at z < 1.5, given a realistic observability timescale; and (3) major mergers are unlikely responsible for the f {sub clumpy} trend in all masses at z < 1.5. The clump contribution to the rest-frame UV light of star-forming galaxies shows a broad peak around galaxies with log (M {sub *}/M

  4. VizieR Online Data Catalog: Morphologies of z<0.01 SDSS-DR7 galaxies (Ann+, 2015)

    NASA Astrophysics Data System (ADS)

    Ann, H. B.; Seo, M.; Ha, D. K.

    2015-05-01

    This paper presents a catalog of the morphological types of galaxies whose redshifts are less than z=0.01. The morphological types are determined by a visual inspection of the color images provided by SDSS DR7 (II/294). The majority of galaxies in the present sample come from the KIAS-VAGC (Choi et al. 2010JKAS...43..191C) which is based on the spectroscopic target galaxies of the SDSS DR7 complemented by the bright galaxies with known redshifts from various catalogs. (1 data file).

  5. Visible and Near-Infrared Spectroscopy of Seyfert 1 and Narrow-Line Seyfert 1 Galaxies

    NASA Astrophysics Data System (ADS)

    Rodríguez-Ardila, Alberto; Pastoriza, Miriani G.; Donzelli, Carlos J.

    2000-01-01

    This paper studies the continuum and emission-line properties of a sample composed of 16 normal Seyfert 1 and seven narrow-line Seyfert 1 (NLS1) galaxies using optical and near-IR CCD spectroscopy. The continuum emission of the galaxies can be described in terms of a combination of stellar population, a nonstellar continuum of power-law form, and Fe II emission. A significative difference in the optical spectral index between NLS1's and normal Seyfert 1's is observed; the latter is steeper. Most NLS1's show Fe II/Hβ ratios larger than those observed in the other Seyfert 1's. In the IRAS band, both groups of galaxies have very similar properties. We have searched for the presence of optically thin gas in the broad-line region (BLR) of the galaxies by comparing the broad O I λ8446 and Hα emission-line profiles. Our analysis show that in the NLS1's, both profiles are similar in shape and width. This result contradicts the hypothesis of thin gas emission in the high-velocity part of the BLR to explain the ``narrowness'' of broad optical permitted lines in these objects. Evidence of narrow O I λ8446 emission is found in six galaxies of our sample, implying that this line is not restricted to a pure BLR phenomenon. In the narrow-line region, we find similar luminosities in the permitted and high-ionization lines of NLS1's and normal Seyfert 1's. However, low-ionization lines such as [O I] λ6300, [O II] λ3727, and [S II] λλ6717, 6731 are intrinsically less luminous in NLS1's. Physical properties derived from density- and temperature-sensitive line ratios suggest that the [O II] and [S II] emitting zones are overlapping in normal Seyfert 1's and separated in NLS1's. Based on observations made at CASLEO. Complejo Astronómico El Leoncito (CASLEO) is operated under agreement between the Consejo Nacional de Investigaciones Científicas y técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juán.

  6. On the importance of using appropriate spectral models to derive physical properties of galaxies at 0.7 < z < 2.8

    NASA Astrophysics Data System (ADS)

    Pacifici, Camilla; da Cunha, Elisabete; Charlot, Stéphane; Rix, Hans-Walter; Fumagalli, Mattia; Wel, Arjen van der; Franx, Marijn; Maseda, Michael V.; van Dokkum, Pieter G.; Brammer, Gabriel B.; Momcheva, Ivelina; Skelton, Rosalind E.; Whitaker, Katherine; Leja, Joel; Lundgren, Britt; Kassin, Susan A.; Yi, Sukyoung K.

    2015-02-01

    Interpreting observations of distant galaxies in terms of constraints on physical parameters - such as stellar mass (M★), star formation rate (SFR) and dust optical depth ({hat{τ}V}) - requires spectral synthesis modelling. We analyse the reliability of these physical parameters as determined under commonly adopted `classical' assumptions: star formation histories assumed to be exponentially declining functions of time, a simple dust law and no emission-line contribution. Improved modelling techniques and data quality now allow us to use a more sophisticated approach, including realistic star formation histories, combined with modern prescriptions for dust attenuation and nebular emission. We present a Bayesian analysis of the spectra and multiwavelength photometry of 1048 galaxies from the 3D-HST survey in the redshift range 0.7 < z < 2.8 and in the stellar mass range 9 ≲ log (M★/M⊙) ≲ 12. We find that, using the classical spectral library, stellar masses are systematically overestimated (˜0.1 dex) and SFRs are systematically underestimated (˜0.6 dex) relative to our more sophisticated approach. We also find that the simultaneous fit of photometric fluxes and emission-line equivalent widths helps break a degeneracy between SFR and {hat{τ}V}, reducing the uncertainties on these parameters. Finally, we show how the biases of classical approaches can affect the correlation between M★ and SFR for star-forming galaxies (the `star-formation main sequence'). We conclude that the normalization, slope and scatter of this relation strongly depend on the adopted approach and demonstrate that the classical, oversimplified approach cannot recover the true distribution of M★ and SFR.

  7. On the Interaction of the PKS B1358-113 Radio Galaxy with the A1836 Cluster

    DOE PAGES

    Stawarz, L.; Szostek, A.; Cheung, C. C.; ...

    2014-10-07

    In this study, we present the analysis of multifrequency data gathered for the Fanaroff-Riley type-II (FR II) radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy in the center of A1836. The galaxy harbors one of the most massive black holes known to date, and our analysis of the acquired optical data reveals that this black hole is only weakly active, with a mass accretion ratemore » $$\\dot{M}_{\\rm acc} \\sim 2 \\times 10^{-4} \\, \\dot{M}_{\\rm Edd} \\sim 0.02 \\, M_{\\odot }$$ yr –1. Based on analysis of new Chandra and XMM-Newton X-ray observations and archival radio data, and assuming the well-established model for the evolution of FR II radio galaxies, we derive the preferred range for the jet kinetic luminosity L j ~ (1-6) × 10 –3 L Edd ~ (0.5-3) × 10 45 erg s –1. This is above the values implied by various scaling relations proposed for radio sources in galaxy clusters, being instead very close to the maximum jet power allowed for the given accretion rate. We also constrain the radio source lifetime as τ j ~ 40-70 Myr, meaning the total amount of deposited jet energy E tot ~ (2-8) × 10 60 erg. We argue that approximately half of this energy goes into shock heating of the surrounding thermal gas, and the remaining 50% is deposited into the internal energy of the jet cavity. The detailed analysis of the X-ray data provides indication for the presence of a bow shock driven by the expanding radio lobes into the A1836 cluster environment. We derive the corresponding shock Mach number in the range $$\\mathcal {M}_{\\rm sh} \\sim 2\\hbox{--}4$$, which is one of the highest claimed for clusters or groups of galaxies. This, together with the recently growing evidence that powerful FR II radio galaxies may not be uncommon in the centers of clusters at higher redshifts, supports the idea that jet-induced shock heating may indeed play an important role in shaping the properties of clusters, galaxy groups, and galaxies in formation. In this

  8. Quenching and ram pressure stripping of simulated Milky Way satellite galaxies

    NASA Astrophysics Data System (ADS)

    Simpson, Christine; Grand, Robert; Gomez, Facundo; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Campbell, David; Frenk, Carlos; Auriga Project, Virgo Consortium

    2018-01-01

    We present predictions for the quenching of star formation in satellite galaxies of the Local Group from a suite of 30 cosmological zoom simulations of Milky Way-like host galaxies. The Auriga simulations resolve satellites down to the luminosity of the classical dwarf spheroidal galaxies of the Milky Way. We find strong mass-dependent and distance-dependent quenching signals, where dwarf systems beyond 600 kpc are only strongly quenched below a stellar mass of 107 M⊙. Ram pressure stripping appears to be the dominant quenching mechanism and 50% of quenched systems cease star formation within 1 Gyr of first infall. We demonstrate that systems within a host galaxy's R200 radius are comprised of two populations: (i) a first infall population that has entered the host halo within the past few Gyrs and (ii) a population of returning `backsplash' systems that have had a much more extended interaction with the host. Backsplash galaxies that do not return to the host galaxy by redshift zero exhibit quenching properties similar to galaxies within R200 and are distinct from other external systems. The simulated quenching trend with stellar mass has some tension with observations, but our simulations are able reproduce the range of quenching times measured from resolved stellar populations of Local Group dwarf galaxies.

  9. Quenching and ram pressure stripping of simulated Milky Way satellite galaxies

    NASA Astrophysics Data System (ADS)

    Simpson, Christine M.; Grand, Robert J. J.; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Campbell, David J. R.; Frenk, Carlos S.

    2018-07-01

    We present predictions for the quenching of star formation in satellite galaxies of the Local Group from a suite of 30 cosmological zoom simulations of Milky Way-like host galaxies. The Auriga simulations resolve satellites down to the luminosity of the classical dwarf spheroidal galaxies of the Milky Way. We find strong mass-dependent and distance-dependent quenching signals, where dwarf systems beyond 600 kpc are only strongly quenched below a stellar mass of 107 M⊙. Ram pressure stripping appears to be the dominant quenching mechanism and 50 per cent of quenched systems cease star formation within 1 Gyr of first infall. We demonstrate that systems within a host galaxy's R200 radius are comprised of two populations: (i) a first infall population that has entered the host halo within the past few Gyrs and (ii) a population of returning `backsplash' systems that have had a much more extended interaction with the host. Backsplash galaxies that do not return to the host galaxy by redshift zero exhibit quenching properties similar to galaxies within R200 and are distinct from other external systems. The simulated quenching trend with stellar mass has some tension with observations, but our simulations are able reproduce the range of quenching times measured from resolved stellar populations of Local Group dwarf galaxies.

  10. Quenching and ram pressure stripping of simulated Milky Way satellite galaxies

    NASA Astrophysics Data System (ADS)

    Simpson, Christine M.; Grand, Robert J. J.; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rüdiger; Springel, Volker; Campbell, David J. R.; Frenk, Carlos S.

    2018-03-01

    We present predictions for the quenching of star formation in satellite galaxies of the Local Group from a suite of 30 cosmological zoom simulations of Milky Way-like host galaxies. The Auriga simulations resolve satellites down to the luminosity of the classical dwarf spheroidal galaxies of the Milky Way. We find strong mass-dependent and distance-dependent quenching signals, where dwarf systems beyond 600 kpc are only strongly quenched below a stellar mass of 107 M⊙. Ram pressure stripping appears to be the dominant quenching mechanism and 50% of quenched systems cease star formation within 1 Gyr of first infall. We demonstrate that systems within a host galaxy's R200 radius are comprised of two populations: (i) a first infall population that has entered the host halo within the past few Gyrs and (ii) a population of returning `backsplash' systems that have had a much more extended interaction with the host. Backsplash galaxies that do not return to the host galaxy by redshift zero exhibit quenching properties similar to galaxies within R200 and are distinct from other external systems. The simulated quenching trend with stellar mass has some tension with observations, but our simulations are able reproduce the range of quenching times measured from resolved stellar populations of Local Group dwarf galaxies.

  11. Understanding Galaxy Shapes Across Cosmic Time Using The IllustrisTNG Simulation

    NASA Astrophysics Data System (ADS)

    Genel, Shy

    2017-08-01

    Legacy HST observations have enabled groundbreaking measurements of galaxy structure over cosmic time, measurements that still require theoretical interpretation in the context of a comprehensive galaxy evolution model. This proposed research aims at significantly promoting our understanding of the shapes of galaxies as quantified by their principal axes ratios. The main tool we propose to use is IllustrisTNG, a suite consisting of two of the largest cosmological hydrodynamical simulations run to date, which contain resolved galaxy populations (thousands of L* galaxies) that represent a state-of-the-art match to observed galaxies. In Part I of the program, we will use the simulations to create mock images and study the dependence of projected shape measurements on various factors: shape estimator, observed band, the presence of dust, radial and surface brightness cuts, and noise. We will then perform apples-to-apples comparison with observations (including HST), and provide predictions for archival as well as future observations. Further, we will quantify the intrinsic, three-dimensional, shape distribution of galaxies as a function of various galaxy parameters: redshift, mass, color, and size. In Part II of the program, we will develop theoretical insights into the physical mechanisms driving these results. We will study how galaxy shapes relate to angular momentum and merger history, and will follow the shape evolution of individual galaxies over time, looking for correlations to the evolution of other galaxy properties, e.g. size and SFR. We will also study galaxy shape relations to dark matter halo shape, thereby providing input for high-precision cosmic shear models.

  12. BUDHIES II: a phase-space view of H I gas stripping and star formation quenching in cluster galaxies

    NASA Astrophysics Data System (ADS)

    Jaffé, Yara L.; Smith, Rory; Candlish, Graeme N.; Poggianti, Bianca M.; Sheen, Yun-Kyeong; Verheijen, Marc A. W.

    2015-04-01

    We investigate the effect of ram-pressure from the intracluster medium on the stripping of H I gas in galaxies in a massive, relaxed, X-ray bright, galaxy cluster at z = 0.2 from the Blind Ultra Deep H I Environmental Survey (BUDHIES). We use cosmological simulations, and velocity versus position phase-space diagrams to infer the orbital histories of the cluster galaxies. In particular, we embed a simple analytical description of ram-pressure stripping in the simulations to identify the regions in phase-space where galaxies are more likely to have been sufficiently stripped of their H I gas to fall below the detection limit of our survey. We find a striking agreement between the model predictions and the observed location of H I-detected and non-detected blue (late-type) galaxies in phase-space, strongly implying that ram-pressure plays a key role in the gas removal from galaxies, and that this can happen during their first infall into the cluster. However, we also find a significant number of gas-poor, red (early-type) galaxies in the infall region of the cluster that cannot easily be explained with our model of ram-pressure stripping alone. We discuss different possible additional mechanisms that could be at play, including the pre-processing of galaxies in their previous environment. Our results are strengthened by the distribution of galaxy colours (optical and UV) in phase-space, that suggests that after a (gas-rich) field galaxy falls into the cluster, it will lose its gas via ram-pressure stripping, and as it settles into the cluster, its star formation will decay until it is completely quenched. Finally, this work demonstrates the utility of phase-space diagrams to analyse the physical processes driving the evolution of cluster galaxies, in particular H I gas stripping.

  13. Rest-Frame Optical Spectra of Three Strongly Lensed Galaxies at z ~ 2

    NASA Astrophysics Data System (ADS)

    Hainline, Kevin N.; Shapley, Alice E.; Kornei, Katherine A.; Pettini, Max; Buckley-Geer, Elizabeth; Allam, Sahar S.; Tucker, Douglas L.

    2009-08-01

    We present Keck II NIRSPEC rest-frame optical spectra for three recently discovered lensed galaxies: the Cosmic Horseshoe (z = 2.38), the Clone (z = 2.00), and SDSS J090122.37+181432.3 (z = 2.26). The boost in signal-to-noise ratio (S/N) from gravitational lensing provides an unusually detailed view of the physical conditions in these objects. A full complement of high S/N rest-frame optical emission lines is measured, spanning from rest frame 3600 to 6800 Å, including robust detections of fainter lines such as Hγ, [S II]λ6717,6732, and in one instance [Ne III]λ3869. SDSS J090122.37+181432.3 shows evidence for active galactic nucleus activity, and therefore we focus our analysis on star-forming regions in the Cosmic Horseshoe and the Clone. For these two objects, we estimate a wide range of physical properties. Current lensing models for the Cosmic Horseshoe and the Clone allow us to correct the measured Hα luminosity and calculated star formation rate. Metallicities have been estimated with a variety of indicators, which span a range of values of 12+ log(O/H) = 8.3-8.8, between ~0.4 and ~1.5 of the solar oxygen abundance. Dynamical masses were computed from the Hα velocity dispersions and measured half-light radii of the reconstructed sources. A comparison of the Balmer lines enabled measurement of dust reddening coefficients. Variations in the line ratios between the different lensed images are also observed, indicating that the spectra are probing different regions of the lensed galaxies. In all respects, the lensed objects appear fairly typical of ultraviolet-selected star-forming galaxies at z ~ 2. The Clone occupies a position on the emission-line diagnostic diagram of [O III]/Hβ versus [N II]/Hα that is offset from the locations of z ~ 0 galaxies. Our new NIRSPEC measurements may provide quantitative insights into why high-redshift objects display such properties. From the [S II] line ratio, high electron densities (~1000 cm-3) are inferred compared

  14. Source-plane reconstruction of the giant gravitational arc in A2667: A candidate Wolf-Rayet galaxy at z ∼ 1

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cao, Shuo; Zhu, Zong-Hong; Covone, Giovanni

    We present a new analysis of Hubble Space Telescope, Spitzer Space Telescope, and Very Large Telescope imaging and spectroscopic data of a bright lensed galaxy at z = 1.0334 in the lensing cluster A2667. Using this high-resolution imaging, we present an updated lens model that allows us to fully understand the lensing geometry and reconstruct the lensed galaxy in the source plane. This giant arc gives a unique opportunity to view the structure of a high-redshift disk galaxy. We find that the lensed galaxy of A2667 is a typical spiral galaxy with a morphology similar to the structure of itsmore » counterparts at higher redshift, z ∼ 2. The surface brightness of the reconstructed source galaxy in the z {sub 850} band reveals the central surface brightness I(0) = 20.28 ± 0.22 mag arcsec{sup –2} and a characteristic radius r{sub s} = 2.01 ± 0.16 kpc at redshift z ∼ 1. The morphological reconstruction in different bands shows obvious negative radial color gradients for this galaxy. Moreover, the redder central bulge tends to contain a metal-rich stellar population, rather than being heavily reddened by dust due to high and patchy obscuration. We analyze the VIMOS/integral field unit spectroscopic data and find that, in the given wavelength range (∼1800-3200 Å), the combined arc spectrum of the source galaxy is characterized by a strong continuum emission with strong UV absorption lines (Fe II and Mg II) and shows the features of a typical starburst Wolf-Rayet galaxy, NGC 5253. More specifically, we have measured the equivalent widths of Fe II and Mg II lines in the A2667 spectrum, and obtained similar values for the same wavelength interval of the NGC 5253 spectrum. Marginal evidence for [C III] 1909 emission at the edge of the grism range further confirms our expectation.« less

  15. THE ZURICH ENVIRONMENTAL STUDY OF GALAXIES IN GROUPS ALONG THE COSMIC WEB. I. WHICH ENVIRONMENT AFFECTS GALAXY EVOLUTION?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carollo, C. Marcella; Cibinel, Anna; Lilly, Simon J.

    2013-10-20

    The Zurich Environmental Study (ZENS) is based on a sample of ∼1500 galaxy members of 141 groups in the mass range ∼10{sup 12.5-14.5} M{sub ☉} within the narrow redshift range 0.05 < z < 0.0585. ZENS adopts novel approaches, described here, to quantify four different galactic environments, namely: (1) the mass of the host group halo; (2) the projected halo-centric distance; (3) the rank of galaxies as central or satellites within their group halos; and (4) the filamentary large-scale structure density. No self-consistent identification of a central galaxy is found in ∼40% of <10{sup 13.5} M{sub ☉} groups, from whichmore » we estimate that ∼15% of groups at these masses are dynamically unrelaxed systems. Central galaxies in relaxed and unrelaxed groups generally have similar properties, suggesting that centrals are regulated by their mass and not by their environment. Centrals in relaxed groups have, however, ∼30% larger sizes than in unrelaxed groups, possibly due to accretion of small satellites in virialized group halos. At M > 10{sup 10} M{sub ☉}, satellite galaxies in relaxed and unrelaxed groups have similar size, color, and (specific) star formation rate distributions; at lower galaxy masses, satellites are marginally redder in relaxed relative to unrelaxed groups, suggesting quenching of star formation in low-mass satellites by physical processes active in relaxed halos. Overall, relaxed and unrelaxed groups show similar stellar mass populations, likely indicating similar stellar mass conversion efficiencies. In the enclosed ZENS catalog, we publish all environmental diagnostics as well as the galaxy structural and photometric measurements described in companion ZENS papers II and III.« less

  16. Galaxy Morphology Revealed By SDSS: Blue Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Ann, Hong Bae

    The Sloan Digital Sky Survey (SDSS) reveals many new features of galaxy morphologies. Among others, the discovery of blue elliptical galaxies provides some insights into the formation and evolution of galaxies. There seems to be two types of blue elliptical galaxies. One type shows globally blue colors suggesting star formations over the entire galaxy whereas the other type shows blue core that indicates enhanced star formation in the nuclear regions. The former seems to be currently forming galaxies, while the latter is thought to be in transition stage from the blue cloud to the red sequence due to AGN feedback.

  17. Age, size, and position of H ii regions in the Galaxy. Expansion of ionized gas in turbulent molecular clouds

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Anderson, L. D.; Didelon, P.; Raga, A. C.; Minier, V.; Ntormousi, E.; Pettitt, A.; Pinto, C.; Samal, M. R.; Schneider, N.; Zavagno, A.

    2014-08-01

    Aims: This work aims to improve the current understanding of the interaction between H ii regions and turbulent molecular clouds. We propose a new method to determine the age of a large sample of OB associations by investigating the development of their associated H ii regions in the surrounding turbulent medium. Methods: Using analytical solutions, one-dimensional (1D), and three-dimensional (3D) simulations, we constrained the expansion of the ionized bubble depending on the turbulence level of the parent molecular cloud. A grid of 1D simulations was then computed in order to build isochrone curves for H ii regions in a pressure-size diagram. This grid of models allowed us to date a large sample of OB associations that we obtained from the H ii Region Discovery Survey (HRDS). Results: Analytical solutions and numerical simulations showed that the expansion of H ii regions is slowed down by the turbulence up to the point where the pressure of the ionized gas is in a quasi-equilibrium with the turbulent ram pressure. Based on this result, we built a grid of 1D models of the expansion of H ii regions in a profile based on Larson's laws. We take the 3D turbulence into account with an effective 1D temperature profile. The ages estimated by the isochrones of this grid agree well with literature values of well known regions such as Rosette, RCW 36, RCW 79, and M 16. We thus propose that this method can be used to find ages of young OB associations through the Galaxy and also in nearby extra-galactic sources.

  18. Spiral Galaxies Stripped Bare

    NASA Astrophysics Data System (ADS)

    2010-10-01

    Six spectacular spiral galaxies are seen in a clear new light in images from ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile. The pictures were taken in infrared light, using the impressive power of the HAWK-I camera, and will help astronomers understand how the remarkable spiral patterns in galaxies form and evolve. HAWK-I [1] is one of the newest and most powerful cameras on ESO's Very Large Telescope (VLT). It is sensitive to infrared light, which means that much of the obscuring dust in the galaxies' spiral arms becomes transparent to its detectors. Compared to the earlier, and still much-used, VLT infrared camera ISAAC, HAWK-I has sixteen times as many pixels to cover a much larger area of sky in one shot and, by using newer technology than ISAAC, it has a greater sensitivity to faint infrared radiation [2]. Because HAWK-I can study galaxies stripped bare of the confusing effects of dust and glowing gas it is ideal for studying the vast numbers of stars that make up spiral arms. The six galaxies are part of a study of spiral structure led by Preben Grosbøl at ESO. These data were acquired to help understand the complex and subtle ways in which the stars in these systems form into such perfect spiral patterns. The first image shows NGC 5247, a spiral galaxy dominated by two huge arms, located 60-70 million light-years away. The galaxy lies face-on towards Earth, thus providing an excellent view of its pinwheel structure. It lies in the zodiacal constellation of Virgo (the Maiden). The galaxy in the second image is Messier 100, also known as NGC 4321, which was discovered in the 18th century. It is a fine example of a "grand design" spiral galaxy - a class of galaxies with very prominent and well-defined spiral arms. About 55 million light-years from Earth, Messier 100 is part of the Virgo Cluster of galaxies and lies in the constellation of Coma Berenices (Berenice's Hair, named after the ancient Egyptian queen Berenice II). The third

  19. Which Galaxies Are the Most Habitable?

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    Habitable zones are a hot topic in exoplanet studies: where, around a given star, could a planet exist that supports life? But if you scale this up, you get a much less common question: which type of galaxy is most likely to host complex life in the universe? A team of researchers from the UK believes it has the answer.Criteria for HabitabilityLed by Pratika Dayal of the University of Durham, the authors of this study set out to estimate the habitability of a large population of galaxies. The first step in this process is to determine what elements contribute to a galaxys habitability. The authors note three primary factors:Total number of starsMore stars means more planets!Metallicity of the starsPlanets are more likely to form in stellar vicinities with higher metallicities, since planet formation requires elements heavier than iron.Likelihood of Type II supernovae nearbyPlanets that are located out of range of supernovae have a higher probability of being habitable, since a major dose of cosmic radiation is likely to cause mass extinctions or delay evolution of complex life. Galaxies supernova rates can be estimated from their star formation rates (the two are connected via the initial mass function).Hospitable Cosmic GiantsLower panel: the number of Earth-like habitable planets (given by the color bar, which shows the log ratio relative to the Milky Way) increases in galaxies with larger stellar mass and lower star formation rates. Upper panel: the larger stellar-mass galaxies tend to be elliptical (blue line) rather than spiral (red line). Click for larger view. [Dayal et al. 2015]Interestingly, these three conditions have previously been shown to be linked via something termed the fundamental metallicity relation, which relates the total stellar masses, metallicities, and star formation rates of galaxies. By using this relation, the authors were able to create predictions for the number of habitable planets in more than 100,000 galaxies in the local universe

  20. H I CONTENT AND OPTICAL PROPERTIES OF FIELD GALAXIES FROM THE ALFALFA SURVEY. II. MULTIVARIATE ANALYSIS OF A GALAXY SAMPLE IN LOW-DENSITY ENVIRONMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Toribio, M. Carmen; Solanes, Jose M.; Giovanelli, Riccardo

    This is the second paper of two reporting results from a study of the H I content and stellar properties of nearby galaxies detected by the Arecibo Legacy Fast ALFA blind 21 cm line survey and the Sloan Digital Sky Survey in a 2160 deg{sup 2} region of high galactic latitude sky covered by both surveys, in the general Virgo direction. Here, we analyze a complete H I flux-limited subset of 1624 objects with homogeneously measured 21 cm and multi-wavelength optical attributes extracted from the control sample of H I emitters in environments of low local galactic density assembled bymore » Toribio et al. (Paper I). Strategies of multivariate data analysis are applied to this data set in order to (i) investigate the correlation structure of the space defined by an extensive set of potentially independent observables describing gas-rich systems, (ii) identify the intrinsic parameters that best define their neutral gas content, and (iii) explore the scaling relations arising from the joint distributions of the quantities most strongly correlated with the H I mass. The principal component analysis performed over a set of five galaxy properties reveals that they are strongly interrelated, supporting previous claims that nearby H I emitters show a high degree of correlation. The best predictors for the expected value of M{sub HI} are the diameter of the stellar disk, D{sub 25,r}, followed by the total luminosity (both in the r band), and the maximum rotation speed, while morphological proxies such as color show only a moderately strong correlation with the gaseous content attenuated by observational error. Among the various inferred prescriptions, the simplest and most accurate is log(M{sub HI}/M{sub sun}) = 8.72 + 1.25 log(D{sub 25,r}/kpc). We find a slope of -8.2 {+-} 0.5 for the relation between optical magnitude and log rotation speed, in good agreement with Tully-Fisher studies, as well as a log slope of 1.55 {+-} 0.06 for the H I mass-optical galaxy size relation