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Sample records for actively star-forming galaxies

  1. NUCLEAR ACTIVITY IS MORE PREVALENT IN STAR-FORMING GALAXIES

    SciTech Connect

    Rosario, D. J.; Lutz, D.; Berta, S.; Popesso, P.; Genzel, R.; Saintonge, A.; Tacconi, L.; Wuyts, S. E-mail: lutz@mpe.mpg.de E-mail: popesso@mpe.mpg.de E-mail: amelie@mpe.mpg.de E-mail: swuyts@mpe.mpg.de; and others

    2013-07-01

    We explore the question of whether low and moderate luminosity active galactic nuclei (AGNs) are preferentially found in galaxies that are undergoing a transition from active star formation (SF) to quiescence. This notion has been suggested by studies of the UV-optical colors of AGN hosts, which find them to be common among galaxies in the so-called Green Valley, a region of galaxy color space believed to be composed mostly of galaxies undergoing SF quenching. Combining the deepest current X-ray and Herschel/PACS far-infrared (FIR) observations of the two Chandra Deep Fields with redshifts, stellar masses, and rest-frame photometry derived from the extensive and uniform multi-wavelength data in these fields, we compare the rest-frame U - V color distributions and star formation rate distributions of AGNs and carefully constructed samples of inactive control galaxies. The UV-to-optical colors of AGNs are consistent with equally massive inactive galaxies at redshifts out to z {approx} 2, but we show that such colors are poor tracers of SF. While the FIR distributions of both star-forming AGNs and star-forming inactive galaxies are statistically similar, we show that AGNs are preferentially found in star-forming host galaxies, or, in other words, AGNs are less likely to be found in weakly star-forming or quenched galaxies. We postulate that, among X-ray-selected AGNs of low and moderate accretion luminosities, the supply of cold gas primarily determines the accretion rate distribution of the nuclear black holes.

  2. WIDESPREAD AND HIDDEN ACTIVE GALACTIC NUCLEI IN STAR-FORMING GALAXIES AT REDSHIFT >0.3

    SciTech Connect

    Juneau, Stephanie; Bournaud, Frederic; Daddi, Emanuele; Elbaz, David; Alexander, David M.; Mullaney, James R.; Magnelli, Benjamin; Hwang, Ho Seong; Willner, S. P.; Coil, Alison L.; Rosario, David J.; Trump, Jonathan R.; Faber, S. M.; Kocevski, Dale D.; Cooper, Michael C.; Frayer, David T.; and others

    2013-02-20

    We characterize the incidence of active galactic nuclei (AGNs) in 0.3 < z < 1 star-forming galaxies by applying multi-wavelength AGN diagnostics (X-ray, optical, mid-infrared, radio) to a sample of galaxies selected at 70 {mu}m from the Far-Infrared Deep Extragalactic Legacy survey (FIDEL). Given the depth of FIDEL, we detect 'normal' galaxies on the specific star formation rate (sSFR) sequence as well as starbursting systems with elevated sSFR. We find an overall high occurrence of AGN of 37% {+-} 3%, more than twice as high as in previous studies of galaxies with comparable infrared luminosities and redshifts but in good agreement with the AGN fraction of nearby (0.05 < z < 0.1) galaxies of similar infrared luminosities. The more complete census of AGNs comes from using the recently developed Mass-Excitation (MEx) diagnostic diagram. This optical diagnostic is also sensitive to X-ray weak AGNs and X-ray absorbed AGNs, and reveals that absorbed active nuclei reside almost exclusively in infrared-luminous hosts. The fraction of galaxies hosting an AGN appears to be independent of sSFR and remains elevated both on the sSFR sequence and above. In contrast, the fraction of AGNs that are X-ray absorbed increases substantially with increasing sSFR, possibly due to an increased gas fraction and/or gas density in the host galaxies.

  3. THE PRESENCE OF WEAK ACTIVE GALACTIC NUCLEI IN HIGH REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Wright, Shelley A.; Graham, James R.; Ma, C-P; Larkin, James E.

    2010-03-10

    We present [O III 5007 A] observations of the star-forming galaxy (SFG) HDF-BMZ1299 (z = 1.598) using Keck Observatory's adaptive optics system with the near-infrared {integral} field spectrograph OSIRIS. Using previous Halpha and [N II] measurements of the same source, we are able for the first time to use spatially resolved observations to place a high-redshift galaxy's substructure on a traditional H II diagnostic diagram. We find that HDF-BMZ1299's spatially concentrated nebular ratios in the central {approx}1.5 kpc (0.''2) are best explained by the presence of an active galactic nucleus (AGN): log ([N II]/Halpha) = -0.22 +- 0.05 and 2sigma limit of log ([O III]/Hbeta) {approx}>0.26. The dominant energy source of this galaxy is star formation, and integrating a single aperture across the galaxy yields nebular ratios that are composite spectra from both AGN and H II regions. The presence of an embedded AGN in HDF-BMZ1299 may suggest a potential contamination in a fraction of other high-redshift SFGs, and we suggest that this may be a source of the 'elevated' nebular ratios previously seen in seeing-limited metallicity studies. HDF-BMZ1299's estimated AGN luminosity is L{sub Halpha} = (3.7 +- 0.5) x 10{sup 41} erg s{sup -1} and L{sub [O{sub III}]} = (5.8 +- 1.9) x 10{sup 41} erg s{sup -1}, making it one of the lowest luminosity AGNs discovered at this early epoch.

  4. EVIDENCE FOR LOW EXTINCTION IN ACTIVELY STAR-FORMING GALAXIES AT z > 6.5

    SciTech Connect

    Walter, F.; Decarli, R.; Carilli, C.; Riechers, D.; Bertoldi, F.; Weiss, A.; Cox, P.; Neri, R.; Maiolino, R.; Ouchi, M.; Egami, E.

    2012-06-20

    We present a search for the [C II] 158 {mu}m fine structure line (a main cooling line of the interstellar medium) and the underlying far-infrared (FIR) continuum in three high-redshift (6.6 < z < 8.2) star-forming galaxies using the IRAM Plateau de Bure Interferometer. We targeted two Ly{alpha}-selected galaxies (Ly{alpha} emitters, LAEs) with moderate UV-based star formation rates (SFRs {approx} 20 M{sub Sun} yr{sup -1}; Himiko at z = 6.6 and IOK-1 at z = 7.0) and a gamma-ray burst (GRB) host galaxy (GRB 090423 at z {approx} 8.2). Based on our 3{sigma} rest-frame FIR continuum limits, previous (rest-frame) UV continuum measurements and spectral energy distribution (SED) fitting, we rule out SED shapes similar to highly obscured galaxies (e.g., Arp 220, M 82) and less extreme dust-rich nearby spiral galaxies (e.g., M 51) for the LAEs. Conservatively assuming an SED shape typical of local spiral galaxies we derive upper limits for the FIR-based star formation rates (SFRs) of {approx}70 M{sub Sun} yr{sup -1}, {approx}50 M{sub Sun} yr{sup -1}, and {approx}40 M{sub Sun} yr{sup -1} for Himiko, IOK-1, and GRB 090423, respectively. For the LAEs these limits are only a factor {approx}3 higher than the published UV-based SFRs (uncorrected for extinction). This indicates that the dust obscuration in the z > 6 LAEs studied here is lower by a factor of a few than what has recently been found in some LAEs at lower redshift (2 < z < 3.5) with similar UV-based SFRs. A low obscuration in our z > 6 LAE sample is consistent with recent rest-frame UV studies of z {approx} 7 Lyman break galaxies.

  5. The Dust Content and Opacity of Actively Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Calzetti, Daniela; Armus, Lee; Bohlin, Ralph C.; Kinney, Anne L.; Koornneef, Jan; Storchi-Bergmann, Thaisa

    2000-01-01

    ), UV - bright star-forming galaxies, these galaxies' FIR emission will be generally undetected in submillimeter surveys, unless: (1) their bolometric luminosity is comparable to or larger than that of ultraluminous FIR galaxies and (2) their FIR SED contains a cool dust component.

  6. GOODS-HERSCHEL: SEPARATING HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI AND STAR-FORMING GALAXIES USING INFRARED COLOR DIAGNOSTICS

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Charmandaris, Vassilis; Daddi, Emmanuele; Elbaz, David; Pannella, Maurilio; Aussel, Herve; Dasyra, Kalliopi; Leiton, Roger; Scott, Douglas; Magnelli, Benjamin; Popesso, Paola; Altieri, Bruno; Coia, Daniela; Valtchanov, Ivan; Dannerbauer, Helmut; Dickinson, Mark; Kartaltepe, Jeyhan; Magdis, Georgios

    2013-02-15

    We have compiled a large sample of 151 high-redshift (z = 0.5-4) galaxies selected at 24 {mu}m (S {sub 24} > 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-infrared spectrum into contributions from star formation and activity in the galactic nuclei. In addition, we have a wealth of photometric data from Spitzer IRAC/MIPS and Herschel PACS/SPIRE. We explore how effective different infrared color combinations are at separating our mid-IR spectroscopically determined active galactic nuclei from our star-forming galaxies. We look in depth at existing IRAC color diagnostics, and we explore new color-color diagnostics combining mid-IR, far-IR, and near-IR photometry, since these combinations provide the most detail about the shape of a source's IR spectrum. An added benefit of using a color that combines far-IR and mid-IR photometry is that it is indicative of the power source driving the IR luminosity. For our data set, the optimal color selections are S {sub 250}/S {sub 24} versus S {sub 8}/S {sub 3.6} and S {sub 100}/S {sub 24} versus S {sub 8}/S {sub 3.6}; both diagnostics have {approx}10% contamination rate in the regions occupied primarily by star-forming galaxies and active galactic nuclei, respectively. Based on the low contamination rate, these two new IR color-color diagnostics are ideal for estimating both the mid-IR power source of a galaxy when spectroscopy is unavailable and the dominant power source contributing to the IR luminosity. In the absence of far-IR data, we present color diagnostics using the Wide-field Infrared Survey Explorer mid-IR bands which can efficiently select out high-z (z {approx} 2) star-forming galaxies.

  7. The ISO View of Star Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Helou, George

    1999-01-01

    ISO studies of normal galaxies in the local Universe have revealed basic new properties whose significant implications for the star formation process and cosmology are only starting to be understood. This review will touch on the general results of a statistical nature, and provide a quick summary of the profusion of exciting results on individual objects. In the mid-infrared, PHT-S has established that the spectra of star forming galaxies between 6 and-13microns are dominated by the Aromatic Features in Emission (AFE), and show little variation as a function of the heating intensity. The Carriers of the AFE (CAFE) are thus a universal component of dust with standard properties, and contribute between 10 and 25% of the total dust luminosity. In addition to AFE, the spectra show a low-level continuum detectable at wavelengths longer than 3.5microns whose origin is still under investigation. The mid-infrared colors formed as the ratio of flux densities in the 6.75micron and the 15micron bands of ISO-CAM remain essentially constant and near unity for quiescent and mildly active galaxies. As dust heating increases further, the 15micron flux increases steeply compared to 6.75microns, indicating that dust heated to 100K

  8. The ISO View of Star Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Helou, George

    1999-01-01

    ISO studies of normal galaxies in the local Universe have revealed basic new properties whose significant implications for the star formation process and cosmology are only starting to be understood. This review will touch on the general results of a statistical nature, and provide a quick summary of the profusion of exciting results on individual objects. In the mid-infrared, PHT-S has established that the spectra of star forming galaxies between 6 and-13microns are dominated by the Aromatic Features in Emission (AFE), and show little variation as a function of the heating intensity. The Carriers of the AFE (CAFE) are thus a universal component of dust with standard properties, and contribute between 10 and 25% of the total dust luminosity. In addition to AFE, the spectra show a low-level continuum detectable at wavelengths longer than 3.5microns whose origin is still under investigation. The mid-infrared colors formed as the ratio of flux densities in the 6.75micron and the 15micron bands of ISO-CAM remain essentially constant and near unity for quiescent and mildly active galaxies. As dust heating increases further, the 15micron flux increases steeply compared to 6.75microns, indicating that dust heated to 100Kgalaxy become more active in star formation, its [CII] flux weakens relative to total dust emission while the [OI] does not. This behavior has attracted much interest because it extrapolates to the most active galaxies, making them weaker in [CII

  9. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crighton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Schmitt, Benjamin; Sehgal, Neelima; Sievers, Johnathan; Staggs, Suzanne; Swetz, Daniel; Thornton, Robert; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 -1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, A(sub 148-218), of 3.7 (+0.62 or -0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  10. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Duenner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, EriK D.; Wollack, Edward

    2013-01-01

    We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218GHz in the 2008 Southern survey. Flux densities span 14-1700mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148GHz, with the trend continuing to 218GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7+0.62 or -0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  11. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 - 1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7 +0.62/-0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  12. 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)

  13. STAR-FORMING GALAXY EVOLUTION IN NEARBY RICH CLUSTERS

    SciTech Connect

    Tyler, K. D.; Rieke, G. H.; Bai, L.

    2013-08-20

    Dense environments are known to quench star formation in galaxies, but it is still unknown what mechanism(s) are directly responsible. In this paper, we study the star formation of galaxies in A2029 and compare it to that of Coma, combining indicators at 24 {mu}m, H{alpha}, and UV down to rates of 0.03 M{sub Sun} yr{sup -1}. We show that A2029's star-forming galaxies follow the same mass-SFR relation as the field. The Coma cluster, on the other hand, has a population of galaxies with star formation rates (SFRs) significantly lower than the field mass-SFR relation, indicative of galaxies in the process of being quenched. Over half of these galaxies also host active galactic nuclei. Ram-pressure stripping and starvation/strangulation are the most likely mechanisms for suppressing the star formation in these galaxies, but we are unable to disentangle which is dominating. The differences we see between the two clusters' populations of star-forming galaxies may be related to their accretion histories, with A2029 having accreted its star-forming galaxies more recently than Coma. Additionally, many early-type galaxies in A2029 are detected at 24 {mu}m and/or in the far-UV, but this emission is not directly related to star formation. Similar galaxies have probably been classified as star forming in previous studies of dense clusters, possibly obscuring some of the effects of the cluster environment on true star-forming galaxies.

  14. Ammonia thermometry of star-forming galaxies

    SciTech Connect

    Mangum, Jeffrey G.; MacGregor, Meredith; Svoboda, Brian E.; Darling, Jeremy; Henkel, Christian; Menten, Karl M.; Schinnerer, Eva E-mail: mmacgreg@fas.harvard.edu E-mail: jdarling@origins.colorado.edu E-mail: kmenten@mpifr-bonn.mpg.de

    2013-12-10

    With a goal toward deriving the physical conditions in external galaxies, we present a study of the ammonia (NH{sub 3}) emission and absorption in a sample of star-forming systems. Using the unique sensitivities to kinetic temperature afforded by the excitation characteristics of several inversion transitions of NH{sub 3}, we have continued our characterization of the dense gas in star-forming galaxies by measuring the kinetic temperature in a sample of 23 galaxies and one galaxy offset position selected for their high infrared luminosity. We derive kinetic temperatures toward 13 galaxies, 9 of which possess multiple kinetic temperature and/or velocity components. Eight of these galaxies exhibit kinetic temperatures >100 K, which are in many cases at least a factor of two larger than kinetic temperatures derived previously. Furthermore, the derived kinetic temperatures in our galaxy sample, which are in many cases at least a factor of two larger than derived dust temperatures, point to a problem with the common assumption that dust and gas kinetic temperatures are equivalent. As previously suggested, the use of dust emission at wavelengths greater than 160 μm to derive dust temperatures, or dust heating from older stellar populations, may be skewing derived dust temperatures in these galaxies to lower values. We confirm the detection of high-excitation OH {sup 2}Π{sub 3/2} J = 9/2 absorption toward Arp 220. We also report the first detections of non-metastable NH{sub 3} inversion transitions toward external galaxies in the (2,1) (NGC 253, NGC 660, IC 342, and IC 860), (3,1), (3,2), (4,3), (5,4) (all in NGC 660), and (10,9) (Arp 220) transitions.

  15. Nebular excitation in z ∼ 2 star-forming galaxies from the SINS and LUCI surveys: The influence of shocks and active galactic nuclei

    SciTech Connect

    Newman, Sarah F.; Genzel, Reinhard; Buschkamp, Peter; Förster Schreiber, Natascha M.; Kurk, Jaron; Rosario, David; Davies, Ric; Eisenhauer, Frank; Lutz, Dieter; Sternberg, Amiel; Gnat, Orly; Mancini, Chiara; Renzini, Alvio; Lilly, Simon J.; Carollo, C. Marcella; Burkert, Andreas; Cresci, Giovanni; Genel, Shy; Shapiro Griffin, Kristen; Hicks, Erin K. S.; and others

    2014-01-20

    Based on high-resolution, spatially resolved data of 10 z ∼ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the 'composite' region of the z ∼ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ∼ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ∼ 2 mass-metallicity relation (i.e., to the mass they would have at z ∼ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration.

  16. Star-forming galaxy models: Blending star formation into TREESPH

    NASA Technical Reports Server (NTRS)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  17. Using Cosmic Telescopes to Study Dusty, Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Walth, Gregory; Egami, Eiichi; Clément, Benjamin; Rujopakarn, Wiphu; Rawle, Tim; Rex, Marie; Richard, Johan; Dessauges, Miroslava; Perez-Gonzalez, Pablo; Stark, Daniel; Herschel Lensing Survey

    2016-06-01

    Dusty, star-forming galaxies (DSFGs), characterized by their far-infrared (far-IR) emission, undergo the largest starbursts in the Universe, contributing to the majority of the cosmic star formation rate density at z = 1 ‑ 4. These starbursts have important implications for galaxy evolution and feedback as these galaxies build up much of their stellar mass during this time and may experience strong stellar driven winds. For the first time the Herschel Space Observatory was able observe the full far-IR dust emission for a large population of high-redshift DSFGs. However, Herschel reaches the confusion limit quickly and only the brightest galaxies at redshifts z > 2 can be detected. With gravitational lensing, we are able to surpass the Herschel confusion limit and probe intrinsically less luminous and therefore more normal star-forming galaxies. With this goal in mind, we have conducted a large Herschel survey, the Herschel Lensing Survey, of the cores of almost 600 massive galaxy clusters, where the effects of gravitational lensing are the strongest. In this presentation I will discuss how using one of largest gravitational lenses enables the detailed study of star forming regions at high redshift by investigating a giant (D ~ 1 kpc) luminous star forming region in aDSFG at z=0.6. Next, I will discuss how using one of the brightest sources from our sample allows us to investigate the molecular gas and dust properties of a typical DSFG with a CO outflow at z~2. Finally, I will discuss ongoing work using the brightest DSFGs in our sample to detect rest-frame optical nebular emission lines, using near-infrared spectroscopy with Keck/MOSFIRE, LBT/LUCI, and Magellan/MMIRS, which reveal conditions of their ISM; specifically ionization, star formation, metallicity, AGN activity, and dust attenuation.

  18. Using Cosmic Telescopes to Study Dusty, Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Walth, Gregory; Egami, Eiichi; Clément, Benjamin; Rujopakarn, Wiphu; Rawle, Tim; Rex, Marie; Richard, Johan; Dessauges, Miroslava; Perez-Gonzalez, Pablo; Stark, Daniel; Herschel Lensing Survey

    2016-06-01

    Dusty, star-forming galaxies (DSFGs), characterized by their far-infrared (far-IR) emission, undergo the largest starbursts in the Universe, contributing to the majority of the cosmic star formation rate density at z = 1 - 4. These starbursts have important implications for galaxy evolution and feedback as these galaxies build up much of their stellar mass during this time and may experience strong stellar driven winds. For the first time the Herschel Space Observatory was able observe the full far-IR dust emission for a large population of high-redshift DSFGs. However, Herschel reaches the confusion limit quickly and only the brightest galaxies at redshifts z > 2 can be detected. With gravitational lensing, we are able to surpass the Herschel confusion limit and probe intrinsically less luminous and therefore more normal star-forming galaxies. With this goal in mind, we have conducted a large Herschel survey, the Herschel Lensing Survey, of the cores of almost 600 massive galaxy clusters, where the effects of gravitational lensing are the strongest. In this presentation I will discuss how using one of largest gravitational lenses enables the detailed study of star forming regions at high redshift by investigating a giant (D ~ 1 kpc) luminous star forming region in aDSFG at z=0.6. Next, I will discuss how using one of the brightest sources from our sample allows us to investigate the molecular gas and dust properties of a typical DSFG with a CO outflow at z~2. Finally, I will discuss ongoing work using the brightest DSFGs in our sample to detect rest-frame optical nebular emission lines, using near-infrared spectroscopy with Keck/MOSFIRE, LBT/LUCI, and Magellan/MMIRS, which reveal conditions of their ISM; specifically ionization, star formation, metallicity, AGN activity, and dust attenuation.

  19. An atlas of ultraviolet spectra of star-forming galaxies

    NASA Technical Reports Server (NTRS)

    Kinney, A. L.; Bohlin, R. C.; Calzetti, D.; Panagia, N.; Wyse, Rosemary F. G.

    1993-01-01

    A systematic study is presented of the UV spectra of star-forming galaxies of different morphological type and activity class using a sample drawn from a uniformly reduced IUE data set. The spectra for a wide variety of galaxies, including normal spiral, LINER, starburst, blue compact, blue compact dwarf, and Seyfert 2 galaxies, are presented in the form of spectral energy distributions to demonstrate the overall characteristics according to morphology and activity class and in the form of absolute flux distributions to better show the absorption and emission features of individual objects. The data support the picture based on UV spectra of the Orbiting Astronomical Observatory and of the Astronautical Netherlands Satellite that spiral galaxies of later Hubble class have more flux at the shortest UV wavelengths than do spiral galaxies of earlier Hubble class.

  20. Nebular Excitation in z ~ 2 Star-forming Galaxies from the SINS and LUCI Surveys: The Influence of Shocks and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Newman, Sarah F.; Buschkamp, Peter; Genzel, Reinhard; Förster Schreiber, Natascha M.; Kurk, Jaron; Sternberg, Amiel; Gnat, Orly; Rosario, David; Mancini, Chiara; Lilly, Simon J.; Renzini, Alvio; Burkert, Andreas; Carollo, C. Marcella; Cresci, Giovanni; Davies, Ric; Eisenhauer, Frank; Genel, Shy; Shapiro Griffin, Kristen; Hicks, Erin K. S.; Lutz, Dieter; Naab, Thorsten; Peng, Yingjie; Tacconi, Linda J.; Wuyts, Stijn; Zamorani, Gianni; Vergani, Daniela; Weiner, Benjamin J.

    2014-01-01

    Based on high-resolution, spatially resolved data of 10 z ~ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the "composite" region of the z ~ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ~ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ~ 2 mass-metallicity relation (i.e., to the mass they would have at z ~ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration. Based on observations at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDs 073.B-9018, 076.A-0527, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 083.A-0781,084.A-0853, 087.A-0081, 091.A.-0126) and at the Large Binocular Telescope (LBT) on Mt. Graham in Arizona.

  1. Modeling abundances in star forming galaxies

    NASA Astrophysics Data System (ADS)

    Kobayashi, Chiaki

    2015-08-01

    Heavy elements are produced from various types of supernovae (and AGB stars). I first show that elemental abundances of extremely metal-poor stars are consistent not with pair-instability supernovae but with faint supernovae. Then I introduce subclasses of Type Ia supernovae such as SN 2002cx-like objects and sub-Chandrasekhar mass explosions. These "minor" supernovae are important in the early Universe or metal-poor systems such as dwarf spheroidal galaxies. With "major" chemical enrichment sources, I show cosmic chemical enrichment in our cosmological, hydrodynamical simulations. The feedback from active galactic nuclei (AGN) is also included with a new model for the formation of black holes motivated by the first star formation. AGN-driven outflows transport metals into the circumgalactic medium and the intergalactic medium. Nonetheless, the metallicity changes of galaxies are negligible, and the mass-metallicity relations, which are mainly generated by supernova feedback at the first star burst, are preserved. Within galaxies, metallicity radial gradients are produced, which can be affected by AGN feedback but are more sensitive to the merging histories. We find a weak correlation between the gradients and galaxy mass, which is consistent with available observations. These simulations also provide predictions of supernova/hypernova/GRB rates and the properties of their host galaxies.

  2. Characterising molecular gas in nearby star forming galaxies

    NASA Astrophysics Data System (ADS)

    Kelly, George; Viti, Serena; Garcia-Burillo, Santiago

    2015-08-01

    Regions of very dense, star-forming gas in the interstellar medium are necessary to maintain star formation activity in hostile conditions. Star-forming regions in these environments are able to resist winds and radiative forces from newly formed stars longer than gas in the surrounding ISM. Subject to a proper interpretation, observations of molecules can be used for many purposes: tracing the reservoir or leftover of the star formation process; tracing the process of star formation itself; and determining the galaxy energetics through influence of newly-formed stars or an AGN on their environments. We map the distribution of several tracer molecules over three nearby galaxies. We begin by mapping two starburst galaxies with single dish observations of the dense gas tracer CS. The formation of CS is modelled under different conditions with results fed into a molecular line radiative transfer model. From this we can obtain the physical conditions of the regions of the ISM where there is a high rate of star-formation, as well as compare how the conditions vary away from the galactic centre. Moving on from here, we use ALMA to map NGC 1068. Observations of several molecules across the AGN and starburst regions are used to determine conditions and processes with a spatial resolution of less than 35 parsecs.

  3. Evidence for wide-spread active galactic nucleus-driven outflows in the most massive z ∼ 1-2 star-forming galaxies

    SciTech Connect

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Burkert, A.; Buschkamp, P.; Chan, J.; Brammer, G. E-mail: genzel@mpe.mpg.de; and others

    2014-11-20

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M {sub *}/M {sub ☉}) ≥ 10.9) z ∼ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M {sub *}/M {sub ☉}) ≥ 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS{sup 3D}spectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ∼450-5300 km s{sup –1}), with large [N II]/Hα ratios, above log(M {sub *}/M {sub ☉}) ∼ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ∼ 1 and ∼2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.

  4. The Mid-infrared High-ionization Lines from Active Galactic Nuclei and Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Pereira-Santaella, Miguel; Diamond-Stanic, Aleksandar M.; Alonso-Herrero, Almudena; Rieke, George H.

    2010-12-01

    We used Spitzer/Infrared Spectrograph spectroscopic data on 426 galaxies including quasars, Seyferts, LINERs, and H II galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne V]14.3 μm and 24.3 μm (97.1 eV) and the [O IV]25.9 μm (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne III]15.56 μm (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne III] excess due to star formation in Seyfert galaxies. We also estimated the [O IV] luminosity due to star formation in active galaxies and determined that it dominates the [O IV] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the active galactic nucleus dominates the [O IV] emission in most Seyfert galaxies, whereas star formation adequately explains the observed [O IV] emission in optically classified H II galaxies. Finally, we computed photoionization models to determine the physical conditions of the narrow-line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log n H (cm-2) < 21. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407.

  5. Extreme Dust Heating in Optically Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    O'Connor, Jessica

    A complete census of supermassive black holes in the local universe is important, especially in low mass (log(stellar mass/solar masses) < 10) galaxies. It provides observational constraints on the black hole occupation fractions of low mass galaxies and broadens our understanding of the co-evolution of active galactic nuclei (AGN) and their host galaxies. Infrared selection criteria including [3.4]-[4.6] micron (W1-W2) color provides a useful method for detecting obscured AGN which may be missed in X-ray or optical surveys. Recent work has found that not only are there more AGN in low mass galaxies than would be predicted using optical selection criteria, but that the fraction of high W1-W2 (>0.5) galaxies is actually highest in the lowest mass galaxies. This could be evidence of a significant population of obscured AGN in low mass galaxies, but it is still unclear whether the dust heating that causes high W1-W2 color can only be caused by AGN or if stars alone are sufficient. This dissertation is a study of the demographics of high W1-W2 galaxies in the local universe and the AGN or star-forming nature of their nuclear activity. First, the number density of z0.3, 0.5 and 0.8 are calculated as a function of r-band luminosity and stellar mass. Not only does the number density of high W1-W2 galaxies rise toward the lowest host mass regime in stark contrast to the mass distribution of optical AGN, but the red WISE population displays a bimodality in its luminosity and stellar mass functions. They are a combination of a high mass optical AGN and a low mass optically star-forming component. One optically normal, IR-red (W1-W2>1) galaxy (SDSS J1224+5555) was included in a pilot study of bulgeless, high W1-W2 galaxies which found that its X-ray flux is much lower than would be expected if it hosted an AGN. Decomposing its photometry with multiwavelength spectral energy distribution (SED) modeling revealed that it is impossible to reproduce the galaxy's mid

  6. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Star-forming Galaxies from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine S.; Hainline, Kevin N.; DiPompeo, Michael A.; Goulding, Andy D.

    2016-07-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous work suggesting that young galaxies in optical surveys have an observed lognormal Eddington ratio distribution. We simulate the optical emission line properties of a population of galaxies and AGNs using a broad, instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observed galaxies via their positions on an emission line excitation diagram and Eddington ratio distributions. We present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that for optically selected AGNs in young galaxies, the intrinsic Eddington ratio distribution is consistent with a possibly universal, broad power law with an exponential cutoff, as this distribution is observed in old, optically selected galaxies and X-rays.

  7. Evidence for Wide-spread Active Galactic Nucleus-driven Outflows in the Most Massive z ~ 1-2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Brammer, G.; Burkert, A.; Buschkamp, P.; Chan, J.; Carollo, C. M.; Davies, R.; Eisenhauer, F.; Fabricius, M.; Fossati, M.; Kriek, M.; Kulkarni, S.; Lilly, S. J.; Mancini, C.; Momcheva, I.; Naab, T.; Nelson, E. J.; Renzini, A.; Saglia, R.; Sharples, R. M.; Sternberg, A.; Tacchella, S.; van Dokkum, P.

    2014-11-01

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M */M ⊙) >= 10.9) z ~ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M */M ⊙) >= 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS3Dspectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ~450-5300 km s-1), with large [N II]/Hα ratios, above log(M */M ⊙) ~ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ~ 1 and ~2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation. Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDs 073.B-9018, 074.A-9011, 075.A-0466, 076.A-0527, 078.A-0660, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 081.A-0672, 082.A-0396, 183.A-0781, 087.A-0081, 088.A-0202, 088.A-0209, 091.A-0126, 092.A-0082, 092.A-0091, 093.A-0079). Also based on observations at the Large Binocular Telescope (LBT) on Mt. Graham in Arizona.

  8. Optical Color Gradients in Star-forming Ring Galaxies

    NASA Astrophysics Data System (ADS)

    Korchagin, Vladimir; Mayya, Y. D.; Vorobyov, Eduard

    2001-06-01

    We compute radial color gradients produced by an outwardly propagating circular wave of star formation and compare our results with color gradients observed in the classical ring galaxy, the ``Cartwheel.'' We invoke two independent models of star formation in the ring galaxies. The first one is the conventional density wave scenario, in which an intruder galaxy creates a radially propagating density wave accompanied by an enhanced star formation following the Schmidt's law. The second scenario is a pure self-propagating star formation model, in which the intruder sets off only the first burst of stars at the point of impact. Both models give essentially the same results. Systematic reddening of B-V, V-K colors toward the center, such as that observed in the Cartwheel, can be obtained only if the abundance of heavy elements in the star-forming gas is a few times below solar. The B-V and V-K color gradients observed in the Cartwheel can be explained as a result of mixing of stellar populations born in a star-forming wave propagating through a low-metallicity gaseous disk, and a preexisting stellar disk of the size of the gaseous disk with color properties typical to those observed in nearby disk galaxies.

  9. Gas inflow and metallicity drops in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel; Sánchez Almeida, Jorge; Muñoz Tuñón, Casiana; Dekel, Avishai; Elmegreen, Bruce G.; Elmegreen, Debra M.; Primack, Joel

    2016-04-01

    Gas inflow feeds galaxies with low-metallicity gas from the cosmic web, sustaining star formation across the Hubble time. We make a connection between these inflows and metallicity inhomogeneities in star-forming galaxies, by using synthetic narrow-band images of the Hα emission line from zoom-in AMR cosmological simulations of galaxies with stellar masses of M* ≃ 109 M⊙ at redshifts z = 2-7. In ˜50 per cent of the cases at redshifts lower than 4, the gas inflow gives rise to star-forming, Hα-bright, off-centre clumps. Most of these clumps have gas metallicities, weighted by Hα luminosity, lower than the metallicity in the surrounding interstellar medium by ˜0.3 dex, consistent with observations of chemical inhomogeneities at high and low redshifts. Due to metal mixing by shear and turbulence, these metallicity drops are dissolved in a few disc dynamical times. Therefore, they can be considered as evidence for rapid gas accretion coming from cosmological inflow of pristine gas.

  10. Kinematic evolution of simulated star-forming galaxies

    SciTech Connect

    Kassin, Susan A.; Brooks, Alyson; Governato, Fabio; Weiner, Benjamin J.; Gardner, Jonathan P.

    2014-08-01

    Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last ∼8 billion years since z = 1.2, undergoing a process of 'disk settling'. For the first time, we study the kinematic evolution of a suite of four state of the art 'zoom in' hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking because the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (σ{sub g}) and increase in ordered rotation (V{sub rot}) with time. The slopes of the relations between both σ{sub g} and V{sub rot} with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling'.

  11. Kinematic Evolution of Simulated Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Kassin, Susan A.; Brooks, Alyson; Governato, Fabio; Weiner, Benjamin J.; Gardner, Jonathan P.

    2014-08-01

    Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last ~8 billion years since z = 1.2, undergoing a process of "disk settling." For the first time, we study the kinematic evolution of a suite of four state of the art "zoom in" hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking because the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (σ g ) and increase in ordered rotation (V rot) with time. The slopes of the relations between both σ g and V rot with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling.

  12. Kinematic Evolution of Simulated Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Kassin, Susan A.; Brooks, Alyson; Governato, Fabio; Weiner, Benjamin J.; Gardner, Jonathan P.

    2014-01-01

    Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last approximately 8 billion years since z = 1.2, undergoing a process of "disk settling." For the first time, we study the kinematic evolution of a suite of four state of the art "zoom in" hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking as the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (sigma(sub g)) and increase in ordered rotation (V(sub rot)) with time. The slopes of the relations between both sigma(sub g) and V(sub rot) with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling.

  13. ASSESSING RADIATION PRESSURE AS A FEEDBACK MECHANISM IN STAR-FORMING GALAXIES

    SciTech Connect

    Andrews, Brett H.; Thompson, Todd A.

    2011-02-01

    Radiation pressure from the absorption and scattering of starlight by dust grains may be an important feedback mechanism in regulating star-forming galaxies. We compile data from the literature on star clusters, star-forming subregions, normal star-forming galaxies, and starbursts to assess the importance of radiation pressure on dust as a feedback mechanism, by comparing the luminosity and flux of these systems to their dust Eddington limit. This exercise motivates a novel interpretation of the Schmidt law, the L{sub IR}-L'{sub CO} correlation, and the L{sub IR}-L'{sub HCN} correlation. In particular, the linear L{sub IR}-L'{sub HCN} correlation is a natural prediction of radiation pressure regulated star formation. Overall, we find that the Eddington limit sets a hard upper bound to the luminosity of any star-forming region. Importantly, however, many normal star-forming galaxies have luminosities significantly below the Eddington limit. We explore several explanations for this discrepancy, especially the role of 'intermittency' in normal spirals-the tendency for only a small number of subregions within a galaxy to be actively forming stars at any moment because of the time dependence of the feedback process and the luminosity evolution of the stellar population. If radiation pressure regulates star formation in dense gas, then the gas depletion timescale is 6 Myr, in good agreement with observations of the densest starbursts. Finally, we highlight the importance of observational uncertainties, namely, the dust-to-gas ratio and the CO-to-H{sub 2} and HCN-to-H{sub 2} conversion factors, that must be understood before a definitive assessment of radiation pressure as a feedback mechanism in star-forming galaxies.

  14. Assessing Radiation Pressure as a Feedback Mechanism in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Andrews, Brett H.; Thompson, Todd A.

    2011-02-01

    Radiation pressure from the absorption and scattering of starlight by dust grains may be an important feedback mechanism in regulating star-forming galaxies. We compile data from the literature on star clusters, star-forming subregions, normal star-forming galaxies, and starbursts to assess the importance of radiation pressure on dust as a feedback mechanism, by comparing the luminosity and flux of these systems to their dust Eddington limit. This exercise motivates a novel interpretation of the Schmidt law, the L IR-L'CO correlation, and the L IR-L'HCN correlation. In particular, the linear L IR-L'HCN correlation is a natural prediction of radiation pressure regulated star formation. Overall, we find that the Eddington limit sets a hard upper bound to the luminosity of any star-forming region. Importantly, however, many normal star-forming galaxies have luminosities significantly below the Eddington limit. We explore several explanations for this discrepancy, especially the role of "intermittency" in normal spirals—the tendency for only a small number of subregions within a galaxy to be actively forming stars at any moment because of the time dependence of the feedback process and the luminosity evolution of the stellar population. If radiation pressure regulates star formation in dense gas, then the gas depletion timescale is 6 Myr, in good agreement with observations of the densest starbursts. Finally, we highlight the importance of observational uncertainties, namely, the dust-to-gas ratio and the CO-to-H2 and HCN-to-H2 conversion factors, that must be understood before a definitive assessment of radiation pressure as a feedback mechanism in star-forming galaxies.

  15. THE CLUSTERING AND HALO MASSES OF STAR-FORMING GALAXIES AT z < 1

    SciTech Connect

    Dolley, Tim; Brown, Michael J. I.; Pimbblet, Kevin A.; Palamara, David P.; Beare, Richard; Weiner, Benjamin J.; Jannuzi, Buell T.; Brodwin, Mark; Kochanek, C. S.; Dey, Arjun; Atlee, David W.

    2014-12-20

    We present clustering measurements and halo masses of star-forming galaxies at 0.2 < z < 1.0. After excluding active galactic nuclei (AGNs), we construct a sample of 22,553 24 μm sources selected from 8.42 deg{sup 2} of the Spitzer MIPS AGN and Galaxy Evolution Survey of Boötes. Mid-infrared imaging allows us to observe galaxies with the highest star formation rates (SFRs), less biased by dust obscuration afflicting the optical bands. We find that the galaxies with the highest SFRs have optical colors that are redder than typical blue cloud galaxies, with many residing within the green valley. At z > 0.4 our sample is dominated by luminous infrared galaxies (LIRGs, L {sub TIR} > 10{sup 11} L {sub ☉}) and is composed entirely of LIRGs and ultraluminous infrared galaxies (ULIRGs, L {sub TIR} > 10{sup 12} L {sub ☉}) at z > 0.6. We observe weak clustering of r {sub 0} ≈ 3-6 h {sup –1} Mpc for almost all of our star-forming samples. We find that the clustering and halo mass depend on L {sub TIR} at all redshifts, where galaxies with higher L {sub TIR} (hence higher SFRs) have stronger clustering. Galaxies with the highest SFRs at each redshift typically reside within dark matter halos of M {sub halo} ≈ 10{sup 12.9} h {sup –1} M {sub ☉}. This is consistent with a transitional halo mass, above which star formation is largely truncated, although we cannot exclude that ULIRGs reside within higher mass halos. By modeling the clustering evolution of halos, we connect our star-forming galaxy samples to their local descendants. Most star-forming galaxies at z < 1.0 are the progenitors of L ≲ 2.5 L {sub *} blue galaxies in the local universe, but star-forming galaxies with the highest SFRs (L {sub TIR} ≳ 10{sup 11.7} L {sub ☉}) at 0.6 < z < 1.0 are the progenitors of early-type galaxies in denser group environments.

  16. Boxy Hα emission profiles in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Yan-Mei; Gu, Qiu-Sheng; Tremonti, Christy A.; Shi, Yong; Jin, Yifei

    2016-07-01

    We assemble a sample of disc star-forming galaxies from the Sloan Digital Sky Survey Data Release 7, studying the structure of Hα emission lines, finding a large fraction of this sample contains boxy Hα line profiles. This fraction depends on galaxy physical and geometric parameters in the following way: (1) it increases monotonically with star formation rate per unit area (ΣSFR), and stellar mass (M*), with the trend being much stronger with M*, from ˜0 per cent at M* = 1010 M⊙ to about 50 per cent at M* = 1011 M⊙; (2) the fraction is much smaller in face-on systems than in edge-on systems. It increases with galaxy inclination (i) while i < 60° and is roughly a constant of 25 per cent beyond this range; (3) for the sources which can be modelled well with two velocity components, blueshifted and redshifted from the systemic velocity, these is a positive correlation between the velocity difference of these two components and the stellar mass, with a slope similar to the Tully-Fisher relation; (4) the two components are very symmetric in the mean, both in velocity and in amplitude. The four findings listed above can be understood as a natural result of a rotating galaxy disc with a kpc-scale ring-like Hα emission region.

  17. Locating star-forming regions in quasar host galaxies

    NASA Astrophysics Data System (ADS)

    Young, J. E.; Eracleous, M.; Shemmer, O.; Netzer, H.; Gronwall, C.; Lutz, Dieter; Ciardullo, R.; Sturm, Eckhard

    2014-02-01

    We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II]λ3727, Hβ, [O III]λ5007 and Paα images, taken with the Wide Field Planetary Camera 2 and NICMOS instruments, to map the morphology of line-emitting regions, and, after extinction corrections, diagnose the excitation mechanism and infer star-formation rates. Significant challenges in this type of work are the separation of the quasar light from the stellar continuum and the quasar-excited gas from the star-forming regions. To this end, we present a novel technique for image decomposition and subtraction of quasar light. Our primary result is the detection of extended line-emitting regions with sizes ranging from 0.5 to 5 kpc and distributed symmetrically around the nucleus, powered primarily by star formation. We determine star-formation rates of the order of a few tens of M⊙ yr-1. The host galaxies of our target quasars have stellar masses of the order of 1011 M⊙ and specific star-formation rates on a par with those of M82 and luminous infrared galaxies. As such they fall at the upper envelope or just above the star-formation mass sequence in the specific star formation versus stellar mass diagram. We see a clear trend of increasing star-formation rate with quasar luminosity, reinforcing the link between the growth of the stellar mass of the host and the black hole mass found by other authors.

  18. The SINS/zC-SINF survey of z ∼ 2 galaxy kinematics: Evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies

    SciTech Connect

    Förster Schreiber, N. M.; Genzel, R.; Kurk, J. D.; Lutz, D.; Tacconi, L. J.; Wuyts, S.; Bandara, K.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Lang, P.; Newman, S. F.; Burkert, A.; Carollo, C. M.; Lilly, S. J.; Cresci, G.; Daddi, E.; Mainieri, V.; Mancini, C.; and others

    2014-05-20

    We report the detection of ubiquitous powerful nuclear outflows in massive (≥10{sup 11} M {sub ☉}) z ∼ 2 star-forming galaxies (SFGs), which are plausibly driven by an active galactic nucleus (AGN). The sample consists of the eight most massive SFGs from our SINS/zC-SINF survey of galaxy kinematics with the imaging spectrometer SINFONI, six of which have sensitive high-resolution adaptive optics-assisted observations. All of the objects are disks hosting a significant stellar bulge. The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM ∼ 1500 km s{sup –1}, [N II]/Hα ratio ≈ 0.6, and intrinsic extent of 2-3 kpc. These properties are consistent with warm ionized gas outflows associated with Type 2 AGN, the presence of which is confirmed via independent diagnostics in half the galaxies. The data imply a median ionized gas mass outflow rate of ∼60 M {sub ☉} yr{sup –1} and mass loading of ∼3. At larger radii, a weaker broad component is detected but with lower FWHM ∼485 km s{sup –1} and [N II]/Hα ≈ 0.35, characteristic for star formation-driven outflows as found in the lower-mass SINS/zC-SINF galaxies. The high inferred mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Larger samples at high masses will be crucial in confirming the importance and energetics of the nuclear outflow phenomenon and its connection to AGN activity and bulge growth.

  19. 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.

  20. Mass-metallicity relation for local star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Zhong; Zhang, Shuang-Nan; Zhao, Yong-Heng; Zhang, Wei

    2016-04-01

    We investigate the evolution of the mass-metallicity (M-Z) relation with a large sample of 53 444 star-forming galaxies (SFGs) at 0.04 < z < 0.12, selected from the catalogue of Max-Planck-Institute for Astrophysics-John Hopkins University (MPA-JHU) emission-line measurements for the Sloan Digital Sky Survey Data Release 7. Regarding the sample of SFGs, we correct the observational bias and raise the aperture covering fractions to check the reliability of the metallicity evolution. (i) We show that the redshift evolution of the log (Hα) and log([O III]) luminosities is displayed in our sample. (ii) We find the metallicity evolution of ˜0.15 dex at log (M*/M⊙) ˜ 9.3 in SFGs at 0.04 < z < 0.12. (iii) After applying the luminosity thresholds of log (LHα) > 41.0 and log (L_[O III])>39.7, we find that the metallicity evolution is shown well, and that the evolution of the star formation rate (SFR) is still shown well under the latter luminosity threshold, but the evolution is not observed under the former. (iv) The evolution of the M-Z relation seems to disappear at about log (M*/M⊙) > 10.0 after applying the luminosity threshold of log (LHα) > 41.0 or log (L_[O III])>39.7. (v) We find α = 0.09 and α = 0.07 in the equation, μ = log M* - αlog (SFR), for log (LHα) > 41.0 and log (L_[O III])>39.7 samples, respectively, and these imply that the evolution of the M-Z relation might have a weaker dependence on the SFR in our sample.

  1. A CORRELATION BETWEEN STAR FORMATION RATE AND AVERAGE BLACK HOLE ACCRETION IN STAR-FORMING GALAXIES

    SciTech Connect

    Chen, Chien-Ting J.; Hickox, Ryan C.; Alberts, Stacey; Pope, Alexandra; Brodwin, Mark; Jones, Christine; Forman, William R.; Goulding, Andrew D.; Murray, Stephen S.; Alexander, David M.; Mullaney, James R.; Assef, Roberto J.; Gorjian, Varoujan; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell T.; Le Floc'h, Emeric

    2013-08-10

    We present a measurement of the average supermassive black hole accretion rate (BHAR) as a function of the star formation rate (SFR) for galaxies in the redshift range 0.25 < z < 0.8. We study a sample of 1767 far-IR-selected star-forming galaxies in the 9 deg{sup 2} Booetes multi-wavelength survey field. The SFR is estimated using 250 {mu}m observations from the Herschel Space Observatory, for which the contribution from the active galactic nucleus (AGN) is minimal. In this sample, 121 AGNs are directly identified using X-ray or mid-IR selection criteria. We combined these detected AGNs and an X-ray stacking analysis for undetected sources to study the average BHAR for all of the star-forming galaxies in our sample. We find an almost linear relation between the average BHAR (in M{sub Sun} yr{sup -1}) and the SFR (in M{sub Sun} yr{sup -1}) for galaxies across a wide SFR range 0.85 < log SFR < 2.56: log BHAR = (- 3.72 {+-} 0.52) + (1.05 {+-} 0.33)log SFR. This global correlation between SFR and average BHAR is consistent with a simple picture in which SFR and AGN activity are tightly linked over galaxy evolution timescales.

  2. The Connection Between Galaxy Environment and the Luminosity Function Slopes of Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David A.; Calzetti, Daniela; Kennicutt, Robert

    2016-06-01

    We present the first study of GALEX far ultra-violet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ~65,000 star-forming regions (i.e., FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of \

  3. The nature of Hα-selected galaxies at z > 2. II. Clumpy galaxies and compact star-forming galaxies

    SciTech Connect

    Tadaki, Ken-ichi; Kodama, Tadayuki; Koyama, Yusei; Tanaka, Ichi; Hayashi, Masao; Shimakawa, Rhythm

    2014-01-01

    We present the morphological properties of Hα-selected galaxies at z > 2 in SXDF-UDS-CANDELS field. With high-resolution optical/near-infrared images obtained by the Hubble Space Telescope, we identify giant clumps within the Hα emitters (HAEs). We find that at least 41% of our sample shows clumpy structures in the underlying disks. The color gradient of clumps is commonly seen in the sense that the clumps near the galactic center tend to be redder than those in the outer regions. The mid-infrared detection in galaxies with red clumps and the spatial distribution of Hα emission suggest that dusty star-formation activity is probably occurring in the nuclear red clumps. A gas supply to a bulge component through clump migration is one of the most potent physical processes for producing such dusty star-forming clumps and forming massive bulges in local early-type galaxies. They would become large quiescent galaxies at later times just by consumption or blowout of remaining gas. Also, while most of the HAEs have extended disks, we observe two massive, compact HAEs whose stellar surface densities are significantly higher. They are likely to be the direct progenitors of massive, compact quiescent galaxies at z = 1.5-2.0. Two evolutionary paths to massive quiescent galaxies are devised to account for both the size growth of quiescent galaxies and their increased number density from z ∼ 2 to z = 0.

  4. Rapid growth of black holes in massive star-forming galaxies.

    PubMed

    Alexander, D M; Smail, I; Bauer, F E; Chapman, S C; Blain, A W; Brandt, W N; Ivison, R J

    2005-04-01

    The tight relationship between the masses of black holes and galaxy spheroids in nearby galaxies implies a causal connection between the growth of these two components. Optically luminous quasars host the most prodigious accreting black holes in the Universe, and can account for greater than or approximately equal to 30 per cent of the total cosmological black-hole growth. As typical quasars are not, however, undergoing intense star formation and already host massive black holes (> 10(8)M(o), where M(o) is the solar mass), there must have been an earlier pre-quasar phase when these black holes grew (mass range approximately (10(6)-10(8))M(o)). The likely signature of this earlier stage is simultaneous black-hole growth and star formation in distant (redshift z > 1; >8 billion light years away) luminous galaxies. Here we report ultra-deep X-ray observations of distant star-forming galaxies that are bright at submillimetre wavelengths. We find that the black holes in these galaxies are growing almost continuously throughout periods of intense star formation. This activity appears to be more tightly associated with these galaxies than any other coeval galaxy populations. We show that the black-hole growth from these galaxies is consistent with that expected for the pre-quasar phase.

  5. Early star-forming galaxies and the reionization of the Universe.

    PubMed

    Robertson, Brant E; Ellis, Richard S; Dunlop, James S; McLure, Ross J; Stark, Daniel P

    2010-11-01

    Star-forming galaxies trace cosmic history. Recent observational progress with the NASA Hubble Space Telescope has led to the discovery and study of the earliest known galaxies, which correspond to a period when the Universe was only ∼800 million years old. Intense ultraviolet radiation from these early galaxies probably induced a major event in cosmic history: the reionization of intergalactic hydrogen.

  6. VizieR Online Data Catalog: Star-forming galaxies in near-IR (Martins+, 2013)

    NASA Astrophysics Data System (ADS)

    Martins, L. P.; Rodriguez-Ardila, A.; Diniz, S.; Riffel, R.; de Souza, R.

    2014-10-01

    The sample used here was presented in Martins et al. (2013MNRAS.431.1823M) and is a subset of the one presented in the magnitude-limited optical spectroscopic survey of nearby bright galaxies of Ho, Filippenko & Sargent (1995, Cat. J/ApJS/98/477, hereafter HO95). These galaxies are sources defined by Ho, Filippenko & Sargent (1997, Cat. J/ApJS/112/315, hereafter HO97) as those composed of 'nuclei dominated by emission lines from regions of active star formation (HII or starburst nuclei)'. In addition, five galaxies, classified as non-star forming in the optical, dominated by old stellar population and with no detected emission lines, were included as a control sample. All spectra were obtained at the NASA 3m Infrared Telescope Facility (IRTF) in two observing runs (2007 and 2008) - the same data from Martins et al. (2013MNRAS.431.1823M). (2 data files).

  7. FROM BLUE STAR-FORMING TO RED PASSIVE: GALAXIES IN TRANSITION IN DIFFERENT ENVIRONMENTS

    SciTech Connect

    Vulcani, Benedetta; Poggianti, Bianca M.; Fasano, Giovanni; Moretti, Alessia; Fritz, Jacopo; Calvi, Rosa; Paccagnella, Angela

    2015-01-01

    Exploiting a mass-complete (M {sub *} > 10{sup 10.25} M {sub ☉}) sample at 0.03 Galaxy Group Catalog, we use the (U – B) {sub rf} color and morphologies to characterize galaxies, in particular those that show signs of an ongoing or recent transformation of their star-formation activity and/or morphology: green galaxies, red passive late types, and blue star-forming early types. Color fractions depend on mass and only for M {sub *} < 10{sup 10.7} M {sub ☉} on environment. The incidence of red galaxies increases with increasing mass, and, for M {sub *} < 10{sup 10.7} M {sub ☉}, decreases toward the group outskirts and in binary and single galaxies. The relative abundance of green and blue galaxies is independent of environment and increases monotonically with galaxy mass. We also inspect galaxy structural parameters, star-formation properties, histories, and ages and propose an evolutionary scenario for the different subpopulations. Color transformations are due to a reduction and suppression of the star-formation rate in both bulges and disks that does not noticeably affect galaxy structure. Morphological transitions are linked to an enhanced bulge-to-disk ratio that is due to the removal of the disk, not to an increase of the bulge. Our modeling suggests that green colors might be due to star-formation histories declining with long timescales, as an alternative scenario to the classical ''quenching'' processes. Our results suggest that galaxy transformations in star-formation activity and morphology depend neither on the environment nor on being a satellite or the most massive galaxy of a halo. The only environmental dependence we find is the higher fast quenching efficiency in groups giving origin to poststarburst signatures.

  8. Revealing the nature of star forming blue early-type galaxies at low redshift

    NASA Astrophysics Data System (ADS)

    George, Koshy; Zingade, Kshama

    2015-11-01

    Context. Star forming early-type galaxies with blue optical colours at low redshift can be used to test our current understanding of galaxy formation and evolution. Aims: We want to reveal the fuel and triggering mechanism for star formation in these otherwise passively evolving red and dead stellar systems. Methods: We undertook an optical and ultraviolet study of 55 star forming blue early-type galaxies, searching for signatures of recent interactions that could be driving the molecular gas into the galaxy and potentially triggering the star formation. Results: We report here our results on star forming blue early-type galaxies with tidal trails and in close proximity to neighbouring galaxies that are evidence of ongoing or recent interactions between galaxies. There are 12 galaxies with close companions with similar redshifts, among which two galaxies are having ongoing interactions that potentially trigger the star formation. Two galaxies show a jet feature that could be due to the complete tidal disruption of the companion galaxy. The interacting galaxies have high star formation rates and very blue optical colours. Galaxies with no companion could have undergone a minor merger in the recent past. Conclusions: The recent or ongoing interaction with a gas-rich neighbouring galaxy could be responsible for bringing cold gas to an otherwise passively evolving early-type galaxy. The sudden gas supply could trigger the star formation, eventually creating a blue early-type galaxy. The galaxies with ongoing tidal interaction are blue and star forming, thereby implying that blue early-type galaxies can exist even when the companion is on flyby so does not end up in a merger. Based on data compiled from Galaxy Zoo project, and the volunteers contribution are acknowledged at http://www.galaxyzoo.org/Volunteers.aspx

  9. Galactic Winds and Structure of z ~ 2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Newman, Sarah F.

    Galactic-scale outflows are a key driver of galaxy evolution through their feedback effect on star-formation and their ejection of metals and energy into the inter-galactic medium (IGM). While it is known that outflows likely play an important role in the quenching of star-formation - transforming actively star-forming, blue galaxies into their 'red and dead' counterparts - this role is currently not well understood. In particular, at z ˜ 2, during the most active epoch of star-formation, the mass and energy in these outflows is poorly constrained, as is the mechanism for launching them. Furthermore, active-galactic nuclei (AGN) in the centers of massive star-forming galaxies (SFGs) likely play an important role in star-formation quenching, but we do not have a clear understanding of how this AGN feedback compares with that of star-formation driven feedback, and it is not known how many of these massive SFGs at z ˜ 2 even have AGN. This issue is complicated by the fact that many high-z AGN are likely highly obscured, and have strong nebular emission line contributions from both star-formation and the AGN. In this dissertation, I explore these issues using high-spatial and spectral resolution integral field unit spectroscopic data of z ˜ 2 SFGs. The observations are obtained with the instrument SINFONI on the European Southern Observatory (ESO) Very Large Telescope (VLT) at Cerro Paranal. These high-quality data allow spatially-resolved studies of the gas-phase kinematics of these galaxies, as well dynamical information on their outflows. In this work, I explore outflow properties in one galaxy with exceptionally deep data, allowing detailed examination of the outflow energetics, spatial extent and underlying ISM properties, as well those from a larger sample of galaxies. I also probe the fraction of SFGs in our sample which contain (possibly obscured) AGN, and study how this affects our determination of galaxy properties, such as gas-phase metallicity. Finally

  10. The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z = 3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe

    NASA Astrophysics Data System (ADS)

    Martis, Nicholas S.; Marchesini, Danilo; Brammer, Gabriel B.; Muzzin, Adam; Labbé, Ivo; Momcheva, Ivelina G.; Skelton, Rosalind E.; Stefanon, Mauro; van Dokkum, Pieter G.; Whitaker, Katherine E.

    2016-08-01

    Using the UltraVISTA DR1 and 3D-HST catalogs, we construct a stellar-mass-complete sample, unique for its combination of surveyed volume and depth, to study the evolution of the fractions of quiescent galaxies, moderately unobscured star-forming galaxies, and dusty star-forming galaxies as a function of stellar mass over the redshift interval 0.2 ≤ z ≤ 3.0. We show that the role of dusty star-forming galaxies within the overall galaxy population becomes more important with increasing stellar mass and grows rapidly with increasing redshift. Specifically, dusty star-forming galaxies dominate the galaxy population with {log}({M}{{star}}/{M}ȯ )≳ 10.3 at z ≳ 2. The ratio of dusty and non-dusty star-forming galaxies as a function of stellar mass changes little with redshift. Dusty star-forming galaxies dominate the star-forming population at {log}({M}{{star}}/{M}ȯ )≳ 10.0{--}10.5, being a factor of ˜3–5 more common, while unobscured star-forming galaxies dominate at {log}({M}{{star}}/{M}ȯ )≲ 10. At {log}({M}{{star}}/{M}ȯ )\\gt 10.5, red galaxies dominate the galaxy population at all redshift z < 3, either because they are quiescent (at late times) or dusty star-forming (in the early universe).

  11. The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z = 3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe

    NASA Astrophysics Data System (ADS)

    Martis, Nicholas S.; Marchesini, Danilo; Brammer, Gabriel B.; Muzzin, Adam; Labbé, Ivo; Momcheva, Ivelina G.; Skelton, Rosalind E.; Stefanon, Mauro; van Dokkum, Pieter G.; Whitaker, Katherine E.

    2016-08-01

    Using the UltraVISTA DR1 and 3D-HST catalogs, we construct a stellar-mass-complete sample, unique for its combination of surveyed volume and depth, to study the evolution of the fractions of quiescent galaxies, moderately unobscured star-forming galaxies, and dusty star-forming galaxies as a function of stellar mass over the redshift interval 0.2 ≤ z ≤ 3.0. We show that the role of dusty star-forming galaxies within the overall galaxy population becomes more important with increasing stellar mass and grows rapidly with increasing redshift. Specifically, dusty star-forming galaxies dominate the galaxy population with {log}({M}{{star}}/{M}⊙ )≳ 10.3 at z ≳ 2. The ratio of dusty and non-dusty star-forming galaxies as a function of stellar mass changes little with redshift. Dusty star-forming galaxies dominate the star-forming population at {log}({M}{{star}}/{M}⊙ )≳ 10.0{--}10.5, being a factor of ˜3-5 more common, while unobscured star-forming galaxies dominate at {log}({M}{{star}}/{M}⊙ )≲ 10. At {log}({M}{{star}}/{M}⊙ )\\gt 10.5, red galaxies dominate the galaxy population at all redshift z < 3, either because they are quiescent (at late times) or dusty star-forming (in the early universe).

  12. Everything you ever wanted to know about the ultraviolet spectra of star-forming galaxies but were afraid to ask

    NASA Technical Reports Server (NTRS)

    Kinney, A. L.; Bohlin, R.; Calzetti, D.; Panagia, N.; Wyse, R.

    1993-01-01

    We present ultraviolet spectra of 143 star-forming galaxies of different morphological types and activity classes including S0, Sa, Sb, Sc, Sd, irregular, starburst, blue compact, blue compact dwarf, Liner, and Seyfert 2 galaxies. These IUE spectra cover the wavelength range from 1200 to 3200 A and are taken in a large aperture (10 x 20 inch). The ultraviolet spectral energy distributions are shown for a subset of the galaxies, ordered by spectral index, and separated by type for normal galaxies, Liners, starburst galaxies, blue compact (BCG) and blue compact dwarf (BCDG) galaxies, and Seyfert 2 galaxies. The ultraviolet spectra of Liners are, for the most part, indistinguishable from the spectra of normal galaxies. Starburst galaxies have a large range of ultraviolet slope, from blue to red. The star-forming galaxies which are the bluest in the optical (BCG and BCDG), also have the 'bluest' average ultraviolet slope of beta = -1.75 +/- 0.63. Seyfert 2 galaxies are the only galaxies in the sample that consistently have detectable UV emission lines.

  13. The Infrared Spectral Energy Distribution of Normal Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Dale, Daniel A.; Helou, George; Contursi, Alessandra; Silbermann, Nancy A.; Kolhatkar, Sonali

    2001-03-01

    We present a new phenomenological model for the spectral energy distribution of normal star-forming galaxies between 3 and 1100 μm. A sequence of realistic galaxy spectra are constructed from a family of dust emission curves assuming a power-law distribution of dust mass over a wide range of interstellar radiation fields. For each interstellar radiation field heating intensity, we combine emission curves for large and very small grains and aromatic feature carriers. The model is constrained by IRAS and ISOCAM broadband photometric and ISOPHOT spectrophotometric observations for our sample of 69 normal galaxies; the model reproduces well the empirical spectra and infrared color trends. These model spectra allow us to determine the infrared energy budget for normal galaxies and in particular to translate far-infrared fluxes into total (bolometric) infrared fluxes. The 20-42 μm range appears to show the most significant growth in relative terms as the activity level increases, suggesting that the 20-42 μm continuum may be the best dust emission tracer of current star formation in galaxies. The redshift dependence of infrared color-color diagrams and the far-infrared-to-radio correlation for galaxies are also explored.

  14. STRUCTURES OF LOCAL GALAXIES COMPARED TO HIGH-REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Petty, Sara M.; De Mello, DuIlia F.; Gallagher, John S.; Gardner, Jonathan P.; Lotz, Jennifer M.; Matt Mountain, C.; Smith, Linda J.

    2009-08-15

    The rest-frame far-ultraviolet morphologies of eight nearby interacting and starburst galaxies (Arp 269, M 82, Mrk 8, NGC 520, NGC 1068, NGC 3079, NGC 3310, and NGC 7673) are compared with 54 galaxies at z {approx} 1.5 and 46 galaxies at z {approx} 4 observed in the Great Observatories Origins Deep Survey (GOODS) taken with the Advanced Camera for Surveys onboard the Hubble Space Telescope. The nearby sample is artificially redshifted to z {approx} 1.5 and 4 by applying luminosity and size scaling. We compare the simulated galaxy morphologies to real z {approx} 1.5 and 4 UV-bright galaxy morphologies. We calculate the Gini coefficient (G), the second-order moment of the brightest 20% of the galaxy's flux (M {sub 20}), and the Sersic index (n). We explore the use of nonparametric methods with two-dimensional profile fitting and find the combination of M {sub 20} with n an efficient method to classify galaxies as having merger, exponential disk, or bulge-like morphologies. When classified according to G and M {sub 20} 20/30% of real/simulated galaxies at z {approx} 1.5 and 37/12% at z {approx} 4 have bulge-like morphologies. The rest have merger-like or intermediate distributions. Alternatively, when classified according to the Sersic index, 70% of the z {approx} 1.5 and z {approx} 4 real galaxies are exponential disks or bulge-like with n>0.8, and {approx} 30% of the real galaxies are classified as mergers. The artificially redshifted galaxies have n values with {approx} 35% bulge or exponential at z {approx} 1.5 and 4. Therefore, {approx} 20%-30% of Lyman-break galaxies have structures similar to local starburst mergers, and may be driven by similar processes. We assume merger-like or clumpy star-forming galaxies in the GOODS field have morphological structure with values n < 0.8 and M {sub 20}> - 1.7. We conclude that Mrk 8, NGC 3079, and NGC 7673 have structures similar to those of merger-like and clumpy star-forming galaxies observed at z {approx} 1.5 and 4.

  15. 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.

  16. Nearby Clumpy, Gas Rich, Star-forming Galaxies: Local Analogs of High-redshift Clumpy Galaxies

    NASA Astrophysics Data System (ADS)

    Garland, C. A.; Pisano, D. J.; Mac Low, M.-M.; Kreckel, K.; Rabidoux, K.; Guzmán, R.

    2015-07-01

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates (SFRs) and compact morphologies. We combine Sloan Digital Sky Survey data with H i data of 29 LCBGs at redshift z ∼ 0 to understand their nature. We find that local LCBGs have high atomic gas fractions (∼50%) and SFRs per stellar mass consistent with some high-redshift star-forming galaxies (SFGs). Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy SFGs commonly observed at z ∼ 1–3. Local LCBGs separate into three groups: (1) interacting galaxies (∼20%) (2) clumpy spirals (∼40%) and (3) non-clumpy, non-spirals with regular shapes and smaller effective radii and stellar masses (∼40%). It seems that the method of building up a high gas fraction, which then triggers star formation, is not the same for all local LCBGs. This may lead to a dichotomy in galaxy characteristics. We consider possible gas delivery scenarios and suggest that clumpy spirals, preferentially located in clusters and with companions, are smoothly accreting gas from tidally disrupted companions and/or intracluster gas enriched by stripped satellites. Conversely, as non-clumpy galaxies are preferentially located in the field and tend to be isolated, we suggest clumpy, cold streams, which destroy galaxy disks and prevent clump formation, as a likely gas delivery mechanism for these systems. Other possibilities include smooth cold streams, a series of minor mergers, or major interactions.

  17. NEARBY CLUMPY, GAS RICH, STAR-FORMING GALAXIES: LOCAL ANALOGS OF HIGH-REDSHIFT CLUMPY GALAXIES

    SciTech Connect

    Garland, C. A.; Pisano, D. J.; Rabidoux, K.; Low, M.-M. Mac; Kreckel, K.; Guzmán, R. E-mail: djpisano@mail.wvu.edu E-mail: mordecai@amnh.org E-mail: guzman@astro.ufl.edu

    2015-07-10

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates (SFRs) and compact morphologies. We combine Sloan Digital Sky Survey data with H i data of 29 LCBGs at redshift z ∼ 0 to understand their nature. We find that local LCBGs have high atomic gas fractions (∼50%) and SFRs per stellar mass consistent with some high-redshift star-forming galaxies (SFGs). Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy SFGs commonly observed at z ∼ 1–3. Local LCBGs separate into three groups: (1) interacting galaxies (∼20%); (2) clumpy spirals (∼40%); and (3) non-clumpy, non-spirals with regular shapes and smaller effective radii and stellar masses (∼40%). It seems that the method of building up a high gas fraction, which then triggers star formation, is not the same for all local LCBGs. This may lead to a dichotomy in galaxy characteristics. We consider possible gas delivery scenarios and suggest that clumpy spirals, preferentially located in clusters and with companions, are smoothly accreting gas from tidally disrupted companions and/or intracluster gas enriched by stripped satellites. Conversely, as non-clumpy galaxies are preferentially located in the field and tend to be isolated, we suggest clumpy, cold streams, which destroy galaxy disks and prevent clump formation, as a likely gas delivery mechanism for these systems. Other possibilities include smooth cold streams, a series of minor mergers, or major interactions.

  18. C III] EMISSION IN STAR-FORMING GALAXIES NEAR AND FAR

    SciTech Connect

    Rigby, J. R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Johnson, T.; Wuyts, E.; Dahle, H.; Peña-Guerrero, M.

    2015-11-20

    We measure [C iii] 1907, C iii] 1909 Å emission lines in 11 gravitationally lensed star-forming galaxies at z ∼ 1.6–3, finding much lower equivalent widths than previously reported for fainter lensed galaxies. While it is not yet clear what causes some galaxies to be strong C iii] emitters, C iii] emission is not a universal property of distant star-forming galaxies. We also examine C iii] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST and IUE. Twenty percent of these local galaxies show strong C iii] emission, with equivalent widths < −5 Å. Three nearby galaxies show C iii] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf–Rayet galaxies. At all redshifts, strong C iii] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C iii] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.

  19. GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS

    SciTech Connect

    Van der Wel, A.; Chang, Yu-Yen; Rix, H.-W.; Martig, M.; Bell, E. F.; Holden, B. P.; Koo, D. C.; Mozena, M.; Faber, S. M.; Giavalisco, M.; Skelton, R.; Whitaker, K.; Momcheva, I.; Van Dokkum, P. G.; Dekel, A.; Ceverino, D.; Franx, M.; and others

    2014-09-01

    We determine the intrinsic, three-dimensional shape distribution of star-forming galaxies at 0 < z < 2.5, as inferred from their observed projected axis ratios. In the present-day universe, star-forming galaxies of all masses 10{sup 9}-10{sup 11} M {sub ☉} are predominantly thin, nearly oblate disks, in line with previous studies. We now extend this to higher redshifts, and find that among massive galaxies (M {sub *} > 10{sup 10} M {sub ☉}) disks are the most common geometric shape at all z ≲ 2. Lower-mass galaxies at z > 1 possess a broad range of geometric shapes: the fraction of elongated (prolate) galaxies increases toward higher redshifts and lower masses. Galaxies with stellar mass 10{sup 9} M {sub ☉} (10{sup 10} M {sub ☉}) are a mix of roughly equal numbers of elongated and disk galaxies at z ∼ 1 (z ∼ 2). This suggests that galaxies in this mass range do not yet have disks that are sustained over many orbital periods, implying that galaxies with present-day stellar mass comparable to that of the Milky Way typically first formed such sustained stellar disks at redshift z ∼ 1.5-2. Combined with constraints on the evolution of the star formation rate density and the distribution of star formation over galaxies with different masses, our findings imply that, averaged over cosmic time, the majority of stars formed in disks.

  20. C III] Emission in Star-Forming Galaxies Near and Far

    NASA Technical Reports Server (NTRS)

    Rigby, J, R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.; Johnson, T.; Pena-Guerrero, M.

    2015-01-01

    We measure C III Lambda Lambda 1907, 1909 Angstrom emission lines in eleven gravitationally-lensed star-forming galaxies at zeta at approximately 1.6-3, finding much lower equivalent widths than previously reported for fainter lensed galaxies (Stark et al. 2014). While it is not yet clear what causes some galaxies to be strong C III] emitters, C III] emission is not a universal property of distant star-forming galaxies. We also examine C III] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST, and IUE. Twenty percent of these local galaxies show strong C III] emission, with equivalent widths less than -5 Angstrom. Three nearby galaxies show C III] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf-Rayet galaxies. At all redshifts, strong C III] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C III] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.

  1. Chemical Pollution and Evolution of Massive Starbursts: Cleaning up the Environment in Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Kobulnicky, C.

    1996-12-01

    I present the results of a research program seeking to characterize the impact of massive star-clusters on the chemical and dynamical evolution of metal-poor, irregular and blue compact galaxies. The evolution of high mass stars is thought to contribute the bulk of heavy element enrichment in the interstellar medium, especially alpha -process elements like O, Si, etc. Yet, in actively star-forming galaxies, localized chemical inhomogeneities are seldom observed. Spatially-resolved optical and ultraviolet spectroscopy from the Hubble Space Telescope and ground-based observatories is used to search for chemical enrichment in the vicinity of young star clusters in nearby galaxies. VLA aperture synthesis maps are used to examine the neutral hydrogen content, dynamics, and local environment of the sample galaxies. Despite the spread in evolutionary state of the starbursts determined by the EW of Balmer emission lines and the radio continuum spectral index, few instances of localized enrichment are found. In light of these data, the ``instantaneous enrichment'' scenario for extragalactic HII regions appears less probable than one which operates on long timescales and global spatial scales. The results are consistent with the idea that starburst driven winds expel freshly synthesized metals in a hot 10(6) K phase into the halos of galaxies where they cool, condense into globules, and mix homogeneously with the rest of the galaxy on long (dynamical) timescales. The C/O and N/O ratios of the galaxies are used as new tools for measuring the recent star formation history. Implications for chemical evolution of galaxies both locally and cosmologically are developed.

  2. The connection between galaxy environment and the luminosity function slopes of star-forming regions

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David; Calzetti, Daniela; Kennicutt, Robert C.

    2016-11-01

    We present the first study of GALEX far-ultraviolet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ˜65 000 star-forming regions (i.e. FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of 82 galaxies with reliable luminosity functions are used to define these relationships and represent the largest sample of galaxies with the largest range of galaxy properties used to study the connection between luminosity function properties and galaxy environment. We find that α correlates with global star formation properties, where galaxies with higher star formation rates and star formation rate densities (ΣSFR) tend to have flatter luminosity function slopes. In addition, we find that neither stochastic sampling of the luminosity function in galaxies with low-number statistics nor the effects of blending due to distance can fully account for these trends. We hypothesize that the flatter slopes in high ΣSFR galaxies is due to higher gas densities and higher star formation efficiencies which result in proportionally greater numbers of bright star-forming regions. Finally, we create a composite luminosity function composed of star-forming regions from many galaxies and find a break in the luminosity function at brighter luminosities. However, we find that this break is an artefact of varying detection limits for galaxies at different distances.

  3. Early star-forming galaxies and the reionization of the Universe.

    PubMed

    Robertson, Brant E; Ellis, Richard S; Dunlop, James S; McLure, Ross J; Stark, Daniel P

    2010-11-01

    Star-forming galaxies trace cosmic history. Recent observational progress with the NASA Hubble Space Telescope has led to the discovery and study of the earliest known galaxies, which correspond to a period when the Universe was only ∼800 million years old. Intense ultraviolet radiation from these early galaxies probably induced a major event in cosmic history: the reionization of intergalactic hydrogen. PMID:21048759

  4. The clustering evolution of dusty star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Cowley, William I.; Lacey, Cedric G.; Baugh, Carlton M.; Cole, Shaun

    2016-09-01

    We present predictions for the clustering of galaxies selected by their emission at far-infrared (FIR) and sub-millimetre wavelengths. This includes the first predictions for the effect of clustering biases induced by the coarse angular resolution of single-dish telescopes at these wavelengths. We combine a new version of the GALFORM model of galaxy formation with a self-consistent model for calculating the absorption and re-emission of radiation by interstellar dust. Model galaxies selected at 850μm reside in dark matter haloes of mass Mhalo ˜ 1011.5-1012 h-1 M⊙, independent of redshift (for 0.2 ≲ z ≲ 4) or flux (for 0.25 ≲ S850 μm ≲ 4 mJy). At z ˜ 2.5, the brightest galaxies (S850 μm > 4 mJy) exhibit a correlation length of r0=5.5_{-0.5}^{+0.3} h-1 Mpc, consistent with observations. We show that these galaxies have descendants with stellar masses M⋆ ˜ 1011 h-1 M⊙ occupying haloes spanning a broad range in mass Mhalo ˜ 1012-1014 h-1 M⊙. The FIR emissivity at shorter wavelengths (250, 350 and 500 μm) is also dominated by galaxies in the halo mass range Mhalo ˜ 1011.5-1012 h-1 M⊙, again independent of redshift (for 0.5 ≲ z ≲ 5). We compare our predictions for the angular power spectrum of cosmic infrared background anisotropies at these wavelengths with observations, finding agreement to within a factor of ˜2 over all scales and wavelengths, an improvement over earlier versions of the model. Simulating images at 850 μm, we show that confusion effects boost the measured angular correlation function on all scales by a factor of ˜4. This has important consequences, potentially leading to inferred halo masses being overestimated by an order of magnitude.

  5. The Herschel Virgo Cluster Survey. XVIII. Star-forming dwarf galaxies in a cluster environment

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Hunt, L. K.; Madden, S. C.; Hughes, T. M.; Auld, R.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bizzocchi, L.; Boquien, M.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Davies, J.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Pappalardo, C.; Pierini, D.; Rémy-Ruyer, A.; Smith, M. W. L.; Verstappen, J.; Viaene, S.; Vlahakis, C.

    2015-02-01

    To assess the effects of the cluster environment on the different components of the interstellar medium, we analyse the far-infrared (FIR) and submillimetre (submm) properties of a sample of star-forming dwarf galaxies detected by the Herschel Virgo Cluster Survey (HeViCS). We determine dust masses and dust temperatures by fitting a modified black body function to the spectral energy distributions (SEDs). Stellar and gas masses, star formation rates (SFRs), and metallicities are obtained from the analysis of a set of ancillary data. Dust is detected in 49 out of a total 140 optically identified dwarfs covered by the HeViCS field; considering only dwarfs brighter than mB = 18 mag, this gives a detection rate of 43%. After evaluating different emissivity indices, we find that the FIR-submm SEDs are best-fit by β = 1.5, with a median dust temperature Td = 22.4 K. Assuming β = 1.5, 67% of the 23 galaxies detected in all five Herschel bands show emission at 500 μm in excess of the modified black-body model. The fraction of galaxies with a submillimetre excess decreases for lower values of β, while a similarly high fraction (54%) is found if a β-free SED modelling is applied. The excess is inversely correlated with SFR and stellar masses. To study the variations in the global properties of our sample that come from environmental effects, we compare the Virgo dwarfs to other Herschel surveys,such as the Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH), the Dwarf Galaxy Survey (DGS), and the HeViCS Bright Galaxy Catalogue (BGC). We explore the relations between stellar mass and Hi fraction, specific star formation rate, dust fraction, gas-to-dust ratio over a wide range of stellar masses (from 107 to 1011 M⊙) for both dwarfs and spirals. Highly Hi-deficient Virgo dwarf galaxies are mostly characterised by quenched star formation activity and lower dust fractions giving hints for dust stripping in cluster dwarfs. However, to explain the

  6. Galaxy Zoo: spiral galaxy morphologies and their relation to the star-forming main sequence

    NASA Astrophysics Data System (ADS)

    Willett, Kyle; Schawinski, Kevin; Masters, Karen; Melvin, Tom; Skibba, Ramin A.; Nichol, Robert; Cheung, Edmond; Lintott, Chris; Simmons, Brooke D.; Kaviraj, Sugata; Keel, William C.; Fortson, Lucy; Galaxy Zoo volunteers

    2015-01-01

    We examine the relationship between stellar mass and star formation rate in disk galaxies at z<0.085, measuring different populations of spirals as classified by their kiloparsec-scale structure. The morphologies of disk galaxies are obtained from the Galaxy Zoo 2 project, which includes the number of spiral arms, the arm pitch angle, and the presence of strong galactic bars. We show that both the slope and dispersion of the star-forming main sequence (SFMS) is constant no matter what the morphology of the spiral disk. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by 0.3 dex; this is a significant reduction over the increase seen in merging systems at higher redshifts (z > 1). Of the galaxies that do lie significantly above the SFMS in the local Universe, more than 50% are mergers, with a large contribution from the compact green pea galaxies. We interpret our results as evidence that the number and pitch angle of spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms for star formation or are completely overwhelmed by the combination of outflows and feedback.

  7. High molecular gas fractions in normal massive star-forming galaxies in the young Universe.

    PubMed

    Tacconi, L J; Genzel, R; Neri, R; Cox, P; Cooper, M C; Shapiro, K; Bolatto, A; Bouché, N; Bournaud, F; Burkert, A; Combes, F; Comerford, J; Davis, M; Schreiber, N M Förster; Garcia-Burillo, S; Gracia-Carpio, J; Lutz, D; Naab, T; Omont, A; Shapley, A; Sternberg, A; Weiner, B

    2010-02-11

    Stars form from cold molecular interstellar gas. As this is relatively rare in the local Universe, galaxies like the Milky Way form only a few new stars per year. Typical massive galaxies in the distant Universe formed stars an order of magnitude more rapidly. Unless star formation was significantly more efficient, this difference suggests that young galaxies were much more molecular-gas rich. Molecular gas observations in the distant Universe have so far largely been restricted to very luminous, rare objects, including mergers and quasars, and accordingly we do not yet have a clear idea about the gas content of more normal (albeit massive) galaxies. Here we report the results of a survey of molecular gas in samples of typical massive-star-forming galaxies at mean redshifts of about 1.2 and 2.3, when the Universe was respectively 40% and 24% of its current age. Our measurements reveal that distant star forming galaxies were indeed gas rich, and that the star formation efficiency is not strongly dependent on cosmic epoch. The average fraction of cold gas relative to total galaxy baryonic mass at z = 2.3 and z = 1.2 is respectively about 44% and 34%, three to ten times higher than in today's massive spiral galaxies. The slow decrease between z approximately 2 and z approximately 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.

  8. Sub-millimeter Telescope CO (2-1) Observations of Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Jiang, Xue-Jian; Wang, Zhong; Gu, Qiusheng; Wang, Junzhi; Zhang, Zhi-Yu

    2015-01-01

    We present CO J = 2-1 observations toward 32 nearby gas-rich star-forming galaxies selected from the ALFALFA and Wide-field Infrared Survey Explorer (WISE) catalogs, using the Sub-millimeter Telescope (SMT). Our sample is selected to be dominated by intermediate-M * galaxies. The scaling relations between molecular gas, atomic gas, and galactic properties (stellar mass, NUV - r, and WISE color W3 - W2) are examined and discussed. Our results show the following. (1) In the galaxies with stellar mass M * <=1010 M ⊙, the H I fraction (f H I ≡ M H I /M *) is significantly higher than that of more massive galaxies, while the H2 gas fraction (f_H_2 ≡ M_H_2/M *) remains nearly unchanged. (2) Compared to f_H_2, f H I correlates better with both M * and NUV - r. (3) A new parameter, WISE color W3 - W2 (12-4.6 μm), is introduced, which is similar to NUV - r in tracing star formation activity, and we find that W3 - W2 has a tighter anti-correlation with log f_H_2 than the anti-correlation of (NUV - r)-f H I , (NUV - r)-f_H_2, and (W3 - W2)-f H I . This indicates that W3 - W2 can trace the H2 fraction in galaxies. For the gas ratio M_H_2/M H I , only in the intermediate-M * galaxies it appears to depend on M * and NUV - r. We find a tight correlation between the molecular gas mass M_H_2 and 12 μm (W3) luminosities (L 12 μm), and the slope is close to unity (1.03 ± 0.06) for the SMT sample. This correlation may reflect that the cold gas and dust are well mixed on a global galactic scale. Using the all-sky 12 μm (W3) data available in WISE, this correlation can be used to estimate CO flux for molecular gas observations and can even predict H2 mass for star-forming galaxies.

  9. Characterizing Warm Molecular Hydrogen in Active Star-Forming Systems

    NASA Astrophysics Data System (ADS)

    Rangwala, Naseem

    2014-10-01

    Herschel observations of nearby star-forming galaxies have determined that the warm component of the molecular gas traced by the high-J CO lines dominates the luminosity (~90% of the total CO luminosity) and hence the energetics of the molecular ISM. At the temperatures (T = 300 - 2000 K) and densities (n_H < 1E6 per cubic cm) typically found in our survey, H2 emission is the dominant gas coolant, much more important than CO. A fundamental assumption of all analyses of CO emission has been that CO emission traces H2 over the entire range of physical conditions in the observed sources. However, a direct observational comparison of spatial distributions and kinematics of CO and H2 has never been made for the warm molecular gas. We propose to observe the warm H2, in S(1) and S(2) transitions, with the SOFIA-EXES instrument in a diverse sample of star-forming systems: NGC 253 (starburst nucleus), NGC 6240 (luminous infrared galaxy), NGC 1068 (Seyfert-2), and SgrB2(M)/(N) (Galactic hot cores). The primary goal is to compare these measurements with the warm CO (J = 6-5 transition) observed with the Atacama Large Millimeter Array (ALMA) to investigate differences in the kinematics and spatial distributions (for the extended targets) of the two molecules and thereby confirm whether CO is a reliable tracer of H2 in the warm gas.

  10. Metallicity gradients and newly created star-forming systems in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Mendes de Oliveira, Claudia L.

    2015-08-01

    Interactions play an extremely important role in the evolution of galaxies, changing their morphologies and kinematics. Galaxy collisions may result in the formation of intergalactic star-forming objects, such as HII regions, young clusters and/or tidal dwarf galaxies. Several studies have found a wealth of newly created objects in interacting systems. We will exemplify the problems and challenges in this field and will describe observations of the interacting group NGC 6845, which contains four bright galaxies, two of which have extended tidal tails. We obtained Gemini/GMOS spectra for 28 of the regions located in the galaxies and in the tails. All regions in the latter are star-forming objects according to their line ratios, with ages younger than 10 Myr. A super luminous star forming complex is found in the brightest member of the group, NGC 6845A. Its luminosity reveals a star formation density of 0.19 solar masses, per year, per kpc^2, suggesting that this object is a localized starburst. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. We speculate that the observed metallicity gradient may be related to one or more of the following mechanisms: (1) interaction induced inflow of fresh gas to the galaxy center, as seen in simulations, which is expected to dilute the metallicity of the central burst, (2) the formation of young metal-rich star forming regions in the tidal tails, which were born out of enriched gas expelled from the central regions of the system during the interaction and (3) the incremental growth of metals accumulated over time, due to the successful generations of star forming regions along the tails. Finally we will describe our plans to do a search for such objects on Halpha images that will soon be available for 17.5k degrees of the sky, with the A-PLUS survey.

  11. Photometric and spectroscopic studies of star-forming regions within Wolf-Rayet galaxies

    NASA Astrophysics Data System (ADS)

    Karthick, M. Chrisphin; López-Sánchez, Ángel R.; Sahu, D. K.; Sanwal, B. B.; Bisht, Shuchi

    2014-03-01

    We present a study of the properties of star-forming regions within a sample of seven Wolf-Rayet (WR) galaxies. We analyse their morphologies, colours, star-formation rates (SFRs), metallicities and stellar populations, combining broad-band and narrow-band photometry with low-resolution optical spectroscopy. The UBVRI observations were made with the 2-m HCT (Himalayan Chandra Telescope) and 1-m ARIES telescope. The spectroscopic data were obtained using the Hanle Faint Object Spectrograph Camera (HFOSC) mounted on the 2-m HCT. The observed galaxies are NGC 1140, IRAS 07164+5301, NGC 3738, UM 311, NGC 6764, NGC 4861 and NGC 3003. The optical spectra were used to search for the faint WR features, to confirm that the ionization of the gas is caused by the massive stars, and to quantify the oxygen abundance of each galaxy using several independent empirical calibrations. We detected broad features originating in WR stars in NGC 1140 and 4861 and used them to derive the massive star populations. For these two galaxies we also derived the oxygen abundance using a direct estimation of the electron temperature of the ionized gas. The N/O ratio in NGC 4861 is ˜0.25-0.35 dex higher than expected, which may be a consequence of the chemical pollution by N-rich material released by WR stars. Using our Hα images we identified tens of star-forming regions within these galaxies, for which we derived the SFR. Our Hα-based SFR usually agrees with the SFR computed using the far-infrared and the radio-continuum flux. For all regions we found that the most recent star-formation event is 3-6 Myr old. We used the optical broad-band colours in combination with Starburst99 models to estimate the internal reddening and the age of the dominant underlying stellar population within all these regions. Knots in NGC 3738, 6764 and 3003 generally show the presence of an important old (400-1000 Myr) stellar population. However, the optical colours are not able to detect stars older than 20

  12. 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.

  13. Low redshift star-forming galaxies: What can they teach us about primeval galaxies?

    NASA Technical Reports Server (NTRS)

    Calzetti, D.; Kinney, A. L.

    1993-01-01

    The analysis of the UV plus optical spectra of three star-forming galaxies, Mrk 496, Mrk 357, TOL1924-416, obtained by matching the size of the optical aperture with that of IUE, has given unexpected results. These can be summarized as follows: (1) the dereddened Ly(alpha)/H(beta) ratios are consistent with the prediction of case B recombination for nebular emission, within the uncertainties; (2) the decrease of the Ly(alpha)/H(beta) ratio with increasing metallicities is not confirmed in our three objects, although the sample is too small to consider this result definitive. The first result is surprising, mainly because at least the two Markarian galaxies have a large enough H1 content to markedly increase the optical depth for the Ly(alpha) photons and to trigger their absorption by dust. This finding can probably be explained as an effect of the inhomogeneous distribution of gas and dust within the galaxies. On the basis of these results, we conclude that the detection of the Ly(alpha) emission line in searching for primeval galaxies (PG's) can be still considered a valid technique.

  14. Faint Lyα Emitters, Star-forming Galaxies, and Damped Lyα Systems

    NASA Astrophysics Data System (ADS)

    Rauch, M.; Haehnelt, M.; Bunker, A.; Becker, G.; Marleau, F.; Graham, J.; Cristiani, S.; Jarvis, M.; Lacey, C.; Morris, S.; Peroux, C.; Roettgering, H.; Theuns, T.

    2008-10-01

    We have discovered a population of faint single line emitters, likely to be identified with faint z˜ 3 Lyα emitters and with the host galaxies of damped Lyman alpha systems. The objects appear to constitute the bulk of the star-forming galaxies detected so far from the ground, and are likely to provide the gaseous reservoir from which present-day Milky way type galaxies have formed. Unlike color-selected (yman break galaxies, these objects appear to have low star-formation rates, relatively strong Lyalpha emission, and low masses, metallicities, and dust content (s.a. arXiv:0711.1354).

  15. Ultraviolet and Visible Analysis of Star-Forming Regions in Several Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Zernow, Lea; Hunter, D. A.

    2007-12-01

    As some of the smallest and most numerous galaxies in the universe, dwarf irregular (dIm) galaxies give many opportunities for developing an understanding of the manner in which the universe operates. In particular, these galaxies offer challenges to standard models of star formation. The concentration of gas is sufficiently small that the standard models cannot account for the presence of stars in the galaxies. In order to examine this paradox, we used ultraviolet images obtained with the GALEX satellite and optical ground-based imaging to examine the properties of star-forming regions in three dIm galaxies: DDO 50, IC 1613, and WLM. We identified candidate young star-forming regions on near ultraviolet (NUV, 2270 Angstroms) images. We then measured the brightness of the regions in the NUV, far ultraviolet (FUV, 1520 Angstroms), and UBV images. Colors were compared to cluster evolutionary models to estimate ages of the regions, which enabled an estimate of the visual magnitude at a fiducial age of ten million years. We divided the galaxies into three broad annuli in order to compare properties of the star-forming regions as a function of radius. We discuss the properties of star-forming regions in the three galaxies in the context of current star formation models that predict star formation on the basis of large-scale gravitational instability and local-scale gas compression. LZ extends gratitude for funding from the National Science Foundation's Research Experiences for Undergraduates (REU) program at Northern Arizona University through grant AST-0453611. DAH gratefully acknowledges funding for this research from the NASA GALEX program through grant NNX07AJ36G.

  16. A deep Chandra observation of the interacting star-forming galaxy Arp 299

    NASA Astrophysics Data System (ADS)

    Anastasopoulou, K.; Zezas, A.; Ballo, L.; Della Ceca, R.

    2016-08-01

    We present results from a 90 ks Chandra ACIS-S observation of the X-ray luminous interacting galaxy system Arp 299 (NGC 3690/IC 694). We detect 25 discrete X-ray sources with luminosities above ˜4.0 × 1038 erg s-1 covering the entire Ultra Luminous X-ray source (ULX) regime. Based on the hard X-ray spectra of the non-nuclear discrete sources identified in Arp 299, and their association with young, actively star-forming region of Arp 299 we identify them as HMXBs. We find in total 20 off-nuclear sources with luminosities above the ULX limit, 14 of which are point-like sources. Furthermore we observe a marginally significant deficit in the number of ULXs, with respect to the number expected from scaling relations of X-ray binaries with the star formation rate (SFR). Although the high metallicity of the galaxy could result in lower ULX numbers, the good agreement between the observed total X-ray luminosity of ULXs, and that expected from the relevant scaling relation indicates that this deficit could be the result of confusion effects. The integrated spectrum of the galaxy shows the presence of a hot gaseous component with kT = 0.72 ± 0.03 keV, contributing ˜20 per cent of the soft (0.1-2.0 keV) unabsorbed luminosity of the galaxy. A plume of soft X-ray emission in the west of the galaxy indicates a large scale outflow. We find that the AGN in NGC 3690 contributes only 22 per cent of the observed broad-band X-ray luminosity of Arp 299.

  17. Evolution and Feedback Effects of High-z Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Ouchi, Masami

    2015-08-01

    I review the recent observational progresses of star-forming galaxies at a redshift up to z~10. In conjunction with gravitational lensing magnifications, deep HST observations obtain first density estimates of UV-continuum radiation given by young massive stars, and reveal that the star-formation rate density (SFRD) continuously decreases from z~2-3 to z~10. This SFRD decrease towards high-z should be explained by the combination of the cosmic structure formation and radiative cooling+feedback effects in a halo. To decouple the contribution of the cosmic structure formation from the SFRD decrease, the stellar-to-halo mass ratios (SHMR) of high-z galaxies are derived by intensive clustering analyses with HST and Subaru survey data. The SHMR-halo mass relation shows a clear evolution from z~0 to 6, suggesting that the cooling and feedback effects are different between the present and early epochs of the cosmic history. By deep imaging and spectroscopic observations, feedback signatures are found in 10-100 kpc-scale outflow of ionized oxgen gas identified around star-forming galaxies with and without an AGN heating. There are similarly-large hydrogen Lya halos and blobs associated with high-z star-forming galaxies, but the physical origin of these Ly halos and blobs is an open question. At z>~6, UV radiation of ionizing photons produced by star-forming galaxies contribute to the cosmic reionization, while it is thought that the UV radiation prevent formation of next generation stars in dwarf galaxies at the early cosmic epoch, which works as a cosmological feedback effect. I discuss this reionization’s cosmological feedback effect with the up-to-date results from the HST and Planck data.

  18. Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy.

    PubMed

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

    2016-01-14

    One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic 'Dark Ages', when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1-3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy.

  19. Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy.

    PubMed

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

    2016-01-14

    One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic 'Dark Ages', when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1-3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy. PMID:26762455

  20. [C II] emission in z ˜ 6 strongly lensed, star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Knudsen, Kirsten K.; Richard, Johan; Kneib, Jean-Paul; Jauzac, Mathilde; Clément, Benjamin; Drouart, Guillaume; Egami, Eiichi; Lindroos, Lukas

    2016-10-01

    The far-infrared fine-structure line [C II] at 1900.5 GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star formation in very high redshift galaxies. However, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. We report the results of ALMA observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. The galaxy A383-5.1 (star formation rate [SFR] of 3.2 M⊙ yr-1 and magnification of μ = 11.4 ± 1.9) shows a line detection with L_[C II] = 8.9× 106 L⊙, making it the lowest L_[C II] detection at z > 6. For MS0451-H (SFR = 0.4 M⊙ yr-1 and μ = 100 ± 20) we provide an upper limit of L_[C II] < 3× 105 L⊙, which is 1 dex below the local SFR-L_[C II] relations. The results are consistent with predictions for low-metallicity galaxies at z > 6; however, other effects could also play a role in terms of decreasing L[CII]. The detection of A383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted.

  1. Chemo-Kinematic Survey of z ~ 1 Star Forming Galaxies using Keck OSIRIS LGS-AO

    NASA Astrophysics Data System (ADS)

    Mieda, Etsuko; Wright, Shelley A.; Larkin, James E.; Armus, Lee; Juneau, Stephanie

    2015-02-01

    We present first results from the Intermediate Redshift OSIRIS Chemo-Kinematic Survey (IROCKS) of z ~ 1 star forming galaxies (Mieda et al. in prep). We have targeted Hα and [NII] emission lines in J-band and have spatially resolved the galaxies at sub-kilo parsec scale. We have combined our sample with deep HST continuum images, and are able to reveal the dynamics, morphologies, metallicity distribution, emission-line diagnostics, and star formation rates of galaxies spanning this crucial z ~ 1 epoch.

  2. Ionized gas outflows and global kinematics of low-z luminous star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Arribas, S.; Colina, L.; Bellocchi, E.; Maiolino, R.; Villar-Martín, M.

    2014-08-01

    We study the kinematic properties of the ionised gas outflows and ambient interstellar medium (ISM) in a large and representative sample of local luminous and ultra-luminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies) at galactic and sub-galactic (i.e., star-forming clumps) scales, thanks to integral field spectroscopy (IFS)-based high signal-to-noise integrated spectra. The velocity dispersion of the ionized ISM in U/LIRGs (⟨ σ ⟩ ~ 70 km s-1) is larger than in lower luminosity local star-forming galaxies (⟨ σ ⟩ ~ 25 km s-1). While for isolated disc LIRGs star formation appears to sustain turbulence, gravitational energy release associated with interactions and mergers plays an important role in driving σ in the U/LIRG range. We find that σ has a dependency on the star formation rate density (ΣSFR), which is weaker than expected if it were driven by the energy released by the starburst. The relatively small role of star formation (SF) driving the σ in U/LIRGs is reinforced by the lack of an increase in σ associated with high luminosity SF clumps. We also find that the impact of an active galactic nucleus (AGN) in ULIRGs is strong, increasing on average σ by a factor 1.5. Low-z U/LIRGs cover a range of velocity dispersion (σ ~ 30 to 100 km s-1) and star formation rate density (ΣSFR ~ 0.1 to 20 M⊙ yr-1 kpc-2) similar to those of high-z SFGs. Moreover, the observed weak dependency of σ on ΣSFR for local U/LIRGs (σ ∝ ΣSFR+0.06) is in very good agreement with that measured in some high-z samples. The presence of ionized gas outflows in U/LIRGs seems universal based on the detection of a broad, usually blueshifted, Hα line. The observed dependency of the maximum velocity of the outflow (Vmax) on the star formation rate (SFR) is of the type Vmax(non - AGN) ∝ SFR(LIR)+ 0.24. We find that AGNs in U/LIRGs are able to generate faster (~×2) and more massive (~× 1.4) ionized gas outflows than pure starbursts. The derived ionized mass

  3. The effect of disc inclination on the main sequence of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Morselli, L.; Renzini, A.; Popesso, P.; Erfanianfar, G.

    2016-11-01

    We use the Sloan Digital Sky Survey (York et al.) data base to explore the effect of the disc inclination angle on the derived star formation rate (SFR), hence on the slope and width of the main-sequence (MS) relation for star-forming galaxies. We find that SFRs for nearly edge-on discs are underestimated by factors ranging from ˜0.2 dex for low-mass galaxies up to ˜0.4 dex for high-mass galaxies. This results in a substantially flatter MS relation for high-inclination discs compared to that for less inclined ones, though the global effect over the whole sample of star-forming galaxies is relatively minor, given the small fraction of high-inclination discs. However, we also find that galaxies with high-inclination discs represent a non-negligible fraction of galaxies populating the so-called green valley, with derived SFRs intermediate between the MS and those of quenched, passively evolving galaxies.

  4. Far-ultraviolet morphology of star-forming filaments in cool core brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Tremblay, G. R.; O'Dea, C. P.; Baum, S. A.; Mittal, R.; McDonald, M. A.; Combes, F.; Li, Y.; McNamara, B. R.; Bremer, M. N.; Clarke, T. E.; Donahue, M.; Edge, A. C.; Fabian, A. C.; Hamer, S. L.; Hogan, M. T.; Oonk, J. B. R.; Quillen, A. C.; Sanders, J. S.; Salomé, P.; Voit, G. M.

    2015-08-01

    We present a multiwavelength morphological analysis of star-forming clouds and filaments in the central (≲50 kpc) regions of 16 low-redshift (z < 0.3) cool core brightest cluster galaxies. New Hubble Space Telescope imaging of far-ultraviolet continuum emission from young (≲10 Myr), massive (≳5 M⊙) stars reveals filamentary and clumpy morphologies, which we quantify by means of structural indices. The FUV data are compared with X-ray, Lyα, narrow-band Hα, broad-band optical/IR, and radio maps, providing a high spatial resolution atlas of star formation locales relative to the ambient hot (˜107-8 K) and warm ionized (˜104 K) gas phases, as well as the old stellar population and radio-bright active galactic nucleus (AGN) outflows. Nearly half of the sample possesses kpc-scale filaments that, in projection, extend towards and around radio lobes and/or X-ray cavities. These filaments may have been uplifted by the propagating jet or buoyant X-ray bubble, or may have formed in situ by cloud collapse at the interface of a radio lobe or rapid cooling in a cavity's compressed shell. The morphological diversity of nearly the entire FUV sample is reproduced by recent hydrodynamical simulations in which the AGN powers a self-regulating rain of thermally unstable star-forming clouds that precipitate from the hot atmosphere. In this model, precipitation triggers where the cooling-to-free-fall time ratio is tcool/tff ˜ 10. This condition is roughly met at the maximal projected FUV radius for more than half of our sample, and clustering about this ratio is stronger for sources with higher star formation rates.

  5. Baryonic inflow and outflow histories in disk galaxies as revealed from observations of distant star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Toyouchi, Daisuke; Chiba, Masashi

    2016-08-01

    Gas inflow and outflow are the most important processes, which determine the structural and chemical evolution of a disk galaxy like the Milky Way. In order to get new insights into these baryonic processes in Milky Way like galaxies (MWLGs), we consider the data of distant star-forming galaxies and investigate the evolution of the radial density profile of their stellar components and the associated total amount of gaseous inflow and outflow. For this purpose, we analyze the redshift evolution of their stellar mass distribution, combined with the scaling relations between the mass of baryonic components, star formation rate and chemical abundance for both high- and low-z star-forming galaxies. As a result, we find the new relations between star formation rate and inflow/outflow rate as deduced from these distant galaxies, which will provide fundamental information for understanding the structural and chemical evolution of MWLGs.

  6. SUB-MILLIMETER TELESCOPE CO (2-1) OBSERVATIONS OF NEARBY STAR-FORMING GALAXIES

    SciTech Connect

    Jiang, Xue-Jian; Gu, Qiusheng; Wang, Zhong; Wang, Junzhi; Zhang, Zhi-Yu

    2015-01-20

    We present CO J = 2-1 observations toward 32 nearby gas-rich star-forming galaxies selected from the ALFALFA and Wide-field Infrared Survey Explorer (WISE) catalogs, using the Sub-millimeter Telescope (SMT). Our sample is selected to be dominated by intermediate-M {sub *} galaxies. The scaling relations between molecular gas, atomic gas, and galactic properties (stellar mass, NUV – r, and WISE color W3 – W2) are examined and discussed. Our results show the following. (1) In the galaxies with stellar mass M {sub *} ≤10{sup 10} M {sub ☉}, the H I fraction (f {sub H} {sub I} ≡ M {sub H} {sub I}/M {sub *}) is significantly higher than that of more massive galaxies, while the H{sub 2} gas fraction (f{sub H{sub 2}} ≡ M{sub H{sub 2}}/M {sub *}) remains nearly unchanged. (2) Compared to f{sub H{sub 2}}, f {sub H} {sub I} correlates better with both M {sub *} and NUV – r. (3) A new parameter, WISE color W3 – W2 (12-4.6 μm), is introduced, which is similar to NUV – r in tracing star formation activity, and we find that W3 – W2 has a tighter anti-correlation with log f{sub H{sub 2}} than the anti-correlation of (NUV – r)-f {sub H} {sub I}, (NUV – r)-f{sub H{sub 2}}, and (W3 – W2)-f {sub H} {sub I}. This indicates that W3 – W2 can trace the H{sub 2} fraction in galaxies. For the gas ratio M{sub H{sub 2}}/M {sub H} {sub I} , only in the intermediate-M {sub *} galaxies it appears to depend on M {sub *} and NUV – r. We find a tight correlation between the molecular gas mass M{sub H{sub 2}} and 12 μm (W3) luminosities (L {sub 12} {sub μm}), and the slope is close to unity (1.03 ± 0.06) for the SMT sample. This correlation may reflect that the cold gas and dust are well mixed on a global galactic scale. Using the all-sky 12 μm (W3) data available in WISE, this correlation can be used to estimate CO flux for molecular gas observations and can even predict H{sub 2} mass for star-forming galaxies.

  7. The Intergalactic and Circumgalactic Medium surrounding Star-Forming Galaxies at Redshifts 2 < z < 3

    NASA Astrophysics Data System (ADS)

    Rudie, Gwen C.

    We present measurements of the spatial distribution, kinematics, and physical properties of gas in the circumgalactic medium (CGM) of 2.0 < z < 2.8 UV color-selected galaxies as well as within the 2 < z < 3 intergalactic medium (IGM). These measurements are derived from Voigt profile decomposition of the full Lyalpha and Lybeta forest in 15 high-resolution, high signal-to-noise ratio QSO spectra resulting in a catalog of ˜ 6000 H I absorbers. Chapter 2 of this thesis focuses on H I surrounding high-z star-forming galaxies drawn from the Keck Baryonic Structure Survey (KBSS). The KBSS is a unique spectroscopic survey of the distant universe designed to explore the details of the connection between galaxies and intergalactic baryons within the same survey volumes. The KBSS combines high-quality background QSO spectroscopy with large densely-sampled galaxy redshift surveys to probe the CGM at scales of ˜ 50 kpc to a few Mpc. Based on these data, Chapter 2 presents the first quantitative measurements of the distribution, column density, kinematics, and absorber line widths of neutral hydrogen surrounding high-z star-forming galaxies. Chapter 3 focuses on the thermal properties of the diffuse IGM. This analysis relies on measurements of the ˜ 6000 absorber line widths to constrain the thermal and turbulent velocities of absorbing "clouds." A positive correlation between the column density of H I and the minimum line width is recovered and implies a temperature-density relation within the low-density IGM for which higher-density regions are hotter, as is predicted by simple theoretical arguments. Chapter 4 presents new measurements of the opacity of the IGM and CGM to hydrogen-ionizing photons. The chapter begins with a revised measurement of the H I column density distribution based on this new absorption line catalog that, due to the inclusion of high-order Lyman lines, provides the first statistically robust measurement of the frequency of absorbers with H I column

  8. A Survey of Star-forming Galaxies in the 1.4<~Z<~ 2.5 Redshift Desert: Overview

    NASA Astrophysics Data System (ADS)

    Steidel, Charles C.; Shapley, Alice E.; Pettini, Max; Adelberger, Kurt L.; Erb, Dawn K.; Reddy, Naveen A.; Hunt, Matthew P.

    2004-04-01

    The redshift interval 1.4<~z<~2.5 has been described by some as the ``redshift desert'' because of historical difficulties in spectroscopically identifying galaxies in that range. In fact, galaxies can be found in large numbers with standard broadband color selection techniques coupled with follow-up spectroscopy with UV and blue-sensitive spectrographs. In this paper we present the first results of a large-scale survey of such objects, carried out with the blue channel of the LRIS spectrograph (LRIS-B) on the Keck I Telescope. We introduce two samples of star-forming galaxies, ``BX'' galaxies at =2.20+/-0.32 and ``BM'' galaxies at =1.70+/-0.34. In seven survey fields we have spectroscopically confirmed 749 of the former and 114 of the latter. Interlopers (defined as objects at z<1) account for less than 10% of the photometric candidates, and the fraction of faint active galactic nuclei is ~3% in the combined BX/BM sample. Deep near-IR photometry of a subset of the BX sample indicates that, compared with a sample of similarly UV-selected galaxies at z~3, the z~2 galaxies are on average significantly redder in (R-Ks), indicating longer star formation histories, increased reddening by dust, or both. Using near-IR Hα spectra of a subset of BX/BM galaxies to define the galaxies' systemic redshifts, we show that the galactic-scale winds that are a feature of star-forming galaxies at z~3 are also common at later epochs and have similar bulk outflow speeds of 200-300 km s-1. We illustrate with examples the information that can be deduced on the stellar populations, metallicities, and kinematics of redshift desert galaxies from easily accessible rest-frame far-UV and rest-frame optical spectra. Far from being hostile to observations, the universe at z~2 is uniquely suited to providing information on the astrophysics of star-forming galaxies and the intergalactic medium, and the relationship between the two. Based, in part, on data obtained at the W. M. Keck

  9. Physical properties of local star-forming analogues to z ˜ 5 Lyman-break galaxies

    NASA Astrophysics Data System (ADS)

    Greis, Stephanie M. L.; Stanway, Elizabeth R.; Davies, Luke J. M.; Levan, Andrew J.

    2016-07-01

    Intense, compact, star-forming galaxies are rare in the local Universe but ubiquitous at high redshift. We interpret the 0.1-22 μm spectral energy distributions of a sample of 180 galaxies at 0.05 < z < 0.25 selected for extremely high surface densities of inferred star formation in the ultraviolet. By comparison with well-established stellar population synthesis models, we find that our sample comprises young (˜60-400 Myr), moderate mass (˜6 × 109 M⊙) star-forming galaxies with little dust extinction (mean stellar continuum extinction Econt(B - V) ˜ 0.1) and find star formation rates of a few tens of solar masses per year. We use our inferred masses to determine a mean specific star formation rate for this sample of ˜10-9 yr-1, and compare this to the specific star formation rates in distant Lyman-break galaxies (LBGs), and in other low-redshift populations. We conclude that our sample's characteristics overlap significantly with those of the z ˜ 5 LBG population, making ours the first local analogue population well tuned to match those high-redshift galaxies. We consider implications for the origin and evolution of early galaxies.

  10. Star Formation in Low-Mass Star-Forming Galaxies at intermediate redshifts

    NASA Astrophysics Data System (ADS)

    Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Gomez-Guijarro, Carlos

    2015-08-01

    Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that low-mass systems merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf systems might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of low-mass systems at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of low-mass dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present Star Formation properties of a sample of low-mass Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFRs and overall properties were obtained through the analysis of their spectral energy distributions based on (1) HST and ground-based multi-broadband photometry and (2) deep spectroscopy from VLT and GTC telescopes.The SFRs and stellar masses derived for both samples place our targets on the standard main sequence of star-forming galaxies, but extending the sequence at least one dex to low mass systems.

  11. New fully empirical calibrations for strong-line metallicity indicators in star forming galaxies

    NASA Astrophysics Data System (ADS)

    Curti, M.; Cresci, G.; Mannucci, F.; Marconi, A.; Maiolino, R.; Esposito, S.

    2016-06-01

    We derive new empirical calibrations for strong-line diagnostics of gas phase metallicity in local star forming galaxies by uniformly applying the Te method over the full metallicity range probed by the Sloan Digital Sky Survey (SDSS). To measure electron temperatures at high metallicity, where the auroral lines needed are not detected in single galaxies, we stacked spectra of more than 110000 galaxies from the SDSS in bins of log[O II]/Hβ and log[O III]/Hβ. This stacking scheme does not assume any dependence of metallicity on mass or star formation rate, but only that galaxies with the same line ratios have the same oxygen abundance. We provide calibrations which span more than 1 dex in metallicity and are entirely defined on a consistent absolute Te metallicity scale for galaxies. We apply our calibrations to the SDSS sample and find that they provide consistent metallicity estimates to within 0.05 dex.

  12. The Hercules Cluster Environment Impact on the Chemical History of Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Petropoulou, V.; VíLchez, J. M.; Iglesias-Páramo, J.; Papaderos, P.

    In this work we study the effects of the Hercules cluster environment on the chemical history of star-forming (SF) galaxies. For this purpose we have derived the gas metallicities, the mean stellar metallicities and ages, the masses and the luminosities of our sample of galaxies. We have found that our Hercules SF galaxies are either chemically evolved spirals with nearly flat oxygen gradients, or less metal-rich dwarf galaxies which appear to be the "newcomers" in the cluster. Most Hercules SF galaxies follow well defined mass-metallicity and luminosity-metallicity sequences; nevertheless significant outliers to these relations have been identified, illustrating how environmental effects can provide a physical source of dispersion in these fundamental relations.

  13. The formation and assembly of a typical star-forming galaxy at redshift z approximately 3.

    PubMed

    Stark, Daniel P; Swinbank, A Mark; Ellis, Richard S; Dye, Simon; Smail, Ian R; Richard, Johan

    2008-10-01

    Recent studies of galaxies approximately 2-3 Gyr after the Big Bang have revealed large, rotating disks, similar to those of galaxies today. The existence of well-ordered rotation in galaxies during this peak epoch of cosmic star formation indicates that gas accretion is likely to be the dominant mode by which galaxies grow, because major mergers of galaxies would completely disrupt the observed velocity fields. But poor spatial resolution and sensitivity have hampered this interpretation; such studies have been limited to the largest and most luminous galaxies, which may have fundamentally different modes of assembly from those of more typical galaxies (which are thought to grow into the spheroidal components at the centres of galaxies similar to the Milky Way). Here we report observations of a typical star-forming galaxy at z = 3.07, with a linear resolution of approximately 100 parsecs. We find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely to be assembling a spheroidal bulge similar to those seen in spiral galaxies at the present day. The presence of undisrupted rotation may indicate that galaxies such as the Milky Way gain much of their mass by accretion rather than major mergers.

  14. SHOCKED SUPERWINDS FROM THE z {approx} 2 CLUMPY STAR-FORMING GALAXY, ZC406690

    SciTech Connect

    Newman, Sarah F.; Genzel, Reinhard; Shapiro Griffin, Kristen; Davies, Ric; Foerster-Schreiber, Natascha M.; Tacconi, Linda J.; Kurk, Jaron; Wuyts, Stijn; Genel, Shy; Buschkamp, Peter; Eisenhauer, Frank; Lutz, Dieter; Lilly, Simon J.; Carollo, C. Marcella; Renzini, Alvio; Mancini, Chiara; Bouche, Nicolas; Burkert, Andreas; Cresci, Giovanni; Hicks, Erin; and others

    2012-06-20

    We have obtained high-resolution data of the z {approx} 2 ring-like, clumpy star-forming galaxy (SFG) ZC406690 using the VLT/SINFONI with adaptive optics (in K band) and in seeing-limited mode (in H and J bands). Our data include all of the main strong optical emission lines: [O II], [O III], H{alpha}, H{beta}, [N II], and [S II]. We find broad, blueshifted H{alpha} and [O III] emission line wings in the spectra of the galaxy's massive, star-forming clumps ({sigma} {approx} 85 km s{sup -1}) and even broader wings (up to 70% of the total H{alpha} flux, with {sigma} {approx} 290 km s{sup -1}) in regions spatially offset from the clumps by {approx}2 kpc. The broad emission likely originates from large-scale outflows with mass outflow rates from individual clumps that are 1-8 Multiplication-Sign the star formation rate (SFR) of the clumps. Based on emission line ratio diagnostics ([N II]/H{alpha} and [S II]/H{alpha}) and photoionization and shock models, we find that the emission from the clumps is due to a combination of photoionization from the star-forming regions and shocks generated in the outflowing component, with 5%-30% of the emission deriving from shocks. In terms of the ionization parameter (6 Multiplication-Sign 10{sup 7} to 10{sup 8} cm s{sup -1}, based on both the SFR and the O{sub 32} ratio), density (local electron densities of 300-1800 cm{sup -3} in and around the clumps, and ionized gas column densities of 1200-8000 M{sub Sun }pc{sup -2}), and SFR (10-40 M{sub Sun} yr{sup -1}), these clumps more closely resemble nuclear starburst regions of local ultraluminous infrared galaxies and dwarf irregulars than H II regions in local galaxies. However, the star-forming clumps are not located in the nucleus as in local starburst galaxies but instead are situated in a ring several kpc from the center of their high-redshift host galaxy, and have an overall disk-like morphology. The two brightest clumps are quite different in terms of their internal properties

  15. Color-magnitude Diagrams of the Star-forming Galaxies Ho IX, Cam B, NGC 2976, and UGC 1281

    NASA Astrophysics Data System (ADS)

    Georgiev, T. B.; Bomans, D. J.

    We report results on a study of nearby late type galaxies performed with the 2m RC telescope of the Rozhen NAO with with 1×1 K CCD camera. The scale and the frame size are 0.32''/pix and 5.4'×5.4', respectively. At typical seeing of 1'' the data reach routinely a limiting magnitude of ˜4 mag. With these parameters many nearby galaxies, including the members of the IC 342 and M81 groups can be resolved into star-like and diffuse objects. This allows the determination of several fundamental properties of the galaxies, based on surface photometry and study of the brightest resolved objects. The most crucial parameter is the distance to the galaxy. It can be estimated to a standard error of 20 % using the brightest red and blue stars. Selection of these stars is greatly improved by analysis of the image shapes, which allows to detect diffuse objects, like cluster candidates and background galaxies. Further improvement gives the analysis of color-magnitude (CMD) and color-color diagrams. The CMDs also allow to estimate the age of the most recent star formation event and may hint at the metallicity. The CMDs of the low surface brightness irregular galaxies Ho IX and Cam B are very similar. Especially Cam B seems to be an extreme case of a low-mass star-forming dwarf galaxy. The CMD of NGC 2976 is very similar to this of the star burst galaxy M82 (Georgiev T., 2000, Compt. Rend. Acad. Bulg. Sci. 53/2, 5-8). The edge-on galaxy UGC 1281 is of intermediate star-forming activity, but the CMD is quite sparse.

  16. The history of star-forming galaxies in the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Asari, N. V.; Cid Fernandes, R.; Stasińska, G.; Torres-Papaqui, J. P.; Mateus, A.; Sodré, L.; Schoenell, W.; Gomes, J. M.

    2007-10-01

    This paper, the sixth in the Semi-Empirical Analysis of Galaxies series, studies the evolution of 82302 star-forming (SF) galaxies from the Sloan Digital Sky Survey. Star formation histories (SFHs) are derived from detailed spectral fits obtained with our publicly available spectral synthesis code STARLIGHT. Our main goals are to explore new ways to derive SFHs from the synthesis results and apply them to investigate how SFHs vary as a function of nebular metallicity (Zneb). A number of refinements over our previous work are introduced, including (1) an improved selection criterion; (2) a careful examination of systematic residuals around Hβ (3) self-consistent determination of nebular extinctions and metallicities; (4) tests with several Zneb estimators; (5) a study of the effects of the reddening law adopted and of the relation between nebular and stellar extinctions and the interstellar component of the NaI D doublet. Our main achievements may be summarized as follows. (1) A conventional correlation analysis is performed to study how global properties relate to Zneb, leading to the confirmation of previously known relations, such as those between Zneb and galaxy luminosity, mass, dust content, mean stellar metallicity and mean stellar age. (2) A simple formalism which compresses the results of the synthesis while at the same time yielding time-dependent star formation rates (SFR) and mass assembly histories is presented. (3) A comparison of the current SFR derived from the population synthesis with that obtained from Hα shows that these independent estimators agree very well, with a scatter of a factor of 2. An important corollary of this finding is that we now have a way to estimate SFR in galaxies hosting active galactic nuclei, where the Hα method cannot be applied. (4) Fully time-dependent SFHs were derived for all galaxies, and then averaged over six Zneb bins spanning the entire SF wing in the diagram. (5) We find that SFHs vary systematically along the

  17. LUMINOUS STAR-FORMING GALAXIES IN THE GALAXY EVOLUTION EXPLORER-SLOAN DIGITAL SKY SURVEY DATABASE

    SciTech Connect

    Hutchings, J. B.; Bianchi, L.

    2010-02-15

    We have a Galaxy Evolution Explorer-Sloan Digital Sky Survey sample that isolates intermediate redshift QSOs. Some 1% of the spectroscopic sample consists of galaxies in starburst or post-starburst stages. We discuss the most luminous 10 of these, which have redshifts between 0.18 and 0.6. We present spectroscopic measures and derive star formation rates. Two of the six with Mg II coverage reveal outflows in this line. None shows any sign of active galactic nucleus activity. We discuss their star formation histories and their place in galaxy evolution.

  18. In-Situ View of Star-forming Galaxies at Cosmic Noon

    NASA Astrophysics Data System (ADS)

    Foerster Schreiber, Natascha M.

    2015-08-01

    Building on the ever-growing body of multiwavelength extragalactic surveys, spatially- and spectrally-resolved studies are providing new and unique insights into the physical and dynamical processes that drive the star formation and mass assembly of galaxies since as early as a few billion years after the Big Bang. I will present recent key progress in our understanding of galaxy evolution from state-of-the-art optical, near-IR, and submillimeter observations of massive star-forming galaxies around the peak epoch of cosmic star formation density, with an emphasis on high redshift disks. I will discuss implications on the star formation properties, feedback mechanisms, and early life cycle of z ~ 1 - 3 galaxies, and will highlight current challenges and emerging science questions.

  19. What Turns Galaxies Off? the Different Morphologies of Star-Forming and Quiescent Galaxies Since z Approximates 2 from CANDELS

    NASA Technical Reports Server (NTRS)

    Bell, Eric F.; VanDerWel, Arjen; Papovich, Casey; Kocevski, Dale; Lotz, Jennifer; McIntosh, Daniel H.; Kartaltepe, Jeyhan; Faber, S. M.; Ferguson, Harry; Koekemoer, Anton; Grogin, Norman; Wuyts, Stijn; Cheung, Edmong; Conselice, Christopher J.; Dunlop, James S.; Giavalisco, Mauro; Herrington, Jessica; Koo, David; McGrath, Elizabeth J.; DeMello, Duilia; Rix, Hans-Walter; Robaina, Aday R.; Williams, Christina C.

    2011-01-01

    We use HST/WFC3 imaging from the CANDELS multicyc1e treasury survey, in conjunction with the Sloan Digital Sky Survey, to explore the evolution of galactic structure for galaxies with stellar masses > 3 x 10(exp 10) Solar Mass from Z= 2.2 to the present epoch, a time span of 10 Gyr. We explore the relationship between rest-frame optical color, stellar mass, star formation activity and the structural parameters of galaxies as determined from parametric fits to the surface brightness profiles of galaxies. We confirm the dramatic evolution from z= 2.2 to the present day in the number density of non-star-forming galaxies above 3 x 10(exp 10) Solar Mass reported by other authors. We find that the vast majority of these quiescent systems have concentrated light profiles, as parameterized by the Sersic index, and the population of concentrated galaxies grows similarly rapidly. We examine the joint distribution of star formation activity, Sersic index, stellar mass, mass divided by radius (a proxy for velocity dispersion), and stellar surface density. Quiescence correlates poorly with stellar mass at all z < 2.2 (given the approx < 0.2 dex scatter between halo mass and stellar mass at z approximates 0 inferred by More et al, this argues against halo mass being the only factor determining quiescence). Quiescence correlates better with Sersic index, 'velocity dispersion' and stellar surface density, where Sersic index correlates the best (increasingly so at lower redshift). Yet, there is significant scatter between quiescence and galaxy structure: while the vast majority of quiescent galaxies have prominent bulges, many of them have significant disks, and a number of bulge-dominated galaxies have significant star formation. Noting the rarity of quiescent galaxies without prominent bulges, we argue that a prominent bulge (and, perhaps by association, a supermassive black hole) is a necessary but not sufficient condition for quenching star formation on galactic scales over the

  20. The growth of the central region by acquisition of counterrotating gas in star-forming galaxies

    PubMed Central

    Chen, Yan-Mei; Shi, Yong; Tremonti, Christy A.; Bershady, Matt; Merrifield, Michael; Emsellem, Eric; Jin, Yi-Fei; Huang, Song; Fu, Hai; Wake, David A.; Bundy, Kevin; Stark, David; Lin, Lihwai; Argudo-Fernandez, Maria; Bergmann, Thaisa Storchi; Bizyaev, Dmitry; Brownstein, Joel; Bureau, Martin; Chisholm, John; Drory, Niv; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Lopes, Alexandre Roman; Pan, Kai-Ke; Riffel, Rogemar A.; Thomas, Daniel; Wang, Lan; Westfall, Kyle; Yan, Ren-Bin

    2016-01-01

    Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars. PMID:27759033

  1. Modeling tracers of young stellar population age in star-forming galaxies

    SciTech Connect

    Levesque, Emily M.; Leitherer, Claus

    2013-12-20

    The young stellar population of a star-forming galaxy is the primary engine driving its radiative properties. As a result, the age of a galaxy's youngest generation of stars is critical for a detailed understanding of its star formation history, stellar content, and evolutionary state. Here we present predicted equivalent widths for the Hβ, Hα, and Brγ recombination lines as a function of stellar population age. The equivalent widths are produced by the latest generations of stellar evolutionary tracks and the Starburst99 stellar population synthesis code, and are the first to fully account for the combined effects of both nebular emission and continuum absorption produced by the synthetic stellar population. Our grid of model stellar populations spans six metallicities (0.001 < Z < 0.04), two treatments of star formation history (a 10{sup 6} M {sub ☉} instantaneous burst and a continuous star formation rate of 1 M {sub ☉} yr{sup –1}), and two different treatments of initial rotation rate (v {sub rot} = 0.0v {sub crit} and 0.4v {sub crit}). We also investigate the effects of varying the initial mass function. Given constraints on galaxy metallicity, our predicted equivalent widths can be applied to observations of star-forming galaxies to approximate the age of their young stellar populations.

  2. Searching for star-forming dwarf galaxies in the Antlia cluster

    NASA Astrophysics Data System (ADS)

    Vaduvescu, O.; Kehrig, C.; Bassino, L. P.; Smith Castelli, A. V.; Calderón, J. P.

    2014-03-01

    Context. The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. Aims: In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Methods: Using the Gemini South and GMOS camera, we acquired the Hα imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived KS magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. Results: FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, KS surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any Hα emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Conclusions: Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data. Based on observations acquired at Gemini South (GS-2010A-Q-51 and GS-2012A-Q-59) and ESO VISTA Hemisphere Survey (VHS).

  3. Spectral synthesis of star-forming galaxies in the near-infrared

    NASA Astrophysics Data System (ADS)

    Martins, Lucimara P.; Rodríguez-Ardila, Alberto; Diniz, Suzi; Riffel, Rogério; de Souza, Ronaldo

    2013-11-01

    The near-infrared spectral region is becoming a very useful wavelength range to detect and quantify the stellar population of galaxies. Models are developing to predict the contribution of the thermally pulsating stars on the asymptotic giant branch stars that should dominate the near-infrared region (NIR) spectra of populations 0.3 to 2 Gyr old. When present in a given stellar population, these stars leave unique signatures that can be used to detect them unambiguously. However, these models have to be tested in a homogeneous data base of star-forming galaxies, to check if the results are consistent with what is found from different wavelength ranges. In this work, we performed stellar population synthesis on the nuclear and extended regions of 23 star-forming galaxies to understand how the star formation tracers in the NIR can be used in practice. The stellar population synthesis shows that for the galaxies with strong emission in the NIR, there is an important fraction of young/intermediate population contributing to the spectra, which is probably the ionization source in these galaxies. Galaxies that had no emission lines measured in the NIR were found to have older average ages and less contribution of young populations. Although the stellar population synthesis method proved to be very effective to find the young ionizing population in these galaxies, no clear correlation between these results and the NIR spectral indexes were found. Thus, we believe that, in practice, the use of these indexes is still very limited due to observational limitations.

  4. The structure of the interstellar medium of star-forming galaxies

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    We develop and implement numerical methods for including stellar feedback in galaxy-scale numerical simulations. Our models include simplified treatments of heating by Type I and Type II supernovae, gas recycling from young stars and asymptotic giant branch winds, heating from the shocked stellar winds, H II photoionization heating and radiation pressure from stellar photons. The energetics and time dependence associated with the feedback are taken directly from stellar evolution models. We implement these stellar feedback models in smoothed particle hydrodynamic simulations with pc-scale resolution, modelling galaxies from Small Magellanic Cloud (SMC) like dwarfs and Milky Way (MW) analogues to massive z˜ 2 star-forming discs. In the absence of stellar feedback, gas cools rapidly and collapses without limit into dense sub-units, inconsistent with observations. By contrast, in all cases with feedback, the interstellar medium (ISM) quickly approaches a statistical steady state in which giant molecular clouds (GMCs) continuously form, disperse and re-form, leading to a multiphase ISM. In this paper, we quantify the properties of the ISM and GMCs in this self-regulated state. In a companion paper we study the galactic winds driven by stellar feedback. Our primary results on the structure of the ISM in star-forming galaxies include the following. 1. Star-forming galaxies generically self-regulate so that the cool, dense gas maintains Toomre's Q˜ 1. Most of the volume is occupied by relatively diffuse hot gas, while most of the mass is in dense GMC complexes created by self-gravity. The phase structure of the gas and the gas mass fraction at high densities are much more sensitive probes of the physics of stellar feedback than integrated quantities such as the Toomre Q or gas velocity dispersion. 2. Different stellar feedback mechanisms act on different spatial (and density) scales. Radiation pressure and H II gas pressure are critical for preventing runaway collapse

  5. Chandra Sees Wealth Of Black Holes In Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    2001-06-01

    NASA's Chandra X-ray Observatory has found new populations of suspected mid-mass black holes in several starburst galaxies, where stars form and explode at an unusually high rate. Although a few of these objects had been found previously, this is the first time they have been detected in such large numbers and could help explain their relationship to star formation and the production of even more massive black holes. At the 198th meeting of the American Astronomical Society in Pasadena, California, three independent teams of scientists reported finding dozens of X-ray sources in galaxies aglow with star formation. These X-ray objects appear point-like and are ten to a thousand times more luminous in X-rays than similar sources found in our Milky Way and the M81 galaxy. "Chandra gives us the ability to study the populations of individual bright X-ray sources in nearby galaxies in extraordinary detail," said Andreas Zezas, lead author from the Harvard-Smithsonian Center for Astrophysics team that observed The Antennae, a pair of colliding galaxies, and M82, a well-known starburst galaxy. "This allows us to build on earlier detections of these objects and better understand their relationship to starburst galaxies." Antennae-True Color Image True Color Image of Antennae Credit: NASA/SAO/G.Fabbiano et al. Press Image and Caption Kimberly Weaver, of NASA's Goddard Space Flight Center in Greenbelt, MD, lead scientist of the team that studied the starburst galaxy NGC 253, discussed the importance of the unusual concentration of these very luminous X-ray sources near the center of that galaxy. Four sources, which are tens to thousands of times more massive than the Sun, are located within 3,000 light years of the galaxy core. "This may imply that these black holes are gravitating toward the center of the galaxy where they could coalesce to form a single supermassive black hole," Weaver suggested. "It could be that this starburst galaxy is transforming itself into a quasar

  6. THE CHEMICAL EVOLUTION OF STAR-FORMING GALAXIES OVER THE LAST 11 BILLION YEARS

    SciTech Connect

    Zahid, H. Jabran; Kewley, Lisa J.; Geller, Margaret J.; Hwang, Ho Seong; Fabricant, Daniel G.; Kurtz, Michael J.

    2013-07-10

    We calculate the stellar mass-metallicity relation at five epochs ranging to z {approx} 2.3. We quantify evolution in the shape of the mass-metallicity relation as a function of redshift; the mass-metallicity relation flattens at late times. There is an empirical upper limit to the gas-phase oxygen abundance in star-forming galaxies that is independent of redshift. From examination of the mass-metallicity relation and its observed scatter, we show that the flattening at late times is a consequence of evolution in the stellar mass where galaxies enrich to this empirical upper metallicity limit; there is also evolution in the fraction of galaxies at a fixed stellar mass that enrich to this limit. The stellar mass where metallicities begin to saturate is {approx}0.7 dex smaller in the local universe than it is at z {approx} 0.8.

  7. AN OBJECTIVE DEFINITION FOR THE MAIN SEQUENCE OF STAR-FORMING GALAXIES

    SciTech Connect

    Renzini, Alvio; Peng, Ying-jie E-mail: y.peng@mrao.cam.ac.uk

    2015-03-10

    The main sequence (MS) of star-forming (SF) galaxies plays a fundamental role in driving galaxy evolution and our efforts to understand it. However, different studies find significant differences in the normalization, slope, and shape of the MS. These discrepancies arise mainly from the different selection criteria adopted to isolate SF galaxies, which may include or exclude galaxies with a specific star formation rate (SFR) substantially below the MS value. To obviate this limitation of all current criteria, we propose an objective definition of the MS that does not rely at all on a pre-selection of SF galaxies. Constructing the 3D SFR–mass–number plot, the MS is then defined as the ridge line of the SF peak, as illustrated with various figures. The advantages of such a definition are manifold. If generally adopted, it will facilitate the inter-comparison of results from different groups using the same SFR and stellar mass diagnostics, or it will highlight the relative systematics of different diagnostics. All of this could help to understand MS galaxies as systems in a quasi-steady state equilibrium and would also provide a more objective criterion for identifying quenching galaxies.

  8. Ultraviolet ISM Diagnostics for Star-forming Galaxies. I. Tracers of Metallicity and Extinction

    NASA Astrophysics Data System (ADS)

    Zetterlund, Erika; Levesque, Emily M.; Leitherer, Claus; Danforth, Charles W.

    2015-06-01

    We have observed a sample of 14 nearby (z˜ 0.03) star-forming blue compact galaxies (BCGs) in the rest-frame far-UV (˜1150-2200 Å) using the Cosmic Origins Spectrograph on the Hubble Space Telescope. We have also generated a grid of stellar population synthesis models using the Starburst99 evolutionary synthesis code, allowing us to compare observations and theoretical predictions for the Si iv_1400 and C iv_1550 UV indices; both are comprised of a blend of stellar wind and interstellar lines and have been proposed as metallicity diagnostics in the UV. Our models and observations both demonstrate that there is a positive linear correlation with metallicity for both indices, and we find generally good agreement between our observations and the predictions of the Starburst99 models (with the models slightly under-estimating the value of the indices due to contributions from interstellar lines not simulated by a stellar population synthesis code). By combining the rest-frame UV observations with pre-existing rest-frame optical spectrophotometry of our BCG sample, we also directly compare the predictions of metallicity and extinction diagnostics across both wavelength regimes. This comparison reveals a correlation between the UV absorption and optical strong-line diagnostics, offering the first means of directly comparing interstellar medium (ISM) properties determined across different rest-frame regimes. Finally, using our Starburst99 model grid, we determine theoretical values for the short-wavelength UV continuum slope, {{β }18}, which can be used for determining extinction in rest-frame UV spectra of star-forming galaxies. We consider the implications of these results and discuss future work aimed at parameterizing these and other environmental diagnostics in the UV (a suite of diagnostics that could offer particular utility in the study of star-forming galaxies at high redshift) as well as the development of robust comparisons between ISM diagnostics across a

  9. The rest-frame submillimeter spectrum of high-redshift, dusty, star-forming galaxies

    SciTech Connect

    Spilker, J. S.; Marrone, D. P.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bothwell, M. S.; Brodwin, M.; Carlstrom, J. E.; Crawford, T. M.; Chapman, S. C.; De Breuck, C.; Gullberg, B.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Holzapfel, W. L.; and others

    2014-04-20

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of {sup 12}CO, [C I], and H{sub 2}O, we also detect several faint transitions of {sup 13}CO, HCN, HNC, HCO{sup +}, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the {sup 13}CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which {sup 13}CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO{sup +}, and CN is consistent with a warm, dense medium with T {sub kin} ∼ 55 K and n{sub H{sub 2}}≳10{sup 5.5} cm{sup –3}. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

  10. The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Spilker, J. S.; Marrone, D. P.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bradford, C. M.; Bothwell, M. S.; Brodwin, M.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; de Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Gullberg, B.; Hezaveh, Y.; Holzapfel, W. L.; Husband, K.; Ma, J.; Malkan, M.; Murphy, E. J.; Reichardt, C. L.; Rotermund, K. M.; Stalder, B.; Stark, A. A.; Strandet, M.; Vieira, J. D.; Weiß, A.; Welikala, N.

    2014-04-01

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of 12CO, [C I], and H2O, we also detect several faint transitions of 13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the 13CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which 13CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense medium with T kin ~ 55 K and n_{H_2} \\gtrsim 10^{5.5} cm-3. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

  11. Young, Ultraviolet-bright Stars Dominate Dust Heating in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Law, Ka-Hei; Gordon, Karl D.; Misselt, K. A.

    2011-09-01

    In star-forming galaxies, dust plays a significant role in shaping the ultraviolet (UV) through infrared (IR) spectrum. Dust attenuates the radiation from stars, and re-radiates the energy through equilibrium and non-equilibrium emission. Polycyclic aromatic hydrocarbons (PAHs), graphite, and silicates contribute to different features in the spectral energy distribution; however, they are all highly opaque in the same spectral region—the UV. Compared to old stellar populations, young populations release a higher fraction of their total luminosity in the UV, making them a good source of the energetic UV photons that can power dust emission. However, given their relative abundance, the question of whether young or old stellar populations provide most of these photons that power the IR emission is an interesting question. Using three samples of galaxies observed with the Spitzer Space Telescope and our dusty radiative transfer model, we find that young stellar populations (on the order of 100 million years old) dominate the dust heating in star-forming galaxies, and old stellar populations (13 billion years old) generally contribute less than 20% of the far-IR luminosity.

  12. YOUNG, ULTRAVIOLET-BRIGHT STARS DOMINATE DUST HEATING IN STAR-FORMING GALAXIES

    SciTech Connect

    Law, Ka-Hei; Gordon, Karl D.; Misselt, K. A. E-mail: kgordon@stsci.edu

    2011-09-10

    In star-forming galaxies, dust plays a significant role in shaping the ultraviolet (UV) through infrared (IR) spectrum. Dust attenuates the radiation from stars, and re-radiates the energy through equilibrium and non-equilibrium emission. Polycyclic aromatic hydrocarbons (PAHs), graphite, and silicates contribute to different features in the spectral energy distribution; however, they are all highly opaque in the same spectral region-the UV. Compared to old stellar populations, young populations release a higher fraction of their total luminosity in the UV, making them a good source of the energetic UV photons that can power dust emission. However, given their relative abundance, the question of whether young or old stellar populations provide most of these photons that power the IR emission is an interesting question. Using three samples of galaxies observed with the Spitzer Space Telescope and our dusty radiative transfer model, we find that young stellar populations (on the order of 100 million years old) dominate the dust heating in star-forming galaxies, and old stellar populations (13 billion years old) generally contribute less than 20% of the far-IR luminosity.

  13. IROCKS: Spatially Resolved Kinematics of z ∼ 1 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Mieda, Etsuko; Wright, Shelley A.; Larkin, James E.; Armus, Lee; Juneau, Stéphanie; Salim, Samir; Murray, Norman

    2016-11-01

    We present results from the Intermediate Redshift OSIRIS Chemo-Kinematic Survey (IROCKS) for sixteen z ∼ 1 and one z ∼ 1.4 star-forming galaxies. All galaxies were observed with OSIRIS with the laser guide star adaptive optics system at Keck Observatory. We use rest-frame nebular Hα emission lines to trace morphologies and kinematics of ionized gas in star-forming galaxies on sub-kiloparsec physical scales. We observe elevated velocity dispersions (σ ≳ 50 km s‑1) seen in z > 1.5 galaxies persist at z ∼ 1 in the integrated galaxies. Using an inclined disk model and the ratio of v/σ , we find that 1/3 of the z ∼ 1 sample are disk candidates while the other 2/3 of the sample are dominated by merger-like and irregular sources. We find that including extra attenuation toward H ii regions derived from stellar population synthesis modeling brings star formation rates (SFRs) using Hα and stellar population fit into a better agreement. We explore the properties of the compact Hα sub-component, or “clump,” at z ∼ 1 and find that they follow a similar size–luminosity relation as local H ii regions but are scaled-up by an order of magnitude with higher luminosities and sizes. Comparing the z ∼ 1 clumps to other high-redshift clump studies, we determine that the clump SFR surface density evolves as a function of redshift. This suggests clump formation is directly related to the gas fraction in these systems and may support disk fragmentation as their formation mechanism since gas fraction scales with redshift.

  14. Physical properties of low-mass star-forming galaxies at intermediate redshifts (z <1)

    NASA Astrophysics Data System (ADS)

    Gallego, J.; Rodríguez-Muñoz, L.; Pacifici, C.; Tresse, L.; Charlot, S.; Gil de Paz, A.; Barro, G.; Villar, V.

    2015-05-01

    In this poster we present the physical properties of a sample of low-mass star-forming galaxies at intermediate redshifts (z<1). We selected a population of dwarf galaxies because dwarf galaxies play a key role in galaxy formation and evolution: (1) they resemble the first structures that hierarchical models predict to form first in the Universe (Dekel & Silk 1986) and that are responsible for the reionization process (Bouwens et al. 2012); and (2) the way or epoch they form and how they evolve are still open questions of modern astrophysics. We selected the sample on the CDFS field. Photometry (40 bands, from UV to far-IR) and preliminary photometric redshifts and stellar masses were obtained from RAINBOW database (Pérez-González et al. 2008). Morphology fom Griffith et al. (2012). Main selection was done by stellar mass, selecting those galaxies with stellar mass M_*<10^8 {M}_⊙. Spectroscopic redshifts were obtained from deep (4 h) MOS spectroscopy with the VIMOS spectrograph at VLT. The average spectrum is characterized by a faint, blue and flat continuum and strong emission lines, revealing that the systems are dominated by an undergoing star formation burst. SFRs and stellar masses are consistent with the SF main-squence over a 2 dex range. More massive objects show higher SFRs than low-mass objects, following the SF main sequence. Distant dwarfs and BCDs follow the overall star-forming sequence in the excitation-luminosity diagram, populating the high excitation, low metallicity and high strength region.

  15. Molecular and atomic gas along and across the main sequence of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Saintonge, Amelie; Catinella, Barbara; Cortese, Luca; Genzel, Reinhard; Giovanelli, Riccardo; Haynes, Martha P.; Janowiecki, Steven; Kramer, Carsten; Lutz, Katharina A.; Schiminovich, David; Tacconi, Linda J.; Wuyts, Stijn; Accurso, Gioacchino

    2016-10-01

    We use spectra from the ALFALFA, GASS and COLD GASS surveys to quantify variations in the mean atomic and molecular gas mass fractions throughout the SFR-M* plane and along the main sequence (MS) of star-forming galaxies. Although galaxies well below the MS tend to be undetected in the Arecibo and IRAM observations, reliable mean atomic and molecular gas fractions can be obtained through a spectral stacking technique. We find that the position of galaxies in the SFR-M* plane can be explained mostly by their global cold gas reservoirs as observed in the H I line, with in addition systematic variations in the molecular-to-atomic ratio and star formation efficiency. When looking at galaxies within ±0.4 dex of the MS, we find that as stellar mass increases, both atomic and molecular gas mass fractions decrease, stellar bulges become more prominent, and the mean stellar ages increase. Both star formation efficiency and molecular-to-atomic ratios vary little for massive MS galaxies, indicating that the flattening of the MS is due to the global decrease of the cold gas reservoirs of galaxies rather than to bottlenecks in the process of converting cold atomic gas to stars.

  16. Flat rotation curves and low velocity dispersions in KMOS star-forming galaxies at z ~ 1

    NASA Astrophysics Data System (ADS)

    Di Teodoro, E. M.; Fraternali, F.; Miller, S. H.

    2016-10-01

    The study of the evolution of star-forming galaxies requires the determination of accurate kinematics and scaling relations out to high redshift. In this paper we select a sample of 18 galaxies at z ~ 1, observed in the Hα emission line with KMOS, to derive accurate kinematics using a novel 3D analysis technique. We use the new code 3DBarolo, which models the galaxy emission directly in 3D observational space, without the need to extract kinematic maps. This major advantage of this technique is that it is not affected by beam smearing and thus it enables the determination of rotation velocity and intrinsic velocity dispersion, even at low spatial resolution. We find that (1) the rotation curves of these z ~ 1 galaxies rise very steeply within few kiloparsecs and remain flat out to the outermost radius and (2) the Hα velocity dispersions are low, ranging from 15 to 40 km s-1, which leads to V/σ = 3-10. These characteristics are similar to those of disc galaxies in the local Universe. Finally, we also report no significant evolution of the stellar-mass Tully-Fisher relation. Our results show that disc galaxies are kinematically mature and rotation-dominated at z ~ 1 already. The reduced datacubes as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A77

  17. Metallicity inhomogeneities in local star-forming galaxies as a sign of recent metal-poor gas accretion

    SciTech Connect

    Sánchez Almeida, J.; Morales-Luis, A. B.; Muñoz-Tuñón, C.; Méndez-Abreu, J.; Elmegreen, D. M.; Elmegreen, B. G. E-mail: abml@iac.es E-mail: elmegreen@vassar.edu E-mail: jma20@st-andrews.ac.uk

    2014-03-01

    We measure the oxygen metallicity of the ionized gas along the major axis of seven dwarf star-forming galaxies. Two of them, SDSSJ1647+21 and SDSSJ2238+14, show ≅0.5 dex metallicity decrements in inner regions with enhanced star formation activity. This behavior is similar to the metallicity drop observed in a number of local tadpole galaxies by Sánchez Almeida et al., and was interpreted as showing early stages of assembling in disk galaxies, with the star formation sustained by external metal-poor gas accretion. The agreement with tadpoles has several implications. (1) It proves that galaxies other than the local tadpoles present the same unusual metallicity pattern. (2) Our metallicity inhomogeneities were inferred using the direct method, thus discarding systematic errors usually attributed to other methods. (3) Taken together with the tadpole data, our findings suggest a threshold around one-tenth the solar value for the metallicity drops to show up. Although galaxies with clear metallicity drops are rare, the physical mechanism responsible for them may sustain a significant part of the star formation activity in the local universe. We argue that the star formation dependence of the mass-metallicity relationship, as well as other general properties followed by most local disk galaxies, is naturally interpreted as side effects of pristine gas infall. Alternatives to the metal-poor gas accretion are examined as well.

  18. [C II] LINE EMISSION IN MASSIVE STAR-FORMING GALAXIES AT z = 4.7

    SciTech Connect

    Wagg, J.; Aravena, M.; Martin, S.; Wiklind, T.; Peck, A.; Barkats, D.; Cortes, J. R.; Hills, R.; Hodge, J.; Impellizzeri, C. M V.; Rawlings, M. G.; Carilli, C. L.; Espada, D.; Iono, D.; Riechers, D.; Walter, F.; Wootten, A.; Leroy, A.; Maiolino, R.; McMahon, R. G.; and others

    2012-06-20

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C II] 157.7 {mu}m fine structure line and thermal dust continuum emission from a pair of gas-rich galaxies at z = 4.7, BR1202-0725. This system consists of a luminous quasar host galaxy and a bright submillimeter galaxy (SMG), while a fainter star-forming galaxy is also spatially coincident within a 4'' (25 kpc) region. All three galaxies are detected in the submillimeter continuum, indicating FIR luminosities in excess of 10{sup 13} L{sub Sun} for the two most luminous objects. The SMG and the quasar host galaxy are both detected in [C II] line emission with luminosities L{sub [CII]} = (10.0 {+-} 1.5) Multiplication-Sign 10{sup 9} L{sub Sun} and L{sub [CII]} = (6.5 {+-} 1.0) Multiplication-Sign 10{sup 9} L{sub Sun }, respectively. We estimate a luminosity ratio L{sub [CII]}/L{sub FIR} = (8.3 {+-} 1.2) Multiplication-Sign 10{sup -4} for the starburst SMG to the north and L{sub [CII]}/L{sub FIR} = (2.5 {+-} 0.4) Multiplication-Sign 10{sup -4} for the quasar host galaxy, in agreement with previous high-redshift studies that suggest lower [C II]-to-FIR luminosity ratios in quasars than in starburst galaxies. The third fainter object with a flux density S{sub 340GHz} = 1.9 {+-} 0.3 mJy is coincident with a Ly{alpha} emitter and is detected in HST ACS F775W and F814W images but has no clear counterpart in the H band. Even if this third companion does not lie at a redshift similar to BR1202-0725, the quasar and the SMG represent an overdensity of massive, infrared luminous star-forming galaxies within 1.3 Gyr of the big bang.

  19. I Zw 18, a Template for Star-Forming, z is Greater than 7 Galaxies

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Hubeny, Ivan

    2011-01-01

    I Zw 18-NW, one of the most primitive nearby dwarf galaxies, is arguably the best template we have for star-forming, very high-redshift galaxies (z>7). We have therefore obtained a far-UV spectrum of I Zw 18-NW using Hubble's Cosmic Origins Spectrograph (COS). The spectrum indicates star-formation over the past approx.10 Myr, a very low stellar metallicity, log Z/Zsun approx. -1.7, and high average stellar rotation rate, Vsini approx.200 km/s. Stellar wind lines are very weak, and the edge velocity of wind lines is very low (approx.250 km/s). The overall properties of I Zw 18-NW are consistent with theories of very low metallicity, rapidly rotating stars, e.g. Meynet et al. (2006).

  20. Outflows and complex stellar kinematics in SDSS star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Cicone, C.; Maiolino, R.; Marconi, A.

    2016-04-01

    We investigate the properties of star-formation-driven outflows by using a large spectroscopic sample of ~160 000 local "normal" star-forming galaxies drawn from the Sloan digital sky survey (SDSS), spanning a wide range of star formation rates (SFRs) and stellar masses (M∗). The galaxy sample is divided into a fine grid of bins in the M∗-SFR parameter space, for each of which we produced a composite spectrum by stacking the SDSS spectra of the galaxies contained in that bin together. We exploited the high signal-to-noise of the stacked spectra to study the emergence of faint features of optical emission lines that may trace galactic outflows and are otherwise too faint to detect in individual galaxy spectra. We have adopted a novel approach that relies on the comparison between the line-of-sight velocity distribution (LoSVD) of the ionised gas (as traced by the [OIII]λ5007 and Hα+[NII]λλ6548, 6583 emission lines) and the LoSVD of the stars, which are used as a reference for tracing virial motions. Significant deviations in the gas kinematics from the stellar kinematics in the high-velocity tail of the LoSVDs are interpreted as a signature of outflows. Our results suggest that the incidence of ionised outflows increases with SFR and specific SFR. The outflow velocity (vout) is found to correlate tightly with the SFR for SFR> 1 M⊙ yr-1, whereas the dependence of vout on SFR is nearly flat at lower SFRs. The outflow velocity appears to also increase with the stellar velocity dispersion (σ∗), although this relation has a much larger scatter than the one with SFR, and we infer velocities as high as vout ~ (6-8)σ∗. Strikingly, we detect the signature of ionised outflows only in galaxies located above the main sequence (MS) of star-forming galaxies in the M∗-SFR diagram, and the incidence of such outflows increases sharply with the offset from the MS. This result suggests that star-formation-driven outflows may be responsible for shaping the upper

  1. The large, oxygen-rich halos of star-forming galaxies are a major reservoir of galactic metals.

    PubMed

    Tumlinson, J; Thom, C; Werk, J K; Prochaska, J X; Tripp, T M; Weinberg, D H; Peeples, M S; O'Meara, J M; Oppenheimer, B D; Meiring, J D; Katz, N S; Davé, R; Ford, A B; Sembach, K R

    2011-11-18

    The circumgalactic medium (CGM) is fed by galaxy outflows and accretion of intergalactic gas, but its mass, heavy element enrichment, and relation to galaxy properties are poorly constrained by observations. In a survey of the outskirts of 42 galaxies with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope, we detected ubiquitous, large (150-kiloparsec) halos of ionized oxygen surrounding star-forming galaxies; we found much less ionized oxygen around galaxies with little or no star formation. This ionized CGM contains a substantial mass of heavy elements and gas, perhaps far exceeding the reservoirs of gas in the galaxies themselves. Our data indicate that it is a basic component of nearly all star-forming galaxies that is removed or transformed during the quenching of star formation and the transition to passive evolution.

  2. The large, oxygen-rich halos of star-forming galaxies are a major reservoir of galactic metals.

    PubMed

    Tumlinson, J; Thom, C; Werk, J K; Prochaska, J X; Tripp, T M; Weinberg, D H; Peeples, M S; O'Meara, J M; Oppenheimer, B D; Meiring, J D; Katz, N S; Davé, R; Ford, A B; Sembach, K R

    2011-11-18

    The circumgalactic medium (CGM) is fed by galaxy outflows and accretion of intergalactic gas, but its mass, heavy element enrichment, and relation to galaxy properties are poorly constrained by observations. In a survey of the outskirts of 42 galaxies with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope, we detected ubiquitous, large (150-kiloparsec) halos of ionized oxygen surrounding star-forming galaxies; we found much less ionized oxygen around galaxies with little or no star formation. This ionized CGM contains a substantial mass of heavy elements and gas, perhaps far exceeding the reservoirs of gas in the galaxies themselves. Our data indicate that it is a basic component of nearly all star-forming galaxies that is removed or transformed during the quenching of star formation and the transition to passive evolution. PMID:22096191

  3. The MOSDEF Survey: Excitation Properties of z ˜ 2.3 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Shapley, Alice E.; Reddy, Naveen A.; Kriek, Mariska; Freeman, William R.; Sanders, Ryan L.; Siana, Brian; Coil, Alison L.; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H.; de Groot, Laura

    2015-03-01

    We present results on the excitation properties of z ˜ 2.3 galaxies using early observations from the MOSFIRE Deep Evolution Field (MOSDEF) Survey. With its coverage of the full suite of strong rest-frame optical emission lines, MOSDEF provides an unprecedented view of the rest-frame optical spectra of a representative sample of distant star-forming galaxies. We investigate the locations of z ˜ 2.3 MOSDEF galaxies in multiple emission-line diagnostic diagrams. These include the [O iii]λ5007/Hβ vs. [N ii]/Hα and [O iii]λ5007/Hβ vs. [S ii]λλ6717, 6731/Hα “BPT” diagrams, as well as the O32 vs. R23 excitation diagram. We recover the well-known offset in the star-forming sequence of high-redshift galaxies in the [O iii]λ5007/Hβ vs. [N ii]/Hα BPT diagram relative to Sloan Digital Sky Survey star-forming galaxies. However, the shift for our rest-frame optically selected sample is less significant than for rest-frame-UV selected and emission-line selected galaxies at z ˜ 2. Furthermore, we find that the offset is mass-dependent, only appearing within the low-mass half of the z ˜ 2.3 MOSDEF sample, where galaxies are shifted toward higher [N ii]/Hα at fixed [O iii]/Hβ. Within the [O iii]λ5007/Hβ vs. [S ii]/Hα and O32 vs. R23 diagrams, we find that z ˜ 2.3 galaxies are distributed like local ones, and therefore attribute the shift in the [O iii]λ5007/Hβ vs. [N ii]/Hα BPT diagram to elevated N/O abundance ratios among lower-mass ({{M}*}\\lt {{10}10} {{M}⊙ }) high-redshift galaxies. The variation in N/O ratios calls into question the use at high redshift of oxygen abundance indicators based on nitrogen lines, but the apparent invariance with redshift of the excitation sequence in the O32 vs. R23 diagram paves the way for using the combination of O32 and R23 as an unbiased metallicity indicator over a wide range in redshift. This indicator will allow for an accurate characterization of the shape and normalization of the mass

  4. The SCUBA-2 cosmology legacy survey: Ultraluminous star-forming galaxies in a z = 1.6 cluster

    SciTech Connect

    Smail, Ian; Swinbank, A. M.; Danielson, A. L. R.; Edge, A. C.; Simpson, J. M.; Geach, J. E.; Tadaki, K.; Arumugam, V.; Dunlop, J. S.; Ivison, R. J.; Hartley, W.; Almaini, O.; Conselice, C.; Bremer, M. N.; Chapin, E.; Chapman, S. C.; Scott, D.; Simpson, C. J.; Karim, A.; Kodama, T.; and others

    2014-02-10

    We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3–0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star-formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities ≳10{sup 12} L {sub ☉} and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit ALMA submillimeter continuum observations, which cover one of these sources, to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalized sense) than clusters at z ∼ 0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z = 1.6, M{sub H} ∼ –23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z ∼ 1.6 (M{sub H} ∼ –20.5 and M{sub H} ∼ –21.5, respectively, at z ∼ 0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z = 1.6 and that in Cl 0218.3–0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure.

  5. Charge-exchange X-ray emission of nearby star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Jiren; Wang, Q. Daniel; Mao, Shude

    2012-03-01

    Properties of hot gas outflows from galaxies are generally measured from associated X-ray line emission assuming that it represents atomic transitions in thermally excited hot gas. X-ray line emission, however, can also arise from the charge exchange between highly ionized ions and neutral species. The Kα triplet of He-like ions can be used as a powerful diagnostic, because the charge-exchange X-ray emission (CXE) favours the intercombination and forbidden lines, while the thermal emission favours the resonance line. We analyse the O VII triplet of a sample of nine nearby star-forming galaxies observed by the XMM-Newton Reflection Grating Spectrometers. For most galaxies, the forbidden lines are comparable to or stronger than the resonance lines, which is in contrast to the thermal prediction. For NGC 253, M51, M83, M61, NGC 4631, and the Antennae (Arp 244), the observed line ratios are consistent with the ratio of CXE; for M94 and NGC 2903, the observed ratios indicate multiple origins; for M82, different regions show different line ratios, also indicating multiple origins. We discuss other possible mechanisms that can produce a relatively strong forbidden line, such as a collisional non-equilibrium-ionization recombining/ionizing plasma, which are not favoured. These results suggest that the CXE may be a common phenomenon and contribute a significant fraction of the soft X-ray line emission for galaxies with massive star formation.

  6. DISSECTING THE STELLAR-MASS-SFR CORRELATION IN z = 1 STAR-FORMING DISK GALAXIES

    SciTech Connect

    Salmi, F.; Daddi, E.; Elbaz, D.; Sargent, M. T.; Bethermin, M.; Renzini, A.; Le Borgne, D. E-mail: edaddi@cea.fr

    2012-07-20

    Using a mass-limited sample of 24 {mu}m detected, star-forming galaxies at 0.5 < z < 1.3, we study the mass-star formation rate (SFR) correlation and its tightness. The correlation is well defined ({sigma} = 0.28 dex) for disk galaxies (n{sub Sersic} < 1.5), while more bulge-dominated objects often have lower specific SFRs (sSFRs). For disk galaxies, a much tighter correlation ({sigma} = 0.19 dex) is obtained if the rest-frame H-band luminosity is used instead of stellar mass derived from multi-color photometry. The sSFR correlates strongly with rest-frame optical colors (hence luminosity-weighted stellar age) and also with clumpiness (which likely reflects the molecular gas fraction). This implies that most of the observed scatter is real, despite its low level, and not dominated by random measurement errors. After correcting for these differential effects a remarkably small dispersion remains ({sigma} = 0.14 dex), suggesting that measurement errors in mass or SFR are {approx}< 0.10 dex, excluding systematic uncertainties. Measurement errors in stellar masses, the thickening of the correlation due to real sSFR variations, and varying completeness with stellar mass, can spuriously bias the derived slope to lower values due to the finite range over which observables (mass and SFR) are available. When accounting for these effects, the intrinsic slope for the main sequence for disk galaxies gets closer to unity.

  7. Luminosity Dependence and Redshift Evolution of Strong Emission-Line Diagnostics in Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Cowie, L. L.; Barger, A. J.; Songaila, A.

    2016-01-01

    We examine the redshift evolution of standard strong emission-line diagnostics for Hβ-selected star-forming galaxies using the local SDSS sample and a new z=0.2{--}2.3 sample obtained from Hubble Space Telescope WFC3 grism and Keck DEIMOS and MOSFIRE data. We use the SDSS galaxies to show that there is a systematic dependence of the strong emission-line properties on Balmer-line luminosity, which we interpret as showing that both the N/O abundance and the ionization parameter increase with increasing line luminosity. Allowing for the luminosity dependence tightens the diagnostic diagrams and the metallicity calibrations. The combined SDSS and high-redshift samples show that there is no redshift evolution in the line properties once the luminosity correction is applied, i.e., all galaxies with a given L({{H}}β ) have similar strong emission-line distributions at all the observed redshifts. We argue that the best metal diagnostic for the high-redshift galaxies may be a luminosity-adjusted version of the [N ii]6584/Hα metallicity relation. Based in part 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. SPITZER IMAGING OF STRONGLY LENSED HERSCHEL-SELECTED DUSTY STAR-FORMING GALAXIES

    SciTech Connect

    Ma, Brian; Cooray, Asantha; Calanog, J. A.; Nayyeri, H.; Timmons, N.; Casey, C.; Baes, M.; Chapman, S.; Dannerbauer, H.; De Zotti, G.; Dunne, L.; Michałowski, M. J.; Oteo, I.; Farrah, D.; Fu, Hai; Gonzalez-Nuevo, J.; Riechers, D. A.; Scott, D.; and others

    2015-11-20

    We present the rest-frame optical spectral energy distribution (SED) and stellar masses of six Herschel-selected gravitationally lensed dusty, star-forming galaxies (DSFGs) at 1 < z < 3. These galaxies were first identified with Herschel/SPIRE imaging data from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). The targets were observed with Spitzer/IRAC at 3.6 and 4.5 μm. Due to the spatial resolution of the IRAC observations at the level of 2″, the lensing features of a background DSFG in the near-infrared are blended with the flux from the foreground lensing galaxy in the IRAC imaging data. We make use of higher resolution Hubble/WFC3 or Keck/NIRC2 Adaptive Optics imaging data to fit light profiles of the foreground lensing galaxy (or galaxies) as a way to model the foreground components, in order to successfully disentangle the foreground lens and background source flux densities in the IRAC images. The flux density measurements at 3.6 and 4.5 μm, once combined with Hubble/WFC3 and Keck/NIRC2 data, provide important constraints on the rest-frame optical SED of the Herschel-selected lensed DSFGs. We model the combined UV- to millimeter-wavelength SEDs to establish the stellar mass, dust mass, star formation rate, visual extinction, and other parameters for each of these Herschel-selected DSFGs. These systems have inferred stellar masses in the range 8 × 10{sup 10}–4 × 10{sup 11} M{sub ⊙} and star formation rates of around 100 M{sub ⊙} yr{sup −1}. This puts these lensed submillimeter systems well above the SFR-M* relation observed for normal star-forming galaxies at similar redshifts. The high values of SFR inferred for these systems are consistent with a major merger-driven scenario for star formation.

  9. OUTSIDE-IN SHRINKING OF THE STAR-FORMING DISK OF DWARF IRREGULAR GALAXIES

    SciTech Connect

    Zhang Hongxin; Hunter, Deidre A.; Elmegreen, Bruce G.; Gao Yu; Schruba, Andreas E-mail: dah@lowell.edu E-mail: bge@us.ibm.com

    2012-02-15

    We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies. Our data include Galaxy Evolution Explorer (GALEX) FUV/NUV, UBV, and H{alpha} and Spitzer 3.6 {mu}m images. These galaxies constitute the majority of the LITTLE THINGS survey (Local Irregulars That Trace Luminosity Extremes-The H I Nearby Galaxy Survey). By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation histories, we derived the stellar mass surface density distributions and the star formation rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr, and a Hubble time. We find that, for {approx}80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths, corresponding to younger stellar populations, have shorter disk scale lengths than those at longer wavelengths, corresponding to older stellar populations. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and {approx}80% of the galaxies have steeper mass profiles in the outer disk than in the inner region. The steep radial decline of the star formation rate in the outer parts compared to that in the inner disks gives a natural explanation for the down-bending stellar mass surface density profiles. Within the inner disks, our sample galaxies on average have constant ratios of recent star formation rate to stellar mass with radius. Nevertheless, {approx}35% (12 galaxies, among which 7 have baryonic mass {approx}<10{sup 8} M{sub Sun} ) of the sample exhibit negative slopes across the observed disk, which is in contrast with the so-called inside-out disk growth scenario suggested for luminous spiral galaxies. The tendency of star formation to become concentrated toward the inner disks in low-mass dwarf irregular galaxies is

  10. Outside-in Shrinking of the Star-forming Disk of Dwarf Irregular Galaxies

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Xin; Hunter, Deidre A.; Elmegreen, Bruce G.; Gao, Yu; Schruba, Andreas

    2012-02-01

    We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies. Our data include Galaxy Evolution Explorer (GALEX) FUV/NUV, UBV, and Hα and Spitzer 3.6 μm images. These galaxies constitute the majority of the LITTLE THINGS survey (Local Irregulars That Trace Luminosity Extremes—The H I Nearby Galaxy Survey). By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation histories, we derived the stellar mass surface density distributions and the star formation rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr, and a Hubble time. We find that, for ~80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths, corresponding to younger stellar populations, have shorter disk scale lengths than those at longer wavelengths, corresponding to older stellar populations. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and ~80% of the galaxies have steeper mass profiles in the outer disk than in the inner region. The steep radial decline of the star formation rate in the outer parts compared to that in the inner disks gives a natural explanation for the down-bending stellar mass surface density profiles. Within the inner disks, our sample galaxies on average have constant ratios of recent star formation rate to stellar mass with radius. Nevertheless, ~35% (12 galaxies, among which 7 have baryonic mass lsim108 M ⊙) of the sample exhibit negative slopes across the observed disk, which is in contrast with the so-called inside-out disk growth scenario suggested for luminous spiral galaxies. The tendency of star formation to become concentrated toward the inner disks in low-mass dwarf irregular galaxies is interpreted as a result of their susceptibility to

  11. Lyman Continuum Escape Fraction of Star-forming Dwarf Galaxies at z ˜ 1

    NASA Astrophysics Data System (ADS)

    Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian; Henry, Alaina; Rafelski, Marc; Hayes, Matthew; Salvato, Mara; Pahl, Anthony J.; Mehta, Vihang; Beck, Melanie; Malkan, Matthew; Teplitz, Harry I.

    2016-03-01

    To date, no direct detection of Lyman continuum emission has been measured for intermediate-redshift (z˜ 1) star-forming galaxies. We combine Hubble Space Telescope grism spectroscopy with GALEX UV and ground-based optical imaging to extend the search for escaping Lyman continuum to a large (˜600) sample of z˜ 1 low-mass ({log}(\\bar{M}) ≃ 9.3{M}⊙ ), moderately star-forming (\\bar{{{\\Psi }}} ≲ 10{M}⊙ yr-1) galaxies selected initially on Hα emission. The characteristic escape fraction of LyC from star-forming galaxies (SFGs) that populate this parameter space remains weakly constrained by previous surveys, but these faint (sub-L⋆) SFGs are assumed to play a significant role in the reionization of neutral hydrogen in the intergalactic medium (IGM) at high redshift z\\gt 6. We do not make an unambiguous detection of escaping LyC radiation from this z˜ 1 sample, individual non-detections to constrain the absolute Lyman continuum escape fraction, {f}{esc} \\lt 2.1% (3σ). We measure an upper limit of {f}{esc} \\lt 9.6% from a sample of SFGs selected on high Hα equivalent width (EW \\gt 200 {{\\mathringA }}), which are thought to be close analogs of high redshift sources of reionization. For reference, we also present an emissivity-weighted escape fraction that is useful for measuring the general contribution SFGs to the ionizing UV background. In the discussion, we consider the implications of these intermediate redshift constraints for the reionization of hydrogen in the IGM at high (z\\gt 6) redshift. If we assume our z˜ 1 SFGs, for which we measure this emissivity-weighted {f}{esc}, are analogs to the high redshift sources of reionization, we find it is difficult to reconcile reionization by faint ({M}{UV}≲ -13) SFGs with a low escape fraction ({f}{esc} \\lt 3%), with constraints from independent high redshift observations. If {f}{esc} evolves with redshift, reionization by SFGs may be consistent with observations from Planck.

  12. Modelling the nebular emission from primeval to present-day star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Gutkin, Julia; Charlot, Stéphane; Bruzual, Gustavo

    2016-10-01

    We present a new model of the nebular emission from star-forming galaxies in a wide range of chemical compositions, appropriate to interpret observations of galaxies at all cosmic epochs. The model relies on the combination of state-of-the-art stellar population synthesis and photoionization codes to describe the ensemble of H II regions and the diffuse gas ionized by young stars in a galaxy. A main feature of this model is the self-consistent yet versatile treatment of element abundances and depletion on to dust grains, which allows one to relate the observed nebular emission from a galaxy to both gas-phase and dust-phase metal enrichment. We show that this model can account for the rest-frame ultraviolet and optical emission-line properties of galaxies at different redshifts and find that ultraviolet emission lines are more sensitive than optical ones to parameters such as C/O abundance ratio, hydrogen gas density, dust-to-metal mass ratio and upper cut-off of the stellar initial mass function. We also find that, for gas-phase metallicities around solar to slightly subsolar, widely used formulae to constrain oxygen ionic fractions and the C/O ratio from ultraviolet and optical emission-line luminosities are reasonable faithful. However, the recipes break down at non-solar metallicities, making them inappropriate to study chemically young galaxies. In such cases, a fully self-consistent model of the kind presented in this paper is required to interpret the observed nebular emission.

  13. On the formation redshift of Low-Mass Star-Forming Galaxies at intermediate redshifts

    NASA Astrophysics Data System (ADS)

    Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Barro, Guillermo; Gomez-Guijarro, Carlos; Villar, Víctor

    2015-08-01

    Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that low-mass systems merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf systems might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of low-mass systems at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of low-mass dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present constraints on the star formation histories (SFHs) of a sample of low-mass Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFHs were obtained through the analysis of their spectral energy distributions using a novel approach (Pacifici et al. 2012) that (1) consistently combines photometric (HST and ground-based multi-broadband) and spectroscopic (equivalent widths of emission lines from VLT and GTC spectroscopy) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time.The median SFH of our LMSFGs appears to form 90% of the median stellar mass inferred for the sample in the ˜0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for dwarf SFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for a slightly more massive secondary sample 8.0 < log M∗/Mo < 9.1).This is a pilot study for future surveys on dwarf galaxies at high redshift.

  14. EXTINCTION IN STAR-FORMING DISK GALAXIES FROM INCLINATION-DEPENDENT COMPOSITE SPECTRA

    SciTech Connect

    Yip, Ching-Wa; Szalay, Alex S.; Wyse, Rosemary F. G.; Budavari, Tamas; Dobos, Laszlo; Csabai, Istvan E-mail: szalay@pha.jhu.ed

    2010-02-01

    Extinction in galaxies affects their observed properties. In scenarios describing the distribution of dust and stars in individual disk galaxies, the amplitude of the extinction can be modulated by the inclination of the galaxies. In this work, we investigate the inclination dependency in composite spectra of star-forming disk galaxies from the Sloan Digital Sky Survey Data Release 5. In a volume-limited sample within a redshift range 0.065-0.075 and a r-band Petrosian absolute magnitude range -19.5 to -22 mag which exhibits a flat distribution of inclination, the inclined relative to face-on extinction in the stellar continuum is found empirically to increase with inclination in the g, r, and i bands. Within the central 0.5 intrinsic half-light radius of the galaxies, the g-band relative extinction in the stellar continuum for the highly inclined objects (axis ratio b/a = 0.1) is 1.2 mag, agreeing with previous studies. The extinction curve of the disk galaxies is given in the rest-frame wavelengths 3700-8000 A, identified with major optical emission and absorption lines in diagnostics. The Balmer decrement, Halpha/Hbeta, remains constant with inclination, suggesting a different kind of dust configuration and/or reddening mechanism in the H II region from that in the stellar continuum. One factor is shown to be the presence of spatially non-uniform interstellar extinction, presumably caused by clumped dust in the vicinity of the H II region.

  15. Structure and dynamics of star-forming galaxies across the history of the Universe using GRBs

    NASA Astrophysics Data System (ADS)

    Thöne, Christina; Fynbo, Johan; de Ugarte Postigo, Antonio

    2015-08-01

    Gamma-ray bursts are exploding massive stars and some of the most luminous explosions in the Universe. They can serve as powerful light houses that probe the structure and abundances of the dense ISM in their hosts at almost any redshift and not accessible by other types of observations, e.g. using quasars. Since 2009 our collaboration has collected UV to nIR medium-resolution spectra of over 70 GRB afterglows using the ESO/VLT X-shooter spectrograph. Our sample covers a redshift range from 0.06 to 6.3 allowing us to study the dynamics of the ISM in star-forming galaxies from the nearby Universe out to the epoch of reionization and for the first time in a statistically sound way. Absorption lines usually show a rich structure of different components due to galaxy dynamics, turbulences or in-/outflows and different ionization levels seem to arise from different regions in the host. Fine-structure lines some of which are uniquely observed in GRB hosts are excited in the dense regions close to the GRB site itself. For some host with z < 3 we can also simultaenously observe emission lines from the hot ISM, comparing the origin of hot and cold gas within the same galaxy. The large wavelength coverage of the sample gives us the unique opportunity to study the evolution of gas dynamics across most of the time galaxies have existed, how the gas structure changed over time and what is the importance and consistency of in- and ouflows. Here we will present the X-shooter GRB afterglow sample, our results on the study of absorption and emission line features and compare the observed structures with theoretical models of galaxies to get a unique insight on the distrubution and dynamics of the ISM in starforming galaxies at any redshift.

  16. Hubble Imaging of the Ionizing Radiation from a Star-forming Galaxy at Z=3.2 with fesc>50%

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; de Barros, S.; Vasei, K.; Alavi, A.; Giavalisco, M.; Siana, B.; Grazian, A.; Hasinger, G.; Suh, H.; Cappelluti, N.; Vito, F.; Amorin, R.; Balestra, I.; Brusa, M.; Calura, F.; Castellano, M.; Comastri, A.; Fontana, A.; Gilli, R.; Mignoli, M.; Pentericci, L.; Vignali, C.; Zamorani, G.

    2016-07-01

    Star-forming galaxies are considered to be the leading candidate sources dominating cosmic reionization at z\\gt 7: the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently an active line of research. We have observed a star-forming galaxy at z = 3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730-890 Å rest-frame, and detected LyC emission. This galaxy is very compact and also has a large Oxygen ratio [{{O}} {{III}}]λ 5007/[{{O}} {{II}}]λ 3727 (≳ 10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6 Ms X-ray Chandra observations). The measured escape fraction of ionizing radiation spans the range 50%-100%, depending on the intergalactic medium (IGM) attenuation. The LyC emission is measured at {m}{{F}336{{W}}}=27.57+/- 0.11 (with signal-to-noise ratio (S/N) = 10) and is spatially unresolved, with an effective radius of {R}e\\lt 200 pc. Predictions from photoionization and radiative transfer models are in line with the properties reported here, indicating that stellar winds and supernova explosions in a nucleated star-forming region can blow cavities generating density-bounded conditions compatible to optically thin media. Irrespective of the nature of the ionizing radiation, spectral signatures of these sources over the entire electromagnetic spectrum are of central importance for their identification during the epoch of reionization when the LyC is unobservable. Intriguingly, the Spitzer/IRAC photometric signature of intense rest-frame optical emissions ([O iii]λλ4959,5007 + Hβ) recently observed at z≃ 7.5{--}8.5 is similar to what is observed in this galaxy. Only the James Webb Space Telescope will measure optical line ratios at z\\gt 7, allowing a direct comparison with the lower-redshift LyC emitters, such as that reported here. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope

  17. Hubble Imaging of the Ionizing Radiation from a Star-forming Galaxy at Z=3.2 with fesc>50%

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; de Barros, S.; Vasei, K.; Alavi, A.; Giavalisco, M.; Siana, B.; Grazian, A.; Hasinger, G.; Suh, H.; Cappelluti, N.; Vito, F.; Amorin, R.; Balestra, I.; Brusa, M.; Calura, F.; Castellano, M.; Comastri, A.; Fontana, A.; Gilli, R.; Mignoli, M.; Pentericci, L.; Vignali, C.; Zamorani, G.

    2016-07-01

    Star-forming galaxies are considered to be the leading candidate sources dominating cosmic reionization at z\\gt 7: the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently an active line of research. We have observed a star-forming galaxy at z = 3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730–890 Å rest-frame, and detected LyC emission. This galaxy is very compact and also has a large Oxygen ratio [{{O}} {{III}}]λ 5007/[{{O}} {{II}}]λ 3727 (≳ 10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6 Ms X-ray Chandra observations). The measured escape fraction of ionizing radiation spans the range 50%–100%, depending on the intergalactic medium (IGM) attenuation. The LyC emission is measured at {m}{{F}336{{W}}}=27.57+/- 0.11 (with signal-to-noise ratio (S/N) = 10) and is spatially unresolved, with an effective radius of {R}e\\lt 200 pc. Predictions from photoionization and radiative transfer models are in line with the properties reported here, indicating that stellar winds and supernova explosions in a nucleated star-forming region can blow cavities generating density-bounded conditions compatible to optically thin media. Irrespective of the nature of the ionizing radiation, spectral signatures of these sources over the entire electromagnetic spectrum are of central importance for their identification during the epoch of reionization when the LyC is unobservable. Intriguingly, the Spitzer/IRAC photometric signature of intense rest-frame optical emissions ([O iii]λλ4959,5007 + Hβ) recently observed at z≃ 7.5{--}8.5 is similar to what is observed in this galaxy. Only the James Webb Space Telescope will measure optical line ratios at z\\gt 7, allowing a direct comparison with the lower-redshift LyC emitters, such as that reported here. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space

  18. Star-forming galaxies as the origin of diffuse high-energy backgrounds: gamma-ray and neutrino connections, and implications for starburst history

    SciTech Connect

    Tamborra, Irene; Ando, Shin'ichiro; Murase, Kohta E-mail: s.ando@uva.nl

    2014-09-01

    Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos and that O(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1–2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E{sup -2.15} are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.

  19. Dynamical Properties of z ~ 2 Star-forming Galaxies and a Universal Star Formation Relation

    NASA Astrophysics Data System (ADS)

    Bouché, N.; Cresci, G.; Davies, R.; Eisenhauer, F.; Förster Schreiber, N. M.; Genzel, R.; Gillessen, S.; Lehnert, M.; Lutz, D.; Nesvadba, N.; Shapiro, K. L.; Sternberg, A.; Tacconi, L. J.; Verma, A.; Cimatti, A.; Daddi, E.; Renzini, A.; Erb, D. K.; Shapley, A.; Steidel, C. C.

    2007-12-01

    We present the first comparison of the dynamical properties of different samples of z~1.4-3.4 star-forming galaxies from spatially resolved imaging spectroscopy from SINFONI/VLT integral field spectroscopy and IRAM CO millimeter interferometry. Our samples include 16 rest-frame UV-selected, 16 rest-frame optically selected, and 13 submillimeter galaxies (SMGs). We find that rest-frame UV and optically bright (K<20) z~2 star forming galaxies are dynamically similar, and follow the same velocity-size relation as disk galaxies at z~0. In the theoretical framework of rotating disks forming from dissipative collapse in dark matter halos, the two samples require a spin parameter <λ> ranging from 0.06 to 0.2. In contrast, bright SMGs (S850μm>=5 mJy) have larger velocity widths and are much more compact. Hence, SMGs have lower angular momenta and higher matter densities than either the UV or optically selected populations. This indicates that dissipative major mergers may dominate the SMGs population, resulting in early spheroids, and that a significant fraction of the UV/optically bright galaxies have evolved less violently, either in a series of minor mergers, or in rapid dissipative collapse from the halo, given that either process may leads to the formation of early disks. These early disks may later evolve into spheroids via disk instabilities or mergers. Because of their small sizes and large densities, SMGs lie at the high surface density end of a universal (out to z=2.5) ``Schmidt-Kennicutt'' relation between gas surface density and star formation rate surface density. The best-fit relation suggests that the star formation rate per unit area scales as the surface gas density to a power of ~1.7, and that the star formation efficiency increases by a factor of 4 between non-starbursts and strong starbursts. Based on observations at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile, under programs GTO 073.B-9018, 074.A-9011

  20. Feedback from quasars in star-forming galaxies and the triggering of massive galactic winds

    NASA Astrophysics Data System (ADS)

    Monaco, Pierluigi; Fontanot, Fabio

    2005-05-01

    The shining of quasars is a likely trigger of massive galactic winds, able to remove most interstellar medium (ISM) from a star-forming spheroid. However, the mechanism responsible for the deposition of energy into the ISM is still unclear. Starting from a model for feedback in galaxy formation with a two-phase medium (Monaco), we propose that the perturbation induced by radiative heating from a quasar on the ISM triggers a critical change of feedback regime. In the feedback model, supernova remnants (SNRs) expanding in the hot and pressurized phase of a star-forming spheroid typically become pressure confined before the hot interior gas is able to cool. In the presence of runaway radiative heating by a quasar, a mass flow from the cold to the hot phase develops; whenever this evaporation flow is significant with respect to the star formation rate, owing to the increased density of the hot phase the SNRs reach the point where their interior gas cools before being confined, forming a thick cold shell. We show that in this case the consequent drop in pressure leads quickly to the percolation of all the shells and to the formation of a super shell of cold gas that sweeps the whole galaxy. Radiation pressure is then very effective in removing such a shell from the galaxy. This self-limiting mechanism leads to a correlation between black hole and bulge masses for more massive bulges than 1010 Msolar. The insertion of a motivated wind trigger criterion in a hierarchical galaxy formation model shows, however, that winds are not necessary to obtain a good black hole-bulge correlation. In the absence of winds, good results are obtained if the mechanism responsible for the creation of a reservoir of low-angular momentum gas (able to accrete on to the black hole) deposits mass at a rate proportional to the star formation rate. Using a novel galaxy formation model, we show under which conditions black hole masses are self-limited by the wind mechanism described above, and

  1. The Spatial Distribution of the Young Stellar Clusters in the Star-forming Galaxy NGC 628

    NASA Astrophysics Data System (ADS)

    Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Aloisi, A.; Bright, S. N.; Christian, C.; Cignoni, M.; Dale, D. A.; Dobbs, C.; Elmegreen, D. M.; Fumagalli, M.; Gallagher, J. S., III; Grebel, E. K.; Johnson, K. E.; Lee, J. C.; Messa, M.; Smith, L. J.; Ryon, J. E.; Thilker, D.; Ubeda, L.; Wofford, A.

    2015-12-01

    We present a study of the spatial distribution of the stellar cluster populations in the star-forming galaxy NGC 628. Using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey), we have identified 1392 potential young (≲ 100 Myr) stellar clusters within the galaxy using a combination of visual inspection and automatic selection. We investigate the clustering of these young stellar clusters and quantify the strength and change of clustering strength with scale using the two-point correlation function. We also investigate how image boundary conditions and dust lanes affect the observed clustering. The distribution of the clusters is well fit by a broken power law with negative exponent α. We recover a weighted mean index of α ∼ -0.8 for all spatial scales below the break at 3.″3 (158 pc at a distance of 9.9 Mpc) and an index of α ∼ -0.18 above 158 pc for the accumulation of all cluster types. The strength of the clustering increases with decreasing age and clusters older than 40 Myr lose their clustered structure very rapidly and tend to be randomly distributed in this galaxy, whereas the mass of the star cluster has little effect on the clustering strength. This is consistent with results from other studies that the morphological hierarchy in stellar clustering resembles the same hierarchy as the turbulent interstellar medium.

  2. On the Contribution of Fluorescence to Lyα Halos around Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Mas-Ribas, Lluís; Dijkstra, Mark

    2016-05-01

    We quantify the contribution of Lyα fluorescence to observed spatially extended Lyα halos around Lyα emitters at redshift z = 3.1. The key physical quantities that describe the fluorescent signal include (i) the distribution of cold gas in the circumgalactic medium (CGM); we explore simple analytic models and fitting functions to recent hydrodynamical simulations; and (ii) local variations in the ionizing background due to ionizing sources that cluster around the central galaxy. We account for clustering by boosting the observationally inferred volumetric production rate of ionizing photons, {ɛ }{{LyC}}, by a factor of 1+{ξ }{{LyC}}(r), in which {ξ }{{LyC}}(r) quantifies the clustering of ionizing sources around the central galaxy. We compute {ξ }{{LyC}}(r) by assigning an “effective” bias parameter to the ionizing sources. This novel approach allows us to quantify our ignorance of the population of ionizing sources in a simple parametrized form. We find a maximum enhancement in the local ionizing background in the range 50–200 at r ˜ 10 physical kpc. For spatially uncorrelated ionizing sources and fluorescing clouds we find that fluorescence can contribute up to ˜ 50%–60% of the observed spatially extended Lyα emission. We briefly discuss how future observations can shed light on the nature of Lyα halos around star-forming galaxies.

  3. On the Contribution of Fluorescence to Lyα Halos around Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Mas-Ribas, Lluís; Dijkstra, Mark

    2016-05-01

    We quantify the contribution of Lyα fluorescence to observed spatially extended Lyα halos around Lyα emitters at redshift z = 3.1. The key physical quantities that describe the fluorescent signal include (i) the distribution of cold gas in the circumgalactic medium (CGM); we explore simple analytic models and fitting functions to recent hydrodynamical simulations; and (ii) local variations in the ionizing background due to ionizing sources that cluster around the central galaxy. We account for clustering by boosting the observationally inferred volumetric production rate of ionizing photons, {ɛ }{{LyC}}, by a factor of 1+{ξ }{{LyC}}(r), in which {ξ }{{LyC}}(r) quantifies the clustering of ionizing sources around the central galaxy. We compute {ξ }{{LyC}}(r) by assigning an “effective” bias parameter to the ionizing sources. This novel approach allows us to quantify our ignorance of the population of ionizing sources in a simple parametrized form. We find a maximum enhancement in the local ionizing background in the range 50-200 at r ˜ 10 physical kpc. For spatially uncorrelated ionizing sources and fluorescing clouds we find that fluorescence can contribute up to ˜ 50%-60% of the observed spatially extended Lyα emission. We briefly discuss how future observations can shed light on the nature of Lyα halos around star-forming galaxies.

  4. THE STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF STAR-FORMING GALAXIES IN THE NEARBY UNIVERSE

    SciTech Connect

    Torres-Papaqui, J. P.; Coziol, R.; Ortega-Minakata, R. A.; Neri-Larios, D. M. E-mail: rcoziol@astro.ugto.mx E-mail: daniel@astro.ugto.mx

    2012-08-01

    We have determined the metallicity (O/H) and nitrogen abundance (N/O) of a sample of 122,751 star-forming galaxies (SFGs) from the Data Release 7 of the Sloan Digital Sky Survey. For all these galaxies we have also determined their morphology and obtained a comprehensive picture of their star formation history (SFH) using the spectral synthesis code STARLIGHT. The comparison of the chemical abundance with the SFH allows us to describe the chemical evolution of the SFGs in the nearby universe (z {<=} 0.25) in a manner consistent with the formation of their stellar populations and morphologies. A high fraction (45%) of the SFGs in our sample show an excess abundance of nitrogen relative to their metallicity. We also find this excess to be accompanied by a deficiency of oxygen, which suggests that this could be the result of effective starburst winds. However, we find no difference in the mode of star formation of the nitrogen-rich and nitrogen-poor SFGs. Our analysis suggests that they all form their stars through a succession of bursts of star formation extended over a period of few Gyr. What produces the chemical differences between these galaxies seems therefore to be the intensity of the bursts: the galaxies with an excess of nitrogen are those that are presently experiencing more intense bursts or have experienced more intense bursts in their past. We also find evidence relating the chemical evolution process to the formation of the galaxies: the galaxies with an excess of nitrogen are more massive, and have more massive bulges and earlier morphologies than those showing no excess. Contrary to expectation, we find no evidence that the starburst wind efficiency decreases with the mass of the galaxies. As a possible explanation we propose that the loss of metals consistent with starburst winds took place during the formation of the galaxies, when their potential wells were still building up, and consequently were weaker than today, making starburst winds more

  5. Complex Gas Kinematics in Compact, Rapidly Assembling Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Amorín, R.; Vílchez, J. M.; Hägele, G. F.; Firpo, V.; Pérez-Montero, E.; Papaderos, P.

    2012-08-01

    Deep, high-resolution spectroscopic observations have been obtained for six compact, strongly star-forming galaxies at redshift z ~ 0.1-0.3, most of them also known as green peas. Remarkably, these galaxies show complex emission-line profiles in the spectral region including Hα, [N II] λλ6548, 6584, and [S II] λλ6717, 6731, consisting of the superposition of different kinematical components on a spatial extent of few kiloparsecs: a very broad line emission underlying more than one narrower component. For at least two of the observed galaxies some of these multiple components are resolved spatially in their two-dimensional spectra, whereas for another one a faint detached Hα blob lacking stellar continuum is detected at the same recessional velocity ~7 kpc away from the galaxy. The individual narrower Hα components show high intrinsic velocity dispersion (σ ~ 30-80 km s-1), suggesting together with unsharped masking Hubble Space Telescope images that star formation proceeds in an ensemble of several compact and turbulent clumps, with relative velocities of up to ~500 km s-1. The broad underlying Hα components indicate in all cases large expansion velocities (full width zero intensity >=1000 km s-1) and very high luminosities (up to ~1042 erg s-1), probably showing the imprint of energetic outflows from supernovae. These intriguing results underline the importance of green peas for studying the assembly of low-mass galaxies near and far. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  6. Age-dating Low-Mass Star-Forming Galaxies at intermediate redshifts

    NASA Astrophysics Data System (ADS)

    Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Barro, Guillermo; Gomez-Guijarro, Carlos; Villar, Víctor

    2015-08-01

    Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that low-mass systems merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf systems might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of low-mass systems at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of low-mass dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present physical properties and constraints on the star formation histories (SFHs) of a sample of low-mass Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFHs were obtained through the analysis of their spectral energy distributions using a novel approach (Pacifici et al. 2012) that (1) consistently combines photometric (HST and ground-based multi-broadband) and spectroscopic (equivalent widths of emission lines from VLT and GTC spectroscopy) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time.The median SFH of our LMSFGs appears to form 90% of the median stellar mass inferred for the sample in the ˜0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for dwarf SFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for a slightly more massive secondary sample 8.0 < log M∗/Mo < 9.1).

  7. PREDICTIONS FOR ULTRA-DEEP RADIO COUNTS OF STAR-FORMING GALAXIES

    SciTech Connect

    Mancuso, Claudia; Lapi, Andrea; De Zotti, Gianfranco; Bressan, Alessandro; Perrotta, Francesca; Danese, Luigi; Cai, Zhen-Yi; Negrello, Mattia; Bonato, Matteo

    2015-09-01

    We have worked outty predictions for the radio counts of star-forming galaxies down to nJy levels, along with redshift distributions down to the detection limits of the phase 1 Square Kilometer Array MID telescope (SKA1-MID) and of its precursors. Such predictions were obtained by coupling epoch-dependent star formation rate (SFR) functions with relations between SFR and radio (synchrotron and free–free) emission. The SFR functions were derived taking into account both the dust-obscured and the unobscured star formation, by combining far-infrared, ultraviolet, and Hα luminosity functions up to high redshifts. We have also revisited the South Pole Telescope counts of dusty galaxies at 95 GHz, performing a detailed analysis of the Spectral Energy Distributions. Our results show that the deepest SKA1-MID surveys will detect high-z galaxies with SFRs two orders of magnitude lower compared to Herschel surveys. The highest redshift tails of the distributions at the detection limits of planned SKA1-MID surveys comprise a substantial fraction of strongly lensed galaxies. We predict that a survey down to 0.25 μJy at 1.4 GHz will detect about 1200 strongly lensed galaxies per square degree, at redshifts of up to 10. For about 30% of them the SKA1-MID will detect at least 2 images. The SKA1-MID will thus provide a comprehensive view of the star formation history throughout the re-ionization epoch, unaffected by dust extinction. We have also provided specific predictions for the EMU/ASKAP and MIGHTEE/MeerKAT surveys.

  8. The Quest for Dusty Star-forming Galaxies at High Redshift z ≳ 4

    NASA Astrophysics Data System (ADS)

    Mancuso, C.; Lapi, A.; Shi, J.; Gonzalez-Nuevo, J.; Aversa, R.; Danese, L.

    2016-06-01

    We exploit the continuity equation approach and “main-sequence” star formation timescales to show that the observed high abundance of galaxies with stellar masses ≳ a few 1010 M ⊙ at redshift z ≳ 4 implies the existence of a galaxy population featuring large star formation rates (SFRs) ψ ≳ 102 M ⊙ yr-1 in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z ≲ 3 in the far-IR band by the Herschel Space Observatory. We work out specific predictions for the evolution of the corresponding stellar mass and SFR functions out to z ˜ 10, determining that the number density at z ≲ 8 for SFRs ψ ≳ 30 M ⊙ yr-1 cannot be estimated relying on the UV luminosity function alone, even when standard corrections for dust extinction based on the UV slope are applied. We compute the number counts and redshift distributions (including galaxy-scale gravitational lensing) of this galaxy population, and show that current data from the AzTEC-LABOCA, SCUBA-2, and ALMA-SPT surveys are already addressing it. We demonstrate how an observational strategy based on color preselection in the far-IR or (sub-)millimeter band with Herschel and SCUBA-2, supplemented by photometric data from on-source observations with ALMA, can allow us to reconstruct the bright end of the SFR functions out to z ≲ 8. In parallel, such a challenging task can be managed by exploiting current UV surveys in combination with (sub-)millimeter observations by ALMA and NIKA2 and/or radio observations by SKA and its precursors.

  9. DISSECTION OF H{alpha} EMITTERS : LOW-z ANALOGS OF z > 4 STAR-FORMING GALAXIES

    SciTech Connect

    Shim, Hyunjin; Chary, Ranga-Ram

    2013-03-01

    Strong H{alpha} emitters (HAEs) dominate the z {approx} 4 Lyman-break galaxy (LBG) population. We have identified local analogs of these HAEs using the Sloan Digital Sky Survey. At z < 0.4, only 0.04% of the galaxies are classified as HAEs with H{alpha} equivalent widths ({approx}> 500 A) comparable to that of z {approx} 4 HAEs. Local HAEs have lower stellar mass and lower ultraviolet (UV) luminosity than z {approx} 4 HAEs, yet the H{alpha}-to-UV luminosity ratio, as well as their specific star formation rate, is consistent with that of z {approx} 4 HAEs, indicating that they are scaled-down versions of high-z star-forming galaxies. Compared to the previously studied local analogs of LBGs selected using rest-frame UV properties, local HAEs show similar UV luminosity surface density, weaker D{sub n} (4000) break, lower metallicity, and lower stellar mass. This implies that the local HAEs are less evolved galaxies than the traditional Lyman break analogs. In the stacked spectrum, local HAEs show a significant He II {lambda}4686 emission line suggesting a population of hot, massive stars similar to that seen in some Wolf-Rayet galaxies. Low [N II]/[O III] line flux ratios imply that local HAEs are inconsistent with being systems that host bright active galactic nuclei. Instead, it is highly likely that local HAEs are galaxies with an elevated ionization parameter, either due to a high electron density or large escape fraction of hydrogen ionizing photons as in the case of Wolf-Rayet galaxies.

  10. Kinematics in the Interacting, Star-Forming Galaxies NGC 3395/3396 and NGC 3991/3994/3995

    NASA Technical Reports Server (NTRS)

    Weistrop, Donna; Nelson, Charles H.

    1999-01-01

    It has been suggested that induced star formation is more sensitive to galaxy dynamics than to local phenomena and that enhanced star formation is found in galaxies with disturbed velocity structures. We are studying the stellar populations of several UV-bright, interacting galaxies to try to understand the detailed star formation process in these systems. We present preliminary results of an investigation of the kinematics of star-forming regions in the interacting systems NGC 3395/3396 and NGC 3991/3994/3995. Regions of powerful star formation are observed throughout these galaxies. The observatation will be used to investigate rotation curves in the galaxies and motion in the tidal tails.

  11. GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4

    SciTech Connect

    Pannella, M.; Elbaz, D.; Daddi, E.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Cibinel, A.; Juneau, S.; Floc’h, E. Le; Leiton, R.; Buat, V.; Charmandaris, V.; Magdis, G.; Ivison, R. J.; Borgne, D. Le; Lin, L.; Morrison, G. E.; and others

    2015-07-10

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate–M{sub *} correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR–radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5–4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts.

  12. High Mass X-ray Binaries in Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Rangelov, Blagoy

    High Mass X-ray Binaries (HMXBs), in which a compact object, either black hole or neutron star, is accreting material from a young, massive donor star, often dominate the high-energy emission from nearby star-forming galaxies. These high mass pairs are believed to form in star clusters, where most massive star formation takes place, but to become displaced from their parent clusters either because they are dynamically ejected or because their parent cluster has dissolved. We have conducted a systematic study of the formation and evolution of bright HMXBs in eight nearby galaxies, by detecting HMXBs from their X-ray emission in Chandra X-ray Observatory observations, and identifying their parent clusters and donor stars in optical observations taken with the Hubble Space Telescope. We use the X-ray and optical properties of these systems to determine the ages of the binaries, whether the compact objects are black holes or neutron stars, and to constrain the masses of the donor stars.

  13. Extremely Bright Submillimeter Galaxies beyond the Lupus-I Star-forming Region

    NASA Astrophysics Data System (ADS)

    Tamura, Y.; Kawabe, R.; Shimajiri, Y.; Tsukagoshi, T.; Nakajima, Y.; Oasa, Y.; Wilner, D. J.; Chandler, C. J.; Saigo, K.; Tomida, K.; Yun, M. S.; Taniguchi, A.; Kohno, K.; Hatsukade, B.; Aretxaga, I.; Austermann, J. E.; Dickman, R.; Ezawa, H.; Goss, W. M.; Hayashi, M.; Hughes, D. H.; Hiramatsu, M.; Inutsuka, S.; Ogasawara, R.; Ohashi, N.; Oshima, T.; Scott, K. S.; Wilson, G. W.

    2015-08-01

    We report detections of two candidate distant submillimeter galaxies (SMGs), MM J154506.4-344318 and MM J154132.7-350320, which are discovered in the AzTEC/ASTE 1.1 mm survey toward the Lupus-I star-forming region. The two objects have 1.1 mm flux densities of 43.9 and 27.1 mJy, and have Herschel/SPIRE counterparts as well. The Submillimeter Array counterpart to the former SMG is identified at 890 μm and 1.3 mm. Photometric redshift estimates using all available data from the mid-infrared to the radio suggest that the redshifts of the two SMGs are {z}{photo}≃ 4-5 and 3, respectively. Near-infrared objects are found very close to the SMGs and they are consistent with low-z ellipticals, suggesting that the high apparent luminosities can be attributed to gravitational magnification. The cumulative number counts at {S}1.1{mm}≥slant 25 mJy, combined with the other two 1.1 mm brightest sources, are {0.70}-0.34+0.56 deg-2, which is consistent with a model prediction that accounts for flux magnification due to strong gravitational lensing. Unexpectedly, a z\\gt 3 SMG and a Galactic dense starless core (e.g., a first hydrostatic core) could be similar in the mid-infrared to millimeter spectral energy distributions and spatial structures at least at ≳ 1\\prime\\prime . This indicates that it is necessary to distinguish the two possibilities by means of broadband photometry from the optical to centimeter and spectroscopy to determine the redshift, when a compact object is identified toward Galactic star-forming regions.

  14. 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.

  15. C+/H2 gas in star-forming clouds and galaxies

    NASA Astrophysics Data System (ADS)

    Nordon, Raanan; Sternberg, Amiel

    2016-11-01

    We present analytic theory for the total column density of singly ionized carbon (C+) in the optically thick photon dominated regions (PDRs) of far-UV irradiated (star-forming) molecular clouds. We derive a simple formula for the C+ column as a function of the cloud (hydrogen) density, the far-UV field intensity, and metallicity, encompassing the wide range of galaxy conditions. When assuming the typical relation between UV and density in the cold neutral medium, the C+ column becomes a function of the metallicity alone. We verify our analysis with detailed numerical PDR models. For optically thick gas, most of the C+ column is mixed with hydrogen that is primarily molecular (H2), and this `C+/H2' gas layer accounts for almost all of the `CO-dark' molecular gas in PDRs. The C+/H2 column density is limited by dust shielding and is inversely proportional to the metallicity down to ˜0.1 solar. At lower metallicities, H2 line blocking dominates and the C+/H2 column saturates. Applying our theory to CO surveys in low-redshift spirals, we estimate the fraction of C+/H2 gas out of the total molecular gas to be typically ˜0.4. At redshifts 1 < z < 3 in massive disc galaxies the C+/H2 gas represents a very small fraction of the total molecular gas (≲ 0.16). This small fraction at high redshifts is due to the high gas surface densities when compared to local galaxies.

  16. Variations of the ISM Compactness Across the Main Sequence of Star Forming Galaxies: Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Martínez-Galarza, J. R.; Smith, H. A.; Lanz, L.; Hayward, Christopher C.; Zezas, A.; Rosenthal, L.; Weiner, A.; Hung, C.; Ashby, M. L. N.; Groves, B.

    2016-01-01

    The majority of star-forming galaxies follow a simple empirical correlation in the star formation rate (SFR) versus stellar mass (M*) plane, of the form {{SFR}}\\propto {M}*α , usually referred to as the star formation main sequence (MS). The physics that sets the properties of the MS is currently a subject of debate, and no consensus has been reached regarding the fundamental difference between members of the sequence and its outliers. Here we combine a set of hydro-dynamical simulations of interacting galactic disks with state-of-the-art radiative transfer codes to analyze how the evolution of mergers is reflected upon the properties of the MS. We present Chiburst, a Markov Chain Monte Carlo spectral energy distribution (SED) code that fits the multi-wavelength, broad-band photometry of galaxies and derives stellar masses, SFRs, and geometrical properties of the dust distribution. We apply this tool to the SEDs of simulated mergers and compare the derived results with the reference output from the simulations. Our results indicate that changes in the SEDs of mergers as they approach coalescence and depart from the MS are related to an evolution of dust geometry in scales larger than a few hundred parsecs. This is reflected in a correlation between the specific star formation rate, and the compactness parameter { C }, that parametrizes this geometry and hence the evolution of dust temperature ({T}{{dust}}) with time. As mergers approach coalescence, they depart from the MS and increase their compactness, which implies that moderate outliers of the MS are consistent with late-type mergers. By further applying our method to real observations of luminous infrared galaxies (LIRGs), we show that the merger scenario is unable to explain these extreme outliers of the MS. Only by significantly increasing the gas fraction in the simulations are we able to reproduce the SEDs of LIRGs.

  17. CLASH: A census of magnified star-forming galaxies at z ∼ 6-8

    SciTech Connect

    Bradley, L. D.; Coe, D.; Postman, M.; Koekemoer, A.; Zitrin, A.; Carrasco, M.; Bouwens, R.; Balestra, I.; Monna, A.; Seitz, S.; Rosati, P.; Lemze, D.; Zheng, W.; Moustakas, J.; Moustakas, L. A.; Shu, X.; Broadhurst, T.; and others

    2014-09-01

    We utilize 16 band Hubble Space Telescope (HST) observations of 18 lensing clusters obtained as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program to search for z ∼ 6-8 galaxies. We report the discovery of 204, 45, and 13 Lyman-break galaxy candidates at z ∼ 6, z ∼ 7, and z ∼ 8, respectively, identified from purely photometric redshift selections. This large sample, representing nearly an order of magnitude increase in the number of magnified star-forming galaxies at z ∼ 6-8 presented to date, is unique in that we have observations in four WFC3/UVIS UV, seven ACS/WFC optical, and all five WFC3/IR broadband filters, which enable very accurate photometric redshift selections. We construct detailed lensing models for 17 of the 18 clusters to estimate object magnifications and to identify two new multiply lensed z ≳ 6 candidates. The median magnifications over the 17 clusters are 4, 4, and 5 for the z ∼ 6, z ∼ 7, and z ∼ 8 samples, respectively, over an average area of 4.5 arcmin{sup 2} per cluster. We compare our observed number counts with expectations based on convolving 'blank' field UV luminosity functions through our cluster lens models and find rough agreement down to ∼27 mag, where we begin to suffer significant incompleteness. In all three redshift bins, we find a higher number density at brighter observed magnitudes than the field predictions, empirically demonstrating for the first time the enhanced efficiency of lensing clusters over field surveys. Our number counts also are in general agreement with the lensed expectations from the cluster models, especially at z ∼ 6, where we have the best statistics.

  18. The Study of Dusty Star-Forming Galaxies in the Early Universe Through Far-Infrared Observations

    NASA Astrophysics Data System (ADS)

    Calanog, Jae Alyson

    In this thesis I use far-infrared (far-IR) observations performed by the Herschel Space Observatory to study dusty star-forming galaxies, which are believed to be the likely progenitors of massive elliptical galaxies. More specifically, I investigate the far-IR emission of dust-obscured galaxies (DOGs), analyze the near-IR imaging of Herschel-selected lensed galaxies, and investigate the rest-frame UV emission of HFLS3, a z = 6.34 Herschel-selected starburst.

  19. Untangling the nature of spatial variations of cold dust properties in star forming galaxies

    SciTech Connect

    Kirkpatrick, Allison; Calzetti, Daniela; Kennicutt, Robert; Galametz, Maud; Gordon, Karl; Groves, Brent; Tabatabaei, Fatemeh; Hunt, Leslie; Dale, Daniel; Hinz, Joannah

    2014-07-10

    We investigate the far-infrared (IR) dust emission for 20 local star forming galaxies from the Key Insights on Nearby Galaxies: A Far-IR Survey with Herschel (KINGFISH) sample. We model the far-IR/submillimeter spectral energy distribution (SED) using images from Spitzer Space Telescope and Herschel Space Observatory. We calculate the cold dust temperature (T{sub c} ) and emissivity (β) on a pixel by pixel basis (where each pixel ranges from 0.1 to 3 kpc{sup 2}) using a two-temperature modified blackbody fitting routine. Our fitting method allows us to investigate the resolved nature of temperature and emissivity variations by modeling from the galaxy centers to the outskirts (physical scales of ∼15-50 kpc, depending on the size of the galaxy). We fit each SED in two ways: (1) fit T{sub c} and β simultaneously, (2) hold β constant and fit T{sub c} . We compare T{sub c} and β with star formation rates (calculated from L{sub Hα} and L{sub 24μm}), the luminosity of the old stellar population (traced through L{sub 3.6μm}), and the dust mass surface density (traced by 500 μm luminosity, L{sub 500}). We find a significant trend between SFR/L{sub 500} and T{sub c} , implying that the flux of hard UV photons relative to the amount of dust is significantly contributing to the heating of the cold, or diffuse, dust component. We also see a trend between L{sub 3.6}/L{sub 500} and β, indicating that the old stellar population contributes to the heating at far-IR/submillimeter wavelengths. Finally, we find that when β is held constant, T{sub c} exhibits a strongly decreasing radial trend, illustrating that the shape of the far-IR SED is changing radially through a galaxy, thus confirming on a sample almost double in size the trends observed in Galametz et al.

  20. A Hard X-Ray Study of the Normal Star-forming Galaxy M83 with NuSTAR

    NASA Astrophysics Data System (ADS)

    Yukita, M.; Hornschemeier, A. E.; Lehmer, B. D.; Ptak, A.; Wik, D. R.; Zezas, A.; Antoniou, V.; Maccarone, T. J.; Replicon, V.; Tyler, J. B.; Venters, T.; Argo, M. K.; Bechtol, K.; Boggs, S.; Christensen, F. E.; Craig, W. W.; Hailey, C.; Harrison, F.; Krivonos, R.; Kuntz, K.; Stern, D.; Zhang, W. W.

    2016-06-01

    We present the results from sensitive, multi-epoch NuSTAR observations of the late-type star-forming galaxy M83 (d = 4.6 Mpc). This is the first investigation to spatially resolve the hard (E\\gt 10 keV) X-ray emission of this galaxy. The nuclear region and ˜20 off-nuclear point sources, including a previously discovered ultraluminous X-ray source, are detected in our NuSTAR observations. The X-ray hardnesses and luminosities of the majority of the point sources are consistent with hard X-ray sources resolved in the starburst galaxy NGC 253. We infer that the hard X-ray emission is most likely dominated by intermediate accretion state black hole binaries and neutron star low-mass X-ray binaries (Z-sources). We construct the X-ray binary luminosity function (XLF) in the NuSTAR band for an extragalactic environment for the first time. The M83 XLF has a steeper XLF than the X-ray binary XLF in NGC 253, which is consistent with previous measurements by Chandra at softer X-ray energies. The NuSTAR integrated galaxy spectrum of M83 drops quickly above 10 keV, which is also seen in the starburst galaxies NGC 253, NGC 3310, and NGC 3256. The NuSTAR observations constrain any active galactic nucleus (AGN) to be either highly obscured or to have an extremely low luminosity of ≲1038 erg s‑1 (10–30 keV), implying that it is emitting at a very low Eddington ratio. An X-ray point source that is consistent with the location of the nuclear star cluster with an X-ray luminosity of a few times 1038 erg s‑1 may be a low-luminosity AGN but is more consistent with being an X-ray binary.

  1. 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

  2. The Kinematics of C iv in Star-forming Galaxies at z ≈ 1.2

    NASA Astrophysics Data System (ADS)

    Du, Xinnan; Shapley, Alice E.; Martin, Crystal L.; Coil, Alison L.

    2016-10-01

    We present the first statistical sample of rest-frame far-UV spectra of star-forming galaxies at z ˜ 1. These spectra are unique in that they cover the high-ionization C iv λλ1548, 1550 doublet. We also detect low-ionization features such as Si ii λ1526, Fe ii λ1608, Al ii λ1670, Ni ii λλ1741, 1751, and Si ii λ1808, and intermediate-ionization features from Al iii λλ1854, 1862. Comparing the properties of absorption lines of lower- and higher-ionization states provides a window into the multiphase nature of circumgalactic gas. Our sample is drawn from the DEEP2 survey and spans the redshift range 1.01 ≤ z ≤ 1.35 (< z> =1.25). By isolating the interstellar C iv absorption from the stellar P Cygni wind profile, we find that 69% of the C iv profiles are blueshifted with respect to the systemic velocity. Furthermore, C iv shows a small but significant blueshift relative to Fe ii (offset of the best-fit linear regression -76 ± 26 km s-1). At the same time, the C iv blueshift is on average comparable to that of Mg ii λλ2796, 2803. At this point, in explaining the larger blueshift of C iv absorption at the ˜3σ level, we cannot distinguish between the faster motion of highly ionized gas relative to gas traced by Fe ii and filling in on the red side from resonant C iv emission. We investigate how far-UV interstellar absorption kinematics correlate with other galaxy properties using stacked spectra. These stacking results show a direct link between C iv absorption and the current star formation rate, though we only observe small velocity differences among different ionization states tracing the outflowing interstellar medium.

  3. The Lyman continuum escape fraction of low mass star-forming galaxies at z~1.

    NASA Astrophysics Data System (ADS)

    Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian D.; Rafelski, Marc; Henry, Alaina L.; Hayes, Matthew; Salvato, Mara; Pahl, Anthony; Mehta, Vihang; Beck, Melanie; Malkan, Matthew Arnold; Teplitz, Harry I.

    2016-01-01

    Star-forming galaxies (SFGs) in the high redshift universe (z>6) are believed to ionize neutral hydrogen in the intergalactic medium during the epoch of reionization. We tested this assumption by studying likely analogs of these SFGs in archival HST grism spectroscopy with GALEX UV and ground-based optical images at the redshift range in which we can directly measure the rest-frame Lyman continuum (λ<912Å, LyC) emission. We selected ~1400 SFGs for study on the presence of strong Hα emission and strongly selected against those SFGs whose GALEX FUV photometry could be contaminated by low redshift interlopers along the line of sight to produce a sample of ~600 z~1 SFGs. We made no unambiguous detection of escaping Lyman continuum radiation in individual galaxies in this sample, and stacked the individual non-detections in order to constrain the absolute Lyman continuum escape fraction, fesc<2% (3σ). We sub-divided this sample and stacked SFGs to measure upper limits to fesc with respect to stellar mass,luminosity and relative orientation. For z~1 high Hα equivalent width (EW>200Å) SFGs, we found for the first time an upper limit to fesc<9%. We discuss the implications of these limits for the ionizing emissivity of high redshift SFGs during the epoch of reionization. We conclude that reionization by SFGs is only marginally consistent with independent Planck observations of the CMB electron scattering opacity unless the LyC escape fraction of SFGs increases with redshift and an unobserved population of faint (MUV<-13 AB) SFGs contributes significantly to the UV background.

  4. The Redshift Distribution of Dusty Star-forming Galaxies from the SPT Survey

    NASA Astrophysics Data System (ADS)

    Strandet, M. L.; Weiss, A.; Vieira, J. D.; de Breuck, C.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bradford, C. M.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; Everett, W.; Fassnacht, C. D.; Furstenau, R. M.; Gonzalez, A. H.; Greve, T. R.; Gullberg, B.; Hezaveh, Y.; Kamenetzky, J. R.; Litke, K.; Ma, J.; Malkan, M.; Marrone, D. P.; Menten, K. M.; Murphy, E. J.; Nadolski, A.; Rotermund, K. M.; Spilker, J. S.; Stark, A. A.; Welikala, N.

    2016-05-01

    We use the Atacama Large Millimeter/submillimeter Array (ALMA) in Cycle 1 to determine spectroscopic redshifts of high-redshift dusty star-forming galaxies (DSFGs) selected by their 1.4 mm continuum emission in the South Pole Telescope (SPT) survey. We present ALMA 3 mm spectral scans between 84 and 114 GHz for 15 galaxies and targeted ALMA 1 mm observations for an additional eight sources. Our observations yield 30 new line detections from CO, [C i], [N ii], H2O and NH3. We further present Atacama Pathfinder Experiment [C ii] and CO mid-J observations for seven sources for which only a single line was detected in spectral-scan data from ALMA Cycle 0 or Cycle 1. We combine the new observations with previously published and new millimeter/submillimeter line and photometric data of the SPT-selected DSFGs to study their redshift distribution. The combined data yield 39 spectroscopic redshifts from molecular lines, a success rate of >85%. Our sample represents the largest data set of its kind today and has the highest spectroscopic completeness among all redshift surveys of high-z DSFGs. The median of the redshift distribution is z = 3.9 ± 0.4, and the highest-redshift source in our sample is at z = 5.8. We discuss how the selection of our sources affects the redshift distribution, focusing on source brightness, selection wavelength, and strong gravitational lensing. We correct for the effect of gravitational lensing and find the redshift distribution for 1.4 mm selected sources with a median redshift of z = 3.1 ± 0.3. Comparing to redshift distributions selected at shorter wavelengths from the literature, we show that selection wavelength affects the shape of the redshift distribution.

  5. Escape of about five per cent of Lyman-alpha photons from high-redshift star-forming galaxies.

    PubMed

    Hayes, Matthew; Ostlin, Göran; Schaerer, Daniel; Mas-Hesse, J Miguel; Leitherer, Claus; Atek, Hakim; Kunth, Daniel; Verhamme, Anne; de Barros, Stéphane; Melinder, Jens

    2010-03-25

    The Lyman-alpha (Lyalpha) emission line is the primary observational signature of star-forming galaxies at the highest redshifts, and has enabled the compilation of large samples of galaxies with which to study cosmic evolution. The resonant nature of the line, however, means that Lyalpha photons scatter in the neutral interstellar medium of their host galaxies, and their sensitivity to absorption by interstellar dust may therefore be greatly enhanced. This implies that the Lyalpha luminosity may be significantly reduced, or even completely suppressed. Hitherto, no unbiased empirical test of the escaping fraction (f(esc)) of Lyalpha photons has been performed at high redshifts. Here we report that the average f(esc) from star-forming galaxies at redshift z = 2.2 is just 5 per cent by performing a blind narrowband survey in Lyalpha and Halpha. This implies that numerous conclusions based on Lyalpha-selected samples will require upwards revision by an order of magnitude and we provide a benchmark for this revision. We demonstrate that almost 90 per cent of star-forming galaxies emit insufficient Lyalpha to be detected by standard selection criteria. Both samples show an anti-correlation of f(esc) with dust content, and we show that Lyalpha- and Halpha-selection recovers populations that differ substantially in dust content and f(esc).

  6. The Planck Catalogue of High-z source candidates : A laboratory for high-z star forming galaxies

    NASA Astrophysics Data System (ADS)

    Montier, Ludovic

    2015-08-01

    The Planck satellite has provided the first FIR/submm all-sky survey with a sensitivity allowing us to identify the rarest, most luminous high-z dusty star-forming sources on the sky. It opens a new window on these extreme star-forming systems at redshift above 1.5, providing a powerful laboratory to study the mechanisms of galaxy evolution and enrichment in the frame of the large scale structure growth.I will describe how the Planck catalogue of high-z source candidates (PHz, Planck 2015 in prep.) has been built and charcaterized over 25% of the sky by selecting the brightest red submm sources at a 5' resolution. Follow-up observations with Herschel/SPIRE over 228 Planck candidates have shown that 93% of these candidates are actually overdensities of red sources with SEDs peaking at 350um (Planck Int. results. XXVII 2014). Complementarily to this population of objects, 12 Planck high-z candidates have been identified as strongly lensed star forming galaxies at redshift lying between 2.2 and 3.6 (Canameras et al 2015 subm.), with flux densities larger than 400 mJy up to 1 Jy at 350um, and strong magnification factors. These Planck lensed star-forming galaxies are the rarest brightest lensed in the submm range, providing a unique opportunity to extend the exploration of the star-forming system in this range of mass and redshift.I will detail further a specific analysis performed on a proto-cluster candidate, PHz G95.5-61.6, identified as a double structure at z=1.7 and z=2.03, using an extensive follow-up program (Flores-Cacho et al 2015 subm.). This is the first Planck proto-cluster candidate with spectroscopic confirmation, which opens a new field of statistical analysis about the evolution of dusty star-forming galaxies in such accreting structures.I will finally discuss how the PHz catalogue may help to answer some of the fundamental questions like: At what cosmic epoch did massive galaxy clusters form most of their stars? Is star formation more or less vigorous

  7. Ultraviolet to Mid-Infrared Observations of Star-forming Galaxies at z~2: Stellar Masses and Stellar Populations

    NASA Astrophysics Data System (ADS)

    Shapley, Alice E.; Steidel, Charles C.; Erb, Dawn K.; Reddy, Naveen A.; Adelberger, Kurt L.; Pettini, Max; Barmby, Pauline; Huang, Jiasheng

    2005-06-01

    We present the broadband UV through mid-infrared spectral energy distributions (SEDs) of a sample of 72 spectroscopically confirmed star-forming galaxies at z=2.30+/-0.3. Located in a 72 arcmin2 field centered on the bright background QSO, HS 1700+643, these galaxies were preselected to lie at z~2 solely on the basis of their rest-frame UV colors and luminosities and should be representative of UV-selected samples at high redshift. In addition to deep ground-based photometry spanning from 0.35 to 2.15 μm, we make use of Spitzer IRAC data, which probe the rest-frame near-IR at z~2. The range of stellar populations present in the sample is investigated with simple, single-component stellar population synthesis models. The inability to constrain the form of the star formation history limits our ability to determine the parameters of extinction, age, and star formation rate without using external multiwavelength information. Emphasizing stellar mass estimates, which are much less affected by these uncertainties, we find =10.32+/-0.51 for the sample. The addition of Spitzer IRAC data as a long-wavelength baseline reduces stellar mass uncertainties by a factor of 1.5-2 relative to estimates based on optical-Ks photometry alone. However, the total stellar mass estimated for the sample is remarkably insensitive to the inclusion of IRAC data. We find correlations between stellar mass and rest-frame R band (observed Ks) and rest-frame 1.4 μm (observed 4.5 μm) luminosities, although with significant scatter. Even at rest-frame 1.4 μm, the mass-to-light ratio varies by a factor of 15 indicating that even the rest-frame near-IR, when taken alone, is a poor indicator of stellar mass in star-forming galaxies at z~2. Allowing for the possibility of episodic star formation, we find that typical galaxies in our sample could contain up to 3 times more stellar mass in an old underlying burst than what was inferred from single-component modeling. In contrast, mass

  8. Connecting AGN Feedback, the Star-Forming Interstellar Medium, and Galaxy Formation

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip

    The biggest shortcoming in our models of star, supermassive black hole, and galaxy formation is our poor and incomplete understanding of 'feedback' processes. In nearly all models, strong feedback from stars and black holes plays a critical role in regulating the nature of the interstellar medium (ISM) and subsequent generations of star formation and black hole growth. But our theoretical understanding of these processes has largely been restricted to either idealized cases, or simple phenomenological 'sub-grid' prescriptions. These have limited predictive power, and invoke highly uncertain assumptions for the unresolved ISM physics. As such, developing more realistic, explicit treatment of these processes is critical, and one of the primary challenges facing models of both galaxy and star formation. In this proposal, we focus on improving our understanding of AGN feedback by combining novel, high-resolution studies of both black hole growth and galaxy evolution. Critically, these will simultaneously resolve the ISM and both fueling and feedback from black holes, and include fundamentally new physics on galactic scales. Our goal is to anchor these calculations as much as possible in first principles, eliminating large uncertainties in the current models, and enable new predictions on galactic scales. Recently, we developed new numerical models to resolve star formation and feedback on scales from molecular cloud star-forming regions through galaxies. These simulations explicitly follow the energy, momentum, mass, and metal fluxes from stellar radiation pressure, photo-heating, supernovae, and stellar winds; in all cases feedback is tied directly to stellar evolution models. Unlike those previous, the models naturally produce an ISM in which molecular clouds form and disperse rapidly, with realistic phase structure and turbulence. These mechanisms simultaneously drive large galactic outflows; the galactic environment is radically different from the smooth medium of

  9. Herschel protocluster survey: a search for dusty star-forming galaxies in protoclusters at z = 2-3

    NASA Astrophysics Data System (ADS)

    Kato, Y.; Matsuda, Y.; Smail, Ian; Swinbank, A. M.; Hatsukade, B.; Umehata, H.; Tanaka, I.; Saito, T.; Iono, D.; Tamura, Y.; Kohno, K.; Erb, D. K.; Lehmer, B. D.; Geach, J. E.; Steidel, C. C.; Alexander, D. M.; Yamada, T.; Hayashino, T.

    2016-08-01

    We present a Herschel/Spectral and Photometric Imaging Receiver (SPIRE) survey of three protoclusters at z = 2-3 (2QZCluster, HS1700, SSA22). Based on the SPIRE colours (S350/S250 and S500/S350) of 250 μm sources, we selected high-redshift dusty star-forming galaxies potentially associated with the protoclusters. In the 2QZCluster field, we found a 4σ overdensity of six SPIRE sources around 4.5 arcmin (˜2.2 Mpc) from a density peak of H α emitters at z = 2.2. In the HS1700 field, we found a 5σ overdensity of eight SPIRE sources around 2.1 arcmin (˜1.0 Mpc) from a density peak of Lyman-break galaxies at z = 2.3. We did not find any significant overdensities in SSA22 field, but we found three 500 μm sources are concentrated 3 arcmin (˜1.4 Mpc) east to the Ly α emitters overdensity. If all the SPIRE sources in these three overdensities are associated with protoclusters, the inferred star formation rate densities are 103-104 times higher than the average value at the same redshifts. This suggests that dusty star formation activity could be very strongly enhanced in z ˜ 2-3 protoclusters. Further observations are needed to confirm the redshifts of the SPIRE sources and to investigate what processes enhance the dusty star formation activity in z ˜ 2-3 protoclusters.

  10. The SUNBIRD survey: characterizing the super star cluster populations of intensely star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Randriamanakoto, Zara; Vaisanen, Petri; Escala, Andres

    2015-08-01

    This work investigates properties of young, massive and dense star clusters in a sample of 42 nearby starbursts and LIRGs with an average distance of 80 Mpc. The targets form the sample of the SUperNovae and starBursts in the InfraReD (SUNBIRD) survey that were imaged using near-infrared K-band adaptive optics mounted on the Gemini/NIRI and the VLT/NaCo instruments.We fitted power-laws to the SSC K-band luminosity functions and found index values ranging between 1.5 and 2.4 with a median value of α ˜ 1.86±0.24. This is shallower than the average of ≈ 2.4 associated with normal spiral galaxies indicating that SSCs hosted by star-forming galaxies are disrupted in a way depending on their mass or environment. Using simulations we found that blending effects are not significant for targets closer than ≈100Mpc. We also established the first ever near-infrared (NIR) brightest star cluster magnitude - star formation rate (SFR) relation. The correlation has a steeper slope compared to the one with optical data at lower SFRs which could indicate a simple statistical effect, though we argue that a physical truncation of the mass distribution at high masses would better explain the tight scatter of the observed relation.Finally, we combined new NIR imaging of seven LIRG targets with their optical HST archival data to derive the age, mass, and extinction distributions of optically-selected SSC candidates. Apart from having a high mass range of 10^4 - 10^8 M⊙, more than a quarter of the cluster population is younger than 30 Myr. We also derived the cluster initial mass functions and found that at least in one of the LIRGs, a mass-dependent disruption mechanism is responsible for the deficiency in low-mass star clusters. The cluster formation efficiencies Γ = 10 - 23 %, on the other hand, support the arguments that highly-pressurized environments favor SF in bound star clusters.This work has shown the importance of studying SSC host galaxies with high SFR levels to

  11. THE METALLICITY DEPENDENCE OF THE CO {yields} H{sub 2} CONVERSION FACTOR IN z {>=} 1 STAR-FORMING GALAXIES

    SciTech Connect

    Genzel, R.; Tacconi, L. J.; Schreiber, N. M. Foerster; Gracia-Carpio, J.; Lutz, D.; Saintonge, A.; Combes, F.; Bolatto, A.; Neri, R.; Cox, P.; Sternberg, A.; Cooper, M. C.; Bouche, N.; Bournaud, F.; Comerford, J.; Davis, M.; Newman, S.; Garcia-Burillo, S.; Naab, T. E-mail: linda@mpe.mpg.de; and others

    2012-02-10

    We use the first systematic samples of CO millimeter emission in z {>=} 1 'main-sequence' star-forming galaxies to study the metallicity dependence of the conversion factor {alpha}{sub CO,} from CO line luminosity to molecular gas mass. The molecular gas depletion rate inferred from the ratio of the star formation rate (SFR) to CO luminosity, is {approx}1 Gyr{sup -1} for near-solar metallicity galaxies with stellar masses above M{sub S} {approx} 10{sup 11} M{sub Sun }. In this regime, the depletion rate does not vary more than a factor of two to three as a function of molecular gas surface density or redshift between z {approx} 0 and 2. Below M{sub S} the depletion rate increases rapidly with decreasing metallicity. We argue that this trend is not caused by starburst events, by changes in the physical parameters of the molecular clouds, or by the impact of the fundamental-metallicity-SFR-stellar mass relation. A more probable explanation is that the conversion factor is metallicity dependent and that star formation can occur in 'CO-dark' gas. The trend is also expected theoretically from the effect of enhanced photodissociation of CO by ultraviolet radiation at low metallicity. From the available z {approx} 0 and z {approx} 1-3 samples we constrain the slope of the log({alpha}{sub CO})-log (metallicity) relation to range between -1 and -2, fairly insensitive to the assumed slope of the gas-SFR relation. Because of the lower metallicities near the peak of the galaxy formation activity at z {approx} 1-2 compared to z {approx} 0, we suggest that molecular gas masses estimated from CO luminosities have to be substantially corrected upward for galaxies below M{sub S}.

  12. The anatomy of a star-forming galaxy: pressure-driven regulation of star formation in simulated galaxies

    NASA Astrophysics Data System (ADS)

    Benincasa, S. M.; Wadsley, J.; Couchman, H. M. P.; Keller, B. W.

    2016-11-01

    We explore the regulation of star formation in star-forming galaxies through a suite of high-resolution isolated galaxy simulations. We use the smoothed particle hydrodynamics code GASOLINE, including photoelectric heating and metal cooling, which produces a multi-phase interstellar medium (ISM). We show that representative star formation and feedback sub-grid models naturally lead to a weak, sub-linear dependence between the amount of star formation and changes to star formation parameters. We incorporate these sub-grid models into an equilibrium pressure-driven regulation framework. We show that the sub-linear scaling arises as a consequence of the non-linear relationship between scaleheight and the effective pressure generated by stellar feedback. Thus, simulated star formation regulation is sensitive to how well vertical structure in the ISM is resolved. Full galaxy discs experience density waves which drive locally time-dependent star formation. We develop a simple time-dependent, pressure-driven model that reproduces the response extremely well.

  13. AGN and stellar feedback in star-forming galaxies at redshift 2 : outflows, mass-loading and quenching

    NASA Astrophysics Data System (ADS)

    Roos, O.

    2016-06-01

    Galactic-scale outflows are ubiquitous in observations of star-forming galaxies, up to high redshift. Such galactic outflows are mainly generated by internal sources of feedback: young stars, supernovae and active galactic nuclei (AGNs). Still, the physical origins of such outflows are not well understood, and their main driver is still debated. Up to now, most simulations take into account AGN feedback or stellar feedback but not both, because both phenomena happen on very different spatial and time scales. Most of them also still fail to reproduce all observed parameters from first principles. In this poster, we present the POGO project: Physical Origins of Galactic Outflows. With this suite of 23 simulations, we model AGN and stellar feedback simultaneously based on physical assumptions for the first time at very high resolution (6 to 1.5 pc), and investigate their impact on the outflow parameters of the host-galaxy. Here, we show that AGN and stellar feedback couple non-linearly, and that the mass-loading of the resulting outflow highly depends on the mass of the host, all the more because the coupling can either be positive (small masses) or negative (intermediate masses). Nevertheless, the main driver of the outflow remains the AGN at all masses.

  14. Properties of the Interstellar Medium in Star-Forming Galaxies at z ~ 1.4 Revealed with ALMA

    NASA Astrophysics Data System (ADS)

    Seko, Akifumi; Ohta, Kouji; Yabe, Kiyoto; Hatsukade, Bunyo; Akiyama, Masayuki; Iwamuro, Fumihide; Tamura, Naoyuki; Dalton, Gavin

    2016-03-01

    We conducted observations of 12CO(J = 5-4) and dust thermal continuum emission toward 20 star-forming galaxies on the main sequence at z ˜ 1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass versus star formation rate and stellar mass versus metallicity. We detected CO emission lines from 11 galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H2 conversion factor and assuming a CO(5-4)/CO(1-0) luminosity ratio of 0.23. Masses of molecular gas and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9-12) × 1010 M⊙ and 0.25-0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. Dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9-38) × 107 M⊙. We derived gas-to-dust ratios and found they are 3-4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4-36) × 108 yr while the results of the stacking analysis show ˜3 × 108 yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.

  15. PLAYING WITH POSITIVE FEEDBACK: EXTERNAL PRESSURE-TRIGGERING OF A STAR-FORMING DISK GALAXY

    SciTech Connect

    Bieri, Rebekka; Dubois, Yohan; Silk, Joseph; Mamon, Gary A.

    2015-10-20

    In massive galaxies, the currently favored method for quenching star formation is via active galactic nuclei (AGN) feedback, which ejects gas from the galaxy using a central supermassive black hole. At high redshifts however, explanation of the huge rates of star formation often found in galaxies containing AGNs may require a more vigorous mode of star formation than is attainable by simply enriching the gas content of galaxies in the usual gravitationally driven mode that is associated with the nearby universe. Using idealized hydrodynamical simulations, we show that AGN-pressure-driven star formation potentially provides the positive feedback that may be required to generate the accelerated star formation rates observed in the distant universe.

  16. ALMA OBSERVATIONS OF SPT-DISCOVERED, STRONGLY LENSED, DUSTY, STAR-FORMING GALAXIES

    SciTech Connect

    Hezaveh, Y. D.; Marrone, D. P.; Spilker, J. S.; Bothwell, M.; Fassnacht, C. D.; Vieira, J. D.; Aguirre, J. E.; Aird, K. A.; Aravena, M.; De Breuck, C.; Ashby, M. L. N.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Brodwin, M.; Chapman, S. C.; and others

    2013-04-20

    We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 {mu}m imaging of four high-redshift (z = 2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing radio to far-infrared catalogs. At 1.''5 resolution, the ALMA data reveal multiple images of each submillimeter source, separated by 1''-3'', consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpret the source structure. Lens models indicate that SPT0346-52, located at z = 5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 Multiplication-Sign 10{sup 13} L{sub Sun} and star formation surface density of 4200 M{sub Sun} yr{sup -1} kpc{sup -2}. We find magnification factors of 5 to 22, with lens Einstein radii of 1.''1-2.''0 and Einstein enclosed masses of 1.6-7.2 Multiplication-Sign 10{sup 11} M{sub Sun }. These observations confirm the lensing origin of these objects, allow us to measure their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources.

  17. Properties of Interstellar Medium in Star-Forming Galaxies at z~1.4 revealed with ALMA

    NASA Astrophysics Data System (ADS)

    Seko, Akifumi; Ohta, Kouji; Hatsukade, Bunyo; Yabe, Kiyoto

    2015-08-01

    We made CO(J=5-4) observations of 20 star-forming galaxies at z~1.4 with ALMA to study properties of molecular gas with respect to the stellar mass and metallicity. Almost all of our sample galaxies are on the main sequnece of star-forming galaxies at this redshift. Uniqueness of the sample is gas phase metallicity is known for each galaxy. The metallicities of our sample galaxies are derived from near-infrared spectoscopic observations with Subaru/FMOS. The ranges of metallicity (12+log(O/H)) and stellar mass are 8.2-8.9 and 4×109 - 4×1011 Msun, respectively. The stellar mass range covers lower mass than that in previous studies. We detected CO emission lines from 11 galaxies. Molecular gas mass is derived by adopting metallicity-dependent CO-to-H2 conversion factor. The derived molecular gas masses of detected galaxies are (3-11)×1010 Msun. The molecular gas mass fractions are 0.25-0.94, and the fractions is lower in a more massive galaxy or a galaxy with higher metallicity. Stacking analysis also shows the same trends. However, it is difficult to conclude which of stellar mass and metallicity is a main cause for the relations. We try to constrain the inflow and outflow rate at z~1.4 by using an analytic chemical evolution model, in which gas in a galaxy is accumulated by inflow and consumed by star formation and outflow. The results is consistent with that from Hα luminosity assuming the Kennicutt-Schmidt law. Dust thermal continuum emissions are also observed, thus we would like to mention the evolution of gas-to-dust ratio in galaxies.

  18. Massive star-forming host galaxies of quasars on Sloan digital sky survey stripe 82

    SciTech Connect

    Matsuoka, Yoshiki; Strauss, Michael A.; Price, Ted N. III; DiDonato, Matthew S.

    2014-01-10

    The stellar properties of about 800 galaxies hosting optically luminous, unobscured quasars at z < 0.6 are analyzed. Deep co-added Sloan Digital Sky Survey (SDSS) images of the quasars on Stripe 82 are decomposed into nucleus and host galaxy using point spread function and Sérsic models. The systematic errors in the measured galaxy absolute magnitudes and colors are estimated to be less than 0.5 mag and 0.1 mag, respectively, with simulated quasar images. The effect of quasar light scattered by the interstellar medium is also carefully addressed. The measured quasar-to-galaxy ratio in total flux decreases toward longer wavelengths, from ∼8 in the u band to ∼1 in the i and z bands. We find that the SDSS quasars are hosted exclusively by massive galaxies (stellar mass M {sub star} > 10{sup 10} M {sub ☉}), which is consistent with previous results for less luminous narrow-line (obscured) active galactic nuclei (AGNs). The quasar hosts are very blue and almost absent on the red sequence, showing stark contrast to the color-magnitude distribution of normal galaxies. The fact that more powerful AGNs reside in galaxies with higher star-formation efficiency may indicate that negative AGN feedback, if it exists, is not concurrent with the most luminous phase of AGNs. We also find positive correlation between the mass of supermassive black holes (SMBHs; M {sub BH}) and host stellar mass, but the M {sub BH}-M {sub star} relation is offset toward large M {sub BH} or small M {sub star} compared to the local relation. While this could indicate that SMBHs grow earlier than do their host galaxies, such an argument is not conclusive, as the effect may be dominated by observational biases.

  19. The dynamics of z = 0.8 Hα-selected star-forming galaxies from KMOS/CF-HiZELS

    SciTech Connect

    Sobral, D.; Matthee, J.; Swinbank, A. M.; Stott, J. P.; Bower, R. G.; Smail, Ian; Sharples, R. M.; Best, P.; Geach, J. E.

    2013-12-20

    We present the spatially resolved Hα dynamics of 16 star-forming galaxies at z ∼ 0.81 using the new KMOS multi-object integral field spectrograph on the ESO Very Large Telescope. These galaxies, selected using 1.18 μm narrowband imaging from the 10 deg{sup 2} CFHT-HiZELS survey of the SA 22 hr field, are found in a ∼4 Mpc overdensity of Hα emitters and likely reside in a group/intermediate environment, but not a cluster. We confirm and identify a rich group of star-forming galaxies at z = 0.813 ± 0.003, with 13 galaxies within 1000 km s{sup –1} of each other, and seven within a diameter of 3 Mpc. All of our galaxies are 'typical' star-forming galaxies at their redshift, 0.8 ± 0.4 SFR{sub z=0.8}{sup ∗}, spanning a range of specific star formation rates (sSFRs) of 0.2-1.1 Gyr{sup –1} and have a median metallicity very close to solar of 12 + log(O/H) = 8.62 ± 0.06. We measure the spatially resolved Hα dynamics of the galaxies in our sample and show that 13 out of 16 galaxies can be described by rotating disks and use the data to derive inclination corrected rotation speeds of 50-275 km s{sup –1}. The fraction of disks within our sample is 75% ± 8%, consistent with previous results based on Hubble Space Telescope morphologies of Hα-selected galaxies at z ∼ 1 and confirming that disks dominate the SFR density at z ∼ 1. Our Hα galaxies are well fitted by the z ∼ 1-2 Tully-Fisher (TF) relation, confirming the evolution seen in the zero point. Apart from having, on average, higher stellar masses and lower sSFRs, our group galaxies at z = 0.81 present the same mass-metallicity and TF relation as z ∼ 1 field galaxies and are all disk galaxies.

  20. Encoding of the infrared excess in the NUVrK color diagram for star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Arnouts, S.; Le Floc'h, E.; Chevallard, J.; Johnson, B. D.; Ilbert, O.; Treyer, M.; Aussel, H.; Capak, P.; Sanders, D. B.; Scoville, N.; McCracken, H. J.; Milliard, B.; Pozzetti, L.; Salvato, M.

    2013-10-01

    We present an empirical method of assessing the star formation rate (SFR) of star-forming galaxies based on their locations in the rest-frame color-color diagram (NUV - r) vs. (r - K). By using the Spitzer 24 μm sample in the COSMOS field (~16 400 galaxies with 0.2 ≤ z ≤ 1.3) and a local GALEX-SDSS-SWIRE sample (~700 galaxies with z ≤ 0.2), we show that the mean infrared excess ⟨IRX⟩ = ⟨ LIR/LUV ⟩ can be described by a single vector, NRK , that combines the two colors. The calibration between ⟨IRX⟩ and NRK allows us to recover the IR luminosity, LIR, with an accuracy of σ ~ 0.21 for the COSMOS sample and 0.27 dex for the local one. The SFRs derived with this method agree with the ones based on the observed (UV+IR) luminosities and on the spectral energy distribution (SED) fitting for the vast majority (~85%) of the star-forming population. Thanks to a library of model galaxy SEDs with realistic prescriptions for the star formation history, we show that we need to include a two-component dust model (i.e., birth clouds and diffuse ISM) and a full distribution of galaxy inclinations in order to reproduce the behavior of the ⟨IRX⟩ stripes in the NUVrK diagram. In conclusion, the NRK method, based only on the rest-frame UV/optical colors available in most of the extragalactic fields, offers a simple alternative of assessing the SFR of star-forming galaxies in the absence of far-IR or spectral diagnostic observations. Appendices are available in electronic form at http://www.aanda.org

  1. Size evolution of star-forming galaxies with 2

    NASA Astrophysics Data System (ADS)

    Ribeiro, B.; Le Fèvre, O.; Tasca, L. A. M.; Lemaux, B. C.; Cassata, P.; Garilli, B.; Maccagni, D.; Zamorani, G.; Zucca, E.; Amorín, R.; Bardelli, S.; Fontana, A.; Giavalisco, M.; Hathi, N. P.; Koekemoer, A.; Pforr, J.; Tresse, L.; Dunlop, J.

    2016-08-01

    Context. The size of a galaxy encapsulates the signature of the different physical processes driving its evolution. The distribution of galaxy sizes in the Universe as a function of cosmic time is therefore a key to understand galaxy evolution. Aims: We aim to measure the average sizes and size distributions of galaxies as they are assembling before the peak in the comoving star formation rate density of the Universe to better understand the evolution of galaxies across cosmic time. Methods: We used a sample of ~1200 galaxies in the COSMOS and ECDFS fields with confirmed spectroscopic redshifts 2 ≤ zspec ≤ 4.5 in the VIMOS Ultra Deep Survey (VUDS), representative of star-forming galaxies with iAB ≤ 25. We first derived galaxy sizes by applying a classical parametric profile-fitting method using GALFIT. We then measured the total pixel area covered by a galaxy above a given surface brightness threshold, which overcomes the difficulty of measuring sizes of galaxies with irregular shapes. We then compared the results obtained for the equivalent circularized radius enclosing 100% of the measured galaxy light r100T ~2.2 to those obtained with the effective radius re,circ measured with GALFIT. Results: We find that the sizes of galaxies computed with our non-parametric approach span a wide range but remain roughly constant on average with a median value r100T ~2.2 kpc for galaxies with 2 galaxies is severely underestimating their sizes. By comparing r100T with physical parameters obtained through fitting the spectral energy distribution we find that the star-forming galaxies that are the largest at any redshift are, on average, more massive and form more stars. We discover that galaxies present more concentrated light profiles with

  2. GOODS-Herschel: Star Formation, Dust Attenuation, and the FIR-radio Correlation on the Main Sequence of Star-forming Galaxies up to z ≃4

    NASA Astrophysics Data System (ADS)

    Pannella, M.; Elbaz, D.; Daddi, E.; Dickinson, M.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Buat, V.; Charmandaris, V.; Cibinel, A.; Juneau, S.; Ivison, R. J.; Le Borgne, D.; Le Floc'h, E.; Leiton, R.; Lin, L.; Magdis, G.; Morrison, G. E.; Mullaney, J.; Onodera, M.; Renzini, A.; Salim, S.; Sargent, M. T.; Scott, D.; Shu, X.; Wang, T.

    2015-07-01

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate-M* correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR-radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5-4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts. Based on observations collected at the Herschel, Spitzer, Keck, NRAO-VLA, Subaru, KPNO, and CFHT observatories. Herschel is an European Space Agency Cornerstone Mission with science instruments provided by European-led Principal Investigator consortia and

  3. Constraints on the Assembly and Dynamics of Galaxies. I. Detailed Rest-frame Optical Morphologies on Kiloparsec Scale of z ~ 2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Förster Schreiber, N. M.; Shapley, A. E.; Erb, D. K.; Genzel, R.; Steidel, C. C.; Bouché, N.; Cresci, G.; Davies, R.

    2011-04-01

    We present deep and high-resolution Hubble Space Telescope NIC2 F160W imaging at 1.6 μm of six z ~ 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. The unique combination of rest-frame optical imaging and nebular emission-line maps provides simultaneous insight into morphologies and dynamical properties. The overall rest-frame optical emission of the galaxies is characterized by shallow profiles in general (Sérsic index n < 1), with median effective radii of R e ~ 5 kpc. The morphologies are significantly clumpy and irregular, which we quantify through a non-parametric morphological approach, estimating the Gini (G), multiplicity (Ψ), and M 20 coefficients. The estimated strength of the rest-frame optical emission lines in the F160W bandpass indicates that the observed structure is not dominated by the morphology of line-emitting gas, and must reflect the underlying stellar mass distribution of the galaxies. The sizes and structural parameters in the rest-frame optical continuum and Hα emission reveal no significant differences, suggesting similar global distributions of the ongoing star formation and more evolved stellar population. While no strong correlations are observed between stellar population parameters and morphology within the NIC2/SINFONI sample itself, a consideration of the sample in the context of a broader range of z ~ 2 galaxy types (K-selected quiescent, active galactic nucleus, and star forming; 24 μm selected dusty, infrared-luminous) indicates that these galaxies probe the high specific star formation rate and low stellar mass surface density part of the massive z ~ 2 galaxy population, with correspondingly large effective radii, low Sérsic indices, low G, and high Ψ and M 20. The combined NIC2 and SINFONI data set yields insights of unprecedented detail into the nature of mass accretion at high redshift. Based on observations made with the NASA/ESA Hubble Space

  4. Properties of damped Ly α absorption systems and star-forming galaxies in semi-analytic models at z = 2

    NASA Astrophysics Data System (ADS)

    Berry, Michael; Somerville, Rachel S.; Gawiser, Eric; Maller, Ariyeh H.; Popping, Gergö; Trager, Scott C.

    2016-05-01

    We investigate predictions from semi-analytic cosmological models of galaxy formation for the properties of star-forming galaxies (SFGs) and damped Ly α absorption systems (DLAS), and the relationship between these two populations. Our models reproduce fairly well the observed distributions of redshift, stellar mass, star formation rate (SFR), and dust extinction for z ˜ 2 SFGs. We predict that DLA hosts span a broad range of properties, with broad and relatively flat distributions of stellar and halo mass, SFR, and luminosity. The photometric colours of DLA host galaxies trace the colours of galaxies with similar luminosities, but the majority are much fainter than the limits of most existing surveys of SFGs. Generally, DLA host galaxies and SFGs at z = 2 follow similar trends between stellar mass, DLA cross-section, cold gas fraction, SFR, metallicity, and dust extinction as the global population of galaxies with the same stellar mass. Since DLAS select galaxies with larger cold gas masses, they tend to have larger cold gas fractions, lower metallicities, higher SFRs, and less dust extinction than galaxies at the same stellar mass. Our models reproduce the observed relations between impact parameter, column density, and metallicity, suggesting that the sizes of the gas discs giving rise to DLAS in our models are roughly correct. We find that molecular fractions and SFRs are in general significantly lower at the location of the DLA line of sight than the galaxy-averaged value.

  5. The Planck List of High-z source candidates: A laboratory for high-z star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Montier, L.

    The Planck satellite (Planck 2015 results. I) has provided the first FIR/submm all-sky survey with a sensitivity allowing us to identify the rarest, most luminous hig-z dusty star-forming sources on the sky. The Planck list of high-z source candidates (PHZ, PIP XXXIX subm) has been built and charcaterized over 25% of the sky by selecting the 2151 brightest red submm sources at a 5' resolution (Montier et al. 2010). Follow-up observations with Herschel/SPIRE over 228 Planck candidates have already shown that 93% of these candidates are actually overdensities of red sources (PIP XXVII 2015), while 12 Planck high-z candidates are identified as strongly lensed star-forming galaxies at redshift between 2.2 and 3.6 (Canameras et al. 2015). The first confirmed Planck proto-cluster candidate has been revealed to be a double structure at z = 1.7 and zz = 2.03 (Flores-Cacho et al. 2015). The PHZ opens a new window on these extreme star-forming systems at high-z, providing a powerful laboratory to study the mechanisms of galaxy evolution and enrichment in the frame of the large scale structure growth.

  6. The nature of Hα star-forming galaxies at z ˜ 0.4 in and around Cl 0939+4713: the environment matters

    NASA Astrophysics Data System (ADS)

    Sobral, David; Stroe, Andra; Koyama, Yusei; Darvish, Behnam; Calhau, João; Afonso, Ana; Kodama, Tadayuki; Nakata, Fumiaki

    2016-06-01

    Cluster star-forming galaxies are found to have an excess of far-infrared emission relative to Hα, when compared to those in the field, which could be caused by intense active galactic nuclei (AGN) activity, dust and/or declining star formation histories. Here we present spectroscopic observations of Hα emitters in the Cl 0939+4713 (Abell 851) super-cluster at z = 0.41, using AF2+ WYFFOS on the William Herschel Telescope. We measure [O II], Hβ, [O III], Hα and [N II] for a sample of 119 Hα emitters in and around the cluster. We find that 17 ± 5 per cent of the Hα emitters are AGN, irrespective of environment. For star-forming galaxies, we obtain Balmer decrements, metallicities and ionization parameters with different methods, individually and by stacking. We find a strong mass-metallicity relation at all environments, with no significant dependence on environment. The ionization parameter declines with increasing stellar mass for low-mass galaxies. Hα emitters residing in intermediate environments show the highest ionization parameters (along with high [O III]/Hα and high [O III]/[O II] line ratios, typically twice as large as in the highest and lowest densities), which decline with increasing environmental density. Dust extinction (AHα) correlates strongly with stellar mass, but also with environmental density. Star-forming galaxies in the densest environments are found to be significantly dustier (AHα ≈ 1.5 - 1.6) than those residing in the lowest density environments (AHα ≈ 0.6), deviating significantly from what would be predicted given their stellar masses.

  7. The nature of Hα star-forming galaxies at z ˜ 0.4 in and around Cl 0939+4713: the environment matters★

    NASA Astrophysics Data System (ADS)

    Sobral, David; Stroe, Andra; Koyama, Yusei; Darvish, Behnam; Calhau, João; Afonso, Ana; Kodama, Tadayuki; Nakata, Fumiaki

    2016-06-01

    Cluster star-forming galaxies are found to have an excess of far-infrared emission relative to Hα, when compared to those in the field, which could be caused by intense active galactic nuclei (AGN) activity, dust and/or declining star formation histories. Here we present spectroscopic observations of Hα emitters in the Cl 0939+4713 (Abell 851) super-cluster at z = 0.41, using AF2+ WYFFOS on the William Herschel Telescope. We measure [O II], Hβ, [O III], Hα and [N II] for a sample of 119 Hα emitters in and around the cluster. We find that 17 ± 5 per cent of the Hα emitters are AGN, irrespective of environment. For star-forming galaxies, we obtain Balmer decrements, metallicities and ionization parameters with different methods, individually and by stacking. We find a strong mass-metallicity relation at all environments, with no significant dependence on environment. The ionization parameter declines with increasing stellar mass for low-mass galaxies. Hα emitters residing in intermediate environments show the highest ionization parameters (along with high [O III]/Hα and high [O III]/[O II] line ratios, typically twice as large as in the highest and lowest densities), which decline with increasing environmental density. Dust extinction (AHα) correlates strongly with stellar mass, but also with environmental density. Star-forming galaxies in the densest environments are found to be significantly dustier (AHα ≈ 1.5 - 1.6) than those residing in the lowest density environments (AHα ≈ 0.6), deviating significantly from what would be predicted given their stellar masses.

  8. Gas-to-dust ratios in massive star-forming galaxies at z ˜ 1.4

    NASA Astrophysics Data System (ADS)

    Seko, Akifumi; Ohta, Kouji; Yabe, Kiyoto; Hatsukade, Bunyo; Aono, Yuya; Iono, Daisuke

    2016-08-01

    We present results of 12CO(J = 2-1) observations toward four massive star-forming galaxies at z ˜ 1.4 with the Nobeyama 45 m radio telescope. The galaxies are detected with Spitzer/MIPS in 24 μm and Herschel/SPIRE in 250 μm and 350 μm, and they mostly reside in the main sequence. Their gas-phase metallicities derived by the N2 method using the Hα and [N II]λ 6584 emission lines are near the solar value. CO lines are detected toward three galaxies. The molecular-gas masses obtained are (9.6-35) × 1010 M⊙ by adopting the Galactic CO-to-H2 conversion factor and a CO(2-1)/CO(1-0) flux ratio of 3. The dust masses derived from the modified blackbody model (assuming a dust temperature of 35 K and an emissivity index of 1.5) are (2.4-5.4) × 108 M⊙. Resulting gas-to-dust ratios (not accounting for H I mass) at z ˜ 1.4 are 220-1450, which are several times larger than those in local star-forming galaxies. A dependence of the gas-to-dust ratio on the far-infrared luminosity density is not clearly seen.

  9. THE GAS INFLOW AND OUTFLOW RATE IN STAR-FORMING GALAXIES AT z ∼ 1.4

    SciTech Connect

    Yabe, Kiyoto; Ohta, Kouji; Iwamuro, Fumihide; Akiyama, Masayuki; Tamura, Naoyuki; Yuma, Suraphong; Dalton, Gavin; Lewis, Ian

    2015-01-01

    We try to constrain the gas inflow and outflow rate of star-forming galaxies at z ∼ 1.4 by employing a simple analytic model for the chemical evolution of galaxies. The sample is constructed based on a large near-infrared spectroscopic sample observed with Subaru/FMOS. The gas-phase metallicity is measured from the [N II] λ6584/Hα emission line ratio and the gas mass is derived from the extinction corrected Hα luminosity by assuming the Kennicutt-Schmidt law. We constrain the inflow and outflow rate from the least-χ{sup 2} fittings of the observed gas-mass fraction, stellar mass, and metallicity with the analytic model. The joint χ{sup 2} fitting shows that the best-fit inflow rate is ∼1.8 and the outflow rate is ∼0.6 in units of star-formation rate. By applying the same analysis to the previous studies at z ∼ 0 and z ∼ 2.2, it is shown that both the inflow and outflow rates decrease with decreasing redshift, which implies the higher activity of gas flow process at higher redshift. The decreasing trend of the inflow rate from z ∼ 2.2 to z ∼ 0 agrees with that seen in previous observational works with different methods, though the absolute value is generally larger than in previous works. The outflow rate and its evolution from z ∼ 2.2 to z ∼ 0 obtained in this work agree well with the independent estimations in previous observational works.

  10. Spectroscopic Study of Star-forming Galaxies in Filaments and the Field at z ~ 0.5: Evidence for Environmental Dependence of Electron Density

    NASA Astrophysics Data System (ADS)

    Darvish, Behnam; Mobasher, Bahram; Sobral, David; Hemmati, Shoubaneh; Nayyeri, Hooshang; Shivaei, Irene

    2015-12-01

    We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at z ˜ 0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament (˜8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that, on average, filament star-forming galaxies are more metal enriched (˜0.1-0.15 dex), possibly owing to the inflow of the already-enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of ˜17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.

  11. SPECTROSCOPIC STUDY OF STAR-FORMING GALAXIES IN FILAMENTS AND THE FIELD AT z ∼ 0.5: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF ELECTRON DENSITY

    SciTech Connect

    Darvish, Behnam; Mobasher, Bahram; Hemmati, Shoubaneh; Shivaei, Irene; Sobral, David; Nayyeri, Hooshang

    2015-12-01

    We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at z ∼ 0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament (∼8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that, on average, filament star-forming galaxies are more metal enriched (∼0.1–0.15 dex), possibly owing to the inflow of the already-enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of ∼17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.

  12. Spectroscopic Study of Star-forming Galaxies in Filaments and the Field at z~0.5: Evidence for Environmental Dependence of Electron Density

    NASA Astrophysics Data System (ADS)

    Darvish, Behnam; Mobasher, Bahram; Sobral, David; Hemmati, Shoubaneh; Nayyeri, Hooshang; Shivaei, Irene

    2016-01-01

    We study the physical properties of a spectroscopic sample of 28 star-forming galaxies in a large filamentary structure in the COSMOS field at z~0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of 30 field galaxies. We spectroscopically confirm the presence of a large galaxy filament (~ 8 Mpc), along which five confirmed X-ray groups exist. We show that within the uncertainties, the ionization parameter, equivalent width (EW), EW versus specific star-formation rate (sSFR) relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that on average, filament star-forming galaxies are more metal-enriched (~ 0.1-0.15 dex), possibly due to the inflow of the already enriched intrafilamentary gas into filament galaxies. Moreover, we show that electron densities are significantly lower (a factor of ~17) in filament star-forming systems compared to those in the field, possibly because of a longer star-formation timescale for filament star-forming galaxies. Our results highlight the potential pre-processing role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been highly underestimated.

  13. THE NUMBER DENSITY AND MASS DENSITY OF STAR-FORMING AND QUIESCENT GALAXIES AT 0.4 {<=} z {<=} 2.2

    SciTech Connect

    Brammer, Gabriel B.; Whitaker, K. E.; Van Dokkum, P. G.; Lee, K.-S.; Muzzin, A.; Marchesini, D.; Franx, M.; Kriek, M.; Labbe, I.; Quadri, R. F.; Williams, R.; Rudnick, G.

    2011-09-20

    We study the buildup of the bimodal galaxy population using the NEWFIRM Medium-Band Survey, which provides excellent redshifts and well-sampled spectral energy distributions of {approx}27, 000 galaxies with K < 22.8 at 0.4 < z < 2.2. We first show that star-forming galaxies and quiescent galaxies can be robustly separated with a two-color criterion over this entire redshift range. We then study the evolution of the number density and mass density of quiescent and star-forming galaxies, extending the results of the COMBO-17, DEEP2, and other surveys to z = 2.2. The mass density of quiescent galaxies with M {approx}> 3 x 10{sup 10} M{sub sun} increases by a factor of {approx}10 from z {approx} 2 to the present day, whereas the mass density in star-forming galaxies is flat or decreases over the same time period. Modest mass growth by a factor of {approx}2 of individual quiescent galaxies can explain roughly half of the strong density evolution at masses >10{sup 11} M{sub sun}, due to the steepness of the exponential tail of the mass function. The rest of the density evolution of massive, quiescent galaxies is likely due to transformation (e.g., quenching) of the massive star-forming population, a conclusion which is consistent with the density evolution we observe for the star-forming galaxies themselves, which is flat or decreasing with cosmic time. Modest mass growth does not explain the evolution of less massive quiescent galaxies ({approx}10{sup 10.5} M{sub sun}), which show a similarly steep increase in their number densities. The less massive quiescent galaxies are therefore continuously formed by transforming galaxies from the star-forming population.

  14. MOLECULAR AND ATOMIC LINE SURVEYS OF GALAXIES. I. THE DENSE, STAR-FORMING GAS PHASE AS A BEACON

    SciTech Connect

    Geach, James E.; Papadopoulos, Padelis P. E-mail: padelis@mpifr-bonn.mpg.de

    2012-10-01

    We predict the space density of molecular gas reservoirs in the universe and place a lower limit on the number counts of carbon monoxide (CO), hydrogen cyanide (HCN) molecular, and [C II] atomic emission lines in blind redshift surveys in the submillimeter-centimeter spectral regime. Our model uses (1) recently available HCN spectral line energy distributions (SLEDs) of local luminous infrared galaxies (LIRGs, L{sub IR} > 10{sup 11} L{sub Sun }), (2) a value for {epsilon}{sub *} = SFR/M{sub dense}(H{sub 2}) provided by new developments in the study of star formation feedback on the interstellar medium, and (3) a model for the evolution of the infrared luminosity density. Minimal 'emergent' CO SLEDs from the dense gas reservoirs expected in all star-forming systems in the universe are then computed from the HCN SLEDs since warm, HCN-bright gas will necessarily be CO-bright, with the dense star-forming gas phase setting an obvious minimum to the total molecular gas mass of any star-forming galaxy. We include [C II] as the most important of the far-infrared cooling lines. Optimal blind surveys with the Atacama Large Millimeter Array (ALMA) could potentially detect very distant (z {approx} 10-12) [C II] emitters in the {>=}ULIRG galaxy class at a rate of {approx}0.1-1 hr{sup -1} (although this prediction is strongly dependent on the star formation and enrichment history at this early epoch), whereas the (high-frequency) Square Kilometer Array will be capable of blindly detecting z > 3 low-J CO emitters at a rate of {approx}40-70 hr{sup -1}. The [C II] line holds special promise for detecting metal-poor systems with extensive reservoirs of CO-dark molecular gas where detection rates with ALMA can reach up to 2-7 hr{sup -1} in Bands 4-6.

  15. Changing physical conditions in star-forming galaxies between redshifts 0 < z < 4: [O III]/H β evolution

    NASA Astrophysics Data System (ADS)

    Cullen, F.; Cirasuolo, M.; Kewley, L. J.; McLure, R. J.; Dunlop, J. S.; Bowler, R. A. A.

    2016-08-01

    We investigate the redshift evolution of the [O III]/H β nebular emission line ratio for a sample of galaxies spanning the redshift range 0 < z < 4. We compare the observed evolution to a set of theoretical models which account for the independent evolution of chemical abundance, ionization parameter and interstellar medium (ISM) pressure in star-forming galaxies with redshift. Accounting for selection effects in the combined data sets, we show that the evolution to higher [O III]/H β ratios with redshift is a real physical effect which is best accounted for by a model in which the ionization parameter is elevated from the average values typical of local star-forming galaxies, with a possible simultaneous increase in the ISM pressure. We rule out the possibility that the observed [O III]/H β evolution is purely due to metallicity evolution. We discuss the implications of these results for using local empirical metallicity calibrations to measure metallicities at high redshift, and briefly discuss possible theoretical implications of our results.

  16. Mass assembly in quiescent and star-forming galaxies since z ≃ 4 from UltraVISTA

    NASA Astrophysics Data System (ADS)

    Ilbert, O.; McCracken, H. J.; Le Fèvre, O.; Capak, P.; Dunlop, J.; Karim, A.; Renzini, M. A.; Caputi, K.; Boissier, S.; Arnouts, S.; Aussel, H.; Comparat, J.; Guo, Q.; Hudelot, P.; Kartaltepe, J.; Kneib, J. P.; Krogager, J. K.; Le Floc'h, E.; Lilly, S.; Mellier, Y.; Milvang-Jensen, B.; Moutard, T.; Onodera, M.; Richard, J.; Salvato, M.; Sanders, D. B.; Scoville, N.; Silverman, J. D.; Taniguchi, Y.; Tasca, L.; Thomas, R.; Toft, S.; Tresse, L.; Vergani, D.; Wolk, M.; Zirm, A.

    2013-08-01

    We estimate the galaxy stellar mass function and stellar mass density for star-forming and quiescent galaxies with 0.2 < z < 4. We construct a large, deep (Ks < 24) sample of 220 000 galaxies selected using the new UltraVISTA DR1 data release. Our analysis is based on precise 30-band photometricredshifts. By comparing these photometric redshifts with 10,800 spectroscopic redshifts from the zCOSMOS bright and faint surveys, we find a precision of σΔz/(1 + z) = 0.008 at i+ < 22.5 and σΔz/(1 + z) = 0.03 at 1.5 < z < 4. We derive the stellar mass function and correct for the Eddington bias. We find a mass-dependent evolution of the global and star-forming populations, with the low-mass end of the mass functions evolving more rapidly than the high-mass end. This mass-dependent evolution is a direct consequence of the star formation being "quenched" in galaxies more massive than ℳ ≳ 1010.7 - 10.9ℳ⊙. For the mass function of the quiescent galaxies, we do not find any significant evolution of the high-mass end at z < 1; however we observe a clear flattening of the faint-end slope. From z ~ 3 to z ~ 1, the density of quiescent galaxies increases over the entire mass range. Their comoving stellar mass density increases by 1.6 dex between z ~ 3 and z ~ 1 and by less than 0.2 dex at z < 1. We infer the star formation history from the mass density evolution. This inferred star formation history is in excellent agreement with instantaneous star formation rate measurements at z < 1.5, while we find differences of 0.2 dex at z > 1.5 consistent with the expected uncertainties. We also develop a new method to infer the specific star formation rate from the mass function of star-forming galaxies. We find that the specific star formation rate of 1010 - 10.5ℳ⊙ galaxies increases continuously in the redshift range 1 < z < 4. Finally, we compare our results with a semi-analytical model and find that these models overestimate the density of low mass quiescent galaxies by

  17. Radio continuum observations of local star-forming galaxies using the Caltech Continuum Backend on the green bank telescope

    SciTech Connect

    Rabidoux, Katie; Pisano, D. J.; Kepley, Amanda A.; Johnson, Kelsey E.; Balser, Dana S.

    2014-01-01

    We observed radio continuum emission in 27 local (D < 70 Mpc) star-forming galaxies with the Robert C. Byrd Green Bank Telescope between 26 GHz and 40 GHz using the Caltech Continuum Backend. We obtained detections for 22 of these galaxies at all four sub-bands and four more marginal detections by taking the average flux across the entire bandwidth. This is the first detection (full or marginal) at these frequencies for 22 of these galaxies. We fit spectral energy distributions (SEDs) for all of the four sub-band detections. For 14 of the galaxies, SEDs were best fit by a combination of thermal free-free and nonthermal synchrotron components. Eight galaxies with four sub-band detections had steep spectra that were only fit by a single nonthermal component. Using these fits, we calculated supernova rates, total number of equivalent O stars, and star formation rates within each ∼23'' beam. For unresolved galaxies, these physical properties characterize the galaxies' recent star formation on a global scale. We confirm that the radio-far-infrared correlation holds for the unresolved galaxies' total 33 GHz flux regardless of their thermal fractions, though the scatter on this correlation is larger than that at 1.4 GHz. In addition, we found that for the unresolved galaxies, there is an inverse relationship between the ratio of 33 GHz flux to total far-infrared flux and the steepness of the galaxy's spectral index between 1.4 GHz and 33 GHz. This relationship could be an indicator of the timescale of the observed episode of star formation.

  18. ALMA REDSHIFTS OF MILLIMETER-SELECTED GALAXIES FROM THE SPT SURVEY: THE REDSHIFT DISTRIBUTION OF DUSTY STAR-FORMING GALAXIES

    SciTech Connect

    Weiss, A.; De Breuck, C.; Aravena, M.; Biggs, A. D.; Marrone, D. P.; Bothwell, M.; Vieira, J. D.; Bock, J. J.; Aguirre, J. E.; Aird, K. A.; Ashby, M. L. N.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Bethermin, M.; Brodwin, M.; Chapman, S. C.; and others

    2013-04-10

    Using the Atacama Large Millimeter/submillimeter Array, we have conducted a blind redshift survey in the 3 mm atmospheric transmission window for 26 strongly lensed dusty star-forming galaxies (DSFGs) selected with the South Pole Telescope. The sources were selected to have S{sub 1.4{sub mm}} > 20 mJy and a dust-like spectrum and, to remove low-z sources, not have bright radio (S{sub 843{sub MHz}} < 6 mJy) or far-infrared counterparts (S{sub 100{sub {mu}m}} < 1 Jy, S{sub 60{sub {mu}m}} < 200 mJy). We robustly detect 44 line features in our survey, which we identify as redshifted emission lines of {sup 12}CO, {sup 13}CO, C I, H{sub 2}O, and H{sub 2}O{sup +}. We find one or more spectral features in 23 sources yielding a {approx}90% detection rate for this survey; in 12 of these sources we detect multiple lines, while in 11 sources we detect only a single line. For the sources with only one detected line, we break the redshift degeneracy with additional spectroscopic observations if available, or infer the most likely line identification based on photometric data. This yields secure redshifts for {approx}70% of the sample. The three sources with no lines detected are tentatively placed in the redshift desert between 1.7 < z < 2.0. The resulting mean redshift of our sample is z-bar = 3.5. This finding is in contrast to the redshift distribution of radio-identified DSFGs, which have a significantly lower mean redshift of z-bar = 2.3 and for which only 10%-15% of the population is expected to be at z > 3. We discuss the effect of gravitational lensing on the redshift distribution and compare our measured redshift distribution to that of models in the literature.

  19. Far-ultraviolet Imaging Rocket Experiment (FIRE) and the imaging of star-forming regions in galaxies

    NASA Astrophysics Data System (ADS)

    Gantner, Brennan L.

    2012-01-01

    I designed, built, tested and launched a sounding rocket payload to study the far-ultraviolet radiation of M51 (the Whirlpool Galaxy). This instrument, the Far-ultraviolet Imaging Rocket Experiment (FIRE, all acronyms are listed in Appendix), produced the first ever astronomical image of 900-1000 A light. It was designed to look at star forming regions in nearby galaxies by imaging the youngest, hottest O-type stars. Quantifying and locating the star forming regions within galaxies will directly aid galactic formation models. In addition, with the combination of the GALEX two-color images, FIRE was designed to investigate the intervening dust that significantly obscures these wavelengths. Since the accurate correction for dust is vital to measurements across the ultraviolet regime, improving dust extinction models aids a wide variety of both galactic and extra-galactic observations. Finally, FIRE demonstrated the successful use of two novel technologies, a silicon carbide imaging mirror and a pure indium filter. In addition to FIRE, I also examined the absorption of neutral hydrogen in the intergalactic medium (IGM) along quasi-stellar objects (QSO) sightlines. The IGM is expected to contain a significant fraction of baryons at all epochs, but is difficult to detect and map since it diffuse and emits radiation weakly. An ongoing IGM debate is whether clouds of gas detected through their Lyα absorption to QSOs are truly intergalactic or are extended halos of galaxies. A definitive answer would constrain estimates of baryonic density in the local universe and enhance our understanding of the formation of its structure. The CfA Great Wall of galaxies at redshifts of 0:015 < z < 0:03 offers an excellent locale to probe this question. This region is over-dense in galaxies and is surrounded by under-dense galactic voids, enabling us to compare absorbers' nearest galactic neighbors in highly contrasting density regions. I found 167 Lyα absorbers along

  20. Large Binocular Telescope and Sptizer Spectroscopy of Star-forming Galaxies at 1 < z < 3: Extinction and Star Formation Rate Indicators

    NASA Technical Reports Server (NTRS)

    Rujopakarn, W.; Rieke, G. H.; Papovich, C. J.; Weiner, B. J.; Rigby, Jane; Rex, M.; Bian, F.; Kuhn, O. P.; Thompson, D.

    2012-01-01

    We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1 < z < 3 from the LUCIFER instrument on the Large Binocular Telescope and the Infrared Spectrograph on Spitzer. The sample was selected to represent pure, actively star-forming systems, absent of active galactic nuclei. The large lensing magnifications result in high signal-to-noise spectra that can probe faint IR recombination lines, including Paa and Bra at high redshifts. The sample was augmented by three lensed galaxies with similar suites of unpublished data and observations from the literature, resulting in the final sample of seven galaxies. We use the IR recombination lines in conjunction with Ha observations to probe the extinction, Av, of these systems, as well as testing star formation rate (SFR) indicators against the SFR measured by fitting spectral energy distributions to far-IR photometry. Our galaxies occupy a range of Av from 0 to 5.9 mag, larger than previously known for a similar range of IR luminosities at these redshifts. Thus, estimates of SFR even at z 2 must take careful count of extinction in the most IR luminous galaxies.We also measure extinction by comparing SFR estimates from optical emission lines with those from far- IR measurements. The comparison of results from these two independent methods indicates a large variety of dust distribution scenarios at 1 < z < 3. Without correcting for dust extinction, the Ha SFR indicator underestimates the SFR; the size of the necessary correction depends on the IR luminosity and dust distribution scenario. Individual SFR estimates based on the 6.2µm polycyclic aromatic hydrocarbon emission line luminosity do not show a systematic discrepancy with extinction, although a considerable, 0.2 dex, scatter is observed.

  1. Spatially Resolved Spectroscopy and Chemical History of Star-forming Galaxies in the Hercules Cluster: The Effects of the Environment

    NASA Astrophysics Data System (ADS)

    Petropoulou, V.; Vílchez, J.; Iglesias-Páramo, J.; Papaderos, P.; Magrini, L.; Cedrés, B.; Reverte, D.

    2011-06-01

    Spatially resolved spectroscopy has been obtained for a sample of 27 star-forming (SF) galaxies selected from our deep Hα survey of the Hercules cluster. We have applied spectral synthesis models to all emission-line spectra of this sample using the population synthesis code STARLIGHT and have obtained fundamental parameters of stellar components such as mean metallicity and age. The emission-line spectra were corrected for underlying stellar absorption using these spectral synthesis models. Line fluxes were measured and O/H and N/O gas chemical abundances were obtained using the latest empirical calibrations. We have derived the masses and total luminosities of the galaxies using available Sloan Digital Sky Survey broadband photometry. The effects of cluster environment on the chemical evolution of galaxies and on their mass-metallicity (MZ) and luminosity-metallicity (LZ) relations were studied by combining the derived gas metallicities, the mean stellar metallicities and ages, the masses and luminosities of the galaxies, and their existing H I data. Our Hercules SF galaxies are divided into three main subgroups: (1) chemically evolved spirals with truncated ionized-gas disks and nearly flat oxygen gradients, demonstrating the effect of ram-pressure stripping; (2) chemically evolved dwarfs/irregulars populating the highest local densities, possible products of tidal interactions in preprocessing events; and (3) less metallic dwarf galaxies that appear to be "newcomers" to the cluster and are experiencing pressure-triggered star formation. Most Hercules SF galaxies follow well-defined MZ and LZ sequences (for both O/H and N/O), though the dwarf/irregular galaxies located at the densest regions appear to be outliers to these global relations, suggesting a physical reason for the dispersion in these fundamental relations. The Hercules cluster appears to be currently assembling via the merger of smaller substructures, providing an ideal laboratory where the local

  2. SPATIALLY RESOLVED SPECTROSCOPY AND CHEMICAL HISTORY OF STAR-FORMING GALAXIES IN THE HERCULES CLUSTER: THE EFFECTS OF THE ENVIRONMENT

    SciTech Connect

    Petropoulou, V.; Vilchez, J.; Iglesias-Paramo, J.; Cedres, B.; Papaderos, P.; Magrini, L.; Reverte, D.

    2011-06-10

    Spatially resolved spectroscopy has been obtained for a sample of 27 star-forming (SF) galaxies selected from our deep H{alpha} survey of the Hercules cluster. We have applied spectral synthesis models to all emission-line spectra of this sample using the population synthesis code STARLIGHT and have obtained fundamental parameters of stellar components such as mean metallicity and age. The emission-line spectra were corrected for underlying stellar absorption using these spectral synthesis models. Line fluxes were measured and O/H and N/O gas chemical abundances were obtained using the latest empirical calibrations. We have derived the masses and total luminosities of the galaxies using available Sloan Digital Sky Survey broadband photometry. The effects of cluster environment on the chemical evolution of galaxies and on their mass-metallicity (MZ) and luminosity-metallicity (LZ) relations were studied by combining the derived gas metallicities, the mean stellar metallicities and ages, the masses and luminosities of the galaxies, and their existing H I data. Our Hercules SF galaxies are divided into three main subgroups: (1) chemically evolved spirals with truncated ionized-gas disks and nearly flat oxygen gradients, demonstrating the effect of ram-pressure stripping; (2) chemically evolved dwarfs/irregulars populating the highest local densities, possible products of tidal interactions in preprocessing events; and (3) less metallic dwarf galaxies that appear to be 'newcomers' to the cluster and are experiencing pressure-triggered star formation. Most Hercules SF galaxies follow well-defined MZ and LZ sequences (for both O/H and N/O), though the dwarf/irregular galaxies located at the densest regions appear to be outliers to these global relations, suggesting a physical reason for the dispersion in these fundamental relations. The Hercules cluster appears to be currently assembling via the merger of smaller substructures, providing an ideal laboratory where the

  3. Star-forming Brightest Cluster Galaxies at 0.25 > z > 1.25: A Transitioning Fuel Supply

    NASA Astrophysics Data System (ADS)

    McDonald, M.; Stalder, B.; Bayliss, M.; Allen, S. W.; Applegate, D. E.; Ashby, M. L. N.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chiu, I.; Desai, S.; Gonzalez, A. H.; Hlavacek-Larrondo, J.; Holzapfel, W. L.; Marrone, D. P.; Miller, E. D.; Reichardt, C. L.; Saliwanchik, B. R.; Saro, A.; Schrabback, T.; Stanford, S. A.; Stark, A. A.; Vieira, J. D.; Zenteno, A.

    2016-02-01

    We present a multiwavelength study of the 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel’dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star-formation rate (SFR) for the BCG in each cluster—based on the UV and IR continuum luminosity, as well as the [O ii]λλ3726,3729 emission line luminosity in cases where spectroscopy is available—and find seven systems with SFR > 100 M⊙ yr-1. We find that the BCG SFR exceeds 10 M⊙ yr-1 in 31 of 90 (34%) cases at 0.25 < z < 1.25, compared to ˜1%-5% at z ˜ 0 from the literature. At z ≳ 1, this fraction increases to {92}-31+6%, implying a steady decrease in the BCG SFR over the past ˜9 Gyr. At low-z, we find that the specific SFR in BCGs is declining more slowly with time than for field or cluster galaxies, which is most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z ≳ 0.6, the correlation between the cluster central entropy and BCG star formation—which is well established at z ˜ 0—is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We use data from the Hubble Space Telescope to investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs, and find complex, highly asymmetric UV morphologies on scales as large as ˜50-60 kpc. The high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy-galaxy interactions to ICM cooling.

  4. LBT/LUCIFER view of star-forming galaxies in the cluster 7C 1756+6520 at z ˜ 1.4

    NASA Astrophysics Data System (ADS)

    Magrini, Laura; Sommariva, Veronica; Cresci, Giovanni; Sani, Eleonora; Galametz, Audrey; Mannucci, Filippo; Petropoulou, Vasiliki; Fumana, Marco

    2012-10-01

    Galaxy clusters are key places to study the contribution of nature (i.e. mass and morphology) and nurture (i.e. environment) in the formation and evolution of galaxies. Recently, a number of clusters at z > 1, i.e. corresponding to the first epochs of the cluster formation, have been discovered and confirmed spectroscopically. We present new observations obtained with the LBT Near Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCIFER) spectrograph at Large Binocular Telescope (LBT) of a sample of star-forming galaxies associated with a large-scale structure around the radio galaxy 7C 1756+6520 at z = 1.42. Combining our spectroscopic data and the literature photometric data, we derived some of the properties of these galaxies: star formation rate, metallicity and stellar mass. With the aim of analysing the effect of the cluster environment on galaxy evolution, we have located the galaxies in the plane of the so-called fundamental metallicity relation (FMR), which is known not to evolve with redshift up to z = 2.5 for field galaxies, but it is still unexplored in rich environments at low and high redshifts. We found that the properties of the galaxies in the cluster 7C 1756+6520 are compatible with the FMR which suggests that the effect of the environment on galaxy metallicity at this early epoch of cluster formation is marginal. As a side study, we also report the spectroscopic analysis of a bright active galactic nucleus, belonging to the cluster, which shows a significant outflow of gas.

  5. ALMA Imaging and Gravitational Lens Models of South Pole Telescope—Selected Dusty, Star-Forming Galaxies at High Redshifts

    NASA Astrophysics Data System (ADS)

    Spilker, J. S.; Marrone, D. P.; Aravena, M.; Béthermin, M.; Bothwell, M. S.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; de Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Litke, K.; Ma, J.; Malkan, M.; Rotermund, K. M.; Strandet, M.; Vieira, J. D.; Weiss, A.; Welikala, N.

    2016-08-01

    The South Pole Telescope has discovered 100 gravitationally lensed, high-redshift, dusty, star-forming galaxies (DSFGs). We present 0.″5 resolution 870 μ {{m}} Atacama Large Millimeter/submillimeter Array imaging of a sample of 47 DSFGs spanning z=1.9{--}5.7, and construct gravitational lens models of these sources. Our visibility-based lens modeling incorporates several sources of residual interferometric calibration uncertainty, allowing us to properly account for noise in the observations. At least 70% of the sources are strongly lensed by foreground galaxies ({μ }870μ {{m}}\\gt 2), with a median magnification of {μ }870μ {{m}}=6.3, extending to {μ }870μ {{m}}\\gt 30. We compare the intrinsic size distribution of the strongly lensed sources to a similar number of unlensed DSFGs and find no significant differences in spite of a bias between the magnification and intrinsic source size. This may indicate that the true size distribution of DSFGs is relatively narrow. We use the source sizes to constrain the wavelength at which the dust optical depth is unity and find this wavelength to be correlated with the dust temperature. This correlation leads to discrepancies in dust mass estimates of a factor of two compared to estimates using a single value for this wavelength. We investigate the relationship between the [C ii] line and the far-infrared luminosity and find that the same correlation between the [C ii]/{L}{{FIR}} ratio and {{{Σ }}}{{FIR}} found for low-redshift star-forming galaxies applies to high-redshift galaxies and extends at least two orders of magnitude higher in {{{Σ }}}{{FIR}}. This lends further credence to the claim that the compactness of the IR-emitting region is the controlling parameter in establishing the “[C ii] deficit.”

  6. Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution

    NASA Astrophysics Data System (ADS)

    Esteban, C.; García-Rojas, J.; Carigi, L.; Peimbert, M.; Bresolin, F.; López-Sánchez, A. R.; Mesa-Delgado, A.

    2014-09-01

    We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mrk 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the H II region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 Å range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C2+ and/or O2+ from faint pure recombination lines in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O versus O/H, C/O versus N/O and C/N versus O/H relations for Galactic and extragalactic H II regions and comparing with results for Galactic halo stars and damped Lyα systems. We find that H II regions in star-forming dwarf galaxies occupy a different locus in the C/O versus O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic H II regions should have the same origin than in halo stars. The comparison between the C/O ratios in H II regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for H II regions and that this coupling breaks in very low metallicity objects.

  7. Stellar Masses and Start Formation Rates of Lensed Dusty Star-Forming Galaxies from the SPT Survey

    NASA Astrophysics Data System (ADS)

    Ma, Jingzhe; Gonzalez, Anthony; SPT SMG Collaboration

    2016-01-01

    To understand cosmic mass assembly in the Universe at early epochs, we primarily rely on measurements of stellar mass and star formation rate of distant galaxies. In this paper, we present stellar masses and star formation rates of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from ALMA observations. We have conducted follow-up observations, obtaining multi-wavelength imaging data, using HST, Spitzer, Herschel and the Atacama Pathfinder EXperiment (APEX). We use the high-resolution HST/WFC3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and star formation rates (SFRs). The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ˜ 5 ×1010M⊙. The intrinsic IR luminosities range from 4×1012L⊙ to 4×1013L⊙. They all have prodigious intrinsic star formation rates of 510 to 4800 M⊙yr-1. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing the ongoing strong starburst events which may be driven by major mergers.

  8. Deep MUSE observations in the HDFS. Morpho-kinematics of distant star-forming galaxies down to 108M⊙

    NASA Astrophysics Data System (ADS)

    Contini, T.; Epinat, B.; Bouché, N.; Brinchmann, J.; Boogaard, L. A.; Ventou, E.; Bacon, R.; Richard, J.; Weilbacher, P. M.; Wisotzki, L.; Krajnović, D.; Vielfaure, J.-B.; Emsellem, E.; Finley, H.; Inami, H.; Schaye, J.; Swinbank, M.; Guérou, A.; Martinsson, T.; Michel-Dansac, L.; Schroetter, I.; Shirazi, M.; Soucail, G.

    2016-06-01

    gravitational interactions. These fractions are similar to what has been found in previous IFS surveys of more massive galaxies, indicating that the dynamical state of the ionized gas and the level of gravitational interactions of star-forming galaxies is not a strong function of their stellar mass. In the high-mass regime, the MUSE-HDFS galaxies follow the Tully-Fisher relation defined from previous IFS surveys in a similar redshift range. This scaling relation also extends to lower masses/velocities but with a higher dispersion. We find that 90% of the MUSE-HDFS galaxies with stellar masses below 109.5M⊙ have settled gas disks. The MUSE-HDFS galaxies follow the scaling relations defined in the local Universe between the specific angular momentum and stellar mass. However, we find that intermediate-redshift, star-forming galaxies fill a continuum transition from the spiral to elliptical local scaling relations, according to the dynamical state (i.e., rotation- or dispersion-dominated) of the gas. This indicates that some galaxies may lose their angular momentum and become dispersion-dominated prior to becoming passive. Based on observations made with ESO/VLT telescopes at the Paranal Observatory under program ID 60.A-9100(C). Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

  9. Selection and mid-infrared spectroscopy of ultraluminous star-forming galaxies at z ∼ 2

    SciTech Connect

    Fang, Guanwen; Kong, Xu; Chen, Yang; Lin, Xuanbin; Huang, Jia-Sheng; Willner, S. P.; Wang, Tao E-mail: jhuang@cfa.harvard.edu

    2014-02-01

    Starting from a sample of 24 μm sources in the Extended Groth Strip, we use 3.6-8 μm color criteria to select ultraluminous infrared galaxies (ULIRGs) at z ∼ 2. Spectroscopy from 20-38 μm of 14 objects verifies their nature and gives their redshifts. Multi-wavelength data for these objects imply stellar masses >10{sup 11} M {sub ☉} and star formation rates ≥410 M {sub ☉} yr{sup –1}. Four objects of this sample observed at 1.6 μm (rest-frame visible) with Hubble Space Telescope/WFC3 show diverse morphologies, suggesting that multiple formation processes create ULIRGs. Of the 14 objects, 4 show signs of active galactic nuclei, but the luminosity appears to be dominated by star formation in all cases.

  10. Magellan FIRE Spectroscopy of Star-Forming Galaxies at 1.5 < z < 2.3 Selected from the WFC3 Infrared Spectroscopic Parallels (WISP) Survey

    NASA Astrophysics Data System (ADS)

    Masters, Daniel C.; McCarthy, P. J.; Hathi, N. P.; WISP survey Team

    2013-01-01

    We present high-resolution, near-infrared echelle spectra of strongly star-forming emission line galaxies at 1.5 < z < 2.3 taken with FIRE on Magellan. The sample was selected from the WFC3 Infrared Spectroscopic Parallels (WISP) survey, using the slitless grism capability of the WFC3 to identify galaxies with strong emission lines in an unbiased way. We are able to identify low-mass, high sSFR galaxies at these redshifts, which are likely analogues to galaxies in the early stages of formation at much higher redshifts. FIRE follow-up observations provide high-resolution rest-frame optical spectra, allowing us to identify possible AGN activity in the sample, estimate metallicity, and investigate the gas-phase dynamics of the galaxies. By obtaining high-resolution near-IR spectra of a statistically significant number of these galaxies we can begin to understand the population in detail and probe the low-mass end of the mass-metallicity relationship at 2.

  11. The angular momentum of hot coronae around spiral galaxies and its impact on the evolution of star forming discs

    NASA Astrophysics Data System (ADS)

    Pezzulli, G.; Fraternali, F.; Binney, J.

    2016-06-01

    Galaxy formation theory and recent observations indicate that spiral galaxies are surrounded by massive and hot coronae, which potentially constitute a huge source of mass and angular momentum for the star forming discs embedded within them. Accretion from these reservoirs is likely a key ingredient for the evolution of spiral galaxies, but our understanding of the involved processes requires more observational and theoretical investigation, both at global and local scales. In this talk, I focus on some theoretical aspects of the angular momentum distribution of hot coronae. I address, in particular, whether these structures can sustain the inside-out growth of spiral galaxies and what are the dynamical consequences of the accretion of hot coronal gas onto the disc. These processes can have a big impact on observable quantities, most notably gas-phase abundance gradients, which can be used to put constraints on theory. I finally mention ongoing work to understand whether a cosmologically motivated angular momentum distribution for the hot gas is compatible with the constraints from galaxy evolution.

  12. The bursting nature of star formation in compact star-forming galaxies from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Guseva, N. G.; Fricke, K. J.; Henkel, C.

    2016-08-01

    We study integrated characteristics of ˜ 14000 low-redshift (0 < z < 1) compact star-forming galaxies (SFGs) selected from the Data Release 12 of the Sloan Digital Sky Survey. It is found that emission of these galaxies is dominated by strong young bursts of star formation, implying that their luminosities experience rapid variations on a time scale of a few Myr. Reducing integrated characteristics of these galaxies to zero burst age would result in a considerably tighter and almost linear relation between stellar mass and star formation rate (SFR). The same correction implies that the specific star formation rate (the ratio of SFR and stellar mass) is not dependent on the galaxy stellar mass. We conclude that the correction for rapid luminosity evolution must be taken into account in a similar way when comparing different samples of low- and high-redshift SFGs. If the bursting nature of star formation and young burst ages are characteristics of the galaxies selected at high redshifts, the age correction of observed SFRs derived from the Hβ emission line or UV continua would modify the derived SFR densities in the early universe.

  13. The bursting nature of star formation in compact star-forming galaxies from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Guseva, N. G.; Fricke, K. J.; Henkel, C.

    2016-11-01

    We study integrated characteristics of ˜14 000 low-redshift (0 < z < 1) compact star-forming galaxies (SFGs) selected from the Data Release 12 of the Sloan Digital Sky Survey. It is found that emission of these galaxies is dominated by strong young bursts of star formation, implying that their luminosities experience rapid variations on a time-scale of a few Myr. Reducing integrated characteristics of these galaxies to zero burst age would result in a considerably tighter and almost linear relation between stellar mass and star formation rate (SFR). The same correction implies that the specific star formation rate (the ratio of SFR and stellar mass) is not dependent on the galaxy stellar mass. We conclude that the correction for rapid luminosity evolution must be taken into account in a similar way when comparing different samples of low- and high-redshift SFGs. If the bursting nature of star formation and young burst ages are characteristics of the galaxies selected at high redshifts, the age correction of observed SFRs derived from the Hβ emission line or UV continua would modify the derived SFR densities in the early universe.

  14. Star-Forming Brightest Cluster Galaxies at 0.25 < z < 1.25: A Transitioning Fuel Supply

    DOE PAGES

    McDonald, M.; Stalder, B.; Bayliss, M.; Allen, S. W.; Applegate, D. E.; Ashby, M. L. N.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; et al

    2016-01-22

    In this paper, we present a multiwavelength study of the 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star-formation rate (SFR) for the BCG in each cluster—based on the UV and IR continuum luminosity, as well as the [O ii]λλ3726,3729 emission line luminosity in cases where spectroscopy is available—and find seven systems with SFR > 100 M⊙ yr-1. We find that the BCG SFR exceeds 10 M⊙ yr-1 in 31 of 90 (34%) cases at 0.25 < z < 1.25, compared to ~1%–5% at z ~ 0 from the literature. At z ≳ 1, this fraction increases tomore » $${92}_{-31}^{+6}$$%, implying a steady decrease in the BCG SFR over the past ~9 Gyr. At low-z, we find that the specific SFR in BCGs is declining more slowly with time than for field or cluster galaxies, which is most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z ≳ 0.6, the correlation between the cluster central entropy and BCG star formation—which is well established at z ~ 0—is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We use data from the Hubble Space Telescope to investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs, and find complex, highly asymmetric UV morphologies on scales as large as ~50–60 kpc. Finally, the high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy–galaxy interactions to ICM cooling.« less

  15. Star-forming dwarf galaxies in the Virgo cluster: the link between molecular gas, atomic gas, and dust

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Corbelli, E.; Bizzocchi, L.; Giovanardi, C.; Bomans, D.; Coelho, B.; De Looze, I.; Gonçalves, T. S.; Hunt, L. K.; Leonardo, E.; Madden, S.; Menéndez-Delmestre, K.; Pappalardo, C.; Riguccini, L.

    2016-05-01

    We present 12CO(1-0) and 12CO(2-1) observations of a sample of 20 star-forming dwarfs selected from the Herschel Virgo Cluster Survey, with oxygen abundances ranging from 12 + log (O / H) ~ 8.1 to 8.8. CO emission is observed in ten galaxies and marginally detected in another one. CO fluxes correlate with the FIR 250 μm emission, and the dwarfs follow the same linear relation that holds for more massive spiral galaxies extended to a wider dynamical range. We compare different methods to estimate H2 molecular masses, namely a metallicity-dependent CO-to-H2 conversion factor and one dependent on H-band luminosity. The molecular-to-stellar mass ratio remains nearly constant at stellar masses ≲ 109 M⊙, contrary to the atomic hydrogen fraction, MHI/M∗, which increases inversely with M∗. The flattening of the MH2/M∗ ratio at low stellar masses does not seem to be related to the effects of the cluster environment because it occurs for both Hi-deficient and Hi-normal dwarfs. The molecular-to-atomic ratio is more tightly correlated with stellar surface density than metallicity, confirming that the interstellar gas pressure plays a key role in determining the balance between the two gaseous components of the interstellar medium. Virgo dwarfs follow the same linear trend between molecular gas mass and star formation rate as more massive spirals, but gas depletion timescales, τdep, are not constant and range between 100 Myr and 6 Gyr. The interaction with the Virgo cluster environment is removing the atomic gas and dust components of the dwarfs, but the molecular gas appears to be less affected at the current stage of evolution within the cluster. However, the correlation between Hi deficiency and the molecular gas depletion time suggests that the lack of gas replenishment from the outer regions of the disc is lowering the star formation activity. Based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany

  16. The luminosity function of star clusters in 20 star-forming galaxies based on Hubble legacy archive photometry

    SciTech Connect

    Whitmore, Bradley C.; Bowers, Ariel S.; Lindsay, Kevin; Ansari, Asna; Evans, Jessica; Chandar, Rupali; Larsen, Soeren

    2014-04-01

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dL∝L {sup α}, with an average value for α of –2.37 and rms scatter = 0.18 when using the F814W ('I') band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M {sub brightest}) and log of the number

  17. A CO LINE AND INFRARED CONTINUUM STUDY OF THE ACTIVE STAR-FORMING COMPLEX W51

    SciTech Connect

    Kang, Miju; Lee, Youngung; Choi, Minho; Bieging, John H.; Kulesa, Craig A.; Peters, William L.

    2010-09-15

    We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J = 2 - 1 transition of the {sup 12}CO and {sup 13}CO molecules over a 1.{sup 0}25 x 1.{sup 0}00 region with the University of Arizona Heinrich Hertz Submillimeter Telescope. We use a statistical equilibrium code to estimate physical properties of the molecular gas. We compare the molecular cloud morphology with the distribution of infrared (IR) and radio continuum sources and find associations between molecular clouds and young stellar objects (YSOs) listed in Spitzer IR catalogs. The ratios of CO lines associated with H II regions are different from the ratios outside the active star-forming regions. We present evidence of star formation triggered by the expansion of the H II regions and by cloud-cloud collisions. We estimate that about 1% of the cloud mass is currently in YSOs.

  18. A CO Line and Infrared Continuum Study of the Active Star-forming Complex W51

    NASA Astrophysics Data System (ADS)

    Kang, Miju; Bieging, John H.; Kulesa, Craig A.; Lee, Youngung; Choi, Minho; Peters, William L.

    2010-09-01

    We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J = 2 - 1 transition of the 12CO and 13CO molecules over a 1fdg25 × 1fdg00 region with the University of Arizona Heinrich Hertz Submillimeter Telescope. We use a statistical equilibrium code to estimate physical properties of the molecular gas. We compare the molecular cloud morphology with the distribution of infrared (IR) and radio continuum sources and find associations between molecular clouds and young stellar objects (YSOs) listed in Spitzer IR catalogs. The ratios of CO lines associated with H II regions are different from the ratios outside the active star-forming regions. We present evidence of star formation triggered by the expansion of the H II regions and by cloud-cloud collisions. We estimate that about 1% of the cloud mass is currently in YSOs.

  19. A Quantitative Analysis of Star-Forming Galaxies at Intermediate Redshifts: Number Counts, Morphological Sequences, and Evolutionary Timescales

    NASA Astrophysics Data System (ADS)

    Voyer, Elysse

    2011-01-01

    We present a multiwavelength study of rest-frame far-ultraviolet (FUV) selected galaxies at intermediate redshifts (0.1 < z < 1) in the GOODS-N & -S fields. The HST data analyzed were taken with ACS, WFPC2, and WFC3 spanning from FUV to near-infrared bands. The galaxy sample is analyzed in bins of specified time to facilitate comparisons with predictions from theory and simulations of timescales for merger events and morphological transformation in secular evolution scenarios. Quantitative rest-frame i-band morphologies from GALFIT are compared with SED based spectral types revealing trends between morphology and star-formation at intermediate redshifts. Sizes of star-forming clumps are also measured in the rest-frame FUV data for different morphologies to test for size evolution which could be an indication of disk or bulge build-up. We compare morphologies of the star-forming sample to those of a large non-FUV selected galaxy sample in the GOODS-N & -S fields over the same redshift ranges to pinpoint significant morphological differences. We also compare with a local sample obtained from the Sloan Digital Sky Survey representing the local Hubble sequence. The FUV sample is used to measure faint end number counts and the resolved background contribution, covering a larger area (15.9 square arcmin.) than previously observed at these wavelengths (1614Å) and magnitudes (20.5-29.5). Our results are in good agreement with recent semi-analytical models based on dark matter "merger trees” (Somerville et al. 2008, Gilmore et al. 2009) and suggest that other HST studies using smaller detection areas have over-predicted the number counts.

  20. The formation efficiency of high-mass X-ray binaries in our two nearest star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Antoniou, Vallia; Zezas, Andreas

    2016-04-01

    We present the results of our investigation of the link between high-mass X-ray binaries (HMXBs) and star formation in the Magellanic Clouds, our nearest star-forming galaxies. Using the most complete census of HMXBs in the Large Magellanic Cloud (LMC) and the published spatially resolved star-formation history map of this galaxy, we find that the HMXBs (and as expected the X-ray pulsars) are present in regions with star-formation bursts ˜6-25 Myr ago. In contrast, this population peaks at later ages (˜25-60 Myr ago) in the Small Magellanic Cloud (SMC). Thus, this study (in combination with previous works) reinforces the idea that the HMXBs are associated with young stellar populations of ages ˜10-40 Myr. In addition, we estimate an HMXB production rate of 1 system per ˜(23.0-4.1+4.4)×10-3 M⊙/yr or 1 system per ˜143M⊙ of stars formed during the associated star-formation episode. Therefore, the formation efficiency of HMXBs in the LMC is ˜17 times lower than that in the SMC. We attribute this difference primarily in the different ages and metallicity of the HMXB populations in the two galaxies. We also set limits on the kicks imparted on the neutron star during the supernova explosion. We find that the time elapsed since the supernova kick is ˜3 times shorter in the LMC than the SMC. This in combination with the average offsets of the HMXBs from their nearest star clusters results in ˜4 times faster transverse velocities for HMXBs in the LMC than in the SMC.

  1. Escape of Lyα and continuum photons from star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Li, Yuexing; Zhu, Qirong; Abel, Tom; Gronwall, Caryl; Ciardullo, Robin

    2014-05-01

    A large number of high-redshift galaxies have been discovered via their narrow-band Lyα line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lyα, non-ionizing UV-continuum (λ = 1300-1600 Å in rest frame), and ionizing photons (λ < 912 Å) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 53 h-3 Mpc3 with high resolutions using the Aquila initial condition which reproduces a Milky Way-like galaxy at redshift z = 0. We find that the escape fraction (fesc) of these different photons shows a complex dependence on redshift and galaxy properties: f_esc^{{Ly{α }}} and f_esc^UV appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while f_esc^Ion remains roughly constant at ˜0.2 from z ˜ 0 to 10, and it does not show clear dependence on galaxy properties. f_esc^{{Ly{α }}} correlates more strongly with f_esc^UV than with f_esc^Ion. In addition, we find a relation between the emergent Lyα luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z ≳ 6, but they can maintain the ionization of IGM at z ˜ 0-5.

  2. FAINT CO LINE WINGS IN FOUR STAR-FORMING (ULTRA)LUMINOUS INFRARED GALAXIES

    SciTech Connect

    Leroy, Adam K.; Walter, Fabian; Decarli, Roberto; Zschaechner, Laura; Bolatto, Alberto; Weiss, Axel

    2015-09-20

    We report the results of a search for large velocity width, low-intensity line wings—a commonly used signature of molecular outflows—in four low redshift (ultra)luminous infrared galaxies that appear to be dominated by star formation. The targets were drawn from a sample of fourteen targets presented in Chung et al., who showed the stacked CO spectrum of the sample to exhibit 1000 km s{sup −1}-wide line wings. We obtained sensitive, wide bandwidth imaging of our targets using the IRAM Plateau de Bure Interferometer. We detect each target at very high significance but do not find the claimed line wings in these four targets. Instead, we constrain the flux in the line wings to be only a few percent. Casting our results as mass outflow rates following Cicone et al. we show them to be consistent with a picture in which very high mass loading factors preferentially occur in systems with high active galactic nucleus contributions to their bolometric luminosity. We identify one of our targets, IRAS 05083 (VII Zw 31), as a candidate molecular outflow.

  3. Search for gamma-ray emission from star-forming galaxies with Fermi LAT

    NASA Astrophysics Data System (ADS)

    Rojas-Bravo, César; Araya, Miguel

    2016-11-01

    Recent studies have found a positive correlation between the star formation rate (SFR) of galaxies and their gamma-ray luminosity. Galaxies with a high SFR are expected to produce a large amount of high-energy cosmic rays, which emit gamma-rays when interacting with the interstellar medium and radiation fields. We search for gamma-ray emission from a sample of galaxies within and beyond the Local Group with data from the LAT instrument onboard the Fermi satellite. We exclude recently detected galaxies (NGC 253, M82, NGC 4945, NGC 1068, NGC 2146, Arp 220) and use seven years of cumulative `Pass 8' data from the LAT in the 100 MeV to 100 GeV range. No new detections are seen in the data and upper limits for the gamma-ray fluxes are calculated. The correlation between gamma-ray luminosity and infrared luminosity for galaxies obtained using our new upper limits is in agreement with a previously published correlation, but the new upper limits imply that some galaxies are not as efficient gamma-ray emitters as previously thought.

  4. Search for gamma-ray emission from star-forming galaxies with Fermi LAT

    NASA Astrophysics Data System (ADS)

    Rojas-Bravo, César; Araya, Miguel

    2016-08-01

    Recent studies have found a positive correlation between the star-formation rate of galaxies and their gamma-ray luminosity. Galaxies with a high star-formation rate are expected to produce a large amount of high-energy cosmic rays, which emit gamma-rays when interacting with the interstellar medium and radiation fields. We search for gamma-ray emission from a sample of galaxies within and beyond the Local Group with data from the LAT instrument onboard the Fermi satellite. We exclude recently detected galaxies (NGC 253, M82, NGC 4945, NGC 1068, NGC 2146, Arp 220) and use seven years of cumulative "Pass 8" data from the LAT in the 100 MeV to 100 GeV range. No new detections are seen in the data and upper limits for the gamma-ray fluxes are calculated. The correlation between gamma-ray luminosity and infrared luminosity for galaxies obtained using our new upper limits is in agreement with a previously published correlation, but the new upper limits imply that some galaxies are not as efficient gamma-ray emitters as previously thought.

  5. Observing Evolution in Star-Forming Galaxies in X-Rays

    NASA Technical Reports Server (NTRS)

    Ptak, Andrew

    2011-01-01

    The Chandra Deep Fields (CDFs) have reached flux limits where normal/starburst galaxies are significant contributors to the X-ray number counts (approximately 40% at F _{0.5-2.0} = 1 x 10(^)-17). Based on these results and current theoretical models of X-ray binary evolution we will discuss expectations for observing galaxy evolution in X-rays in IXO deep surveys. With the high sensitivity of IXO (particularly approximately 5" resolution constant across the WFI FOV and high effective area) IXO surveys should detect large numbers of galaxies which will allow evolution to be studied in multiple redshift bins. High spatial resolution will also drive the need to minimize source confusion below F _{0.5-2.0 keV} = 10^{-17} ergs/s/cm^2. In addition to detecting starburst galaxies individually, stacking will be used to constrain their properties on average, particularly Lyman-break galaxies at z greater than 2. We will also discuss challenges in segregating galaxies from obscured AGN in IXO deep fields and expectations proposed survey X-ray missions.

  6. A project to unveil the population of Low-Mass Star-Forming Galaxies of the Universe

    NASA Astrophysics Data System (ADS)

    Gallego, Jesus; Rodriguez-Muñoz, Lucía; Tresse, Laurence; Pacifici, Camilla; Charlot, Stéphane; Gil de Paz, Armando; Gomez-Guijarro, Carlos; Villar, Víctor; Barro, Guillermo

    2015-08-01

    Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that low-mass systems merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf systems might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of low-mass systems at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of low-mass dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present constraints on the star formation histories (SFHs) of a sample of low-mass Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFHs were obtained through the analysis of their spectral energy distributions using a novel approach (Pacifici et al. 2012) that (1) consistently combines photometric (HST and ground-based multi-broadband) and spectroscopic (equivalent widths of emission lines from VLT and GTC spectroscopy) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time.The median SFH of our LMSFGs appears to form 90% of the median stellar mass inferred for the sample in the ˜0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for dwarf SFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for a slightly more massive secondary sample 8.0 < log M∗/Mo < 9.1).This is a pilot study for future surveys on dwarf galaxies at high redshift.

  7. VARIABILITY AND STAR FORMATION IN LEO T, THE LOWEST LUMINOSITY STAR-FORMING GALAXY KNOWN TODAY

    SciTech Connect

    Clementini, Gisella; Cignoni, Michele; Ramos, Rodrigo Contreras; Federici, Luciana; Tosi, Monica; Ripepi, Vincenzo; Marconi, Marcella; Musella, Ilaria E-mail: rodrigo.contreras@oabo.inaf.it E-mail: monica.tosi@oabo.inaf.it E-mail: ripepi@na.astro.it E-mail: ilaria@na.astro.it

    2012-09-10

    We present results from the first combined study of variable stars and star formation history (SFH) of the Milky Way 'ultra-faint' dwarf (UFD) galaxy Leo T, based on F606W and F814W multi-epoch archive observations obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. We have detected 14 variable stars in the galaxy. They include one fundamental-mode RR Lyrae star and 11 Anomalous Cepheids with periods shorter than 1 day, thus suggesting the occurrence of multiple star formation episodes in this UFD, of which one about 10 Gyr ago produced the RR Lyrae star. A new estimate of the distance to Leo T of 409{sup +29}{sub -27} kpc (distance modulus of 23.06 {+-} 0.15 mag) was derived from the galaxy's RR Lyrae star. Our V, V - I color-magnitude diagram (CMD) of Leo T reaches V {approx} 29 mag and shows features typical of a galaxy in transition between dwarf irregular and dwarf spheroidal types. A quantitative analysis of the SFH, based on the comparison of the observed V, V - I CMD with the expected distribution of stars for different evolutionary scenarios, confirms that Leo T has a complex SFH dominated by two enhanced periods about 1.5 and 9 Gyr ago, respectively. The distribution of stars and gas shows that the galaxy has a fairly asymmetric structure.

  8. The COSMOS-WIRCam Near-Infrared Imaging Survey. I. BzK-Selected Passive and Star-Forming Galaxy Candidates at z gsim 1.4

    NASA Astrophysics Data System (ADS)

    McCracken, H. J.; Capak, P.; Salvato, M.; Aussel, H.; Thompson, D.; Daddi, E.; Sanders, D. B.; Kneib, J.-P.; Willott, C. J.; Mancini, C.; Renzini, A.; Cook, R.; Le Fèvre, O.; Ilbert, O.; Kartaltepe, J.; Koekemoer, A. M.; Mellier, Y.; Murayama, T.; Scoville, N. Z.; Shioya, Y.; Tanaguchi, Y.

    2010-01-01

    We present a new near-infrared survey covering the 2 deg2 COSMOS field conducted using WIRCam at the Canada-France-Hawaii Telescope. By combining our near-infrared data with Subaru B and z images, we construct a deep, wide-field optical-infrared catalog. At K s < 23 (AB magnitudes), our survey completeness is greater than 90% and 70% for stars and galaxies, respectively, and contains 143,466 galaxies and 13,254 stars. Using the BzK diagram, we divide our galaxy catalog into quiescent and star-forming galaxy candidates. At z ~ 2, our catalogs contain 3931 quiescent and 25,757 star-forming galaxies representing the largest and most secure sample at these depths and redshifts to date. Our counts of quiescent galaxies turns over at K s ~ 22, an effect that we demonstrate cannot be due to sample incompleteness. Both the number of faint and bright quiescent objects in our catalogs exceed the predictions of a recent semi-analytic model of galaxy formation, indicating potentially the need for further refinements in the amount of merging and active galactic nucleus feedback at z ~ 2 in these models. We measure the angular correlation function for each sample and find that the slope of the field galaxy correlation function flattens to 1.5 by K s ~ 23. At small angular scales, the angular correlation function for passive BzK galaxies is considerably in excess of the clustering of dark matter. We use precise 30-band photometric redshifts to derive the spatial correlation length and the redshift distributions for each object class. At K s < 22, we find r γ/1.8 0 = 7.0 ± 0.5h -1 Mpc for the passive BzK candidates and 4.7 ± 0.8 h -1 Mpc for the star-forming BzK galaxies. Our pBzK galaxies have an average photometric redshift of zp ~ 1.4, in approximate agreement with the limited spectroscopic information currently available. The stacked K s image will be made publicly available from IRSA. Based on data collected at the Subaru Telescope, which is operated by the National

  9. UV-selected Young Massive Star Cluster Populations in Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Smith, Linda J.

    2015-08-01

    The Legacy ExtraGalactic UV Survey (LEGUS) is an HST Treasury program aimed at the investigation of star-formation and its relationship to environment in nearby galaxies. The results of a UV-selected study of young massive star clusters in a sample of nearby galaxies (< 10 Mpc) using detections based on the WFC3/UVIS F275W filter will be presented. Previous studies have used V or I-band detections and tend to ignore clusters younger than 10 Myr old. This very young population, which represents the most recent cluster-forming event in the LEGUS galaxies will be discussed.This poster is presented on behalf of the LEGUS team (PI Daniela Calzetti).

  10. The Physical Conditions Of A Lensed Star-forming Galaxy At z=1.7

    NASA Astrophysics Data System (ADS)

    Rigby, Jane R.; 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 dis- covered, 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 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.

  11. 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.

  12. Green Peas and diagnostics for Lyman continuum leaking in star-forming dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Thuan, Trinh

    2014-10-01

    One of the key questions in observational cosmology is the identification of the sources responsible for cosmic reionization. The general consensus is that a population of faint low-mass galaxies must be responsible for the bulk of the ionizing photons. However, attempts at identifying individual galaxies showing Lyman continuum (LyC) leakage have so far not been successful, both at high and low redshifts. We propose here to observe directly the LyC of five so-called "Green Pea" (GP) galaxies. GPs share many of the properties of the Lyman Break galaxies at high z (compactness, low mass, low metallicity, high specific star formation rate, gas-rich and clumpy morphology) and may constitute local examples of the long sought-after LyC leaking galaxies. The five GPs have been identified by searching the Sloan Data Release 10 spectral data base of 2 million spectra for non-AGN emission-line objects that meet the following criteria: high [OIII]5007/[OII]3727 ratios, large GALEX FUV fluxes, and redshifted enough (z~0.3) so that the LyC is shifted into the sensitive spectral range of COS. Our unique GP sample will allow us to combine for the first time four fundamental tests for LyC leaking in galaxies and validate their usefulness as LyC leaking indicators : 1) direct measurements of the LyC; 2) high [OIII]/[OII] ratios; 3) characteristics of the Lyman alpha line profile; and 4) residual intensities in the low-ionization ISM absorption UV lines.

  13. Search for [C II] emission in z = 6.5-11 star-forming galaxies

    SciTech Connect

    González-López, Jorge; Infante, Leopoldo; Riechers, Dominik A. E-mail: linfante@astro.puc.cl; and others

    2014-04-01

    We present the search for the [C II] emission line in three z > 6.5 Lyα emitters (LAEs) and one J-dropout galaxy using the Combined Array for Research in Millimeter-wave Astronomy and the Plateau de Bure Interferometer. We observed three bright z ∼ 6.5-7 LAEs discovered in the Subaru Deep Field (SDF) and the multiple imaged lensed z ∼ 11 galaxy candidate found behind the galaxy cluster MACSJ0647.7+7015. For the LAEs IOK-1 (z = 6.965), SDF J132415.7+273058 (z = 6.541), and SDF J132408.3+271543 (z = 6.554) we find upper limits for the [C II] line luminosity of <2.05, <4.52, and <10.56 × 10{sup 8} L {sub ☉}, respectively. We find upper limits to the far-IR (FIR) luminosity of the galaxies using a spectral energy distribution template of the local galaxy NGC 6946 and taking into account the effects of the cosmic microwave background on the millimeter observations. For IOK-1, SDF J132415.7+273058, and SDF J132408.3+271543 we find upper limits for the FIR luminosity of <2.33, 3.79, and 7.72 × 10{sup 11} L {sub ☉}, respectively. For the lensed galaxy MACS0647-JD, one of the highest-redshift galaxy candidates to date with z{sub ph}=10.7{sub −0.4}{sup +0.6}, we put an upper limit in the [C II] emission of <1.36 × 10{sup 8} × (μ/15){sup –1} L {sub ☉} and an upper limit in the FIR luminosity of <6.1 × 10{sup 10} × (μ/15){sup –1} L {sub ☉} (where μ is the magnification factor). We explore the different conditions relevant for the search for [C II] emission in high-redshift galaxies as well as the difficulties for future observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Cerro Chajnantor Atacama Telescope (CCAT).

  14. THE UV CONTINUUM OF z > 1 STAR-FORMING GALAXIES IN THE HUBBLE ULTRAVIOLET ULTRADEEP FIELD

    SciTech Connect

    Kurczynski, Peter; Gawiser, Eric; Rafelski, Marc; Teplitz, Harry I.; Acquaviva, Viviana; Brown, Thomas M.; Coe, Dan; Grogin, Norman A.; Koekemoer, Anton M.; De Mello, Duilia F.; Finkelstein, Steven L.; Lee, Kyoung-soo; Scarlata, Claudia; Siana, Brian D.

    2014-09-20

    We estimate the UV continuum slope, β, for 923 galaxies in the range 1 < z < 8 in the Hubble Ultradeep Field (HUDF). These data include 460 galaxies at 1 < z < 2 down to an absolute magnitude M{sub UV}=−14(∼0.006 L{sub z=1}{sup ∗};0.02 L{sub z=0}{sup ∗}), comparable to dwarf galaxies in the local universe. We combine deep HST/UVIS photometry in F225W, F275W, F336W wavebands (UVUDF) with recent data from HST/WFC3/IR (HUDF12). Galaxies in the range 1 < z < 2 are significantly bluer than local dwarf galaxies. We find their mean (median) values <β > = – 1.382(– 1.830) ± 0.002 (random) ± 0.1 (systematic). We find comparable scatter in β (standard deviation = 0.43) to local dwarf galaxies and 30% larger scatter than z > 2 galaxies. We study the trends of β with redshift and absolute magnitude for binned sub-samples and find a modest color-magnitude relation, dβ/dM = –0.11 ± 0.01, and no evolution in dβ/dM with redshift. A modest increase in dust reddening with redshift and luminosity, ΔE(B – V) ∼ 0.1, and a comparable increase in the dispersion of dust reddening at z < 2, appears likely to explain the observed trends. At z > 2, we find trends that are consistent with previous works; combining our data with the literature in the range 1 < z < 8, we find a color evolution with redshift, dβ/dz = –0.09 ± 0.01 for low luminosity (0.05 L{sub z=3}{sup ∗}), and dβ/dz = –0.06 ± 0.01 for medium luminosity (0.25 L{sub z=3}{sup ∗}) galaxies.

  15. The structural evolution of Milky-Way-like star-forming galaxies since z ∼ 1.3

    SciTech Connect

    Patel, Shannon G.; Fumagalli, Mattia; Franx, Marijn; Labbé, Ivo; Muzzin, Adam; Van Dokkum, Pieter G.; Leja, Joel; Skelton, Rosalind E.; Momcheva, Ivelina; Nelson, Erica June; Van der Wel, Arjen; Rix, Hans-Walter; Brammer, Gabriel; Whitaker, Katherine E.; Lundgren, Britt; Wake, David A.; Quadri, Ryan F.

    2013-12-01

    We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to z ∼ 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HST survey, which utilizes spectroscopy from the HST/WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sérsic profile fits to CANDELS WFC3 imaging. The progenitors of z = 0 SFGs with stellar mass M = 10{sup 10.5} M {sub ☉} are typically half as massive at z ∼ 1. This late-time stellar mass growth is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at z ∼ 0 have grown in half-light radius by a factor of ∼1.4 since z ∼ 1. The half-light radius grows with stellar mass as r{sub e} ∝M {sup 0.29}. While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of Hα maps for SFGs at z ∼ 1 are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R = 8 kpc to have increased by a factor of ∼2 since z ∼ 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way.

  16. The Structural Evolution of Milky-Way-Like Star-Forming Galaxies zeta is approximately 1.3

    NASA Technical Reports Server (NTRS)

    Patel, Shannon G.; Fumagalli, Mattia; Franx, Marun; VanDokkum, Pieter G.; VanDerWel, Arjen; Leja, Joel; Labbe, Ivo; Brammr, Gabriel; Whitaker, Katherine E.; Skelton, Rosalind E.; Momcheva, Ivelina; Lundgren, Britt; Muzzin, Adam; Quadri, Ryan F.; Nelson, Erica June; Wake, David A.; Rix, Hans-Walter

    2013-01-01

    We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to zeta is approx. 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HT survey, which utilizes spectroscopy from the HST-WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sersic profile fits to CANDELS WFC3 imaging. The progenitors of zeta = 0 SFGs with stellar mass M = 10(exp 10.5) solar mass are typically half as massive at zeta is approx. 1. This late-time stellar mass grow is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at zeta is approx. 0 have grown in half-light radius by a factor of approx. 1.4 zeta is approx. 1. The half-light radius grows with stellar mass as r(sub e) alpha stellar mass(exp 0.29). While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of H(a) maps for SFGs at zeta approx. are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R - 8 kkpc to have increased by a factor of approx. 2 since zeta is approx. 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way.

  17. Velocities of warm galactic outflows from synthetic Hα observations of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel; Arribas, Santiago; Colina, Luis; Rodríguez Del Pino, Bruno; Dekel, Avishai; Primack, Joel

    2016-08-01

    The velocity structure imprinted in the Hα emission line profiles contains valuable information about galactic outflows. Using a set of high-resolution zoom-in cosmological simulations of galaxies at z ≃ 2, we generate Hα emission line profiles, taking into account the temperature-dependent Hα emissivity, as well as dust extinction. The Hα line can be described as a sum of two Gaussians, as typically done with observations. In general, its properties are in good agreement with those observed in local isolated galaxies with similar masses and star formation rates, assuming a spatially constant clumping factor of c ≃ 24. Blueshifted outflows are very common in the sample. They extend several kpc above the galaxy discs. They are also spread over the full extent of the discs. However, at small radii, the material with high velocities tends to remain confined within a thick disc, as part of galactic fountains or a turbulent medium, most probably due to the deeper gravitational potential at the galaxy centre.

  18. Evolution and constrains in the star formation histories of IR-bright star forming galaxies at high redshift

    NASA Astrophysics Data System (ADS)

    Sklias, Panos; Schaerer, Daniel; Elbaz, David

    2015-08-01

    Understanding and constraining the early cosmic star formation history of the Universe is a key question of galaxy evolution. A large fraction of star formation is dust obscured, so it is crucial to have access to the IR emission of galaxies to properly study them.Utilizing the multi-wavelength photometry from GOODS-Herschel, we perform SED fitting with different variable star formation histories (SFHs), which we constrain thanks to the observed IR luminosities, on a large sample of individually IR-detected sources from z~1 to 4. We explore how (and to which extent) constraining dust attenuation thanks to the IR luminosities allows to reduce the scatter (expected when using variable SFHs, in contrast to IR+UV standard calibrations) in physical properties and relations such as mass-SFR and the so-called star-forming Main Sequence (MS).Although limited at the high-z end, our analysis shows a change of trends in SFHs between low and high z, that follows the established cosmic SFR density, with galaxies found to prefer rising SFRs at z~3-4, and declining SFRs at z≤1. We show that a fraction of galaxies (~20%), mainly at z≤2, can have lower SFRs than IR-inferred, but still being compatible with the observations, indicative of being post-starbursts/undergoing quenching while bright in the IR, in agreement with theoretical work. The IR-constrained stellar population models we obtain also indicate that the two main modes of star formation - MS and starburst - evolve differently with time, with the former being mostly slow evolving and lying on the MS for long lasting periods, and the latter being very recent, rapidly increasing bursts (or on the decline, when belonging to the aforementioned "quenched" category). Finally, we illustrate how spectroscopic observation of nebular emission lines further enables as to constrain effectively the SFHs of galaxies.

  19. Investigating the presence of 500 μm submillimeter excess emission in local star forming galaxies

    SciTech Connect

    Kirkpatrick, Allison; Calzetti, Daniela; Galametz, Maud; Kennicutt, Rob Jr.; Dale, Daniel; Aniano, Gonzalo; Sandstrom, Karin; Walter, Fabian; Armus, Lee; Crocker, Alison; Hinz, Joannah; Hunt, Leslie; Koda, Jin

    2013-11-20

    Submillimeter excess emission has been reported at 500 μm in a handful of local galaxies, and previous studies suggest that it could be correlated with metal abundance. We investigate the presence of an excess submillimeter emission at 500 μm for a sample of 20 galaxies from the Key Insights on Nearby Galaxies: a Far Infrared Survey with Herschel (KINGFISH) that span a range of morphologies and metallicities (12 + log (O/H) = 7.8-8.7). We probe the far-infrared (IR) emission using images from the Spitzer Space Telescope and Herschel Space Observatory in the wavelength range 24-500 μm. We model the far-IR peak of the dust emission with a two-temperature modified blackbody and measure excess of the 500 μm photometry relative to that predicted by our model. We compare the submillimeter excess, where present, with global galaxy metallicity and, where available, resolved metallicity measurements. We do not find any correlation between the 500 μm excess and metallicity. A few individual sources do show excess (10%-20%) at 500 μm; conversely, for other sources, the model overpredicts the measured 500 μm flux density by as much as 20%, creating a 500 μm 'deficit'. None of our sources has an excess larger than the calculated 1σ uncertainty, leading us to conclude that there is no substantial excess at submillimeter wavelengths at or shorter than 500 μm in our sample. Our results differ from previous studies detecting 500 μm excess in KINGFISH galaxies largely due to new, improved photometry used in this study.

  20. THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES

    SciTech Connect

    Patel, Shannon G.; Holden, Bradford P.; Illingworth, Garth D.; Franx, Marijn

    2011-07-01

    We study the star formation rates (SFRs) of galaxies as a function of local galaxy density at 0.6 < z < 0.9. We used a low-dispersion prism in IMACS on the 6.5 m Baade (Magellan I) telescope to obtain spectra and measured redshifts to a precision of {sigma}{sub z}/(1 + z) {approx} 1% for galaxies with z{sub AB} < 23.3 mag. We utilized a stellar mass-limited sample of 977 galaxies above M > 1.8 x 10{sup 10} M{sub sun} (log M/M{sub sun} >10.25) to conduct our main analysis. With three different SFR indicators, (1) Spitzer MIPS 24 {mu}m imaging, (2) spectral energy distribution (SED) fitting, and (3) [O II]{lambda}3727 emission, we find the median specific SFR (SSFR) and SFR to decline from the low-density field to the cores of groups and a rich cluster. For the SED- and [O II]-based SFRs, the decline in SSFR is roughly an order of magnitude while for the MIPS-based SFRs, the decline is a factor of {approx}4. We find approximately the same magnitude of decline in SSFR even after removing the sample of galaxies near the cluster. Galaxies in groups and a cluster at these redshifts therefore have lower star formation (SF) activity than galaxies in the field, as is the case at z {approx} 0. We investigated whether the decline in SFR with increasing density is caused by a change in the proportion of quiescent and star-forming galaxies (SFGs) or by a decline in the SFRs of SFGs. Using the rest-frame U - V and V - J colors to distinguish quiescent galaxies from SFGs (including both unattenuated blue galaxies and reddened ones), we find that the fraction of quiescent galaxies increases from {approx}32% to 79% from low to high density. In addition, we find the SSFRs of SFGs, selected based on U - V and V - J colors, to decline with increasing density by factors of {approx}5-6 for the SED- and [O II]-based SFRs. The MIPS-based SSFRs for SFGs decline with a shallower slope. The declining SFRs of SFGs with density are paralleled by a decline in the median A{sub V}, providing

  1. THE STAR-FORMING HISTORIES OF THE NUCLEUS, BULGE, AND INNER DISK OF NGC 5102: CLUES TO THE EVOLUTION OF A NEARBY LENTICULAR GALAXY {sup ,} {sup ,}

    SciTech Connect

    Davidge, T. J.

    2015-01-20

    Long slit spectra recorded with the Gemini Multi-Object Spectrograph on Gemini South are used to examine the star-forming history (SFH) of the lenticular galaxy NGC 5102. Structural and supplemental photometric information are obtained from archival Spitzer [3.6] images. Absorption features at blue and visible wavelengths are traced out along the minor axis to galactocentric radii ∼60 arcsec (∼0.9 kpc), sampling the nucleus, bulge, and disk components. Comparisons with model spectra point to luminosity-weighted metallicities that are consistent with the colors of resolved red giant branch stars in the disk. The nucleus has a luminosity-weighted age at visible wavelengths of ∼1{sub −0.1}{sup +0.2} Gyr, and the integrated light is dominated by stars that formed over a time period of only a few hundred Myr. For comparison, the luminosity-weighted ages of the bulge and disk are ∼2{sub −0.2}{sup +0.5} Gyr and 10{sub −2}{sup +2} Gyr, respectively. The g' – [3.6] colors of the nucleus and bulge are consistent with the spectroscopically based ages. In contrast to the nucleus, models that assume star-forming activity spanning many Gyr provide a better match to the spectra of the bulge and disk than simple stellar population models. Isophotes in the bulge have a disky shape, hinting that the bulge was assembled from material with significant rotational support. The SFHs of the bulge and disk are consistent with the bulge forming from the collapse of a long-lived bar, rather than from the collapse of a transient structure that formed as the result of a tidal interaction. It is thus suggested that the progenitor of NGC 5102 was a barred disk galaxy that morphed into a lenticular galaxy through the buckling of its bar.

  2. H-ATLAS: a candidate high redshift cluster/protocluster of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Clements, D. L.; Braglia, F.; Petitpas, G.; Greenslade, J.; Cooray, A.; Valiante, E.; De Zotti, G.; O'Halloran, B.; Holdship, J.; Morris, B.; Pérez-Fournon, I.; Herranz, D.; Riechers, D.; Baes, M.; Bremer, M.; Bourne, N.; Dannerbauer, H.; Dariush, A.; Dunne, L.; Eales, S.; Fritz, J.; Gonzalez-Nuevo, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Leeuw, L. L.; Maddox, S.; Michałowski, M. J.; Negrello, M.; Omont, A.; Oteo, I.; Serjeant, S.; Valtchanov, I.; Vieira, J. D.; Wardlow, J.; van der Werf, P.

    2016-09-01

    We investigate the region around the Planck-detected z = 3.26 gravitationally lensed galaxy HATLAS J114637.9-001132 (hereinafter HATLAS12-00) using both archival Herschel data from the H-ATLAS survey and using submm data obtained with both LABOCA and SCUBA2. The lensed source is found to be surrounded by a strong overdensity of both Herschel-SPIRE sources and submm sources. We detect 17 bright (S870 > ˜7 mJy) sources at >4σ closer than 5 arcmin to the lensed object at 850/870 μm. 10 of these sources have good cross-identifications with objects detected by Herschel-SPIRE which have redder colours than other sources in the field, with 350 μm flux >250 μm flux, suggesting that they lie at high redshift. Submillimeter Array (SMA) observations localise one of these companions to ˜1 arcsec, allowing unambiguous cross identification with a 3.6 and 4.5 μm Spitzer source. The optical/near-IR spectral energy distribution of this source is measured by further observations and found to be consistent with z > 2, but incompatible with lower redshifts. We conclude that this system may be a galaxy cluster/protocluster or larger scale structure that contains a number of galaxies undergoing starbursts at the same time.

  3. The confinement of star-forming galaxies into a main sequence through episodes of gas compaction, depletion and replenishment

    NASA Astrophysics Data System (ADS)

    Tacchella, Sandro; Dekel, Avishai; Carollo, C. Marcella; Ceverino, Daniel; DeGraf, Colin; Lapiner, Sharon; Mandelker, Nir; Primack Joel, R.

    2016-04-01

    Using cosmological simulations, we address the properties of high-redshift star-forming galaxies (SFGs) across their main sequence (MS) in the plane of star formation rate (SFR) versus stellar mass. We relate them to the evolution of galaxies through phases of gas compaction, depletion, possible replenishment, and eventual quenching. We find that the high-SFR galaxies in the upper envelope of the MS are compact, with high gas fractions and short depletion times (`blue nuggets'), while the lower SFR galaxies in the lower envelope have lower central gas densities, lower gas fractions, and longer depletion times, consistent with observed gradients across the MS. Stellar-structure gradients are negligible. The SFGs oscillate about the MS ridge on time-scales ˜0.4tHubble (˜1 Gyr at z ˜ 3). The propagation upwards is due to gas compaction, triggered, e.g. by mergers, counter-rotating streams, and/or violent disc instabilities. The downturn at the upper envelope is due to central gas depletion by peak star formation and outflows while inflow from the shrunken gas disc is suppressed. An upturn at the lower envelope can occur once the extended disc has been replenished by fresh gas and a new compaction can be triggered, namely as long as the replenishment time is shorter than the depletion time. The mechanisms of gas compaction, depletion, and replenishment confine the SFGs to the narrow (±0.3 dex) MS. Full quenching occurs in massive haloes (Mvir > 1011.5 M⊙) and/or at low redshifts (z < 3), where the replenishment time is long compared to the depletion time, explaining the observed bending down of the MS at the massive end.

  4. The intrinsic scatter along the main sequence of star-forming galaxies at z ∼ 0.7

    SciTech Connect

    Guo, Kexin; Zhong Zheng, Xian; Fu, Hai E-mail: xzzheng@pmo.ac.cn

    2013-11-20

    A sample of 12,614 star-forming galaxies (SFGs) with stellar mass >10{sup 9.5} M {sub ☉} between 0.6 < z < 0.8 from COSMOS is selected to study the intrinsic scatter of the correlation between star formation rate (SFR) and stellar mass. We derive SFR from ultraviolet (UV) and infrared (IR) luminosities. A stacking technique is adopted to measure IR emission for galaxies undetected at 24 μm. We confirm that the slope of the mass-SFR relation is close to unity. We examine the distributions of specific SFRs (SSFRs) in four equally spaced mass bins from 10{sup 9.5} M {sub ☉} to 10{sup 11.5} M {sub ☉}. Different models are used to constrain the scatter of SSFR for lower mass galaxies that are mostly undetected at 24 μm. The SFR scatter is dominated by the scatter of UV luminosity and gradually that of IR luminosity at increasing stellar mass. We derive SSFR dispersions of 0.18, 0.21, 0.26, and 0.31 dex with a typical measurement uncertainty of ≲ 0.01 dex for the four mass bins. Interestingly, the scatter of the mass-SFR relation seems not constant in the sense that the scatter in SSFR is smaller for SFGs of stellar mass <10{sup 10.5} M {sub ☉}. If confirmed, this suggests that the physical processes governing star formation become systematically less violent for less massive galaxies. The SSFR distribution for SFGs with intermediate mass 10{sup 10}-10{sup 10.5} M {sub ☉} is characterized by a prominent excess of intense starbursts in comparison with other mass bins. We argue that this feature reflects that both violent (e.g., major/minor mergers) and quiescent processes are important in regulating star formation in this intermediate-mass regime.

  5. Herschel Extreme Lensing Line Observations: Dynamics of Two Strongly Lensed Star-Forming Galaxies near Redshift z=2*

    NASA Technical Reports Server (NTRS)

    Rhoads, James E.; Rigby, Jane Rebecca; Malhotra, Sangeeta; Allam, Sahar; Carilli, Chris; Combes, Francoise; Finkelstein, Keely; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; Guillard, Pierre; Nesvadba, Nicole; Spaans, Marco; Strauss, Michael A.

    2014-01-01

    We report on two regularly rotating galaxies at redshift z approx. = 2, using high-resolution spectra of the bright [C microns] 158 micrometers emission line from the HIFI instrument on the Herschel Space Observatory. Both SDSS090122.37+181432.3 ("S0901") and SDSSJ120602.09+514229.5 ("the Clone") are strongly lensed and show the double-horned line profile that is typical of rotating gas disks. Using a parametric disk model to fit the emission line profiles, we find that S0901 has a rotation speed of v sin(i) approx. = 120 +/- 7 kms(sup -1) and a gas velocity dispersion of (standard deviation)g < 23 km s(sup -1) (1(standard deviation)). The best-fitting model for the Clone is a rotationally supported disk having v sin(i) approx. = 79 +/- 11 km s(sup -1) and (standard deviation)g 4 kms(sup -1) (1(standard deviation)). However, the Clone is also consistent with a family of dispersion-dominated models having (standard deviation)g = 92 +/- 20 km s(sup -1). Our results showcase the potential of the [C microns] line as a kinematic probe of high-redshift galaxy dynamics: [C microns] is bright, accessible to heterodyne receivers with exquisite velocity resolution, and traces dense star-forming interstellar gas. Future [C microns] line observations with ALMA would offer the further advantage of spatial resolution, allowing a clearer separation between rotation and velocity dispersion.

  6. Chemo -- dynamical, multi -- fragmented SPH code for evolution of star forming disk galaxies

    NASA Astrophysics Data System (ADS)

    Berczik, P.

    The problem of chemical and dynamical evolution of galaxies is one of the most attracting and complex problems of modern astrophysics. Within the framework of the given paper the standard dynamic Smoothed Particle Hydrodynamics (SPH) code (Monaghan J.J. 1992, ARAA, 30, 543) is noticeably expanded. Our work concernes with the changes and incorporation of new ideas into the algorithmic inclusion of Star Formation (SF) and Super Novae (SN) explosions in SPH (Berczik P. & Kravchuk S.G., 1996, ApSpSci, 245, 27). The proposed energy criterion for definition of a place and efficiency of SF results in the successfully explain Star Formation History (SFH) in isolated galaxies of different types. On the base of original ideas we expand a code in a more realistic way of the description of effects of return of a hot, chemical enriched gas in Interstellar Matter (ISM). In addition to the account of SNII, we offer the self-agreed account of SNIa and PN. This allows to describe not only the ISM content of O^16 but also the content of Fe^56 . This model will allow to investigate adequately also a well known G - dwarf problem.

  7. THE DISTANCE TO A STAR-FORMING REGION IN THE OUTER ARM OF THE GALAXY

    SciTech Connect

    Hachisuka, K.; Brunthaler, A.; Menten, K. M.; Reid, M. J.; Hagiwara, Y.; Mochizuki, N.

    2009-05-10

    We performed astrometric observations with the Very Long Baseline Army of WB89-437, an H{sub 2}O maser source in the Outer spiral arm of the Galaxy. We measure an annual parallax of 0.167 {+-} 0.006 mas, corresponding to a heliocentric distance of 6.0 {+-} 0.2 kpc or a Galactocentric distance of 13.4 {+-} 0.2 kpc. This value for the heliocentric distance is considerably smaller than the kinematic distance of 8.6 kpc. This confirms the presence of a faint Outer arm toward l = 135 deg. We also measured the full space motion of the object and find a large peculiar motion of {approx}20 km s{sup -1} toward the Galactic center. This peculiar motion explains the large error in the kinematic distance estimate. We also find that WB89-437 has the same rotation speed as the LSR, providing more evidence for a flat rotation curve and thus the presence of dark matter in the outer Galaxy.

  8. ONE PLANE FOR ALL: MASSIVE STAR-FORMING AND QUIESCENT GALAXIES LIE ON THE SAME MASS FUNDAMENTAL PLANE AT z ∼ 0 AND z ∼ 0.7

    SciTech Connect

    Bezanson, Rachel; Franx, Marijn; Van Dokkum, Pieter G.

    2015-02-01

    Scaling relations between galaxy structures and dynamics have been studied extensively for early- and late-type galaxies, both in the local universe and at high redshifts. The abundant differences between the properties of disky and elliptical, or star-forming and quiescent, galaxies seem to be characteristic of the local universe; such clear distinctions begin to disintegrate as observations of massive galaxies probe higher redshifts. In this paper we investigate the existence of the mass fundamental plane of all massive galaxies (σ ≳ 100 km s{sup –1}). This work includes local galaxies (0.05 < z < 0.07) from the Sloan Digital Sky Survey, in addition to 31 star-forming and 72 quiescent massive galaxies at intermediate redshift (z ∼ 0.7) with absorption-line kinematics from deep Keck-DEIMOS spectra and structural parameters from Hubble Space Telescope imaging. In two-parameter scaling relations, star-forming and quiescent galaxies differ structurally and dynamically. However, we show that massive star-forming and quiescent galaxies lie on nearly the same mass fundamental plane, or the relationship between stellar mass surface density, stellar velocity dispersion, and effective radius. The scatter in this relation (measured about log σ) is low: 0.072 dex (0.055 dex intrinsic) at z ∼ 0 and 0.10 dex (0.08 dex intrinsic) at z ∼ 0.7. This 3D surface is not unique: virial relations, with or without a dependence on luminosity profile shapes, can connect galaxy structures and stellar dynamics with similar scatter. This result builds on the recent finding that mass fundamental plane has been stable for early-type galaxies since z ∼ 2. As we now find that this also holds for star-forming galaxies to z ∼ 0.7, this implies that these scaling relations of galaxies will be minimally susceptible to progenitor biases owing to the evolving stellar populations, structures, and dynamics of galaxies through cosmic time.

  9. THE FMOS-COSMOS SURVEY OF STAR-FORMING GALAXIES AT z ∼ 1.6. III. SURVEY DESIGN, PERFORMANCE, AND SAMPLE CHARACTERISTICS

    SciTech Connect

    Silverman, J. D.; Sugiyama, N.; Kashino, D.; Sanders, D.; Zahid, J.; Kewley, L. J.; Chu, J.; Hasinger, G.; Kartaltepe, J. S.; Arimoto, N.; Renzini, A.; Rodighiero, G.; Baronchelli, I.; Daddi, E.; Juneau, S.; Lilly, S. J.; Carollo, C. M.; Capak, P.; Ilbert, O.; and others

    2015-09-15

    We present a spectroscopic survey of galaxies in the COSMOS field using the Fiber Multi-object Spectrograph (FMOS), a near-infrared instrument on the Subaru Telescope. Our survey is specifically designed to detect the Hα emission line that falls within the H-band (1.6–1.8 μm) spectroscopic window from star-forming galaxies with 1.4 < z < 1.7 and M{sub stellar} ≳ 10{sup 10} M{sub ⊙}. With the high multiplex capability of FMOS, it is now feasible to construct samples of over 1000 galaxies having spectroscopic redshifts at epochs that were previously challenging. The high-resolution mode (R ∼ 2600) effectively separates Hα and [N ii]λ6585, thus enabling studies of the gas-phase metallicity and photoionization state of the interstellar medium. The primary aim of our program is to establish how star formation depends on stellar mass and environment, both recognized as drivers of galaxy evolution at lower redshifts. In addition to the main galaxy sample, our target selection places priority on those detected in the far-infrared by Herschel/PACS to assess the level of obscured star formation and investigate, in detail, outliers from the star formation rate (SFR)—stellar mass relation. Galaxies with Hα detections are followed up with FMOS observations at shorter wavelengths using the J-long (1.11–1.35 μm) grating to detect Hβ and [O iii]λ5008 which provides an assessment of the extinction required to measure SFRs not hampered by dust, and an indication of embedded active galactic nuclei. With 460 redshifts measured from 1153 spectra, we assess the performance of the instrument with respect to achieving our goals, discuss inherent biases in the sample, and detail the emission-line properties. Our higher-level data products, including catalogs and spectra, are available to the community.

  10. A SINFONI view of circum-nuclear star-forming rings in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Falcón-Barroso, Jesús; Böker, Torsten; Schinnerer, Eva; Knapen, Johan H.; Ryder, Stuart

    2008-07-01

    We present near-infrared (H- and K-band) SINFONI integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. We made use of the relative intensities of different emission lines (i.e. [FeII], HeI, Brγ) to age date the stellar clusters present along the rings. This qualitative, yet robust, method allows us to discriminate between two distinct scenarios that describe how star formation progresses along the rings. Our findings favour a model where star formation is triggered predominantly at the intersection between the bar major axis and the inner Lindblad resonance and then passively evolves as the clusters rotate around the ring (‘Pearls on a string’ scenario), although models of stochastically distributed star formation (‘Popcorn’ model) cannot be completely ruled out.

  11. Metal-line absorption around z ≈ 2.4 star-forming galaxies in the Keck Baryonic Structure Survey

    NASA Astrophysics Data System (ADS)

    Turner, Monica L.; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison L.

    2014-11-01

    We study metal absorption around 854 z ≈ 2.4 star-forming galaxies taken from the Keck Baryonic Structure Survey. The galaxies examined in this work lie in the fields of 15 hyperluminous background quasi-stellar objects, with galaxy impact parameters ranging from 35 proper kpc (pkpc) to 2 proper Mpc (pMpc). Using the pixel optical depth technique, we present the first galaxy-centred 2D maps of the median absorption by O VI, N V, C IV, C III, and Si IV, as well as updated results for H I. At small galactocentric radii we detect a strong enhancement of the absorption relative to randomly located regions that extend out to at least 180 pkpc in the transverse direction, and ±240 km s-1 along the line of sight (LOS, ˜1 pMpc in the case of pure Hubble flow) for all ions except N V. For C IV (and H I) we detect a significant enhancement of the absorption signal out to 2 pMpc in the transverse direction, corresponding to the maximum impact parameter in our sample. After normalizing the median absorption profiles to account for variations in line strengths and detection limits, in the transverse direction we find no evidence for a sharp drop-off in metals distinct from that of H I. We argue instead that non-detection of some metal-line species in the extended circumgalactic medium is consistent with differences in the detection sensitivity. Along the LOS, the normalized profiles reveal that the enhancement in the absorption is more extended for O VI, C IV, and Si IV than for H I. We also present measurements of the scatter in the pixel optical depths, covering fractions, and equivalent widths as a function of projected galaxy distance. Limiting the sample to the 340 galaxies with redshifts measured from nebular emission lines does not decrease the extent of the enhancement along the LOS compared to that in the transverse direction. This rules out redshift errors as the source of the observed redshift-space anisotropy and thus implies that we have detected the signature

  12. Evolution of the stellar-to-dark matter relation: Separating star-forming and passive galaxies from z = 1 to 0

    SciTech Connect

    Tinker, Jeremy L.; Leauthaud, Alexie; Bundy, Kevin; George, Matthew R.; Behroozi, Peter; Wechsler, Risa H.; Massey, Richard; Rhodes, Jason

    2013-12-01

    We use measurements of the stellar mass function, galaxy clustering, and galaxy-galaxy lensing within the COSMOS survey to constrain the stellar-to-halo mass relation (SHMR) of star forming and quiescent galaxies over the redshift range z = [0.2, 1.0]. For massive galaxies, M {sub *} ≳ 10{sup 10.6} M {sub ☉}, our results indicate that star-forming galaxies grow proportionately as fast as their dark matter halos while quiescent galaxies are outpaced by dark matter growth. At lower masses, there is minimal difference in the SHMRs, implying that the majority low-mass quiescent galaxies have only recently been quenched of their star formation. Our analysis also affords a breakdown of all COSMOS galaxies into the relative numbers of central and satellite galaxies for both populations. At z = 1, satellite galaxies dominate the red sequence below the knee in the stellar mass function. But the number of quiescent satellites exhibits minimal redshift evolution; all evolution in the red sequence is due to low-mass central galaxies being quenched of their star formation. At M {sub *} ∼ 10{sup 10} M {sub ☉}, the fraction of central galaxies on the red sequence increases by a factor of 10 over our redshift baseline, while the fraction of quenched satellite galaxies at that mass is constant with redshift. We define a 'migration rate' to the red sequence as the time derivative of the passive galaxy abundances. We find that the migration rate of central galaxies to the red sequence increases by nearly an order of magnitude from z = 1 to z = 0. These results imply that the efficiency of quenching star formation for centrals is increasing with cosmic time, while the mechanisms that quench the star formation of satellite galaxies in groups and clusters is losing efficiency.

  13. CONTINUOUS MID-INFRARED STAR FORMATION RATE INDICATORS: DIAGNOSTICS FOR 0 < z < 3 STAR-FORMING GALAXIES

    SciTech Connect

    Battisti, A. J.; Calzetti, D.; Johnson, B. D.; Elbaz, D.

    2015-02-20

    We present continuous, monochromatic star formation rate (SFR) indicators over the mid-infrared wavelength range of 6–70 μm. We use a sample of 58 star-forming galaxies (SFGs) in the Spitzer–SDSS–GALEX Spectroscopic Survey at z < 0.2, for which there is a rich suite of multi-wavelength photometry and spectroscopy from the ultraviolet through to the infrared. The data from the Spitzer Infrared Spectrograph (IRS) of these galaxies, which spans 5–40 μm, is anchored to their photometric counterparts. The spectral region between 40–70 μm is interpolated using dust model fits to the IRS spectrum and Spitzer 70 and 160 μm photometry. Since there are no sharp spectral features in this region, we expect these interpolations to be robust. This spectral range is calibrated as a SFR diagnostic using several reference SFR indicators to mitigate potential bias. Our band-specific continuous SFR indicators are found to be consistent with monochromatic calibrations in the local universe, as derived from Spitzer, WISE, and Herschel photometry. Our local composite template and continuous SFR diagnostics are made available for public use through the NASA/IPAC Infrared Science Archive (IRSA) and have typical dispersions of 30% or less. We discuss the validity and range of applicability for our SFR indicators in the context of unveiling the formation and evolution of galaxies. Additionally, in the era of the James Webb Space Telescope this will become a flexible tool, applicable to any SFG up to z ∼ 3.

  14. Star-forming dwarf galaxies: the correlation between far-infrared and radio fluxes

    NASA Astrophysics Data System (ADS)

    Schleicher, Dominik R. G.; Beck, Rainer

    2016-09-01

    The correlation between far-infrared and radio fluxes connects star formation and magnetic fields in galaxies and has been confirmed over a wide range in luminosities in the far-infrared to radio domain, both in the local Universe and even at redshifts of z ~ 2. Recent investigations have indicated that it may even hold in the regime of local dwarf galaxies, and we therefore explore here the expected behavior in the regime of star formation surface densities below 0.1 M⊙ kpc-2 yr-1. We derive two conditions that can be particularly relevant for inducing a change in the expected correlation: a critical star formation surface density to maintain the correlation between star formation rate and the magnetic field, and a critical star formation surface density below which cosmic-ray diffusion losses dominate their injection through supernova explosions. For rotation periods shorter than 1.5 × 107(H/ kpc)2 yr, with H the scale height of the disk, the first correlation will break down before diffusion losses are relevant because higher star formation rates are required to maintain the correlation between star formation rate and magnetic field strength. For high star formation surface densities ΣSFR, we derive a characteristic scaling of the nonthermal radio to the far-infrared and infrared emission with ΣSFR1/3 , corresponding to a scaling of the nonthermal radio luminosity Ls with the infrared luminosity Lth as Lth4/3 . The latter is expected to change when the above processes are no longer steadily maintained. In the regime of long rotation periods, we expect a transition toward a steeper scaling with ΣSFR2/3, implying Ls ∝ Lth5/3 , while the regime of fast rotation is expected to show a considerably enhanced scatter because a well-defined relation between star formation and magnetic field strength is not maintained. The scaling relations above explain the increasing thermal fraction of the radio emission observed within local dwarfs and can be tested with

  15. Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates

    NASA Technical Reports Server (NTRS)

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B; Conroy, Charlie; Schreiber, Natascha M. Foerster; Franx, Marijn; Fumagalli, Mattia; Lundren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Rix, Hans-Walter; Skelton, Rosalind E.; VanDokkum, Pieter G.; Tease, Katherine Whitaker; Wuyts, Stijn

    2013-01-01

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust towards star-forming regions (measured using Balmer decrements) and the integrated dust properties (derived by comparing spectral energy distributions [SEDs] with stellar population and dust models) for a statistically significant sample of distant galaxies. We select a sample of 163 galaxies between 1.36< or = z< or = 1.5 with H(alpha) SNR > or = 5 and measure Balmer decrements from stacked spectra. First, we stack spectra in bins of integrated stellar dust attenuation, and find that there is extra dust extinction towards star-forming regions (AV,HII is 1.81 times the integrated AV, star), though slightly lower than found for low-redshift starburst galaxies. Next, we stack spectra in bins of specific star formation rate (log sSFR), star formation rate (log SFR), and stellar mass (logM*). We find that on average AV,HII increases with SFR and mass, but decreases with increasing sSFR. The amount of extra extinction also decreases with increasing sSFR and decreasing stellar mass. Our results are consistent with the two-phase dust model - in which galaxies contain both a diffuse and a stellar birth cloud dust component - as the extra extinction will increase once older stars outside the star-forming regions become more dominant. Finally, using our Balmer decrements we derive dust-corrected H(alpha) SFRs, and find evidence that SED fitting produces incorrect SFRs if very rapidly declining SFHs are included in the explored parameter space. Subject headings: dust, extinction- galaxies: evolution- galaxies: high-redshift

  16. THE OPTICALLY UNBIASED GRB HOST (TOUGH) SURVEY. VI. RADIO OBSERVATIONS AT z {approx}< 1 AND CONSISTENCY WITH TYPICAL STAR-FORMING GALAXIES

    SciTech Connect

    Michalowski, M. J.; Dunlop, J. S.; Kamble, A.; Kaplan, D. L.; Hjorth, J.; Malesani, D.; Fynbo, J. P. U.; Kruehler, T.; Reinfrank, R. F.; Bonavera, L.; Ibar, E.; Garrett, M. A.; Jakobsson, P.; Levan, A. J.; Massardi, M.; Pal, S.; Sollerman, J.; Tanvir, N. R.; Van der Horst, A. J.; and others

    2012-08-20

    The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of {approx}825 M{sub Sun} yr{sup -1}, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least {approx}63% of GRB hosts have SFR < 100 M{sub Sun} yr{sup -1} and at most {approx}8% can have SFR > 500 M{sub Sun} yr{sup -1}. For the undetected hosts the mean radio flux (<35 {mu}Jy 3{sigma}) corresponds to an average SFR < 15 M{sub Sun} yr{sup -1}. Moreover, {approx}> 88% of the z {approx}< 1 GRB hosts have ultraviolet dust attenuation A{sub UV} < 6.7 mag (visual attenuation A{sub V} < 3 mag). Hence, we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A{sub UV} of GRB hosts are consistent with those of Lyman break galaxies, H{alpha} emitters at similar redshifts, and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z {approx}< 1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought.

  17. The Optically Unbiased GRB Host (TOUGH) Survey. VI. Radio Observations at z <~ 1 and Consistency with Typical Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Michałowski, M. J.; Kamble, A.; Hjorth, J.; Malesani, D.; Reinfrank, R. F.; Bonavera, L.; Castro Cerón, J. M.; Ibar, E.; Dunlop, J. S.; Fynbo, J. P. U.; Garrett, M. A.; Jakobsson, P.; Kaplan, D. L.; Krühler, T.; Levan, A. J.; Massardi, M.; Pal, S.; Sollerman, J.; Tanvir, N. R.; van der Horst, A. J.; Watson, D.; Wiersema, K.

    2012-08-01

    The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of ~825 M ⊙ yr-1, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least ~63% of GRB hosts have SFR < 100 M ⊙ yr-1 and at most ~8% can have SFR > 500 M ⊙ yr-1. For the undetected hosts the mean radio flux (<35 μJy 3σ) corresponds to an average SFR < 15 M ⊙ yr-1. Moreover, >~ 88% of the z <~ 1 GRB hosts have ultraviolet dust attenuation A UV < 6.7 mag (visual attenuation AV < 3 mag). Hence, we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A UV of GRB hosts are consistent with those of Lyman break galaxies, Hα emitters at similar redshifts, and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z <~ 1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Large Programme 177.A-0591), the Australian Telescope Compact Array, the Giant Metrewave Radio Telescope, the Very Large Array, and the Westerbork

  18. The Angular Momentum Distribution and Baryon Content of Star-forming Galaxies at z ˜ 1-3

    NASA Astrophysics Data System (ADS)

    Burkert, A.; Förster Schreiber, N. M.; Genzel, R.; Lang, P.; Tacconi, L. J.; Wisnioski, E.; Wuyts, S.; Bandara, K.; Beifiori, A.; Bender, R.; Brammer, G.; Chan, J.; Davies, R.; Dekel, A.; Fabricius, M.; Fossati, M.; Kulkarni, S.; Lutz, D.; Mendel, J. T.; Momcheva, I.; Nelson, E. J.; Naab, T.; Renzini, A.; Saglia, R.; Sharples, R. M.; Sternberg, A.; Wilman, D.; Wuyts, E.

    2016-08-01

    We analyze the angular momenta of massive star-forming galaxies (SFGs) at the peak of the cosmic star formation epoch (z ˜ 0.8-2.6). Our sample of ˜360 log(M */M ⊙) ˜ 9.3-11.8 SFGs is mainly based on the KMOS3D and SINS/zC-SINF surveys of Hα kinematics, and collectively provides a representative subset of the massive star-forming population. The inferred halo scale angular momentum distribution is broadly consistent with that theoretically predicted for their dark matter halos, in terms of mean spin parameter < λ > ˜ 0.037 and its dispersion (σ logλ ˜ 0.2). Spin parameters correlate with the disk radial scale and with their stellar surface density, but do not depend significantly on halo mass, stellar mass, or redshift. Our data thus support the long-standing assumption that on average, even at high redshifts, the specific angular momentum of disk galaxies reflects that of their dark matter halos (j d = j DM). The lack of correlation between λ × (j d /j DM) and the nuclear stellar density Σ*(1 kpc) favors a scenario where disk-internal angular momentum redistribution leads to “compaction” inside massive high-redshift disks. For our sample, the inferred average stellar to dark matter mass ratio is ˜2%, consistent with abundance matching results. Including the molecular gas, the total baryonic disk to dark matter mass ratio is ˜5% for halos near 1012 M ⊙, which corresponds to 31% of the cosmologically available baryons, implying that high-redshift disks are strongly baryon dominated. Based on observations obtained at the Very Large Telescope of the European Southern Observatory, Paranal, Chile (ESO Programme IDs 075.A-0466, 076.A-0527, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 081.B-0568, 081.A-0672, 082.A-0396, 183.A-0781, 087.A-0081, 088.A-0202, 088.A-0209, 091.A-0126, 092.A-0091, 093.A-0079, 094.A-0217, 095.A-0047, 096.A-0025).

  19. Probing Early Galaxy Growth and Dusty Star-Forming Systems Across Diverse Environments in the 28 deg2 Herschel/Stripe82/HETDEX Field

    NASA Astrophysics Data System (ADS)

    Larson, Rebecca; Jogee, Shardha; Watson, Nicholas; Viero, Marco; Weinzirl, Tim; Yorke, Harold W.; Finkelstein, Steven; Papovich, Casey; Casey, Caitlin M.; Ciardullo, Robin; Gronwall, Caryl; LaMassa, Stephanie; Urry, C. Meg

    2015-08-01

    In the next few years, we will embark on an unprecedented study of how a million galaxies grow their stars and dark matter halos over a large a huge comoving volume (0.5 Gpc^3) in the cosmic web at the critical epoch (z~1.9 - 3.5), where cosmic star formation and black hole activity peak, and proto-clusters start to collapse. This study is enabled by the powerful synergy of six photometric and spectroscopic surveys, which are providing Herschel SPIRE, Spitzer IRAC, NEWFIRM K-band, DECam ugriz, and XMM X-ray imaging data, along with optical spectroscopic data from HETDEX over a very large-area (28 sq. deg.) in the Stripe82/HETDEX field. In this poster, we illustrate the power of these combined datasets and focus on studying dusty, star-forming systems (DSFSs) identified with the Herschel Stripe 82 Survey (HerS). Using the 250, 350, and 500 micron SPIRE data over our 28 sq. deg. field, we identify a number of possible high redshift (z > 4) DSFSs which will be prime candidates for follow-up observations. We discuss their properties and possible association with galaxies and quasars detected at X-ray, IR, optical, and UV wavelengths. We present examples of SED fits to DSFSs to constrain their star formation rates, redshifts and dust properties, and discuss broader implications for galaxy growth at early cosmic times. We acknowledge support from NSF grant AST-1413652 andthe JPL/NASA SURP Program.

  20. [O III] emission line as a tracer of star-forming galaxies at high redshifts: comparison between Hα and [O III] emitters at z=2.23 in HiZELS

    NASA Astrophysics Data System (ADS)

    Suzuki, T. L.; Kodama, T.; Sobral, D.; Khostovan, A. A.; Hayashi, M.; Shimakawa, R.; Koyama, Y.; Tadaki, K.-i.; Tanaka, I.; Minowa, Y.; Yamamoto, M.; Smail, I.; Best, P. N.

    2016-10-01

    We investigate the properties of z = 2.23 Hα and [O III] λ5007 emitters using the narrow-band-selected samples obtained from the High-z Emission Line Survey. We construct two samples of the Hα and [O III] emitters and compare their integrated physical properties. We find that the distribution of stellar masses, dust extinction, star formation rates (SFRs), and specific SFRs (sSFRs) is not statistically different between the two samples. When we separate the full galaxy sample into three subsamples according to the detections of the Hα and/or [O III] emission lines, most of the sources detected with both Hα and [O III] show log(sSFRUV) ≳ -9.5. The comparison of the three subsamples suggests that sources with strong [O III] line emission tend to have the highest star-forming activity out all galaxies that we study. We argue that the [O III] emission line can be used as a tracer of star-forming galaxies at high redshift, and that it is especially useful to investigate star-forming galaxies at z > 3, for which Hα emission is no longer observable from the ground.

  1. A HIGHER EFFICIENCY OF CONVERTING GAS TO STARS PUSHES GALAXIES AT z ∼ 1.6 WELL ABOVE THE STAR-FORMING MAIN SEQUENCE

    SciTech Connect

    Silverman, J. D.; Rujopakarn, W.; Daddi, E.; Liu, D.; Sargent, M.; Renzini, A.; Feruglio, C.; Kashino, D.; Sanders, D.; Kartaltepe, J.; Nagao, T.; Arimoto, N.; Berta, S.; Lutz, D.; Béthermin, M.; Koekemoer, A.; and others

    2015-10-20

    Local starbursts have a higher efficiency of converting gas into stars, as compared to typical star-forming galaxies at a given stellar mass, possibly indicative of different modes of star formation. With the peak epoch of galaxy formation occurring at z > 1, it remains to be established whether such an efficient mode of star formation is occurring at high redshift. To address this issue, we measure the molecular gas content of seven high-redshift (z ∼ 1.6) starburst galaxies with the Atacama Large Millimeter/submillimeter Array and IRAM/Plateau de Bure Interferometer. Our targets are selected from the sample of Herschel far-infrared-detected galaxies having star formation rates (∼300–800 M{sub ⊙} yr{sup −1}) elevated (≳4×) above the star-forming main sequence (MS) and included in the FMOS-COSMOS near-infrared spectroscopic survey of star-forming galaxies at z ∼ 1.6 with Subaru. We detect CO emission in all cases at high levels of significance, indicative of high gas fractions (∼30%–50%). Even more compelling, we firmly establish with a clean and systematic selection that starbursts, identified as MS outliers, at high redshift generally have a lower ratio of CO to total infrared luminosity as compared to typical MS star-forming galaxies, although with a smaller offset than expected based on past studies of local starbursts. We put forward a hypothesis that there exists a continuous increase in star formation efficiency with elevation from the MS with galaxy mergers as a possible physical driver. Along with a heightened star formation efficiency, our high-redshift sample is similar in other respects to local starbursts, such as being metal rich and having a higher ionization state of the interstellar medium.

  2. Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Usero, Antonio; Leroy, Adam K.; Walter, Fabian; Schruba, Andreas; García-Burillo, Santiago; Sandstrom, Karin; Bigiel, Frank; Brinks, Elias; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl-Friedrich; de Blok, W. J. G.

    2015-10-01

    We present a new survey of HCN(1–0) emission, a tracer of dense molecular gas, focused on the little-explored regime of normal star-forming galaxy disks. Combining HCN, CO, and infrared (IR) emission, we investigate the role of dense gas in star formation, finding systematic variations in both the apparent dense gas fraction (traced by the HCN-to-CO ratio) and the apparent star formation efficiency of dense gas (traced by the IR-to-HCN ratio). The latter may be unexpected, given the recent popularity of gas density threshold models to explain star formation scaling relations. Our survey used the IRAM 30 m telescope to observe HCN(1–0), CO(1–0), and several other emission lines across 29 nearby disk galaxies whose CO(2–1) emission has previously been mapped by the HERACLES survey. We detected HCN in 48 out of 62 observed positions. Because our observations achieve a typical resolution of ∼1.5 kpc and span a range of galaxies and galactocentric radii (56% lie at {r}{gal}\\gt 1 kpc), we are able to investigate the properties of the dense gas as a function of local conditions in a galaxy disk. We focus on how the ratios IR-to-CO, HCN-to-CO, and IR-to-HCN (observational cognates of the star formation efficiency, dense gas fraction, and dense gas star formation efficiency) depend on the stellar surface density, {{{Σ }}}{star}, and the molecular-to-atomic gas ratio, {{{Σ }}}{mol}/{{{Σ }}}{atom}. The HCN-to-CO ratio is low, often ∼1/30, and correlates tightly with both the molecular-to-atomic ratio and the stellar mass surface density across a range of 2.1 dex (factor of ≈125) in both parameters. Thus for the assumption of fixed CO-to-H2 and HCN-to-dense gas conversion factors, the dense gas fraction depends strongly on location in the disk, being higher in the high surface density, highly molecular parts of galaxies. At the same time, the IR-to-HCN ratio (closely related to the star formation efficiency of dense molecular gas) decreases systematically

  3. New Light in Star-Forming Dwarf Galaxies: The PMAS Integral Field View of the Blue Compact Dwarf Galaxy Mrk 409

    NASA Astrophysics Data System (ADS)

    Cairós, Luz M.; Caon, Nicola; Papaderos, Polychronis; Kehrig, Carolina; Weilbacher, Peter; Roth, Martin M.; Zurita, Cristina

    2009-12-01

    We present an integral field spectroscopic study of the central 2 × 2 kpc2 of the blue compact dwarf galaxy Mrk 409, observed with the Potsdam MultiAperture Spectrophotometer (PMAS). This study focuses on the morphology, two-dimensional chemical abundance pattern, excitation properties, and kinematics of the ionized interstellar medium in the starburst component. We also investigate the nature of the extended ring of ionized gas emission surrounding the bright nuclear starburst region of Mrk 409. PMAS spectra of selected regions along the ring, interpreted with evolutionary and population synthesis models, indicate that their ionized emission is mainly due to a young stellar population with a total mass of ~1.5 × 106 M sun, which started forming almost coevally ~10 Myr ago. This stellar component is likely confined to the collisional interface of a spherically expanding, starburst-driven super-bubble with denser, swept-up ambient gas, ~600 pc away from the central starburst nucleus. The spectroscopic properties of the latter imply a large extinction (CHβ>0.9), and the presence of an additional non-thermal ionization source, most likely a low-luminosity active galactic nucleus. Mrk 409 shows a relatively large oxygen abundance (12 + log(O/H) ~ 8.4) and no chemical abundance gradients out to R ~ 600 pc. The ionized gas kinematics displays an overall regular rotation on a northwest-southeast axis, with a maximum velocity of 60 km s-1 the total mass inside the star-forming ring is about 1.4 × 109 M sun. Based on observations obtained at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy.

  4. PHIBSS: MOLECULAR GAS, EXTINCTION, STAR FORMATION, AND KINEMATICS IN THE z = 1.5 STAR-FORMING GALAXY EGS13011166

    SciTech Connect

    Genzel, R.; Tacconi, L. J.; Kurk, J.; Wuyts, S.; Foerster Schreiber, N. M.; Gracia-Carpio, J.; Combes, F.; Freundlich, J.; Bolatto, A.; Cooper, M. C.; Neri, R.; Nordon, R.; Bournaud, F.; Comerford, J.; Cox, P.; Davis, M.; Garcia-Burillo, S.; Naab, T.; Lutz, D. E-mail: linda@mpe.mpg.de; and others

    2013-08-10

    We report matched resolution imaging spectroscopy of the CO 3-2 line (with the IRAM Plateau de Bure millimeter interferometer) and of the H{alpha} line (with LUCI at the Large Binocular Telescope) in the massive z = 1.53 main-sequence galaxy EGS 13011166, as part of the ''Plateau de Bure high-z, blue-sequence survey'' (PHIBSS: Tacconi et al.). We combine these data with Hubble Space Telescope V-I-J-H-band maps to derive spatially resolved distributions of stellar surface density, star formation rate, molecular gas surface density, optical extinction, and gas kinematics. The spatial distribution and kinematics of the ionized and molecular gas are remarkably similar and are well modeled by a turbulent, globally Toomre unstable, rotating disk. The stellar surface density distribution is smoother than the clumpy rest-frame UV/optical light distribution and peaks in an obscured, star-forming massive bulge near the dynamical center. The molecular gas surface density and the effective optical screen extinction track each other and are well modeled by a ''mixed'' extinction model. The inferred slope of the spatially resolved molecular gas to star formation rate relation, N = dlog{Sigma}{sub starform}/dlog{Sigma}{sub molgas}, depends strongly on the adopted extinction model, and can vary from 0.8 to 1.7. For the preferred mixed dust-gas model, we find N = 1.14 {+-} 0.1.

  5. Herschel extreme lensing line observations: Dynamics of two strongly lensed star-forming galaxies near redshift z = 2

    SciTech Connect

    Rhoads, James E.; Malhotra, Sangeeta; Allam, Sahar; Carilli, Chris; Combes, Françoise; Finkelstein, Keely; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; Guillard, Pierre; Nesvadba, Nicole; Rigby, Jane; Spaans, Marco; Strauss, Michael A.

    2014-05-20

    We report on two regularly rotating galaxies at redshift z ≈ 2, using high-resolution spectra of the bright [C II] 158 μm emission line from the HIFI instrument on the Herschel Space Observatory. Both SDSS090122.37+181432.3 ({sup S}0901{sup )} and SDSSJ120602.09+514229.5 ({sup t}he Clone{sup )} are strongly lensed and show the double-horned line profile that is typical of rotating gas disks. Using a parametric disk model to fit the emission line profiles, we find that S0901 has a rotation speed of vsin (i) ≈ 120 ± 7 km s{sup –1} and a gas velocity dispersion of σ {sub g} < 23 km s{sup –1} (1σ). The best-fitting model for the Clone is a rotationally supported disk having vsin (i) ≈ 79 ± 11 km s{sup –1} and σ {sub g} ≲ 4 km s{sup –1} (1σ). However, the Clone is also consistent with a family of dispersion-dominated models having σ {sub g} = 92 ± 20 km s{sup –1}. Our results showcase the potential of the [C II] line as a kinematic probe of high-redshift galaxy dynamics: [C II] is bright, accessible to heterodyne receivers with exquisite velocity resolution, and traces dense star-forming interstellar gas. Future [C II] line observations with ALMA would offer the further advantage of spatial resolution, allowing a clearer separation between rotation and velocity dispersion.

  6. Herschel Extreme Lensing Line Observations: Dynamics of Two Strongly Lensed Star-forming Galaxies near Redshift z = 2

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Malhotra, Sangeeta; Allam, Sahar; Carilli, Chris; Combes, Françoise; Finkelstein, Keely; Finkelstein, Steven; Frye, Brenda; Gerin, Maryvonne; Guillard, Pierre; Nesvadba, Nicole; Rigby, Jane; Spaans, Marco; Strauss, Michael A.

    2014-05-01

    We report on two regularly rotating galaxies at redshift z ≈ 2, using high-resolution spectra of the bright [C II] 158 μm emission line from the HIFI instrument on the Herschel Space Observatory. Both SDSS090122.37+181432.3 ("S0901") and SDSSJ120602.09+514229.5 ("the Clone") are strongly lensed and show the double-horned line profile that is typical of rotating gas disks. Using a parametric disk model to fit the emission line profiles, we find that S0901 has a rotation speed of vsin (i) ≈ 120 ± 7 km s-1 and a gas velocity dispersion of σ g < 23 km s-1 (1σ). The best-fitting model for the Clone is a rotationally supported disk having vsin (i) ≈ 79 ± 11 km s-1 and σ g <~ 4 km s-1 (1σ). However, the Clone is also consistent with a family of dispersion-dominated models having σ g = 92 ± 20 km s-1. Our results showcase the potential of the [C II] line as a kinematic probe of high-redshift galaxy dynamics: [C II] is bright, accessible to heterodyne receivers with exquisite velocity resolution, and traces dense star-forming interstellar gas. Future [C II] line observations with ALMA would offer the further advantage of spatial resolution, allowing a clearer separation between rotation and velocity dispersion. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  7. Linking the X-ray and infrared properties of star-forming galaxies at z < 1.5

    NASA Astrophysics Data System (ADS)

    Symeonidis, M.; Georgakakis, A.; Page, M. J.; Bock, J.; Bonzini, M.; Buat, V.; Farrah, D.; Franceschini, A.; Ibar, E.; Lutz, D.; Magnelli, B.; Magdis, G.; Oliver, S. J.; Pannella, M.; Paolillo, M.; Rosario, D.; Roseboom, I. G.; Vaccari, M.; Villforth, C.

    2014-10-01

    We present the most complete study to date of the X-ray emission from star formation in high-redshift (median z = 0.7; z < 1.5), IR-luminous (LIR = 1010-1013 L⊙) galaxies detected by Herschel's PACS and SPIRE instruments. For our purpose, we take advantage of the deepest X-ray data to date, the Chandra Deep Fields (North and South). Sources which host AGN are removed from our analysis by means of multiple AGN indicators. We find an AGN fraction of 18 ± 2 per cent amongst our sample and note that AGN entirely dominate at values of log [LX/LIR] > -3 in both hard and soft X-ray bands. From the sources which are star formation dominated, only a small fraction are individually X-ray detected and for the bulk of the sample we calculate average X-ray luminosities through stacking. We find an average soft X-ray to infrared ratio of log = -4.3 and an average hard X-ray to infrared ratio of log = -3.8. We report that the X-ray/IR correlation is approximately linear through the entire range of LIR and z probed and, although broadly consistent with the local (z < 0.1) one, it does display some discrepancies. We suggest that these discrepancies are unlikely to be physical, i.e. due to an intrinsic change in the X-ray properties of star-forming galaxies with cosmic time, as there is no significant evidence for evolution of the LX/LIR ratio with redshift. Instead, they are possibly due to selection effects and remaining AGN contamination. We also examine whether dust obscuration in the galaxy plays a role in attenuating X-rays from star formation, by investigating changes in the LX/LIR ratio as a function of the average dust temperature. We conclude that X-rays do not suffer any measurable attenuation in the host galaxy.

  8. Star-forming galaxies in low-redshift clusters: comparison of integrated properties of cluster and field galaxies

    NASA Astrophysics Data System (ADS)

    Bretherton, C. F.; James, P. A.; Moss, C.; Whittle, M.

    2010-12-01

    Aims: We investigate the effect of the cluster environment on the star formation properties of galaxies in 8 nearby Abell clusters. Methods: Star formation properties are determined for individual galaxies using the equivalent width of Hα+[Nii] line emission from narrow-band imaging. Equivalent width distributions are derived for each galaxy type in each of 3 environments - cluster, supercluster (outside the cluster virial radius) and field. The effects of morphological disturbance on star formation are also investigated. Results: We identify a population of early-type disk galaxies in the cluster population with enhanced star formation compared to their field counterparts. The enhanced cluster galaxies frequently show evidence of disturbance, and the disturbed galaxies show marginal evidence for a higher velocity dispersion, possibly indicative of an infalling population. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias; and with the Jacobus Kapteyn Telescope, which was operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  9. THE EVOLUTION OF THE STELLAR MASS FUNCTIONS OF STAR-FORMING AND QUIESCENT GALAXIES TO z = 4 FROM THE COSMOS/UltraVISTA SURVEY

    SciTech Connect

    Muzzin, Adam; Franx, Marijn; Labbé, Ivo; Marchesini, Danilo; Stefanon, Mauro; McCracken, Henry J.; Milvang-Jensen, Bo; Fynbo, J. P. U.; Dunlop, James S.; Brammer, Gabriel; Van Dokkum, Pieter G.

    2013-11-01

    We present measurements of the stellar mass functions (SMFs) of star-forming and quiescent galaxies to z = 4 using a sample of 95,675 K{sub s} -selected galaxies in the COSMOS/UltraVISTA field. The SMFs of the combined population are in good agreement with previous measurements and show that the stellar mass density of the universe was only 50%, 10%, and 1% of its current value at z ∼ 0.75, 2.0, and 3.5, respectively. The quiescent population drives most of the overall growth, with the stellar mass density of these galaxies increasing as ρ{sub star}∝(1 + z){sup –4.7±0.4} since z = 3.5, whereas the mass density of star-forming galaxies increases as ρ{sub star}∝(1 + z){sup –2.3±0.2}. At z > 2.5, star-forming galaxies dominate the total SMF at all stellar masses, although a non-zero population of quiescent galaxies persists to z = 4. Comparisons of the K{sub s} -selected star-forming galaxy SMFs with UV-selected SMFs at 2.5 < z < 4 show reasonable agreement and suggest that UV-selected samples are representative of the majority of the stellar mass density at z > 3.5. We estimate the average mass growth of individual galaxies by selecting galaxies at fixed cumulative number density. The average galaxy with log(M{sub star}/M{sub ☉}) = 11.5 at z = 0.3 has grown in mass by only 0.2 dex (0.3 dex) since z = 2.0 (3.5), whereas those with log(M{sub star}/M{sub ☉}) = 10.5 have grown by >1.0 dex since z = 2. At z < 2, the time derivatives of the mass growth are always larger for lower-mass galaxies, which demonstrates that the mass growth in galaxies since that redshift is mass-dependent and primarily bottom-up. Lastly, we examine potential sources of systematic uncertainties in the SMFs and find that those from photo-z templates, stellar population synthesis modeling, and the definition of quiescent galaxies dominate the total error budget in the SMFs.

  10. THE UVJ SELECTION OF QUIESCENT AND STAR-FORMING GALAXIES: SEPARATING EARLY- AND LATE-TYPE GALAXIES AND ISOLATING EDGE-ON SPIRALS

    SciTech Connect

    Patel, Shannon G.; Franx, Marijn; Holden, Bradford P.; Illingworth, Garth D.; Van der Wel, Arjen

    2012-04-01

    We utilize for the first time Hubble Space Telescope Advanced Camera for Surveys imaging to examine the structural properties of galaxies in the rest-frame U - V versus V - J diagram (i.e., the UVJ diagram) using a sample at 0.6 < z < 0.9 that reaches a low stellar mass limit (log M/M{sub Sun} >10.25). The use of the UVJ diagram as a tool to distinguish quiescent galaxies from star-forming galaxies (SFGs) is becoming more common due to its ability to separate red quiescent galaxies from reddened SFGs. Quiescent galaxies occupy a small and distinct region of UVJ color space and we find most of them to have concentrated profiles with high Sersic indices (n > 2.5) and smooth structure characteristic of early-type systems. SFGs populate a broad but well-defined sequence of UVJ colors and are comprised of objects with a mix of Sersic indices. Interestingly, most UVJ-selected SFGs with high Sersic indices also display structure due to dust and star formation typical of the n < 2.5 SFGs and late-type systems. Finally, we find that the position of an SFG on the sequence of UVJ colors is determined to a large degree by the mass of the galaxy and its inclination. Systems that are closer to edge-on generally display redder colors and lower [O II]{lambda}3727 luminosity per unit mass as a consequence of the reddening due to dust within the disks. We conclude that the two main features seen in UVJ color space correspond closely to the traditional morphological classes of early- and late-type galaxies.

  11. SPECTROSCOPIC PROPERTIES OF STAR-FORMING HOST GALAXIES AND TYPE Ia SUPERNOVA HUBBLE RESIDUALS IN A NEARLY UNBIASED SAMPLE

    SciTech Connect

    D'Andrea, Chris B.; Gupta, Ravi R.; Sako, Masao; Morris, Matt; Nichol, Robert C.; Campbell, Heather; Lampeitl, Hubert; Brown, Peter J.; Olmstead, Matthew D.; Frieman, Joshua A.; Kessler, Richard; Garnavich, Peter; Jha, Saurabh W.; Marriner, John; Schneider, Donald P.; Smith, Mathew

    2011-12-20

    We examine the correlation between supernova (SN) host-galaxy properties and their residuals in the Hubble diagram. We use SNe discovered during the Sloan Digital Sky Survey-II Supernova Survey, and focus on objects at a redshift of z < 0.15, where the selection effects of the survey are known to yield a complete Type Ia supernova (SN Ia) sample. To minimize the bias in our analysis with respect to measured host-galaxy properties, spectra were obtained for nearly all hosts, spanning a range in magnitude of -23 < M{sub r} < -17. In contrast to previous works that use photometric estimates of host mass as a proxy for global metallicity, we analyze host-galaxy spectra to obtain gas-phase metallicities and star formation rates (SFRs) from host galaxies with active star formation. From a final sample of {approx}40 emission-line galaxies, we find that light-curve-corrected SNe Ia are {approx}0.1 mag brighter in high-metallicity hosts than in low-metallicity hosts. We also find a significant (>3{sigma}) correlation between the Hubble Residuals of SNe Ia and the specific SFR of the host galaxy. We comment on the importance of SN/host-galaxy correlations as a source of systematic bias in future deep SN surveys.

  12. Spectroscopic Properties of Star-Forming Host Galaxies and Type Ia Supernova Hubble Residuals in a Nearly Unbiased Sample

    SciTech Connect

    D'Andrea, Chris B.; et al.

    2011-12-20

    We examine the correlation between supernova host galaxy properties and their residuals on the Hubble diagram. We use supernovae discovered during the Sloan Digital Sky Survey II - Supernova Survey, and focus on objects at a redshift of z < 0.15, where the selection effects of the survey are known to yield a complete Type Ia supernova sample. To minimize the bias in our analysis with respect to measured host-galaxy properties, spectra were obtained for nearly all hosts, spanning a range in magnitude of -23 < M_r < -17. In contrast to previous works that use photometric estimates of host mass as a proxy for global metallicity, we analyze host-galaxy spectra to obtain gas-phase metallicities and star-formation rates from host galaxies with active star formation. From a final sample of ~ 40 emission-line galaxies, we find that light-curve corrected Type Ia supernovae are ~ 0.1 magnitudes brighter in high-metallicity hosts than in low-metallicity hosts. We also find a significant (> 3{\\sigma}) correlation between the Hubble residuals of Type Ia supernovae and the specific star-formation rate of the host galaxy. We comment on the importance of supernova/host-galaxy correlations as a source of systematic bias in future deep supernova surveys.

  13. Molecular gas content in strongly lensed z ~ 1.5-3 star-forming galaxies with low infrared luminosities

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, M.; Zamojski, M.; Schaerer, D.; Combes, F.; Egami, E.; Swinbank, A. M.; Richard, J.; Sklias, P.; Rawle, T. D.; Rex, M.; Kneib, J.-P.; Boone, F.; Blain, A.

    2015-05-01

    To extend the molecular gas measurements to more typical star-forming galaxies (SFGs) with star formation rates SFR< 40 M⊙ yr-1 and stellar masses M∗< 2.5 × 1010M⊙ at z ~ 1.5-3, we have observed CO emission with the IRAM Plateau de Bure Interferometer and the IRAM 30 m telescope for five strongly lensed galaxies, selected from the Herschel Lensing Survey. These observations are combined with a compilation of CO measurements from the literature. From this, we infer the CO luminosity correction factors r2,1 = 0.81 ± 0.20 and r3,1 = 0.57 ± 0.15 for the J = 2 and J = 3 CO transitions, respectively, valid for SFGs at z> 1. The combined sample of CO-detected SFGs at z> 1 shows a large spread in star formation efficiency (SFE) with a dispersion of 0.33 dex, such that the SFE extends well beyond the low values of local spirals and overlaps the distribution of z> 1 submm galaxies. We find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to the variations of several physical parameters, primarily the specific star formation rate, and also stellar mass and redshift. The dependence of SFE on the offset from the main sequence and the compactness of the starburst is less clear. The possible increase of the molecular gas depletion timescale with stellar mass, now revealed by low M∗ SFGs at z> 1 and also observed at z = 0, contrasts with the generally acknowledged constant molecular gas depletion timescale and refutes the linearity of the Kennicutt-Schmidt relation. A net rise of the molecular gas fraction (fgas) is observed from z ~ 0.2 to z ~ 1.2, followed by a very mild increase toward higher redshifts, as found in earlier studies. At each redshift the molecular gas fraction shows a large dispersion, mainly due to the dependence of fgas on stellar mass, producing a gradient of increasing fgas with decreasing M∗. We provide the first measurement of the molecular gas fraction of z> 1 SFGs at the low-M∗ end between 109.4

  14. THE SINS SURVEY OF z {approx} 2 GALAXY KINEMATICS: PROPERTIES OF THE GIANT STAR-FORMING CLUMPS

    SciTech Connect

    Genzel, R.; Foerster Schreiber, N. M.; Genel, S.; Tacconi, L. J.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Kurk, J.; Newman, S.; Jones, T.; Shapiro, K.; Lilly, S. J.; Carollo, C. M.; Renzini, A.; Bouche, N.; Burkert, A.; Cresci, G.; Ceverino, D.; Dekel, A.; Hicks, E.

    2011-06-01

    We have studied the properties of giant star-forming clumps in five z {approx} 2 star-forming disks with deep SINFONI AO spectroscopy at the ESO VLT. The clumps reside in disk regions where the Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad H{alpha}/[N II] line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. The most active clumps may lose much of their mass and disrupt in the disk. The clumps leave a modest imprint on the gas kinematics. Velocity gradients across the clumps are 10-40 km s{sup -1} kpc{sup -1}, similar to the galactic rotation gradients. Given beam smearing and clump sizes, these gradients may be consistent with significant rotational support in typical clumps. Extreme clumps may not be rotationally supported; either they are not virialized or they are predominantly pressure supported. The velocity dispersion is spatially rather constant and increases only weakly with star formation surface density. The large velocity dispersions may be driven by the release of gravitational energy, either at the outer disk/accreting streams interface, and/or by the clump migration within the disk. Spatial variations in the inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps.

  15. A Keck Adaptive Optics Survey of a Representative Sample of Gravitationally Lensed Star-forming Galaxies: High Spatial Resolution Studies of Kinematics and Metallicity Gradients

    NASA Astrophysics Data System (ADS)

    Leethochawalit, Nicha; Jones, Tucker A.; Ellis, Richard S.; Stark, Daniel P.; Richard, Johan; Zitrin, Adi; Auger, Matthew

    2016-04-01

    We discuss spatially resolved emission line spectroscopy secured for a total sample of 15 gravitationally lensed star-forming galaxies at a mean redshift of z≃ 2 based on Keck laser-assisted adaptive optics observations undertaken with the recently improved OSIRIS integral field unit (IFU) spectrograph. By exploiting gravitationally lensed sources drawn primarily from the CASSOWARY survey, we sample these sub-L{}* galaxies with source-plane resolutions of a few hundred parsecs ensuring well-sampled 2D velocity data and resolved variations in the gas-phase metallicity. Such high spatial resolution data offer a critical check on the structural properties of larger samples derived with coarser sampling using multiple-IFU instruments. We demonstrate how kinematic complexities essential to understanding the maturity of an early star-forming galaxy can often only be revealed with better sampled data. Although we include four sources from our earlier work, the present study provides a more representative sample unbiased with respect to emission line strength. Contrary to earlier suggestions, our data indicate a more diverse range of kinematic and metal gradient behavior inconsistent with a simple picture of well-ordered rotation developing concurrently with established steep metal gradients in all but merging systems. Comparing our observations with the predictions of hydrodynamical simulations suggests that gas and metals have been mixed by outflows or other strong feedback processes, flattening the metal gradients in early star-forming galaxies.

  16. The Star-forming Histories of the Nucleus, Bulge, and Inner Disk of NGC 5102: Clues to the Evolution of a Nearby Lenticular Galaxy

    NASA Astrophysics Data System (ADS)

    Davidge, T. J.

    2015-01-01

    Long slit spectra recorded with the Gemini Multi-Object Spectrograph on Gemini South are used to examine the star-forming history (SFH) of the lenticular galaxy NGC 5102. Structural and supplemental photometric information are obtained from archival Spitzer [3.6] images. Absorption features at blue and visible wavelengths are traced out along the minor axis to galactocentric radii ~60 arcsec (~0.9 kpc), sampling the nucleus, bulge, and disk components. Comparisons with model spectra point to luminosity-weighted metallicities that are consistent with the colors of resolved red giant branch stars in the disk. The nucleus has a luminosity-weighted age at visible wavelengths of {˜ } 1+0.2-0.1 Gyr, and the integrated light is dominated by stars that formed over a time period of only a few hundred Myr. For comparison, the luminosity-weighted ages of the bulge and disk are {˜ } 2+0.5-0.2 Gyr and 10+2-2 Gyr, respectively. The g' - [3.6] colors of the nucleus and bulge are consistent with the spectroscopically based ages. In contrast to the nucleus, models that assume star-forming activity spanning many Gyr provide a better match to the spectra of the bulge and disk than simple stellar population models. Isophotes in the bulge have a disky shape, hinting that the bulge was assembled from material with significant rotational support. The SFHs of the bulge and disk are consistent with the bulge forming from the collapse of a long-lived bar, rather than from the collapse of a transient structure that formed as the result of a tidal interaction. It is thus suggested that the progenitor of NGC 5102 was a barred disk galaxy that morphed into a lenticular galaxy through the buckling of its bar. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  17. Applications of high-frequency resolution, wide-field VLBI: observations of nearby star-forming galaxies & habitable exoplanetary candidates

    NASA Astrophysics Data System (ADS)

    Rampadarath, Hayden

    2014-04-01

    Until recently, the maximum observable field of view of Very Long Baseline Interferometric (VLBI) observations was limited, predominantly, by the ability to process large volumes of data. However, the availability of software correlators and high performance computing have provided the means to overcome these restrictions, giving rise to the technique of wide-field VLBI. This thesis reports on the application of this technique to investigate two different science cases: (1) to explore the use of VLBI for targeted searches for extra-terrestrial intelligence (SETI); (2) to investigate the compact radio source populations, supernovae, and star formation rates and the interstellar media of nearby star-forming galaxies. Radio sources detected with VLBI will display characteristic variations as a function of time and frequency that are dependent on their locations with respect to the observing phase centre. Thus, a planet with a radio emitting civilisation, bright enough to be detected, can be identified and separated from human generated signals through VLBI observations. This idea was tested on a VLBI observation of the planetary system Gliese 581. The dataset was searched for candidate SETI signals, in both time and frequency, with amplitudes greater than five times the baseline sensitivity on all baselines. Candidate signals were selected and through the use of automated, statistical data analysis techniques were ruled out as originating from the Gliese 581 system. The results of this study place an upper limit of 7 MW/Hz on the power output of any isotropic emitter located in the Gliese 581 system, within this frequency range. While the study was unable to identify any signals originating from Gliese 581, the techniques presented are applicable to the next-generation interferometers, such as the long baselines of the Square Kilometre Array.

  18. A survey of the cold molecular gas in gravitationally lensed star-forming galaxies at z > 2

    NASA Astrophysics Data System (ADS)

    Aravena, M.; Spilker, J. S.; Bethermin, M.; Bothwell, M.; Chapman, S. C.; de Breuck, C.; Furstenau, R. M.; Gónzalez-López, J.; Greve, T. R.; Litke, K.; Ma, J.; Malkan, M.; Marrone, D. P.; Murphy, E. J.; Stark, A.; Strandet, M.; Vieira, J. D.; Weiss, A.; Welikala, N.; Wong, G. F.; Collier, J. D.

    2016-04-01

    Using the Australia Telescope Compact Array, we conducted a survey of CO J = 1 - 0 and J = 2 - 1 line emission towards strongly lensed high-redshift dusty star-forming galaxies (DSFGs) previously discovered with the South Pole Telescope (SPT). Our sample comprises 17 sources that had CO-based spectroscopic redshifts obtained with the Atacama Large Millimeter/submillimeter Array and the Atacama Pathfinder Experiment. We detect all sources with known redshifts in either CO J = 1 - 0 or J = 2 - 1. 12 sources are detected in the 7-mm continuum. The derived CO luminosities imply gas masses in the range (0.5-11) × 1010 M⊙ and gas depletion time-scales tdep < 200 Myr, using a CO to gas mass conversion factor αCO = 0.8 M⊙ (K km s-1 pc2)-1. Combining the CO luminosities and dust masses, along with a fixed gas-to-dust ratio, we derive αCO factors in the range 0.4-1.8 M⊙ (K km s-1 pc2)-1, similar to what is found in other starbursting systems. We find small scatter in αCO values within the sample, even though inherent variations in the spatial distribution of dust and gas in individual cases could bias the dust-based αCO estimates. We find that lensing magnification factors based on the CO linewidth to luminosity relation (μCO) are highly unreliable, but particularly when μ < 5. Finally, comparison of the gas and dynamical masses suggest that the average molecular gas fraction stays relatively constant at z = 2-5 in the SPT DSFG sample.

  19. The growth of typical star-forming galaxies and their super massive black holes across cosmic time since z ˜ 2

    NASA Astrophysics Data System (ADS)

    Calhau, João; Sobral, David; Stroe, Andra; Best, Philip; Smail, Ian; Lehmer, Bret; Harrison, Chris; Thomson, Alasdair

    2016-09-01

    Understanding galaxy formation and evolution requires studying the interplay between the growth of galaxies and the growth of their black holes across cosmic time. Here we explore a sample of Hα-selected star-forming galaxies from the HiZELS survey and use the wealth of multi-wavelength data in the COSMOS field (X-rays, far-infrared and radio) to study the relative growth rates between typical galaxies and their central supermassive black holes, from z = 2.23 to z = 0. Typical star-forming galaxies at z ˜ 1 - 2 have black hole accretion rates (dot{M}_BH) of 0.001-0.01M⊙ yr-1 and star formation rates (SFRs) of ˜10-40 M⊙ yr-1, and thus grow their stellar mass much quicker than their black hole mass (3.3±0.2 orders of magnitude faster). However, ˜3% of the sample (the sources detected directly in the X-rays) show a significantly quicker growth of the black hole mass (up to 1.5 orders of magnitude quicker growth than the typical sources). dot{M}_BH falls from z = 2.23 to z = 0, with the decline resembling that of star formation rate density or the typical SFR (SFR★). We find that the average black hole to galaxy growth (dot{M}_BH/SFR) is approximately constant for star-forming galaxies in the last 11 Gyrs. The relatively constant dot{M}_BH/SFR suggests that these two quantities evolve equivalently through cosmic time and with practically no delay between the two.

  20. Cosmic Reionization and Early Star-forming Galaxies: A Joint Analysis of New Constraints from Planck and the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Robertson, Brant E.; Ellis, Richard S.; Furlanetto, Steven R.; Dunlop, James S.

    2015-04-01

    We discuss new constraints on the epoch of cosmic reionization and test the assumption that most of the ionizing photons responsible arose from high-redshift star-forming galaxies. Good progress has been made in charting the end of reionization through spectroscopic studies of z ≃ 6-8 QSOs, gamma-ray bursts, and galaxies expected to host Lyα emission. However, the most stringent constraints on its duration have come from the integrated optical depth, τ, of Thomson scattering to the cosmic microwave background. Using the latest data on the abundance and luminosity distribution of distant galaxies from Hubble Space Telescope imaging, we simultaneously match the reduced value τ =0.066+/- 0.012 recently reported by the Planck collaboration and the evolving neutrality of the intergalactic medium with a reionization history within 6≲ z≲ 10, thereby reducing the requirement for a significant population of very high redshift (z\\gg 10) galaxies. Our analysis strengthens the conclusion that star-forming galaxies dominated the reionization process and has important implications for upcoming 21 cm experiments and searches for early galaxies with the James Webb Space Telescope.

  1. Keck-I MOSFIRE spectroscopy of compact star-forming galaxies at z ≳ 2: high velocity dispersions in progenitors of compact quiescent galaxies

    SciTech Connect

    Barro, Guillermo; Koo, David C.; Faber, Sandra M.; Guo, Yicheng; Toloba, Elisa; Fang, Jerome J.; Trump, Jonathan R.; Dekel, Avishai; Kassin, Susan A.; Koekemoer, Anton M.; Kocevski, Dale D.; Van der Wel, Arjen; Pérez-González, Pablo G.; Pacifici, Camilla; Simons, Raymond; Campbell, Randy D.; Goodrich, Bob; Kassis, Marc; Ceverino, Daniel; Finkelstein, Steven L.; and others

    2014-11-10

    We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift 2 ≤ z ≤ 2.5 with star formation rates of SFR ∼ 100 M {sub ☉} yr{sup –1} and masses of log(M/M {sub ☉}) ∼10.8. Their high integrated gas velocity dispersions of σ{sub int} =230{sub −30}{sup +40} km s{sup –1}, as measured from emission lines of Hα and [O III], and the resultant M {sub *}-σ{sub int} relation and M {sub *}-M {sub dyn} all match well to those of compact quiescent galaxies at z ∼ 2, as measured from stellar absorption lines. Since log(M {sub *}/M {sub dyn}) =–0.06 ± 0.2 dex, these compact SFGs appear to be dynamically relaxed and evolved, i.e., depleted in gas and dark matter (<13{sub −13}{sup +17}%), and present larger σ{sub int} than their non-compact SFG counterparts at the same epoch. Without infusion of external gas, depletion timescales are short, less than ∼300 Myr. This discovery adds another link to our new dynamical chain of evidence that compact SFGs at z ≳ 2 are already losing gas to become the immediate progenitors of compact quiescent galaxies by z ∼ 2.

  2. Rest-frame UV-Optically Selected Galaxies at 2.3 <~ z <~ 3.5: Searching for Dusty Star-forming and Passively Evolving Galaxies

    NASA Astrophysics Data System (ADS)

    Guo, Yicheng; Giavalisco, Mauro; Cassata, Paolo; Ferguson, Henry C.; Williams, Christina C.; Dickinson, Mark; Koekemoer, Anton; Grogin, Norman A.; Chary, Ranga-Ram; Messias, Hugo; Tundo, Elena; Lin, Lihwai; Lee, Seong-Kook; Salimbeni, Sara; Fontana, Adriano; Grazian, Andrea; Kocevski, Dale; Lee, Kyoung-Soo; Villanueva, Edward; van der Wel, Arjen

    2012-04-01

    A new set of color selection criteria (VJL) analogous with the BzK method is designed to select both star-forming galaxies (SFGs) and passively evolving galaxies (PEGs) at 2.3 <~ z <~ 3.5 by using rest-frame UV-optical (V - J versus J - L) colors. The criteria are thoroughly tested with theoretical stellar population synthesis models and real galaxies with spectroscopic redshifts to evaluate their efficiency and contamination. We apply the well-tested VJL criteria to the HST/WFC3 Early Release Science field and study the physical properties of selected galaxies. The redshift distribution of selected SFGs peaks at z ~ 2.7, slightly lower than that of Lyman break galaxies at z ~ 3. Comparing the observed mid-infrared fluxes of selected galaxies with the prediction of pure stellar emission, we find that our VJL method is effective at selecting massive dusty SFGs that are missed by the Lyman break technique. About half of the star formation in massive (M star > 1010 M ⊙) galaxies at 2.3 <~ z <~ 3.5 is contributed by dusty (extinction E(B - V) > 0.4) SFGs, which, however, only account for ~20% of the number density of massive SFGs. We also use the mid-infrared fluxes to clean our PEG sample and find that galaxy size can be used as a secondary criterion to effectively eliminate the contamination of dusty SFGs. The redshift distribution of the cleaned PEG sample peaks at z ~ 2.5. We find six PEG candidates at z > 3 and discuss possible methods to distinguish them from dusty contamination. We conclude that at least part of our candidates are real PEGs at z ~ 3, implying that these types of galaxies began to form their stars at z >~ 5. We measure the integrated stellar mass density (ISMD) of PEGs at z ~ 2.5 and set constraints on it at z > 3. We find that the ISMD grows by at least about a factor of 10 in 1 Gyr at 3 < z <5 and by another factor of 10 in the next 3.5 Gyr (1 < z < 3).

  3. NGC 3801 caught in the act: a post-merger star-forming early-type galaxy with AGN-jet feedback

    NASA Astrophysics Data System (ADS)

    Hota, Ananda; Rey, Soo-Chang; Kang, Yongbeom; Kim, Suk; Matsushita, Satoki; Chung, Jiwon

    2012-05-01

    In the current models of galaxy formation and evolution, AGN feedback is crucial to reproduce galaxy luminosity function, colour-magnitude relation and M•-σ relation. However, whether AGN feedback can indeed expel and heat up significant amount of cool molecular gas and consequently quench star formation is yet to be demonstrated observationally. Only in four cases so far (Cen A, NGC 3801, NGC 6764 and Mrk 6), X-ray observations have found evidences of jet-driven shocks heating the ISM. We chose the least explored galaxy NGC 3801, and present the first ultraviolet imaging and stellar population analysis of this galaxy from GALEX data. We find this merger-remnant early-type galaxy to have an intriguing spiral wisp of young star-forming regions (age ranging from 100 to 500 Myr). Taking clues from dust/PAH, H I and CO emission images, we interpret NGC 3801 to have a kinematically decoupled core or an extremely warped gas disc. From the HST data, we also show evidence of ionized gas outflow similar to that observed in H I and molecular gas (CO) data, which may have caused the decline of star formation leading to the red optical colour of the galaxy. However, from these panchromatic data, we interpret that the expanding shock shells from the young (˜2.4 Myr) radio jets are yet to reach the outer gaseous regions of the galaxy. It seems we observe this galaxy at a rare stage of its evolutionary sequence where post-merger star formation has already declined and new powerful jet feedback is about to affect the gaseous star-forming outer disc within the next 10 Myr, to further transform it into a red-and-dead early-type galaxy.

  4. Direct measurements of dust attenuation in z ∼ 1.5 star-forming galaxies from 3D-HST: Implications for dust geometry and star formation rates

    SciTech Connect

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B.; Conroy, Charlie; Schreiber, Natascha M. Förster; Wuyts, Stijn; Franx, Marijn; Fumagalli, Mattia; Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Van Dokkum, Pieter G.; Skelton, Rosalind E.; Whitaker, Katherine E.

    2014-06-10

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust around star-forming regions (A {sub V,} {sub H} {sub II}) and the integrated dust content (A {sub V,} {sub star}). We select a sample of 163 galaxies between 1.36 ≤ z ≤ 1.5 with Hα signal-to-noise ratio ≥5 and measure Balmer decrements from stacked spectra to calculate A {sub V,} {sub H} {sub II}. First, we stack spectra in bins of A {sub V,} {sub star}, and find that A {sub V,} {sub H} {sub II} = 1.86 A {sub V,} {sub star}, with a significance of σ = 1.7. Our result is consistent with the two-component dust model, in which galaxies contain both diffuse and stellar birth cloud dust. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M {sub *}). We find that on average A {sub V,} {sub H} {sub II} increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-component model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive dust-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.

  5. Caught in the Act: Gas and Stellar Velocity Dispersions in a Fast Quenching Compact Star-Forming Galaxy at z~1.7

    NASA Astrophysics Data System (ADS)

    Barro, Guillermo; Faber, Sandra M.; Dekel, Avishai; Pacifici, Camilla; Pérez-González, Pablo G.; Toloba, Elisa; Koo, David C.; Trump, Jonathan R.; Inoue, Shigeki; Guo, Yicheng; Liu, Fengshan; Primack, Joel R.; Koekemoer, Anton M.; Brammer, Gabriel; Cava, Antonio; Cardiel, Nicolas; Ceverino, Daniel; Eliche, Carmen; Fang, Jerome J.; Finkelstein, Steven L.; Kocevski, Dale D.; Livermore, Rachael C.; McGrath, Elizabeth

    2016-04-01

    We present Keck I MOSFIRE spectroscopy in the Y and H bands of GDN-8231, a massive, compact, star-forming galaxy at a redshift of z ˜ 1.7. Its spectrum reveals both Hα and [N ii] emission lines and strong Balmer absorption lines. The Hα and Spitzer MIPS 24 μm fluxes are both weak, thus indicating a low star-formation rate of SFR ≲ 5{--}10 {M}⊙ yr-1. This, added to a relatively young age of ˜700 Myr measured from the absorption lines, provides the first direct evidence for a distant galaxy being caught in the act of rapidly shutting down its star formation. Such quenching allows GDN-8231 to become a compact, quiescent galaxy, similar to three other galaxies in our sample, by z ˜ 1.5. Moreover, the color profile of GDN-8231 shows a bluer center, consistent with the predictions of recent simulations for an early phase of inside-out quenching. Its line-of-sight velocity dispersion for the gas, {σ }{{{LOS}}}{{gas}} = 127 ± 32 km s-1, is nearly 40% smaller than that of its stars, {σ }{{{LOS}}}\\star = 215 ± 35 km s-1. High-resolution hydro-simulations of galaxies explain such apparently colder gas kinematics of up to a factor of ˜1.5 with rotating disks being viewed at different inclinations and/or centrally concentrated star-forming regions. A clear prediction is that their compact, quiescent descendants preserve some remnant rotation from their star-forming progenitors.

  6. A Kinematic Approach to Assessing Environmental Effects: Star-forming Galaxies in a z ~ 0.9 SpARCS Cluster Using Spitzer 24 μm Observations

    NASA Astrophysics Data System (ADS)

    Noble, A. G.; Webb, T. M. A.; Muzzin, A.; Wilson, G.; Yee, H. K. C.; van der Burg, R. F. J.

    2013-05-01

    We present an infrared study of a z = 0.872 cluster, SpARCS J161314+564930, with the primary aim of distinguishing the dynamical histories of spectroscopically confirmed star-forming members to assess the role of cluster environment. We utilize deep MIPS imaging and a mass-limited sample of 85 spectroscopic members to identify 16 24 μm bright sources within the cluster, and measure their 24 μm star formation rates (SFRs) down to ~6 M ⊙ yr-1. Based on their line-of-sight velocities and stellar ages, MIPS cluster members appear to be an infalling population that was recently accreted from the field with minimal environmental dependency on their star formation. However, we identify a double-sequenced distribution of star-forming galaxies among the members, with one branch exhibiting declining specific SFRs with mass. The members along this sub-main sequence contain spectral features suggestive of passive galaxies. Using caustic diagrams, we kinematically identify these galaxies as a virialized and/or backsplash population. Moreover, we find a mix of dynamical histories at all projected radii, indicating that standard definitions of environment (i.e., radius and density) are contaminated with recently accreted interlopers, which could contribute to a lack of environmental trends for star-forming galaxies. A cleaner narrative of their dynamical past begins to unfold when using a proxy for accretion histories through profiles of constant (r/r 200) × (Δv/σ v ); galaxies accreted at earlier times possess lower values of (r/r 200) × (Δv/σ v ) with minimal contamination from the distinct infalling population. Therefore, adopting a time-averaged definition for density (as traced by accretion histories) rather than an instantaneous density yields a depressed specific SFR within the dynamical cluster core.

  7. The evolution of the equivalent width of the Hα emission line and specific star formation rate in star-forming galaxies at 1 < z < 5

    NASA Astrophysics Data System (ADS)

    Mármol-Queraltó, E.; McLure, R. J.; Cullen, F.; Dunlop, J. S.; Fontana, A.; McLeod, D. J.

    2016-08-01

    We present the results of a study which uses spectral energy distribution (SED) fitting to investigate the evolution of the equivalent width (EW) of the Hα emission line in star-forming galaxies over the redshift interval 1 < z < 5. After first demonstrating the ability of our SED-fitting technique to recover EW(Hα) using a sample of galaxies at z ≃ 1.3 with EW(Hα) measurements from 3D-HST grism spectroscopy, we proceed to apply our technique to samples of spectroscopically confirmed and photometric-redshift selected star-forming galaxies at z ≥ 1 in the CANDELS (Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey) UDS and GOODS-S fields. Confining our analysis to a constant stellar mass range (9.5 < log (M⋆/M⊙) < 10.5), we find that the median EW(Hα) evolves only modestly with redshift, reaching a rest-frame value of EW(Hα) =301 ± 30 Å by redshift z ≃ 4.5. Furthermore, using estimates of star formation rate (SFR) based on both UV luminosity and Hα line flux, we use our galaxy samples to compare the evolution of EW(Hα) and specific star formation rate (sSFR). Our results indicate that over the redshift range 1 < z < 5, the evolution displayed by EW(Hα) and sSFR is consistent, and can be adequately parametrized as ∝ (1 + z)1.0 ± 0.2. As a consequence, over this redshift range, we find that the sSFR and rest-frame EW(Hα) of star-forming galaxies with stellar masses M⋆ ≃ 10^{10}{ M_{sun;} are related by EW(Hα)/Å = (63 ± 7) × sSFR/Gyr-1. Given the current uncertainties in measuring the SFRs of high-redshift galaxies, we conclude that EW(Hα) provides a useful independent tracer of sSFR for star-forming galaxies out to redshifts of z = 5.

  8. MAMBO 1.2 mm Observations of BzK-selected Star-forming Galaxies at z ~ 2

    NASA Astrophysics Data System (ADS)

    Dannerbauer, H.; Daddi, E.; Onodera, M.; Kong, X.; Röttgering, H.; Arimoto, N.; Brusa, M.; Cimatti, A.; Kurk, J.; Lehnert, M. D.; Mignoli, M.; Renzini, A.

    2006-01-01

    We present MAMBO 1.2 mm observations of five BzK-preselected vigorous starburst galaxies at z~2. Two of these were detected at more than 99.5% confidence levels, with 1.2 mm fluxes around 1.5 mJy. These millimeter fluxes imply vigorous activity with star formation rates (SFRs) of ~500-1500 Msolar yr-1, which were also confirmed by detections at 24 μm with the Multiband Imaging Photometer on Spitzer (MIPS). The two detected galaxies are the ones in the sample with the highest SFRs estimated from the rest-frame UV, and their far-IR-derived and UV-derived SFRs agree reasonably well. This is different from local ultraluminous infrared galaxies (ULIRGs) and high-z submillimeter/millimeter-selected galaxies, for which the UV is reported to underestimate SFRs by factors of 10-100, but similar to the average BzK ULIRG at z~2. The two galaxies detected at 1.2 mm are brighter in K than the typical NIR counterparts of MAMBO and SCUBA sources, implying a significantly different K-band-to-submillimeter/millimeter flux ratio as well. This suggests a scenario in which z~2 galaxies, after their rapid (sub)millimeter-bright phase that is opaque to optical/UV light, evolve into a longer lasting phase of K-band-bright and massive objects. Targeting the most UV-active BzK galaxies could yield substantial detection rates at submillimeter/millimeter wavelengths. Based on observations carried out with the IRAM 30 m Telescope at Pico Veleta. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Also based on ESO observations (program IDs 072.A-0506 and 075.A-0439) and on Subaru observations (programs S02B-101 and S04A-081), and on observations made with the Spitzer Space Telescope, which is operated by the JPL, Caltech, under a contract with NASA.

  9. A Systematic Investigation of Cold Gas and Dust in "Normal" Star-Forming Galaxies and Starbursts at Redshifts 5-6

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Carilli, Chris Luke; Capak, Peter L.; COSMOS, HerMES

    2016-01-01

    Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the material that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We present some of the most recent progress in studies of gas-rich galaxies out to the highest redshifts through detailed investigations of the cold gas and dust with the most powerful facilities, i.e., the Karl G. Jansky Very Large Array (VLA), the NOrthern Extended Millimeter Array (NOEMA) and the Atacama Large (sub-) Millimeter Array (ALMA). Facilitating the impressive sensitivity of ALMA, this investigation encompasses a systematic study of the star-forming interstellar medium, gas dynamics, and dust obscuration in massive dusty starbursts and (much less luminous and massive) "typical" galaxies at such early epochs. These new results show that "typical" z>5 galaxies are significantly metal-enriched, but not heavily dust-obscured, consistent with a decreasing contribution of dust-obscured star formation to the star formation history of the universe towards the earliest cosmic epochs.

  10. Investigating nearby star-forming galaxies in the ultraviolet with HST/COS spectroscopy. I. Spectral analysis and interstellar abundance determinations

    SciTech Connect

    James, B. L.; Aloisi, A.; Sohn, S. T.; Wolfe, M. A.; Heckman, T.

    2014-11-10

    This is the first in a series of three papers describing a project with the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure abundances of the neutral interstellar medium (ISM) in a sample of nine nearby star-forming galaxies. The goal is to assess the (in)homogeneities of the multiphase ISM in galaxies where the bulk of metals can be hidden in the neutral phase, yet the metallicity is inferred from the ionized gas in the H II regions. The sample, spanning a wide range in physical properties, is to date the best suited to investigate the metallicity behavior of the neutral gas at redshift z = 0. ISM absorption lines were detected against the far-ultraviolet spectra of the brightest star-forming region(s) within each galaxy. Here we report on the observations, data reduction, and analysis of these spectra. Column densities were measured by a multicomponent line-profile fitting technique, and neutral-gas abundances were obtained for a wide range of elements. Several caveats were considered, including line saturation, ionization corrections, and dust depletion. Ionization effects were quantified with ad hoc CLOUDY models reproducing the complex photoionization structure of the ionized and neutral gas surrounding the UV-bright sources. An 'average spectrum of a redshift z = 0 star-forming galaxy' was obtained from the average column densities of unsaturated profiles of neutral-gas species. This template can be used as a powerful tool for studies of the neutral ISM at both low and high redshift.

  11. GALAXY EVOLUTION. An over-massive black hole in a typical star-forming galaxy, 2 billion years after the Big Bang.

    PubMed

    Trakhtenbrot, Benny; Urry, C Megan; Civano, Francesca; Rosario, David J; Elvis, Martin; Schawinski, Kevin; Suh, Hyewon; Bongiorno, Angela; Simmons, Brooke D

    2015-07-10

    Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. The radiation emitted from the growing SMBH is expected to affect star formation throughout the host galaxy. The relevance of this scenario at early cosmic epochs is not yet established. We present spectroscopic observations of a galaxy at redshift z = 3.328, which hosts an actively accreting, extremely massive BH, in its final stages of growth. The SMBH mass is roughly one-tenth the mass of the entire host galaxy, suggesting that it has grown much more efficiently than the host, contrary to models of synchronized coevolution. The host galaxy is forming stars at an intense rate, despite the presence of a SMBH-driven gas outflow.

  12. GALAXY EVOLUTION. An over-massive black hole in a typical star-forming galaxy, 2 billion years after the Big Bang.

    PubMed

    Trakhtenbrot, Benny; Urry, C Megan; Civano, Francesca; Rosario, David J; Elvis, Martin; Schawinski, Kevin; Suh, Hyewon; Bongiorno, Angela; Simmons, Brooke D

    2015-07-10

    Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. The radiation emitted from the growing SMBH is expected to affect star formation throughout the host galaxy. The relevance of this scenario at early cosmic epochs is not yet established. We present spectroscopic observations of a galaxy at redshift z = 3.328, which hosts an actively accreting, extremely massive BH, in its final stages of growth. The SMBH mass is roughly one-tenth the mass of the entire host galaxy, suggesting that it has grown much more efficiently than the host, contrary to models of synchronized coevolution. The host galaxy is forming stars at an intense rate, despite the presence of a SMBH-driven gas outflow. PMID:26160942

  13. Spectroscopic pilot study in the near infrared of a sample of star-forming galaxies at z = 2

    NASA Astrophysics Data System (ADS)

    Gallego, J.; Sánchez de Miguel, A.; Zamorano, J.; Pérez-González, P. G.; Cardiel, N.; Barro, G.

    2011-11-01

    In this work we present the results of the spectroscopic analysis inthe near-infrared K band of a sample of 12 active star forminggalaxies at z ˜ 2. The sample was selected by using photometricredshifts, blue colors and large fluxes in the 24 μ m band ofMIPS/Spitzer. To analyze their physical properties we have computedtheir sizes, colors, stellar masses, extinctions and other parametersavailable in literature and in the "Rainbow" database. We computeHα luminosities and star formation rates for all galaxies atthat redshift. We were able to estimate metallicities from [NII]6584for a sub sample of the objects. In particular the dependence of the metallicitywith the stellar mass has been studied and compared with the results of other samples ofgalaxies at several redshifts. For a fixed mass, the metallicities ofour galaxies are compatible than those similar at the corresponding redshift, following the general trend of lower metallicities for higher redshifts.

  14. Sejong Open Cluster Survey (SOS) - V. The Active Star Forming Region SH 2-255-257

    NASA Astrophysics Data System (ADS)

    Lim, Beomdu; Sung, Hwankyung; Hur, Hyeonoh; Lee, Byeong-Cheol; Bessell, Michael S.; Kim, Jinyoung S.; Lee, Kang Hwan; Park, Byeong-Gon; Jeong, Gwanghui

    2015-12-01

    There is much observational evidence that active star formation is taking place in the H II regions Sh 2-255-257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B-V) = 0.8 mag, and the reddening law toward the region is normal (R_V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J-H) color-magnitude diagram. The slope of the IMF is about Γ = -1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169 M_{⊙}). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

  15. Spectroscopic study in the visible and near infrared wavelength of an Hα-selected sample of star-forming galaxies at z = 0.84

    NASA Astrophysics Data System (ADS)

    Sánchez de Miguel, A.; Gallego, J.; Villar, V.; Pérez-González, P. G.; Zamorano, J.; Cardiel, N.; Acosta Pulido, J. A.

    2013-05-01

    In this work we study the physical properties of star-forming galaxies selected in an Hα near-infrared narrow-band survey tuned for redshift z=0.84 (Villar et al. 2008, 2011). Also, we present a sample at z˜1 with mass greater than 10^{10} M_{⊙} with Hα emission. The observations were carried out with WHT/LIRIS (see Sánchez de Miguel et al. 2011, in Highlights of Spanish Astrophysics VI). The rest of the data from the spectra archive of the RAINBOW Cosmological Survey database (Pérez-González et al. 2005, 2008; Barro et al. 2011ab). According to the redshift distribution of these galaxies, 65% of the galaxies are in a redshift range of 0.005. This velocity range corresponds to less than 25% of the effective volume. Which could be indicative of the presence of substructure. A total of 48 galaxies have detected Hα emission and other 12 show [NII]6584. To complete our multi-wavelength sample we found 23 galaxies with Hβ, [OIII]5007 or [OII]3727 detections. Using this photometry from ancillary data we will calculate nebular and stellar extinctions. We have calculated metallicities using the [NII]/Hα ratio and the Pettini & Pagel (2004) calibrations. The metallicity of samples are compatible with the local galaxies. We found that in all the diagnostic diagrams galaxies have similar properties to the local ones, except they are intrinsically brighter for the same equivalent width [OII]3727.

  16. The MOSDEF Survey: Detection of [O III]λ4363 and the Direct-method Oxygen Abundance of a Star-forming Galaxy at z = 3.08

    NASA Astrophysics Data System (ADS)

    Sanders, Ryan L.; Shapley, Alice E.; Kriek, Mariska; Reddy, Naveen A.; Freeman, William R.; Coil, Alison L.; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H.; de Groot, Laura

    2016-07-01

    We present measurements of the electron-temperature-based oxygen abundance for a highly star-forming galaxy at z = 3.08, COSMOS-1908. This is the highest redshift at which [O iii]λ4363 has been detected and the first time that this line has been measured at z\\gt 2. We estimate an oxygen abundance of 12+{log}({{O}}/{{H}})={8.00}-0.14+0.13. This galaxy is a low-mass ({10}9.3 {M}ȯ ), highly star-forming (˜50 {M}ȯ yr‑1) system that hosts a young stellar population (˜160 Myr). We investigate the physical conditions of the ionized gas in COSMOS-1908 and find that this galaxy has a high ionization parameter, little nebular reddening (E{(B-V)}{{gas}}\\lt 0.14), and a high electron density ({n}e˜ 500 cm‑3). We compare the ratios of strong oxygen, neon, and hydrogen lines to the direct-method oxygen abundance for COSMOS-1908 and additional star-forming galaxies at z=0-1.8 with [O iii]λ4363 measurements and show that galaxies at z˜ 1{--}3 follow the same strong-line correlations as galaxies in the local universe. This agreement suggests that the relationship between ionization parameter and O/H is similar for z˜ 0 and high-redshift galaxies. These results imply that metallicity calibrations based on lines of oxygen, neon, and hydrogen do not strongly evolve with redshift and can reliably estimate abundances out to z˜ 3, paving the way for robust measurements of the evolution of the mass–metallicity relation to high redshift. 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.

  17. The MOSDEF Survey: Detection of [O III]λ4363 and the Direct-method Oxygen Abundance of a Star-forming Galaxy at z = 3.08

    NASA Astrophysics Data System (ADS)

    Sanders, Ryan L.; Shapley, Alice E.; Kriek, Mariska; Reddy, Naveen A.; Freeman, William R.; Coil, Alison L.; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H.; de Groot, Laura

    2016-07-01

    We present measurements of the electron-temperature-based oxygen abundance for a highly star-forming galaxy at z = 3.08, COSMOS-1908. This is the highest redshift at which [O iii]λ4363 has been detected and the first time that this line has been measured at z\\gt 2. We estimate an oxygen abundance of 12+{log}({{O}}/{{H}})={8.00}-0.14+0.13. This galaxy is a low-mass ({10}9.3 {M}⊙ ), highly star-forming (˜50 {M}⊙ yr-1) system that hosts a young stellar population (˜160 Myr). We investigate the physical conditions of the ionized gas in COSMOS-1908 and find that this galaxy has a high ionization parameter, little nebular reddening (E{(B-V)}{{gas}}\\lt 0.14), and a high electron density ({n}e˜ 500 cm-3). We compare the ratios of strong oxygen, neon, and hydrogen lines to the direct-method oxygen abundance for COSMOS-1908 and additional star-forming galaxies at z=0-1.8 with [O iii]λ4363 measurements and show that galaxies at z˜ 1{--}3 follow the same strong-line correlations as galaxies in the local universe. This agreement suggests that the relationship between ionization parameter and O/H is similar for z˜ 0 and high-redshift galaxies. These results imply that metallicity calibrations based on lines of oxygen, neon, and hydrogen do not strongly evolve with redshift and can reliably estimate abundances out to z˜ 3, paving the way for robust measurements of the evolution of the mass-metallicity relation to high redshift. 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.

  18. Narrow He II emission in star-forming galaxies at low metallicity. Stellar wind emission from a population of very massive stars

    NASA Astrophysics Data System (ADS)

    Gräfener, G.; Vink, J. S.

    2015-06-01

    Context. In a recent study, star-forming galaxies with He ii λ1640 emission at moderate redshifts between 2 and 4.6 have been found to occur in two modes that are distinguished by the width of their He ii emission lines. Broad He ii emission has been attributed to stellar emission from a population of evolved Wolf-Rayet (WR) stars. The origin of narrow He ii emission is less clear but has been attributed to nebular emission excited by a population of very hot Pop III stars formed in pockets of pristine gas at moderate redshifts. Aims: We propose an alternative scenario for the origin of the narrow He ii emission, namely very massive stars (VMS) at low metallicity (Z), which form strong but slow WR-type stellar winds due to their proximity to the Eddington limit. Methods: We estimated the expected He ii line fluxes and equivalent widths based on wind models for VMS and Starburst99 population synthesis models and compared the results with recent observations of star-forming galaxies at moderate redshifts. Results: The observed He ii line strengths and equivalent widths are in line with what is expected for a population of VMS in one or more young super-clusters located within these galaxies. Conclusions: In our scenario the two observed modes of He ii emission originate from massive stellar populations in distinct evolutionary stages at low Z (~0.01 Z⊙). If this interpretation is correct, there is no need to postulate the existence of Pop III stars at moderate redshifts to explain the observed narrow He ii emission. An interesting possibility is the existence of self-enriched VMS with similar WR-type spectra at extremely low Z. Stellar He ii emission from such very early generations of VMS may be detectable in future studies of star-forming galaxies at high redshifts with the James Webb Space Telescope (JWST). The fact that the He ii emission of VMS is largely neglected in current population synthesis models will generally affect the interpretation of the

  19. THE AVERAGE PHYSICAL PROPERTIES AND STAR FORMATION HISTORIES OF THE UV-BRIGHTEST STAR-FORMING GALAXIES AT z {approx} 3.7

    SciTech Connect

    Lee, Kyoung-Soo; Glikman, Eilat; Dey, Arjun; Reddy, Naveen; Jannuzi, Buell T.; Brown, Michael J. I.; Gonzalez, Anthony H.; Cooper, Michael C.; Fan Xiaohui; Bian Fuyan; Stern, Daniel; Brodwin, Mark; Cooray, Asantha

    2011-06-01

    We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star-forming galaxies at z {approx} 3.7. Our results are based on the average spectral energy distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg{sup 2} of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope {beta} ({identical_to} dlogF{sub {lambda}}/dlog{lambda}; measured at 0.13 {mu}m < {lambda}{sub rest} < 0.28 {mu}m) rises steeply with the median UV luminosity from -1.8 at L {approx} L* to -1.2 (L {approx} 4-5L*). We use population synthesis analyses to derive their average physical properties and find that (1) L{sub UV} and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400 Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less-luminous counterparts, such that L {approx} 4-5L* galaxies are extincted up to A(1600) = 2 mag while L {approx} L* galaxies have A(1600) = 0.7-1.5 mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M{sub *} relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2 Gyr and their possible connection to the most massive galaxies at

  20. Probing the Peak Epoch of Cosmic Star Formation (1Star-forming Galaxies Behind the Lensing Clusters: UV Luminosity Function and the Dust Attenuation

    NASA Astrophysics Data System (ADS)

    Alavi, Anahita; Siana, Brian D.; Richard, Johan; Rafelski, Marc; Jauzac, Mathilde; Limousin, Marceau; Stark, Daniel; Teplitz, Harry I.

    2016-01-01

    Obtaining a complete census of cosmic star formation requires an understanding of faint star-forming galaxies that are far below the detection limits of current surveys. To search for the faint galaxies, we use the power of strong gravitational lensing from foreground galaxy clusters to boost the detection limits of HST to much fainter luminosities. Using the WFC3/UVIS on board the HST, we obtain deep UV images of 4 lensing clusters with existing deep optical and near-infrared data (three from Frontier Fields survey). Building multiband photometric catalogs and applying a photometric redshift selection, we uncover a large population of dwarf galaxies (-18.5star-forming galaxies keeps increasing steeply toward very faint magnitudes (MUV=-12.5). As an important implication of a steep faint-end slope LF, we show that the faint galaxies (-18.550%) at these redshifts. We use this unique sample to investigate further the various properties of dwarf galaxies as it is claimed to deviate from the trends seen for the more massive galaxies. Recent hydro-dynamical simulations and observations of local dwarfs show that these galaxies have episodic bursts of star formation on short time scales (< 10 Myr). We find that the bursty star formation histories (SFHs) cause a large intrinsic scatter in UV colors (β) at MUV > -16, comparing a sample of low mass galaxies from simulations with bursty SFHs with our comprehensive measurements of the observed β values. As this scatter can also be due to the dust extinction, we distinguish these two effects by measuring the dust attenuation using Balmer decrement (Hα/Hβ) ratios from our MOSFIRE/Keck spectroscopy.

  1. The MOSDEF Survey: The Strong Agreement Between Hα and UV-To-FIR Star Formation Rates for z ~ 2 Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Shivaei, Irene; Reddy, Naveen; Kriek, Mariska T.; Shapley, Alice E.; Mobasher, Bahram; Coil, Alison L.; Siana, Brian D.; Sanders, Ryan; Price, Sedona; Freeman, William R.; Azadi, Mojegan

    2016-06-01

    We present the first direct comparison between Balmer line and panchromatic SED-based star-formation rates (SFRs) for z ~ 2 galaxies. While dust-corrected SFRs(Hα,Hβ) using Balmer decrements are commonly used at low redshift, it has been argued that Balmer lines may miss optically thick star-forming regions at high redshifts. In order to investigate this possible bias, we compare the SFRs(Hα,Hβ) with independently measured UV-to-far-IR SFRs for star-forming galaxies at z ~ 2. For this comparison we use a sample of galaxies selected from the unique spectroscopic dataset of the MOSFIRE Deep Evolution Field (MOSDEF) survey. The MOSDEF survey is a multi-year project that uses the near-IR MOSFIRE spectrograph on the 10-m Keck I telescope to characterize the gaseous and stellar contents of ~ 1500 rest-frame optically selected galaxies at 1.37 ≤ z ≤ 3.80. In addition to the rest-frame optical spectra, we use data from Spitzer/MIPS 24 μm, Herschel/PACS 100 and 160 μm, and Herschel/SPIRE 250, 350, and 500 μm to measure mid- and far-IR fluxes. We fit the UV-to-far-IR SEDs with the state-of-the-art flexible stellar population synthesis (FSPS) models, which utilize energy balance to fit the stellar and dust emission simultaneously. Comparing the SFR(Hα,Hβ) with the robust UV-to-far-IR SED inferrred SFRs, show us how accurately Balmer decrements predict the obscuration of the nebular lines in order to robustly calculate SFRs for star-forming galaxies at high redshift. Furthermore, we use our data to assess SFR indicators based on modeling the UV-to-mid-IR SEDs or by adding SFR(UV) and SFR(IR), for which the latter is based on the empirical conversions from mid-IR to total IR luminosity. This study shed light on the validity of various SFR indicators, specifically the nebular emission lines, for galaxies at z ~ 2.

  2. From H I to Stars: H I Depletion in Starbursts and Star-forming Galaxies in the ALFALFA Hα Survey

    NASA Astrophysics Data System (ADS)

    Jaskot, A. E.; Oey, M. S.; Salzer, J. J.; Van Sistine, A.; Bell, E. F.; Haynes, M. P.

    2015-07-01

    H i in galaxies traces the fuel for future star formation and reveals the effects of feedback on neutral gas. Using a statistically uniform, H i-selected sample of 565 galaxies from the Arecibo Legacy Fast ALFA (ALFALFA) Hα survey, we explore H i properties as a function of star formation activity. ALFALFA Hα provides R-band and Hα imaging for a volume-limited subset of the 21 cm ALFALFA survey. We identify eight starbursts based on Hα equivalent width and six with enhanced star formation relative to the main sequence. Both starbursts and non-starbursts have similar H i-to-stellar mass ratios ({M}{{H} {{I}}}/{M}*), which suggests that feedback is not depleting the starbursts’ H i. Consequently, the starbursts do have shorter H i depletion times ({t}{dep}), implying more efficient H i-to-H2 conversion. While major mergers likely drive this enhanced efficiency in some starbursts, the lowest-mass starbursts may experience periodic bursts, consistent with enhanced scatter in {t}{dep} at low {M}*. Two starbursts appear to be pre-coalescence mergers; their elevated {M}{{H} {{I}}}/{M}* suggest that H i-to-H2 conversion is still ongoing at this stage. By comparing with the GASS sample, we find that {t}{dep} anticorrelates with stellar surface density for disks, while spheroids show no such trend. Among early-type galaxies, {t}{dep} does not correlate with bulge-to-disk ratio; instead, the gas distribution may determine the star formation efficiency. Finally, the weak connection between galaxies’ specific star formation rates and {M}{{H} {{I}}}/{M}* contrasts with the well-known correlation between {M}{{H} {{I}}}/{M}* and color. We show that dust extinction can explain the H i–color trend, which may arise from the relationship between {M}*, {M}{{H} {{I}}}, and metallicity.

  3. From H I to Stars: H I Depletion in Starbursts and Star-forming Galaxies in the ALFALFA Hα Survey

    NASA Astrophysics Data System (ADS)

    Jaskot, A. E.; Oey, M. S.; Salzer, J. J.; Van Sistine, A.; Bell, E. F.; Haynes, M. P.

    2015-07-01

    H i in galaxies traces the fuel for future star formation and reveals the effects of feedback on neutral gas. Using a statistically uniform, H i-selected sample of 565 galaxies from the Arecibo Legacy Fast ALFA (ALFALFA) Hα survey, we explore H i properties as a function of star formation activity. ALFALFA Hα provides R-band and Hα imaging for a volume-limited subset of the 21 cm ALFALFA survey. We identify eight starbursts based on Hα equivalent width and six with enhanced star formation relative to the main sequence. Both starbursts and non-starbursts have similar H i-to-stellar mass ratios ({M}{{H} {{I}}}/{M}*), which suggests that feedback is not depleting the starbursts’ H i. Consequently, the starbursts do have shorter H i depletion times ({t}{dep}), implying more efficient H i-to-H2 conversion. While major mergers likely drive this enhanced efficiency in some starbursts, the lowest-mass starbursts may experience periodic bursts, consistent with enhanced scatter in {t}{dep} at low {M}*. Two starbursts appear to be pre-coalescence mergers; their elevated {M}{{H} {{I}}}/{M}* suggest that H i-to-H2 conversion is still ongoing at this stage. By comparing with the GASS sample, we find that {t}{dep} anticorrelates with stellar surface density for disks, while spheroids show no such trend. Among early-type galaxies, {t}{dep} does not correlate with bulge-to-disk ratio; instead, the gas distribution may determine the star formation efficiency. Finally, the weak connection between galaxies’ specific star formation rates and {M}{{H} {{I}}}/{M}* contrasts with the well-known correlation between {M}{{H} {{I}}}/{M}* and color. We show that dust extinction can explain the H i-color trend, which may arise from the relationship between {M}*, {M}{{H} {{I}}}, and metallicity.

  4. The Complex Physics of Dusty Star-forming Galaxies at High Redshifts as Revealed by Herschel and Spitzer

    NASA Astrophysics Data System (ADS)

    Lo Faro, B.; Franceschini, A.; Vaccari, M.; Silva, L.; Rodighiero, G.; Berta, S.; Bock, J.; Burgarella, D.; Buat, V.; Cava, A.; Clements, D. L.; Cooray, A.; Farrah, D.; Feltre, A.; González Solares, E. A.; Hurley, P.; Lutz, D.; Magdis, G.; Magnelli, B.; Marchetti, L.; Oliver, S. J.; Page, M. J.; Popesso, P.; Pozzi, F.; Rigopoulou, D.; Rowan-Robinson, M.; Roseboom, I. G.; Scott, Douglas; Smith, A. J.; Symeonidis, M.; Wang, L.; Wuyts, S.

    2013-01-01

    We combine far-infrared photometry from Herschel (PEP/HerMES) with deep mid-infrared spectroscopy from Spitzer to investigate the nature and the mass assembly history of a sample of 31 luminous and ultraluminous infrared galaxies ((U)LIRGs) at z ~ 1 and 2 selected in GOODS-S with 24 μm fluxes between 0.2 and 0.5 mJy. We model the data with a self-consistent physical model (GRASIL) which includes a state-of-the-art treatment of dust extinction and reprocessing. We find that all of our galaxies appear to require massive populations of old (>1 Gyr) stars and, at the same time, to host a moderate ongoing activity of star formation (SFR <= 100 M ⊙ yr-1). The bulk of the stars appear to have been formed a few Gyr before the observation in essentially all cases. Only five galaxies of the sample require a recent starburst superimposed on a quiescent star formation history. We also find discrepancies between our results and those based on optical-only spectral energy distribution (SED) fitting for the same objects; by fitting their observed SEDs with our physical model we find higher extinctions (by ΔA V ~ 0.81 and 1.14) and higher stellar masses (by Δlog(M sstarf) ~ 0.16 and 0.36 dex) for z ~ 1 and z ~ 2 (U)LIRGs, respectively. The stellar mass difference is larger for the most dust-obscured objects. We also find lower SFRs than those computed from L IR using the Kennicutt relation due to the significant contribution to the dust heating by intermediate-age stellar populations through "cirrus" emission (~73% and ~66% of the total L IR for z ~ 1 and z ~ 2 (U)LIRGs, respectively). Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  5. THE COMPLEX PHYSICS OF DUSTY STAR-FORMING GALAXIES AT HIGH REDSHIFTS AS REVEALED BY HERSCHEL AND SPITZER

    SciTech Connect

    Lo Faro, B.; Franceschini, A.; Vaccari, M.; Rodighiero, G.; Feltre, A.; Marchetti, L.; Silva, L.; Berta, S.; Lutz, D.; Magnelli, B.; Bock, J.; Burgarella, D.; Buat, V.; Cava, A.; Clements, D. L.; Cooray, A.; Farrah, D.; Hurley, P.; Solares, E. A. Gonzalez; Magdis, G.; and others

    2013-01-10

    We combine far-infrared photometry from Herschel (PEP/HerMES) with deep mid-infrared spectroscopy from Spitzer to investigate the nature and the mass assembly history of a sample of 31 luminous and ultraluminous infrared galaxies ((U)LIRGs) at z {approx} 1 and 2 selected in GOODS-S with 24 {mu}m fluxes between 0.2 and 0.5 mJy. We model the data with a self-consistent physical model (GRASIL) which includes a state-of-the-art treatment of dust extinction and reprocessing. We find that all of our galaxies appear to require massive populations of old (>1 Gyr) stars and, at the same time, to host a moderate ongoing activity of star formation (SFR {<=} 100 M {sub Sun} yr{sup -1}). The bulk of the stars appear to have been formed a few Gyr before the observation in essentially all cases. Only five galaxies of the sample require a recent starburst superimposed on a quiescent star formation history. We also find discrepancies between our results and those based on optical-only spectral energy distribution (SED) fitting for the same objects; by fitting their observed SEDs with our physical model we find higher extinctions (by {Delta}A {sub V} {approx} 0.81 and 1.14) and higher stellar masses (by {Delta}log(M {sub *}) {approx} 0.16 and 0.36 dex) for z {approx} 1 and z {approx} 2 (U)LIRGs, respectively. The stellar mass difference is larger for the most dust-obscured objects. We also find lower SFRs than those computed from L {sub IR} using the Kennicutt relation due to the significant contribution to the dust heating by intermediate-age stellar populations through 'cirrus' emission ({approx}73% and {approx}66% of the total L {sub IR} for z {approx} 1 and z {approx} 2 (U)LIRGs, respectively).

  6. SPITZER OBSERVATIONS OF PASSIVE AND STAR-FORMING EARLY-TYPE GALAXIES: AN INFRARED COLOR-COLOR SEQUENCE

    SciTech Connect

    Temi, Pasquale

    2009-12-20

    We describe the infrared properties of a large sample of early-type galaxies, comparing data from the Spitzer archive with Ks-band emission from the Two Micron All Sky Survey. While most representations of this data result in correlations with large scatter, we find a remarkably tight relation among colors formed by ratios of luminosities in Spitzer-Multiband Imaging Photometer bands (24, 70, and 160 mum) and the Ks band. Remarkably, this correlation among E and S0 galaxies follows that of nearby normal galaxies of all morphological types. In particular, the tight infrared color-color correlation for S0 galaxies alone follows that of the entire Hubble sequence of normal galaxies, roughly in order of galaxy type from ellipticals to spirals to irregulars. The specific star formation rate (SFR) of S0 galaxies estimated from the 24 mum luminosity increases with decreasing K-band luminosity (or stellar mass) from essentially zero, as with most massive ellipticals, to rates typical of irregular galaxies. Moreover, the luminosities of the many infrared-luminous S0 galaxies can significantly exceed those of the most luminous (presumably post-merger) E galaxies. SFRs in the most infrared-luminous S0 galaxies approach 1-10 solar masses per year. Consistently, with this picture we find that while most early-type galaxies populate an infrared red sequence, about 24% of the objects (mostly S0s) are in an infrared blue cloud together with late-type galaxies. For those early-type galaxies also observed at radio frequencies, we find that the far-infrared luminosities correlate with the mass of neutral and molecular hydrogen, but the scatter is large. This scatter suggests that the star formation may be intermittent or that similar S0 galaxies with cold gaseous disks of nearly equal mass can have varying radial column density distributions that alter the local and global SFRs.

  7. SMOOTH(ER) STELLAR MASS MAPS IN CANDELS: CONSTRAINTS ON THE LONGEVITY OF CLUMPS IN HIGH-REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Wuyts, Stijn; Foerster Schreiber, Natascha M.; Genzel, Reinhard; Lutz, Dieter; Guo Yicheng; Giavalisco, Mauro; Barro, Guillermo; Faber, Sandra M.; Kocevski, Dale D.; Koo, David C.; McGrath, Elizabeth; Dekel, Avishai; Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M.; Lotz, Jennifer; Hathi, Nimish P.; Huang, Kuang-Han; Newman, Jeffrey A.; and others

    2012-07-10

    We perform a detailed analysis of the resolved colors and stellar populations of a complete sample of 323 star-forming galaxies (SFGs) at 0.5 < z < 1.5 and 326 SFGs at 1.5 < z < 2.5 in the ERS and CANDELS-Deep region of GOODS-South. Galaxies were selected to be more massive than 10{sup 10} M{sub Sun} and have specific star formation rates (SFRs) above 1/t{sub H} . We model the seven-band optical ACS + near-IR WFC3 spectral energy distributions of individual bins of pixels, accounting simultaneously for the galaxy-integrated photometric constraints available over a longer wavelength range. We analyze variations in rest-frame color, stellar surface mass density, age, and extinction as a function of galactocentric radius and local surface brightness/density, and measure structural parameters on luminosity and stellar mass maps. We find evidence for redder colors, older stellar ages, and increased dust extinction in the nuclei of galaxies. Big star-forming clumps seen in star formation tracers are less prominent or even invisible in the inferred stellar mass distributions. Off-center clumps contribute up to {approx}20% to the integrated SFR, but only 7% or less to the integrated mass of all massive SFGs at z {approx} 1 and z {approx} 2, with the fractional contributions being a decreasing function of wavelength used to select the clumps. The stellar mass profiles tend to have smaller sizes and M20 coefficients, and higher concentration and Gini coefficients than the light distribution. Our results are consistent with an inside-out disk growth scenario with brief (100-200 Myr) episodic local enhancements in star formation superposed on the underlying disk. Alternatively, the young ages of off-center clumps may signal inward clump migration, provided this happens efficiently on the order of an orbital timescale.

  8. Detection of hot, metal-enriched outflowing gas around z ≈ 2.3 star-forming galaxies in the Keck Baryonic Structure Survey

    NASA Astrophysics Data System (ADS)

    Turner, Monica L.; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison L.

    2015-06-01

    We use quasar absorption lines to study the physical conditions in the circumgalactic medium of redshift z ≈ 2.3 star-forming galaxies taken from the Keck Baryonic Structure Survey. In Turner et al. we used the pixel optical depth technique to show that absorption by H I and the metal ions O VI, N V, C IV, C III, and Si IV is strongly enhanced within |Δv| ≲ 170 km s-1 and projected distances |d| ≲ 180 proper kpc from sightlines to the background quasars. Here we demonstrate that the O VI absorption is also strongly enhanced at fixed H I, C IV, and Si IV optical depths, and that this enhancement extends out to ˜350 km s-1. At fixed H I the increase in the median O VI optical depth near galaxies is 0.3-0.7 dex and is detected at 2-3σ confidence for all seven H I bins that have log _{10}τ_{H I} ≥ -1.5. We use ionization models to show that the observed strength of O VI as a function of H I is consistent with enriched, photoionized gas for pixels with τ_{H I} ≳ 10. However, for pixels with τ_{H I} ≲ 1 this would lead to implausibly high metallicities at low densities if the gas were photoionized by the background radiation. This indicates that the galaxies are surrounded by gas that is sufficiently hot to be collisionally ionized (T > 105 K) and that a substantial fraction of the hot gas has a metallicity ≳10-1 of solar. Given the high metallicity and large velocity extent (out to ˜1.5 vcirc) of this gas, we conclude that we have detected hot, metal-enriched outflows arising from star-forming galaxies.

  9. The UV–Optical Color Gradients in Star-forming Galaxies at 0.5 < z < 1.5: Origins and Link to Galaxy Assembly

    NASA Astrophysics Data System (ADS)

    Liu, F. S.; Jiang, Dongfei; Guo, Yicheng; Koo, David C.; Faber, S. M.; Zheng, Xianzhong; Yesuf, Hassen M.; Barro, Guillermo; Li, Yao; Li, Dingpeng; Wang, Weichen; Mao, Shude; Fang, Jerome J.

    2016-05-01

    The rest-frame UV–optical (i.e., NUV ‑ B) color index is sensitive to the low-level recent star formation and dust extinction, but it is insensitive to the metallicity. In this Letter, we have measured the rest-frame NUV ‑ B color gradients in ˜1400 large (r e > 0.″18), nearly face-on (b/a > 0.5) main sequence star-forming galaxies (SFGs) between redshift 0.5 and 1.5 in the CANDELS/GOODS-S and UDS fields. With this sample, we study the origin of UV–optical color gradients in the SFGs at z ˜ 1 and discuss their link with the buildup of stellar mass. We find that the more massive, centrally compact, and more dust extinguished SFGs tend to have statistically more negative raw color gradients (redder centers) than the less massive, centrally diffuse, and less dusty SFGs. After correcting for dust reddening based on optical-spectral energy distribution fitting, the color gradients in the low-mass (M * < 1010 M ⊙) SFGs generally become quite flat, while most of the high-mass (M * > 1010.5 M ⊙) SFGs still retain shallow negative color gradients. These findings imply that dust reddening is likely the principal cause of negative color gradients in the low-mass SFGs, while both increased central dust reddening and buildup of compact old bulges are likely the origins of negative color gradients in the high-mass SFGs. These findings also imply that at these redshifts the low-mass SFGs buildup their stellar masses in a self-similar way, while the high-mass SFGs grow inside out.

  10. ALMA Observation of 158 μm [C II] Line and Dust Continuum of a z = 7 Normally Star-forming Galaxy in the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Ota, Kazuaki; Walter, Fabian; Ohta, Kouji; Hatsukade, Bunyo; Carilli, Chris L.; da Cunha, Elisabete; González-López, Jorge; Decarli, Roberto; Hodge, Jacqueline A.; Nagai, Hiroshi; Egami, Eiichi; Jiang, Linhua; Iye, Masanori; Kashikawa, Nobunari; Riechers, Dominik A.; Bertoldi, Frank; Cox, Pierre; Neri, Roberto; Weiss, Axel

    2014-09-01

    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 σline = 240 μJy beam-1 (40 km s-1 channel) and σcont = 21 μJy beam-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) 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 dust < 6.4 × 107 M ⊙, FIR luminosity L FIR < 3.7 × 1010 L ⊙ (42.5-122.5 μm), total IR luminosity L IR < 5.7 × 1010 L ⊙ (8-1000 μm), and dust-obscured star formation rate (SFR) < 10 M ⊙ yr-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 [C II] < 3.4 × 107 L ⊙. Locations of IOK-1 and previously observed LAEs on the L [C II] versus SFR and L [C II]/L FIR versus L 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. Based in part on data collected with the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc

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

    SciTech Connect

    Ota, Kazuaki; Walter, Fabian; Da Cunha, Elisabete; González-López, Jorge; Decarli, Roberto; Hodge, Jacqueline A.; Ohta, Kouji; Hatsukade, Bunyo; Nagai, Hiroshi; Iye, Masanori; Kashikawa, Nobunari; Carilli, Chris L.; Egami, Eiichi; Jiang, Linhua; Riechers, Dominik A.; Bertoldi, Frank; Cox, Pierre; Neri, Roberto; Weiss, Axel

    2014-09-01

    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) 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.

  12. RECENT STELLAR MASS ASSEMBLY OF LOW-MASS STAR-FORMING GALAXIES AT REDSHIFTS 0.3 < z < 0.9

    SciTech Connect

    Rodríguez-Muñoz, Lucía; Gallego, Jesús; De Paz, Armando Gil; Villar, Víctor; Tresse, Laurence; Charlot, Stéphane; Barro, Guillermo

    2015-01-20

    The epoch when low-mass star-forming galaxies (LMSFGs) form the bulk of their stellar mass is uncertain. While some models predict an early formation, others favor a delayed scenario until later ages of the universe. We present constraints on the star formation histories (SFHs) of a sample of LMSFGs obtained through the analysis of their spectral energy distributions using a novel approach that (1) consistently combines photometric (broadband) and spectroscopic (equivalent widths of emission lines) data, and (2) uses physically motivated SFHs with non-uniform variations of the star formation rate (SFR) as a function of time. The sample includes 31 spectroscopically confirmed LMSFGs (7.3 ≤ log M {sub *}/M {sub ☉} ≤ 8.0), at 0.3 < z {sub spec} < 0.9, in the Extended-Chandra Deep Field-South field. Among them, 24 were selected with photometric stellar mass log M {sub *}/M {sub ☉} < 8.0, 0.3 < z {sub phot} < 1.0, and m {sub NB816,} {sub AB} < 26 mag; the remaining 7 were selected as blue compact dwarfs within the same photometric redshift and magnitude ranges. We also study a secondary sample of 43 more massive spectroscopically confirmed galaxies (8.0 < log M {sub *}/M {sub ☉} ≤ 9.1), selected with the same criteria. The SFRs and stellar masses derived for both samples place our targets on the standard main sequence of star-forming galaxies. The median SFH of LMSFGs at intermediate redshifts appears to form 90% of the median stellar mass inferred for the sample in the ∼0.5-1.8 Gyr immediately preceding the observation. These results suggest a recent stellar mass assembly for LMSFGs, consistent with the cosmological downsizing trends. We find similar median SFH timescales for the more massive secondary sample.

  13. Rest-UV Absorption Lines as Metallicity Estimator: The Metal Content of Star-forming Galaxies at z ~ 5

    NASA Astrophysics Data System (ADS)

    Faisst, A. L.; Capak, P. L.; Davidzon, I.; Salvato, M.; Laigle, C.; Ilbert, O.; Onodera, M.; Hasinger, G.; Kakazu, Y.; Masters, D.; McCracken, H. J.; Mobasher, B.; Sanders, D.; Silverman, J. D.; Yan, L.; Scoville, N. Z.

    2016-05-01

    We measure a relation between the depth of four prominent rest-UV absorption complexes and metallicity for local galaxies and verify it up to z˜ 3. We then apply this relation to a sample of 224 galaxies at 3.5\\lt z\\lt 6.0 (< z> =4.8) in the Cosmic Evolution Survey (COSMOS), for which unique UV spectra from the Deep Imaging Multi-object Spectrograph (DEIMOS) and accurate stellar masses from the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) are available. The average galaxy population at z˜ 5 and {log}(M/{M}⊙ )\\gt 9 is characterized by 0.3-0.4 dex (in units of 12+{log}({{O/H}})) lower metallicities than at z ˜ 2, but comparable to z˜ 3.5. We find galaxies with weak or no Lyα emission to have metallicities comparable to z ˜ 2 galaxies and therefore may represent an evolved subpopulation of z˜ 5 galaxies. We find a correlation between metallicity and dust in good agreement with local galaxies and an inverse trend between metallicity and star-formation rate consistent with observations at z ˜ 2. The relation between stellar mass and metallicity (MZ relation) is similar to z˜ 3.5, but there are indications of it being slightly shallower, in particular for the young, Lyα-emitting galaxies. We show that, within a “bathtub” approach, a shallower MZ relation is expected in the case of a fast (exponential) build-up of stellar mass with an e-folding time of 100-200 Myr. Because of this fast evolution, the process of dust production and metal enrichment as a function of mass could be more stochastic in the first billion years of galaxy formation compared to later times.

  14. Rest-UV Absorption Lines as Metallicity Estimator: The Metal Content of Star-forming Galaxies at z ~ 5

    NASA Astrophysics Data System (ADS)

    Faisst, A. L.; Capak, P. L.; Davidzon, I.; Salvato, M.; Laigle, C.; Ilbert, O.; Onodera, M.; Hasinger, G.; Kakazu, Y.; Masters, D.; McCracken, H. J.; Mobasher, B.; Sanders, D.; Silverman, J. D.; Yan, L.; Scoville, N. Z.

    2016-05-01

    We measure a relation between the depth of four prominent rest-UV absorption complexes and metallicity for local galaxies and verify it up to z˜ 3. We then apply this relation to a sample of 224 galaxies at 3.5\\lt z\\lt 6.0 (< z> =4.8) in the Cosmic Evolution Survey (COSMOS), for which unique UV spectra from the Deep Imaging Multi-object Spectrograph (DEIMOS) and accurate stellar masses from the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) are available. The average galaxy population at z˜ 5 and {log}(M/{M}ȯ )\\gt 9 is characterized by 0.3–0.4 dex (in units of 12+{log}({{O/H}})) lower metallicities than at z ˜ 2, but comparable to z˜ 3.5. We find galaxies with weak or no Lyα emission to have metallicities comparable to z ˜ 2 galaxies and therefore may represent an evolved subpopulation of z˜ 5 galaxies. We find a correlation between metallicity and dust in good agreement with local galaxies and an inverse trend between metallicity and star-formation rate consistent with observations at z ˜ 2. The relation between stellar mass and metallicity (MZ relation) is similar to z˜ 3.5, but there are indications of it being slightly shallower, in particular for the young, Lyα-emitting galaxies. We show that, within a “bathtub” approach, a shallower MZ relation is expected in the case of a fast (exponential) build-up of stellar mass with an e-folding time of 100–200 Myr. Because of this fast evolution, the process of dust production and metal enrichment as a function of mass could be more stochastic in the first billion years of galaxy formation compared to later times.

  15. STAR FORMATION RATES AND STELLAR MASSES OF H{alpha} SELECTED STAR-FORMING GALAXIES AT z = 0.84: A QUANTIFICATION OF THE DOWNSIZING

    SciTech Connect

    Villar, Victor; Gallego, Jesus; Perez-Gonzalez, Pablo G.; Barro, Guillermo; Zamorano, Jaime; Noeske, Kai; Koo, David C. E-mail: j.gallego@fis.ucm.es E-mail: gbarro@fis.ucm.es E-mail: noeske@stsci.edu

    2011-10-10

    In this work we analyze the physical properties of a sample of 153 star-forming galaxies at z {approx} 0.84, selected by their H{alpha} flux with a narrowband filter. B-band luminosities of the objects are higher than those of local star-forming galaxies. Most of the galaxies are located in the blue cloud, though some objects are detected in the green valley and in the red sequence. After the extinction correction is applied, virtually all these red galaxies move to the blue sequence, unveiling their dusty nature. A check on the extinction law reveals that the typical extinction law for local starbursts is well suited for our sample but with E(B - V){sub stars} = 0.55 E(B - V){sub gas}. We compare star formation rates (SFRs) measured with different tracers (H{alpha}, far-ultraviolet, and infrared), finding that they agree within a factor of three after extinction correction. We find a correlation between the ratios SFR{sub FUV}/SFR{sub H{alpha}}, SFR{sub IR}/SFR{sub H{alpha}}, and the EW(H{alpha}) (i.e., weighted age), which accounts for part of the scatter. We obtain stellar mass estimations by fitting templates to multi-wavelength photometry. The typical stellar mass of a galaxy within our sample is {approx}10{sup 10} M{sub sun}. The SFR is correlated with stellar mass and the specific SFR decreases with it, indicating that massive galaxies are less affected by star formation processes than less massive ones. This result is consistent with the downsizing scenario. To quantify this downsizing we estimated the quenching mass M{sub Q} for our sample at z {approx} 0.84, finding that it declines from M{sub Q} {approx} 10{sup 12} M{sub sun} at z {approx} 0.84 to M{sub Q} {approx} 8 x 10{sup 10} M{sub sun} at the local universe.

  16. High-resolution Spectroscopy of a Young, Low-metallicity Optically Thin L = 0.02L* Star-forming Galaxy at z = 3.12

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; De Barros, S.; Cupani, G.; Karman, W.; Gronke, M.; Balestra, I.; Coe, D.; Mignoli, M.; Brusa, M.; Calura, F.; Caminha, G.-B.; Caputi, K.; Castellano, M.; Christensen, L.; Comastri, A.; Cristiani, S.; Dijkstra, M.; Fontana, A.; Giallongo, E.; Giavalisco, M.; Gilli, R.; Grazian, A.; Grillo, C.; Koekemoer, A.; Meneghetti, M.; Nonino, M.; Pentericci, L.; Rosati, P.; Schaerer, D.; Verhamme, A.; Vignali, C.; Zamorani, G.

    2016-04-01

    We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 ± 0.33 ({M}{UV}=-17.0), low-mass (≲{10}7{M}⊙ ), and compact (R eff = 62 pc) freshly star-forming galaxy at z = 3.1169 magnified (16×) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R=λ /dλ ˜ 3000{--}7400). We measured C iv λ 1548,1550, He ii λ 1640, O iii]λ 1661,1666, C iii]λ λ 1907,1909, Hβ, [O iii]λ λ 4959,5007 emission lines with {FWHM}≲ 50 km s-1 and (de-lensed) fluxes spanning the interval 1.0× {10}-19{--}2× {10}-18 erg s-1 cm-2 at signal-to-noise ratio (S/N) = 4-30. The double-peaked Lyα emission with {{Δ }}v({red}-{blue})=280(±7) km s-1 and de-lensed fluxes {2.4}({blue)}| {8.5}({red)}× {10}-18 erg s-1 cm-2 (S/N = {38}({blue)}| {110}({red)}) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O iii]λ 5007/ [O ii]λ 3727 \\gt \\quad 10 ratio. We detect C iv λ 1548,1550 resonant doublet in emission, each component with {FWHM}≲ 45 km s-1 and redshifted by +51(±10) km s-1 relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C iv λ 1548,1550 and He ii λ 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, β =-2.95+/- 0.20 ({F}λ ={λ }β ), consistent with a dust-free and young ≲20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H)\\quad \\lt \\quad 7.8. We are witnessing an early episode of star formation in which a relatively low N H i and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the James Webb Space

  17. High-resolution Spectroscopy of a Young, Low-metallicity Optically Thin L = 0.02L* Star-forming Galaxy at z = 3.12

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; De Barros, S.; Cupani, G.; Karman, W.; Gronke, M.; Balestra, I.; Coe, D.; Mignoli, M.; Brusa, M.; Calura, F.; Caminha, G.-B.; Caputi, K.; Castellano, M.; Christensen, L.; Comastri, A.; Cristiani, S.; Dijkstra, M.; Fontana, A.; Giallongo, E.; Giavalisco, M.; Gilli, R.; Grazian, A.; Grillo, C.; Koekemoer, A.; Meneghetti, M.; Nonino, M.; Pentericci, L.; Rosati, P.; Schaerer, D.; Verhamme, A.; Vignali, C.; Zamorani, G.

    2016-04-01

    We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 ± 0.33 ({M}{UV}=-17.0), low-mass (≲{10}7{M}ȯ ), and compact (R eff = 62 pc) freshly star-forming galaxy at z = 3.1169 magnified (16×) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R=λ /dλ ˜ 3000{--}7400). We measured C iv λ 1548,1550, He ii λ 1640, O iii]λ 1661,1666, C iii]λ λ 1907,1909, Hβ, [O iii]λ λ 4959,5007 emission lines with {FWHM}≲ 50 km s‑1 and (de-lensed) fluxes spanning the interval 1.0× {10}-19{--}2× {10}-18 erg s‑1 cm‑2 at signal-to-noise ratio (S/N) = 4–30. The double-peaked Lyα emission with {{Δ }}v({red}-{blue})=280(±7) km s‑1 and de-lensed fluxes {2.4}({blue)}| {8.5}({red)}× {10}-18 erg s‑1 cm‑2 (S/N = {38}({blue)}| {110}({red)}) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O iii]λ 5007/ [O ii]λ 3727 \\gt \\quad 10 ratio. We detect C iv λ 1548,1550 resonant doublet in emission, each component with {FWHM}≲ 45 km s‑1 and redshifted by +51(±10) km s‑1 relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C iv λ 1548,1550 and He ii λ 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, β =-2.95+/- 0.20 ({F}λ ={λ }β ), consistent with a dust-free and young ≲20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H)\\quad \\lt \\quad 7.8. We are witnessing an early episode of star formation in which a relatively low N H i and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the

  18. THE EVOLVING INTERSTELLAR MEDIUM OF STAR-FORMING GALAXIES SINCE z = 2 AS PROBED BY THEIR INFRARED SPECTRAL ENERGY DISTRIBUTIONS

    SciTech Connect

    Magdis, Georgios E.; Rigopoulou, D.; Daddi, E.; Bethermin, M.; Sargent, M.; Elbaz, D.; Pannella, M.; Dannerbauer, H.; Da Cunha, E.; Walter, F.; Charmandaris, V.; Hwang, H. S.

    2012-11-20

    Using data from the mid-infrared to millimeter wavelengths for individual galaxies and for stacked ensembles at 0.5 < z < 2, we derive robust estimates of dust masses (M {sub dust}) for main-sequence (MS) galaxies, which obey a tight correlation between star formation rate (SFR) and stellar mass (M {sub *}), and for starbursting galaxies that fall outside that relation. Exploiting the correlation of gas-to-dust mass with metallicity (M {sub gas}/M {sub dust}-Z), we use our measurements to constrain the gas content, CO-to-H{sub 2} conversion factors ({alpha}{sub CO}), and star formation efficiencies (SFE) of these distant galaxies. Using large statistical samples, we confirm that {alpha}{sub CO} and SFE are an order of magnitude higher and lower, respectively, in MS galaxies at high redshifts compared to the values of local galaxies with equivalently high infrared luminosities (L {sub IR} > 10{sup 12} L {sub Sun }). For galaxies within the MS, we show that the variations of specific star formation rates (sSFRs = SFR/M {sub *}) are driven by varying gas fractions. For relatively massive galaxies like those in our samples, we show that the hardness of the radiation field, (U), which is proportional to the dust-mass-weighted luminosity (L {sub IR}/M {sub dust}) and the primary parameter defining the shape of the IR spectral energy distribution (SED), is equivalent to SFE/Z. For MS galaxies with stellar mass log (M {sub *}/M {sub Sun }) {>=} 9.7 we measure this quantity, (U), showing that it does not depend significantly on either the stellar mass or the sSFR. This is explained as a simple consequence of the existing correlations between SFR-M {sub *}, M {sub *}-Z, and M {sub gas}-SFR. Instead, we show that (U) (or equally L {sub IR}/M {sub dust}) does evolve, with MS galaxies having harder radiation fields and thus warmer temperatures as redshift increases from z = 0 to 2, a trend that can also be understood based on the redshift evolution of the M {sub *}-Z and SFR

  19. UV Absorption Lines as Metallicity Estimator and the Metal Content of Star-forming Galaxies at z=5

    NASA Astrophysics Data System (ADS)

    Faisst, Andreas; Capak, Peter L.; Davidson, Iary; Kakazu, Yuko; Salvato, Mara; Laigle, Clotilde; Onodera, Masato; Masters, Daniel; COSMOS Team

    2016-01-01

    Probing the metal content of high redshift galaxies is essential to study their formation and evolution in the early universe. However, the spectral features used to measure the metallicity are shifted out of the wavelength range of current spectrographs at high-z and therefore alternative methods must be used.We measure the relation between four prominent UV absorption complexes and metallicity for more than 50 local galaxies and, by using a sample of more than 20 galaxies at z ~ 2 - 3, verify that this relation holds up to z ˜ 3. We then apply this method to a sample of ˜ 220 galaxies at 3.5 < z < 6.0 in COSMOS, for which unique UV spectra from DEIMOS and accurate stellar mass estimates from SPLASH are available. The z ~ 5 galaxies at 9 < log(m/M⊙) < 11 are characterized by 0.3 - 0.4 dex (in units of 12 + log(O/H)) lower metallicities than galaxies at z ˜ 2 but comparable to z ˜ 3 - 3.5 galaxies. In the same stellar mass range, we do not find a significant relation between stellar mass and metallicity (MZ relation), suggesting that the MZ relation at z ~ 5 is very shallow or breaking down. Since we verify a correlation between dust obscuration (measured by β) and UV absorption strength (i.e., metallicity), we argue that the process of dust production and metal enrichment in the first billion years of galaxy formation is more stochastic than at later times. Using a "bathtub" model approach, we find that an exponential build up of stellar mass within a short time of several 100 Myr can explain a shallow MZ relation at z ˜ 5. Furthermore, we find a weak anti-correlation between star-formation rates and UV absorption strength (i.e., metallicity), indicative of these galaxies being fueled by the inflow of pristine (metal-poor) gas. The galaxy sample presented in this work is unique to further test these scenarios using ALMA and the upcoming James Webb Space Telescope.

  20. Spectroscopic detections of C III] λ1909 Å at z ≃ 6-7: a new probe of early star-forming galaxies and cosmic reionization

    NASA Astrophysics Data System (ADS)

    Stark, Daniel P.; Richard, Johan; Charlot, Stéphane; Clément, Benjamin; Ellis, Richard; Siana, Brian; Robertson, Brant; Schenker, Matthew; Gutkin, Julia; Wofford, Aida

    2015-06-01

    Deep spectroscopic observations of z ≳ 6.5 galaxies have revealed a marked decline with increasing redshift in the detectability of Ly α emission. While this may offer valuable insight into the end of the reionization process, it presents a challenge to the detailed spectroscopic study of bright photometrically-selected distant sources now being found via deep Hubble Space Telescope imaging, and particularly those highly magnified sources viewed through foreground lensing clusters. In this paper, we demonstrate the validity of a new way forward via the detection of an alternative diagnostic line, C III] λ1909 Å, seen in spectroscopic exposures of a star-forming galaxy at zLyα = 6.029. We also report tentative detection of C III] λ1909 Å in a galaxy at zLyα = 7.213. The former 3.3σ detection is based on a 3.5 h XShooter spectrum of a bright (J125 = 25.2) gravitationally-lensed galaxy behind the cluster Abell 383. The latter 2.8σ detection is based on a 4.2 h MOSFIRE spectra of one of the most distant spectroscopically confirmed galaxies, GN-108036, with J140 = 25.2. Both targets were chosen for their continuum brightness and previously-known redshift (based on Ly α), ensuring that any C III] emission would be located in a favourable portion of the near-infrared sky spectrum. Since the availability of secure Ly α redshifts significantly narrows the wavelength range where C III] is sought, this increases confidence in these, otherwise, low-signal-to-noise ratio detections. We compare our C III] and Ly α equivalent widths in the context of those found at z ≃ 2 from earlier work and discuss the motivation for using lines other than Ly α to study galaxies in the reionization era.

  1. HERSCHEL DETECTION OF DUST EMISSION FROM UV-LUMINOUS STAR-FORMING GALAXIES AT 3.3 {approx}< z {approx}< 4.3

    SciTech Connect

    Lee, Kyoung-Soo; Alberts, Stacey; Pope, Alexandra; Atlee, David; Dey, Arjun; Jannuzi, Buell T.; Reddy, Naveen; Brown, Michael J. I.

    2012-10-20

    We report the Herschel/SPIRE detection of dust emission arising from UV-luminous (L {approx}> L*) star-forming galaxies at 3.3 {approx}< z {approx}< 4.3. Our sample of 1913 Lyman break galaxy (LBG) candidates is selected over an area of 5.3 deg{sup 2} in the Booetes field of the NOAO Deep Wide-Field Survey. This is one of the largest samples of UV-luminous galaxies at this epoch and enables an investigation of the bright end of the galaxy luminosity function. We divide our sample into three luminosity bins and stack the Herschel/SPIRE data to measure the average spectral energy distribution (SED) of LBGs at far-infrared (FIR) wavelengths. We find that these galaxies have average IR luminosities of (3-5) Multiplication-Sign 10{sup 11} L{sub Sun} and 60%-70% of their star formation obscured by dust. The FIR SEDs peak at {lambda}{sub rest} {approx}> 100 {mu}m suggesting dust temperatures (T{sub d} = 27-30 K) significantly colder than that of local galaxies of comparable IR luminosities. The observed IR-to-UV luminosity ratio (IRX {identical_to} L{sub IR}/L{sub UV}) is low ( Almost-Equal-To 3-4) compared with that observed for z Almost-Equal-To 2 LBGs (IRX{sub z{approx}2} Almost-Equal-To 7.1 {+-} 1.1). The correlation between the slope of the UV continuum and IRX for galaxies in the two lower luminosity bins suggests dust properties similar to those of local starburst galaxies. However, the galaxies in the highest luminosity bin appear to deviate from the local relation, suggesting that their dust properties may differ from those of their lower-luminosity and low-redshift counterparts. We speculate that the most UV-luminous galaxies at this epoch are being observed in a short-lived and young evolutionary phase.

  2. NEUTRAL HYDROGEN OPTICAL DEPTH NEAR STAR-FORMING GALAXIES AT z Almost-Equal-To 2.4 IN THE KECK BARYONIC STRUCTURE SURVEY

    SciTech Connect

    Rakic, Olivera; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.

    2012-06-01

    We study the interface between galaxies and the intergalactic medium by measuring the absorption by neutral hydrogen in the vicinity of star-forming galaxies at z Almost-Equal-To 2.4. Our sample consists of 679 rest-frame UV-selected galaxies with spectroscopic redshifts that have impact parameters <2 (proper) Mpc to the line of sight of one of the 15 bright, background QSOs and that fall within the redshift range of its Ly{alpha} forest. We present the first two-dimensional maps of the absorption around galaxies, plotting the median Ly{alpha} pixel optical depth as a function of transverse and line-of-sight separation from galaxies. The Ly{alpha} optical depths are measured using an automatic algorithm that takes advantage of all available Lyman series lines. The median optical depth, and hence the median density of atomic hydrogen, drops by more than an order of magnitude around 100 kpc, which is similar to the virial radius of the halos thought to host the galaxies. The median remains enhanced, at the >3{sigma} level, out to at least 2.8 Mpc (i.e., >9 comoving Mpc), but the scatter at a given distance is large compared with the median excess optical depth, suggesting that the gas is clumpy. Within 100 (200) kpc, and over {+-}165 km s{sup -1}, the covering fraction of gas with Ly{alpha} optical depth greater than unity is 100{sup +0}{sub -32}% (66% {+-} 16%). Absorbers with {tau}{sub Ly{alpha}} > 0.1 are typically closer to galaxies than random. The mean galaxy overdensity around absorbers increases with the optical depth and also as the length scale over which the galaxy overdensity is evaluated is decreased. Absorbers with {tau}{sub Ly{alpha}} {approx} 1 reside in regions where the galaxy number density is close to the cosmic mean on scales {>=}0.25 Mpc. We clearly detect two types of redshift space anisotropies. On scales <200 km s{sup -1}, or <1 Mpc, the absorption is stronger along the line of sight than in the transverse direction. This 'finger of God

  3. Physical properties from VLT spectroscopy of a sample of star-forming dwarf galaxies at intermediate redshift

    NASA Astrophysics Data System (ADS)

    Rodríguez-Muñoz, L.; Gallego, J.; Pérez-González, P. G.; Tresse, L.; Gil de Paz, A.; Barro, G.; Villar, V.; Le Fèvre, O.

    2013-05-01

    Dwarf galaxies remain as one of the most important and missing pieces of the great puzzle of formation and evolution of galaxies. Due to their low luminosities, their study has been mainly biased to the local universe or clusters, which hampers our knowledge of their redshift of formation and properties along the cosmological time, strong observational tests to recent models of formation and evolution of low-mass galaxies. Using the multiwavelength database RAINBOW, that provides photometric redshifts and masses estimations, we selected a representative sample of dwarf galaxies in the Chandra Deep Field-South (CDFS) within the redshift range 0.3galaxy sample.

  4. THE GREEN BANK TELESCOPE MAPS THE DENSE, STAR-FORMING GAS IN THE NEARBY STARBURST GALAXY M82

    SciTech Connect

    Kepley, Amanda A.; Frayer, David; Leroy, Adam K.; Usero, Antonio; Walter, Fabian

    2014-01-01

    Observations of the Milky Way and nearby galaxies show that dense molecular gas correlates with recent star formation, suggesting that the formation of this gas phase may help regulate star formation. A key test of this idea requires wide-area, high-resolution maps of dense molecular gas in galaxies to explore how local physical conditions drive dense gas formation, but these observations have been limited because of the faintness of dense gas tracers like HCN and HCO{sup +}. Here we demonstrate the power of the Robert C. Byrd Green Bank Telescope (GBT)—the largest single-dish millimeter radio telescope—for mapping dense gas in galaxies by presenting the most sensitive maps yet of HCN and HCO{sup +} in the starburst galaxy M82. The HCN and HCO{sup +} in the disk of this galaxy correlates with both recent star formation and more diffuse molecular gas and shows kinematics consistent with a rotating torus. The HCO{sup +} emission extending to the north and south of the disk is coincident with the outflow previously identified in CO and traces the eastern edge of the hot outflowing gas. The central starburst region has a higher ratio of star formation to dense gas than the outer regions, pointing to the starburst as a key driver of this relationship. These results establish that the GBT can efficiently map the dense molecular gas at 90 GHz in nearby galaxies, a capability that will increase further with the 16 element feed array under construction.

  5. New emerging results on molecular gas, stars, and dust at z ~ 2, as revealed by low star formation rate and low stellar mass star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Zamojski, Michel; Schaerer, Daniel; Combes, Françoise; Egami, Eiichi; Sklias, Panos; Swinbank, Mark A.; Richard, Johan; Rawle, Tim

    Recent CO surveys of star-forming galaxies (SFGs) at z ~ 2 have revolutionized our picture of massive galaxies. It is time to expand these studies toward the more common z ~ 2 SFGs with SFR < 40 M ⊙ yr-1 and M * < 2.5 × 1010 M⊙. We have derived molecular gas, stars, and dust in 8 such lensed SFGs. They extend the L IR-L'CO(1-0) distribution of massive z>1 SFGs and increase the spread of the SFG star formation efficiency (SFE). A single star formation relation is found when combining all existing CO-detected galaxies. Our low-M * SFGs also reveal a SFE decrease with M * as found locally. A rise of the molecular gas fraction (f gas) with redshift is observed up to z ~ 1.6, but it severely flattens toward higher redshifts. We provide the first insight into the f gas upturn at the low-M * end 109.4 < M */M⊙ < 1010 reaching f gas ~ 0.7, it is followed by a f gas decrease toward higher M *. Finally, we find a non-universal dust-to-gas ratio among local and high-redshift SFGs and starbursts with near-solar metallicities.

  6. On the lack of correlation between Mg II 2796, 2803 Å and Lyα emission in lensed star-forming galaxies

    SciTech Connect

    Rigby, J. R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.

    2014-07-20

    We examine the Mg II 2796, 2803 Å, Lyα, and nebular line emission in five bright star-forming galaxies at 1.66 < z < 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 Lyα 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 100-200 km s{sup –1}. When present, Lyα is even more redshifted. The reddest components of Mg II and Lyα emission have tails to 500-600 km s{sup –1}, implying a strong outflow. The lack of correlation in the Mg II and Lyα 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.

  7. SPT 0538–50: Physical conditions in the interstellar medium of a strongly lensed dusty star-forming galaxy at z = 2.8

    SciTech Connect

    Bothwell, M. S.; Aguirre, J. E.; Chapman, S. C.; Marrone, D. P.; Vieira, J. D.; Bock, J. J.; Downes, T. P.; Ashby, M. L. N.; Aravena, M.; De Breuck, C.; Gullberg, B.; Benson, B. A.; Carlstrom, J. E.; Crawford, T. M.; Bradford, C. M.; Brodwin, M.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; and others

    2013-12-10

    We present observations of SPT-S J053816–5030.8, a gravitationally lensed dusty star-forming galaxy (DSFG) at z = 2.7817 that was first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538–50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538–50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, the Very Large Telescope, ATCA, APEX, and the Submillimeter Array. We use high-resolution imaging from the Hubble Space Telescope to de-blend SPT 0538–50, separating DSFG emission from that of the foreground lens. Combined with a source model derived from ALMA imaging (which suggests a magnification factor of 21 ± 4), we derive the intrinsic properties of SPT 0538–50, including the stellar mass, far-IR luminosity, star formation rate, molecular gas mass, and—using molecular line fluxes—the excitation conditions within the interstellar medium. The derived physical properties argue that we are witnessing compact, merger-driven star formation in SPT 0538–50 similar to local starburst galaxies and unlike that seen in some other DSFGs at this epoch.

  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. Metal-poor, Cool Gas in the Circumgalactic Medium of a z = 2.4 Star-forming Galaxy: Direct Evidence for Cold Accretion?

    NASA Astrophysics Data System (ADS)

    Crighton, Neil H. M.; Hennawi, Joseph F.; Prochaska, J. Xavier

    2013-10-01

    In our current galaxy formation paradigm, high-redshift galaxies are predominantly fueled by accretion of cool, metal-poor gas from the intergalactic medium. Hydrodynamical simulations predict that this material should be observable in absorption against background sightlines within a galaxy's virial radius, as optically thick Lyman limit systems (LLSs) with low metallicities. Here we report the discovery of exactly such a strong metal-poor absorber at an impact parameter R = 58 kpc from a star-forming galaxy at z = 2.44. Besides strong neutral hydrogen (N_{{H}^0}=10^{19.50+/- 0.16}\\, cm^{-2}) we detect neutral deuterium and oxygen, allowing a precise measurement of the metallicity: log10(Z/Z ⊙) = -2.0 ± 0.17, or (7-15) × 10-3 solar. Furthermore, the narrow deuterium linewidth requires a cool temperature <20,000 K. Given the striking similarities between this system and the predictions of simulations, we argue that it represents the direct detection of a high-redshift cold-accretion stream. The low-metallicity gas cloud is a single component of an absorption system exhibiting a complex velocity, ionization, and enrichment structure. Two other components have metallicities >0.1 solar, 10 times larger than the metal-poor component. We conclude that the photoionized circumgalactic medium (CGM) of this galaxy is highly inhomogeneous: the majority of the gas is in a cool, metal-poor and predominantly neutral phase, but the majority of the metals are in a highly ionized phase exhibiting weak neutral hydrogen absorption but strong metal absorption. If such inhomogeneity is common, then high-resolution spectra and detailed ionization modeling are critical to accurately appraise the distribution of metals in the high-redshift CGM. .

  10. The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen Gas in the Outskirts of Star-forming Galaxies from z ~ 1 to z ~3

    NASA Astrophysics Data System (ADS)

    Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia

    2016-07-01

    Current observational evidence suggests that the star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in damped Lyα systems (DLAs) at z˜ 3 is more than 10 times lower than predicted by the Kennicutt-Schmidt (KS) relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z ˜ 1, z ˜ 2, and z˜ 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies’ outskirts. We find that the SFR efficiency of H i gas at z\\gt 1 is ˜1%-3% of that predicted by the KS relation. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency with redshift. Our analysis instead suggests that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a secondary effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies and local dwarf galaxies.

  11. METAL-POOR, COOL GAS IN THE CIRCUMGALACTIC MEDIUM OF A z = 2.4 STAR-FORMING GALAXY: DIRECT EVIDENCE FOR COLD ACCRETION?

    SciTech Connect

    Crighton, Neil H. M.; Hennawi, Joseph F.; Prochaska, J. Xavier

    2013-10-20

    In our current galaxy formation paradigm, high-redshift galaxies are predominantly fueled by accretion of cool, metal-poor gas from the intergalactic medium. Hydrodynamical simulations predict that this material should be observable in absorption against background sightlines within a galaxy's virial radius, as optically thick Lyman limit systems (LLSs) with low metallicities. Here we report the discovery of exactly such a strong metal-poor absorber at an impact parameter R = 58 kpc from a star-forming galaxy at z = 2.44. Besides strong neutral hydrogen (N{sub H{sup 0}}=10{sup 19.50±0.16} cm{sup -2}) we detect neutral deuterium and oxygen, allowing a precise measurement of the metallicity: log{sub 10}(Z/Z {sub ☉}) = –2.0 ± 0.17, or (7-15) × 10{sup –3} solar. Furthermore, the narrow deuterium linewidth requires a cool temperature <20,000 K. Given the striking similarities between this system and the predictions of simulations, we argue that it represents the direct detection of a high-redshift cold-accretion stream. The low-metallicity gas cloud is a single component of an absorption system exhibiting a complex velocity, ionization, and enrichment structure. Two other components have metallicities >0.1 solar, 10 times larger than the metal-poor component. We conclude that the photoionized circumgalactic medium (CGM) of this galaxy is highly inhomogeneous: the majority of the gas is in a cool, metal-poor and predominantly neutral phase, but the majority of the metals are in a highly ionized phase exhibiting weak neutral hydrogen absorption but strong metal absorption. If such inhomogeneity is common, then high-resolution spectra and detailed ionization modeling are critical to accurately appraise the distribution of metals in the high-redshift CGM.

  12. The SCUBA-2 Cosmology Legacy Survey: galaxies in the deep 850 μm survey, and the star-forming `main sequence'

    NASA Astrophysics Data System (ADS)

    Koprowski, M. P.; Dunlop, J. S.; Michałowski, M. J.; Roseboom, I.; Geach, J. E.; Cirasuolo, M.; Aretxaga, I.; Bowler, R. A. A.; Banerji, M.; Bourne, N.; Coppin, K. E. K.; Chapman, S.; Hughes, D. H.; Jenness, T.; McLure, R. J.; Symeonidis, M.; Werf, P. van der

    2016-06-01

    We investigate the properties of the galaxies selected from the deepest 850-μm survey undertaken to date with (Submillimetre Common-User Bolometer Array 2) SCUBA-2 on the James Clerk Maxwell Telescope as part of the SCUBA-2 Cosmology Legacy Survey. A total of 106 sources (>5σ) were uncovered at 850 μm from an area of ≃150 arcmin2 in the centre of the COSMOS/UltraVISTA/Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field, imaged to a typical depth of σ850 ≃ 0.25 mJy. We utilize the available multifrequency data to identify galaxy counterparts for 80 of these sources (75 per cent), and to establish the complete redshift distribution for this sample, yielding bar{z} = 2.38± 0.09. We have also been able to determine the stellar masses of the majority of the galaxy identifications, enabling us to explore their location on the star formation rate:stellar mass (SFR:M*) plane. Crucially, our new deep 850-μm-selected sample reaches flux densities equivalent to SFR ≃ 100 M⊙ yr-1, enabling us to confirm that sub-mm galaxies form the high-mass end of the `main sequence' (MS) of star-forming galaxies at z > 1.5 (with a mean specific SFR of sSFR = 2.25 ± 0.19 Gyr-1 at z ≃ 2.5). Our results are consistent with no significant flattening of the MS towards high masses at these redshifts. However, our results add to the growing evidence that average sSFR rises only slowly at high redshift, resulting in log10sSFR being an apparently simple linear function of the age of the Universe.

  13. THE ABUNDANCE OF STAR-FORMING GALAXIES IN THE REDSHIFT RANGE 8.5-12: NEW RESULTS FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN

    SciTech Connect

    Ellis, Richard S.; Schenker, Matthew A.; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Rogers, Alexander B.; Curtis-Lake, Emma; Cirasuolo, Michele; Robertson, Brant E.; Schneider, Evan; Stark, Daniel P.; Ono, Yoshiaki; Ouchi, Masami; Koekemoer, Anton; Charlot, Stephane; Furlanetto, Steven R.

    2013-01-20

    We present the results of the deepest search to date for star-forming galaxies beyond a redshift z {approx_equal} 8.5 utilizing a new sequence of near-infrared Wide-Field Camera 3 (WFC3/IR) images of the Hubble Ultra Deep Field (UDF). This 'UDF12' campaign completed in 2012 September doubles the earlier exposures with WFC3/IR in this field and quadruples the exposure in the key F105W filter used to locate such distant galaxies. Combined with additional imaging in the F140W filter, the fidelity of high-redshift candidates is greatly improved. Using spectral energy distribution fitting techniques on objects selected from a deep multi-band near-infrared stack, we find seven promising z > 8.5 candidates. As none of the previously claimed UDF candidates with 8.5 < z < 10 are confirmed by our deeper multi-band imaging, our campaign has transformed the measured abundance of galaxies in this redshift range. Although we recover the candidate UDFj-39546284 (previously proposed at z = 10.3), it is undetected in the newly added F140W image, implying that it lies at z = 11.9 or is an intense emission line galaxy at z {approx_equal} 2.4. Although no physically plausible model can explain the required line intensity given the lack of Ly{alpha} or broadband UV signal, without an infrared spectrum we cannot rule out an exotic interloper. Regardless, our robust z {approx_equal} 8.5-10 sample demonstrates a luminosity density that continues the smooth decline observed over 6 < z < 8. Such continuity has important implications for models of cosmic reionization and future searches for z >10 galaxies with James Webb Space Telescope.

  14. Ly{alpha} ESCAPE FROM z {approx} 0.03 STAR-FORMING GALAXIES: THE DOMINANT ROLE OF OUTFLOWS

    SciTech Connect

    Wofford, Aida; Leitherer, Claus; Salzer, John

    2013-03-10

    The usefulness of H I Ly{alpha} photons for characterizing star formation in the distant universe is limited by our understanding of the astrophysical processes that regulate their escape from galaxies. These processes can only be observed in detail out to a few Multiplication-Sign 100 Mpc. Past nearby (z < 0.3) spectroscopic studies are based on small samples and/or kinematically unresolved data. Taking advantage of the high sensitivity of Hubble Space Telescope's Cosmic Origins Spectrograph (COS), we observed the Ly{alpha} lines of 20 H{alpha}-selected galaxies located at =0.03. The galaxies cover a broad range of luminosity, oxygen abundance, and reddening. In this paper, we characterize the observed Ly{alpha} lines and establish correlations with fundamental galaxy properties. We find seven emitters. These host young ({<=}10 Myr) stellar populations have rest-frame equivalent widths in the range 1-12 A, and have Ly{alpha} escape fractions within the COS aperture in the range 1%-12%. One emitter has a double-peaked Ly{alpha} with peaks 370 km s{sup -1} apart and a stronger blue peak. Excluding this object, the emitters have Ly{alpha} and O I {lambda}1302 offsets from H{alpha} in agreement with expanding-shell models and Lyman break galaxies observations. The absorbers have offsets that are almost consistent with a static medium. We find no one-to-one correspondence between Ly{alpha} emission and age, metallicity, or reddening. Thus, we confirm that Ly{alpha} is enhanced by outflows and is regulated by the dust and H I column density surrounding the hot stars.

  15. Lyα and CIII] Emission in z = 7 - 9 Galaxies: Accelerated Reionization Around Luminous Star Forming Systems?

    NASA Astrophysics Data System (ADS)

    Stark, Daniel P.; Ellis, Richard S.; Charlot, Stéphane; Chevallard, Jacopo; Tang, Mengtao; Belli, Sirio; Zitrin, Adi; Mainali, Ramesh; Gutkin, Julia; Vidal-García, Alba; Bouwens, Rychard; Oesch, Pascal

    2016-09-01

    We discuss new Keck/MOSFIRE spectroscopic observations of four luminous galaxies at z ≃ 7 - 9 selected to have intense optical line emission by Roberts-Borsani et al. (2016). Previous follow-up has revealed Lyα in two of the four galaxies. Our new MOSFIRE observations confirm that Lyα is present in the entire sample. We detect Lyα emission in the galaxy COS-zs7-1, confirming its redshift as zLyα = 7.154, and we detect Lyα in EGS-zs8-2 at zLyα = 7.477, verifying an earlier tentative detection. The ubiquity of Lyα in this sample is puzzling given that the IGM is expected to be significantly neutral over 7 < z < 9. To investigate this result in more detail, we have initiated a campaign to target UV metal lines in the four Lyα emitters as a probe of both the ionizing field and the Lyα velocity offset at early times. Here we present the detection of CIII] emission in the z = 7.73 galaxy EGS-zs8-1, requiring an intense radiation field and moderately low metallicity. We argue that the radiation field is likely to affect the local environment, increasing the transmission of Lyα through the galaxy. Moreover, the centroid of CIII] indicates that Lyα is redshifted by 340 km sec-1. This velocity offset is larger than that seen in less luminous systems, providing an explanation for the transmission of Lyα emission through the IGM. Since the transmission is further enhanced by the likelihood that such systems are also situated in large ionized bubbles, the visibility of Lyα at z > 7 is expected to be strongly luminosity-dependent, with transmission accelerated in systems with intense star formation.

  16. The MOSDEF Survey: The Strong Agreement between Hα and UV-to-FIR Star Formation Rates for z ~ 2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Shivaei, Irene; Kriek, Mariska; Reddy, Naveen A.; Shapley, Alice E.; Barro, Guillermo; Conroy, Charlie; Coil, Alison L.; Freeman, William R.; Mobasher, Bahram; Siana, Brian; Sanders, Ryan; Price, Sedona H.; Azadi, Mojegan; Pasha, Imad; Inami, Hanae

    2016-04-01

    We present the first direct comparison between Balmer line and panchromatic spectral energy distribution (SED)-based star formation rates (SFRs) for z˜ 2 galaxies. For this comparison, we used 17 star-forming galaxies selected from the MOSFIRE Deep Evolution Field (MOSDEF) survey, with 3σ detections for Hα and at least two IR bands (Spitzer/MIPS 24 μm and Herschel/PACS 100 and 160 μm, and in some cases Herschel/SPIRE 250, 350, and 500 μm). The galaxies have total IR (8-1000 μm) luminosities of ˜ 1011.4-1012.4 L⊙ and SFRs of ˜ 30-250 M⊙ yr-1. We fit the UV-to-far-IR SEDs with flexible stellar population synthesis (FSPS) models—which include both stellar and dust emission—and compare the inferred SFRs with the SFR(Hα, Hβ) values corrected for dust attenuation using Balmer decrements. The two SFRs agree with a scatter of 0.17 dex. Our results imply that the Balmer decrement accurately predicts the obscuration of the nebular lines and can be used to robustly calculate SFRs for star-forming galaxies at z˜ 2 with SFRs up to ˜ 200 M⊙ yr-1. We also use our data to assess SFR indicators based on modeling the UV-to-mid-IR SEDs or by adding SFR(UV) and SFR(IR), for which the latter is based on the mid-IR only or on the full IR SED. All these SFRs show a poorer agreement with SFR(Hα, Hβ) and in some cases large systematic biases are observed. Finally, we show that the SFR and dust attenuation derived from the UV-to-near-IR SED alone are unbiased when assuming a delayed exponentially declining star formation history. Based on observations made with 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.

  17. Sub-kiloparsec ALMA Imaging of Compact Star-forming Galaxies at z ~ 2.5: Revealing the Formation of Dense Galactic Cores in the Progenitors of Compact Quiescent Galaxies

    NASA Astrophysics Data System (ADS)

    Barro, G.; Kriek, M.; Pérez-González, P. G.; Trump, J. R.; Koo, D. C.; Faber, S. M.; Dekel, A.; Primack, J. R.; Guo, Y.; Kocevski, D. D.; Muñoz-Mateos, J. C.; Rujoparkarn, W.; Seth, K.

    2016-08-01

    We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm dust continuum maps of six massive, compact, dusty star-forming galaxies at z ˜ 2.5. These galaxies are selected for their small rest-frame optical sizes ({r}{{e,F160W}}˜ 1.6 kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z ˜ 2. The deep observations yield high far-infrared (FIR) luminosities of {L}{{IR}}={10}12.3-12.8 {L}ȯ and star formation rates (SFRs) of SFR = 200–700 M ⊙ yr‑1, consistent with those of typical star-forming “main sequence” galaxies. The high spatial resolution (FWHM ˜ 0.″12–0.″18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR–SFR overwhelmingly dominates the bolometric SFR up to r ˜ 5 kpc, by a factor of over 100× from the unobscured UV–SFR. Furthermore, the effective radius of the mean SFR profile ({r}{{e,SFR}}˜ 1 kpc) is ˜30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Δt = ±100 Myr, is a 4× increase of the stellar mass density within the central 1 kpc and a 1.6× decrease of the half-mass–radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

  18. Sub-kiloparsec ALMA Imaging of Compact Star-forming Galaxies at z ~ 2.5: Revealing the Formation of Dense Galactic Cores in the Progenitors of Compact Quiescent Galaxies

    NASA Astrophysics Data System (ADS)

    Barro, G.; Kriek, M.; Pérez-González, P. G.; Trump, J. R.; Koo, D. C.; Faber, S. M.; Dekel, A.; Primack, J. R.; Guo, Y.; Kocevski, D. D.; Muñoz-Mateos, J. C.; Rujopakarn, W.; Seth, K.

    2016-08-01

    We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm dust continuum maps of six massive, compact, dusty star-forming galaxies at z ˜ 2.5. These galaxies are selected for their small rest-frame optical sizes ({r}{{e,F160W}}˜ 1.6 kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z ˜ 2. The deep observations yield high far-infrared (FIR) luminosities of {L}{{IR}}={10}12.3-12.8 {L}⊙ and star formation rates (SFRs) of SFR = 200-700 M ⊙ yr-1, consistent with those of typical star-forming “main sequence” galaxies. The high spatial resolution (FWHM ˜ 0.″12-0.″18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR-SFR overwhelmingly dominates the bolometric SFR up to r ˜ 5 kpc, by a factor of over 100× from the unobscured UV-SFR. Furthermore, the effective radius of the mean SFR profile ({r}{{e,SFR}}˜ 1 kpc) is ˜30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Δt = ±100 Myr, is a 4× increase of the stellar mass density within the central 1 kpc and a 1.6× decrease of the half-mass-radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

  19. WFC3 GRISM CONFIRMATION OF THE DISTANT CLUSTER Cl J1449+0856 AT (z) = 2.00: QUIESCENT AND STAR-FORMING GALAXY POPULATIONS

    SciTech Connect

    Gobat, R.; Strazzullo, V.; Daddi, E.; Renzini, A.; Finoguenov, A.; Cimatti, A.; Scarlata, C.; Arimoto, N.

    2013-10-10

    We present deep Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) slitless spectroscopic observations of the distant cluster Cl J1449+0856. These cover a single pointing with 18 orbits of G141 spectroscopy and F140W imaging, allowing us to derive secure redshifts down to M{sub 140} ∼ 25.5 AB and 3σ line fluxes of ∼5 × 10{sup –18} erg s{sup –1} cm{sup –2}. In particular, we were able to spectroscopically confirm 12 early-type galaxies (ETGs) in the field up to z ∼ 3, 6 of which are in the cluster core, which represents the first direct spectroscopic confirmation of quiescent galaxies in a z = 2 cluster environment. With 140 redshifts in a ∼6 arcmin{sup 2} field, we can trace the spatial and redshift galaxy distribution in the cluster core and background field. We find two strong peaks at z = 2.00 and z = 2.07, where only one was seen in our previously published ground-based data. Due to the spectroscopic confirmation of the cluster ETGs, we can now reevaluate the redshift of Cl J1449+0856 at z = 2.00, rather than z = 2.07, with the background overdensity being revealed to be sparse and {sup s}heet{sup -}like. This presents an interesting case of chance alignment of two close yet unrelated structures, each one preferentially selected by different observing strategies. With 6 quiescent or early-type spectroscopic members and 20 star-forming ones, Cl J1449+0856 is now reliably confirmed to be at z = 2.00. The identified members can now allow for a detailed study of galaxy properties in the densest environment at z = 2.

  20. Probing star formation in the dense environments of z ˜ 1 lensing haloes aligned with dusty star-forming galaxies detected with the South Pole Telescope

    NASA Astrophysics Data System (ADS)

    Welikala, N.; Béthermin, M.; Guery, D.; Strandet, M.; Aird, K. A.; Aravena, M.; Ashby, M. L. N.; Bothwell, M.; Beelen, A.; Bleem, L. E.; de Breuck, C.; Brodwin, M.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; Dole, H.; Doré, O.; Everett, W.; Flores-Cacho, I.; Gonzalez, A. H.; González-Nuevo, J.; Greve, T. R.; Gullberg, B.; Hezaveh, Y. D.; Holder, G. P.; Holzapfel, W. L.; Keisler, R.; Lagache, G.; Ma, J.; Malkan, M.; Marrone, D. P.; Mocanu, L. M.; Montier, L.; Murphy, E. J.; Nesvadba, N. P. H.; Omont, A.; Pointecouteau, E.; Puget, J. L.; Reichardt, C. L.; Rotermund, K. M.; Scott, D.; Serra, P.; Spilker, J. S.; Stalder, B.; Stark, A. A.; Story, K.; Vanderlinde, K.; Vieira, J. D.; Weiß, A.

    2016-01-01

    We probe star formation in the environments of massive (˜1013 M⊙) dark matter haloes at redshifts of z ˜ 1. This star formation is linked to a submillimetre clustering signal which we detect in maps of the Planck High Frequency Instrument that are stacked at the positions of a sample of high redshift (z > 2) strongly lensed dusty star-forming galaxies (DSFGs) selected from the South Pole Telescope (SPT) 2500 deg2 survey. The clustering signal has submillimetre colours which are consistent with the mean redshift of the foreground lensing haloes (z ˜ 1). We report a mean excess of star formation rate (SFR) compared to the field, of (2700 ± 700) M⊙ yr-1 from all galaxies contributing to this clustering signal within a radius of 3.5 arcmin from the SPT DSFGs. The magnitude of the Planck excess is in broad agreement with predictions of a current model of the cosmic infrared background. The model predicts that 80 per cent of the excess emission measured by Planck originates from galaxies lying in the neighbouring haloes of the lensing halo. Using Herschel maps of the same fields, we find a clear excess, relative to the field, of individual sources which contribute to the Planck excess. The mean excess SFR compared to the field is measured to be (370 ± 40) M⊙ yr-1 per resolved, clustered source. Our findings suggest that the environments around these massive z ˜ 1 lensing haloes host intense star formation out to about 2 Mpc. The flux enhancement due to clustering should also be considered when measuring flux densities of galaxies in Planck data.

  1. The very wide-field gzK Galaxy Survey - II. The relationship between star-forming galaxies at z ˜ 2 and their host haloes based upon HOD modelling

    NASA Astrophysics Data System (ADS)

    Ishikawa, Shogo; Kashikawa, Nobunari; Hamana, Takashi; Toshikawa, Jun; Onoue, Masafusa

    2016-05-01

    We present the results of an halo occupation distribution (HOD) analysis of star-forming galaxies at z ˜ 2. We obtained high-quality angular correlation functions based on a large sgzK sample, which enabled us to carry out the HOD analysis. The mean halo mass and the HOD mass parameters are found to increase monotonically with increasing K-band magnitude, suggesting that more luminous galaxies reside in more massive dark haloes. The luminosity dependence of the HOD mass parameters was found to be the same as in the local Universe; however, the masses were larger than in the local Universe over all ranges of magnitude. This implies that galaxies at z ˜ 2 tend to form in more massive dark haloes than in the local Universe, a process known as downsizing. By analysing the dark halo mass evolution using the extended Press-Schechter formalism and the number evolution of satellite galaxies in a dark halo, we find that faint Lyman break galaxies at z ˜ 4 could evolve into the faintest sgzKs (22.0 < K ≤ 23.0) at z ˜ 2 and into the Milky-Way-like galaxies or elliptical galaxies in the local Universe, whereas the most luminous sgzKs (18.0 ≤ K ≤ 21.0) could evolve into the most massive systems in the local Universe. The stellar-to-halo mass ratio (SHMR) of the sgzKs was found to be consistent with the prediction of the model, except that the SHMR of the faintest sgzKs was smaller than the prediction at z ˜ 2. This discrepancy may be explained by the confinement of our samples to star-forming galaxies.

  2. THE ADVANCED CAMERA FOR SURVEYS NEARBY GALAXY SURVEY TREASURY. VI. THE ANCIENT STAR-FORMING DISK OF NGC 404

    SciTech Connect

    Williams, Benjamin F.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Stilp, Adrienne; Dolphin, Andrew; Seth, Anil C.; Weisz, Daniel; Skillman, Evan E-mail: jd@astro.washington.ed E-mail: roskar@astro.washington.ed E-mail: aseth@cfa.harvard.ed E-mail: skillman@astro.umn.ed

    2010-06-10

    We present HST/WFPC2 observations across the disk of the nearby isolated dwarf S0 galaxy NGC 404, which hosts an extended gas disk. The locations of our fields contain a roughly equal mixture of bulge and disk stars. All of our resolved stellar photometry reaches m {sub F814W} = 26 (M {sub F814W} = -1.4), which covers 2.5 mag of the red giant branch and main-sequence stars with ages <300 Myr. Our deepest field reaches m {sub F814W} = 27.2 (M {sub F814W} = -0.2), sufficient to resolve the red clump and main-sequence stars with ages <500 Myr. Although we detect trace amounts of star formation at times more recent than 10 Gyr ago for all fields, the proportion of red giant stars to asymptotic giants and main-sequence stars suggests that the disk is dominated by an ancient (>10 Gyr) population. Detailed modeling of the color-magnitude diagram suggests that {approx}70% of the stellar mass in the NGC 404 disk formed by z {approx} 2 (10 Gyr ago) and at least {approx}90% formed prior to z {approx} 1 (8 Gyr ago). These results indicate that the stellar populations of the NGC 404 disk are on average significantly older than those of other nearby disk galaxies, suggesting that early- and late-type disks may have different long-term evolutionary histories, not simply differences in their recent star formation rates. Comparisons of the spatial distribution of the young stellar mass and FUV emission in Galaxy Evolution Explorer images show that the brightest FUV regions contain the youngest stars, but that some young stars (<160 Myr) lie outside of these regions. FUV luminosity appears to be strongly affected by both age and stellar mass within individual regions. Finally, we use our measurements to infer the relationship between the star formation rate and the gas density of the disk at previous epochs. We find that most of the history of the NGC 404 disk is consistent with star formation that has decreased with the gas density according to the Schmidt law. However, {approx} 0

  3. Optical depth ratios and metal-line absorption around z≈2.3 star-forming galaxies: insights from observations and simulations

    NASA Astrophysics Data System (ADS)

    Turner, Monica; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison

    2015-01-01

    We study metal-line absorption around 854 z≈2.3 star-forming galaxies taken from the Keck Baryonic Structure Survey. The galaxies in this survey lie in the fields of 15 hyper-luminous background QSOs, with galaxy impact parameters ranging from 35 proper kpc (pkpc) to 2 proper Mpc (pMpc). Using the pixel optical depth technique, we present the first galaxy-centered 2-D maps of the median absorption by OVI, NV, CIV, CIII, and SiIV, as well as updated results for HI. At small galactocentric radii we detect a strong enhancement of the absorption relative to randomly located regions that extend out to at least 180 pkpc in the transverse direction, and ±240 km s-1 along the line-of-sight (LOS, ˜1 pMpc in the case of pure Hubble flow) for all ions except NV. Limiting the sample to the 340 galaxies with redshifts measured from nebular emission lines does not decrease the extent of the enhancement along the LOS compared to that in the transverse direction, which rules out redshift errors as the source of the observed redshift-space anisotropy and implies that we have detected the signature of gas peculiar velocities from infall, outflows, or virial motions. Looking next at optical depth ratios, we isolate pixel pairs at small galactocentric distances (within 180 pkpc in the transverse direction and 170 km s-1 along the LOS) and find that the optical depth of OVI at fixed HI is enhanced with respect to the full sample. Comparison with CLOUDY models, and assuming photoionisation, results in nearly solar metallicities at intergalactic overdensities, which we consider to be unphysical. Invoking collisional ionisation, we are able to place a lower limit on [O/H] of ˜1/100th solar, and conclude that we are likely probing collisionally ionised gas near galaxies. Finally, we turn to the EAGLE cosmological hydrodynamical simulations to interpret our results, and furthermore to study the evolution of the column density profiles as a function of impact parameter for different

  4. EVIDENCE OF VERY LOW METALLICITY AND HIGH IONIZATION STATE IN A STRONGLY LENSED, STAR-FORMING DWARF GALAXY AT z = 3.417

    SciTech Connect

    Amorín, R.; Grazian, A.; Castellano, M.; Pentericci, L.; Fontana, A.; Sommariva, V.; Merlin, E.; Van der Wel, A.; Maseda, M.

    2014-06-10

    We investigate the gas-phase metallicity and Lyman continuum (LyC) escape fraction of a strongly gravitationally lensed, extreme emission-line galaxy at z = 3.417, J1000+0221S, recently discovered by the CANDELS team. We derive ionization- and metallicity-sensitive emission-line ratios from H+K band Large Binocular Telescope (LBT)/LUCI medium resolution spectroscopy. J1000+0221S shows high ionization conditions, as evidenced by its enhanced [O III]/[O II] and [O III]/Hβ ratios. Strong-line methods based on the available line ratios suggest that J1000+0221S is an extremely metal-poor galaxy, with a metallicity of 12+log (O/H) < 7.44 (Z < 0.05 Z {sub ☉}), placing it among the most metal-poor star-forming galaxies at z ≳ 3 discovered so far. In combination with its low stellar mass (2 × 10{sup 8} M {sub ☉}) and high star formation rate (5 M {sub ☉} yr{sup –1}), the metallicity of J1000+0221S is consistent with the extrapolation of the mass-metallicity relation traced by Lyman-break galaxies at z ≳ 3 to low masses, but it is 0.55 dex lower than predicted by the fundamental metallicity relation at z ≲ 2.5. These observations suggest a rapidly growing galaxy, possibly fed by massive accretion of pristine gas. Additionally, deep LBT/LBC photometry in the UGR bands are used to derive a limit to the LyC escape fraction, thus allowing us to explore for the first time the regime of sub-L* galaxies at z > 3. We find a 1σ upper limit to the escape fraction of 23%, which adds a new observational constraint to recent theoretical models predicting that sub-L* galaxies at high-z have high escape fractions and thus are the responsible for the reionization of the universe.

  5. BLAST: CORRELATIONS IN THE COSMIC FAR-INFRARED BACKGROUND AT 250, 350, AND 500 mum REVEAL CLUSTERING OF STAR-FORMING GALAXIES

    SciTech Connect

    Viero, Marco P.; Martin, Peter G.; Netterfield, Calvin B.; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Moncelsi, Lorenzo; Pascale, Enzo; Bock, James J.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Devlin, Mark J.; Klein, Jeff; Gundersen, Joshua O.; Hughes, David H.; MacTavish, Carrie J.; Negrello, Mattia; Olmi, Luca

    2009-12-20

    We detect correlations in the cosmic far-infrared background due to the clustering of star-forming galaxies in observations made with the Balloon-borne Large Aperture Submillimeter Telescope, at 250, 350, and 500 mum. We perform jackknife and other tests to confirm the reality of the signal. The measured correlations are well fitted by a power law over scales of 5'-25', with DELTAI/I = 15.1% +- 1.7%. We adopt a specific model for submillimeter sources in which the contribution to clustering comes from sources in the redshift ranges 1.3 <= z <= 2.2, 1.5 <= z <= 2.7, and 1.7 <= z <= 3.2, at 250, 350, and 500 mum, respectively. With these distributions, our measurement of the power spectrum, P(k{sub t}heta), corresponds to linear bias parameters, b = 3.8 +- 0.6, 3.9 +- 0.6, and 4.4 +- 0.7, respectively. We further interpret the results in terms of the halo model, and find that at the smaller scales, the simplest halo model fails to fit our results. One way to improve the fit is to increase the radius at which dark matter halos are artificially truncated in the model, which is equivalent to having some star-forming galaxies at z >= 1 located in the outskirts of groups and clusters. In the context of this model, we find a minimum halo mass required to host a galaxy is log(M{sub min}/M{sub sun}) = 11.5{sup +0.4}{sub -0.1}, and we derive effective biases b{sub eff} = 2.2 +- 0.2, 2.4 +- 0.2, and 2.6 +- 0.2, and effective masses log(M{sub eff}/M{sub odot})=12.9+-0.3, 12.8 +- 0.2, and 12.7 +- 0.2, at 250, 350 and 500 mum, corresponding to spatial correlation lengths of r{sub 0} = 4.9, 5.0, and 5.2+-0.7 h{sup -1}Mpc, respectively. Finally, we discuss implications for clustering measurement strategies with Herschel and Planck.

  6. ANGULAR POWER SPECTRA OF THE MILLIMETER-WAVELENGTH BACKGROUND LIGHT FROM DUSTY STAR-FORMING GALAXIES WITH THE SOUTH POLE TELESCOPE

    SciTech Connect

    Hall, N. R.; Knox, L.; Keisler, R.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Reichardt, C. L.; Cho, H.-M.; George, E. M.; Holzapfel, W. L.; Ade, P. A. R.; Aird, K. A.; Hrubes, J. D.; De Haan, T.; Dobbs, M. A.; Holder, G. P.; Halverson, N. W.

    2010-08-01

    We use data from the first 100 deg{sup 2} field observed by the South Pole Telescope (SPT) in 2008 to measure the angular power spectrum of temperature anisotropies contributed by the background of dusty star-forming galaxies (DSFGs) at millimeter wavelengths. From the auto- and cross-correlation of 150 and 220 GHz SPT maps, we significantly detect both Poisson distributed and, for the first time at millimeter wavelengths, clustered components of power from a background of DSFGs. The spectral indices of the Poisson and clustered components are found to be {alpha}-bar{sup P}{sub 150-220}=3.86{+-}0.23 and {alpha} {sup C}{sub 150-220} = 3.8 {+-} 1.3, implying a steep scaling of the dust emissivity index {beta} {approx} 2. The Poisson and clustered power detected in SPT, BLAST (at 600, 860, and 1200 GHz), and Spitzer (1900 GHz) data can be understood in the context of a simple model in which all galaxies have the same graybody spectrum with dust emissivity index of {beta} = 2 and dust temperature T{sub d} = 34 K. In this model, half of the 150 GHz background light comes from redshifts greater than 3.2. We also use the SPT data to place an upper limit on the amplitude of the kinetic Sunyaev-Zel'dovich power spectrum at l = 3000 of 13 {mu}K{sup 2} at 95% confidence.

  7. Constraints on star-forming galaxies at z >= 6.5 from HAWK-I Y-band imaging of GOODS-South

    NASA Astrophysics Data System (ADS)

    Hickey, Samantha; Bunker, Andrew; Jarvis, Matt J.; Chiu, Kuenley; Bonfield, David

    2010-05-01

    We present the results of our search for high-redshift Lyman-break galaxies over the GOODS-South field. We use Hubble Space Telescope (HST)-ACS data in B, V, i' & z', Very Large Telescope (VLT)-ISAAC J and Ks, Spitzer-Infrared Array Camera (IRAC) 3.6, 4.5, 5.8 and 8.0 μm data in conjunction with the new HAWK-I Y-band science verification data to search for dropout galaxies in the redshift range 6 < z < 9. We survey ~119arcmin2 to YAB = 25.7 (5σ), of which 37.5arcmin2 reaches YAB = 25.9. Candidate z' and Y dropouts were selected on the basis of a colour cut of (Y - J)AB > 0.75mag and (z' - Y)AB > 1.0mag, respectively. We find no robust Y-drops (z ~ 9) brighter than JAB < 25.4. In our search for z'-band dropouts (z ~ 6.5- 7.5), we identify four possible candidates, two with z'-drop colours and clear Spitzer-IRAC detections and two less likely candidates. We also identify two previously known Galactic T-dwarf stellar contaminants with these colours, and two likely transient objects seen in the Y-band data. The implications if all or none of our candidates is real on the ultraviolet galaxy luminosity functions at z > 6.5 are explored. We find our number of z'-drop candidates to be insufficient based on the expected number of z' drops in a simple no-evolution scenario from the z = 3 Lyman-break galaxy luminosity function but we are consistent with the observed luminosity function at z ~ 6 (if all our candidates are real). However, if one or both of our best z'-drop candidates are not z > 6.5 galaxies, this would demand evolution of the luminosity function at early epochs, in the sense that the number density of ultraviolet luminous star-forming galaxies at z > 7 is less than at z ~ 6. We show that the future surveys to be conducted with the European Southern Observatory VISTA telescope over the next 5yr will be able to measure the bulk of the luminosity function for both z' and Y dropouts and thus provide the strongest constraints on the level of star-formation within

  8. THE FMOS-COSMOS SURVEY OF STAR-FORMING GALAXIES AT z ∼ 1.6. I. Hα-BASED STAR FORMATION RATES AND DUST EXTINCTION

    SciTech Connect

    Kashino, D.; Sugiyama, N.; Silverman, J. D.; Rodighiero, G.; Renzini, A.; Arimoto, N.; Daddi, E.; Lilly, S. J.; Carollo, C. M.; Sanders, D. B.; Zahid, H. J.; Chu, J.; Hasinger, G.; Kewley, L. J.; Kartaltepe, J.; Nagao, T.; Capak, P.; Ilbert, O.; Kajisawa, M.; Koekemoer, A. M. [HST and JWST Instruments and others

    2013-11-01

    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 for 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.

  9. New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star-forming dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Tang, Jing; Bressan, Alessandro; Rosenfield, Philip; Slemer, Alessandra; Marigo, Paola; Girardi, Léo; Bianchi, Luciana

    2014-12-01

    We extend the PARSEC library of stellar evolutionary tracks by computing new models of massive stars, from 14 to 350 M⊙. The input physics is the same used in the PARSEC V1.1 version, but for the mass-loss rate from considering the most recent updates in the literature. We focus on low metallicity, Z = 0.001 and Z = 0.004, for which the metal-poor dwarf irregular star-forming galaxies, Sextans A, the Wolf-Lundmark-Melotte galaxy and NGC 6822, provide simple but powerful workbenches. The models reproduce fairly well the observed colour-magnitude diagrams (CMDs) but the stellar colour distributions indicate that the predicted blue loop is not hot enough in models with a canonical extent of overshooting. In the framework of a mild extended mixing during central hydrogen burning, the only way to reconcile the discrepancy is to enhance the overshooting at the base of the convective envelope (EO) during the first dredge-up. The mixing scales required to reproduce the observed loops, EO = 2HP or EO = 4HP, are definitely larger than those derived from, e.g. the observed location of the red-giant-branch bump in low mass stars. This effect, if confirmed, would imply a strong dependence of the mixing scale below the formal Schwarzschild border, on the stellar mass or luminosity. Reproducing the features of the observed CMDs with standard values of envelope overshooting would require a metallicity significantly lower than the values measured in these galaxies. Other quantities, such as the star formation rate and the initial mass function, are only slightly sensitive to this effect. Future investigations will consider other metallicities and different mixing schemes.

  10. The Angular Momentum Distribution and Baryon Content of Star-forming Galaxies at z ˜ 1–3

    NASA Astrophysics Data System (ADS)

    Burkert, A.; Förster Schreiber, N. M.; Genzel, R.; Lang, P.; Tacconi, L. J.; Wisnioski, E.; Wuyts, S.; Bandara, K.; Beifiori, A.; Bender, R.; Brammer, G.; Chan, J.; Davies, R.; Dekel, A.; Fabricius, M.; Fossati, M.; Kulkarni, S.; Lutz, D.; Mendel, J. T.; Momcheva, I.; Nelson, E. J.; Naab, T.; Renzini, A.; Saglia, R.; Sharples, R. M.; Sternberg, A.; Wilman, D.; Wuyts, E.

    2016-08-01

    We analyze the angular momenta of massive star-forming galaxies (SFGs) at the peak of the cosmic star formation epoch (z ˜ 0.8–2.6). Our sample of ˜360 log(M */M ⊙) ˜ 9.3–11.8 SFGs is mainly based on the KMOS3D and SINS/zC-SINF surveys of Hα kinematics, and collectively provides a representative subset of the massive star-forming population. The inferred halo scale angular momentum distribution is broadly consistent with that theoretically predicted for their dark matter halos, in terms of mean spin parameter < λ > ˜ 0.037 and its dispersion (σ logλ ˜ 0.2). Spin parameters correlate with the disk radial scale and with their stellar surface density, but do not depend significantly on halo mass, stellar mass, or redshift. Our data thus support the long-standing assumption that on average, even at high redshifts, the specific angular momentum of disk galaxies reflects that of their dark matter halos (j d = j DM). The lack of correlation between λ × (j d /j DM) and the nuclear stellar density Σ*(1 kpc) favors a scenario where disk-internal angular momentum redistribution leads to “compaction” inside massive high-redshift disks. For our sample, the inferred average stellar to dark matter mass ratio is ˜2%, consistent with abundance matching results. Including the molecular gas, the total baryonic disk to dark matter mass ratio is ˜5% for halos near 1012 M ⊙, which corresponds to 31% of the cosmologically available baryons, implying that high-redshift disks are strongly baryon dominated. Based on observations obtained at the Very Large Telescope of the European Southern Observatory, Paranal, Chile (ESO Programme IDs 075.A-0466, 076.A-0527, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 081.B-0568, 081.A-0672, 082.A-0396, 183.A-0781, 087.A-0081, 088.A-0202, 088.A-0209, 091.A-0126, 092.A-0091, 093.A-0079, 094.A-0217, 095.A-0047, 096.A-0025).

  11. Neutral Hydrogen Optical Depth near Star-forming Galaxies at z ≈ 2.4 in the Keck Baryonic Structure Survey

    NASA Astrophysics Data System (ADS)

    Rakic, Olivera; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.

    2012-06-01

    We study the interface between galaxies and the intergalactic medium by measuring the absorption by neutral hydrogen in the vicinity of star-forming galaxies at z ≈ 2.4. Our sample consists of 679 rest-frame UV-selected galaxies with spectroscopic redshifts that have impact parameters <2 (proper) Mpc to the line of sight of one of the 15 bright, background QSOs and that fall within the redshift range of its Lyα forest. We present the first two-dimensional maps of the absorption around galaxies, plotting the median Lyα pixel optical depth as a function of transverse and line-of-sight separation from galaxies. The Lyα optical depths are measured using an automatic algorithm that takes advantage of all available Lyman series lines. The median optical depth, and hence the median density of atomic hydrogen, drops by more than an order of magnitude around 100 kpc, which is similar to the virial radius of the halos thought to host the galaxies. The median remains enhanced, at the >3σ level, out to at least 2.8 Mpc (i.e., >9 comoving Mpc), but the scatter at a given distance is large compared with the median excess optical depth, suggesting that the gas is clumpy. Within 100 (200) kpc, and over ±165 km s-1, the covering fraction of gas with Lyα optical depth greater than unity is 100+0 - 32% (66% ± 16%). Absorbers with τLyα > 0.1 are typically closer to galaxies than random. The mean galaxy overdensity around absorbers increases with the optical depth and also as the length scale over which the galaxy overdensity is evaluated is decreased. Absorbers with τLyα ~ 1 reside in regions where the galaxy number density is close to the cosmic mean on scales >=0.25 Mpc. We clearly detect two types of redshift space anisotropies. On scales <200 km s-1, or <1 Mpc, the absorption is stronger along the line of sight than in the transverse direction. This "finger of God" effect may be due to redshift errors, but is probably dominated by gas motions within or very close to

  12. Mid-J CO Emission from NGC 891: Microturbulent Molecular Shocks in Normal Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Nikola, T.; Stacey, G. J.; Brisbin, D.; Ferkinhoff, C.; Hailey-Dunsheath, S.; Parshley, S.; Tucker, C.

    2011-12-01

    We have detected the CO(6-5), CO(7-6), and [C I] 370 μm lines from the nuclear region of NGC 891 with our submillimeter grating spectrometer ZEUS on the Caltech Submillimeter Observatory. These lines provide constraints on photodissociation region (PDR) and shock models that have been invoked to explain the H2 S(0), S(1), and S(2) lines observed with Spitzer. We analyze our data together with the H2 lines, CO(3-2), and infrared continuum from the literature using a combined PDR/shock model. We find that the mid-J CO originates almost entirely from shock-excited warm molecular gas; contributions from PDRs are negligible. Also, almost all of the H2 S(2) line and half of the S(1) line are predicted to emerge from shocks. Shocks with a pre-shock density of 2 × 104 cm-3 and velocities of 10 km s-1 and 20 km s-1 for C-shocks and J-shocks, respectively, provide the best fit. In contrast, the [C I] line emission arises exclusively from the PDR component, which is best parameterized by a density of 3.2 × 103 cm-3 and a far-ultraviolet field of Go = 100 for both PDR/shock-type combinations. Our mid-J CO observations show that turbulence is a very important heating source in molecular clouds, even in normal quiescent galaxies. The most likely energy sources for the shocks are supernovae or outflows from young stellar objects. The energetics of these shock sources favor C-shock excitation of the lines.

  13. Simultaneously modelling far-infrared dust emission and its relation to CO emission in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Shetty, Rahul; Roman-Duval, Julia; Hony, Sacha; Cormier, Diane; Klessen, Ralf S.; Konstandin, Lukas K.; Loredo, Thomas; Pellegrini, Eric W.; Ruppert, David

    2016-07-01

    We present a method to simultaneously model the dust far-infrared (FIR) spectral energy distribution (SED) and the total infrared - carbon monoxide (CO) integrated intensity (SIR-ICO) relationship. The modelling employs a hierarchical Bayesian (HB) technique to estimate the dust surface density, temperature (Teff), and spectral index at each pixel from the observed FIR maps. Additionally, given the corresponding CO map, the method simultaneously estimates the slope and intercept between the FIR and CO intensities, which are global properties of the observed source. The model accounts for correlated and uncorrelated uncertainties, such as those present in Herschel observations. Using synthetic data sets, we demonstrate the accuracy of the HB method, and contrast the results with common non-hierarchical fitting methods. As an initial application, we model the dust and gas on 100 pc scales in the Magellanic Clouds from Herschel FIR and NANTEN CO observations. The slopes of the logSIR-logICO relationship are similar in both galaxies, falling in the range 1.1-1.7. However, in the Small Magellanic Cloud the intercept is nearly three times higher, which can be explained by its lower metallicity than the Large Magellanic Cloud (LMC), resulting in a larger SIR per unit ICO. The HB modelling evidences an increase in Teff in regions with the highest ICO in the LMC. This may be due to enhanced dust heating in the densest molecular regions from young stars. Such simultaneous dust and gas modelling may reveal variations in the properties of the interstellar medium and its association with other galactic characteristics, such as star formation rates and/or metallicities.

  14. Identification of dusty massive stars in star-forming dwarf irregular galaxies in the Local Group with mid-IR photometry

    NASA Astrophysics Data System (ADS)

    Britavskiy, N. E.; Bonanos, A. Z.; Mehner, A.; Boyer, M. L.; McQuinn, K. B. W.

    2015-12-01

    Context. Increasing the statistics of spectroscopically confirmed evolved massive stars in the Local Group enables the investigation of the mass loss phenomena that occur in these stars in the late stages of their evolution. Aims: We aim to complete the census of luminous mid-IR sources in star-forming dwarf irregular (dIrr) galaxies of the Local Group. To achieve this we employed mid-IR photometric selection criteria to identify evolved massive stars, such as red supergiants (RSGs) and luminous blue variables (LBVs), by using the fact that these types of stars have infrared excess due to dust. Methods: The method is based on 3.6 μm and 4.5 μm photometry from archival Spitzer Space Telescope images of nearby galaxies. We applied our criteria to four dIrr galaxies: Pegasus, Phoenix, Sextans A, and WLM, selecting 79 point sources that we observed with the VLT/FORS2 spectrograph in multi-object spectroscopy mode. Results: We identified 13 RSGs, of which 6 are new discoveries, as well as two new emission line stars, and one candidate yellow supergiant. Among the other observed objects we identified carbon stars, foreground giants, and background objects, such as a quasar and an early-type galaxy that contaminate our survey. We use the results of our spectroscopic survey to revise the mid-IR and optical selection criteria for identifying RSGs from photometric measurements. The optical selection criteria are more efficient in separating extragalactic RSGs from foreground giants than mid-IR selection criteria, but the mid-IR selection criteria are useful for identifying dusty stars in the Local Group. This work serves as a basis for further investigation of the newly discovered dusty massive stars and their host galaxies. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme IDs 090.D-0009 and 091.D-0010.Appendix A is available in electronic form at http://www.aanda.org

  15. New emerging results on molecular gas, stars, and dust at z~2, as revealed by low star formation rate and low stellar mass star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Schaerer, Daniel; Combes, Francoise; Egami, Eiichi; Swinbank, Mark; Richard, Johan; Sklias, Panos; Rawle, Tim D.

    2015-08-01

    The large surveys of main sequence star-forming galaxies (SFGs) at z~2, made at near-IR and mm wavelengths, have revolutionized our picture of galaxies at this critical epoch, where the cosmic star formation rate (SFR) density is at its peak and the stellar mass (Ms) assembly is rapid. They reveal that ~70% of SFGs are young, rotation dominated disk-like systems, yet dynamically hotter and geometrically thicker than local spirals, with larger molecular gas fractions (fgas).It is time to refine this modern picture of z~2 galaxies by extending the current studies toward the more numerous and typical SFGs, characterized by SFR1 from the literature, and allow us to revisit and propose new correlations between IR and CO luminosities, molecular gas, stellar and dust masses, specific SFR, molecular gas depletion timescales (tdepl), fgas, dust-to-gas ratios, and redshift, to be directly compared with galaxy evolution models.We find an increase of tdepl with Ms, as now revealed by low-Ms SFGs at z>1 and also observed at z=0, which contrasts with the acknowledged constant tdepl in "bathtub" models and refutes the linearity of the Kennicutt-Schmidt relation. A steady increase of fgas with redshift is predicted by cosmological models and is observed from z~0 to z~1.5, but is followed by a mild increase toward higher redshifts, which we further confirm with our highest redshift CO measurement in an SFR* galaxy at z=3.6. We provide the first fgas measure in z>1 SFGs at the low-Ms end 109.4

  16. Strong nebular line ratios in the spectra of z ∼ 2-3 star forming galaxies: first results from KBSS-MOSFIRE

    SciTech Connect

    Steidel, Charles C.; Rudie, Gwen C.; Strom, Allison L.; Trainor, Ryan F.; Konidaris, Nicholas P.; Matthews, Keith; Pettini, Max; Reddy, Naveen A.; Shapley, Alice E.; Kulas, Kristin R.; Mace, Gregory; McLean, Ian S.; Erb, Dawn K.; Turner, Monica L.

    2014-11-10

    We present initial results of a deep near-IR spectroscopic survey covering the 15 fields of the Keck Baryonic Structure Survey using the recently commissioned MOSFIRE spectrometer on the Keck 1 telescope. We focus on a sample of 251 galaxies with redshifts 2.0 < z < 2.6, star formation rates (SFRs) 2 ≲ SFR ≲ 200 M {sub ☉} yr{sup –1}, and stellar masses 8.6 < log (M {sub *}/M {sub ☉}) < 11.4, with high-quality spectra in both H- and K-band atmospheric windows. We show unambiguously that the locus of z ∼ 2.3 galaxies in the 'BPT' nebular diagnostic diagram exhibits an almost entirely disjointed, yet similarly tight, relationship between the line ratios [N II] λ6585/Hα and [O III]/Hβ as compared to local galaxies. Using photoionization models, we argue that the offset of the z ∼ 2.3 BPT locus relative to that at z ∼ 0 is caused by a combination of harder stellar ionizing radiation field, higher ionization parameter, and higher N/O at a given O/H compared to most local galaxies, and that the position of a galaxy along the z ∼ 2.3 star-forming BPT locus is surprisingly insensitive to gas-phase oxygen abundance. The observed nebular emission line ratios are most easily reproduced by models in which the net stellar ionizing radiation field resembles a blackbody with effective temperature T {sub eff} = 50, 000-60, 000 K, the gas-phase oxygen abundances lie in the range 0.2 < Z/Z {sub ☉} < 1.0, and the ratio of gas-phase N/O is close to the solar value. We critically assess the applicability at high redshift of commonly used strong line indices for estimating gas-phase metallicity, and consider the implications of the small intrinsic scatter of the empirical relationship between excitation-sensitive line indices and M {sub *} (i.e., the 'mass-metallicity' relation) at z ≅ 2.3.

  17. High-velocity blueshifted Fe II absorption in the dwarf star-forming galaxy PHL 293B: evidence for a wind driven supershell?

    NASA Astrophysics Data System (ADS)

    Terlevich, Roberto; Terlevich, Elena; Bosch, Guillermo; Díaz, Ángeles; Hägele, Guillermo; Cardaci, Mónica; Firpo, Verónica

    2014-12-01

    X-shooter and WHT-ISIS spectra of the star-forming galaxy PHL 293B also known as A2228-00 and SDSS J223036.79-000636.9 are presented in this paper. We find broad (FWHM = 1000 km s-1) and very broad (FWZI = 4000 km s-1) components in the Balmer lines, narrow absorption components in the Balmer series blueshifted by 800 km s-1, previously undetected Fe II multiplet (42) absorptions also blueshifted by 800 km s-1, IR Ca II triplet stellar absorptions consistent with [Fe/H] < -2.0 and no broad components or blueshifted absorptions in the He I lines. Based on historical records, we found no optical variability at the 5σ level of 0.02 mag between 2005 and 2013 and no optical variability at the level of 0.1 mag for the past 24 yr. The lack of variability rules out transient phenomena like luminous blue variables or Type IIn supernovae as the origin of the blueshifted absorptions of H I and Fe II. The evidence points to either a young and dense expanding supershell or a stationary cooling wind, in both cases driven by the young cluster wind.

  18. THE UV LUMINOSITY FUNCTION OF STAR-FORMING GALAXIES VIA DROPOUT SELECTION AT REDSHIFTS z {approx} 7 AND 8 FROM THE 2012 ULTRA DEEP FIELD CAMPAIGN

    SciTech Connect

    Schenker, Matthew A.; Ellis, Richard S.; Robertson, Brant E.; Schneider, Evan; Ono, Yoshiaki; Ouchi, Masami; Stark, Daniel P.; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Curtis-Lake, Emma; Rogers, Alexander B.; Cirasuolo, Michele; Koekemoer, Anton; Charlot, Stephane; Furlanetto, Steven R.

    2013-05-10

    We present a catalog of high-redshift star-forming galaxies selected to lie within the redshift range z {approx_equal} 7-8 using the Ultra Deep Field 2012 (UDF12), the deepest near-infrared (near-IR) exposures yet taken with the Hubble Space Telescope (HST). As a result of the increased near-IR exposure time compared to previous HST imaging in this field, we probe {approx}0.65 (0.25) mag fainter in absolute UV magnitude, at z {approx} 7 (8), which increases confidence in a measurement of the faint end slope of the galaxy luminosity function. Through a 0.7 mag deeper limit in the key F105W filter that encompasses or lies just longward of the Lyman break, we also achieve a much-refined color-color selection that balances high redshift completeness and a low expected contamination fraction. We improve the number of dropout-selected UDF sources to 47 at z {approx} 7 and 27 at z {approx} 8. Incorporating brighter archival and ground-based samples, we measure the z {approx_equal} 7 UV luminosity function to an absolute magnitude limit of M{sub UV} = -17 and find a faint end Schechter slope of {alpha}=-1.87{sup +0.18}{sub -0.17}. Using a similar color-color selection at z {approx_equal} 8 that takes our newly added imaging in the F140W filter into account, and incorporating archival data from the HIPPIES and BoRG campaigns, we provide a robust estimate of the faint end slope at z {approx_equal} 8, {alpha}=-1.94{sup +0.21}{sub -0.24}. We briefly discuss our results in the context of earlier work and that derived using the same UDF12 data but with an independent photometric redshift technique.

  19. Molecular gas, stars, and dust in sub-L* star-forming galaxies at z~2: evidence for universal star formation and nonuniversal dust-to-gas ratio

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Schaerer, Daniel; Combes, Francoise; Egami, Eiichi; Swinbank, A. Mark; Richard, Johan; Sklias, Panos; Rawle, Tim D.

    2015-08-01

    Only recently have CO measurements become possible in main sequence star-forming galaxies (SFGs) at z=1-3, but are still biased toward high star formation rates (SFR) and stellar masses (Ms), because of instrumental sensitivity limitations. It is essential to extend these studies toward the more numerous and typical SFGs, characterized by IR luminosities LIRgalaxies from the literature, we revisit and propose new correlations between IR and CO luminosities, molecular gas, stellar and dust masses, specific SFR, molecular gas depletion timescales (tdepl), molecular gas fractions (fgas), dust-to-gas ratios, and redshift. These correlations betray the interplay between gas, dust, and star formation in galaxies.All the LIR, L'CO(1-0) data are best-fitted with a single relation, which spans 5 orders of magnitude in LIR, covers redshifts from z=0 to z=5.3, and samples spirals, main sequence SFGs, and starbursts. This favors a universal star formation. We find an increase of tdepl with Ms, as now revealed by low-Ms SFGs at z>1 and also observed at z=0, which contrasts with the acknowledged constant tdepl and refutes the linearity of the Kennicutt-Schmidt relation between molecular gas and SFR at galactic scales. A steady increase of fgas with redshift is predicted and is observed from z~0 to z~1.5, but is followed by a mild increase toward higher redshifts, which we further confirm with our highest redshift CO measurement in an L* galaxy at z=3.6. We provide the first fgas measure in z>1 SFGs at the low-Ms end 109.4

  20. The VIMOS Ultra Deep Survey: Lyα emission and stellar populations of star-forming galaxies at 2 < z < 2.5

    NASA Astrophysics Data System (ADS)

    Hathi, N. P.; Le Fèvre, O.; Ilbert, O.; Cassata, P.; Tasca, L. A. M.; Lemaux, B. C.; Garilli, B.; Le Brun, V.; Maccagni, D.; Pentericci, L.; Thomas, R.; Vanzella, E.; Zamorani, G.; Zucca, E.; Amorín, R.; Bardelli, S.; Cassarà, L. P.; Castellano, M.; Cimatti, A.; Cucciati, O.; Durkalec, A.; Fontana, A.; Giavalisco, M.; Grazian, A.; Guaita, L.; Koekemoer, A.; Paltani, S.; Pforr, J.; Ribeiro, B.; Schaerer, D.; Scodeggio, M.; Sommariva, V.; Talia, M.; Tresse, L.; Vergani, D.; Capak, P.; Charlot, S.; Contini, T.; Cuby, J. G.; de la Torre, S.; Dunlop, J.; Fotopoulou, S.; López-Sanjuan, C.; Mellier, Y.; Salvato, M.; Scoville, N.; Taniguchi, Y.; Wang, P. W.

    2016-04-01

    The aim of this paper is to investigate spectral and photometric properties of 854 faint (iAB ≲ 25 mag) star-forming galaxies (SFGs) at 2 < z < 2.5 using the VIMOS Ultra-Deep Survey (VUDS) spectroscopic data and deep multi-wavelength photometric data in three extensively studied extragalactic fields (ECDFS, VVDS, COSMOS). These SFGs were targeted for spectroscopy as a result of their photometric redshifts. The VUDS spectra are used to measure the UV spectral slopes (β) as well as Lyα equivalent widths (EW). On average, the spectroscopically measured β (-1.36 ± 0.02), is comparable to the photometrically measured β (-1.32 ± 0.02), and has smaller measurement uncertainties. The positive correlation of β with the spectral energy distribution (SED)-based measurement of dust extinction Es(B-V) emphasizes the importance of β as an alternative dust indicator at high redshifts. To make a proper comparison, we divide these SFGs into three subgroups based on their rest-frame Lyα EW: SFGs with no Lyα emission (SFGN; EW ≤ 0 Å), SFGs with Lyα emission (SFGL; EW > 0 Å), and Lyα emitters (LAEs; EW ≥ 20 Å). The fraction of LAEs at these redshifts is ~10%, which is consistent with previous observations. We compared best-fitSED-estimated stellar parameters of the SFGN, SFGL and LAE samples. For the luminosities probed here (~ L∗), we find that galaxies with and without Lyα in emission have small but significant differences in their SED-based properties. We find that LAEs have less dust, and lower star-formation rates (SFR) compared to non-LAEs. We also find that LAEs are less massive compared to non-LAEs, though the difference is smaller and less significant compared to the SFR and Es(B-V). When we divide the LAEs according to their Spitzer/IRAC 3.6 μm fluxes, we find that the fraction of IRAC-detected (m3.6 ≲ 25 mag) LAEs is much higher than the fraction of IRAC-detected narrow band (NB)-selected LAEs at z ≃ 2-3. This could imply that UV-selected LAEs

  1. PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS IN z {approx} 1-3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES

    SciTech Connect

    Tacconi, L. J.; Genzel, R.; Wuyts, S.; Foerster Schreiber, N. M.; Gracia-Carpio, J.; Lutz, D.; Saintonge, A.; Neri, R.; Cox, P.; Combes, F.; Bolatto, A.; Cooper, M. C.; Bournaud, F.; Comerford, J.; Davis, M.; Newman, S.; Garcia-Burillo, S.; Naab, T.; Omont, A. E-mail: genzel@mpe.mpg.de; and others

    2013-05-01

    We present PHIBSS, the IRAM Plateau de Bure high-z blue sequence CO 3-2 survey of the molecular gas properties in massive, main-sequence star-forming galaxies (SFGs) near the cosmic star formation peak. PHIBSS provides 52 CO detections in two redshift slices at z {approx} 1.2 and 2.2, with log(M{sub *}(M{sub Sun })) {>=} 10.4 and log(SFR(M{sub Sun }/yr)) {>=} 1.5. Including a correction for the incomplete coverage of the M{sub *} -SFR plane, and adopting a ''Galactic'' value for the CO-H{sub 2} conversion factor, we infer average gas fractions of {approx}0.33 at z {approx} 1.2 and {approx}0.47 at z {approx} 2.2. Gas fractions drop with stellar mass, in agreement with cosmological simulations including strong star formation feedback. Most of the z {approx} 1-3 SFGs are rotationally supported turbulent disks. The sizes of CO and UV/optical emission are comparable. The molecular-gas-star-formation relation for the z = 1-3 SFGs is near-linear, with a {approx}0.7 Gyr gas depletion timescale; changes in depletion time are only a secondary effect. Since this timescale is much less than the Hubble time in all SFGs between z {approx} 0 and 2, fresh gas must be supplied with a fairly high duty cycle over several billion years. At given z and M{sub *}, gas fractions correlate strongly with the specific star formation rate (sSFR). The variation of sSFR between z {approx} 0 and 3 is mainly controlled by the fraction of baryonic mass that resides in cold gas.

  2. A Total Molecular Gas Mass Census in Z ˜ 2-3 Star-forming Galaxies: Low-J CO Excitation Probes of Galaxies’ Evolutionary States

    NASA Astrophysics Data System (ADS)

    Sharon, Chelsea E.; Riechers, Dominik A.; Hodge, Jacqueline; Carilli, Chris L.; Walter, Fabian; Weiß, Axel; Knudsen, Kirsten K.; Wagg, Jeff

    2016-08-01

    We present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array for 14 z˜ 2 galaxies with existing CO(3-2) measurements, including 11 galaxies that contain active galactic nuclei (AGNs) and three submillimeter galaxies (SMGs). We combine this sample with an additional 15 z˜ 2 galaxies from the literature that have both CO(1-0) and CO(3-2) measurements in order to evaluate differences in CO excitation between SMGs and AGN host galaxies, to measure the effects of CO excitation on the derived molecular gas properties of these populations, and to look for correlations between the molecular gas excitation and other physical parameters. With our expanded sample of CO(3-2)/CO(1-0) line ratio measurements, we do not find a statistically significant difference in the mean line ratio between SMGs and AGN host galaxies as can be found in the literature; we instead find {r}{3,1}=1.03+/- 0.50 for AGN host galaxies and {r}{3,1}=0.78+/- 0.27 for SMGs (or {r}{3,1}=0.90+/- 0.40 for both populations combined). We also do not measure a statistically significant difference between the distributions of the line ratios for these populations at the p = 0.05 level, although this result is less robust. We find no excitation dependence on the index or offset of the integrated Schmidt-Kennicutt relation for the two CO lines, and we obtain indices consistent with N = 1 for the various subpopulations. However, including low-z “normal” galaxies increases our best-fit Schmidt-Kennicutt index to N˜ 1.2. While we do not reproduce correlations between the CO line width and luminosity, we do reproduce correlations between CO excitation and star-formation efficiency.

  3. Surface brightness and color distributions in blue compact dwarf galaxies. I - Haro 2, an extreme example of a star-forming young elliptical galaxy

    NASA Technical Reports Server (NTRS)

    Loose, Hans-Hermann; Thuan, Trinh X.

    1986-01-01

    The first results of a large-scale program to study the morphology and structure of blue compact dwarf galaxies from CCD observations are presented. The observations and reduction procedures are described, and surface brightness and color profiles are shown. The results are used to discuss the morphological type of Haro 2 and its stellar populations. It is found that Haro 2 appears to be an extreme example of an elliptical galaxy undergoing intense star formation in its central regions, and that the oldest stars it contains were made only about four million yr ago. The 'missing' mass problem of Haro 2 is also discussed.

  4. The Nuclear Activities of Nearby S0 Galaxies

    NASA Astrophysics Data System (ADS)

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

    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 nuclear 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.

  5. Star-forming Activity in the H II Regions Associated with the IRAS 17160–3707 Complex

    NASA Astrophysics Data System (ADS)

    Nandakumar, G.; Veena, V. S.; Vig, S.; Tej, A.; Ghosh, S. K.; Ojha, D. K.

    2016-11-01

    We present a multiwavelength investigation of star formation activity toward the southern H ii regions associated with IRAS 17160–3707, located at a distance of 6.2 kpc with a bolometric luminosity of 8.3 × 105 L ⊙. The ionized gas distribution and dust clumps in the parental molecular cloud are examined in detail using measurements at infrared, submillimeter and radio wavelengths. The radio continuum images at 1280 and 610 MHz obtained using the Giant Metrewave Radio Telescope reveal the presence of multiple compact sources as well as nebulous emission. At submillimeter wavelengths, we identify seven dust clumps and estimate their physical properties such as temperature: 24–30 K, mass: 300–4800 M ⊙ and luminosity: 9–317 × 102 L ⊙ using modified blackbody fits to the spectral energy distributions (SEDs) between 70 and 870 μm. We find 24 young stellar objects (YSOs) in the mid-infrared, with a few of them coincident with the compact radio sources. The SEDs of the YSOs have been fitted by the Robitaille models and the results indicate that those having radio compact sources as counterparts host massive objects in early evolutionary stages with best fit age ≤0.2 Myr. We compare the relative evolutionary stages of clumps using various signposts such as masers, ionized gas, presence of YSOs and infrared nebulosity, and find six massive star-forming clumps and one quiescent clump. Of the former, five are in a relatively advanced stage and one in an earlier stage.

  6. A KINEMATIC APPROACH TO ASSESSING ENVIRONMENTAL EFFECTS: STAR-FORMING GALAXIES IN A z {approx} 0.9 SpARCS CLUSTER USING SPITZER 24 {mu}m OBSERVATIONS

    SciTech Connect

    Noble, A. G.; Webb, T. M. A.; Muzzin, A.; Van der Burg, R. F. J.; Wilson, G.; Yee, H. K. C.

    2013-05-10

    We present an infrared study of a z = 0.872 cluster, SpARCS J161314+564930, with the primary aim of distinguishing the dynamical histories of spectroscopically confirmed star-forming members to assess the role of cluster environment. We utilize deep MIPS imaging and a mass-limited sample of 85 spectroscopic members to identify 16 24 {mu}m bright sources within the cluster, and measure their 24 {mu}m star formation rates (SFRs) down to {approx}6 M{sub Sun} yr{sup -1}. Based on their line-of-sight velocities and stellar ages, MIPS cluster members appear to be an infalling population that was recently accreted from the field with minimal environmental dependency on their star formation. However, we identify a double-sequenced distribution of star-forming galaxies among the members, with one branch exhibiting declining specific SFRs with mass. The members along this sub-main sequence contain spectral features suggestive of passive galaxies. Using caustic diagrams, we kinematically identify these galaxies as a virialized and/or backsplash population. Moreover, we find a mix of dynamical histories at all projected radii, indicating that standard definitions of environment (i.e., radius and density) are contaminated with recently accreted interlopers, which could contribute to a lack of environmental trends for star-forming galaxies. A cleaner narrative of their dynamical past begins to unfold when using a proxy for accretion histories through profiles of constant (r/r{sub 200}) Multiplication-Sign ({Delta}v/{sigma}{sub v}); galaxies accreted at earlier times possess lower values of (r/r{sub 200}) Multiplication-Sign ({Delta}v/{sigma}{sub v}) with minimal contamination from the distinct infalling population. Therefore, adopting a time-averaged definition for density (as traced by accretion histories) rather than an instantaneous density yields a depressed specific SFR within the dynamical cluster core.

  7. SPATIALLY RESOLVED H{alpha} MAPS AND SIZES OF 57 STRONGLY STAR-FORMING GALAXIES AT z {approx} 1 FROM 3D-HST: EVIDENCE FOR RAPID INSIDE-OUT ASSEMBLY OF DISK GALAXIES

    SciTech Connect

    Nelson, Erica June; Van Dokkum, Pieter G.; Skelton, Rosalind E.; Bezanson, Rachel; Lundgren, Britt; Brammer, Gabriel; Foerster Schreiber, Natascha; Franx, Marijn; Fumagalli, Mattia; Patel, Shannon; Labbe, Ivo; Rix, Hans-Walter; Da Cunha, Elisabete; Schmidt, Kasper B.; Kriek, Mariska; Quadri, Ryan

    2012-03-10

    We investigate the buildup of galaxies at z {approx} 1 using maps of H{alpha} and stellar continuum emission for a sample of 57 galaxies with rest-frame H{alpha} equivalent widths >100 A in the 3D-HST grism survey. We find that the H{alpha} emission broadly follows the rest-frame R-band light but that it is typically somewhat more extended and clumpy. We quantify the spatial distribution with the half-light radius. The median H{alpha} effective radius r{sub e} (H{alpha}) is 4.2 {+-} 0.1 kpc but the sizes span a large range, from compact objects with r{sub e} (H{alpha}) {approx} 1.0 kpc to extended disks with r{sub e} (H{alpha}) {approx} 15 kpc. Comparing H{alpha} sizes to continuum sizes, we find =1.3 {+-} 0.1 for the full sample. That is, star formation, as traced by H{alpha}, typically occurs out to larger radii than the rest-frame R-band stellar continuum; galaxies are growing their radii and building up from the inside out. This effect appears to be somewhat more pronounced for the largest galaxies. Using the measured H{alpha} sizes, we derive star formation rate surface densities, {Sigma}{sub SFR}. We find that {Sigma}{sub SFR} ranges from {approx}0.05 M{sub Sun} yr{sup -1} kpc{sup -2} for the largest galaxies to {approx}5 M{sub Sun} yr{sup -1} kpc{sup -2} for the smallest galaxies, implying a large range in physical conditions in rapidly star-forming z {approx} 1 galaxies. Finally, we infer that all galaxies in the sample have very high gas mass fractions and stellar mass doubling times <500 Myr. Although other explanations are also possible, a straightforward interpretation is that we are simultaneously witnessing the rapid formation of compact bulges and large disks at z {approx} 1.

  8. The NGP +30° Zone Galaxies. I. Comparative Study of the Galaxies with Different Nuclear Activity

    NASA Astrophysics Data System (ADS)

    Petrosian, Artashes R.; McLean, B.; Allen, R.; Leitherer, C.; Kunth, Daniel

    2007-08-01

    A database for 618 active and star forming (A/SF) and 564 normal (N) galaxies in the NGP with large number of parameters is presented. These parameters of A/SF and N galaxies are compared using MFA. Main results are following: A/SF galaxies are objects with later morphologies, more inclined and with bluer colors than N galaxies. All sample peculiar galaxies are A/SF objects. SF galaxies are objects with relatively late morphological types, lower absolute luminosities and linear sizes, bluer colors and more inclined than sample X-Ray or radio sources as well as Seyferts. NIR colors of the galaxies are independent parameters and do not correlate with any other parameters of the galaxies.

  9. An intensely star-forming galaxy at z ∼ 7 with low dust and metal content revealed by deep ALMA and HST observations

    SciTech Connect

    Ouchi, Masami; Ono, Yoshiaki; Momose, Rieko; Ellis, Richard; Nakanishi, Kouichiro; Kohno, Kotaro; Tamura, Yoichi; Kurono, Yasutaka; Ashby, M. L. N.; Willner, S. P.; Fazio, G. G.; Shimasaku, Kazuhiro; Iono, Daisuke

    2013-12-01

    We report deep ALMA observations complemented by associated Hubble Space Telescope (HST) imaging for a luminous (m {sub UV} = 25) galaxy, 'Himiko', at a redshift of z = 6.595. The galaxy is remarkable for its high star formation rate, 100 M {sub ☉} yr{sup –1}, which has been securely estimated from our deep HST and Spitzer photometry, and the absence of any evidence for strong active galactic nucleus activity or gravitational lensing magnification. Our ALMA observations probe an order of magnitude deeper than previous IRAM observations, yet fail to detect a 1.2 mm dust continuum, indicating a flux of <52 μJy, which is comparable to or weaker than that of local dwarf irregulars with much lower star formation rates. We likewise provide a strong upper limit for the flux of [C II] 158 μm, L{sub [C} {sub II]}<5.4×10{sup 7} L{sub ⊙}, which is a diagnostic of the hot interstellar gas that is often described as a valuable probe for early galaxies. In fact, our observations indicate that Himiko lies off the local L{sub [C} {sub II]}-star formation rate scaling relation by a factor of more than 30. Both aspects of our ALMA observations suggest that Himiko is a unique object with a very low dust content and perhaps nearly primordial interstellar gas. Our HST images provide unique insight into the morphology of this remarkable source, highlighting an extremely blue core of activity and two less extreme associated clumps. Himiko is undergoing a triple major merger event whose extensive ionized nebula of Lyα emitting gas, discovered in our earlier work with Subaru, is powered by star formation and the dense circumgalactic gas. We are likely witnessing an early massive galaxy during a key period of its mass assembly close to the end of the reionization era.

  10. PROBING THE BALANCE OF AGN AND STAR-FORMING ACTIVITY IN THE LOCAL UNIVERSE WITH ChaMP

    SciTech Connect

    Constantin, Anca; Green, Paul; Aldcroft, Tom; Kim, Dong-Woo; Haggard, Daryl; Anderson, Scott F.; Barkhouse, Wayne

    2009-11-10

    The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra Multiwavelength Project (ChaMP) currently offers the largest and most homogeneously selected sample of nearby galaxies for investigating the relation between X-ray nuclear emission, nebular line emission, black hole masses, and properties of the associated stellar populations. We provide X-ray spectral fits and valid uncertainties for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19). We present here novel constraints that both X-ray luminosity L{sub X} and X-ray spectral energy distribution bring to the galaxy evolutionary sequence H II -> Seyfert/Transition Object -> LINER -> Passive suggested by optical data. In particular, we show that both L{sub X} and GAMMA, the slope of the power law that best fits the 0.5-8 keV spectra, are consistent with a clear decline in the accretion power along the sequence, corresponding to a softening of their spectra. This implies that, at z approx 0, or at low-luminosity active galactic nucleus (AGN) levels, there is an anticorrelation between GAMMA and L/L {sub edd}, opposite to the trend exhibited by high z AGN (quasars). The turning point in the GAMMA-L/L{sub edd} LLAGN + quasars relation occurs near GAMMA approx 1.5 and L/L{sub edd} approx 0.01. Interestingly, this is identical to what stellar mass X-ray binaries exhibit, indicating that we have probably found the first empirical evidence for an intrinsic switch in the accretion mode, from advection-dominated flows to standard (disk/corona) accretion modes in supermassive black hole accretors, similar to what has been seen and proposed to happen in stellar mass black hole systems. The anticorrelation we find between GAMMA and L/L{sub edd} may instead indicate that stronger accretion correlates with greater absorption. Therefore, the trend for softer spectra toward more luminous, high redshift, and strongly accreting (L/L{sub edd} approx> 0.01) AGNs/quasars could simply be the result

  11. HST/WFC3 CONFIRMATION OF THE INSIDE-OUT GROWTH OF MASSIVE GALAXIES AT 0 < z < 2 AND IDENTIFICATION OF THEIR STAR-FORMING PROGENITORS AT z {approx} 3

    SciTech Connect

    Patel, Shannon G.; Franx, Marijn; Muzzin, Adam; Van Dokkum, Pieter G.; Quadri, Ryan F.; Williams, Rik J.; Marchesini, Danilo; Holden, Bradford P.

    2013-03-20

    We study the structural evolution of massive galaxies by linking progenitors and descendants at a constant cumulative number density of n{sub c} = 1.4 Multiplication-Sign 10{sup -4} Mpc{sup -3} to z {approx} 3. Structural parameters were measured by fitting Sersic profiles to high-resolution CANDELS HST WFC3 J{sub 125} and H{sub 160} imaging in the UKIDSS-UDS at 1 < z < 3 and ACS I{sub 814} imaging in COSMOS at 0.25 < z < 1. At a given redshift, we selected the HST band that most closely samples a common rest-frame wavelength so as to minimize systematics from color gradients in galaxies. At fixed n{sub c}, galaxies grow in stellar mass by a factor of {approx}3 from z {approx} 3 to z {approx} 0. The size evolution is complex: galaxies appear roughly constant in size from z {approx} 3 to z {approx} 2 and then grow rapidly to lower redshifts. The evolution in the surface mass density profiles indicates that most of the mass at r < 2 kpc was in place by z {approx} 2, and that most of the new mass growth occurred at larger radii. This inside-out mass growth is therefore responsible for the larger sizes and higher Sersic indices of the descendants toward low redshift. At z < 2, the effective radius evolves with the stellar mass as r{sub e} {proportional_to}M {sup 2.0}, consistent with scenarios that find dissipationless minor mergers to be a key driver of size evolution. The progenitors at z {approx} 3 were likely star-forming disks with r{sub e} {approx} 2 kpc, based on their low Sersic index of n {approx} 1, low median axis ratio of b/a {approx} 0.52, and typical location in the star-forming region of the U - V versus V - J diagram. By z {approx} 1.5, many of these star-forming disks disappeared, giving rise to compact quiescent galaxies. Toward lower redshifts, these galaxies continued to assemble mass at larger radii and became the local ellipticals that dominate the high-mass end of the mass function at the present epoch.

  12. Merger Signatures in the Dynamics of Star-forming Gas

    NASA Astrophysics Data System (ADS)

    Hung, Chao-Ling; Hayward, Christopher C.; Smith, Howard A.; Ashby, Matthew L. N.; Lanz, Lauranne; Martínez-Galarza, Juan R.; Sanders, D. B.; Zezas, Andreas

    2016-01-01

    The recent advent of integral field spectrographs and millimeter interferometers has revealed the internal dynamics of many hundreds of star-forming galaxies. Spatially resolved kinematics have been used to determine the dynamical status of star-forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-forming gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-forming gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, gas fractions, and mass ratios, we find that the merger signatures are visible for ˜0.2-0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive gas-rich disk galaxies designed to be analogs of z ˜ 2-3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20%-60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-forming gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-forming galaxies, and including them in samples of star-forming disks may bias the measurements of disk properties such

  13. DUST EXTINCTION FROM BALMER DECREMENTS OF STAR-FORMING GALAXIES AT 0.75 {<=} z {<=} 1.5 WITH HUBBLE SPACE TELESCOPE/WIDE-FIELD-CAMERA 3 SPECTROSCOPY FROM THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY

    SciTech Connect

    Dominguez, A.; Siana, B.; Masters, D.; Henry, A. L.; Martin, C. L.; Scarlata, C.; Bedregal, A. G.; Malkan, M.; Ross, N. R.; Atek, H.; Colbert, J. W.; Teplitz, H. I.; Rafelski, M.; McCarthy, P.; Hathi, N. P.; Dressler, A.; Bunker, A.

    2013-02-15

    Spectroscopic observations of H{alpha} and H{beta} emission lines of 128 star-forming galaxies in the redshift range 0.75 {<=} z {<=} 1.5 are presented. These data were taken with slitless spectroscopy using the G102 and G141 grisms of the Wide-Field-Camera 3 (WFC3) on board the Hubble Space Telescope as part of the WFC3 Infrared Spectroscopic Parallel survey. Interstellar dust extinction is measured from stacked spectra that cover the Balmer decrement (H{alpha}/H{beta}). We present dust extinction as a function of H{alpha} luminosity (down to 3 Multiplication-Sign 10{sup 41} erg s{sup -1}), galaxy stellar mass (reaching 4 Multiplication-Sign 10{sup 8} M {sub Sun }), and rest-frame H{alpha} equivalent width. The faintest galaxies are two times fainter in H{alpha} luminosity than galaxies previously studied at z {approx} 1.5. An evolution is observed where galaxies of the same H{alpha} luminosity have lower extinction at higher redshifts, whereas no evolution is found within our error bars with stellar mass. The lower H{alpha} luminosity galaxies in our sample are found to be consistent with no dust extinction. We find an anti-correlation of the [O III] {lambda}5007/H{alpha} flux ratio as a function of luminosity where galaxies with L {sub H{alpha}} < 5 Multiplication-Sign 10{sup 41} erg s{sup -1} are brighter in [O III] {lambda}5007 than H{alpha}. This trend is evident even after extinction correction, suggesting that the increased [O III] {lambda}5007/H{alpha} ratio in low-luminosity galaxies is likely due to lower metallicity and/or higher ionization parameters.

  14. HST/WFC3 Near-Infrared Spectroscopy of Quenched and Mildly Star Forming Galaxies at 1.4 from WISPs: Stellar Population Properties

    NASA Astrophysics Data System (ADS)

    Bedregal, Alejandro; Scarlata, C.; WISP Survey Team

    2013-01-01

    We combine HST G102 and G141 near-IR grism spectroscopy with HST/UVIS, HST/WFC3 and Spitzer/IRAC[3.6 micron] photometry to assemble a sample of massive (M_star/M_sun = 11.0 dex) and rather passive galaxies at 1.4. After restricting to masses above 10.65 dex, this sample of 80 sources is the largest with homogeneous near-IR spectroscopy for this kind of galaxies at these redshifts. In contrast to the local Universe, we find the mass range above 10.65 dex is populated by galaxies with a wide range of properties. Although our color selection excludes from the sample typical SF massive galaxies, we still find two populations characterized by distinctive average luminosity-weighted ages and star-formation time-scales, but having similar mass and redshift distributions. The spectral energy distributions of Quenched galaxies (SSFR=<10^-2Gyr^-1) are well fitted with exponentially decreasing SFHs, and short star-formation timescales (tau=10-100Myr). They also show a wide distribution in ages, between 1 and 3 Gyrs. On the other hand, we also find a population of low SSFR galaxies (SSFR >10^-2Gyr.^-1) which show more extended SFHs (tau=0.1-1Gyr), being mostly old 3Gyr), and with higher A_V extinctions than the quenched galaxies. Given the stellar mass range covered by our SF galaxies, we find that their SFRs are low compared to normal SF galaxies at these redshifts (median SF 7M_sun yr^-1). We find that the old and massive population of mild-SF galaxies has properties inconsistent with them being a rejuvenated version of the quenched population at the same redshift. This possibly implies that the two samples originate from different mechanisms. In particular, the stellar-population properties of the quenched galaxies are consistent with being the result of gas-rich major mergers, well before the epoch of observation, and with a quick truncation of the SF after the merger. Instead, the properties of the old and mild-SF galaxies are in better agreement with a more extended

  15. Dust Obscuration and Metallicity at High Redshift: New Inferences from UV, Hα, and 8 μm Observations of z ~ 2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Reddy, Naveen A.; Erb, Dawn K.; Pettini, Max; Steidel, Charles C.; Shapley, Alice E.

    2010-04-01

    We use a sample of 90 spectroscopically confirmed Lyman break galaxies with Hα measurements and Spitzer MIPS 24 μm observations to constrain the relationship between rest-frame 8 μm luminosity (L 8) and star formation rate (SFR) for L* galaxies at z ~ 2. We find a tight correlation with 0.24 dex scatter between L 8 and Hα luminosity/SFR for z ~ 2 galaxies with 1010 L sun <~ L IR <~ 1012 L sun. Employing this relationship with a larger sample of 392 galaxies with spectroscopic redshifts, we find that the UV slope β can be used to recover the dust attenuation of the vast majority of moderately luminous L* galaxies at z ~ 2 to within a 0.4 dex scatter using the local correlation. Separately, young galaxies with ages lsim100 Myr appear to be less dusty than their UV slopes would imply based on the local trend and may follow an extinction curve that is steeper than what is typically assumed. Consequently, very young galaxies at high redshift may be significantly less dusty than inferred previously. Our results provide the first direct evidence, independent of the UV slope, for a correlation between UV and bolometric luminosity (L bol) at high redshift, in the sense that UV-faint galaxies are on average less infrared and less bolometrically luminous than their UV-bright counterparts. The L bol-L UV relation indicates that as the SFR increases, L UV turns over (or "saturates") around the value of L* at z ~ 2, implying that dust obscuration may be largely responsible for modulating the bright end of the UV luminosity function. Finally, dust attenuation is found to correlate with oxygen abundance at z ~ 2. Accounting for systematic differences in local and high-redshift metallicity calibrations, we find that L* galaxies at z ~ 2, while at least an order of magnitude more bolometrically luminous, exhibit ratios of metals to dust that are similar to those of local starbursts. This result is expected if high-redshift galaxies are forming their stars in a less metal

  16. Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation Rate

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Rigby, Jane R.; Cooper, Michael; Yan, Renbin

    2015-01-01

    We report on the discovery of 28 redshift (z) approximately equal to 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFR with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 dex above the redshift (z) approximately 1 stellar mass-SFR relation and 0.23 plus or minus 0.23 dex below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 dex, but significant dispersion remains dex with 0.16 dex due to measurement uncertainties). This dispersion suggests that gas accretion, star formation, and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately equal to 100 (sup plus 310) (sub minus 75) million years which suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 94.4 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas but has not had time to drive the metal-enriched gas out with feedback mechanisms.

  17. Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation Rate

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Rigby, Jane R.; Cooper, Michael; Yan, Renbin

    2015-01-01

    We report on the discovery of 28 redshift (z) approximately 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) extends to low stellar mass and high SFR. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFRs, with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 decimal exponent (dex) above the redshift (z) approximately equal to 1 stellar mass-SFR relation, and 0.23 plus or minus 0.23 decimal exponent (dex) below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 decimal exponent (dex), but significant dispersion remains (0.29 decimal exponent (dex) with 0.16 decimal exponent (dex) due to measurement uncertainties). This dispersion suggests that gas accretion, star formation and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately 100 (sup plus 310) (sub minus 75) million years that suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 97.3 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas, but has not had time to drive the metal-enriched gas out with feedback mechanisms.

  18. Young, Star-forming Galaxies and Their Local Counterparts: The Evolving Relationship of Mass-SFR-Metallicity Since z ˜ 2.1

    NASA Astrophysics Data System (ADS)

    Grasshorn Gebhardt, Henry S.; Zeimann, Gregory R.; Ciardullo, Robin; Gronwall, Caryl; Hagen, Alex; Bridge, Joanna S.; Schneider, Donald P.; Trump, Jonathan R.

    2016-01-01

    We explore the evolution of the Stellar Mass-Star Formation Rate (SFR)-Metallicity relation using a set of 256 COSMOS and GOODS galaxies in the redshift range 1.90 < z < 2.35. We present the galaxies’ rest-frame optical emission-line fluxes derived from IR-grism spectroscopy with the Hubble Space Telescope and combine these data with SFRs and stellar masses obtained from deep, multi-wavelength (rest-frame UV to IR) photometry. We then compare these measurements to those for a local sample of galaxies carefully matched in stellar mass (7.5≲ {log}({M}*/{M}⊙ )≲ 10.5) and SFR (-0.5≲ {log}({{SFR}})≲ 2.5 in M⊙ yr-1). We find that the distribution of z ˜ 2.1 galaxies in stellar mass-SFR-metallicity space is clearly different from that derived for our sample of similarly bright ({L}{{H}β }\\gt 3× {10}40 erg s-1) local galaxies, and this offset cannot be explained by simple systematic offsets in the derived quantities. At stellar masses above ˜ {10}9 {M}⊙ and SFRs above ˜ 10 {M}⊙ yr-1, the z ˜ 2.1 galaxies have higher oxygen abundances than their local counterparts, while the opposite is true for lower-mass, lower-SFR systems.

  19. EVIDENCE FOR WIDESPREAD ACTIVE GALACTIC NUCLEUS ACTIVITY AMONG MASSIVE QUIESCENT GALAXIES AT z {approx} 2

    SciTech Connect

    Olsen, Karen P.; Rasmussen, Jesper; Toft, Sune; Zirm, Andrew W.

    2013-02-10

    We quantify the presence of active galactic nuclei (AGNs) in a mass-complete (M {sub *} > 5 Multiplication-Sign 10{sup 10} M {sub Sun }) sample of 123 star-forming and quiescent galaxies at 1.5 {<=} z {<=} 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey. 41% {+-} 7% of the galaxies are detected directly in X-rays, 22% {+-} 5% with rest-frame 0.5-8 keV luminosities consistent with hosting luminous AGNs (L {sub 0.5-8keV} > 3 Multiplication-Sign 10{sup 42} erg s{sup -1}). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGNs are triggered by external effects such as mergers. We detect significant mean X-ray signals in stacked images for both the individually non-detected star-forming and quiescent galaxies, with spectra consistent with star formation only and/or a low-luminosity AGN in both cases. Comparing star formation rates inferred from the 2-10 keV luminosities to those from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative of low-luminosity AGNs. Among the quiescent galaxies, the excess suggests that as many as 70%-100% of these contain low- or high-luminosity AGNs, while the corresponding fraction is lower among star-forming galaxies (43%-65%). Our discovery of the ubiquity of AGNs in massive, quiescent z {approx} 2 galaxies provides observational support for the importance of AGNs in impeding star formation during galaxy evolution.

  20. The FMOS-COSMOS survey of star-forming galaxies at z ∼ 1.6. II. The mass-metallicity relation and the dependence on star formation rate and dust extinction

    SciTech Connect

    Zahid, H. J.; Sanders, D. B.; Chu, J.; Hasinger, G.; Kashino, D.; Silverman, J. D.; Kewley, L. J.; Daddi, E.; Renzini, A.; Rodighiero, G.; Nagao, T.; Arimoto, N.; Kartaltepe, J.; Lilly, S. J.; Carollo, C. M.; Maier, C.; Geller, M. J.; Capak, P.; Ilbert, O.; Kajisawa, M.; Collaboration: COSMOS Team; and others

    2014-09-01

    We investigate the relationships between stellar mass, gas-phase oxygen abundance (metallicity), star formation rate (SFR), and dust content of star-forming galaxies at z ∼ 1.6 using Subaru/FMOS spectroscopy in the COSMOS field. The mass-metallicity (MZ) relation at z ∼ 1.6 is steeper than the relation observed in the local universe. The steeper MZ relation at z ∼ 1.6 is mainly due to evolution in the stellar mass where the MZ relation begins to turnover and flatten. This turnover mass is 1.2 dex larger at z ∼ 1.6. The most massive galaxies at z ∼ 1.6 (∼10{sup 11} M {sub ☉}) are enriched to the level observed in massive galaxies in the local universe. The MZ relation we measure at z ∼ 1.6 supports the suggestion of an empirical upper metallicity limit that does not significantly evolve with redshift. We find an anti-correlation between metallicity and SFR for galaxies at a fixed stellar mass at z ∼ 1.6, which is similar to trends observed in the local universe. We do not find a relation between stellar mass, metallicity, and SFR that is independent of redshift; rather, our data suggest that there is redshift evolution in this relation. We examine the relation between stellar mass, metallicity, and dust extinction, and find that at a fixed stellar mass, dustier galaxies tend to be more metal rich. From examination of the stellar masses, metallicities, SFRs, and dust extinctions, we conclude that stellar mass is most closely related to dust extinction.

  1. Hubble Space Telescope Hx Imaging of Star-forming Galaxies at z approximately equal to 1-1.5: Evolution in the Size and Luminosity of Giant H II Regions

    NASA Technical Reports Server (NTRS)

    Livermore, R. C.; Jones, T.; Richard, J.; Bower, R. G.; Ellis, R. S.; Swinbank, A. M.; Rigby, J. R.; Smail, Ian; Arribas, S.; Rodriguez-Zaurin, J.; Colina, L.; Ebeling, H.; Crain, R. A.

    2013-01-01

    We present Hubble Space Telescope/Wide Field Camera 3 narrow-band imaging of the Ha emission in a sample of eight gravitationally lensed galaxies at z = 1-1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360 pc, as well as providing magnifications in flux ranging from approximately 10× to approximately 50×. This enables us to identify resolved star-forming HII regions at this epoch and therefore study their Ha luminosity distributions for comparisons with equivalent samples at z approximately 2 and in the local Universe. We find evolution in the both luminosity and surface brightness of HII regions with redshift. The distribution of clump properties can be quantified with an HII region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that 'clumpy' galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their HII regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disc shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilize the disc.

  2. Some stars are totally metal: a new mechanism driving dust across star-forming clouds, and consequences for planets, stars, and galaxies

    SciTech Connect

    Hopkins, Philip F.

    2014-12-10

    Dust grains in neutral gas behave as aerodynamic particles, so they can develop large local density fluctuations entirely independent of gas density fluctuations. Specifically, gas turbulence can drive order-of-magnitude 'resonant' fluctuations in the dust density on scales where the gas stopping/drag timescale is comparable to the turbulent eddy turnover time. Here we show that for large grains (size ≳ 0.1 μm, containing most grain mass) in sufficiently large molecular clouds (radii ≳ 1-10 pc, masses ≳ 10{sup 4} M {sub ☉}), this scale becomes larger than the characteristic sizes of prestellar cores (the sonic length), so large fluctuations in the dust-to-gas ratio are imprinted on cores. As a result, star clusters and protostellar disks formed in large clouds should exhibit significant abundance spreads in the elements preferentially found in large grains (C, O). This naturally predicts populations of carbon-enhanced stars, certain highly unusual stellar populations observed in nearby open clusters, and may explain the 'UV upturn' in early-type galaxies. It will also dramatically change planet formation in the resulting protostellar disks, by preferentially 'seeding' disks with an enhancement in large carbonaceous or silicate grains. The relevant threshold for this behavior scales simply with cloud densities and temperatures, making straightforward predictions for clusters in starbursts and high-redshift galaxies. Because of the selective sorting by size, this process is not necessarily visible in extinction mapping. We also predict the shape of the abundance distribution—when these fluctuations occur, a small fraction of the cores may actually be seeded with abundances Z ∼ 100 (Z) such that they are almost 'totally metal' (Z ∼ 1)! Assuming the cores collapse, these totally metal stars would be rare (1 in ∼10{sup 4} in clusters where this occurs), but represent a fundamentally new stellar evolution channel.

  3. The North Galactic Pole +30° Zone Galaxies. I. A Comparative Study of Galaxies with Different Nuclear Activity

    NASA Astrophysics Data System (ADS)

    Petrosian, Artashes; McLean, Brian; Allen, Ron; Kunth, Daniel; Leitherer, Claus

    2008-03-01

    A database containing 618 active and star-forming (A/SF) galaxies and 564 normal galaxies in a 120° × 6° wide strip crossing the north Galactic pole was constructed in order to compare the global properties of "active" galaxies against a control sample of "normal" galaxies. This database combines a literature and catalog search with new optical measurements from the Fpg (red) and Jpg (blue) band images of the STScI Digitized Sky Survey (DSS). We provide alternative names, accurate coordinates, morphological type, activity classes, red and blue apparent magnitudes, 2MASS near-infrared J-H and H-K colors, apparent diameters, axial ratios, position angles, and number counts of neighboring objects in a circle of radius 50 kpc. We also present an atlas of 103 interacting and merging systems among these galaxies. The integrated properties of A/SF and normal galaxies in this sample are compared using a multivariate factor analysis, which reveals that A/SF galaxies are objects with relatively late morphological types, and are more inclined and have bluer optical colors than normal galaxies. In this sample, all merging and interacting galaxies are A/SF objects. Star-forming galaxies are objects with relatively late morphological types, lower absolute luminosities and linear sizes, bluer colors, and higher inclination than sample X-ray or radio sources, as well as Seyfert galaxies. The near-infrared colors of the sample galaxies are independent parameters and do not correlate with activity level or any other parameter of the galaxies.

  4. A star-forming shock front in radio galaxy 4C+41.17 resolved with laser-assisted adaptive optics spectroscopy

    SciTech Connect

    Steinbring, Eric

    2014-07-01

    Near-infrared integral-field spectroscopy of redshifted [O III], Hβ, and optical continuum emission from the z = 3.8 radio galaxy 4C+41.17 is presented, obtained with the laser-guide-star adaptive optics facility on the Gemini North telescope. Employing a specialized dithering technique, a spatial resolution of 0.''10, or 0.7 kpc, is achieved in each spectral element, with a velocity resolution of ∼70 km s{sup –1}. Spectra similar to local starbursts are found for bright knots coincident in archival Hubble Space Telescope ( HST) rest-frame ultraviolet images, which also allows a key line diagnostic to be mapped together with new kinematic information. There emerges a clearer picture of the nebular emission associated with the jet in 8.3 GHz and 15 GHz Very Large Array maps, closely tied to a Lyα-bright shell-shaped structure seen with HST. This supports a previous interpretation of that arc tracing a bow shock, inducing ∼10{sup 10–11} M {sub ☉} star formation regions that comprise the clumpy broadband optical/ultraviolet morphology near the core.

  5. Where Stars Form: Inside-out Growth and Coherent Star Formation from HST Hα Maps of 3200 Galaxies across the Main Sequence at 0.7 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Nelson, Erica June; van Dokkum, Pieter G.; Förster Schreiber, Natascha M.; Franx, Marijn; Brammer, Gabriel B.; Momcheva, Ivelina G.; Wuyts, Stijn; Whitaker, Katherine E.; Skelton, Rosalind E.; Fumagalli, Mattia; Hayward, Christopher C.; Kriek, Mariska; Labbé, Ivo; Leja, Joel; Rix, Hans-Walter; Tacconi, Linda J.; van der Wel, Arjen; van den Bosch, Frank C.; Oesch, Pascal A.; Dickey, Claire; Ulf Lange, Johannes

    2016-09-01

    We present Hα maps at 1 kpc spatial resolution for star-forming galaxies at z ˜ 1, made possible by the Wide Field Camera 3 grism on Hubble Space Telescope (HST). Employing this capability over all five 3D-HST/CANDELS fields provides a sample of 3200 galaxies enabling a division into subsamples based on stellar mass and star formation rate (SFR). By creating deep stacked Hα images, we reach surface brightness limits of 1 × 10‑18 erg s‑1 cm‑2 arcsec‑2, allowing us to map the distribution of ionized gas to ˜10 kpc for typical L* galaxies at this epoch. We find that the spatial extent of the Hα distribution increases with stellar mass as {r}{{H}α }=1.5{({M}* /{10}10{M}ȯ )}0.23 kpc. The Hα emission is more extended than the stellar continuum emission, consistent with inside-out assembly of galactic disks. This effect grows stronger with mass as {r}{{H}α }/{r}* =1.1 {({M}* /{10}10{M}ȯ )}0.054. We map the Hα distribution as a function of SFR(IR+UV) and find evidence for “coherent star formation” across the SFR–M * plane: above the main sequence (MS), Hα is enhanced at all radii; below the MS, Hα is depressed at all radii. This suggests that at all masses the physical processes driving the enhancement or suppression of star formation act throughout the disks of galaxies. At high masses ({10}10.5\\lt {M}* /{M}ȯ \\lt {10}11), above the MS, Hα is particularly enhanced in the center, potentially building bulges and/or supermassive black holes. Below the MS, a strong central dip in the EW(Hα), as well as the inferred specific SFR, appears. Importantly, though, across the entirety of the SFR–M * plane, the absolute SFR as traced by Hα is always centrally peaked, even in galaxies below the MS.

  6. Where Stars Form: Inside-out Growth and Coherent Star Formation from HST Hα Maps of 3200 Galaxies across the Main Sequence at 0.7 < z < 1.5

    NASA Astrophysics Data System (ADS)

    Nelson, Erica June; van Dokkum, Pieter G.; Förster Schreiber, Natascha M.; Franx, Marijn; Brammer, Gabriel B.; Momcheva, Ivelina G.; Wuyts, Stijn; Whitaker, Katherine E.; Skelton, Rosalind E.; Fumagalli, Mattia; Hayward, Christopher C.; Kriek, Mariska; Labbé, Ivo; Leja, Joel; Rix, Hans-Walter; Tacconi, Linda J.; van der Wel, Arjen; van den Bosch, Frank C.; Oesch, Pascal A.; Dickey, Claire; Ulf Lange, Johannes

    2016-09-01

    We present Hα maps at 1 kpc spatial resolution for star-forming galaxies at z ˜ 1, made possible by the Wide Field Camera 3 grism on Hubble Space Telescope (HST). Employing this capability over all five 3D-HST/CANDELS fields provides a sample of 3200 galaxies enabling a division into subsamples based on stellar mass and star formation rate (SFR). By creating deep stacked Hα images, we reach surface brightness limits of 1 × 10-18 erg s-1 cm-2 arcsec-2, allowing us to map the distribution of ionized gas to ˜10 kpc for typical L* galaxies at this epoch. We find that the spatial extent of the Hα distribution increases with stellar mass as {r}{{H}α }=1.5{({M}* /{10}10{M}⊙ )}0.23 kpc. The Hα emission is more extended than the stellar continuum emission, consistent with inside-out assembly of galactic disks. This effect grows stronger with mass as {r}{{H}α }/{r}* =1.1 {({M}* /{10}10{M}⊙ )}0.054. We map the Hα distribution as a function of SFR(IR+UV) and find evidence for “coherent star formation” across the SFR-M * plane: above the main sequence (MS), Hα is enhanced at all radii; below the MS, Hα is depressed at all radii. This suggests that at all masses the physical processes driving the enhancement or suppression of star formation act throughout the disks of galaxies. At high masses ({10}10.5\\lt {M}* /{M}⊙ \\lt {10}11), above the MS, Hα is particularly enhanced in the center, potentially building bulges and/or supermassive black holes. Below the MS, a strong central dip in the EW(Hα), as well as the inferred specific SFR, appears. Importantly, though, across the entirety of the SFR-M * plane, the absolute SFR as traced by Hα is always centrally peaked, even in galaxies below the MS.

  7. Accurate positions of SiO masers in active star-forming regions - Orion-KL, W51-IRS2, and Sagittarius-B2 MD5

    NASA Astrophysics Data System (ADS)

    Morita, Koh-Ichiro; Hasegawa, Tetsuo; Ukita, Nobuharu; Okumura, Sachiko K.; Ishiguro, Masato

    1992-08-01

    Accurate positional measurements of SiO J = 1-0 masers in active star-forming regions, Orion-KL, W51-IRS2, and Sgr-B2 MD5, were made with the Nobeyama Millimeter Array. Absolute positional accuracies of 0.12-0.6 arcsec were achieved. The SiO maser in W51-IRS2 is located within 0.4 arcsec (0.5 x 10 exp 17 cm at the distance of W51-IRS2) of the strongest H2O masers. In Sgr-B2 MD5, the SiO maser coincides with the strongest H2O masers, most of the strong OH masers, and the peak of radio continuum emission from the ultracompact H II region within 0.7 arcsec (0.8 x 10 exp 17 cm at the distance of Sgr-B2). Peaks of the emission from hot NH3 were found to exist within about 1 arcsec of the SiO masers in both regions. The precise positional coincidence confirms our former conclusion that the SiO masers in W51-IRS2 and Sgr-B2 MD5 are actually associated with the ongoing activity of star formation, as is the case of Orion-KL.

  8. Cosmic web and star formation activity in galaxies at z ∼ 1

    SciTech Connect

    Darvish, B.; Mobasher, B.; Sales, L. V.; Sobral, D.; Scoville, N. Z.; Best, P.; Smail, I.

    2014-11-20

    We investigate the role of the delineated cosmic web/filaments on star formation activity by exploring a sample of 425 narrow-band selected Hα emitters, as well as 2846 color-color selected underlying star-forming galaxies for a large-scale structure at z = 0.84 in the COSMOS field from the HiZELS survey. Using the scale-independent Multi-scale Morphology Filter algorithm, we are able to quantitatively describe the density field and disentangle it into its major components: fields, filaments, and clusters. We show that the observed median star formation rate (SFR), stellar mass, specific SFR, the mean SFR-mass relation, and its scatter for both Hα emitters and underlying star-forming galaxies do not strongly depend on different classes of environment, in agreement with previous studies. However, the fraction of Hα emitters varies with environment and is enhanced in filamentary structures at z ∼ 1. We propose mild galaxy-galaxy interactions as the possible physical agent for the elevation of the fraction of Hα star-forming galaxies in filaments. Our results show that filaments are the likely physical environments that are often classed as the 'intermediate' densities and that the cosmic web likely plays a major role in galaxy formation and evolution which has so far been poorly investigated.

  9. After the Interaction: an Efficiently Star-forming Molecular Disk in NGC 5195

    NASA Astrophysics Data System (ADS)

    Alatalo, Katherine; Aladro, Rebeca; Nyland, Kristina; Aalto, Susanne; Bitsakis, Theodoros; Gallagher, John S.; Lanz, Lauranne

    2016-10-01

    We present new molecular gas maps of NGC 5195 (alternatively known as M51b) from the Combined Array for Research in Millimeter Astronomy, including 12CO(1–0), 13CO(1–0), CN(1{}{0,2}–{0}{0,1}), CS(2–1), and 3 mm continuum. We also detected HCN(1–0) and HCO+(1–0) using the Onsala Space Observatory. NGC 5195 has a 12CO/13CO ratio ({{ R }}12/13 = 11.4 ± 0.5) consistent with normal star-forming galaxies. The CN(1–0) intensity is higher than is seen in an average star-forming galaxy, possibly enhanced in the diffuse gas in photo-dissociation regions. Stellar template fitting of the nuclear spectrum of NGC 5195 shows two stellar populations: an 80% mass fraction of old (≳10 Gyr) and a 20% mass fraction of intermediate-aged (≈1 Gyr) stellar populations. This provides a constraint on the timescale over which NGC 5195 experienced enhanced star formation during its interaction with M51a. The average molecular gas depletion timescale in NGC 5195 is < {τ }{dep}> = 3.08 Gyr, a factor of ≈ 2 larger than the depletion timescales in nearby star-forming galaxies, but consistent with the depletion seen in CO-detected early-type galaxies. While radio continuum emission at centimeter and millimeter wavelengths is present in the vicinity of the nucleus of NGC 5195, we find it is most likely associated with nuclear star formation rather than radio-loud AGN activity. Thus, despite having a substantial interaction with M51a ∼1/2 Gyr ago, the molecular gas in NGC 5195 has resettled and is currently forming stars at an efficiency consistent with settled early-type galaxies.

  10. An Initial Investigation of Active Galaxies in RESOLVE and ECO

    NASA Astrophysics Data System (ADS)

    Norman, Dara J.; Kannappan, Sheila; Bittner, Ashley; Yarber, Aara'L.; Hoversten, Erik A.; Stark, David; RESOLVE Team

    2016-01-01

    The volume-limited REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey and its complementary Environmental COntext (ECO) catalog are dominated by low mass, gas-rich galaxies, as is typical of the bulk of large-scale structure in the local universe. These surveys, therefore, provide an excellent opportunity to investigate the complete large-scale environments of low-redshift AGN and nuclear starbursts in such galaxies, in order to search for external triggering, examine activity in relation to gas supply, and investigate the role of feedback. By data-mining multi-wavelength catalogs that use varied techniques, we identify known AGN in RESOLVE and ECO, including a population of gas-dominated low-mass galaxies. We take advantage of these surveys' multi-wavelength supporting data to investigate triggering, feedback, and the roles of environment and gas supply in this initial sample of active galaxies. Because biases in standard AGN candidate selection techniques (e.g. BPT, X-ray luminosity) make them individually poor selectors of AGN activity in star-forming and low mass (<10^10 Msun) host galaxies, we also seek to improve the identification of nuclear activity in such galaxies via combined analysis of star formation and AGN signatures. RESOLVE is supported by NSF grant AST-0955368

  11. VizieR Online Data Catalog: Star-forming compact groups (Hernandez-Fernandez+, 2015)

    NASA Astrophysics Data System (ADS)

    Hernandez-Fernandez, J. D.; Mendes de Oliveira, C.

    2016-03-01

    This article provides a local sample (z<~0.15) of compact groups of star-forming galaxies. In this type of groups, galaxies strongly interact among themselves and with the rest of the group components (ICM, dark matter halo). This induces morphological changes and star formation events which are currently taking place. The peculiar evolutionary stage of these groups provides a wealth of galaxy observables that may clarify the theoretical framework about galaxy evolution in groups. We have performed an all-sky search for compact groups of star-forming galaxies in the GALEX UV catalogues. (3 data files).

  12. Are passive red spirals truly passive?. The current star formation activity of optically red disc galaxies

    NASA Astrophysics Data System (ADS)

    Cortese, L.

    2012-07-01

    We used GALEX ultraviolet and WISE 22 μm observations to investigate the current star formation activity of the optically red spirals recently identified as part of the Galaxy Zoo project. These galaxies were accurately selected from the Sloan Digital Sky Survey as pure discs with low or no current star formation activity, representing one of the best optically selected samples of candidate passive spirals. However, we show that these galaxies are not only still forming stars at a significant rate (≳1 M⊙ yr-1) but, more importantly, their star formation activity is not different from that of normal star-forming discs of the same stellar mass (M∗ ≳ 1010.2 M⊙). Indeed, these systems lie on the UV-optical blue sequence, even without any corrections for internal dust attenuation, and they follow the same specific star formation rate vs. stellar mass relation of star-forming galaxies. Our findings clearly show that at high stellar masses, optical colours do not allow to distinguish between actively star-forming and truly quiescent systems.

  13. ENVIRONMENTAL DEPENDENCE OF OTHER GALAXY PROPERTIES FOR THE SAME STAR FORMATION ACTIVITIES

    SciTech Connect

    Deng Xinfa; Bei Yang; He Jizhou; Tang Xiaoxun

    2010-01-01

    Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 6 above and below the value of M*, we have investigated the environmental dependence of other galaxy properties for the same star formation activities. Only in the luminous passive class, a strong environmental dependence of the g - r color is observed, but the environmental dependence of other properties in this class is very weak. In other classes, we can conclude that the local density dependence of luminosity, g - r color, concentration index ci, and morphologies for star-forming galaxies and passive ones is much weaker than that obtained in the volume-limited Main galaxy samples. This suggests that star formation activity is a galaxy property very predictive of the local environment. In addition, we also note that passive galaxies are more luminous, redder, highly concentrated, and preferentially 'early type'.

  14. Carbon Dioxide in Star-forming Regions.

    PubMed

    Charnley; Kaufman

    2000-02-01

    We consider the gas-phase chemistry of CO2 molecules in active regions. We show that CO2 molecules evaporated from dust in hot cores cannot be efficiently destroyed and are in fact copiously produced in cooler gas. When CO2-rich ices are sputtered in strong MHD shock waves, the increase in atomic hydrogen, due to H2 dissociation by ion-neutral streaming, means that CO2 can be depleted by factors of approximately 500 from its injected abundance. We find that a critical shock speed exists at higher preshock densities below which CO2 molecules can be efficiently sputtered but survive in the postshock gas. These calculations offer an explanation for the low gas/solid CO2 ratios detected by the Infrared Space Observatory in star-forming cores as being due to shock destruction followed by partial reformation in warm gas. The presence of high abundances of CO2 in the strongly shocked Galactic center clouds Sgr B2 and Sgr A also find a tentative explanation in this scenario. Shock activity plays an important role in determining the chemistry of star-forming regions, and we suggest that most hot cores are in fact shocked cores.

  15. Hot X-ray emitting gas in galaxies

    NASA Astrophysics Data System (ADS)

    Fabbiano, G.

    2003-04-01

    Hot X-ray emitting gas was discovered in galaxies with the Einstein Observatory, 25 year ago. This hot Interstellar Medium (ISM) may be in thermal equilibrium with the stars in large galaxy bulges (e.g. elliptical and lenticular galaxies) or may be heated by supernovae (SNIa). In star-forming galaxies (spirals, irregulars, merging galaxies) the ISM may be heated by star formation activity, via stellar winds and most efficiently supernova explosions. In this talk I will address recent Chandra observations of hot ISM in star-forming galaxies. X-ray observations of nearby galaxies, in combination with data from other regions of the electromagnetic spectrum, have revealed a complex multi-phase ISM in active star forming regions. Hot super-winds are seen escaping star-burst nuclei, undoubtly carrying with them elements into the intergalactic space. The study of these galaxies may give us a direct (albeit down-scaled) view of galaxy formation in act.

  16. The Compact Star-forming Complex at the Heart of NGC 253

    NASA Astrophysics Data System (ADS)

    Davidge, T. J.

    2016-02-01

    We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during subarcsecond seeing conditions. Absorption features in the spectrum of the star-forming complex are weaker than in the surroundings. An absorption feature is found near 1.78 μm that coincides with the location of a C2 bandhead. If this feature is due to C2 then the star-forming complex has been in place for at least a few hundred Myr. Emission lines of Brγ, [Fe ii], and He i 2.06 μm do not track the NIR continuum light. Pockets of star-forming activity that do not have associated concentrations of red supergiants, and so likely have ages <8 Myr, are found along the western edge of the complex, and there is evidence that one such pocket contains a rich population of Wolf-Rayet stars. Unless the star-forming complex is significantly more metal-poor than the surroundings, then a significant fraction of its total mass is in stars with ages <8 Myr. If the present-day star formation rate is maintained then the timescale to double its stellar mass ranges from a few Myr to a few tens of Myr, depending on the contribution made by stars older than ˜8 Myr. If—as suggested by some studies—the star-forming complex is centered on the galaxy’s nucleus, which presumably contains a large population of old and intermediate-age stars, then the nucleus of NGC 253 is currently experiencing a phase of rapid growth in its stellar mass. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  17. A two-parameter model for the infrared/submillimeter/radio spectral energy distributions of galaxies and active galactic nuclei

    SciTech Connect

    Dale, Daniel A.; Helou, George; Magdis, Georgios E.; Armus, Lee; Díaz-Santos, Tanio; Shi, Yong

    2014-03-20

    A two-parameter semi-empirical model is presented for the spectral energy distributions of galaxies with contributions to their infrared-submillimeter-radio emission from both star formation and accretion disk-powered activity. This model builds upon a previous one-parameter family of models for star-forming galaxies, and includes an update to the mid-infrared emission using an average template obtained from Spitzer Space Telescope observations of normal galaxies. Star-forming/active galactic nucleus (AGN) diagnostics based on polycyclic aromatic hydrocarbon equivalent widths and broadband infrared colors are presented, and example mid-infrared AGN fractional contributions are estimated from model fits to the Great Observatories All-Sky LIRG Survey sample of nearby U/LIRGS and the Five mJy Unbiased Spitzer Extragalactic Survey sample of 24 μm selected sources at redshifts 0 ≲ z ≲ 4.

  18. Variable spectra of active galaxies

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1988-01-01

    The analysis of EXOSAT spectra of active galaxies are presented. The objects examined for X-ray spectral variability were MR 2251-178 and 3C 120. The results of these investigations are described, as well as additional results on X-ray spectral variability related to EXOSAT observations of active galaxies. Additionally, the dipping X-ray source 4U1624-49 was also investigated.

  19. Epsiodic Activity in Radio Galaxies

    SciTech Connect

    Saikia, D.J.; Konar, C.; Jamrozy, M.; Machalski, J.; Gupta, Neeraj; Stawarz, L.; Mack, K.-H.; Siemiginowska, A.; /Harvard-Smithsonian Ctr. Astrophys.

    2007-10-15

    One of the interesting issues in our understanding of active galactic nuclei is the duration of their active phase and whether such activity is episodic. In this paper we summarize our recent results on episodic activity in radio galaxies obtained with the GMRT and the VLA.

  20. Hunting for Infrared Signatures of Supermassive Black Hole Activity in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Hainline, Kevin; Reines, Amy; Greene, Jenny; Stern, Daniel

    2016-08-01

    In order to explore the origin of the relationship between the growth of a galaxy and its central supermassive black hole, evidence must be found for black holes in galaxies at a wide range in masses. Searching for supermassive black holes in dwarf galaxies is especially important as these objects have less complicated merger histories, and they may host black holes that are similar to early proposed ``seed'' black holes. However, this selection is complicated by the fact that star formation in these dwarf galaxies can often mask the optical signatures of supermassive black hole growth and active galactic nucleus (AGN) activity in these objects. The all-sky infrared coverage offered by the Wide-field Infrared Survey Explorer (WISE) has been used to great success to select AGNs in more massive galaxies, but great care must be used when using infrared selection techniques on samples of dwarf galaxies. In particular, compact, highly star-forming dwarf galaxies can have infrared colors that may lead them to be erroneously selected as AGNs. In this talk, I will discuss recent work exploring infrared selection of AGN candidates in dwarf galaxies, and present a set of potential IR dwarf-galaxy AGN candidates. I will also outline the importance in these results with respect to future selection of AGNs in low-metallicity galaxies at high-redshift.

  1. The star formation rates of active galactic nuclei host galaxies

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Teimoorinia, Hossen; Rosario, David J.; Mendel, J. Trevor

    2016-05-01

    Using artificial neural network predictions of total infrared luminosities (LIR), we compare the host galaxy star formation rates (SFRs) of ˜21 000 optically selected active galactic nuclei (AGN), 466 low-excitation radio galaxies (LERGs) and 721 mid-IR-selected AGN. SFR offsets (ΔSFR) relative to a sample of star-forming `main-sequence' galaxies (matched in M⋆, z and local environment) are computed for the AGN hosts. Optically selected AGN exhibit a wide range of ΔSFR, with a distribution skewed to low SFRs and a median ΔSFR = -0.06 dex. The LERGs have SFRs that are shifted to even lower values with a median ΔSFR = -0.5 dex. In contrast, mid-IR-selected AGN have, on average, SFRs enhanced by a factor of ˜1.5. We interpret the different distributions of ΔSFR amongst the different AGN classes in the context of the relative contribution of triggering by galaxy mergers. Whereas the LERGs are predominantly fuelled through low accretion rate secular processes which are not accompanied by enhancements in SFR, mergers, which can simultaneously boost SFRs, most frequently lead to powerful, obscured AGN.

  2. [Molecular spectral diagnosis of star forming regions].

    PubMed

    Xi, S; Qin, S; Deng, L; Yang, J

    2001-08-01

    Stars are the basic building blocks of our universe, therefore it is one of the most important research topics in astrophysics to understand the origin and the early evolution of these objects. The current picture is that stars are formed during the collapse of a large enough self-gravitating interstellar molecular cloud. The early collapse gives birth to a fetus of a star, which is surrounded by a rotating accretion disk. The proto-star accretes interstellar matter through the disk which in turn transfer the accumulated matter to the central proto-star, then the star gets weight during the process. Observation shows that gorgeous ejection of matter always come along with the accretion process. In the presence of disks, these outflows usually escape from the system along the axis of the disk, forming so called bipolar outflows. Typical tracers of these activities are rich molecules such as CO, SiC2, C3H, C3H2 etc. Observationally, such typical molecular outflows can be detected using Doppler effect by spectroscopic measurements. Using the 13.7 m radio telescope in Delingha station of Purple Mountain Observatory, we performed a survey for 12 low temperature IRAS objects, some of the sources show high velocity properties. Detailed analysis of the Doppler profiles of IRS34 is presented. Star forming activities are clearly seen in this field. PMID:12945260

  3. Measuring star formation rates in blue galaxies

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Hunter, Deidre A.

    1987-01-01

    The problems associated with measurements of star formation rates in galaxies are briefly reviewed, and specific models are presented for determinations of current star formation rates from H alpha and Far Infrared (FIR) luminosities. The models are applied to a sample of optically blue irregular galaxies, and the results are discussed in terms of star forming histories. It appears likely that typical irregular galaxies are forming stars at nearly constant rates, although a few examples of systems with enhanced star forming activity are found among HII regions and luminous irregular galaxies.

  4. THE ROLE OF GALAXY INTERACTION IN ENVIRONMENTAL DEPENDENCE OF THE STAR FORMATION ACTIVITY AT z {approx_equal} 1.2

    SciTech Connect

    Ideue, Y.; Taniguchi, Y.; Shioya, Y.; Kajisawa, M.; Nagao, T.; Trump, J. R.; Iovino, A.; Koekemoer, A. M.; Le Fevre, O.; Ilbert, O.; Scoville, N. Z.

    2012-03-01

    In order to understand environmental effects on star formation in high-redshift galaxies, we investigate the physical relationships between the star formation activity, stellar mass, and environment for z {approx_equal} 1.2 galaxies in the 2 deg{sup 2} COSMOS field. We estimate star formation using the [O II]{lambda}3727 emission line and environment from the local galaxy density. Our analysis shows that for massive galaxies (M{sub *} {approx}> 10{sup 10} M{sub Sun }), the fraction of [O II] emitters in high-density environments ({Sigma}{sub 10th} {approx}> 3.9 Mpc{sup -2}) is 1.7 {+-} 0.4 times higher than in low-density environments ({Sigma}{sub 10th} {approx}< 1.5 Mpc{sup -2}), while the [O II] emitter fraction does not depend on environment for low-mass M{sub *} {approx}< 10{sup 10} M{sub Sun} galaxies. In order to understand what drives these trends, we investigate the role of companion galaxies in our sample. We find that the fraction of [O II] emitters in galaxies with companions is 2.4 {+-} 0.5 times as high as that in galaxies without companions at M{sub *} {approx}> 10{sup 10} M{sub Sun }. In addition, massive galaxies are more likely to have companions in high-density environments. However, although the number of star-forming galaxies increases for massive galaxies with close companions and in dense environments, the average star formation rate of star-forming galaxies at a given mass is independent of environment and the presence/absence of a close companion. These results suggest that interactions and/or mergers in a high-density environment could induce star formation in massive galaxies at z {approx} 1.2, increasing the fraction of star-forming galaxies with M{sub *} {approx}> 10{sup 10} M{sub Sun }.

  5. Looking Closely at "Medusa": Star Forming Regions in NGC 4194

    NASA Technical Reports Server (NTRS)

    Weistrop, D.; Eggers, D.; Nelson, C. H.; Kaiser, M. E.

    2004-01-01

    The "Medusa" (NGC 4194, Mrk 201) is a blue compact galaxy, with strong far infrared and radio emission. Ground-based observations exhibit a distorted image with a tidal tail and regions of strong star formation. A population of massive O and early B stars is evident from the IUE spectra HST survey of Seyfert and starburst galaxies notes NCG 4194 is an HII galaxy with lumpy HII regions and knots. The central starburst is apparently produced by a galaxy merger. As part of an investigation of star formation in interacting galaxies, we have obtained ultraviolet and visible images of the central regions of NGC 4194 with the Space Telescope Imaging Spectrograph on HST. Imaging was obtained in two ultraviolet (FUV-MAMA+F25QTZ, NUV-MAMA+F25CN182) and one visible (CCD+F28X50LP) band. Individual star forming knots (at HST resolution) have been identified. We present sized and luminosities for the individual knots, and the knot luminosity function. We compare our data to current starburst models to constrain stellar ages and populations. Knot characteristics as a function of location in the galaxy will also be discussed.

  6. Isolated Star-Forming Cloud Discovered in Intracluster Space

    NASA Astrophysics Data System (ADS)

    2003-01-01

    galaxies, Messier 86 and Messier 84, indicate the presence of other isolated HII regions, thus suggesting that isolated star formation may occur more generally in galaxies. If so, this process may provide a natural explanation to the current riddle why some young stars are found high up in the halo of our own Milky Way galaxy, far from the star-forming clouds in the main plane. The Virgo Cluster ESO PR Photo 04a/03 ESO PR Photo 04a/03 [Preview - JPEG: 400 x 428 pix - 74k [Normal - JPEG: 800 x 855 pix - 408k] [Hi-Res - JPEG: 4252 x 4544 pix - 10.3M] ESO PR Photo 04b/03 ESO PR Photo 04b/03 [Preview - JPEG: 433 x 400 pix - 60k [Normal - JPEG: 865 x 800 pix - 456k] [Hi-Res - JPEG: 3077 x 2847 pix - 4.2M] Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000 with the Wide Field Imager (WFI) at the La Silla Observatory (exposure 6 x 5 min; red R-band; seeing 1.3 arcsec). The large elliptical galaxy at the centre is Messier 84; the elongated image of NGC 4388 (an active spiral galaxy, seen from the side) is in the lower left corner. The field measures 16.9 x 15.7 arcmin2. PR Photo 04b/03 shows a larger region of the Virgo cluster, with the galaxies Messier 86 (at the upper edge of the field, to the left of the centre), as well as Messier 84 (upper right) and NGC 4388 (just below the centre) that are also seen in PR Photo 04a/03. It is reproduced from a long-exposure Subaru Suprime-Cam image, obtained in the red light of ionized hydrogen (the H-alpha spectral line at wavelength 656.2 nm). In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. The field measures 34 x 27 arcmin2. Part of this sky field is shown in colour in PR Photo 04c/03. Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000

  7. The Eagle Nebula: a spectral template for star forming regions

    NASA Astrophysics Data System (ADS)

    Flagey, Nicolas; Boulanger, Francois; Carey, Sean; Compiegne, Mathieu; Dwek, Eli; Habart, Emilie; Indebetouw, Remy; Montmerle, Thierry; Noriega-Crespo, Alberto

    2008-03-01

    IRAC and MIPS have revealed spectacular images of massive star forming regions in the Galaxy. These vivid illustrations of the interaction between the stars, through their winds and radiation, and their environment, made of gas and dust, still needs to be explained. The large scale picture of layered shells of gas components, is affected by the small scale interaction of stars with the clumpy medium that surrounds them. To understand spatial variations of physical conditions and dust properties on small scales, spectroscopic imaging observations are required on a nearby object. The iconic Eagle Nebula (M16) is one of the nearest and most observed star forming region of our Galaxy and as such, is a well suited template to obtain this missing data set. We thus propose a complete spectral map of the Eagle Nebula (M16) with the IRS/Long Low module (15-38 microns) and MIPS/SED mode (55-95 microns). Analysis of the dust emission, spectral features and continuum, and of the H2 and fine-structure gas lines within our models will provide us with constraints on the physical conditions (gas ionization state, pressure, radiation field) and dust properties (temperature, size distribution) at each position within the nebula. Only such a spatially and spectrally complete map will allow us to characterize small scale structure and dust evolution within the global context and understand the impact of small scale structure on the evolution of dusty star forming regions. This project takes advantage of the unique ability of IRS at obtaining sensitive spectral maps covering large areas.

  8. HIGH-RESOLUTION IMAGING OF WATER MASER EMISSION IN THE ACTIVE GALAXIES NGC 6240 AND M51

    SciTech Connect

    Hagiwara, Yoshiaki; Edwards, Philip G. E-mail: Philip.Edwards@csiro.au

    2015-12-20

    We present the results of observations of 22 GHz H{sub 2}O maser emission in NGC 6240 and M51 made with the Karl G. Jansky Very Large Array. Two major H{sub 2}O maser features and several minor features are detected toward the southern nucleus of NGC 6240. These features are redshifted by about 300 km s{sup −1} from the galaxy’s systemic velocity and remain unresolved at the synthesized beam size. A combination of our two-epoch observations and published data reveals an apparent correlation between the strength of the maser and the 22 GHz radio continuum emission, implying that the maser excitation relates to the activity of an active galactic nucleus in the southern nucleus rather than star-forming activity. The star-forming galaxy M51 hosts H{sub 2}O maser emission in the center of the galaxy; however, the origin of the maser has been an open question. We report the first detection of 22 GHz nuclear radio continuum emission in M51. The continuum emission is co-located with the maser position, which indicates that the maser arises from nuclear active galactic nucleus-activity and not from star-forming activity in the galaxy.

  9. A SiO 2-1 SURVEY TOWARD GAS-RICH ACTIVE GALAXIES

    SciTech Connect

    Wang, Junzhi; Zhang, Jiangshui; Shi, Yong; Zhang, Zhiyu

    2013-12-01

    In order to study the feedback from active galactic nuclei (AGNs), we performed a survey of SiO J = 2-1 (v = 0) transition toward ten gas-rich active galaxies with the IRAM 30 m telescope. As the first survey of SiO in such galaxies, we detected SiO J = 2-1 (v = 0) emission in six galaxies above the 3σ level and one galaxy (NGC 3690) at the 2.7σ level. The detection rate is not related to the AGN type or to star formation activity. In comparison with M82, which is a pure star-forming galaxy without nuclear activity, our SiO detections could not be completely ascribed to being due to star formation activity. This suggests that the AGN feedback may be efficient in producing SiO molecules in such galaxies. Further surveys with large single-dish millimeter telescopes and interferometers are necessary for understanding the origin of SiO in galaxies with nuclear activity.

  10. PHYSICAL PROPERTIES, STAR FORMATION, AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN BALMER BREAK GALAXIES AT 0 < z < 1

    SciTech Connect

    Diaz Tello, J.; Donzelli, C.; Padilla, N.; Fujishiro, N.; Yoshikawa, T.; Hanami, H.; Hatsukade, B.

    2013-07-01

    We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-active galactic nuclei (AGNs) diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to mid-infrared (MIR) Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx), and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) star-forming galaxies, two (5%) composite galaxies, and three (8%) AGNs were classified, whereas from the MEx diagram only one galaxy was classified as AGN. A total of 19 galaxies have photometry available in all the IRAC/Spitzer bands. Of these, three AGN candidates were not classified as AGN in the optical diagrams, suggesting they are dusty/obscured AGNs, or that nuclear star formation has diluted their contributions. By fitting the spectral energy distribution of the galaxies, we derived the stellar masses, dust reddening E(B - V), ages, and UV star formation rates (SFRs). Furthermore, the relationship between SFR surface density ({Sigma}{sub SFR}) and stellar mass surface density per time unit ({Sigma}{sub M{sub */{tau}}}) as a function of redshift was investigated using the [O II] {lambda}3727, 3729, H{alpha} {lambda}6563 luminosities, which revealed that both quantities are larger for higher redshift galaxies. We also studied the SFR and specific SFR (SSFR) versus stellar mass and color relations, with the more massive galaxies having higher SFR values but lower SSFR values than less massive galaxies. These results are consistent with previous ones showing that, at a given mass, high-redshift galaxies have on average larger SFR and SSFR values than low-redshift galaxies. Finally, bluer galaxies have larger SSFR values than redder

  11. Lithopanspermia in star-forming clusters.

    PubMed

    Adams, Fred C; Spergel, David N

    2005-08-01

    This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to action in the field) because of the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses approximately 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed v (eject) and number N(.) of members in the birth aggregate. The odds of any given ejected meteoroid being recaptured by another solar system are relatively low, about 1:10(3)-10(6) over the expected range of ejection speeds and cluster sizes. Because the number of ejected rocks (with mass m > 10 kg) per system can be large, N (R) approximately 10(16), virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that N (B) approximately 10(7) rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life-bearing rocks is expected to occur N (bio) asymptotically equal to 10-16,000 times (per cluster), depending on the ejection speeds. Only a small fraction (f (imp) approximately 10(4)) of the captured rocks impact the surfaces of terrestrial planets, so that N (lps) asymptotically equal to 10(3)-1.6 lithopanspermia events are expected per cluster (under favorable conditions). Finally, we discuss the question of internal versus external seeding of clusters and the possibility of Earth seeding young clusters over its biologically active lifetime.

  12. Lithopanspermia in star-forming clusters.

    PubMed

    Adams, Fred C; Spergel, David N

    2005-08-01

    This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to action in the field) because of the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses approximately 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed v (eject) and number N(.) of members in the birth aggregate. The odds of any given ejected meteoroid being recaptured by another solar system are relatively low, about 1:10(3)-10(6) over the expected range of ejection speeds and cluster sizes. Because the number of ejected rocks (with mass m > 10 kg) per system can be large, N (R) approximately 10(16), virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that N (B) approximately 10(7) rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life-bearing rocks is expected to occur N (bio) asymptotically equal to 10-16,000 times (per cluster), depending on the ejection speeds. Only a small fraction (f (imp) approximately 10(4)) of the captured rocks impact the surfaces of terrestrial planets, so that N (lps) asymptotically equal to 10(3)-1.6 lithopanspermia events are expected per cluster (under favorable conditions). Finally, we discuss the question of internal versus external seeding of clusters and the possibility of Earth seeding young clusters over its biologically active lifetime. PMID:16078868

  13. A method for determining AGN accretion phase in field galaxies

    NASA Astrophysics Data System (ADS)

    Micic, Miroslav; Martinović, Nemanja; Sinha, Manodeep

    2016-09-01

    Recent observations of active galactic nucleus (AGN) activity in massive galaxies (log M*/ M⊙ > 10.4) show the following: (1) at z < 1, AGN-hosting galaxies do not show enhanced merger signatures compared with normal galaxies, (2) also at z < 1, most AGNs are hosted by quiescent galaxies and (3) at z > 1, the percentage of AGNs in star-forming galaxies increases and becomes comparable to the AGN percentage in quiescent galaxies at z ˜ 2. How can major mergers explain AGN activity in massive quiescent galaxies that have no merger features and no star formation to indicate a recent galaxy merger? By matching merger events in a cosmological N-body simulation to the observed AGN incidence probability in the COSMOS survey, we show that major merger-triggered AGN activity is consistent with the observations. By distinguishing between `peak' AGNs (recently merger-triggered and hosted by star-forming galaxies) and `faded' AGNs (merger-triggered a long time ago and now residing in quiescent galaxies), we show that the AGN occupation fraction in star-forming and quiescent galaxies simply follows the evolution of the galaxy merger rate. Since the galaxy merger rate drops dramatically at z < 1, the only AGNs left to be observed are the ones triggered by old mergers that are now in the declining phase of their nuclear activity, hosted by quiescent galaxies. As we go towards higher redshifts, the galaxy merger rate increases and the percentages of `peak' AGNs and `faded' AGNs become comparable.

  14. Astronomers Discover New Star-Forming Regions in Milky Way

    NASA Astrophysics Data System (ADS)

    2010-05-01

    Astronomers studying the Milky Way have discovered a large number of previously-unknown regions where massive stars are being formed. Their discovery provides important new information about the structure of our home Galaxy and promises to yield new clues about the chemical composition of the Galaxy. "We can clearly relate the locations of these star-forming sites to the overall structure of the Galaxy. Further studies will allow us to better understand the process of star formation and to compare the chemical composition of such sites at widely different distances from the Galaxy's center," said Thomas Bania, of Boston University. Bania worked with Loren Anderson of the Astrophysical Laboratory of Marseille in France, Dana Balser of the National Radio Astronomy Observatory (NRAO), and Robert Rood of the University of Virginia. The scientists presented their findings to the American Astronomical Society's meeting in Miami, Florida. The star-forming regions the astronomers sought, called H II regions, are sites where hydrogen atoms are ionized, or stripped of their electrons, by the intense radiation of the massive, young stars. To find these regions hidden from visible-light detection by the Milky Way's gas and dust, the researchers used infrared and radio telescopes. "We found our targets by using the results of infrared surveys done with NASA's Spitzer Space Telescope and of surveys done with the National Science Foundation's (NSF) Very Large Array (VLA) radio telescope," Anderson said. "Objects that appear bright in both the Spitzer and VLA images we studied are good candidates for H II regions," he explained. The astronomers then used the NSF's giant Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, an extremely sensitive radio telescope. With the GBT, they were able to detect specific radio frequencies emitted by electrons as they recombined with protons to form hydrogen. This evidence of recombination confirmed that the regions contained ionized

  15. Mechanisms for quenching star formation activities in green valley galaxies and its depends on morphologies

    NASA Astrophysics Data System (ADS)

    Kong, Xu; Pan, Zhizheng; Lian, Jianhui

    2015-08-01

    Galaxies are categorized into two main populations, red quiescent galaxies and blue star-forming galaxies. One of the key questions is which physical mechanisms are responsible for quenching star formation activities in blue galaxies and the resulting transformation? In this talk, we present research on the morphologies, spectra, and environments of "green valley" galaxies in the COSMOS field and low redshift "green valley" galaxies in SDSS. Our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M* < 10^10.0 Msun blue galaxies into red galaxies, especially at z < 0.5. Using image from SDSS and GALEX, we analyze the radial ultraviolet-optical color distributions in a sample of low redshift green valley galaxies, and investigate how quenching is processing in a galaxy. The early-type "green valley" galaxies (ETGs) have dramatically different radial NUV-r color distributions compared to late-type "green valley" galaxies (LTGs), most of ETGs have blue cores, nearly all LTGs have uniform color profi