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Sample records for local galaxy properties

  1. Evolution of dwarf galaxy properties in local group environments

    NASA Astrophysics Data System (ADS)

    Arraki, Kenza Sigrid

    Understanding galaxy evolution depends on connecting large-scale structures determined by the ACDM model with, at minimum, the small-scale physics of gas, star formation, and stellar feedback. Formation of galaxies within dark matter halos is sensitive to the physical phenomena occurring within and around the halo. This is especially true for dwarf galaxies, which have smaller potential wells and are more susceptible to the effects of tidal stripping and gas ionization and removal than larger galaxies. At dwarf galaxies scales comparisons of dark matter-only simulations with observations has unveiled various differences such as the core-cusp, the missing satellites, and the too big to fail problems. We have run suites of collisionless and hydrodynamical simulations of dwarf galaxies evolution in massive host environments to address these issues. We performed controlled, numerical simulations, which mimic the effects of baryons, in order to examine the assumptions implicitly made by dark matter-only simulations. The too big to fail problem is due to the overabundance of relatively massive, dense satellite galaxies found in simulations of Milky Way-like environments. We found that the removal of a small baryonic component from the central regions of forming dwarf spheroidal galaxies and the inclusion of a disk component in the host galaxy can substantially reduce the central dark matter density of satellites, bringing simulations and observations of satellites into agreement. Additionally, we studied hydrodynamical simulations of massive host galaxies and their surrounding dwarf galaxy populations. The VELA simulation suite of cosmological zoom-in simulations is run with the ART code, stochastic star formation, and stellar feedback (supernovae feedback, stellar winds, radiation pressure, and photoionization pressure). The suite includes host galaxies with Mvir(z=0)=1011-10 12M ȯ and their satellite dwarf galaxies and local isolated dwarf galaxies around each primary

  2. 11HUGS & LVL: Star Formation Properties of Local Volume Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Janice C.; Gil de Paz, A.; Tremonti, C.; Kennicutt, R.; van Zee, L.; Sakai, S.; Funes, J. G.; LVL Team

    2007-12-01

    11HUGS, the 11 Mpc H-alpha UV Galaxy Survey, is a GALEX Legacy program designed to systematically characterize the star formation demographics of the Local Volume using a complete sample of 258 spiral and irregular galaxies within 11 Mpc. The dataset consists of snapshots of the instantaneous massive star formation as captured via narrowband H-alpha imaging, as well as GALEX NUV (1500 Å) and FUV (2300 Å) imaging, which traces star formation over a longer 1e8 yr timescale. UV observations of the 11HUGS sample are now 80% complete, and we use the available data, along with the completed H-alpha component of the survey, to investigate the consistency between UV and H-alpha derived star formation rates over a full range of activities down to ultra-low SFRs of 0.0001 M_sun/yr. We also provide a first look at the span of UV-FIR SED and dust properties using initial data from the follow-on Cycle 4 Spitzer Local Volume Legacy (LVL) survey, which is obtaining mid and far-IR imaging for the full sample.

  3. The properties of infrared galaxies in the local universe

    NASA Technical Reports Server (NTRS)

    Soifer, B. T.; Neugebauer, G.

    1991-01-01

    The 60-micron selected IRAS Bright Galaxy Sample is used as a starting point to derive additional complete flux-limited samples of extragalactic objects at 12, 25, and 100 microns. With these complete samples the luminosity functions at all IRAS wavelengths are derived for the local universe. These luminosity functions are used to determine the infrared emission of the local universe. The maximum in the energy output of galaxies occurs at 100 microns. The infrared emission of galaxies at 12 and 25 micron represents about 30 percent of the total infrared luminosity in the local universe. The mean infrared colors of infrared selected galaxies vary systematically with infrared luminosity; the ratio S sub nu (60 microns)/S sub nu(100 microns) increases and S sub nu(12 microns)/S sub nu(25 microns) decreases with increasing infrared luminosity.

  4. Spectral properties of galaxies in the Stromlo-APM redshift survey: clues on the local star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Tresse, L.; Maddox, S. J.; Loveday, J.

    We analyse emission-line properties of the bj-selected Stromlo-APM spectra ( = 0.05). Because this is a representative sample, we can study the global spectral properties of the local galaxy population. We classify spectra according to their H_alpha emission, which is closely related to massive star formation. This study gives a comparative local point for analysis of more distant surveys. We show that in the local universe, faint, small galaxies are dominated by star formation activity, while bright, large galaxies are more quiescent. Obviously this picture of the local universe is quite different from the distant one, where bright galaxies appear to show a rapidly-increasing activity back in time.

  5. The intriguing properties of local compact massive galaxies: What are they?

    NASA Astrophysics Data System (ADS)

    Ferré-Mateu, A.; Vazdekis, A.; Trujillo, I.; Sánchez-Blázquez, P.; Ricciardelli, E.; de la Rosa, I. G.

    2013-07-01

    Studying the properties of the few compact massive galaxies that exist in the local Universe (Trujillo et al. 2009) might provide a closer look to the nature of their high redshift (z >= 1.0) massive counterparts. By this means we have characterized their main kinematics, structural properties, stellar populations and star formation histories with a set of new high quality spectroscopic and imaging data (Ferré-Mateu et al. 2012 and Trujillo et al. 2012). These galaxies seem to be truly unique, as they do not follow the characteristic kinematics, stellar surface mass density profiles and stellar population patterns of present-day massive ellipticals or spirals of similar mass. They are, instead, more alike their high-z analogs. Summarizing, local compact massive galaxies are rare, unique and the perfect laboratory to study their high redshift counterparts.

  6. Local normal galaxies

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1990-01-01

    In the near future, high energy (E greater than 20 MeV) gamma ray astronomy offers the promise of a new means of examining the closest galaxies. Two and possibly three local galaxies, the Small and Large Magellanic Clouds and M31, should be visible to the high energy gamma ray telescope on the Gamma Ray Observatory, and the first should be seen by GAMMA-1. With the assumptions of adequate cosmic ray production and reasonable magnetic field strengths, both of which should likely be satisfied, specific predictions of the gamma ray emission can be made separating the concepts of the galactic and universal nature of cosmic rays. A study of the synchrotron radiation from the Large Magellanic Cloud (LMC) suggests that the cosmic ray density is similar to that in the local region of our galaxy, but not uniform. It is hoped the measurements will be able to verify this independent of assumptions about the magnetic fields in the LMC.

  7. 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.

  8. THE OBSERVED PROPERTIES OF DWARF GALAXIES IN AND AROUND THE LOCAL GROUP

    SciTech Connect

    McConnachie, Alan W.

    2012-07-15

    Positional, structural, and dynamical parameters for all dwarf galaxies in and around the Local Group are presented, and various aspects of our observational understanding of this volume-limited sample are discussed. Over 100 nearby galaxies that have distance estimates reliably placing them within 3 Mpc of the Sun are identified. This distance threshold samples dwarfs in a large range of environments, from the satellite systems of the MW and M31, to the quasi-isolated dwarfs in the outer regions of the Local Group, to the numerous isolated galaxies that are found in its surroundings. It extends to, but does not include, the galaxies associated with the next nearest groups, such as Maffei, Sculptor, and IC 342. Our basic knowledge of this important galactic subset and their resolved stellar populations will continue to improve dramatically over the coming years with existing and future observational capabilities, and they will continue to provide the most detailed information available on numerous aspects of dwarf galaxy formation and evolution. Basic observational parameters, such as distances, velocities, magnitudes, mean metallicities, as well as structural and dynamical characteristics, are collated, homogenized (as far as possible), and presented in tables that will be continually updated to provide a convenient and current online resource. As well as discussing the provenance of the tabulated values and possible uncertainties affecting their usage, the membership and spatial extent of the MW sub-group, M31 sub-group, and the Local Group are explored. The morphological diversity of the entire sample and notable sub-groups is discussed, and timescales are derived for the Local Group members in the context of their orbital/interaction histories. The scaling relations and mean stellar metallicity trends defined by the dwarfs are presented, and the origin of a possible 'floor' in central surface brightness (and, more speculatively, stellar mean metallicity) at

  9. DUST PROPERTIES OF LOCAL DUST-OBSCURED GALAXIES WITH THE SUBMILLIMETER ARRAY

    SciTech Connect

    Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J. E-mail: sandrews@cfa.harvard.edu

    2013-11-01

    We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S{sub ν}(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S{sub ν}(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 10{sup 11}(L{sub ☉}) and 4-14 × 10{sup 7}(M{sub ☉}), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.

  10. A comparison of the morphological properties between local and z ∼ 1 infrared luminous galaxies: Are local and high-z (U)LIRGs different?

    SciTech Connect

    Hung, Chao-Ling; Sanders, D. B.; Larson, Kirsten L.; Lee, Nicholas; Li, Yanxia; Lockhart, Kelly; Shih, Hsin-Yi; Barnes, Joshua E.; Casey, Caitlin M.; Koss, Michael; Kartaltepe, Jeyhan S.; Smith, Howard A.

    2014-08-10

    Ultraluminous and luminous infrared galaxies (ULIRGs and LIRGs) are the most extreme star-forming galaxies in the universe and dominate the total star formation rate density at z > 1. In the local universe (z < 0.3), the majority of ULIRGs and a significant portion of LIRGs are triggered by interactions between gas-rich spiral galaxies, yet it is unclear if this is still the case at high z. To investigate the relative importance of galaxy interactions in infrared luminous galaxies, we carry out a comparison of optical morphological properties between local (U)LIRGs and (U)LIRGs at z = 0.5-1.5 based on the same sample selection, morphology classification scheme, and optical morphology at similar rest-frame wavelengths. In addition, we quantify the systematics in comparing local and high-z data sets by constructing a redshifted data set from local (U)LIRGs, in which its data quality mimics the high-z data set. Based on the Gini-M{sub 20} classification scheme, we find that the fraction of interacting systems decreases by ∼8% from local to z ≲ 1, and it is consistent with the reduction between local and redshifted data sets (6{sub −6}{sup +14}%). Based on visual classifications, the merger fraction of local ULIRGs is found to be ∼20% lower compared to published results, and the reduction due to redshifting is 15{sub −8}{sup +10}%. Consequently, the differences of merger fractions between local and z ≲ 1 (U)LIRGs is only ∼17%. These results demonstrate that there is no strong evolution in the fraction of (U)LIRGs classified as mergers at least out to z ∼ 1. At z > 1, the morphology types of ∼30% of (U)LIRGs cannot be determined due to their faintness in the F814W band; thus, the merger fraction measured at z > 1 suffers from large uncertainties.

  11. Local Universe Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Carignan, Claude

    2015-08-01

    One of the outstanding problems in cosmology is addressing the "small-scale crisis" and understanding structure formation at the smallest scales. Standard Lambda Cold Dark Matter cosmological simulations of Milky Way-size DM halos predict many more DM sub-halos than the number of dwarf galaxies observed. This is the so-called Missing Satellites Problem. The most popular interpretation of the Missing Satellites Problem is that the smallest dark matter halos in the universe are extremely inefficient at forming stars. The virialized extent of the Milky Way's halo should contain ~500 satellites, while only ˜100 satellites and dwarfs are observed in the whole Local Group. Despite the large amount of theoretical work and new optical observations, the discrepancy, even if reduced, still persists between observations and hierarchical models, regardless of the model parameters. It may be possible to find those isolated ultra-faint missing dwarf galaxies via their neutral gas component, which is one of the goals we are pursuing with the SKA precursor KAT-7 in South Africa, and soon with the SKA pathfinder MeerKAT.

  12. HELGA: The Herschel Exploitation of the Local Galaxy Andromeda: Sub-mm Morphology and Dust Properties

    NASA Astrophysics Data System (ADS)

    Fritz, J.; Smith, M. W. L.; Kirk, J.; Helga Collaboration

    2014-03-01

    The results from a large-field Far-Infrared (FIR) and sub-millimeter (sub-mm) survey of our neighbor galaxy M31 are presented. We have obtained Herschel images of a ˜ 5.5 × 2.5 degree area centered on Andromeda. Using 21-cm atomic hydrogen maps, we are able to disentangle genuine emission from M31 from that for foreground Galactic cirrus, allowing us to recognize dusty structures out to ˜ 31 kpc from the center. We first characterize the FIR and sub-mm morphology and then, by de-projecting Herschel maps and running an ad-hoc source extraction algorithm, we reconstruct the intrinsic morphology and the spatial distribution of the molecular complexes. Finally, we study the spatially resolved properties of the dust (temperature, emissivity, mass, etc.) by means of a pixel-by-pixel SED fitting approach.

  13. WHERE ARE THE FOSSILS OF THE FIRST GALAXIES? I. LOCAL VOLUME MAPS AND PROPERTIES OF THE UNDETECTED DWARFS

    SciTech Connect

    Bovill, Mia S.; Ricotti, Massimo E-mail: ricotti@astro.umd.edu

    2011-11-01

    We present a new method for generating initial conditions for {Lambda}CDM N-body simulations which provides the dynamical range necessary to follow the evolution and distribution of the fossils of the first galaxies on Local Volume, 5-10 Mpc, scales. The initial distribution of particles represents the position, velocity, and mass distribution of the dark and luminous halos extracted from pre-reionization simulations. We confirm previous results that ultra-faint dwarfs have properties compatible with being well-preserved fossils of the first galaxies. However, because the brightest pre-reionization dwarfs form preferentially in biased regions, they most likely merge into non-fossil halos with circular velocities >20-30 km s{sup -1}. Hence, we find that the maximum luminosity of true fossils in the Milky Way is L{sub V} < 10{sup 6} L{sub sun}, casting doubts on the interpretation that some classical dSphs are true fossils. In addition, we argue that most ultra-faints at small galactocentric distance, R < 50 kpc, had their stellar properties modified by tides, while a large population of fossils is still undetected due to their extremely low surface brightness log ({Sigma}{sub V}) < -1.4. We estimate that the region outside R{sub 50} ({approx}400 kpc) up to 1 Mpc from the Milky Way contains about a hundred true fossils of the first galaxies with V-band luminosity 10{sup 3}-10{sup 5} L{sub sun} and half-light radii, r{sub hl} {approx} 100-1000 pc.

  14. Local analogs of high-redshift galaxies: Interstellar medium conditions

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    Local analog galaxies play an important role in understanding the properties of high-redshift galaxies. We present a method to select a type of local analog that closely resembles the ionized interstellar medium conditions in high-redshift galaxies. These galaxies are selected based on their locations in the [O III]/Hβ versus [N II]/Hα nebular emission-line diagnostic diagram. The ionization parameters and electron densities in these analogs are comparable to those in z ~= 2 - 3 galaxies, but higher than those in normal SDSS galaxies by ~= 0.6 dex and ~= 0.9 dex, respectively. We find that the high sSFR and SFR surface density can enhance the electron densities and the ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-redshift galaxies.

  15. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VI. The Distribution and Properties of Molecular Cloud Associations in M31

    NASA Astrophysics Data System (ADS)

    Kirk, J. M.; Gear, W. K.; Fritz, J.; Smith, M. W. L.; Ford, G.; Baes, M.; Bendo, G. J.; De Looze, I.; Eales, S. A.; Gentile, G.; Gomez, H. L.; Gordon, K.; O'Halloran, B.; Madden, S. C.; Roman-Duval, J.; Verstappen, J.; Viaene, S.; Boselli, A.; Cooray, A.; Lebouteiller, V.; Spinoglio, L.

    2015-01-01

    In this paper we present a catalog of giant molecular clouds (GMCs) in the Andromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy Andromeda (HELGA) data set. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterize the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al. A total of 326 GMCs in the mass range 104-107 M ⊙ are identified; their cumulative mass distribution is found to be proportional to M -2.34, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to L CO observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit, suggesting that we are observing associations of GMCs. Following Gordon et al., we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8.°9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  16. THE HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). VI. THE DISTRIBUTION AND PROPERTIES OF MOLECULAR CLOUD ASSOCIATIONS IN M31

    SciTech Connect

    Kirk, J. M.; Gear, W. K.; Smith, M. W. L.; Ford, G.; Eales, S. A.; Gomez, H. L.; Fritz, J.; Baes, M.; De Looze, I.; Gentile, G.; Gordon, K.; Verstappen, J.; Viaene, S.; Bendo, G. J.; O'Halloran, B.; Madden, S. C.; Lebouteiller, V.; Boselli, A.; Cooray, A.; and others

    2015-01-01

    In this paper we present a catalog of giant molecular clouds (GMCs) in the Andromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy Andromeda (HELGA) data set. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterize the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al. A total of 326 GMCs in the mass range 10{sup 4}-10{sup 7} M {sub ☉} are identified; their cumulative mass distribution is found to be proportional to M {sup –2.34}, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to L {sub CO} observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit, suggesting that we are observing associations of GMCs. Following Gordon et al., we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8.°9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system.

  17. Surface Photometry of Local Volume Galaxies

    NASA Astrophysics Data System (ADS)

    Sakai, Shoko; van Zee, Liese; Lee, Janice C.; Kennicutt, Robert C.; Funes, Jose G.

    2009-08-01

    We propose to obtain UBVR images of a statistically complete sample of spiral and irregular galaxies in the Local Volume Legacy (LVL) survey to investigate the correlation between past star formation activity and other physical properties such as SFR, dust content, and metallicity. The proposed optical imaging observations of 34 galaxies (27 southern, 7 northern) will be combined with existing UV, H(alpha), and IR observations, and will serve to nearly complete the optical imaging coverage of the full LVL sample of 258 galaxies. As expected for a volume limited sample, the majority of galaxies targeted here are low luminosity dwarf galaxies. The observed optical colors, in addition to optical-IR colors, will be compared with stellar population models to estimate the past history of star formation in these low mass galaxies and to provide constraints on the stellar mass-to-light ratios. The observed surface photometry will also allow us to study the photometric properties, the morphology, and spatial distributions of the different stellar populations in these low mass systems.

  18. Multi-wavelength properties and smbh's masses of the isolated galaxies with active nuclei in the Local Universe

    NASA Astrophysics Data System (ADS)

    Vavilova, Iryna; Vasylenko, Anatolij; Babyk, Iuri; Pulatova, Nadya

    2016-07-01

    We apply the specially-oriented Astro-Space databases obtained with ground-based telescopes and space observatories to study the multi-wavelength spectral and physical properties of galaxies with active nuclei (AGNs), namely of isolated AGNs that are poorly investigated especially in X-rays. Such a study allowed us 1) to separate the internal evolution mechanisms from the environment influence and consider them as two separate processes related to fueling nuclear activity, 2) to explore absorption features and the X-ray continuum radiation from accretion disks around SMBHs (e.g. to select accretion models). In the case of detecting the Fe K emission line, it was possible to analyze the physical conditions in the AGNs innermost parts in more details. Using the SDSS spectral Hβ-line data we were able to estimate the SMBH masses of several isolated AGNs in the Local Universe, which are systematically lower than the SMBH masses of AGNs located in a dense environment. We present also the results of analysis of the spectral data obtained by XMM-Newton, Swift, Chandra, and INTEGRAL space observatories for several isolated AGNs from 2MIG catalogue, for which the available X-ray data were accessed. Among these objects are CGCG 179-005, NGC 6300, NGC 1050, NGC 2989, WKK 3050, ESO 438-009, ESO 317-038 and others. We determined corresponding spectral models and values of their parameters (spectral index, intrinsic absorption etc.). X-ray spectra for bright galaxies, NGC 6300 and Circinus, were analyzed up to 250 keV and their characteristics of emission features were determined in 6-7 keV range.

  19. LOCAL TADPOLE GALAXIES: DYNAMICS AND METALLICITY

    SciTech Connect

    Sanchez Almeida, J.; Munoz-Tunon, C.; Mendez-Abreu, J.; Elmegreen, D. M.; Elmegreen, B. G. E-mail: cmt@iac.es E-mail: elmegreen@vassar.edu

    2013-04-10

    Tadpole galaxies, with a bright peripheral clump on a faint tail, are morphological types unusual in the nearby universe but very common early on. Low mass local tadpoles were identified and studied photometrically in a previous work, which we complete here analyzing their chemical and dynamical properties. We measure H{alpha} velocity curves of seven local tadpoles, representing 50% of the initial sample. Five of them show evidence for rotation ({approx}70%), and a sixth target hints at it. Often the center of rotation is spatially offset with respect to the tadpole head (three out of five cases). The size and velocity dispersion of the heads are typical of giant H II regions, and three of them yield dynamical masses in fair agreement with their stellar masses as inferred from photometry. In four cases the velocity dispersion at the head is reduced with respect to its immediate surroundings. The oxygen metallicity estimated from [N II] {lambda}6583/H{alpha} often shows significant spatial variations across the galaxies ({approx}0.5 dex), being smallest at the head and larger elsewhere. The resulting chemical abundance gradients are opposite to the ones observed in local spirals, but agrees with disk galaxies at high redshift. We interpret the metallicity variation as a sign of external gas accretion (cold-flows) onto the head of the tadpole. The galaxies are low-metallicity outliers of the mass-metallicity relationship. In particular, two of the tadpole heads are extremely metal poor, with a metallicity smaller than a tenth of the solar value. These two targets are also very young (ages smaller than 5 Myr). All these results combined are consistent with the local tadpole galaxies being disks in early stages of assembling, with their star formation sustained by accretion of external metal-poor gas.

  20. Morphological Peculiarities of Distant and Local Galaxies

    NASA Astrophysics Data System (ADS)

    Wu, K. L.; Faber, S. M.; Lauer, T. R.

    1997-12-01

    Detailed images from the Hubble Space Telescope (HST) have sparked a surge of interest in morphological peculiarities in both distant and local galaxies. Several groups have developed criteria by which to classify peculiarities in galaxy morphology (e.g., Abraham et al. 1996, Naim et al. 1997). In order to study peculiar galaxies at high redshifts, it is crucial to have a solid understanding of both the morphological peculiarities in local galaxies and the appearance of local galaxies if they were observed at higher redshifts. We are developing several algorithms to quantify the types and degree of peculiarity seen in galaxy morphology. These algorithms, or peculiarity indices, are sensitive to several different types of features. The indices are applied initially to two samples: (1) a local galaxy sample, comprised of a subset of the Frei, et al. 1996 ``Catalog of Nearby Galaxies,'' along with several merger candidates from Hibbard & van Gorkom 1996 and from a run on the Lick Observatory Nickel 40-inch telescope by one of the authors (KLW); and (2) a sample of simulated z ~ 0.8 galaxies. The images of the local galaxies are resampled, and noise is added, to reflect the sampling and noise levels found in the Hubble Deep Field (HDF). The galaxy sizes and surface brightnesses are cosmologically shifted to simulate observations of these galaxies through the HST F814W ( ~ I) filter at z ~ 0.8. This study expands upon previous work by providing a realistic view of which local morphological features we can expect to measure robustly when observed at high redshifts with the current observational technology. We also demonstrate the effectiveness of our peculiarity indices in differentiating between ``normal'' (i.e., Hubble Sequence type) galaxies and ``peculiar'' galaxies at these two epochs.

  1. VIPERS: Stellar population properties of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Siudek, Małgorzata; Malek, Katarzyna; Garilli, Bianka; Scodeggio, Marco; Fritz, Alexander; Pollo, Agnieszka

    2016-06-01

    We present stellar population properties of early-type galaxies from the VIMOS Public Extragalactic Redshift Survey (VIPERS) based on the spectral measurements of ˜ 4000 galaxies with stellar masses from 10^{10} to 10^{12} {[M_{⊙}]} in the redshift range 0.4 < z < 1.0. We quantify relations between their age, stellar metallicity, duration of star burst, and stellar mass. We compare the properties of VIPERS intermediate redshift galaxies with galaxies found in the Local Universe.

  2. Effect of bars on the galaxy properties

    NASA Astrophysics Data System (ADS)

    Vera, Matias; Alonso, Sol; Coldwell, Georgina

    2016-10-01

    Aims: With the aim of assessing the effects of bars on disk galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong bars, weak bars and without bars. Methods: We identified barred galaxies from the Sloan Digital Sky Survey (SDSS). By visual inspection of SDSS images we classified the face-on spiral galaxies brighter than g< 16.5 mag into strong-bar, weak-bar, and unbarred galaxies. With the goal of providing an appropriate quantification of the influence of bars on galaxy properties, we also constructed a suitable control sample of unbarred galaxies with similar redshifts, magnitudes, morphology, bulge sizes, and local density environment distributions to those of barred galaxies. Results: We found 522 strong-barred and 770 weak-barred galaxies; this represents a bar fraction of 25.82% with respect to the full sample of spiral galaxies, in good agreement with several previous studies. We also found that strong-barred galaxies show lower efficiency in star formation activity and older stellar populations (as derived with the Dn(4000) spectral index) with respect to weak-barred and unbarred spirals from the control sample. In addition, there is a significant excess of strong-barred galaxies with red colors. The color-color and color-magnitude diagrams show that unbarred and weak-barred galaxies are more extended towards the blue zone, while strong-barred disk objects are mostly grouped in the red region. Strong-barred galaxies present an important excess of high metallicity values compared to unbarred and weak-barred disk objects, which show similar distributions. Regarding the mass-metallicity relation, we found that weak-barred and unbarred galaxies are fitted by similar curves, while strong-barred ones show a curve that falls abruptly with more significance in the range of low stellar masses (log (M∗/M⊙) < 10.0). These results would indicate that prominent bars produced an accelerating effect on the gas processing

  3. Segregation properties of galaxies

    SciTech Connect

    Santiago, B.X.; Da Costa, L.N. )

    1990-10-01

    Using the recently completed Southern Sky Redshift Survey, in conjunction with measurements of the central surface brightness, the existence of segregation in the way galaxies of different morphology and surface brightness are distributed in space is investigated. Results indicate that there is some evidence that low surface brightness galaxies are more randomly distributed than brighter ones and that this effect is independent of the well-known tendency of early-type galaxies to cluster more strongly than spirals. Presuming that the observed clustering was established at the epoch of galaxy formation, it may provide circumstantial evidence for biased galaxy formation. 24 refs.

  4. Interpreting the Properties of Galaxies

    NASA Astrophysics Data System (ADS)

    Conti, Alberto

    Galaxies exhibit a wide range of physical properties (e.g., luminosities, colors, velocity widths, star formation, gas and stellar content) and the evolutionary processes responsible for these properties are numerous and complex. Understanding which processes shape the observable properties of galaxies and which others play only a minor role, inherently requires a large sample of galaxies. Moreover, if we want to understand why galaxies have the properties they do, we need a theory of galaxy formation. The standard paradigm of galaxy formation assumes that most of the matter is dark and dissipationless and that, under the influence of gravity, structures on galactic and larger scales grow hierarchically (from Gaussian initial conditions) with smaller objects forming first. Gas, moving under the gravitational influence of the dark component, dissipates and collapses at the center of the potential wells provided by the dark matter. In this picture the internal structure of the dark matter clumps and their formation history regulate the global properties of galaxies. However, these properties must also depend on how gas cools to form the dense clouds that seed star formation and how star formation affects the surrounding medium with the injection of energy and heavy elements. I show how simple, ``semi-analytic'' parameterizations are used to describe the highly non-linear aforementioned processes and to predict a wide range of properties of the galaxy population for any specific cosmogony. I then present a simple and flexible framework to extract from the numerous observable properties of disk galaxies that semi-analytic models predict, only those that are needed to characterize the sample as a whole. This framework makes use of the well-know statistical technique of Principal Component Analysis (PCA). Moreover, I correlate the semi-analytic assumptions with the PCA findings and determine which, among our theoretical assumptions, shape the observable galaxies

  5. An infrared imaging study of galaxies in the local universe

    NASA Technical Reports Server (NTRS)

    Grauer, Albert D.; Rieke, Marcia J.; Mcleod, Kim K.

    1995-01-01

    This poster was a preliminary report on a survey of galaxies in the local universe at J and K using a NICMOS3 256 x 256 infrared photometric camera attached to the 61 inch telescope on Mt. Bigelow. Deep images are being obtained for a representative sample of galaxies in the Uppsala General Catalogue. Structural and color parameters are determined for a wide variety of galactic types. These data should prove to be valuable in characterizing stellar populations within disks and bulges, determining if IR-active galaxies have unusual global as well as- nuclear properties, and understanding the effects of evolution and redshift dimming in distant galaxies.

  6. Dust and star formation properties of a complete sample of local galaxies drawn from the Planck Early Release Compact Source Catalogue

    NASA Astrophysics Data System (ADS)

    Clemens, M. S.; Negrello, M.; De Zotti, G.; Gonzalez-Nuevo, J.; Bonavera, L.; Cosco, G.; Guarese, G.; Boaretto, L.; Salucci, P.; Baccigalupi, C.; Clements, D. L.; Danese, L.; Lapi, A.; Mandolesi, N.; Partridge, R. B.; Perrotta, F.; Serjeant, S.; Scott, D.; Toffolatti, L.

    2013-07-01

    We combine Planck High Frequency Instrument data at 857, 545, 353 and 217 GHz with data from Wide-field Infrared Survey Explorer (WISE), Spitzer, IRAS and Herschel to investigate the properties of a well-defined, flux-limited sample of local star-forming galaxies. A 545 GHz flux density limit was chosen so that the sample is 80 per cent complete at this frequency, and the resulting sample contains a total of 234 local, star-forming galaxies. We investigate the dust emission and star formation properties of the sample via various models and calculate the local dust mass function. Although single-component-modified blackbodies fit the dust emission longward of 80 μm very well, with a median β = 1.83, the known degeneracy between dust temperature and β also means that the spectral energy distributions are very well described by a dust component with dust emissivity index fixed at β = 2 and temperature in the range 10-25 K. Although a second, warmer dust component is required to fit shorter wavelength data, and contributes approximately a third of the total infrared emission, its mass is negligible. No evidence is found for a very cold (6-10 K) dust component. The temperature of the cold dust component is strongly influenced by the ratio of the star formation rate to the total dust mass. This implies, contrary to what is often assumed, that a significant fraction of even the emission from ˜20 K dust is powered by ongoing star formation, whether or not the dust itself is associated with star-forming clouds or `cirrus'. There is statistical evidence of a free-free contribution to the 217 GHz flux densities of ≲20 per cent. We find a median dust-to-stellar mass ratio of 0.0046; and that this ratio is anticorrelated with galaxy mass. There is good correlation between dust mass and atomic gas mass (median Md/MHI = 0.022), suggesting that galaxies that have more dust (higher values of Md/M*) have more interstellar medium in general. Our derived dust mass function

  7. 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)

  8. Local Group Galaxy Emission-line Survey

    NASA Astrophysics Data System (ADS)

    Blaha, Cindy; Baildon, Taylor; Mehta, Shail; Garcia, Edgar; Massey, Philip; Hodge, Paul W.

    2015-01-01

    We present the results of the Local Group Galaxy Emission-line Survey of Hα emission regions in M31, M33 and seven dwarf galaxies in (NGC6822, IC10, WLM, Sextans A and B, Phoenix and Pegasus). Using data from the Local Group Galaxy Survey (LGGS - see Massey et al, 2006), we used continuum-subtracted Ha emission line images to define emission regions with a faint flux limit of 10 -17 ergs-sec-1-cm-2above the background. We have obtained photometric measurements for roughly 7450 Hα emission regions in M31, M33 and five of the seven dwarf galaxies (no regions for Phoenix or Pegasus). Using these regions, with boundaries defined by Hα-emission flux limits, we also measured fluxes for the continuum-subtracted [OIII] and [SII] images and constructed a catalog of Hα fluxes, region sizes and [OIII]/ Hα and [SII]/ Hα line ratios. The HII region luminosity functions and size distributions for the spiral galaxies M31 and M33 are compared with those of the dwarf galaxies NGC 6822 and IC10. For M31 and M33, the average [SII]/ Hα and [OIII]/ Hα line ratios, plotted as a function of galactocentric radius, display a linear trend with shallow slopes consistent with other studies of metallicity gradients in these galaxies. The galaxy-wide averages of [SII]/ Hα line ratios correlate with the masses of the dwarf galaxies following the previously established dwarf galaxy mass-metallicity relationship. The slope of the luminosity functions for the dwarf galaxies varies with galaxy mass. The Carleton Catalog of this Local Group Emission-line Survey will be made available on-line.

  9. Reddening and Absorption Through Local Group Galaxies

    NASA Astrophysics Data System (ADS)

    Hodge, Paul

    1997-07-01

    This project involves a photometric study of galaxies seen through the bodies of several Local Group galaxies. The high resolution of WFPC2 images will be used with automated techniques to identify galaxies at various magnitude limits. For three different magnitude regimes we will use three different techniques for studying the optical effects of the dust content: 1} for the brighter galaxies the integrated colors will be determined and compared to those of similar Hubble types in the field, which follow a fairly narrow color- type relationship; 2} for a selection of galaxies that goes to somewhat fainter limits, we will be able to measure magnitudes in three colors, allowing us to determine reddening by comparison with the field galaxy color-color relations; and 3} the identified galaxies of all brightnesses will be counted, using automated techniques, and the counts will be compared to galaxy densities in the field. The goal is a map of the TOTAL extinction and reddening through the Local Group galaxies, which can be compared to maps of the HI, molecular gas and infrared radiation, so that astrophysical conclusions can be made.

  10. SUPERDENSE MASSIVE GALAXIES IN WINGS LOCAL CLUSTERS

    SciTech Connect

    Valentinuzzi, T.; D'Onofrio, M.; Fritz, J.; Poggianti, B. M.; Bettoni, D.; Fasano, G.; Moretti, A.; Omizzolo, A.; Varela, J.; Cava, A.; Couch, W. J.; Dressler, A.; Moles, M.; Kjaergaard, P.; Vanzella, E.

    2010-03-20

    Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high- to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 < z < 0.07. We discover a significant population of superdense massive galaxies with masses and sizes comparable to those observed at high redshift. They approximately represent 22% of all cluster galaxies more massive than 3 x 10{sup 10} M{sub sun}, are mostly S0 galaxies, have a median effective radius (R{sub e} ) = 1.61 +- 0.29 kpc, a median Sersic index (n) = 3.0 +- 0.6, and very old stellar populations with a median mass-weighted age of 12.1 +- 1.3 Gyr. We calculate a number density of 2.9 x 10{sup -2} Mpc{sup -3} for superdense galaxies in local clusters, and a hard lower limit of 1.3 x 10{sup -5} Mpc{sup -3} in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius, and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that-when stellar masses are considered-there is consistency with the local WINGS galaxy sizes out to z {approx} 2, while a discrepancy of a factor of 3 exists with the only spectroscopic z > 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M{sub *} > 4 x 10{sup 11} M{sub sun} compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.

  11. The Far-Infrared Properties of the Most Isolated Galaxies

    NASA Astrophysics Data System (ADS)

    Lisenfeld, U.; Verdes-Montenegro, L.; Sulentic, J.; Leon, S.; Espada, D.; Bergond, G.; García, E.; Sabater, J.; Santander-Vela, J. D.; Verley, S.

    2007-05-01

    A long-standing question in galaxy evolution involves the role of nature (self-regulation) vs. nurture (environment) on the observed properties (and evolution) of galaxies. A collaboration centreed at the Instituto de Astrofisica de Andalucia (Granada, Spain) is trying to address this question by producing a observational database for a sample of 1050 isolated galaxies from the catalogue of Karachentseva (1973) with the overarching goal being the generation of a "zero-point" sample against which effects of environment on galaxies can be assessed. The AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) database (see www.iaa.es/AMIGA.html) will include optical, IR and radio line and continuum measures. The galaxies in the sample represent the most isolated galaxies in the local universe. In the present contribution, we will present the project, as well as the results of an analysis of the far-infrared (FIR) and molecular gas properties of this sample.

  12. Chemical abundances of massive stars in Local Group galaxies

    NASA Astrophysics Data System (ADS)

    Venn, Kim A.; Kaufer, Andreas; Tolstoy, Eline; Kudritzki, Rolf-Peter; Przybilla, Norbert; Smartt, Stephen J.; Lennon, Daniel J.

    The relative abundances of elements in galaxies can provide valuable information on the stellar and chemical evolution of a galaxy. While nebulae can provide abundances for a variety of light elements, stars are the only way to directly determine the abundances of iron-group and s-process and r-process elements in a galaxy. The new 8m and 10m class telescopes and high-efficiency spectrographs now make high-quality spectral observations of bright supergiants possible in dwarf galaxies in the Local Group. We have been concentrating on elemental abundances in the metal-poor dwarf irregular galaxies, NGC 6822, WLM, Sextants A, and GR 8. Comparing abundance ratios to those predicted from their star formation histories, determined from color-magnitude diagrams, and comparing those ratios between these galaxies can give us new insights into the evolution of these dwarf irregular galaxies. Iron-group abundances also allow us to examine the metallicities of the stars in these galaxies directly, which affects their inferred mass loss rates and predicted stellar evolution properties.

  13. Dynamics of galaxy structures in the Local Volume

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.

    2016-10-01

    I consider a sample of `Updated Nearby Galaxy Catalog' that contains eight hundred objects within 11 Mpc. Environment of each galaxy is characterized by a tidal index Θ1 depending on separation and mass of the galaxy Main Disturber (=MD). The UNGC galaxies with a common MD are ascribed to its `suite' and ranked according to their Θ1. Fifteen the most populated suites contain more than half of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at M_B = -18 mag. The observational properties of galaxies accumulated in UNGC are used to derive orbital masses of giant galaxies via motions of their satellites. The average orbital-to-stellar mass ratio for them is M orb M* ~= 30, corresponding to the mean local density of matter Ωm ~= 0.09, i.e 1/3 of the global cosmic one. The dark-to-stellar mass ratio for the Milky Way and M31 is typical for other neighboring giant galaxies.

  14. Characterizing Dust Attenuation in Local Star Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Battisti, Andrew; Calzetti, Daniela; Chary, Ranga-Ram

    2017-01-01

    The dust attenuation for a sample of ~10000 local (z ≤ 0.1) star forming galaxies is constrained as a function of their physical properties. We utilize aperture-matched multi-wavelength data from the UV-to-NIR, available from the Galaxy Evolution Explorer, the Sloan Digital Sky Survey, the United Kingdom Infrared Telescope, and the Two Micron All-Sky Survey, to ensure that regions of comparable size in each galaxy are being analyzed. We characterize the dust attenuation through the slope of the UV flux density and the Balmer decrement (Hα/Hβ). The observed relationship between these quantities is similar to the local starburst relation and is not seen to vary strongly with galactic properties. We derive the total attenuation curve over the range 1250 Å < λ < 28500 Å and find that a single attenuation curve is effective for characterizing the majority of galaxies in our sample. This attenuation curve is slightly lower in the far-UV than local starburst galaxies, by roughly 15%, but appears similar at longer wavelengths and has a normalization of RV = 3.7±0.4 (V-band). This indicates that a single attenuation curve is reasonable for wide application in the local Universe.

  15. The [L - s] calibration for local HII galaxies

    NASA Astrophysics Data System (ADS)

    Bordalo, V.; Telles, E.

    2003-08-01

    The physical conditions found in HII galaxies has profound implications on several topics, such as star formation and its possible sequential propagation in HII galaxies, and how the ISM is structured in these galaxies. Central in this field of research is the validity and interpretation of the empirical correlations of size and luminosity versus their supersonic line widths for high redshift galaxies. A fine calibration of these relations for local HII galaxies may be of great importance if used as a distance indicator of galaxies at high redshift, since HII galaxies are easy to find at great distances. In a recent paper (Telles, Muñoz-Tuñón & Tenorio-Tagle, 2001) was shown that: (i) enhanced spectral and spatial resolution seems to unveil an intricate structure in HII galaxies. (ii) HII galaxies when resolved, present several emitting knots with a variety of shapes, luminosity and sigma values. (iii) The intrinsic properties (luminosity, velocity dispersion) of a galaxy are dominated by the central(core) component. These results were the motivations to observe HII galaxies using FEROS spectrograph(ESO) which has high resolution(R = 48000) and high efficiency. Here we present our most recent calibration of the [L-s] relation from a homogeneous sample of about one hundred local HII galaxies, using line widths measures from FEROS data. The integrated flux for Ha, Hb and [OIII](ll 4959, 5007), O/H ratio and equivalent widths were obtained from a spectrophotometric catalog of HII galaxies built from Boller & Chivens(ESO) data(Telles, Cuisinier & Kehrig in preparation). We are also studying the behavior of the relation for different emission lines and investigating the existence of a second parameter, such as metallicity and equivalent width. These new calibrations show a significant improvement in the accuracy in which distances can be derived due to the high quality of our data. We'll show that our calibration is consistent with previous works, confirming the

  16. The atomic-to-molecular transition and its relation to the scaling properties of galaxy discs in the local Universe

    NASA Astrophysics Data System (ADS)

    Fu, Jian; Guo, Qi; Kauffmann, Guinevere; Krumholz, Mark R.

    2010-12-01

    We extend the existing semi-analytic models of galaxy formation to track atomic and molecular gas in disc galaxies. Simple recipes for processes such as cooling, star formation, supernova feedback and chemical enrichment of the stars and gas are grafted on to dark matter halo merger trees derived from the Millennium Simulation. Each galactic disc is represented by a series of concentric rings. We assume that the surface density profile of an infalling gas in a dark matter halo is exponential, with scale radius rd that is proportional to the virial radius of the halo times its spin parameter λ. As the dark matter haloes grow through mergers and accretion, disc galaxies assemble from the inside out. We include two simple prescriptions for molecular gas formation processes in our models: one is based on the analytic calculations by Krumholz, McKee & Tumlinson, and the other is a prescription where the H2 fraction is determined by the pressure of the interstellar medium (ISM). Motivated by the observational results of Leroy et al., we adopt a star formation law in which in the regime where the molecular gas dominates the total gas surface density, and where atomic hydrogen dominates. We then fit these models to the radial surface density profiles of stars, HI and H2 drawn from recent high-resolution surveys of stars and gas in nearby galaxies. We explore how the ratios of atomic gas, molecular gas and stellar mass vary as a function of global galaxy scale parameters, including stellar mass, stellar surface density and gas surface density. We elucidate how the trends can be understood in terms of three variables that determine the partition of baryons in discs: the mass of the dark matter halo, the spin parameter of the halo and the amount of gas recently accreted from the external environment.

  17. Local Analogs for High-redshift Galaxies: Resembling the Physical Conditions of the Interstellar Medium in High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    We present a sample of local analogs for high-redshift galaxies selected in the Sloan Digital Sky Survey (SDSS). The physical conditions of the interstellar medium (ISM) in these local analogs resemble those in high-redshift galaxies. These galaxies are selected based on their positions in the [O iii]/Hβ versus [N ii]/Hα nebular emission-line diagnostic diagram. We show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (sSFRs), flat UV continuums, and compact galaxy sizes. In particular, the ionization parameters and electron densities in these analogs are comparable to those in z ≃ 2-3 galaxies, but higher than those in normal SDSS galaxies by ≃0.6 dex and ≃0.9 dex, respectively. The mass-metallicity relation (MZR) in these local analogs shows -0.2 dex offset from that in SDSS star-forming galaxies at the low-mass end, which is consistent with the MZR of the z˜ 2{--}3 galaxies. We compare the local analogs in this study with those in other studies, including Lyman break analogs (LBA) and green pea (GP) galaxies. The analogs in this study share a similar star formation surface density with LBAs, but the ionization parameters and electron density in our analogs are higher than those in LBAs by factors of 1.5 and 3, respectively. The analogs in this study have comparable ionization parameters and electron densities to the GP galaxies, but our method can select galaxies in a wider redshift range. We find the high sSFR and SFR surface density can increase the electron density and ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-redshift galaxies.

  18. Supermassive black holes in local galaxies

    NASA Astrophysics Data System (ADS)

    Bender, Ralf; Saglia, Roberto P.

    2007-01-01

    Over the past decade we have learned that probably all ellipticals and bulges of galaxies contain central supermassive black holes (SMBH). SMBH masses correlate well with the luminosities, and in turn the stellar masses of the bulges harboring them, with about 0.15% of the bulge mass being found in the SMBH. Pure disk galaxies, on the other hand, do not, in general, seem to contain SMBHs. Here we review the best cases for SMBH detection in galaxies, discuss methods and associated uncertainties, summarize correlations between SMBH masses and host galaxy properties, and finally address possible future developments. To cite this article: R. Bender, R.P. Saglia, C. R. Physique 8 (2007).

  19. Fitting the SEDs of Galaxies in the Local Volume

    NASA Astrophysics Data System (ADS)

    Johnson, B. D.

    2011-06-01

    The distribution of the Hα/UV flux ratio in local, low-luminosity galaxies is suggestive of a varying high-mass end of the Initial Mass Function (IMF), though several additional effects may be responsible. I describe the fitting of population synthesis models with an invariant IMF to the Spectral Energy Distributions of a subset of the Local Volume Legacy (LVL) sample. I pay special attention to the types of star formation histories and dust properties required to match simultaneously the UV and Hα fluxes of these low luminosity galaxies, under the assumption that the IMF does not vary. The observed SEDs to be fit include UV, optical, and IR broadband photometry from GALEX, SDSS, and Spitzer respectively, as well as narrowband Hα photometry from the 11Mpc Survey. Of special importance is the observed thermal Far-IR emission, which places a useful constraint on the dust attenuation. I find that recently ended bursts adequately describe the UV through Far-IR SED of ≲10% of the sample, while the rest, including some galaxies with 'low' Hα/UV flux ratios, are well fit by a smooth or continuous recent star formation history. I consider the physical properties of local volume galaxies, derived from indicators that are not sensitive to the upper IMF, and find the suggestion of a large spread in specific star formation rate at low stellar mass, possibly indicating a range of long-term star formation history in these galaxies.

  20. 'Direct' Gas-Phase Metallicities, Stellar Properties, and Local Environments of Emission-Line Galaxies at Redshifts Below 0.90

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Malkan, Matthew A.; Nagao, Tohru; Kashikawa, Nobunari; Shimasaku, Kazuhiro; Hayashi, Masao

    2013-01-01

    Using deep narrow-band (NB) imaging and optical spectroscopy from the Keck telescope and the Multi Mirror Telescope (MMT), we identify a sample of 20 emission-line galaxies (ELGs) at z = 0.065-0.90 where the weak auroral emission line, [O iii] lambda4363, is detected at >=3sigma. These detections allow us to determine the gas-phase metallicity using the "direct" method. With electron temperature measurements, and dust attenuation corrections from Balmer decrements, we find that 4 of these low-mass galaxies are extremely metal-poor with 12+log(O/H) <= 7.65 or one-tenth solar. Our most metal-deficient galaxy has 12+log(O/H)= 7.24(+0.45 / -0.30) (95% confidence), similar to some of the lowest metallicity galaxies identified in the local universe. We find that our galaxies are all undergoing significant star formation with average specific star formation rate (SFR) of (100 Myra)(exp -1), and that they have high central SFR surface densities (average of 0.5 Solar M / yr/ sq. kpc). In addition, more than two-thirds of our galaxies have between one and four nearby companions within a projected radius of 100 kpc, which we find is an excess among star-forming galaxies at z =0.4 -- 0.85. We also find that the gas-phase metallicities for a given stellar mass and SFR lie systematically lower than the local stellar M-Z-(SFR) relation by approx. = 0.2 dex (2 sigma significance). These results are partly due to selection effects, since galaxies with strong star formation and low metallicity are more likely to yield [O iii] lambda4363 detections. Finally, the observed higher ionization parameter and high electron density suggest that they are lower redshift analogs to typical z approx. > 1 galaxies.

  1. Stellar halos around Local Group galaxies

    NASA Astrophysics Data System (ADS)

    McConnachie, Alan W.

    2016-08-01

    The Local Group is now home to 102 known galaxies and candidates, with many new faint galaxies continuing to be discovered. The total stellar mass range spanned by this population covers a factor of close to a billion, from the faintest systems with stellar masses of order a few thousand to the Milky Way and Andromeda, with stellar masses of order 1011 M ⊙. Here, I discuss the evidence for stellar halos surrounding Local Group galaxies spanning from dwarf scales (with the case of the Andromeda II dwarf spheroidal), though to intermediate mass systems (M33) and finishing with M31. Evidence of extended stellar populations and merging is seen across the luminosity function, indicating that the processes that lead to halo formation are common at all mass scales.

  2. Radio properties of fossil galaxy groups

    NASA Astrophysics Data System (ADS)

    Miraghaei, H.; Khosroshahi, H. G.

    2016-09-01

    We study 1.4 GHz radio properties of a sample of fossil galaxy groups using GMRT radio observations and the FIRST survey catalog. Fossil galaxy groups, having no recent major mergers in their dominant galaxies and also group scale mergers, give us the opportunity to investigate the effect of galaxy merger on AGN activity. In this work, we compare the radio properties of a rich sample of fossil groups with a sample of normal galaxy groups and clusters and show that the brightest group galaxies in fossil groups are under luminous at 1.4 GHz, relative to the general population of the brightest group galaxies, indicating that the dynamically relaxed nature of fossil groups has influenced the AGN activity in their dominant galaxy.

  3. General properties of HII regions in galaxies

    NASA Technical Reports Server (NTRS)

    Smirnov, M. A.; Komberg, B. V.

    1979-01-01

    The structure, electron density, and dimensions of HII regions in galaxies are discussed. These parameters are correlated to the chemical composition gradient along the galactic radius, the dimensions of the three largest HII regions in the galaxy, and the amount of hydrogen in the galaxy, as well as the mass, dimensions, and total optical luminosity of the galaxy. The relationships of HII regions to star formation and galactic nucleus activity are discussed and the kinematic properties of the SB and Sab galaxies are related to the size of HII regions.

  4. AGN Host Galaxy Properties And Mass Function

    NASA Astrophysics Data System (ADS)

    Bongiorno, Angela

    2016-10-01

    Supermassive black hole growth, nuclear activity, and galaxy evolution have been found to be closely related. In the context of AGN-galaxy coevolution, I will discuss about the relation found between the host galaxy properties and the central BH and I will present the latest determination of the host galaxy stellar mass function (HGMF), and the specific accretion rate distribution function (SARDF), derived from the XMM-COSMOS sample up to z˜2.5, with particular focus on AGN feedback as possible responsible mechanism for galaxy quenching.

  5. Properties of Bars in the Local Universe

    NASA Astrophysics Data System (ADS)

    Nair, Preethi

    2009-12-01

    Early work on bar fractions suffered from poor sample sizes which limited the study of correlations between bar fraction and physical properties. Recent large surveys like SDSS and COSMOS have helped rectify this deficiency. Sheth et al. (2008) using a sample of 2000 galaxies from COSMOS, have shown that bar fractions decrease with redshift as claimed by Abraham et al. (1999) and van den Bergh et al. (2000) . In addition, they find the bar fraction of spiral galaxies is a strong function of stellar mass, color and bulge prominence such that more massive, redder, concentrated galaxies have a larger bar fraction than less massive, bluer, diskier galaxies. Barazza et al. (2008) using 2000 galaxies from SDSS find results counter to Sheth et al. (2008) i.e., bar fractions increase with decreasing mass and bluer colors (corresponding to late type galaxies). Using a larger sample of 15000 visually classified SDSS galaxies (which includes bar classifications) I further investigate the properties of barred galaxies in the local universe. In addition, I will describe the variation of total fine fraction (bars + rings +lenses) with physical properties and the effects of AGN on the observed fine fraction.

  6. Galaxy interactions and active galactic nuclei in the local universe

    NASA Astrophysics Data System (ADS)

    Ryan, Christopher J.

    2009-06-01

    It has been suggested that galaxy interactions may be the principal mechanism responsible for triggering non-thermal activity in galactic nuclei. This thesis investigates the possible role of interactions in the local Universe by searching for evidence of a causal relationship between major interactions and the initiation of activity in Seyfert galaxies using high-quality, multiwavelength imaging data. The connection between interacting galaxies and Seyferts is explored by comparing the clustering properties of their environments, as quantified by the spatial cross-correlation function amplitude. If a direct evolutionary relationship exists, the objects should be located in environments that are statistically similar. It was previously demonstrated that Seyferts are found in fields comparable to isolated galaxies. The analysis presented in this work reveals that interacting galaxies are preferentially situated in regions consistent with Abell Richness Classes of 0 to 1. The apparent dissimilarity of their environments provides a strong argument against a link between major interactions and Seyfert galaxies. An examination of the photometric and morphological properties of the interacting systems does not uncover any trends that could be associated with the initiation of nuclear activity. The role of major interactions in triggering low-redshift AGNs is then assessed using near-infrared imagery of a sample of Narrow-Line Seyfert 1 galaxies. It has been postulated that these objects are evolutionarily young AGNs, powered by accretion onto supermassive black holes that are considerably lower in mass than those found in typical broad-line Seyferts. By employing the correlation between black hole mass and host galaxy bulge luminosity, the mean black hole mass, [Special characters omitted.] BH , in solar units for the sample is found to be [left angle bracket]log [Special characters omitted.] ( BH )[right angle bracket] = 7.7 ± 0.1, consistent with typical broad

  7. Dust-obscured galaxies in the local universe

    SciTech Connect

    Hwang, Ho Seong; Geller, Margaret J. E-mail: mgeller@cfa.harvard.edu

    2013-06-01

    We use Wide-field Infrared Survey Explorer (WISE), AKARI, and Galaxy Evolution Explorer (GALEX) data to select local analogs of high-redshift (z ∼ 2) dust obscured galaxies (DOGs). We identify 47 local DOGs with S {sub 12μm}/S {sub 0.22μm} ≥ 892 and S {sub 12μm} > 20 mJy at 0.05 < z < 0.08 in the Sloan Digital Sky Survey data release 7. The infrared (IR) luminosities of these DOGs are in the range 3.4 × 10{sup 10} (L {sub ☉}) ≲ L {sub IR} ≲ 7.0 × 10{sup 11} (L {sub ☉}) with a median L {sub IR} of 2.1 × 10{sup 11} (L {sub ☉}). We compare the physical properties of local DOGs with a control sample of galaxies that have lower S {sub 12μm}/S {sub 0.22μm} but have similar redshift, IR luminosity, and stellar mass distributions. Both WISE 12 μm and GALEX near-ultraviolet (NUV) flux densities of DOGs differ from the control sample of galaxies, but the difference is much larger in the NUV. Among the 47 DOGs, 36% ± 7% have small axis ratios in the optical (i.e., b/a < 0.6), larger than the fraction among the control sample (17% ± 3%). There is no obvious sign of interaction for many local DOGs. No local DOGs have companions with comparable optical magnitudes closer than ∼50 kpc. The large- and small-scale environments of DOGs are similar to the control sample. Many physical properties of local DOGs are similar to those of high-z DOGs, even though the IR luminosities of local objects are an order of magnitude lower than for the high-z objects: the presence of two classes (active galactic nuclei- and star formation-dominated) of DOGs, abnormal faintness in the UV rather than extreme brightness in the mid-IR, and diverse optical morphology. These results suggest a common underlying physical origin of local and high-z DOGs. Both seem to represent the high-end tail of the dust obscuration distribution resulting from various physical mechanisms rather than a unique phase of galaxy evolution.

  8. DEPENDENCE OF BARRED GALAXY FRACTION ON GALAXY PROPERTIES AND ENVIRONMENT

    SciTech Connect

    Lee, Gwang-Ho; Lee, Myung Gyoon; Park, Changbom; Choi, Yun-Young E-mail: mglee@astro.snu.ac.kr E-mail: yy.choi@khu.ac.kr

    2012-02-01

    We investigate the dependence of the occurrence of bars in galaxies on galaxy properties and environment. We use a volume-limited sample of 33,391 galaxies brighter than M{sub r} = -19.5 + 5logh at 0.02 {<=} z {<=} 0.05489, drawn from the Sloan Digital Sky Survey Data Release 7. We classify the galaxies into early and late types, and identify bars by visual inspection. Among 10,674 late-type galaxies with axis ratio b/a > 0.60, we find 3240 barred galaxies (f{sub bar} = 30.4%) which divide into 2542 strong bars (f{sub SB1} = 23.8%) and 698 weak bars (f{sub SB2} = 6.5%). We find that f{sub SB1} increases as u - r color becomes redder and that it has a maximum value at intermediate velocity dispersion ({sigma} {approx_equal}150 km s{sup -1}). This trend suggests that strong bars are dominantly hosted by intermediate-mass systems. Weak bars prefer bluer galaxies with lower mass and lower concentration. In the case of strong bars, their dependence on the concentration index appears only for massive galaxies with {sigma} > 150 km s{sup -1}. We also find that f{sub bar} does not directly depend on the large-scale background density when other physical parameters (u - r color or {sigma}) are fixed. We discover that f{sub SB1} decreases as the separation to the nearest neighbor galaxy becomes smaller than 0.1 times the virial radius of the neighbor regardless of neighbor's morphology. These results imply that strong bars are likely to be destroyed during strong tidal interactions and that the mechanism for this phenomenon is gravitational and not hydrodynamical. The fraction of weak bars has no correlation with environmental parameters. We do not find any direct evidence for environmental stimulation of bar formation.

  9. Properties of Galaxies and Groups: Nature versus Nurture

    NASA Astrophysics Data System (ADS)

    Niemi, Sami-Matias

    2011-09-01

    Due to the inherently nonlinear nature of gravity cosmological N-body simulations have become an invaluable tool when the growth of structure is being studied and modelled closer to the present epoch. Large simulations with high dynamical range have made it possible to model the formation and growth of cosmic structure with unprecedented accuracy. Moreover, galaxies, the basic building blocks of the Universe, can also be modelled in cosmological context. However, despite all the simulations and successes in recent decades, there are still many unanswered questions in the field of galaxy formation and evolution. One of the longest standing issue being the significance of the formation place and thus initial conditions to a galaxy's evolution in respect to environment, often formulated simply as "nature versus nurture" like in human development and psychology. Unfortunately, our understanding of galaxy evolution in different environments is still limited, albeit, for example, the morphology-density relation has shown that the density of the galaxy's local environment can affect its properties. Consequently, the environment should play a role in galaxy evolution, however despite the efforts, the exact role of the galaxy's local environment to its evolution remains open. This thesis introduction discusses briefly the background cosmology, cosmological N-body simulations and semi-analytical models. The second part is reserved for groups of galaxies, whether they are gravitationally bound, and what this may imply for galaxy evolution. The third part of the thesis concentrates on describing results of a case study of isolated field elliptical galaxies. The final chapter discusses another case study of luminous infra-red galaxies.

  10. Dark Matter Searches with Cherenkov Telescopes: Nearby Dwarf Galaxies or Local Galaxy Clusters?

    SciTech Connect

    Sanchez-Conde, Miguel A.; Cannoni, Mirco; Zandanel, Fabio; Gomez, Mario E.; Prada, Francisco; /IAA, Granada

    2012-06-06

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  11. Resolving the Tip of the Red Giant Branch of Two New Candidate Local Group Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Tollerud, Erik

    2014-10-01

    We propose to use ACS/WFC to observe two faint dwarf galaxies recently discovered via their HI emission. Based on a blind HI search of 40 HI clumps from 7500 square degrees of the GALFA-HI survey, these two candidates are the only objects with optical counterparts. They show HI and Halpha emission consistent with nearby galaxies, and have blue stars that are barely resolved in ground-based optical imaging with good seeing. These resolved stars are consistent with the galaxies being at Local Group distances. If they are in the Local Group, these galaxies are both less luminous and more compact than the recently-discovered Leo P, also found first with HI observations. They may then also be the faintest known star-forming galaxies. The ground-based imaging leaves large distance uncertainty, however, because the tip of the red giant branch cannot be resolved. We propose one orbit per galaxy of ACS/WFC imaging in F606W and F814W to measure accurate TRGB distances and determine if they truly are Local Group galaxies. If so, these galaxies provide tests on both the efficacy of Lambda CDM in predicting the properties of dwarf galaxies in low density environments, and the lowest-luminosity data points on models of galaxy star formation.

  12. Bar Evolution and Bar Properties from Disc Galaxies in the Early Universe

    NASA Astrophysics Data System (ADS)

    Hutchinson-Smith, Tenley; Simmons, Brooke

    2017-01-01

    Bars in disc galaxies indicate a large collection of stars in a specific configuration of orbits that give the galaxy center a rectangular looking feature. Astronomers have discovered that these bars affect the distribution of matter in galaxies, and are also related to galaxy stellar mass and star formation history. Little is known about the specifics of how bars evolve and drive the evolution of their host galaxies because only a handful of bars have been studied in detail so far. I have examined a sample of 8,221 barred galaxies from the early universe to identify and examine correlations with galaxy properties. The data comes from Galaxy Zoo, an online citizen science project that allows anyone to classify and measure detailed properties of galaxies. I present results including the fraction of galaxies in the sample that have bars, and the variation of galaxy properties with bar length, including galaxy color and stellar mass. I also compare these results to barred galaxies in the local universe. I will discuss the implications of these results in the context of galaxy evolution overall, including the effect of dark matter on bars and galaxy evolution.

  13. MORPHOLOGY AND SIZE DIFFERENCES BETWEEN LOCAL AND HIGH-REDSHIFT LUMINOUS INFRARED GALAXIES

    SciTech Connect

    Rujopakarn, Wiphu; Rieke, George H.; Eisenstein, Daniel J.; Juneau, Stephanie

    2011-01-10

    We show that the star-forming regions in high-redshift luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and submillimeter galaxies (SMGs) have similar physical scales to those in local normal star-forming galaxies. To first order, their higher infrared (IR) luminosities result from higher luminosity surface density. We also find a good correlation between the IR luminosity and IR luminosity surface density in starburst galaxies across over five orders of magnitude of IR luminosity from local normal galaxies to z {approx} 2 SMGs. The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs. Based on this relationship, we suggest that luminosity surface density should serve as a more accurate indicator for the IR emitting environment, and hence the observable properties, of star-forming galaxies than their IR luminosity. We demonstrate this approach by showing that ULIRGs at z {approx} 1 and a lensed galaxy at z {approx} 2.5 exhibit aromatic features agreeing with local LIRGs that are an order of magnitude less luminous, but have similar IR luminosity surface density. A consequence of this relationship is that the aromatic emission strength in star-forming galaxies will appear to increase at z>1 for a given IR luminosity compared to their local counterparts.

  14. Representing properties locally.

    PubMed

    Solomon, K O; Barsalou, L W

    2001-09-01

    Theories of knowledge such as feature lists, semantic networks, and localist neural nets typically use a single global symbol to represent a property that occurs in multiple concepts. Thus, a global symbol represents mane across HORSE, PONY, and LION. Alternatively, perceptual theories of knowledge, as well as distributed representational systems, assume that properties take different local forms in different concepts. Thus, different local forms of mane exist for HORSE, PONY, and LION, each capturing the specific form that mane takes in its respective concept. Three experiments used the property verification task to assess whether properties are represented globally or locally (e.g., Does a PONY have mane?). If a single global form represents a property, then verifying it in any concept should increase its accessibility and speed its verification later in any other concept. Verifying mane for PONY should benefit as much from having verified mane for LION earlier as from verifying mane for HORSE. If properties are represented locally, however, verifying a property should only benefit from verifying a similar form earlier. Verifying mane for PONY should only benefit from verifying mane for HORSE, not from verifying mane for LION. Findings from three experiments strongly supported local property representation and ruled out the interpretation that object similarity was responsible (e.g., the greater overall similarity between HORSE and PONY than between LION and PONY). The findings further suggest that property representation and verification are complicated phenomena, grounded in sensory-motor simulations.

  15. ORBITAL DEPENDENCE OF GALAXY PROPERTIES IN SATELLITE SYSTEMS OF GALAXIES

    SciTech Connect

    Hwang, Ho Seong; Park, Changbom E-mail: cbp@kias.re.k

    2010-09-01

    We study the dependence of satellite galaxy properties on the distance to the host galaxy and the orbital motion (prograde and retrograde orbits) using the Sloan Digital Sky Survey (SDSS) data. From SDSS Data Release 7, we find 3515 isolated satellite systems of galaxies at z < 0.03 that contain 8904 satellite galaxies. Using this sample, we construct a catalog of 635 satellites associated with 215 host galaxies whose spin directions are determined by our inspection of the SDSS color images and/or by spectroscopic observations in the literature. We divide satellite galaxies into prograde and retrograde orbit subsamples depending on their orbital motion with respect to the spin direction of the host. We find that the number of galaxies in prograde orbit is nearly equal to that of retrograde orbit galaxies: the fraction of satellites in prograde orbit is 50% {+-} 2%. The velocity distribution of satellites with respect to their hosts is found to be almost symmetric: the median bulk rotation of satellites is -1 {+-} 8 km s{sup -1}. It is found that the radial distribution of early-type satellites in prograde orbit is strongly concentrated toward the host while that of retrograde ones shows much less concentration. We also find the orbital speed of late-type satellites in prograde orbit increases as the projected distance to the host (R) decreases while the speed decreases for those in retrograde orbit. At R less than 0.1 times the host virial radius (R < 0.1r{sub vir,host}), the orbital speed decreases in both prograde and retrograde orbit cases. Prograde satellites are on average fainter than retrograde satellites for both early and late morphological types. The u - r color becomes redder as R decreases for both prograde and retrograde orbit late-type satellites. The differences between prograde and retrograde orbit satellite galaxies may be attributed to their different origin or the different strength of physical processes that they have experienced through

  16. The coronal parameters of local Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Marinucci, A.; Tortosa, A.; NuSTAR AGN Physics Working Group

    2016-05-01

    One of the open problems for AGN is the nature of the primary X-ray emission: It is likely due to Comptonization of soft UV photons, but the optical depth and temperature of the emitting corona were largely unknown before the launch of the Nuclear Spectroscopic Telescope Array (NuSTAR). It is the first focusing hard X-ray telescope on orbit, ∼ 100 times more sensitive in the 10-79 keV band compared to previous observatories, enabling the study of AGN at high energies with high precision. We present and discuss the results on the hot corona parameters of active galactic nuclei that have been recently measured with NuSTAR (often in coordination with XMM-Newton, Suzaku, or wift) with unprecedented accuracy, in a number of local Seyfert galaxies.

  17. The coronal parameters of local Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Marinucci, A.

    2015-07-01

    One of the open problems for AGN is the nature of the primary X-ray emission: it is likely due to Comptonization of soft UV photons, but the optical depth and temperature of the emitting corona were largely unknown before the launch of NuSTAR. The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing X-ray telescope on orbit, ˜ 100 times more sensitive in the 10-80 keV band compared to previous observatories, enabling the study of AGN at high energies with high precision. We will present and discuss the results on the hot corona parameters of Active Galactic Nuclei that have been recently measured with NuSTAR (often in coordination with XMM-Newton or Suzaku) with unprecedented accuracy, in a number of local Seyfert galaxies.

  18. Restframe Optical Properties of Lyman Break Galaxies

    NASA Astrophysics Data System (ADS)

    Shapley, A. E.; Steidel, C. C.; Adelberger, K. L.; Pettini, M.; Dickinson, M. E.; Giavalisco, M.

    2000-12-01

    We review recent results from near-IR studies of z ~ 3 galaxies that have been selected by their broadband optical colors using the Lyman Break technique. Specifically, we discuss the use of near-IR imaging at J and Ks, in combination with previously obtained optical photometry, to untangle the degenerate effects of dust extinction and age on galaxy spectral energy distributions. We use the observed optical-to-infrared colors for a subsample of galaxies from our extensive high-redshift survey to constrain both the amount of dust and the ages of the observed stellar populations. Thus, we hope to learn about distribution of ages, unextincted star-formation rates, and formed stellar masses of these high-redshift galaxies. We also make use of the restframe UV luminosity function of Lyman Break galaxies, in combination with the distribution of restframe UV-to-optical colors (measured with the R-Ks color at z ~ 3), to determine the restframe optical luminosity function of Lyman Break galaxies. Finally, we describe new efforts, using near-infrared spectroscopy, to study familiar restframe optical nebular emission lines redshifted to 1.5 - 2.5 μm in z ~ 3 galaxies. The properties of these emission features should indicate the range of dynamical masses and metallicities of high redshift star-forming galaxies. We also hope to use the velocity offsets measured between restframe optical nebular lines, Lyman-α , and restframe-UV interstellar metal lines, to characterize the starburst-induced outflows present in Lyman Break galaxies, how they depend on other galaxy properties, and what their impact is on the surrounding intergalactic medium.

  19. Local Group dwarf galaxies: nature and nurture

    NASA Astrophysics Data System (ADS)

    Sawala, Till; Scannapieco, Cecilia; White, Simon

    2012-02-01

    We investigate the formation and evolution of dwarf galaxies in a high-resolution, hydrodynamical cosmological simulation of a Milky Way sized halo and its environment. Our simulation includes gas cooling, star formation, supernova feedback, metal enrichment and ultraviolet heating. In total, 90 satellites and more than 400 isolated dwarf galaxies are formed in the simulation, allowing a systematic study of the internal and environmental processes that determine their evolution. We find that 95 per cent of satellite galaxies are gas free at z= 0, and identify three mechanisms for gas loss: supernova feedback, tidal stripping and photoevaporation due to re-ionization. Gas-rich satellite galaxies are only found with total masses above ˜5 × 109 M⊙. In contrast, for isolated dwarf galaxies, a total mass of ˜109 M⊙ constitutes a sharp transition; less massive galaxies are predominantly gas free at z= 0, more massive, isolated dwarf galaxies are often able to retain their gas. In general, we find that the total mass of a dwarf galaxy is the main factor which determines its star formation, metal enrichment and its gas content, but that stripping may explain the observed difference in gas content between field dwarf galaxies and satellites with total masses close to 109 M⊙. We also find that a morphological transformation via tidal stripping of infalling, luminous dwarf galaxies whose dark matter is less concentrated than their stars cannot explain the high total mass-to-light ratios of the faint dwarf spheroidal galaxies.

  20. The Fossils of the First Galaxies in the Local Universe

    NASA Astrophysics Data System (ADS)

    Bovill, Mia Sauda

    We argue that, at least a fraction of the newly discovered population of ultra-faint dwarfs in the Local Group constitute the fossil relics of a once ubiquitous population of dwarf galaxies formed before reionization with maximum circular velocities, vmax < 20 km s -1, where vmax ˜ M 1/3. To follow the evolution and distribution of the fossils of the first galaxies on Local Volume, 5 - 10 Mpc, scales, we have developed a new method for generating initial conditions for ΛCDM N-body simulations which provides the necessary dynamic range. The initial distribution of particles represents the position, velocity and mass distribution of the dark and luminous ha- los extracted from pre-reionization simulations. We find that ultra-faint dwarfs have properties compatible with well preserved fossils of the first galaxies and are able to reproduce the observed luminosity-metallicity relation. However, because the brightest pre-reionization dwarfs form preferentially in overdense regions, they have merged into non-fossil halos with vmax > 20-30 km s-1. Hence, we find a luminosity threshold of true-fossils of 106 Lsolar, casting doubts on the classification of some classical dSphs as fossils. We also argue that the ultra-faints at R < 50 kpc, have had their stellar properties significantly modified by tides, and that a large population of fossils remains undetected due to log(Sigma V) < -1.4. Next, we show that fossils of the first galaxies have galactocentric distributions and cumulative luminosity func- tions consistent with observations. We predict there are ˜ 300 luminous satellites orbiting within Rvir of the Milky Way, ˜ 50-70% of which are fossils. Despite our multidimensional agreement at low luminosities, our primordial model produces an overabundance of bright dwarf satellites (LV > 105 Lsolar), with this "bright satellite problem" most evident in the outer parts of the Milky Way. We estimate that, although relatively bright (LV > 105 Lsolar), these ghostly

  1. Theoretical Modeling of Star-Forming Galaxies. I. Emission-Line Diagnostic Grids for Local and Low-Metallicity Galaxies

    NASA Astrophysics Data System (ADS)

    Levesque, Emily M.; Kewley, Lisa J.; Larson, Kirsten L.

    2010-02-01

    We use the newest generation of the Starburst99/Mappings code to generate an extensive suite of models to facilitate detailed studies of star-forming galaxies and their interstellar medium properties, particularly at low metallicities. The new models used include a rigorous treatment of metal opacities in the population synthesis modeling and more detailed dust physics in the photoionization code. These models span a wide range of physical parameters including metallicity, ionization parameter, and the adoption of both an instantaneous burst and continuous star formation history (SFH). We examine the agreement between our models and local (z < 0.1) star-forming galaxy populations from several large data sets, including the Sloan Digital Sky Survey, the Nearby Field Galaxy Survey, and samples of blue compact galaxies and metal-poor galaxies. We find that models adopting a continuous SFH reproduce the metallicity-sensitive line ratios observed in the local population of star-forming galaxies, including the low-metallicity sample. However, we find that the current codes generate an insufficiently hard ionizing radiation field, leading to deficiencies in the [S II] fluxes produced by the models. We consider the advantages and shortcomings of this suite of models, and discuss future work and improvements that can be applied to the modeling of star-forming galaxies.

  2. TWO LOCAL VOLUME DWARF GALAXIES DISCOVERED IN 21 cm EMISSION: PISCES A AND B

    SciTech Connect

    Tollerud, Erik J.; Geha, Marla C.; Grcevich, Jana; Putman, Mary E.; Stern, Daniel E-mail: marla.geha@yale.edu E-mail: mputman@astro.columbia.edu

    2015-01-01

    We report the discovery of two dwarf galaxies, Pisces A and B, from a blind 21 cm H I search. These were the only two galaxies found via optical imaging and spectroscopy of 22 H I clouds identified in the GALFA-H I survey as dwarf galaxy candidates. They have properties consistent with being in the Local Volume (<10 Mpc), and one has resolved stellar populations such that it may be on the outer edge of the Local Group (∼1 Mpc from M31). While the distance uncertainty makes interpretation ambiguous, these may be among the faintest star-forming galaxies known. Additionally, rough estimates comparing these galaxies to ΛCDM dark matter simulations suggest consistency in number density, implying that the dark matter halos likely to host these galaxies are primarily H I-rich. The galaxies may thus be indicative of a large population of dwarfs at the limit of detectability that are comparable to the faint satellites of the Local Group. Because they are outside the influence of a large dark matter halo to alter their evolution, these galaxies can provide critical anchors to dwarf galaxy formation models.

  3. The Connection between Galaxies and Dark Matter Structures in the Local Universe

    SciTech Connect

    Reddick, Rachel M.; Wechsler, Risa H.; Tinker, Jeremy L.; Behroozi, Peter S.

    2012-07-11

    We provide new constraints on the connection between galaxies in the local Universe, identified by the Sloan Digital Sky Survey (SDSS), and dark matter halos and their constituent substructures in the {Lambda}CDM model using WMAP7 cosmological parameters. Predictions for the abundance and clustering properties of dark matter halos, and the relationship between dark matter hosts and substructures, are based on a high-resolution cosmological simulation, the Bolshoi simulation. We associate galaxies with dark matter halos and subhalos using subhalo abundance matching, and perform a comprehensive analysis which investigates the underlying assumptions of this technique including (a) which halo property is most closely associated with galaxy stellar masses and luminosities, (b) how much scatter is in this relationship, and (c) how much subhalos can be stripped before their galaxies are destroyed. The models are jointly constrained by new measurements of the projected two-point galaxy clustering and the observed conditional stellar mass function of galaxies in groups. We find that an abundance matching model that associates galaxies with the peak circular velocity of their halos is in good agreement with the data, when scatter of 0.20 {+-} 0.03 dex in stellar mass at a given peak velocity is included. This confirms the theoretical expectation that the stellar mass of galaxies is tightly correlated with the potential wells of their dark matter halos before they are impacted by larger structures. The data put tight constraints on the satellite fraction of galaxies as a function of galaxy stellar mass and on the scatter between halo and galaxy properties, and rule out several alternative abundance matching models that have been considered. This will yield important constraints for galaxy formation models, and also provides encouraging indications that the galaxy - halo connection can be modeled with sufficient fidelity for future precision studies of the dark Universe.

  4. Outskirts of Local Group Dwarf Galaxies Revealed by Subaru Hyper Suprime-Cam

    NASA Astrophysics Data System (ADS)

    Komiyama, Yutaka

    2017-03-01

    Local Group galaxies are important targets since their stellar populations can be resolved, and their properties can be investigated in detail with the help of stellar evolutionary models. The newly-built instrument for the 8.2m Subaru Telescope, Hyper Suprime-Cam (HSC), which has a 1 Giga pixel CCD camera with 1.5 degrees field of view, is the best instrument for observing Local Group galaxies. We have carried out a survey for Local Group dwarf galaxies using HSC aiming to shed light on the outskirts of these galaxies. The survey covers target galaxies out beyond the tidal radii down to a depth unexplored by previous surveys. Thanks to the high spatial resolution and high sensitivity provided by the Subaru Telescope, we are able to investigate properties such as spatial distribution and stellar population from the very center of galaxies to the outskirts. In this article, I will show results for the dwarf irregular galaxy NGC 6822 and the dwarf spheroidal galaxy Ursa Minor.

  5. Morphological Peculiarity Indices of Local and Distant Galaxies

    NASA Astrophysics Data System (ADS)

    Wu, K. L.; Faber, S. M.; Lauer, T. R.

    1998-12-01

    Detailed images from the Hubble Space Telescope (HST) have sparked a surge of interest in morphological peculiarities in both distant and local galaxies. Several groups have developed criteria by which to automatically classify galaxy morphology (e.g., Abraham et al. 1996, Naim et al. 1997). In order to study peculiar galaxies at high redshifts, it is crucial to have a solid understanding of both the morphological peculiarities in local galaxies and the appearance of these features when observed at higher redshifts. We are developing several algorithms, or peculiarity indices, to quantify the types and degree of peculiarity seen in galaxy morphology. It is not our aim to classify galaxies on the ``normal'' Hubble Sequence. The focus of this work is an asymmetry index, which is a variation of that presented by Abraham et al. 1996. The indices are applied initially to two samples: (1) a local galaxy sample, comprised of the Frei, et al. 1996 ``Catalog of Nearby Galaxies,'' along with several merger candidates from two runs on the Lick Observatory Nickel 40-inch telescope by one of the authors (KLW); and (2) simulations of the above sample of galaxies cosmologically shifted to z ~ 0.8. This study expands upon previous work by providing a realistic view of which local morphological features we can expect to measure robustly when observed at high redshifts with the current observational technology.

  6. The isolated dSph galaxy KKs3 in the local Hubble flow

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.; Kniazev, A. Yu.; Sharina, M. E.

    2015-09-01

    We present SALT spectroscopy of a globular cluster in the center of the nearby isolated dSph galaxy KKs3 situated at a distance of 2.12 Mpc. Its heliocentric radial velocity is 316 ± 7 km s-1 that corresponds to V_LG = 112 km s-1 in the Local Group (LG) reference frame. We use its distance and velocity along with the data on other 35 field galaxies in the proximity of the LG to trace the local Hubble flow. The following basic properties of the local field galaxies are briefly discusse: morphology, absolute magnitudes, average surface brightnesses, specific star formation rates, and hydrogen mass-to-stellar mass ratios. Surprisingly, the sample of the neighboring isolated galaxies displays no signs of compression under the influence of the expanding Local Void.

  7. The Local Dwarf GALAXIES:BUILDING Blocks of Massive Ones? I.THE Fornax Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    Nykytyuk, T. V.

    A chemical evolution of the Local Group dwarf galaxy Fornax is considered in the framework of the merger scenario. We suppose a galactic stellar halo to be formed as separate fragments which then merge; thus, we can calculate the set of such the fragments to reproduce the observed metallicity distribution function of a galaxy. Accordingly, if dwarf galaxies were such the systems, which, once merged, have formed massive galaxies, we need to obtain only one fragment to reproduce the observed metallicity distribution function of a dwarf galaxy. To test this assumption, the stellar metallicity distribution functions of Fornax was calculated in the framework of the merger scenario. The more than one fragment was obtained for galaxy under consideration; thus, it is unlikely the systems similar to Fornax to be building blocks of massive galaxies.

  8. Dynamically hot galaxies. I - Structural properties

    NASA Technical Reports Server (NTRS)

    Bender, Ralf; Burstein, David; Faber, S. M.

    1992-01-01

    Results are reported from an analysis of the structural properties of dynamically hot galaxies which combines central velocity dispersion, effective surface brightness, and effective radius into a new 3-space (k), in which the axes are parameters that are physically meaningful. Hot galaxies are found to divide into groups in k-space that closely parallel conventional morphological classifications, namely, luminous ellipticals, compacts, bulges, bright dwarfs, and dwarf spheroidals. A major sequence is defined by luminous ellipticals, bulges, and most compacts, which together constitute a smooth continuum in k-space. Several properties vary smoothly with mass along this continuum, including bulge-to-disk ratio, radio properties, rotation, degree of velocity anisotropy, and 'unrelaxed'. A second major sequence is comprised of dwarf ellipticals and dwarf spheroidals. It is suggested that mass loss is a major factor in hot dwarf galaxies, but the dwarf sequence cannot be simply a mass-loss sequence, as it has the wrong direction in k-space.

  9. Deriving Physical Properties from Broadband Photometry with Prospector: Description of the Model and a Demonstration of its Accuracy Using 129 Galaxies in the Local Universe

    NASA Astrophysics Data System (ADS)

    Leja, Joel; Johnson, Benjamin D.; Conroy, Charlie; van Dokkum, Pieter G.; Byler, Nell

    2017-03-01

    Broadband photometry of galaxies measures an unresolved mix of complex stellar populations, gas, and dust. Interpreting these data is a challenge for models: many studies have shown that properties derived from modeling galaxy photometry are uncertain by a factor of two or more, and yet answering key questions in the field now requires higher accuracy than this. Here, we present a new model framework specifically designed for these complexities. Our model, Prospector- α, includes dust attenuation and re-radiation, a flexible attenuation curve, nebular emission, stellar metallicity, and a six-component nonparametric star formation history. The flexibility and range of the parameter space, coupled with Monte Carlo Markov chain sampling within the Prospector inference framework, is designed to provide unbiased parameters and realistic error bars. We assess the accuracy of the model with aperture-matched optical spectroscopy, which was excluded from the fits. We compare spectral features predicted solely from fits to the broadband photometry to the observed spectral features. Our model predicts Hα luminosities with a scatter of ∼0.18 dex and an offset of ∼0.1 dex across a wide range of morphological types and stellar masses. This agreement is remarkable, as the Hα luminosity is dependent on accurate star formation rates, dust attenuation, and stellar metallicities. The model also accurately predicts dust-sensitive Balmer decrements, spectroscopic stellar metallicities, polycyclic aromatic hydrocarbon mass fractions, and the age- and metallicity-sensitive features Dn4000 and Hδ. Although the model passes all these tests, we caution that we have not yet assessed its performance at higher redshift or the accuracy of recovered stellar masses.

  10. Were Progenitors of Local L* Galaxies Lyα Emitters at High Redshift?

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    The Lyα emission has been observed from galaxies over a redshift span z ~ 0-8.6. However, the evolution of high-redshift Lyα emitters (LAEs), and the link between these populations and local galaxies, remains poorly understood. Here, we investigate the Lyα properties of progenitors of a local L* galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART2 code. We find that the main progenitor (the most massive one) of a Milky-Way-like galaxy has a number of Lyα properties close to those of observed LAEs at z ~ 2-6, but most of the fainter ones appear to fall below the detection limits of current surveys. The Lyα photon escape fraction depends sensitively on a number of physical properties of the galaxy, such as mass, star formation rate, and metallicity, as well as galaxy morphology and orientation. Moreover, we find that high-redshift LAEs show blueshifted Lyα line profiles characteristic of gas inflow, and that the Lyα emission by excitation cooling increases with redshift, and becomes dominant at z >~ 6. Our results suggest that some observed LAEs at z ~ 2-6 with luminosity of L Lyα ~ 1042-1043 erg s-1 may be similar to the main progenitor of the Milky Way at high redshift, and that they may evolve into present-day L* galaxies.

  11. Physical and observable properties of the first galaxies

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    The Hubble Ultra Deep Field and Frontier Fields have discovered over 1,500 galaxies at redshifts greater than 6. We present observational predictions for this high-redshift population, using the Renaissance Simulations, a suite of high-resolution cosmological simulations, that enables the correlation between key observables and the physical properties of the first galaxies in the Universe. Using a sample of over 3,000 resolved galaxies along with the formation of 10,000 massive Population III stars, we show that the luminosity function flattens above a UV magnitude of -14 but does not drop to zero even to our resolution limit of M_UV = -4. We find that dark matter halos below the atomic cooling limit (~10^8 M_sun) can form stars if they are chemically enriched, and they have similar mass-to-light ratios as local ultra-faint dwarfs. We utilize stellar population synthesis models, dust extinction using Monte Carlo methods, and photo-ionization modeling, all sourced from the simulation data, to obtain synthetic observations of the first galaxies. Using these results, we will be able to constrain the following properties of the first galaxies: (1) star formation histories and stellar populations, (2) nebular emission and dust extinction, and (3) the faint end of the luminosity function.

  12. Star Formation at Low Metallicity in Local Dwarf Irregular Galaxies

    NASA Astrophysics Data System (ADS)

    Elmegreen, Bruce; Hunter, Deidre Ann; Rubio, Monica; Brinks, Elias; Cortés, Juan R.; Cigan, Phil

    2016-01-01

    The radial profiles of star formation rates and surface mass densities for gas and stars have been compiled for 20 local dwarf irregular galaxies and converted into disk scale heights and Toomre Q values. The scale heights are relatively large compared to the galaxy sizes (~0.6 times the local radii) and generally increase with radius in a flare. The gaseous Q values are high, ~4, at most radii and even higher for the stars. Star formation proceeds even with these high Q values in a normal exponential disk as viewed in the far ultraviolet. Such normal star formation suggests that Q is not relevant to star formation in dIrrs. The star formation rate per unit area always equals approximately the gas surface density divided by the midplane free fall time with an efficiency factor of about 1% that decreases systematically with radius in approximate proportion to the gas surface density. We view this efficiency variation as a result of a changing molecular fraction in a disk where atomic gas dominates both stars and molecules. In a related study, CO observations with ALMA of star-forming regions at the low metallicities of these dwarfs, which averages 13% solar, shows, in the case of the WLM galaxy, tiny CO clouds inside much larger molecular and atomic hydrogen envelopes. The CO cloud mass fraction within the molecular region is only one percent or so. Nevertheless, the CO clouds have properties that are similar to solar neighborhood clouds: they satisfy the size-linewidth relation observed in the LMC, SMC, and other local dwarfs where CO has been observed, and the same virial mass versus luminosity relation. This uniforming of CO cloud properties seems to be the result of a confining pressure from the weight of the overlying molecular and atomic shielding layers. Star formation at low metallicity therefore appears to be a three dimensional process independent of 2D instabilities involving Q, in highly atomic gas with relatively small CO cores, activated at a rate

  13. The chemical evolution of galaxies in the local volume

    NASA Astrophysics Data System (ADS)

    Croxall, Kevin V.

    2010-12-01

    The composition of the universe has greatly changed since the first matter condensed from the primordial soup of the Big Bang. As galaxies have grown and evolved over the past Hubble time, massive luminous galaxies have built up more heavy elements than their low mass counterparts. While sundry physical mechanisms have been proposed to account for this observed trend, the physical connection between galaxy mass and metallicity has evaded the understanding of astronomers for several decades. In order to gain a greater understanding of this metallicity-luminosity relation and the physical drivers behind the chemical evolution of galaxies, we have performed a detailed study of galaxies in both isolated and non-isolated environments: namely, galaxies in the local volume (D ≤ 5 Mpc) and galaxy members belonging to the M81 group. Our results from studying the M81 group imply that recent interactions among the central galaxies in this group, rather than mechanisms intrinsic to the galaxies, are likely responsible for the anomalously high abundances in three cluster members. While tidal interactions can alter the chemical make up the galaxies involved, the well established metallicity-luminosity relation indicates a more universal chemical evolution. To further explore this idea, we analyze galaxy abundances, stellar & gas distributions, and kinematics from both new and archival observations of forty-five low mass galaxies within 5 Mpc of the Milky Way. Our results indicate that these galaxies occupy a different mass-to-light ratio parameter space than their larger counter parts. Our study of the local volume explores the effects of various galaxy attributes such as mass, star formation rate, gas mass fraction, and the mass distribution that offer more concrete connections with the evolution of the system. We show that none of the attributes measured in this study exhibit more correlation with metallicity (measured via nebular oxygen abundances) than does the luminosity

  14. Census of the Local Universe (CLU) Galaxy Survey: Results Within Preliminary Fields

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Kasliwal, Mansi M.; Van Sistine, Angela; Dale, Daniel A.; Sutter, Jessica; Turner, Jordan; Parziale, Ryan; iPTF Team

    2017-01-01

    We present an analysis of galaxy candidates in 15 (out of ~3600) preliminary fields of the Census of the Local Universe (CLU) galaxy survey. The intermediate Palomar Transient Factory (iPTF) is undertaking the CLU project to complete our survey of galaxies out to 200 Mpc (z ˜ 0.05) and deploys 4 wavelength-adjacent, narrowband filters to search for emission line (Hα) sources across 3π (~28,000 deg^2) of the sky. Using the Palomar 200-inch Hale telescope, we have obtained spectroscopic follow-up observations with which we can verify each candidate’s redshift and derive galaxy properties. In addition, we present some interesting galaxies in our candidate list (e.g., green peas) whose extreme properties (e.g., low metallicity and high star formation rate) are similar to those of higher redshift galaxies (z>2). We will expand our analysis to all ~3600 fields and anticipate finding tens-of-thousands of new galaxies in the local Universe over the next year.

  15. HII regions in dwarf irregular galaxies of the local group

    NASA Technical Reports Server (NTRS)

    Hodge, Paul; Lee, Myung Gyoon

    1990-01-01

    Deep, narrowband H alpha Charge Coupled Device (CCD) surveys of HII regions were carried out in several dwarf irregular galaxies in and near the local group. Data are now complete for these galaxies: NGC 6822, GR 8, IC 10, IC 1613, Sextans A, Sextans B, and Sag Irr. Observations are complete for DDO 47, 53, 167, 168 and 187. Details of some of the results for the surveys completed so far are discussed. For NGC 6822, CCD survey at H alpha resulted in the detection of 145 HII regions in the local group irregular galaxy NGC 6822. Most of them are newly detected, faint surface-brightness objects. Positions, maps and dimensions are being published elsewhere. For GR 8, a deep narrowband H alpha imaging of the nearby dwarf irregular galaxy GR 8 revealed a total of 32 HII regions. Positions, H alpha luminosities, and sizes of these objects were determined. The H alpha luminosity function has the same shape as that for more luminous galaxies, except for size of sample effects. Most HII regions detected are at the very low luminosity end of the general luminosity function. For IC 10, a deep CCD narrowband H alpha imaging of the local group dwarf irregular galaxy IC 10 revealed a total of 144 HII regions. Positions, H alpha luminosities, and sizes of these objects were determined. The H alpha luminosity function has the same shape as that for more luminous galaxies.

  16. 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.

  17. The Spitzer Local Volume Legacy Survey: Infrared Imaging and Photometry for 258 Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Dale, Daniel A.; LVL Team

    2009-01-01

    Near-, mid-, and far-infrared flux properties are presented for the Local Volume Legacy survey, a Spitzer Space Telescope legacy program built upon a foundation of GALEX ultraviolet and ground-based Hα imaging of 258 galaxies within 11 Mpc. The Local Volume Legacy survey covers an unbiased, representative, and statistically robust sample of nearby star-forming galaxies, exploiting the faintest absolute depth and highest extragalactic spatial resolution achievable with Spitzer. As a result of its approximately volume-limited nature, LVL augments previous Spitzer observations of present-day galaxies (such as from SINGS, the Spitzer Infrared Nearby Galaxies Survey) with improved sampling of the low-luminosity dwarf galaxy population. LVL's unique sample selection results in a large spread in mid-infrared colors, likely due to the conspicuous deficiency of PAH emission from low-metallicity galaxies. Conversely, the LVL sample shows a tighter correlation in the infrared-to-ultraviolet ratio versus ultraviolet spectral slope, due in large part to the lack of luminous early-type galaxies in the Local Volume.

  18. Galaxy formation with local photoionization feedback - I. Methods

    NASA Astrophysics Data System (ADS)

    Kannan, R.; Stinson, G. S.; Macciò, A. V.; Hennawi, J. F.; Woods, R.; Wadsley, J.; Shen, S.; Robitaille, T.; Cantalupo, S.; Quinn, T. R.; Christensen, C.

    2014-01-01

    We present a first study of the effect of local photoionizing radiation on gas cooling in smoothed particle hydrodynamics simulations of galaxy formation. We explore the combined effect of ionizing radiation from young and old stellar populations. The method computes the effect of multiple radiative sources using the same tree algorithm as used for gravity, so it is computationally efficient and well resolved. The method foregoes calculating absorption and scattering in favour of a constant escape fraction for young stars to keep the calculation efficient enough to simulate the entire evolution of a galaxy in a cosmological context to the present day. This allows us to quantify the effect of the local photoionization feedback through the whole history of a galaxy's formation. The simulation of a Milky Way-like galaxy using the local photoionization model forms ˜40 per cent less stars than a simulation that only includes a standard uniform background UV field. The local photoionization model decreases star formation by increasing the cooling time of the gas in the halo and increasing the equilibrium temperature of dense gas in the disc. Coupling the local radiation field to gas cooling from the halo provides a preventive feedback mechanism which keeps the central disc light and produces slowly rising rotation curves without resorting to extreme feedback mechanisms. These preliminary results indicate that the effect of local photoionizing sources is significant and should not be ignored in models of galaxy formation.

  19. ENVIRONMENTAL DEPENDENCE OF OTHER GALAXY PROPERTIES FOR HIGH STELLAR MASS AND LOW STELLAR MASS GALAXIES

    SciTech Connect

    Deng Xinfa; Wen Xiaoqing; Xu Jianying; Ding Yingping; Huang Tong

    2010-06-10

    At a stellar mass of 3 x 10{sup 10} M {sub {Theta}} we divide the volume-limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6) into two distinct families and explore the environmental dependence of galaxy properties for High Stellar Mass (HSM) and Low Stellar Mass (LSM) galaxies. It is found that for HSM and LSM galaxies, the environmental dependence of some typical galaxy properties, such as color, morphologies, and star formation activities, is still very strong, which at least shows that the stellar mass is not fundamental in correlations between galaxy properties and the environment. We also note that the environmental dependence of the size for HSM and LSM galaxies is fairly weak, which is mainly due to the galaxy size being insensitive to environment.

  20. The Role of Host Galaxy for the Environmental Dependence of Active Nuclei in Local Galaxies

    NASA Astrophysics Data System (ADS)

    Davies, Richard I.; Hicks, E. K. S.; Erwin, P.; Burtscher, L.; Contursi, A.; Genzel, R.; Janssen, A.; Koss, M.; Lin, M.-Y.; Lutz, D.; Maciejewski, W.; Müller-Sánchez, F.; Orban de Xivry, G.; Ricci, C.; Riffel, R.; Riffel, R. A.; Rosario, D.; Schartmann, M.; Schnorr-Müller, A.; Shimizu, T.; Sternberg, A.; Sturm, E.; Storchi-Bergmann, T.; Tacconi, L.; Veilleux, S.

    2017-01-01

    We discuss the environment of local hard X-ray selected active galaxies, with reference to two independent group catalogues. We find that the fraction of these AGN in S0 host galaxies decreases strongly as a function of galaxy group size (halo mass) - which contrasts with the increasing fraction of galaxies of S0 type in denser environments. However, there is no evidence for an environmental dependence of AGN in spiral galaxies. Because most AGN are found in spiral galaxies, this dilutes the signature of environmental dependence for the population as a whole. We argue that the differing results for AGN in disk-dominated and bulge-dominated galaxies is related to the source of the gas fuelling the AGN, and so may also impact the luminosity function, duty cycle, and obscuration. We find that there is a significant difference in the luminosity function for AGN in spiral and S0 galaxies, and tentative evidence for some difference in the fraction of obscured AGN.

  1. Dust properties of Lyman-break galaxies in cosmological simulations

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Nagamine, Kentaro; Thompson, Robert; Choi, Jun-Hwan

    2014-04-01

    Recent observations have indicated the existence of dust in high-redshift galaxies, however, the dust properties in them are still unknown. Here we present theoretical constraints on dust properties in Lyman-break galaxies (LBGs) at z = 3 by post-processing a cosmological smoothed particle hydrodynamics simulation with radiative transfer calculations. We calculate the dust extinction in 2800 dark matter haloes using the metallicity information of individual gas particles in our simulation. We use only bright galaxies with rest-frame ultraviolet (UV) magnitude M1700 < -20 mag, and study the dust size, dust-to-metal mass ratio, and dust composition. From the comparison of calculated colour excess between B and V band [i.e. E(B - V)] and the observations, we constrain the typical dust size, and show that the best-fitting dust grain size is ˜ 0.05 μm, which is consistent with the results of theoretical dust models for Type II supernova. Our simulation with the dust extinction effect can naturally reproduce the observed rest-frame UV luminosity function of LBGs at z = 3 without assuming an ad hoc constant extinction value. In addition, in order to reproduce the observed mean E(B - V), we find that the dust-to-metal mass ratio needs to be similar to that of the local galaxies, and that the graphite dust is dominant or at least occupy half of dust mass.

  2. What determines large scale galaxy clustering: halo mass or local density?

    NASA Astrophysics Data System (ADS)

    Pujol, Arnau; Hoffmann, Kai; Jiménez, Noelia; Gaztañaga, Enrique

    2017-02-01

    Using a dark matter simulation we show how halo bias is determined by local density and not by halo mass. This is not totally surprising as, according to the peak-background split model, local matter density (bar δ) is the property that constrains bias at large scales. Massive haloes have a high clustering because they reside in high density regions. Small haloes can be found in a wide range of environments which differentially determine their clustering amplitudes. This contradicts the assumption made by standard halo occupation distribution (HOD) models that bias and occupation of haloes is determined solely by their mass. We show that the bias of central galaxies from semi-analytic models of galaxy formation as a function of luminosity and colour is therefore not correctly predicted by the standard HOD model. Using bar δ (of matter or galaxies) instead of halo mass, the HOD model correctly predicts galaxy bias. These results indicate the need to include information about local density and not only mass in order to correctly apply HOD analysis in these galaxy samples. This new model can be readily applied to observations and has the advantage that, in contrast with the dark matter halo mass, the galaxy density can be directly observed.

  3. How Typical Are the Local Group Dwarf Galaxies?

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Dolphin, Andrew E.; Dalcanton, Julianne J.; Skillman, Evan D.; Holtzman, Jon; Williams, Benjamin F.; Gilbert, Karoline M.; Seth, Anil C.; Cole, Andrew; Gogarten, Stephanie M.; Rosema, Keith; Karachentsev, Igor D.; McQuinn, Kristen B. W.; Zaritsky, Dennis

    2011-12-01

    We compare the cumulative star formation histories (SFHs) of Local Group (LG) dwarf galaxies with those in the volume-limited ACS Nearby Galaxy Survey Treasury (ANGST) sample (D <~ 4 Mpc), in order to understand how typical the LG dwarf galaxies are relative to those in the nearby universe. The SFHs were derived in a uniform manner from high-quality optical color-magnitude diagrams constructed from Hubble Space Telescope imaging. We find that the mean cumulative SFHs of the LG dwarfs are comparable to the mean cumulative SFHs of the ANGST sample for the three different morphological types (dwarf spheroidals/ellipticals: dSph/dE; dwarf irregulars: dI; transition dwarfs: dTrans). We also discuss effects such as population gradients and systematic uncertainties in the stellar models that may influence the derived SFHs. Both the ANGST and LG dwarf galaxies show a consistent and strong morphology-density relationship, emphasizing the importance of environment in the evolution of dwarf galaxies. Specifically, we confirm that dIs are found at lower densities and higher luminosities than dSphs, within this large sample. We also find that dTrans are located in similar environments to those occupied by dwarf irregular galaxies, but have systematically lower luminosities that are more comparable to those of dwarf spheroidals. The similarity of the SFHs and morphology-density relationships of the LG and ANGST dwarf galaxies suggests that the LG dwarfs are a good representation of dwarf galaxies in the local universe. Based on 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., under NASA contract NAS 5-26555.

  4. H(alpha) and Optical Imaging of Local Volume Galaxies in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Sakai, Shoko; van Zee, Liese; Lee, Janice C.; Kennicutt, Robert C.; Funes, Jose G.

    2010-02-01

    We propose H(alpha) and B,R imaging observations of 33 galaxies in the Local Volume Legacy (LVL) survey to measure current star formation activity and derive emission-line corrected optical colors throughout the stellar disk. The proposed imaging observations will be combined with existing UV and IR observations, and will serve to nearly complete the optical imaging coverage of the full LVL sample of 258 galaxies. The observed surface photometry and radial trace of the star formation activity will allow us to study the photometric properties, the morphology, and spatial distributions of different stellar populations in these nearby galaxies. These images will also form the basis for a definitive multiwavelength dataset for studies of star formation in nearby galaxies.

  5. Metallicity gradients in local Universe galaxies: Time evolution and effects of radial migration

    NASA Astrophysics Data System (ADS)

    Magrini, Laura; Coccato, Lodovico; Stanghellini, Letizia; Casasola, Viviana; Galli, Daniele

    2016-04-01

    Context. Our knowledge of the shape of radial metallicity gradients in disc galaxies has recently improved. Conversely, the understanding of their time evolution is more complex, since it requires analysis of stellar populations with different ages or systematic studies of galaxies at different redshifts. In the local Universe, H ii regions and planetary nebulae (PNe) are important tools to investigate radial metallicity gradients in disc galaxies. Aims: We present an in-depth study of all nearby spiral galaxies (M33, M31, NGC 300, and M81) with direct-method nebular abundances of both populations, aiming at studying the evolution of their radial metallicity gradients. For the first time, we also evaluate the radial migration of PN populations. Methods: For the selected galaxies, we analysed H ii region and PN properties to: determine whether oxygen in PNe is a reliable tracer for past interstellar medium (ISM) composition; homogenise published datasets; estimate the migration of the oldest stellar populations; and determine the overall chemical enrichment and slope evolution. Results: We confirm that oxygen in PNe is a reliable tracer for past ISM metallicity. We find that PN gradients are flatter than or equal to those of H ii regions. When radial motions are negligible, this result provides a direct measurement of the time evolution of the gradient. For galaxies with dominant radial motions, we provide upper limits on the gradient evolution. Finally, the total metal content increases with time in all target galaxies, and early morphological types have a larger increment Δ(O/H) than late-type galaxies. Conclusions: Our findings provide important constraints to discriminate among different galactic evolutionary scenarios, favouring cosmological models with enhanced feedback from supernovae. The advent of extremely large telescopes allows us to include galaxies in a wider range of morphologies and environments, thus putting firmer constraints on galaxy formation

  6. Exploring the Escape of Hydrogen Ionizing Photons from Local Galaxies

    NASA Astrophysics Data System (ADS)

    Davis, Jesse A.; Rosenberg, Jessica L.; Venkatesan, Aparna; Cannon, John M.; Salzer, John Joseph

    2016-01-01

    role of dwarf galaxies in the ionization of the local IGM and cosmic reionization.

  7. Frequent Spin Reorientation of Galaxies due to Local Interactions

    NASA Astrophysics Data System (ADS)

    Cen, Renyue

    2014-04-01

    We study the evolution of angular momenta of M * = 1010-1012 M ⊙ galaxies utilizing large-scale ultra-high resolution cosmological hydrodynamic simulations and find that the spin of the stellar component changes direction frequently because of interactions with nearby systems, such as major mergers, minor mergers, significant gas inflows, and torques. The rate and nature of change of spin direction cannot be accounted for by large-scale tidal torques, because the rates of the latter fall short by orders of magnitude and because the apparent random swings of the spin direction are inconsistent with the alignment by linear density field. The implications for galaxy formation as well as the intrinsic alignment of galaxies are profound. Assuming the large-scale tidal field is the sole alignment agent, a new picture emerging is that intrinsic alignment of galaxies would be a balance between slow large-scale coherent torquing and fast spin reorientation by local interactions. What is still open is whether other processes, such as feeding galaxies with gas and stars along filaments or sheets, introduce coherence for spin directions of galaxies along the respective structures.

  8. Semi-analytic models for HI gas in disk and local dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Fu, Jian

    2015-08-01

    We construct the radially-resolved semi-analytic models of galaxy formation based on the L-Galaxies model framework, which include both atomic and molecular gas phase in ISM. The models adopt the ΛCDM cosmology simulation Millennium, Millennium II and Aquarius. Our models can reproduce varies properties of HI gas in nearby galaxies, e.g. the HI mass function, the HI-to-star ratio vs stellar mass and stellar surface density, universal HI radial surface density profile in outer disks etc. We can also give some physical origins of HI size mass relation in many observations.Based on our model results for local dwarf galaxies, we show that the "missing satellite problem" also exists in the HI component, i.e., the models over predict dwarf galaxies with low HI mass. That is a shortcoming of current ΛCDM cosmology framework. Future survey for HI gas in dwarf galaxies (e.g. SKA or FAST) in local group can help to verify the correctness of cold dark matter.

  9. Feedback in the local Universe: Relation between star formation and AGN activity in early type galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher; Baum, Stefi; Jones, Christine; Forman, William; Whitmore, Samantha; Ahmed, Rabeea; Pierce, Katherine; Leary, Sara

    2015-08-01

    Aim: We address the relation between star formation and AGN activity in a large sample of nearby early type (E and S0) galaxies. The redshift range of the galaxies is 0.0002galaxy evolution and formation. Evidence of AGN feedback is found in massive galaxies in galaxy clusters. However, how common AGN feedback is in the local universe and in small scale systems is still not evident.Methods: To answer this question, we carried out a multiple wavelength study of a sample of 231 early type galaxies which were selected to have an apparent K-band magnitude brighter than 13.5 and whose positions correlate with Chandra ACIS-I and ACIS-S sources. The galaxies in the sample are unbiased regarding their star formation and radio source properties. Using the archival observations at radio, IR and UV from VLA, WISE and GALEX respectively, we obtained the radio power, estimate FUV star formation rate (SFR) and other galaxy properties to study AGN activity and ongoing star formation.Results: The relationship between radio power and stellar mass shows that there is an upper envelope of radio power that is a steep function of stellar luminosity. This suggests that less massive galaxies have low radio power while massive galaxies are capable of hosting powerful radio sources. The Radio-MIR relation shows that galaxies with P>=1022 WHz-1 are potential candidates for being AGN. About ~ 7% of the sample show evidence of ongoing star formation with SFR ranging from 10-3 to 1 M⊙yr-1. These are also less massive and radio faint suggesting the absence of active accretion. There is nearly equal fraction of star forming galaxies in radio faint (P<1022 WHz-1) and radio bright galaxies (P>=1022 WHz-1) . Only ~ 5% of the galaxies in our sample have P>=1022 WHz-1 and most of them do not show evidence of bright accretion disks. We see a weak correlation and a dispersion of

  10. Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

    NASA Astrophysics Data System (ADS)

    De Propris, Roberto; Baldry, Ivan K.; Bland-Hawthorn, Joss; Brough, Sarah; Driver, Simon P.; Hopkins, Andrew M.; Kelvin, Lee; Loveday, Jon; Phillipps, Steve; Robotham, Aaron S. G.

    2014-11-01

    We derive the close pair fractions and volume merger rates for galaxies in the Galaxy and Mass Assembly (GAMA) survey with -23 < Mr < -17 (ΩM = 0.27, ΩΛ = 0.73, H0 = 100 km s-1 Mpc-1) at 0.01 < z < 0.22 (look-back time of <2 Gyr). The merger fraction is approximately 1.5 per cent Gyr-1 at all luminosities (assuming 50 per cent of pairs merge) and the volume merger rate is ≈3.5 × 10-4 Mpc-3 Gyr-1. We examine how the merger rate varies by luminosity and morphology. Dry mergers (between red/spheroidal galaxies) are found to be uncommon and to decrease with decreasing luminosity. Fainter mergers are wet, between blue/discy galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (-23 < Mr < -20), the merger rate evolution is flat, irrespective of colour or morphology, out to z ˜ 0.2. The makeup of the merging population does not appear to change over this redshift range. Galaxy growth by major mergers appears comparatively unimportant and dry mergers are unlikely to be significant in the buildup of the red sequence over the past 2 Gyr. We compare the colour, morphology, environmental density and degree of activity (BPT class, Baldwin, Phillips & Terlevich) of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid dominated than the comparison sample. We suggest that this may be due to `harassment' in multiple previous passes prior to the current close interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume.

  11. Spectral nuclear properties of NLS1 galaxies

    NASA Astrophysics Data System (ADS)

    Schmidt, E. O.; Ferreiro, D.; Vega Neme, L.; Oio, G. A.

    2016-12-01

    Context. It is not yet well known whether narrow line Seyfert 1 (NLS1) galaxies follow the MBH - σ⋆ relation found for normal galaxies. Emission lines, such as [SII] or [OIII]λ5007, have been used as a surrogate of the stellar velocity dispersion and various results have been obtained. On the other hand, some active galactic nuclei (AGNs) have shown Balmer emission with an additional intermediate component (IC) besides the well-known narrow and broad lines. The properties of this IC have not yet been fully studied. Aims: In order to re-examine the location of NLS1 in the MBH - σ⋆ relation, we test some emission lines, such as the narrow component (NC) of Hα and the forbidden [NII]λλ6548,6584 and [SII]λλ6716,6731 lines, as replacements for σ⋆. On the other hand, we study the properties of the IC of Hα found in 14 galaxies of the sample to find a link between this component, the central engine, and the remaining lines. We also compare the emission among the broad component (BC) of Hα and those emitted at the narrow line region (NLR) to detect differences in the ionizing source in each emitting region. Methods: We have obtained and studied medium-resolution spectra (170 km s-1 FWHM at Hα) of 36 NLS1 galaxies in the optical range 5800-6800 Å. We performed a Gaussian decomposition of the Hα +[NII]λλ6548,6584 profile to study the distinct components of Hα and [NII] lines. We also measured the [SII] lines. Results: We obtained black hole (BH) masses in the range log (MBH/M⊙) = 5.4-7.5 for our sample. We found that, in general, most of the galaxies lie below the MBH - σ⋆ relation when the NC of Hα and [NII] lines are used as a surrogate of σ⋆. The objects are closer to the relation when [SII] lines are used. Nevertheless, the galaxies are still below this relation and we do not see a clear correlation between the BH masses and FWHM[SII]. Besides this, we found that 13 galaxies show an IC, most of which are in the velocity range 700-1500 km s

  12. Void galaxy properties depending on void filament straightness

    NASA Astrophysics Data System (ADS)

    Shim, Junsup; Lee, Jounghun; Hoyle, Fiona

    2015-08-01

    We investigate the properties of galaxies belonging to the filaments in cosmic void regions, using the void catalogue constructed by Pan et al. (2012) from the SDSS DR7. To identify galaxy filaments within a void, voids with 30 or more galaxies are selected as a sample. We identify 3172 filaments in 1055 voids by applying the filament finding algorithm utilizing minimal spanning tree (MST) which is an unique linear pattern into which connects all the galaxies in a void. We study the correlations between galaxy properties and the specific size of filament which quantifies the degree of the filament straightness. For example, the average magnitude and the magnitude of the faintest galaxy in filament decrease as the straightness of the filament increases. We also find that the correlations become stronger in rich filaments with many member galaxies than in poor ones. We discuss a physical explanation to our findings and their cosmological implications.

  13. The Local Tully–Fisher Relation for Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Karachentsev, Igor D.; Kaisina, Elena I.; Kashibadze (Nasonova, Olga G.

    2017-01-01

    We study different incarnations of the Tully–Fisher (TF) relation for the Local Volume (LV) galaxies taken from Updated Nearby Galaxy Catalog. The UNGC sample contains 656 galaxies with W50 H i-line-width estimates, mostly belonging to low-mass dwarfs. Of them, 296 objects have distances measured with accuracies better than 10%. For the sample of 331 LV galaxies having baryonic masses {log}{M}{bar}> 5.8{log} {M}ȯ , we obtain a relation {log}{M}{bar}=2.49{log}{W}50+3.97 with an observed scatter of 0.38 dex. The largest factors affecting the scatter are observational errors in K-band magnitudes and W50 line widths for the tiny dwarfs, as well as uncertainty of their inclinations. We find that accounting for the surface brightness of the LV galaxies or their gas fraction, specific star-formation rate, or isolation index does not essentially reduce the observed scatter on the baryonic TF diagram. We also notice that a sample of 71 dSph satellites of the Milky Way and M31 with a known stellar velocity dispersion σ* tends to follow nearly the same bTF relation, having slightly lower masses than that of late-type dwarfs.

  14. The Reddening law outside the local group galaxies: The case of NGC 7552 and NGC 5236

    NASA Technical Reports Server (NTRS)

    Kinney, Anne L.; Calzetti, Daniela; Bica, Eduardo; Storchi-Bergmann, Thaisa

    1994-01-01

    The dust reddening law from the UV to the near-IR for the extended regions of galaxies is here derived from the spectral distributions of the starburst spiral galaxies NGC 7552 and NGC 5236. The centers of these galaxies have similar absorption and emission line spectra, differing only if the strength of their interstellar lines and in the continuum distribution, with NGC 7552 appearing more reddened than NGC 5236. The disk of NGC 7552 is more inclined, and there is evidence that its center is observed through additional foreground dust and gas clouds, as compared to the center of NGC 5236. While the galaxies can be expected to have similar dust content, they are known to have different dust path lengths to our line of sight. Therefore, differences in the shape of the spectra can be attributed mainly to the effects of dust, allowing us to probe for the first time the properties of the reddening law outside the local group of galaxies. We derive the reddening law based on the optical depth of the emission line of H Alpha and H Beta and also based on the continuum distribtuion. We find that the optical depth from the emission line regions are about twice the optical depth of the continuum regions. Thus, dereddening a starburst galaxy by scaling the Milky Way reddening laws to optical depths obtained from the H Alpha/H Beta line ratio overcompensates for the effect of dust.

  15. Kinematics of the ionized gas in the Local Group irregular galaxy IC 1613

    NASA Astrophysics Data System (ADS)

    Valdez-Gutiérrez, M.; Rosado, M.; Georgiev, L.; Borissova, J.; Kurtev, R.

    2001-01-01

    We present Hα and [S Ii] observations for the Local Group irregular galaxy IC 1613 using the PUMA scanning Fabry-Perot interferometer. Our goal is to analyze the kinematics of the ionized gas in the complex sample of superbubbles located in the whole extension of our field (10\\arcmin ), which includes most of the optical emission of this galaxy, and to study the inter-relationship between young stellar associations and nebulae based on a previous study that we have made on the stellar associations of the central region of this galaxy. The ionized gas in this galaxy is distributed in classical H Ii regions and in a series of superbubbles (also called giant shells) covering a large fraction of the optical extent of the galaxy. We present a catalog of kinematical properties of both the H Ii regions of this galaxy and the superbubbles. We have also compared the kinematics of the ionized gas in H Ii regions to search for possible dynamic differences between neutral and ionized gas.

  16. Local Group Dwarf Galaxies in the LCDM Cosmology: Theory Meets Observations

    NASA Astrophysics Data System (ADS)

    Tollerud, Erik Jon

    2012-05-01

    Dwarf galaxies include some of the most extreme low-luminosity objects in the universe, and provide important windows into a wide variety of processes in galaxy formation and evolution. In this thesis, I describe a series of comparisons between observations of dwarf galaxies and predictions of the ΛCDM concordance cosmology, with a focus on Local Group satellites. I first correct the Milky Way satellite luminosity function for luminosity bias under the assumption of a typical ΛCDM satellite distribution, finding consistency with the observations and a prediction of possibly hundreds of faint Milky Way satellites. I also describe a new technique to connect the luminous properties of these satellites (as well as brighter galaxies) to their expected dark matter halo properties. I further consider the brightest Milky Way satellite, the Large Magellanic cloud (LMC), in a cosmological context by comparing it to similar galaxies in the Sloan Digital Sky Survey (SDSS). This shows that ΛCDM n-body simulations provide a good match to observations of such satellites. I also show that, while LMC-like satellites are not uncommon, the LMC is unusual in how blue it is, especially given that the SDSS satellites are significantly redder than typical galaxies of their size. Finally, I present a large new data for faint satellites of M31, the nearest galaxy similar to the Milky Way, providing a second data point for detailed studies of faint satellite systems. I also shows that its satellites are very similar in their general properties to that of the Milky Way satellites.

  17. Characterising the Dense Molecular Gas in Exceptional Local Galaxies

    NASA Astrophysics Data System (ADS)

    Tunnard, Richard C. A.

    2016-08-01

    The interferometric facilities now coming online (the Atacama Large Millimetre Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA)) and those planned for the coming decade (the Next Generation Very Large Array (ngVLA) and the Square Kilometre Array (SKA)) in the radio to sub-millimetre regimes are opening a window to the molecular gas in high-redshift galaxies. However, our understanding of similar galaxies in the local universe is still far from complete and the data analysis techniques and tools needed to interpret the observations in consistent and comparable ways are yet to be developed. I first describe the Monte Carlo Markov Chain (MCMC) script developed to empower a public radiative transfer code. I characterise both the public code and MCMC script, including an exploration of the effect of observing molecular lines at high redshift where the Cosmic Microwave Background (CMB) can provide a significant background, as well as the effect this can have on well-known local correlations. I present two studies of ultraluminous infrared galaxies (ULIRGs) in the local universe making use of literature and collaborator data. In the first of these, NGC6240, I use the wealth of available data and the geometry of the source to develop a multi-phase, multi-species model, finding evidence for a complex medium of hot diffuse and cold dense gas in pressure equilibrium. Next, I study the prototypical ULIRG Arp 220; an extraordinary galaxy rendered especially interesting by the controversy over the power source of the western of the two merger nuclei and its immense luminosity and dust obscuration. Using traditional grid based methods I explore the molecular gas conditions within the nuclei and find evidence for chemical differentiation between the two nuclei, potentially related to the obscured power source. Finally, I investigate the potential evolution of proto-clusters over cosmic time with sub-millimetre observations of 14 radio galaxies, unexpectedly finding

  18. The Radio Properties of Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Hogan, M. T.

    2014-09-01

    Energetic feedback from the Active Galactic Nucleus (AGN) of the Brightest Cluster Galaxy (BCG) is required to prevent catastrophic cooling of the intra-cluster medium (ICM) in galaxy clusters. Evidence for this is seen through the inflation of cavities in the ICM by AGN-launched, radio-emitting jets, and understanding this process is an active area of research. Radio observations play an integral role in this, as they trace the active stages of the feedback cycle. Understanding the radio properties of BCGs is therefore paramount for understanding both galaxy clusters and AGN feedback processes globally. Within this thesis, the BCGs in a large (>700) sample of X-ray selected clusters are studied. We observe these BCGs with a wide variety of facilities, building a census of their radio properties across a range of frequencies, timescales and angular resolutions. Radio spectral energy distributions (SEDs) are built for over 200 BCGs, and then decomposed into two components; a core, attributable to ongoing nuclear activity, and a non-core, attributable to historical accretion. Both components are not only more common, but also significantly more powerful in cool-core (CC) clusters than non-cool core (NCC) clusters. However, it is the presence of an active core that shows BCGs in CC clusters are constantly `on' - explaining how they regulate their environments over gigayear timescales. We observe 35 currently active BCGs at high (15-353 GHz) radio frequencies, and monitor their variability. Self-absorbed, active components are found to be common at high frequency. Little variability is seen on < year timescales, although longer term variation of ~10% annually over few-decade timescales is observed. Evidence is presented for a hitherto unseen component in BCG spectra that may be attributable to a naked Advection Dominated Accretion Flow (ADAF). The milli-arcsecond scale radio properties of 59 sources are studied, with a large range of morphologies recovered although no

  19. The relationship of active galactic nuclei & quasars with their local galaxy environment

    NASA Astrophysics Data System (ADS)

    Strand, Natalie Erin

    We explore how the local environment is related to properties of active galactic nuclei (AGNs) of various luminosities. Recent simulations and observations are converging on the view that the extreme luminosity of quasars, the brightest of AGNs, is fueled in major mergers of gas-rich galaxies. In such a picture, quasars, the highest luminosity AGNs, are expected to be located in regions with a higher density of galaxies on small scales where mergers are more likely to take place. However, in this picture, the activity observed in low-luminosity AGNs is due to secular processes that are less dependent on the local galaxy density. To test this hypothesis, we compare the local photometric galaxy density on kiloparsec scales around spectroscopic type I and type II quasars to the local density around lower-luminosity spectroscopic type I and type II AGNs. To minimize projection effects and evolution in the photometric galaxy sample we use to characterize AGN environments, we place our random control sample at the same redshift as our AGNs and impose a narrow redshift window around both the AGNs and control targets. Our results support these merger models for bright AGN origins. We find that the brightest sources have overdensities that increase on the smallest scales compared to dimmer sources. In addition, we investigate the nature of the quasar and AGN environments themselves and find that the increased overdensity of early-type galaxies in the environments of bright type I sources suggests that they are located in richer cluster environments than dim sources. We measure increased environment overdensity with increased quasar black hole mass, consistent with the well- known M DMH - M BH relationship, and find evidence for quenching in the environments of high accretion efficiency type I quasars.

  20. LOCALIZED STARBURSTS IN DWARF GALAXIES PRODUCED BY THE IMPACT OF LOW-METALLICITY COSMIC GAS CLOUDS

    SciTech Connect

    Sánchez Almeida, J.; Muñoz-Tuñón, C.; Filho, M. E.; Elmegreen, B. G.; Elmegreen, D. M.; Pérez-Montero, E.; Vílchez, J. M.; Amorín, R.; Ascasibar, Y.; Papaderos, P.

    2015-09-10

    Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver of star formation over cosmic history. Except in very dense environments where galaxy mergers are also important, model galaxies feed from cold streams of gas from the web that penetrate their dark matter halos. Although these predictions are unambiguous, the observational support has been indirect so far. Here, we report spectroscopic evidence for this process in extremely metal-poor galaxies (XMPs) of the local universe, taking the form of localized starbursts associated with gas having low metallicity. Detailed abundance analyses based on Gran Telescopio Canarias optical spectra of 10 XMPs show that the galaxy hosts have metallicities around 60% solar, on average, while the large star-forming regions that dominate their integrated light have low metallicities of some 6% solar. Because gas mixes azimuthally in a rotation timescale (a few hundred Myr), the observed metallicity inhomogeneities are only possible if the metal-poor gas fell onto the disk recently. We analyze several possibilities for the origin of the metal-poor gas, favoring the metal-poor gas infall predicted by numerical models. If this interpretation is correct, XMPs trace the cosmic web gas in their surroundings, making them probes to examine its properties.

  1. Ultracompact Blue Dwarfs: Galaxy Formation in the Local Universe?

    NASA Astrophysics Data System (ADS)

    Corbin, Michael

    2004-07-01

    Recent observations suggest that very low-mass galaxies in the local universe are still in the process of formation. To investigate this issue we propose to obtain deep ACS HRC images in the U, V and I bands of a sample of 11 "ultracompact" blue dwarf galaxies {UCBDs} identified in the Sloan Digital Sky Survey. These objects are nearby {z < 0.009}, actively star-forming, and have extremely small angular and physical sizes {d < 6" and D < 1 kpc}. They also tend to reside in voids. Our WFPC2 images of the prototype object of this class, POX 186, reveal this tiny object to have a highly disturbed morphlogy indicative of a recent {within 10^8 yr} collision between two small { 100 pc} clumps of stars that could represent the long-sought building blocks predicted by the Press-Schechter model of hierarchical galaxy formation. This collision has also triggered the formation of a "super" star cluster {SSC} at the object's core that may be the progenitor of a globular cluster. POX 186 thus appears to be a very small dwarf galaxy in the process of formation. This exciting discovery strongly motivates HST imaging of a full sample of UCBDs in order to determine if they have morphologies similar to POX 186. HST images are essential for resolving the structure of these objects, including establishing the presence of SSCs. HST also offers the only way to determine their morphologies in the near UV. The spectra of the objects available from the SDSS will also allow us to measure their star formation rates, dust content and metallicities. In addition to potentially providing the first direct evidence of Press-Schechter building blocks, these data could yield insight into the relationship between galaxy and globular cluster formation, and will serve as a test of the recent "downsizing" model of galaxy formation in which the least massive objects are the last to form.

  2. Neutral Gas Outside the Disks of Local Group Galaxies

    NASA Astrophysics Data System (ADS)

    Lockman, Felix J.

    2017-03-01

    Of the three kinds of neutral gas found outside the stellar disks of Local Group galaxies, only the products of interaction, like the Magellanic Stream, have a clearly understandable origin. Both the high-velocity clouds and the faint H I between M31 and M33 remain a mystery. New observations of the region between M31 and M33 with the Green Bank Telescope show that the H I there resides in clouds with a size and mass similar to that of dwarf galaxies, but without stars. These clouds might be products of an interaction, or condensations in the hot circumgalactic medium of M31, but both these models have difficulties. The prevalence of clouds like this in the Local Group remains to be determined.

  3. The Galaxy in Context: Structural, Kinematic, and Integrated Properties

    NASA Astrophysics Data System (ADS)

    Bland-Hawthorn, Joss; Gerhard, Ortwin

    2016-09-01

    Our Galaxy, the Milky Way, is a benchmark for understanding disk galaxies. It is the only galaxy whose formation history can be studied using the full distribution of stars from faint dwarfs to supergiants. The oldest components provide us with unique insight into how galaxies form and evolve over billions of years. The Galaxy is a luminous (L⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. Based on global properties, it falls in the sparsely populated “green valley” region of the galaxy color-magnitude diagram. Here we review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress. Galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.

  4. Environmental impacts on dust temperature of star-forming galaxies in the local Universe

    NASA Astrophysics Data System (ADS)

    Matsuki, Yasuhiro; Koyama, Yusei; Nakagawa, Takao; Takita, Satoshi

    2017-04-01

    We present infrared views of the environmental effects on the dust properties in star-forming (SF) galaxies at z ∼ 0, using the AKARI Far-Infrared Surveyor all-sky map and the large spectroscopic galaxy sample from Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We restrict the sample to those within the redshift range of 0.05 < z < 0.07 and the stellar mass range of 9.2 < log 10(M*/M⊙). We select SF galaxies based on their Hα equivalent width (EWHα > 4 Å) and emission line flux ratios. We perform far-infrared (FIR) stacking analyses by splitting the SDSS SF galaxy sample according to their stellar mass, specific star formation rate (SSFRSDSS), and environment. We derive total infrared luminosity (LIR) for each subsample using the average flux densities at WIDE-S (90 μm) and WIDE-L (140 μm) bands, and then compute infrared (IR)-based SFR (SFRIR) from LIR. We find a mild decrease of IR-based SSFR (SSFRIR) amongst SF galaxies with increasing local density (∼0.1-dex level at maximum), which suggests that environmental effects do not instantly shut down the SF activity in galaxies. We also derive average dust temperature (Tdust) using the flux densities at 90 and 140 μm bands. We confirm a strong positive correlation between Tdust and SSFRIR, consistent with recent studies. The most important finding of this study is that we find a marginal trend that Tdust increases with increasing environmental galaxy density. Although the environmental trend is much milder than the SSFR-Tdust correlation, our results suggest that the environmental density may affect the dust temperature in SF galaxies, and that the physical mechanism which is responsible for this phenomenon is not necessarily specific to cluster environments because the environmental dependence of Tdust holds down to relatively low-density environments.

  5. Alignment of galaxies relative to their local environment in SDSS-DR8

    NASA Astrophysics Data System (ADS)

    Hirv, A.; Pelt, J.; Saar, E.; Tago, E.; Tamm, A.; Tempel, E.; Einasto, M.

    2017-02-01

    Aims: We study the alignment of galaxies relative to their local environment in SDSS-DR8 and, using these data, we discuss evolution scenarios for different types of galaxies. Methods: We defined a vector field of the direction of anisotropy of the local environment of galaxies. We summed the unit direction vectors of all close neighbours of a given galaxy in a particular way to estimate this field. We found the alignment angles between the spin axes of disc galaxies, or the minor axes of elliptical galaxies, and the direction of anisotropy. The distributions of cosines of these angles are compared to the random distributions to analyse the alignment of galaxies. Results: Sab galaxies show perpendicular alignment relative to the direction of anisotropy in a sparse environment, for single galaxies and galaxies of low luminosity. Most of the parallel alignment of Scd galaxies comes from dense regions, from 2...3 member groups and from galaxies with low luminosity. The perpendicular alignment of S0 galaxies does not depend strongly on environmental density nor luminosity; it is detected for single and 2...3 member group galaxies, and for main galaxies of 4...10 member groups. The perpendicular alignment of elliptical galaxies is clearly detected for single galaxies and for members of ≤10 member groups; the alignment increases with environmental density and luminosity. Conclusions: We confirm the existence of fossil tidally induced alignment of Sab galaxies at low z. The alignment of Scd galaxies can be explained via the infall of matter to filaments. S0 galaxies may have encountered relatively massive mergers along the direction of anisotropy. Major mergers along this direction can explain the alignment of elliptical galaxies. Less massive, but repeated mergers are possibly responsible for the formation of elliptical galaxies in sparser areas and for less luminous elliptical galaxies.

  6. Feeding and feedback in radio galaxies of the local universe

    NASA Astrophysics Data System (ADS)

    Couto, Guilherme dos Santos

    2016-10-01

    We present integral field spectroscopic data covering the inner kiloparsecs of four radio galaxies of the local Universe (z<0.07), Arp 102B, Pictor A, 3C 33 and 4C +29.30, obtained with the GMOS-IFU instrument of the Gemini telescopes. We use these data to analyze the gas excitation and kinematics via two-dimensional maps. Using the flux distributions of the emission lines, we identify extended emission in ionized gas up to the edges of the observed field, which corresponds to 1.7 kpc x 2.5 kpc for Arp 102B, 2.5 kpc x 3.4 kpc for Pictor A, 4.0 kpc x 5.8 kpc for 3C 33 and 4.3 kpc x 6.2 kpc for 4C +29.30. The extended line emitting gas displays structures resembling rotating disks, spiral arms and bars. Line ratios indicate that both photons from the nuclear source and shocks originated in the interaction of the radio jet with circumnuclear gas are ionizing mechanisms of the gas. Line ratio values are typical of Seyfert galaxies for 3C 33 and 4C +29.30, while intermediate values between Seyferts and LINERs are observed in Arp 102B. Pictor A galaxy, however, shows low values of [NII]/Ha=0.15-0.25, expected for HII regions. We suggest that these values are observed due to the low gas metallicity (12+log(O/H)=8.39). Centroid velocity maps show that the gas kinematics is dominated by rotation only in Arp 102B and 3C 33. Outflows are observed in the galaxies Arp 102B, 3C 33 and 4C +29.30. We obtain mass outflow rates of 0.32-0.49 Msun per year, but the outflow kinetic power is small, ranging 0.04-0.07% of the AGN bolometric luminosity, indicating that the feedback has little impact in the host galaxies evolution. The high masses of ionized gas, ranging from 7.4E7 to 4.6E8 Msun, and the fact that these galaxies are early-type, suggest an external origin of the gas. Indeed, it is observed evidence of interaction with companion galaxies in Arp 102B, Pictor A and 4C +29.30. We suggest that the capture of mass has triggered the nuclear activity in these galaxies, with the high

  7. VLA HI Imaging of the LARS+eLARS Galaxies: Global HI Properties

    NASA Astrophysics Data System (ADS)

    Eisner, Brian Andrew; Reilly, Bridget; Cannon, John M.; Hayes, Matthew; Melinder, Jens; Östlin, Göran; Pardy, Stephen; LARS Team

    2017-01-01

    The Lyman Alpha Reference Sample (LARS) and its extension (eLARS) form the most comprehensive effort to date to study the details of Lyman Alpha radiative transfer in galaxies. Direct imaging of Lyman Alpha emission from the Hubble Space Telescope is supplemented by a wealth of multi-wavelength observations designed to probe the complex processes that contribute to the escape or destruction of Lyman Alpha photons as they resonantly scatter in the neutral ISM. The 42 LARS+eLARS galaxies span a range of physical properties, including mass and star formation rate. In this work, we present new VLA D-configuration HI imaging of 32 LARS+eLARS galaxies designed to localize the HI gas and to measure the total HI mass. HI column density images and velocity fields are compared to SDSS imaging. Most galaxies are unresolved at this angular resolution; a companion poster presents imaging of interacting galaxies that are well-resolved.

  8. Automated bar detection in local disk galaxies from the SDSS. The colors of bars

    NASA Astrophysics Data System (ADS)

    Consolandi, G.

    2016-10-01

    This paper describes an automatic isophotal fitting procedure that succeeds, without the support of any visual inspection of either the images or the ellipticity/position-angle radial profiles, to extract a fairly pure sample of barred late-type galaxies (LTGs) among thousands of optical images from the Sloan Digital Sky Survey (SDSS). The procedure relies on previous methods to robustly extract the photometrical properties of a large sample of local SDSS galaxies and is tailored to extract bars on the basis of their well-known peculiarities in their position angle and ellipticity profiles. This procedure was run on a sample of 5853 galaxies in the Coma and Local superclusters. The procedure extracted a color, an ellipticity and a position angle radial profile of the ellipses fitted to the isophotes for each galaxy. Examining the profiles of 922 face-on LTGs (B/A > 0.7) automatically, the procedure found that 36% are barred. The local bar fraction strongly increases with stellar mass. The sample of barred galaxies is used to construct a set of template radial color profiles to test the impact of the barred galaxy population on the average color profiles as previously shown in the literature and to test the bar-quenching scenario. The radial color profile of barred galaxy shows that bars are on average redder than their surrounding disk producing an outside-in gradient toward red in correspondence with their corotation radius. The distribution of the extension of the deprojected length of the bar suggests that bars have strong impact on the gradients of averaged color profiles. The dependence of the profiles on the mass is consistent with the bar-quenching scenario, i.e. more massive barred galaxies have redder colors (hence older stellar population and suppressed star formation) inside their corotation radius with respect to their lower mass counterparts. Tables of the barred and non-barred galaxies are only available at the CDS via anonymous ftp to http

  9. CORRELATIONS AMONG GALAXY PROPERTIES FROM THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Li Zhongmu; Mao Caiyan

    2013-07-01

    Galaxies are complex systems with many properties. Correlations among galaxy properties can supply important clues for studying the formation and evolution of galaxies. Using principal component analysis and least-squares fitting, this paper investigates the correlations among galactic parameters involving more properties (color, morphology, stellar population, and absolute magnitude) than previous studies. We use a volume-limited sample (whole sample) of 75,423 galaxies that was selected from the Sloan Digital Sky Survey Data Release 2 and divided into two subsamples (blue and red samples) using a critical color of (g - r) = 0.70 mag. In addition to recovering some previous results, we also obtain some new results. First, all separators for dividing galaxies into two groups can be related via good parameter-first principal component (PC1) correlations. A critical PC1 that indicates whether or not stellar age (or the evolution of a stellar population over time) is important can be used to separate galaxies. This suggests that a statistical parameter, PC1, is helpful in understanding the physical separators of galaxies. In addition, stellar age is shown to be unimportant for red galaxies, while both stellar age and mass are dominating parameters of blue galaxies. This suggests that the various numbers of dominating parameters of galaxies may result from the use of different samples. Finally, some parameters are shown to be correlated, and quantitative fits for a few correlations are obtained, e.g., log(t) = 8.57 + 1.65 (g - r) for the age (log t) and color (g - r) of blue galaxies and log (M{sub *}) = 4.31 - 0.30 M{sub r} for the stellar mass (log M{sub *}) and absolute magnitude (M{sub r}) of red galaxies. The median relationships between various parameter pairs are also presented for comparison.

  10. Dwarfs and Giants in the local flows of galaxies.

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Emelyanov, N. V.; Karachentsev, I. D.

    We use recent Hubble Space Telescope data on nearby dwarf and giant galaxies to study the dynamical structure and evolutionary trends of the local expansion flows of galaxies. It is found that antigravity of dark energy dominates the force field of the flows and makes them expand with acceleration. It also cools the flows and introduces to them the nearly linear velocity-distance relation with the time-rate close to the global Hubble's factor. There are grounds to expect that this is the universal physical regularity that is common not only for the nearby flows we studied here, but also for all the expansion flows of various spatial scales from the 1 Mpc scale and up to the scale of the global cosmological expansion.

  11. Shocked Outflows and Gas Disks in Local Merging Galaxies

    NASA Astrophysics Data System (ADS)

    Soto, Kurt; Martin, C. L.; Prescott, M. K. M.; Armus, L.

    2012-01-01

    We have mapped the kinematic and physical properties of gas emitting optical emission lines across 39 gas-rich mergers, which were previously shown to host tidally-induced gas inflows, with deep ESI spectroscopy. In our unique analysis of these longslit spectra, we fitted multiple kinematic components to forbidden lines and recombination lines simultaneously, enabling an examination of the excitation mechanism in different kinematic components. We identify many rotating gas disks in systems whose stellar component is no longer a disk due to the merger. Many of these disks present gas excited by hot stars, but some of the disks present shock-like ratios of diagnostic emission lines, an observation we attribute to the collision of the two galaxies. In another subset of galaxies, we find very broad (sigma > 150 km/s) emission components that also present shock-like emission-line ratios. The large spatial extent of this emission favors shocks over the narrow-line region of a hidden AGN as the excitation mechanism. The high star formation rate, high dust content, and blueshift of the broad emission further suggest an origin in a galactic outflow. If this interpretation is correct, then our study of these nearby galaxies provides important insight for interpreting the broad emission lines associated with giant star-forming clumps in z 2 galaxies. It also shows that galactic outflows can be recognized via resolved emission lines, in addition to absorption lines, even in integrated spectra; and this technique could prove very powerful for studying galactic outflows in infrared spectra of high-redshift galaxies in the future. This work was supported by the National Science Foundation under contract 0808161.

  12. The black hole mass function derived from local spiral galaxies

    SciTech Connect

    Davis, Benjamin L.; Berrier, Joel C.; Shields, Douglas W.; Kennefick, Daniel; Kennefick, Julia; Seigar, Marc S.; Lacy, Claud H. S.; Hartley, Matthew T.

    2014-07-10

    We present our determination of the nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the local universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern (δ < 0°) hemisphere. Our SMBH mass function agrees well at the high-mass end with previous values given in the literature. At the low-mass end, inconsistencies exist in previous works that still need to be resolved, but our work is more in line with expectations based on modeling of black hole evolution. This low-mass end of the spectrum is critical to our understanding of the mass function and evolution of black holes since the epoch of maximum quasar activity. The sample is defined by a limiting luminosity (redshift-independent) distance, D{sub L} = 25.4 Mpc (z = 0.00572) and a limiting absolute B-band magnitude, M{sub B}=−19.12. These limits define a sample of 140 spiral galaxies, with 128 measurable pitch angles to establish the pitch angle distribution for this sample. This pitch-angle distribution function may be useful in the study of the morphology of late-type galaxies. We then use an established relationship between the logarithmic spiral arm pitch angle and the mass of the central SMBH in a host galaxy in order to estimate the mass of the 128 respective SMBHs in this volume-limited sample. This result effectively gives us the distribution of mass for SMBHs residing in spiral galaxies over a lookback time, t{sub L} ≤ 82.1 h{sub 67.77}{sup −1} Myr and contained within a comoving volume, V{sub C} = 3.37 × 10{sup 4} h{sub 67.77}{sup −3} Mpc{sup 3}. We estimate that the density of SMBHs residing in spiral galaxies in the local universe is ρ=5.54{sub −2.73}{sup +6.55} × 10{sup 4} h{sub 67.77}{sup 3} M{sub ☉} Mpc{sup –3}. Thus, our derived cosmological SMBH mass density for spiral galaxies is Ω{sub BH}=4.35{sub −2.15}{sup +5.14} × 10{sup –7} h{sub 67.77}. Assuming that

  13. Properties of an H I-selected galaxy sample

    NASA Technical Reports Server (NTRS)

    Szomoru, Arpad; Guhathakurta, Puragra; Van Gorkom, Jacqueline H.; Knapen, Johan H.; Weinberg, David H.; Fruchter, Andrew S.

    1994-01-01

    We analyze the properties of a sample of galaxies identified in a 21cm, H I-line survey of selected areas in the Perseus-Pisces supercluster and its foreground void. Twelve fields were observed in the supercluster, five of them (target fields) centered on optically bright galaxies, and the other seven (blank fields) selected to contain no bright galaxies within 45 min. of their centers. We detected nine previously uncatalogued, gas-rich galaxies, six of them in the target fields. We also detected H I from seven previously catalogued galaxies in these fields. Observations in the void covered the same volume as the 12 supercluster fields at the same H I-mass sensitivity, but no objects were detected. Combining out H I data with optical broadband and H alpha imaging, we conclude that the properties of H I-selected galaxies do not differ substantially from those of late-type galaxies found in optical surveys. In particular, the galaxies in our sample do not appear to be unusually faint for their H I mass, or for their circular velocity. We find tentative evidence for a connection between optical surface brightness and degree of isolation, in the sense that low surface brightness galaxies tend to be more isolated. The previously catalogued, optically bright galaxies in our survey volume dominate the total H I mass density and cross section; the uncatalogued galaxies contribute only approximately 19 percent of the mass and approximately 12 percent of the cross section. Thus, existing estimates of the density and cross section of neutral hydrogen, most of which are based on optically selected galaxy samples, are probably accurate. Such estimates can be used to compare the nearby universe to the high-redshift universe probed by quasar absorption lines.

  14. AGN multi-wavelength identification and host galaxy properties

    NASA Astrophysics Data System (ADS)

    Azadi, Mojegan; Coil, Alison L.; MOSDEF Team; PRIMUS Team

    2017-01-01

    I present results on AGN identification, selection biases, and host galaxy properties at z~2.3 and results on the relation between AGN accretion and star formation activity at z~0.8. In the MOSDEF survey, with a sample of X-ray, IR, and optically selected AGN at z~2.3, using rest-frame optical spectra obtained with the Keck/MOSFIRE instrument, I find clear selection biases in identifying AGN at these wavelengths. There is a strong bias against identifying AGN at any wavelength in low mass galaxies, and an additional bias against identifying IR AGN in the most massive galaxies. While AGN hosts span a wide range of SFR, IR AGN are mainly in less dusty galaxies with relatively higher SFR and optical AGN are in dusty galaxies with relatively lower SFR in our sample. X-ray AGN selection does not display a bias with host SFR. I also consider the relation between the growth of galaxies and their SMBHs using a large sample of X-ray AGN in the PRIMUS survey. I do not find a significant correlation between SFR and AGN instantaneous luminosity. However, I find a weak but significant correlation between the average luminosity of AGN and SFR, which likely reflects that AGN luminosities vary on shorter timescales than host galaxies SFR. My results indicate that AGN are also often hosted by quiescent galaxies, and within both the star-forming and quiescent galaxy populations the probability of hosting an AGN is a power-law distribution as a function of specific accretion rate. However, at a given stellar mass, I find that a star-forming galaxy is ~2-3 times more likely than a quiescent galaxy to host an AGN of a given specific accretion rate. The probability of a galaxy hosting an AGN is constant across the main sequence of star formation, while in quiescent galaxies increases with SFR.

  15. Morphological properties of isolated galaxies vs. isolation criteria

    NASA Astrophysics Data System (ADS)

    Vavilova, I. B.; Melnyk, O. V.; Elyiv, A. A.

    2009-12-01

    We studied the morphological properties of isolated galaxies samples in dependence on the isolation parameter and properties of primary catalogs. With this aim we identified the samples of single and isolated galaxies from SDSS DR5 (Single and QIsol) with the 3D Voronoi tessellation method (Elyiv et al. 2009). We found that in comparison with other samples of isolated galaxies, the QIsol sample contains an excess of late-type galaxies, especially with a low luminosity and BCG/Im/Irr morphology. We also showed that the fractions of early type galaxies in QIsol SDSS DR5 sample and samples 2MIG (Karachentseva et al. 2010) and CIG (Karachentseva et al. 1973; Hernandez-Toledo et al. 2008) are in a good agreement (16-19 %), but Allam's (Allam et al. 2005) and Prada's (Prada et al. 2003) SDSS DR1 samples show a higher excess of the early type galaxies that can be explained by the selection criteria and morphology definition method. We found a weak relation between isolation parameter and color index for the Single sample that may indicate that even in the low dense environment the morphology density relation is observed. We conclude that morphological properties of the resulting sample of isolated galaxies are highly dependent on the primary catalogue from which the galaxies were selected. Moreover, the selection criterion is also important but plays a secondary role in the resulting morphological content, color indices distribution and other parameters of the isolated galaxy samples. Only four galaxies are common in the 2MIG, QIsol, and CIG samples, namely UGC5184, UGC6121, UGC8495, and UGC9598, that allows to consider them as really most isolated galaxies.

  16. Observational properties of compact groups of galaxies

    NASA Technical Reports Server (NTRS)

    Hickson, Paul

    1990-01-01

    Compact groups are small, relatively isolated, systems of galaxies with projected separations comparable to the diameters of the galaxies themselves. Two well-known examples are Stephan's Quintet (Stephan, 1877) and Seyfert's Sextet (Seyfert 1948a,b). In groups such as these, the apparent space density of galaxies approaches 10(exp 6) Mpc(sub -3), denser even than the cores of rich clusters. The apparent unlikeliness of the chance occurrence of such tight groupings lead Ambartsumyan (1958, 1975) to conclude that compact groups must be physically dense systems. This view is supported by clear signs of galaxy interactions that are seen in many groups. Spectroscopic observations reveal that typical relative velocities of galaxies in the groups are comparable to their internal stellar velocities. This should be conducive to strong gravitational interactions - more so than in rich clusters, where galaxy velocities are typically much higher. This suggests that compact groups could be excellent laboratories in which to study galaxy interactions and their effects. Compact groups often contain one or more galaxies whose redshift differs greatly from those of the other group members. If these galaxies are at the same distance as the other members, either entire galaxies are being ejected at high velocities from these groups, or some new physical phenomena must be occurring. If their redshifts are cosmological, we must explain why so many discordant galaxies are found in compact groups. In recent years much progress has been made in addressing these questions. Here, the author discusses the current observational data on compact groups and their implications.

  17. Disk Galaxies in the Outer Local Supercluster: Optical CCD Surface Photometry and Distribution of Galaxy Disk Parameter

    NASA Technical Reports Server (NTRS)

    Lu, N. Y.

    1998-01-01

    We report new B-band CCD surface photometry on a sample of 76 disk galaxies brighter than BT = 14.5 mag in the Uppsala General Catalogue of Galaxies, which are confined within a volume located in the outer part of the Local Supercluster.

  18. Properties of Isolated Galaxies in the SDSS DR2

    NASA Astrophysics Data System (ADS)

    Tucker, D. L.; Allam, S. S.; SDSS Collaboration

    2004-05-01

    We analyze the properties of a sample of ˜4,500 isolated galaxies selected from the SDSS DR2 photometric data following well defined criteria (Tucker & Allam 2003). The results are briefly discussed.

  19. Probing the Histories of Local Group Dwarf Galaxies with Pulsating Variable Stars

    NASA Astrophysics Data System (ADS)

    Ordoñez, Antonio J.; Sarajedini, Ata

    2017-01-01

    I have identified and characterized the Cepheid and RR Lyrae variables in several Local Group dwarf galaxies using archival Hubble Space Telescope imaging. Template light curve fitting routines have been applied to the observations in order to accurately characterize the properties of these variable stars. The pulsation properties of these stars help to constrain their masses and ages, which in turn shed light on the evolution of their respective host systems. I will summarize what this work has yielded in the context of dwarf galaxy evolution and the accretion history of the Milky Way halo. I will also discuss simulated observations on artificial light curves which we have used to characterize different observing strategies and analysis techniques for studies of pulsating variable stars.

  20. Stellar and Gaseous Properties of Tidal Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Duc, P.-A.; Mirabel, I. F.; Brinks, E.

    Small galaxies may form as a result of interactions between galaxies. This idea is consistent with a number of observations of the outer regions of interacting systems: optical condensations, as luminous as dwarf galaxies, are often found at the end of tidal tails. We will present multi--wavelength observations of a few systems and highlight the existence of a new class of objects, which have been named ``tidal dwarf galaxies'', that are made of material pulled out from colliding galaxies. They are gas--rich, associated with massive HI clouds and, like traditional dwarf irregular and blue compact dwarf galaxies, they host active star formation regions. However, they have a high metallicity for their mass. This is the very result of their peculiar mode of formation which is based on cosmic recycling. Part of their stellar populations consists of young stars formed from the collapse in the intergalactic medium of tidally expelled HI clouds, while another fraction is composed of old stars pulled out from the disks of the parent galaxies. We have found for the first time evidence that some tidal dwarfs might already be gravitationally bound and therefore have become independent galaxies. Systematic studies of the properties of dwarf galaxies in different environments are underway in order to estimate the fraction of recycled objects among them.

  1. The Star Formation Properties of Void Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Moorman, Crystal; Vogeley, Michael S.

    2016-01-01

    We measure the star formation properties of two large samples of galaxies from the SDSS in large-scale cosmic voids on time scales of 10 Myr and 100 Myr, using Ha emission line strengths and GALEX FUV fluxes, respectively. The first sample consists of 109,818 optically selected galaxies. We find that void galaxies in this sample have higher specific star formation rates (SSFRs; star formation rates per unit stellar mass) than similar stellar mass galaxies in denser regions. The second sample is a subset of the optically selected sample containing 8070 galaxies with reliable S/N HI detections from ALFALFA. For the HI detected sample, SSFRs are similar regardless of large-scale environment. Investigating only the HI detected dwarf galaxies reveals a trend towards higher SSFRs in voids. Furthermore, we estimate the star formation rate per unit HI mass, known as the star formation efficiency (SFE) of a galaxy, as a function of environment. For the overall HI detected population, we notice no environmental dependence. Limiting the sample to dwarf galaxies again reveals a trend towards higher SFEs in voids. These results suggest that void environments provide a nurturing environment for dwarf galaxy evolution.

  2. On the Star Formation Properties of Void Galaxies

    NASA Astrophysics Data System (ADS)

    Moorman, Crystal M.; Moreno, Jackeline; White, Amanda; Vogeley, Michael S.; Hoyle, Fiona; Giovanelli, Riccardo; Haynes, Martha P.

    2016-11-01

    We measure the star formation properties of two large samples of galaxies from the SDSS in large-scale cosmic voids on timescales of 10 and 100 Myr, using Hα emission line strengths and GALEX FUV fluxes, respectively. The first sample consists of 109,818 optically selected galaxies. We find that void galaxies in this sample have higher specific star formation rates (SSFRs; star formation rates per unit stellar mass) than similar stellar mass galaxies in denser regions. The second sample is a subset of the optically selected sample containing 8070 galaxies with reliable H i detections from ALFALFA. For the full H i detected sample, SSFRs do not vary systematically with large-scale environment. However, investigating only the H i detected dwarf galaxies reveals a trend toward higher SSFRs in voids. Furthermore, we estimate the star formation rate per unit H i mass (known as the star formation efficiency; SFE) of a galaxy, as a function of environment. For the overall H i detected population, we notice no environmental dependence. Limiting the sample to dwarf galaxies still does not reveal a statistically significant difference between SFEs in voids versus walls. These results suggest that void environments, on average, provide a nurturing environment for dwarf galaxy evolution allowing for higher specific star formation rates while forming stars with similar efficiencies to those in walls.

  3. Universal Scattering Property of Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Hall, C. R.; Bruhweiler, F. C.; Madejski, G. M.

    1996-12-01

    The dusty torus model of Seyfert galaxies--the so-called Unified Model--(Antonucci & Miller 1985; Antonucci 1993) states that both type 1 and type 2 objects are intrinsically the same and share a similar overall geometry. Depending upon the observer's line of sight to the central engine, the broad lines which define the Seyfert type may be visible (Sy 1) or obscured by the torus (Sy 2), while the narrow lines are equally visible in both classes. In addition the polar regions of the torus contain an electron scattering atmosphere, extending beyond the polar openings. Via Thomson scattering of central engine photons, the broad line feature in Sy 2s can only be detected in polarized light. From an empirical analysis comparing the narrow Balmer H-beta observed in a sample of objects from both classes against the broad Balmer H-beta observed directly in Seyfert 1s, and observed in polarized light in Seyfert 2s, we find a general scattering law: the ratio of the intrinsic luminosity to the polarized luminosity in the line is approximately 300. This has strong implications on the geometry and physical properties of the scattering medium. References: Antonucci, R.R.J. 1993,ARA&A, 31, 473 Antonucci, R.R.J.,& Miller,J.S. 1985,ApJ, 297, 621

  4. THE EFFECT OF ENVIRONMENT ON MILKY-WAY-MASS GALAXIES IN A CONSTRAINED SIMULATION OF THE LOCAL GROUP

    SciTech Connect

    Creasey, Peter; Scannapieco, Cecilia; Nuza, Sebastián E.; Gottlöber, Stefan; Steinmetz, Matthias; Yepes, Gustavo

    2015-02-10

    In this Letter, we present, for the first time, a study of star formation rate (SFR), gas fraction, and galaxy morphology of a constrained simulation of the Milky Way (MW) and Andromeda (M31) galaxies compared to other MW-mass galaxies. By combining with unconstrained simulations, we cover a sufficient volume to compare these galaxies’ environmental densities ranging from the field to that of the Local Group (LG). This is particularly relevant as it has been shown that, quite generally, galaxy properties depend intimately upon their environment, most prominently when galaxies in clusters are compared to those in the field. For galaxies in loose groups such as the LG, however, environmental effects have been less clear. We consider the galaxy’s environmental density in spheres of 1200 kpc (comoving) and find that while environment does not appear to directly affect morphology, there is a positive trend with SFRs. This enhancement in star formation occurs systematically for galaxies in higher density environments, regardless whether they are part of the LG or in filaments. Our simulations suggest that the richer environment at megaparsec scales may help replenish the star-forming gas, allowing higher specific SFRs in galaxies such as the MW.

  5. Local starburst galaxies and their descendants. Statistics from the Sloan Digital Sky Survey

    NASA Technical Reports Server (NTRS)

    Bergvall, Nils; Marquart, Thomas; Way, Michael J.; Blomqvist, Anna; Holst, Emma; Ostlin, Goran; Zackrisson, Erik

    2016-01-01

    Despite strong interest in the starburst phenomenon in extragalactic astronomy, the concept remains ill-defined. Here we use a strict definition of starburst to examine the statistical properties of starburst galaxies in the local universe. We also seek to establish links between starburst galaxies, post-starburst (hereafter postburst) galaxies, and active galaxies. Data were selected from the Sloan Digital Sky Survey DR7. We applied a novel method of treating dust attenuation and derive star formation rates, ages, and stellar masses assuming a two-component stellar population model. Dynamical masses are calculated from the width of the H-alpha line. These masses agree excellently with the photometric masses. The mass (gas+stars) range is approximately 10( exp 9) - 10(exp 11.5) solar mass. As a selection criterion for starburst galaxies, we use, the birthrate parameter, b = SFR/SFR, requiring that b is greater than 3. For postburst galaxies, we use, the equivalent width of Hdelta in absorption with the criterion EW (sub Hdelta_abs) is greater than 6 A. Results. We find that only 1% of star-forming galaxies are starburst galaxies. They contribute 3-6% to the stellar production and are therefore unimportant for the local star formation activity. The median starburst age is 70 Myr roughly independent of mass, indicating that star formation is mainly regulated by local feedback processes. The b-parameter strongly depends on burst age. Values close to b = 60 are found at ages approximately 10 Myr, while almost no starbursts are found at ages greater than 1 Gyr. The median baryonic burst mass fraction of sub-L galaxies is 5% and decreases slowly towards high masses. The median mass fraction of the recent burst in the postburst sample is 5-10%. A smaller fraction of the postburst galaxies, however, originates in non-bursting galaxies. The age-mass distribution of the postburst progenitors (with mass fractions is greater than 3%) is bimodal with a break at logM(solar mass

  6. KINEMATIC CLASSIFICATIONS OF LOCAL INTERACTING GALAXIES: IMPLICATIONS FOR THE MERGER/DISK CLASSIFICATIONS AT HIGH-z

    SciTech Connect

    Hung, Chao-Ling; Larson, Kirsten L.; Sanders, D. B.; Rich, Jeffrey A.; Yuan, Tiantian; Kewley, Lisa J.; Casey, Caitlin M.; Smith, Howard A.; Hayward, Christopher C.

    2015-04-20

    The classification of galaxy mergers and isolated disks is key for understanding the relative importance of galaxy interactions and secular evolution during the assembly of galaxies. Galaxy kinematics as traced by emission lines have been used to suggest the existence of a significant population of high-z star-forming galaxies consistent with isolated rotating disks. However, recent studies have cautioned that post-coalescence mergers may also display disk-like kinematics. To further investigate the robustness of merger/disk classifications based on kinematic properties, we carry out a systematic classification of 24 local (U)LIRGs spanning a range of morphologies: from isolated spiral galaxies, ongoing interacting systems, to fully merged remnants. We artificially redshift the Wide Field Spectrograph observations of these local (U)LIRGs to z = 1.5 to make a realistic comparison with observations at high-z, and also to ensure that all galaxies have the same spatial sampling of ∼900 pc. Using both kinemetry-based and visual classifications, we find that the reliability of kinematic classification shows a strong trend with the interaction stage of galaxies. Mergers with two nuclei and tidal tails have the most distinct kinematics compared to isolated disks, whereas a significant population of the interacting disks and merger remnants are indistinguishable from isolated disks. The high fraction of mergers displaying disk-like kinematics reflects the complexity of the dynamics during galaxy interactions. Additional merger indicators such as morphological properties traced by stars or molecular gas are required to further constrain the merger/disk classifications at high-z.

  7. Neutral Gas Properties of Extremely Isolated Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Ashley, Trisha; Marcum, Pamela M.; Fanelli, Michael N.

    2017-04-01

    We present the results of single-dish atomic hydrogen (H i) observations of six highly isolated early-type galaxies. These objects are a representative subset of galaxies previously studied at optical wavelengths and selected to be separated by at least 2.5 Mpc from companions brighter than M V = ‑16.5 mag. Each galaxy was observed with a single pointing using the NRAO Green Bank Telescope L-band receiver. Five of these systems were strongly detected in H i. These five galaxies exhibit H i profiles with a range of properties: single Gaussian-like peaks, separate double peaks, and double horn-like profiles. The four bluest galaxies (B‑V < 0.54) all contain significant gas with H i masses ranging from 1.1 × 108 to 1.4 × 109.

  8. Dynamical properties of the Integral Sign galaxy.

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Del Olmo, A.

    The galaxy A 0705+7155, called the Integral Sign because of its singular aspect, was spectroscopically examined. Physical conditions of the ISM, rotation curve, mass, morphological type, warps, and the distance of A 0705+7155 are discussed.

  9. BROAD Hβ EMISSION-LINE VARIABILITY IN A SAMPLE OF 102 LOCAL ACTIVE GALAXIES

    SciTech Connect

    Runco, Jordan N.; Cosens, Maren; Bennert, Vardha N.; Scott, Bryan; Komossa, S.; Malkan, Matthew A.; Treu, Tommaso; Lazarova, Mariana S.; Auger, Matthew W.; Park, Daeseong E-mail: mcosens@calpoly.edu E-mail: malkan@astro.ucla.edu E-mail: lazarovam2@unk.edu E-mail: daeseongpark@kasi.re.kr

    2016-04-10

    A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses M{sub BH} > 10{sup 7}M{sub ⊙} was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between M{sub BH} and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate M{sub BH}, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.

  10. Spitzer Local Volume Legacy (LVL) SEDs and physical properties

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Johnson, Benjamin D.; Van Zee, Liese; Lee, Janice C.; Kennicutt, Robert C.; Calzetti, Daniela; Staudaher, Shawn M.; Engelbracht, Charles W.

    2014-11-01

    We present the panchromatic spectral energy distributions (SEDs) of the Local Volume Legacy (LVL) survey which consists of 258 nearby galaxies (D < 11 Mpc). The wavelength coverage spans the ultraviolet to the infrared (1500 Å-24 μm) which is utilized to derive global physical properties (i.e. star formation rate, stellar mass, internal extinction due to dust). With these data, we find colour-colour relationships and correlated trends between observed and physical properties (i.e. optical magnitudes and dust properties, optical colour and specific star formation rate, and ultraviolet-infrared colour and metallicity). The SEDs are binned by different galaxy properties to reveal how each property affects the observed shape of these SEDs. In addition, due to the volume-limited nature of LVL, we utilize the dwarf-dominated galaxy sample to test star formation relationships established with higher mass galaxy samples. We find good agreement with the star-forming `main-sequence' relationship, but find a systematic deviation in the infrared `main sequence' at low luminosities. This deviation is attributed to suppressed polycyclic aromatic hydrocarbon (PAH) formation in low-metallicity environments and/or the destruction of PAHs in more intense radiation fields occurring near a suggested threshold in star formation rates (sSFR) at a value of log(sSFR) ˜ -10.2.

  11. Far-infrared and dust properties of present-day galaxies in the EAGLE simulations

    NASA Astrophysics Data System (ADS)

    Camps, Peter; Trayford, James W.; Baes, Maarten; Theuns, Tom; Schaller, Matthieu; Schaye, Joop

    2016-10-01

    The Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological simulations reproduce the observed galaxy stellar mass function and many galaxy properties. In this work, we study the dust-related properties of present-day EAGLE galaxies through mock observations in the far-infrared and submm wavelength ranges obtained with the 3D dust radiative transfer code SKIRT. To prepare an EAGLE galaxy for radiative transfer processing, we derive a diffuse dust distribution from the gas particles and we re-sample the star-forming gas particles and the youngest star particles into star-forming regions that are assigned dedicated emission templates. We select a set of redshift-zero EAGLE galaxies that matches the K-band luminosity distribution of the galaxies in the Herschel Reference Survey (HRS), a volume-limited sample of about 300 normal galaxies in the Local Universe. We find overall agreement of the EAGLE dust scaling relations with those observed in the HRS, such as the dust-to-stellar mass ratio versus stellar mass and versus NUV-r colour relations. A discrepancy in the f250/f350 versus f350/f500 submm colour-colour relation implies that part of the simulated dust is insufficiently heated, likely because of limitations in our sub-grid model for star-forming regions. We also investigate the effect of adjusting the metal-to-dust ratio and the covering factor of the photodissociation regions surrounding the star-forming cores. We are able to constrain the important dust-related parameters in our method, informing the calculation of dust attenuation for EAGLE galaxies in the UV and optical domain.

  12. Photometric Properties of Face-on Isolated Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bahr, Alexander; Epstein, P.; Durbala, A.

    2011-05-01

    We want to quantify the relative role of nature versus nurture in defining the observed properties of galaxies. In simpler terms we would like to disentangle the ``genetic'’ and the environmental influences in shaping the morphology of galaxies. In order to do that one needs to firstly define a zero-order baseline, i.e., a sample of galaxies that have been minimally perturbed by neighbors in the last few billion years of their existence. Such a sample has been produced and refined in different stages in the context of the AMIGA international project (www.iaa.es/AMIGA.html). The recent catalogue ``The All-Sky Catalog of Isolated Galaxies Selected from 2MASS'’ (Karachentseva, V. E. et al. 2010) allows us to complete and enrich the initial sample constructed within AMIGA with new objects, thus enhancing the statistical relevance of our study. Our focus is to define a subset of isolated disk spiral galaxies. We constrain the sample selection by: 1) orientation, restricting to almost face-on galaxies and 2) availability of good photometric images in SDSS. The goal is to ``dissect'’ (decompose) these galaxies in major components (disk, bulge, bars, etc.) and to study the properties of the components in a statistical context. Having a reasonable representation of all morphological types, we aim to test the bimodality of bulges and bars. We present a progress report of our work.

  13. A Submillimeter Continuum Survey of Local Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

    2016-12-01

    We conduct a 350 μm dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05-0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S 350 μm = 114-650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57-122 K and 22-35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3-34 × 107 M ⊙ and 0.03%-2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.

  14. X-ray properties of normal galaxies

    NASA Technical Reports Server (NTRS)

    Fabbiano, G.

    1993-01-01

    In this paper I will first review briefly the results of the X-ray observations of early-type galaxies with the HEAO 2 (Eisnstein) satellite, published in the past ten years. I will then concentrate on more recent results stemming from a systematic re-analysis of the Einstein galaxy database, and I will also report on some very preliminary ROSAT results. Parts of this talk were given at the ESO Elba meeting on early-type galaxies in May 1992 and therefore there is a considerable overlap between this paper and that in the proceedings of that meeting. Some of this material was also reviewed by Fabbiano and Kim (1992) and Fabbiano (1992b).

  15. 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.

  16. The physical properties of Lyα emitting galaxies: not just primeval galaxies?

    NASA Astrophysics Data System (ADS)

    Pentericci, L.; Grazian, A.; Fontana, A.; Castellano, M.; Giallongo, E.; Salimbeni, S.; Santini, P.

    2009-02-01

    Aims: We have analyzed a sample of Lyman break galaxies from z ~ 3.5 to z ~ 6 selected from the GOODS-S field as B, V, and i-dropouts, and with spectroscopic observations showing that they have the Lyα line in emission. Our main aim is to investigate their physical properties and their dependence on the emission line characteristic and to shed light on the relation between galaxies with Lyα emission and the general LBG population. Methods: The objects were selected from their optical continuum colors and then spectroscopically confirmed by the GOODS collaboration and other campaigns. From the public spectra we derived the main properties of the Lyα emission such as total flux and rest frame EW. We then used complete photometry, from U band to mid-infrared from the GOODS-MUSIC database, and through standard spectro-photometric techniques we derived the physical properties of the galaxies, such as total stellar mass, stellar ages, star formation rates, and dust content. Finally we investigated the relation between emission line and physical properties. Results: Although most galaxies are fit by young stellar populations, a small but non negligible fraction has SEDs that cannot be represented well by young models and require considerably older stellar component, up to ~1 Gyr. There is no apparent relation between age and EW: some of the oldest galaxies have high line EW, and should be also selected in narrow-band surveys. Therefore not all Lyα emitting galaxies are primeval galaxies in the very early stages of formation, as is commonly assumed. We also find a range of stellar populations, with masses from 5 × 108 M_⊙ to 5 × 1010 M_⊙ and SFR from few to 60 M_⊙ yr-1. Although there is no net correlation between mass and EW, we find a significant lack of massive galaxies with high EW, which could be explained if the most massive galaxies were either dustier and/or if they contained more neutral gas than less massive objects. Finally we find that more than

  17. THE ROLE OF MERGER STAGE ON GALAXY RADIO SPECTRA IN LOCAL INFRARED-BRIGHT STARBURST GALAXIES

    SciTech Connect

    Murphy, Eric J.

    2013-11-01

    An investigation of the steep, high-frequency (i.e., ν ∼ 12 GHz) radio spectra among a sample of 31 local infrared-bright starburst galaxies is carried out in light of their Hubble-Space-Telescope-based merger classifications. Radio data covering as many as 10 individual bands allow for spectral indices to be measured over three frequency bins between 0.15 and 32.5 GHz. Sources having the flattest spectral indices measured at ∼2 and 4 GHz, arising from large free-free optical depths among the densest starbursts, appear to be in ongoing through post-stage mergers. The spectral indices measured at higher frequencies (i.e., ∼12 GHz) are steepest for sources associated with ongoing mergers in which their nuclei are distinct, but share a common stellar envelope and/or exhibit tidal tails. These results hold after excluding potential active galactic nuclei based on their low 6.2 μm polycyclic aromatic hydrocarbon equivalent widths. Consequently, the low-, mid-, and high-frequency spectral indices each appear to be sensitive to the exact merger stage. It is additionally shown that ongoing mergers, whose progenitors are still separated and share a common envelope and/or exhibit tidal tails, also exhibit excess radio emission relative to what is expected given the far-infrared/radio correlation, suggesting that there may be a significant amount of radio emission that is not associated with ongoing star formation. The combination of these observations, along with high-resolution radio morphologies, leads to a picture in which the steep high-frequency radio spectral indices and excess radio emission arise from radio continuum bridges and tidal tails that are not associated with star formation, similar to what is observed for so-called 'taffy' galaxies. This scenario may also explain the seemingly low far-infrared/radio ratios measured for many high-z submillimeter galaxies, a number of which are merger-driven starbursts.

  18. OT1_aedge_4: A definitive Herschel study of the most powerful local radio galaxy - Cygnus A

    NASA Astrophysics Data System (ADS)

    Edge, A.

    2010-07-01

    Powerful radio galaxies have played a central role in our understanding of active galaxies over the past five decades. Cygnus-A, the brightest and most nearby FR-II source, has been a "Rosetta Stone" in this study. It appears to have the outward characteristics of a normal radio galaxy but it's proximity allows us to identify the more subtle properties of an obscured quasar. The energy provided by this very active galaxy is sufficient to launch the energetic jets we observe but the transport of the energy to the hotspots is poorly constrained and understood. The growing realisation that AGN directly affect their host galaxy through a direct feedback mechanism throughout the lifetime of the galaxy makes it especially important for the most nearby obscured quasar to be observed with the widest possible spectral coverage. We propose to use Herschel to reveal the heating of the central region and the energetics of the hotspots. We request observations of the atomic cooling lines [OI], [OIII] and [CII] that will allow us to compare the energetics of the ISM in Cygnus A with other local and more distant galaxies.

  19. Dark and luminous properties of low-luminosity spiral galaxies

    NASA Astrophysics Data System (ADS)

    Kogoshvili, N.; Borchkhadze, T.

    2012-08-01

    On the basis of data in our Merged Catalogue of Galaxies (MERCG), for which an online version is now available, we have analysed some properties of spiral galaxies that are members of pairs or small groups of galaxies. Our sample consists of a total of approximately 300 pairs and groups, distributed over the entire sky. In this context, low-luminosity spirals (LLS), here defined as those with an absolute magnitude of MB ≥ -20.6, are of particular interest, since they are thought to harbour dark matter. We find that the mean distance between the two components in LLS/LLS pairs of galaxies is significantly smaller than in LLS/elliptical (E), LLS/high-luminosity spiral (HLS) and HLS/HLS pairs, as well as in groups with at least one LLS. Moreover, LLS from this sample in the mean have larger central surface densities μo and smaller values of the full angular momentum K than HLS. In the second part, we investigate the relative frequencies of LLS galaxies, single as well as in pairs/groups. We find that they are 4-5 times more frequent inside and around three major clusters of galaxies (Virgo, Pegasus I and Perseus) than in the general field. Our findings all support the assumption that LLS galaxies are indeed carriers of dark matter.

  20. KPNO 0.9m H(alpha) Imaging Survey of ``Transforming Galaxies'' in Local Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Haines, Christopher; O'Sullivan, Ewan; Raychaudhury, Somak; Egami, Eiichi; Campusano, Luis

    2012-08-01

    We propose to use the KPNO 0.9-m telescope to obtain panoramic H(alpha) imaging of ~135 galaxies in ten nearby galaxy groups (60- 80 Mpc) from the Complete Local-Volume Groups Sample (CLoGS). In rich clusters ram-pressure stripping has been shown to be very effective at removing the gas contents and quenching star formation in infalling spiral galaxies. It is much less clear how galaxies are affected by the much lower ram pressures found in galaxy groups, or if other environmental processes begin to dominate. Given that >50% of galaxies in the local volume reside in groups, it is vital that we gain new insights into which mechanisms drive the SFR-density relation in groups. The proposed H(alpha) imaging will allow us to resolve where star-formation is occurring in each galaxy. This can effectively discriminate between ram-pressure stripping characterized by truncated H(alpha) disks, the much gentler starvation mechanism which produces anemic spirals, and nuclear starbursts triggered by low-velocity encounters and mergers which should be most frequent in groups.

  1. KPNO 0.9m H(alpha) Imaging Survey of ``Transforming Galaxies" in Local Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Haines, Christopher; O'Sullivan, Ewan; Raychaudhury, Somak; Gargiulo, Adriana; Campusano, Luis

    2012-02-01

    We propose to use the KPNO 0.9-m telescope to obtain panoramic H(alpha) imaging of ~200 galaxies in two nearby (32, 35 Mpc) galaxy groups NGC 4261 and NGC 5353 from the CLoGS local group survey. In rich clusters ram-pressure stripping has been shown to be very effective at removing the gas contents and quenching star formation in infalling spiral galaxies. It is much less clear how galaxies are affected by the much lower ram pressures found in galaxy groups, or if other environmental processes begin to dominate. Given that >50% of galaxies in the local volume reside in groups, it is vital we gain new insights into which mechanisms drive the SFR-density relation in groups. The proposed H(alpha) imaging will allow us to resolve where star-formation is occuring in each galaxy. This can effectively discriminate between ram-pressure stripping characterized by truncated H(alpha) disks, the much gentler starvation mechanism which produces anemic spirals, and nuclear star-bursts triggered by low-velocity encounters which should be most frequent in groups.

  2. Multicolor Photometry of the Merging Galaxy Cluster A2319: Dynamics and Star Formation Properties

    NASA Astrophysics Data System (ADS)

    Yan, Peng-Fei; Yuan, Qi-Rong; Zhang, Li; Zhou, Xu

    2014-05-01

    Asymmetric X-ray emission and a powerful cluster-scale radio halo indicate that A2319 is a merging cluster of galaxies. This paper presents our multicolor photometry for A2319 with 15 optical intermediate filters in the Beijing-Arizona-Taiwan-Connecticut (BATC) system. There are 142 galaxies with known spectroscopic redshifts within the viewing field of 58' × 58' centered on this rich cluster, including 128 member galaxies (called sample I). A large velocity dispersion in the rest frame, 1622^{+91}_{-70} km s-1, suggests merger dynamics in A2319. The contour map of projected density and localized velocity structure confirm the so-called A2319B substructure, at ~10' northwest to the main concentration A2319A. The spectral energy distributions (SEDs) of more than 30,000 sources are obtained in our BATC photometry down to V ~ 20 mag. A u-band (~3551 Å) image with better seeing and spatial resolution, obtained with the Bok 2.3 m telescope at Kitt Peak, is taken to make star-galaxy separation and distinguish the overlapping contamination in the BATC aperture photometry. With color-color diagrams and photometric redshift technique, 233 galaxies brighter than h BATC = 19.0 are newly selected as member candidates after an exclusion of false candidates with contaminated BATC SEDs by eyeball-checking the u-band Bok image. The early-type galaxies are found to follow a tight color-magnitude correlation. Based on sample I and the enlarged sample of member galaxies (called sample II), subcluster A2319B is confirmed. The star formation properties of cluster galaxies are derived with the evolutionary synthesis model, PEGASE, assuming a Salpeter initial mass function and an exponentially decreasing star formation rate (SFR). A strong environmental effect on star formation histories is found in the manner that galaxies in the sparse regions have various star formation histories, while galaxies in the dense regions are found to have shorter SFR time scales, older stellar ages, and

  3. Multicolor photometry of the merging galaxy cluster A2319: Dynamics and star formation properties

    SciTech Connect

    Yan, Peng-Fei; Yuan, Qi-Rong; Zhang, Li; Zhou, Xu E-mail: yuanqirong@njnu.edu.cn

    2014-05-01

    Asymmetric X-ray emission and a powerful cluster-scale radio halo indicate that A2319 is a merging cluster of galaxies. This paper presents our multicolor photometry for A2319 with 15 optical intermediate filters in the Beijing-Arizona-Taiwan-Connecticut (BATC) system. There are 142 galaxies with known spectroscopic redshifts within the viewing field of 58' × 58' centered on this rich cluster, including 128 member galaxies (called sample I). A large velocity dispersion in the rest frame, 1622{sub −70}{sup +91} km s{sup –1}, suggests merger dynamics in A2319. The contour map of projected density and localized velocity structure confirm the so-called A2319B substructure, at ∼10' northwest to the main concentration A2319A. The spectral energy distributions (SEDs) of more than 30,000 sources are obtained in our BATC photometry down to V ∼ 20 mag. A u-band (∼3551 Å) image with better seeing and spatial resolution, obtained with the Bok 2.3 m telescope at Kitt Peak, is taken to make star-galaxy separation and distinguish the overlapping contamination in the BATC aperture photometry. With color-color diagrams and photometric redshift technique, 233 galaxies brighter than h {sub BATC} = 19.0 are newly selected as member candidates after an exclusion of false candidates with contaminated BATC SEDs by eyeball-checking the u-band Bok image. The early-type galaxies are found to follow a tight color-magnitude correlation. Based on sample I and the enlarged sample of member galaxies (called sample II), subcluster A2319B is confirmed. The star formation properties of cluster galaxies are derived with the evolutionary synthesis model, PEGASE, assuming a Salpeter initial mass function and an exponentially decreasing star formation rate (SFR). A strong environmental effect on star formation histories is found in the manner that galaxies in the sparse regions have various star formation histories, while galaxies in the dense regions are found to have shorter SFR time

  4. The 2dF galaxy redshift survey: clustering properties of radio galaxies

    NASA Astrophysics Data System (ADS)

    Magliocchetti, Manuela; Maddox, Steve J.; Hawkins, Ed; Peacock, John A.; Bland-Hawthorn, Joss; Bridges, Terry; Cannon, Russell; Cole, Shaun; Colless, Matthew; Collins, Chris; Couch, Warrick; Dalton, Gavin; de Propris, Roberto; Driver, Simon P.; Efstathiou, George; Ellis, Richard S.; Frenk, Carlos S.; Glazebrook, Karl; Jackson, Carole A.; Jones, Bryn; Lahav, Ofer; Lewis, Ian; Lumsden, Stuart; Norberg, Peder; Peterson, Bruce A.; Sutherland, Will; Taylor, Keith; 2dFGRS Team

    2004-06-01

    The clustering properties of local, S1.4 GHz>= 1 mJy, radio sources are investigated for a sample of 820 objects drawn from the joint use of the Faint Images of the Radio Sky at 20 cm (FIRST) and 2dF Galaxy Redshift surveys. To this aim, we present 271 new bJ<= 19.45 spectroscopic counterparts of FIRST radio sources to be added to those already introduced in our previous paper. The two-point correlation function for the local radio population is found to be entirely consistent with estimates obtained for the whole sample of 2dFGRS galaxies. From measurements of the redshift-space correlation function ξ(s) we derive a redshift-space clustering length s0= 10.7+0.8-0.7 Mpc, while from the projected correlation function Ξ(rT) we estimate the parameters of the real-space correlation function ξ(r) = (r/r0)-γ, r0= 6.7+0.9-1.1 Mpc and γ= 1.6 +/- 0.1, where h= 0.7 is assumed. Different results are instead obtained if we only consider sources that present signatures of active galactic nucleus (AGN) activity in their spectra. These objects are shown to be very strongly correlated, with r0= 10.9+1.0-1.2 Mpc and γ= 2 +/- 0.1, a steeper slope than has been claimed in other recent works. No difference is found in the clustering properties of radio-AGNs of different radio luminosity. Comparisons with models for ξ(r) show that AGN-fuelled sources reside in dark matter haloes more massive than ~1013.4 Msolar, higher than the corresponding figure for radio-quiet quasi-stellar objects. This value can be converted into a minimum black hole mass associated with radio-loud, AGN-fuelled objects of MminBH~ 109 Msolar. The above results then suggest - at least for relatively faint radio objects - the existence of a threshold black hole mass associated with the onset of significant radio activity such as that of radio-loud AGNs; however, once the activity is triggered, there appears to be no evidence for a connection between black hole mass and level of radio output.

  5. OmegaWINGS: spectroscopy in the outskirts of local clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Moretti, A.; Gullieuszik, M.; Poggianti, B.; Paccagnella, A.; Couch, W. J.; Vulcani, B.; Bettoni, D.; Fritz, J.; Cava, A.; Fasano, G.; D'Onofrio, M.; Omizzolo, A.

    2017-03-01

    Context. Studies of the properties of low-redshift cluster galaxies suffer, in general, from small spatial coverage of the cluster area. WINGS, the most homogeneous and complete study of galaxies in dense environments to date, obtained spectroscopic redshifts for 48 clusters at a median redshift of 0.05, out to an average distance of approximately 0.5 cluster virial radii. The WINGS photometric survey was recently extended by the VST survey OmegaWINGS to cover the outskirts of a subset of the original cluster sample. Aims: In this work, we present the spectroscopic follow-up of 33 of the 46 clusters of galaxies observed with VST over 1 square degree. The aim of this spectroscopic survey is to enlarge the number of cluster members and study the galaxy characteristics and the cluster dynamical properties out to large radii, reaching the virial radius and beyond. Methods: We used the AAOmega spectrograph at AAT to obtain fiber-integrated spectra covering the wavelength region between 3800 and 9000 Å with a spectral resolution of 3.5-6 Å full width at half maximum (FWHM). Observations were performed using two different configurations and exposure times per cluster. We measured redshifts using both absorption and emission lines and used them to derive the cluster redshifts and velocity dispersions. Results: We present here the redshift measurements for 17 985 galaxies, 7497 of which turned out to be cluster members. The sample magnitude completeness is 80% at V = 20. Thanks to the observing strategy, the radial completeness turned out to be relatively constant (90%) within the AAOmega field of view. The success rate in measuring redshifts is 95%, at all radii. Conclusions: We provide redshifts for the full sample of galaxies in OmegaWINGS clusters together with updated and robust cluster redshift and velocity dispersions. These data, publicly accessible through the CDS and VO archives, will enable evolutionary and environmental studies of cluster properties, providing

  6. THE WHIQII SURVEY: METALLICITIES AND SPECTROSCOPIC PROPERTIES OF LUMINOUS COMPACT BLUE GALAXIES

    SciTech Connect

    Tollerud, Erik J.; Barton, Elizabeth J.; Cooke, Jeff; Van Zee, Liese

    2010-01-10

    As part of the WIYN High Image Quality Indiana-Irvine (WHIQII) survey, we present 123 spectra of faint emission-line galaxies, selected to focus on intermediate redshift (0.4 approx< z approx< 0.8) galaxies with blue colors that appear physically compact on the sky. The sample includes 15 true Luminous Compact Blue Galaxies (LCBGs) and an additional 27 slightly less extreme emission-line systems. These galaxies represent a highly evolving class that may play an important role in the decline of star formation since z approx 1, but their exact nature and evolutionary pathways remain a mystery. Here, we use emission lines to determine metallicities and ionization parameters, constraining their intrinsic properties and state of star formation. Some LCBG metallicities are consistent with a 'bursting dwarf' scenario, while a substantial fraction of others are not, further confirming that LCBGs are a highly heterogeneous population but are broadly consistent with the intermediate redshift field. In agreement with previous studies, we observe overall evolution in the luminosity-metallicity relation at intermediate redshift. Our sample, and particularly the LCBGs, occupies a region in the empirical R{sub 23}-O{sub 32} plane that differs from luminous local galaxies and is more consistent with dwarf irregulars at the present epoch, suggesting that cosmic 'downsizing' is observable in even the most fundamental parameters that describe star formation. These properties for our sample are also generally consistent with lying between local galaxies and those at high redshift, as expected by this scenario. Surprisingly, our sample exhibits no detectable correlation between compactness and metallicity, strongly suggesting that at these epochs of rapid star formation, the morphology of compact star-forming galaxies is largely transient.

  7. Do galaxy global relationships emerge from local ones? The SDSS IV MaNGA surface mass density-metallicity relation

    NASA Astrophysics Data System (ADS)

    Barrera-Ballesteros, Jorge K.; Heckman, Timothy M.; Zhu, Guangtun B.; Zakamska, Nadia L.; Sánchez, Sebastian F.; Law, David; Wake, David; Green, Jenny E.; Bizyaev, Dmitry; Oravetz, Daniel; Simmons, Audrey; Malanushenko, Elena; Pan, Kaike; Roman Lopes, Alexandre; Lane, Richard R.

    2016-12-01

    We present the stellar surface mass density versus gas metallicity (Σ*-Z) relation for more than 500 000 spatially resolved star-forming resolution elements (spaxels) from a sample of 653 disc galaxies included in the SDSS IV MaNGA survey. We find a tight relation between these local properties, with higher metallicities as the surface density increases. This relation extends over three orders of magnitude in the surface mass density and a factor of 4 in metallicity. We show that this local relationship can simultaneously reproduce two well-known properties of disc galaxies: their global mass-metallicity relationship and their radial metallicity gradients. We also find that the Σ*-Z relation is largely independent of the galaxy's total stellar mass and specific star formation rate (sSFR), except at low stellar mass and high sSFR. These results suggest that in the present-day universe local properties play a key role in determining the gas-phase metallicity in typical disc galaxies.

  8. Spectral analysis of the Stromlo-APM Survey - I. Spectral properties of galaxies

    NASA Astrophysics Data System (ADS)

    Tresse, L.; Maddox, S.; Loveday, J.; Singleton, C.

    1999-11-01

    We analyse spectral properties of 1671 galaxies from the Stromlo-APM Survey, selected to have 15<=bJ<=17.15 and having a mean redshift z=0.05. This is a representative local sample of field galaxies, so the global properties of the galaxy population provide a comparative point for analysis of more distant surveys. We measure Hα, [Oii] λ3727, [Sii] λλ6716, 6731, [Nii] λ6583 and [Oi] λ6300 equivalent widths and the D4000 break index. The 5-Å-resolution spectra use an 8-arcsec slit, which typically covers 40-50per cent of the galaxy area. We find no evidence for systematic trends depending on the fraction of galaxy covered by the slit, and further analysis suggests that our spectra are representative of integrated galaxy spectra. We classify spectra according to their Hα emission, which is closely related to massive star formation. Overall we find that 61per cent of galaxies are Hα emitters with rest-frame equivalent widths EW(Hα) >~2Å. The emission-line galaxy (ELG) fraction is smaller than seen in the Canada-France Redshift Survey (CFRS) at z=0.2, and is consistent with a rapid evolution of Hα luminosity density. The ELG fraction and EW(Hα) increase at fainter absolute magnitudes, smaller projected area and smaller D4000. In the local Universe, faint, small galaxies are dominated by star formation activity, while bright, large galaxies are more quiescent. This picture of the local Universe is quite different from that of the distant one; bright galaxies appear to show rapidly increasing activity as one moves further back in time. We find that the ratio [Nii] λ6583/Hα is anticorrelated with EW(Hα), and that the value of 0.5 commonly used to remove the [Nii] contribution from blended Hα+[Nii] λλ6548, 6583 applies only for samples with an EW distribution similar to that seen at low redshift. We show that the [Oii], [Nii], [Sii] and Hα EWs are correlated, but with large dispersions (~50per cent) owing to the diversity of galaxy contents sampled. Our

  9. OBSERVATIONS OF STARBURST GALAXIES WITH FAR-ULTRAVIOLET SPECTROGRAPHIC EXPLORER: GALACTIC FEEDBACK IN THE LOCAL UNIVERSE

    SciTech Connect

    Grimes, J. P.; Heckman, T.; Meurer, G.; Strickland, D.; Aloisi, A.; Leitherer, C.; Sembach, K.; Calzetti, D.; Martin, C. L. E-mail: heckman@pha.jhu.edu E-mail: dks@pha.jhu.edu E-mail: leitherer@stsci.edu E-mail: cmartin@physics.ucsb.edu

    2009-03-15

    quiescent gas, and can only be readily detected in the strongest absorption lines. From direct observations below the Lyman edge in the galaxy rest frame, we find no evidence of Lyman continuum radiation escaping from any of the galaxies in the sample. Moreover, the small escape fraction of light in the center of the strong C II absorption feature confirms the high opacity below the Lyman limit in the neutral ISM. The absolute fraction of escaping Lyman continuum photons is typically <1%. This sample provides a unique window on the global properties of local star-forming galaxies as observed in the far-UV and also provides a useful comparison sample for understanding spectra of high-redshift star-forming galaxies.

  10. KILOPARSEC-SCALE PROPERTIES OF EMISSION-LINE GALAXIES

    SciTech Connect

    Hemmati, Shoubaneh; Miller, Sarah H.; Mobasher, Bahram; Nayyeri, Hooshang; Ferguson, Henry C.; Koekemoer, Anton M.; Guo, Yicheng; Koo, David C.

    2014-12-20

    We perform a detailed study of the resolved properties of emission-line galaxies at kiloparsec scales to investigate how small-scale and global properties of galaxies are related. We use a sample of 119 galaxies in the GOODS fields. The galaxies are selected to cover a wide range in morphologies over the redshift range 0.2 < z < 1.3. High resolution spectroscopic data from Keck/DEIMOS observations are used to fix the redshift of all the galaxies in our sample. Using the HST/ACS and HST/WFC3 imaging data taken as a part of the CANDELS project, for each galaxy, we perform spectral energy distribution fitting per resolution element, producing resolved rest-frame U – V color, stellar mass, star formation rate (SFR), age, and extinction maps. We develop a technique to identify ''regions'' of statistical significance within individual galaxies, using their rest-frame color maps to select red and blue regions, a broader definition for what are called ''clumps'' in other works. As expected, for any given galaxy, the red regions are found to have higher stellar mass surface densities and older ages compared to the blue regions. Furthermore, we quantify the spatial distribution of red and blue regions with respect to both redshift and stellar mass, finding that the stronger concentration of red regions toward the centers of galaxies is not a significant function of either redshift or stellar mass. We find that the ''main sequence'' of star-forming galaxies exists among both red and blue regions inside galaxies, with the median of blue regions forming a tighter relation with a slope of 1.1 ± 0.1 and a scatter of ∼0.2 dex compared to red regions with a slope of 1.3 ± 0.1 and a scatter of ∼0.6 dex. The blue regions show higher specific SFRs (sSFRs) than their red counterparts with the sSFR decreasing since z ∼ 1, driven primarily by the stellar mass surface densities rather than the SFRs at a given resolution element.

  11. Compact Groups of Galaxies with Complete Spectroscopic Redshifts in the Local Universe

    NASA Astrophysics Data System (ADS)

    Sohn, Jubee; Hwang, Ho Seong; Geller, Margaret J.; Diaferio, Antonaldo; Rines, Kenneth J.; Lee, Myung Gyoon; Lee, Gwang-Ho

    2015-12-01

    Dynamical analysis of compact groups provides important tests of models of compact group formation and evolution. By compiling 2066 redshifts from FLWO/FAST, from the literature, and from SDSS DR12 in the fields of compact groups in tet{McC09}, we construct the largest sample of compact groups with complete spectroscopic redshifts in the redshift range 0.01 < z < 0.22. This large redshift sample shows that the interloper fraction in the tet{McC09} compact group candidates is ˜ 42%. A secure sample of 332 compact groups includes 192 groups with four or more member galaxies and 140 groups with three members. The fraction of early-type galaxies in these compact groups is 62%, higher than for the original Hickson compact groups. The velocity dispersions of early- and late-type galaxies in compact groups change little with groupcentric radius; the radii sampled are less than 100 h^{-1} kpc, smaller than the radii typically sampled by members of massive clusters of galaxies. The physical properties of our sample compact groups include size, number density, velocity dispersion, and local environment; these properties slightly differ from those derived for the original Hickson compact groups and for the DPOSS II compact groups. Differences result from subtle differences in the way the group candidates were originally selected. The abundance of the compact groups changes little with redshift over the range covered by this sample. The approximate constancy of the abundance for this sample is a potential constraint on the evolution of compact groups on a few Gigayear timescale.

  12. OPTICAL PROPERTIES OF HOST GALAXIES OF EXTRAGALACTIC NUCLEAR WATER MASERS

    SciTech Connect

    Zhu Guangtun; Zaw, Ingyin; Blanton, Michael R.; Greenhill, Lincoln J.

    2011-12-01

    We study the optical properties of the host galaxies of nuclear 22 GHz ({lambda} = 1.35 cm) water masers. To do so, we cross-match the galaxy sample surveyed for water maser emission (123 detections and 3806 non-detections) with the Sloan Digital Sky Survey (SDSS) low-redshift galaxy sample (z < 0.05). Out of 1636 galaxies with SDSS photometry, we identify 48 detections; out of the 1063 galaxies that also have SDSS spectroscopy, we identify 33 detections. We find that maser detection rate is higher at higher optical luminosity (M{sub B} ), larger velocity dispersion ({sigma}), and higher [O III] {lambda}5007 luminosity, with [O III] {lambda}5007 being the dominant factor. These detection rates are essentially the result of the correlations of isotropic maser luminosity with all three of these variables. These correlations are natural if maser strength increases with central black hole mass and the level of active galactic nucleus (AGN) activity. We also find that the detection rate is higher in galaxies with higher extinction. Based on these results, we propose that maser surveys seeking to efficiently find masers should rank AGN targets by extinction-corrected [O III] {lambda}5007 flux when available. This prioritization would improve maser detection efficiency, from an overall {approx}3% without pre-selection to {approx}16% for the strongest intrinsic [O III] {lambda}5007 emitters, by a factor of {approx}5.

  13. Dust Properties, Star Formation, and Chemical Enrichment of Low Luminosity Galaxies

    NASA Astrophysics Data System (ADS)

    van Zee, Liese; Marble, Andrew; Englebracht, Charles; Skillman, Evan

    2009-08-01

    The recently completed Local Volume Legacy (LVL) survey has yielded multi-wavelength observations from the ultraviolet to the radio for a volume-complete sample of 258 galaxies in the local universe, providing detailed information about their star formation rates and dust content. We propose to leverage this rich dataset by obtaining oxygen abundance metallicity measurements for 28 of the lowest luminosity LVL galaxies, in order to investigate the relationship between dust properties, metallicity, and star formation at low-luminosity. Recent studies have suggested departures in this regime from known correlations at higher luminosity; however, these findings have been based on only a few low- luminosity galaxies. Specifically, although the weakening of the aromatic emission features in low luminosity galaxies has largely been ascribed to a metallicity effect, high star formation intensities could also produce the observed trends. The proposed observations will target low luminosity galaxies with low star formation rates (< 0.005 M_⊙ yr^-1) in order to explore the full range of parameter space to determine if the observed behavior of the emission from the IR aromatic features is driven primarily by metallicity or star formation.

  14. The Dynamics and Cold Gas Content of Luminous Infrared Galaxies in the Local Universe

    NASA Astrophysics Data System (ADS)

    Privon, George C.

    2014-01-01

    Many of the most luminous galaxies in the local universe are understood to be the product of mergers and interactions between disk galaxies. These encounters trigger enhanced star formation and accretion onto supermassive black holes; the bulk of which is hidden behind significant extinction from dust. Dynamical simulations matched to individual systems can provide great insight into the merger-driven activity by placing objects on a dynamically-determined merger timeline and by enabling follow-up hydrodynamic simulations which can be used to compare simulations directly with observations. New dynamical models will be presented for luminous infrared galaxies drawn from the Great Observatories All-sky LIRG survey, along with a dynamically-motivated merger stage classification system; these are facilitating a detailed comparison of simulated and observed properties of star formation. New observations of the cold ISM in these systems will also be shown,investigating the influence of AGN activity on tracers of high density (> 10^5 cm^-3) molecular gas.

  15. KPC-Scale Properties of Emission-line Galaxies

    NASA Astrophysics Data System (ADS)

    Hemmati, Shoubaneh; Mobasher, Bahram; Candels

    2015-01-01

    We perform a detailed -combined spectroscopic and photometric- study of resolved properties of galaxies at kpc scale and investigate how small-scale and global properties of galaxies are related. The sample consists of 119 galaxies to z~1.3 with the unique feature of having very high-resolution spectroscopic data from long exposure observations with the KECK/DEIMOS. Using HST/ACS and WFC3 data taken as part of the CANDELS project, we produce resolved rest-frame (U-V) color, stellar mass and star formation surface densities, stellar age and extinction maps and profiles along the galaxies rotation axes. We model the optical nebular emission lines using the high-resolution DEIMOS spectra and construct the optical line ratio profiles diagnostic of metallicity (R23) and nebular extinction (Ha/Hb). We find that the nebular dust extinction profile, inferred from Balmer decrement, is in agreement with the average extinction derived from the resolved SED modeling. Using the R23 metallicity profiles we examine, for the first time, the mass metallicity relation across galaxies and explore how this relation changes as a function of spatial position. We identify red and blue 'regions' of statistical significance within individual galaxies, using their rest-frame color maps. As expected, for any given galaxy, the red regions are found to have higher stellar mass surface densities and older ages compared to the blue regions. Furthermore, we quantify the spatial distribution of red and blue regions with respect to both redshift and stellar mass, finding that the stronger concentration of red regions toward the centers of galaxies is not a significant function of either redshift or stellar mass. We find that the 'main sequence' of star forming galaxies exists among both red and blue regions inside galaxies, with the median of blue regions forming a tighter relation with a slope of 1.1±0.1 and a scatter of ˜ 0.2 dex compared to red regions with a slope of 1.3 ± 0.1 and a scatter

  16. A survey of the properties of early-type galaxies

    NASA Technical Reports Server (NTRS)

    Bregman, Joel N.; Roberts, M. S.; Hogg, D. E.

    1990-01-01

    A compilation of the properties of elliptical and early disk galaxies was completed. In addition to material from the literature, such as Infrared Astronomy Satellite (IRAS) fluxes, the compilation includes recent measurements of HI and CO, as well as a review of the x ray properties by Forman and Jones. The data are used to evaluate the gas content of early systems and to search for correlations with x ray emission. The interstellar medium in early-type galaxies is generally dominated by hot interstellar gas (T approx. 10 to the 7th power K; c.f. the review by Fabbiano 1989 and references therein). In addition, a significant fraction of these galaxies show infrared emission (Knapp, et al., 1989), optical emission lines, and visible dust. Sensitive studies in HI and CO of a number of these galaxies have been completed recently, resulting in several detections, particularly of the later types. Researchers wish to understand the connection among these different forms of the interstellar medium, and to examine the theoretical picture of the fate of the hot gas. To do so, they compiled observations of several forms of interstellar matter for a well-defined sample of early-type galaxies. Here they present a statistical analysis of this data base and discuss the implications of the results.

  17. Resolving the stellar outskirts of six Milky Way-like galaxies beyond the Local Group

    NASA Astrophysics Data System (ADS)

    Monachesi, A.; Bell, E. F.; Radburn-Smith, D. J.; Harmsen, B.; de Jong, R. S.; Bailin, J.; Holwerda, B. W.; Streich, D.

    2017-03-01

    Models of galaxy formation in a hierarchical universe predict substantial scatter in the halo-to-halo stellar properties, owing to stochasticity in galaxies' merger histories. Currently, only few detailed observations of galaxy's halos are available, mainly for the Milky Way and M31. The Galaxy Halos, Outer disks, Substructure, Thick disks and Star clusters (GHOSTS) HST survey is the largest study to date of the resolved stellar populations in the outskirts of disk galaxies and its observations offer a direct test of model predictions. Here we present the results we obtain for six highly inclined nearby Milky Way-mass spiral galaxies. We find a great diversity in the properties of their stellar halos.

  18. Central galaxies in different environments: Do they have similar properties?

    SciTech Connect

    Lacerna, I.; Avila-Reese, V.; Hernández-Toledo, H. M.; Rodríguez-Puebla, A.

    2014-06-10

    We perform an exhaustive comparison among central galaxies from Sloan Digital Sky Survey catalogs in different local environments at 0.01 ≤ z ≤ 0.08. The central galaxies are separated into two categories: group centrals (host halos containing satellites) and field centrals (host halos without satellites). From the latter, we select two subsamples: isolated centrals and bright field centrals, both with the same magnitude limit. The stellar mass (M {sub s}) distributions of the field and group central galaxies are different, which explains why in general the field central galaxies are mainly located in the blue cloud/star-forming regions, whereas the group central galaxies are strongly biased to the red sequence/passive regions. The isolated centrals occupy the same regions as the bright field centrals since both populations have similar M {sub s} distributions. At parity of M {sub s}, the color and specific star formation rate (sSFR) distributions of the samples are similar, especially between field and group centrals. Furthermore, we find that the stellar-to-halo mass (M {sub s}-M {sub h}) relation of isolated galaxies does not depend on the color, sSFR, and morphological type. For systems without satellites, the M {sub s}-M {sub h} relation steepens at high halo masses compared to group centrals, which is a consequence of assuming a one-to-one relation between group total stellar mass and halo mass. Under the same assumption, the scatter around the M {sub s}-M {sub h} relation of centrals with satellites increases with halo mass. Our results suggest that the mass growth of central galaxies is mostly driven by the halo mass, with environment and mergers playing a secondary role.

  19. Exercises for distance estimates of the Local Group galaxies using Cepheid variables.

    NASA Astrophysics Data System (ADS)

    Sato, F.

    This paper presentes exercises for distance estimates of the Local Group galaxies LMC, SMC, M31, and NGC 6822 by use of data of the Cepheid variables in them and those in our own Galaxy taken from various literatures. The exercises are suitable for students of senior high schools and /or of liberal arts course of universities.

  20. Constraining particle dark matter using local galaxy distribution

    SciTech Connect

    Ando, Shin’ichiro; Ishiwata, Koji

    2016-06-27

    It has been long discussed that cosmic rays may contain signals of dark matter. In the last couple of years an anomaly of cosmic-ray positrons has drawn a lot of attentions, and recently an excess in cosmic-ray anti-proton has been reported by AMS-02 collaboration. Both excesses may indicate towards decaying or annihilating dark matter with a mass of around 1–10 TeV. In this article we study the gamma rays from dark matter and constraints from cross correlations with distribution of galaxies, particularly in a local volume. We find that gamma rays due to inverse-Compton process have large intensity, and hence they give stringent constraints on dark matter scenarios in the TeV scale mass regime. Taking the recent developments in modeling astrophysical gamma-ray sources as well as comprehensive possibilities of the final state products of dark matter decay or annihilation into account, we show that the parameter regions of decaying dark matter that are suggested to explain the excesses are excluded. We also discuss the constrains on annihilating scenarios.

  1. THE PRESSURE PROFILES OF HOT GAS IN LOCAL GALAXY GROUPS

    SciTech Connect

    Sun, M.; Sarazin, C.; Sehgal, N.; Voit, G. M.; Donahue, M.; Jones, C.; Forman, W.; Vikhlinin, A.

    2011-02-01

    Recent measurements of the Sunyaev-Zel'dovich (SZ) angular power spectrum from the South Pole Telescope and the Atacama Cosmology Telescope demonstrate the importance of understanding baryon physics when using the SZ power spectrum to constrain cosmology. This is challenging since roughly half of the SZ power at l = 3000 is from low-mass systems with 10{sup 13} h {sup -1} M{sub sun} < M{sub 500} < 1.5 x 10{sup 14} h {sup -1} M{sub sun}, which are more difficult to study than systems of higher mass. We present a study of the thermal pressure content for a sample of local galaxy groups from Sun et al. The group Y{sub sph,500}-M{sub 500} relation agrees with the one for clusters derived by Arnaud et al. The group median pressure profile also agrees with the universal pressure profile for clusters derived by Arnaud et al. With this in mind, we briefly discuss several ways to alleviate the tension between the measured low SZ power and the predictions from SZ templates.

  2. 2D kinematical study in local luminous compact blue galaxies. Starburst origin in UCM2325+2318

    NASA Astrophysics Data System (ADS)

    Castillo-Morales, A.; Pérez-Gallego, J.; Gallego, J.; Guzmán, R.; Castander, F.; Garland, C.; Gruel, N.; Pisano, D. J.; Muñoz-Mateos, J. C.; Ocaña, F.; Zamorano, J.

    2013-05-01

    Luminous Compact Blue Galaxies (LCBGs) are small, but vigorously star forming galaxies. Their presence at different redshifts denotes their cosmological relevance and implies that local starburst galaxies, when properly selected, are unique laboratories for studying the complex ecosystem of the star formation process over time. We have selected a representative sample of 22 LCBGs from the SDSS and UCM databases which, although small, provides an excellent reference for comparison with current and future surveys of similar starbursts at high-z. We are carrying out a 2D optical spectroscopic study of this LCBG sample, including spatially resolved maps of kinematics, extinction, SFR and metallicity. This will help us to answer questions regarding the nature of these objects. In this poster we show our results on the kinematical study (Pérez-Gallego et al. 2011) which allows us to classify these galaxies into three different classes: rotating disk (RD) 48%, perturbed rotation (PR) 28% and complex kinematics (CK) 24%. We find 5% of objects show evidence of a recent major merger, 10% of a minor merger, and 45% of a companion. This argues in favor of ongoing interactions with close companions as a mechanism for the enhanced star formation activity in these galaxies. We find only 5% of objects with clear evidence of AGN activity, and 27% with kinematics consistent with SN-driven galactic winds. Therefore, a different mechanism may be responsible for quenching the star formation in LCBGs. The detailed analysis of the physical properties for each galaxy in the sample is on progress and we show in this poster the results on UCM2325+2318 as a prototype LCBG. Between the possible mechanisms to explain the starburst activity in this galaxy, our 2D spectroscopic data support the scenario of an on-going interaction with the possibility for clump B to be the dwarf satellite galaxy (Castillo-Morales et al. 2011, Pérez-Gallego et al. 2010).

  3. Supermassive Black Hole Masses and Global Properties of Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Castillo, Y. S.; Funes, J. G.; Díaz, R. J.

    2006-06-01

    Different scaling laws are known for the mass of supermassive black holes (M_{BH}): M_{BH}-σ M_{BH}-M_{Bulge}; M_{BH}-M_{DM}. We have reviewed these correlations for 17 disk galaxies and tried to find any correlation between M_{BH} and other disk properties (HI and H_2 masses, far infrared luminosity, star formation rate, etc.). The sample was taken from Marconi and Hunt (2003). For these galaxies we have done a search in the literature for the following properties: A) in the nucleus: star formation rates, and luminosities in Hα ; B) in the bulge: luminosity in B-band; C) in the disk: HI and H_2 total masses, total luminosities in X-ray, B band and far infrared, and total star formation rate. In this work we present the compiled data from the literature and the plots of M_{BH} against galaxy HI total mass, M_{BH} against galaxy H_2 total mass, and M_{BH} against disk blue luminosity. We did not find any evident correlation between the M_{BH} and the properties of the disk.

  4. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.

  5. Understanding the Physical Conditions in Local Analogs of High-Redshift Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Spiewak, Renée; Erb, Dawn; Tremonti, Christina A.; Berg, Danielle

    2016-01-01

    Observations of strong nebular emission lines in high-redshift galaxies (z~2) can be illuminated through the use of analogous local galaxies (z<0.4), for which many more emission lines can be measured. The observed offset in the "BPT" ([N II]λ6584/Hα vs. [O III]λ5007/Hβ) nebular diagnostic diagram between the locus of high redshift galaxies and that of typical local galaxies indicates a change in the physical conditions of the galaxies with redshift; the cause of this offset is unknown, but it may be associated with the ionization parameter, the hardness of the ionizing spectrum, or the N/O abundance ratio. To study the offset, we have selected a sample of local galaxies from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 12 (SDSS-III/BOSS DR12), which occupies the same space in the [N II]λ6584/Hα vs. [O III]λ5007/Hβ diagnostic diagram as the z~2 sample. Using a suite of >50 different emission lines, most of which are unavailable in analyses of higher redshift galaxies, and a novel method of improving the spectrophotometric calibration of BOSS data, we investigate the metallicity, ionization state, and abundance ratios of this offset sample in order to shed light on the physical conditions in galaxies in the early universe.

  6. Strangers in the Night: Discovery of a Dwarf Spheroidal Galaxy on Its First Local Group Infall

    NASA Astrophysics Data System (ADS)

    Chapman, S. C.; Peñarrubia, J.; Ibata, R.; McConnachie, A.; Martin, N.; Irwin, M.; Blain, A.; Lewis, G. F.; Letarte, B.; Lo, K.; Ludlow, A.; O'neil, K.

    2007-06-01

    We present spectroscopic observations of the And XII dwarf spheroidal galaxy using DEIMOS/Keck II, showing it to be moving rapidly through the Local Group (-556 km s-1 heliocentric velocity, -281 km s-1 relative to Andromeda), falling into the Local Group from ~115 kpc beyond Andromeda's nucleus. And XII therefore represents a dwarf galaxy plausibly falling into the Local Group for the first time and never having experienced a dense galactic environment. From Green Bank Telescope observations, a limit on the H I gas mass of <3×103 Msolar suggests that And XII's gas could have been removed prior to experiencing the tides of the Local Group galaxies. Orbit models suggest that the dwarf is close to the escape velocity of M31 for published mass models. And XII is our best direct evidence for the late infall of satellite galaxies, a prediction of cosmological simulations.

  7. THE RELATION BETWEEN GALAXY MORPHOLOGY AND ENVIRONMENT IN THE LOCAL UNIVERSE: AN RC3-SDSS PICTURE

    SciTech Connect

    Wilman, David J.; Erwin, Peter

    2012-02-20

    We present results of an analysis of the local (z {approx} 0) morphology-environment relation for 911 bright (M{sub B} < -19) galaxies, based on matching classical RC3 morphologies with the Sloan Digital Sky Survey based group catalog of Yang et al., which includes halo mass estimates. This allows us to study how the relative fractions of spirals, lenticulars, and ellipticals depend on halo mass over a range of 10{sup 11.7}-10{sup 14.8} h{sup -1} M{sub Sun }, from isolated single-galaxy halos to massive groups and low-mass clusters. We pay particular attention to how morphology relates to central versus satellite status (where 'central' galaxies are the most massive within their halo). The fraction of galaxies which are elliptical is a strong function of stellar mass; it is also a strong function of halo mass, but only for central galaxies. We interpret this as evidence for a scenario where elliptical galaxies are always formed, probably via mergers, as central galaxies within their halos, with satellite ellipticals being previously central galaxies accreted onto a larger halo. The overall fraction of galaxies which are S0 increases strongly with halo mass, from {approx}10% to {approx}70%. Here, too, we find striking differences between the central and satellite populations. 20% {+-} 2% of central galaxies with stellar masses M{sub *} > 10{sup 10.5} M{sub Sun} are S0 regardless of halo mass, but satellite S0 galaxies are only found in massive (>10{sup 13} h{sup -1} M{sub Sun }) halos, where they are 69% {+-} 4% of the M{sub *} > 10{sup 10.5} M{sub Sun} satellite population. This suggests two channels for forming S0 galaxies: one which operates for central galaxies and another which transforms lower-mass (M{sub *} {approx}< 10{sup 11} M{sub Sun }) accreted spirals into satellite S0 galaxies in massive halos. Analysis of finer morphological structure (bars and rings in disk galaxies) shows some trends with stellar mass, but none with halo mass; this is consistent

  8. The Relation between Galaxy Morphology and Environment in the Local Universe: An RC3-SDSS Picture

    NASA Astrophysics Data System (ADS)

    Wilman, David J.; Erwin, Peter

    2012-02-01

    We present results of an analysis of the local (z ~ 0) morphology-environment relation for 911 bright (MB < -19) galaxies, based on matching classical RC3 morphologies with the Sloan Digital Sky Survey based group catalog of Yang et al., which includes halo mass estimates. This allows us to study how the relative fractions of spirals, lenticulars, and ellipticals depend on halo mass over a range of 1011.7-1014.8 h -1 M ⊙, from isolated single-galaxy halos to massive groups and low-mass clusters. We pay particular attention to how morphology relates to central versus satellite status (where "central" galaxies are the most massive within their halo). The fraction of galaxies which are elliptical is a strong function of stellar mass; it is also a strong function of halo mass, but only for central galaxies. We interpret this as evidence for a scenario where elliptical galaxies are always formed, probably via mergers, as central galaxies within their halos, with satellite ellipticals being previously central galaxies accreted onto a larger halo. The overall fraction of galaxies which are S0 increases strongly with halo mass, from ~10% to ~70%. Here, too, we find striking differences between the central and satellite populations. 20% ± 2% of central galaxies with stellar masses M * > 1010.5 M ⊙ are S0 regardless of halo mass, but satellite S0 galaxies are only found in massive (>1013 h -1 M ⊙) halos, where they are 69% ± 4% of the M * > 1010.5 M ⊙ satellite population. This suggests two channels for forming S0 galaxies: one which operates for central galaxies and another which transforms lower-mass ( M * <~ 1011 M ⊙) accreted spirals into satellite S0 galaxies in massive halos. Analysis of finer morphological structure (bars and rings in disk galaxies) shows some trends with stellar mass, but none with halo mass; this is consistent with other recent studies which indicate that bars are not strongly influenced by galaxy environment. Radio sources in high

  9. Detecting effects of filaments on galaxy properties in the Sloan Digital Sky Survey III

    NASA Astrophysics Data System (ADS)

    Chen, Yen-Chi; Ho, Shirley; Mandelbaum, Rachel; Bahcall, Neta A.; Brownstein, Joel R.; Freeman, Peter E.; Genovese, Christopher R.; Schneider, Donald P.; Wasserman, Larry

    2017-04-01

    We study the effects of filaments on galaxy properties in the Sloan Digital Sky Survey (SDSS) Data Release 12 using filaments from the 'Cosmic Web Reconstruction' catalogue, a publicly available filament catalogue for SDSS. Since filaments are tracers of medium- to high-density regions, we expect that galaxy properties associated with the environment are dependent on the distance to the nearest filament. Our analysis demonstrates that a red galaxy or a high-mass galaxy tends to reside closer to filaments than a blue or low-mass galaxy. After adjusting the effect from stellar mass, on average, early-forming galaxies or large galaxies have a shorter distance to filaments than late-forming galaxies or small galaxies. For the main galaxy sample, all signals are very significant (>6σ). For the LOWZ and CMASS sample, the stellar mass and size are significant (>2σ). The filament effects we observe persist until z = 0.7 (the edge of the CMASS sample). Comparing our results to those using the galaxy distances from redMaPPer galaxy clusters as a reference, we find a similar result between filaments and clusters. Moreover, we find that the effect of clusters on the stellar mass of nearby galaxies depends on the galaxy's filamentary environment. Our findings illustrate the strong correlation of galaxy properties with proximity to density ridges, strongly supporting the claim that density ridges are good tracers of filaments.

  10. Effects of interaction on the properties of spiral galaxies. II. Isolated galaxies: The zero point

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Moles, M.

    1999-04-01

    We analyse the properties of a sample of 22 bright isolated spiral galaxies on the basis of Johnson B,V,I images and optical rotation curves. The fraction of early morphological types in our sample of isolated galaxies (or in other samples of non-interacting spiral galaxies) appears to be smaller than in samples including interacting systems. The overall morphological aspect is regular and symmetric, but all the galaxies present non-axisymmetric components in the form of bars or rings. We find that the color indices become bluer towards the outer parts and that their central values are well correlated with the total colors. The properties of the bulges span a larger range than those of the disks, that thus are more alike between them. None of the galaxies shows a truncated, type II disk profile. It is found that the relation between surface brightness and size for the bulges, the Kormendy relation, is tighter when only isolated galaxies are considered. We find a similar relation for the disk parameters with an unprecedented low scatter. A Principal Component Analysis of the measured parameters shows that 2 eigenvectors suffice to explain more than 95 % of the total variance. These are, as found for other samples including spiral galaxies in different environmental situations, a scale parameter given by the mass or, equivalently, the luminosity or the size; and a form parameter given by the bulge to disk luminosity ratio, B/D, or, equivalently, by the gradient of the solid-body rotation region of the rotation curve, the G-parameter. We report here a tight correlation between G and B/D for our sample of isolated spirals that could be used as a new distance indicator. Based on data obtained at the 1.5m telescope of the Estacion de Observacion de Calar Alto, Instituto Geografico Nacional, which is jointly operated by the Instituto Geografico Nacional and the Consejo Superior de Investigaciones Cientificas through the Instituto de Astrofisica de Andalucia

  11. Redshift evolution of the dynamical properties of massive galaxies from SDSS-III/BOSS

    SciTech Connect

    Beifiori, Alessandra; Saglia, Roberto P.; Bender, Ralf; Senger, Robert; Thomas, Daniel; Maraston, Claudia; Steele, Oliver; Masters, Karen L.; Pforr, Janine; Tojeiro, Rita; Johansson, Jonas; Nichol, Robert C.; Chen, Yan-Mei; Wake, David; Bolton, Adam; Brownstein, Joel R.; Leauthaud, Alexie; Schneider, Donald P.; Skibba, Ramin; Pan, Kaike; and others

    2014-07-10

    We study the redshift evolution of the dynamical properties of ∼180, 000 massive galaxies from SDSS-III/BOSS combined with a local early-type galaxy sample from SDSS-II in the redshift range 0.1 ≤ z ≤ 0.6. The typical stellar mass of this sample is M{sub *} ∼2 × 10{sup 11} M{sub ☉}. We analyze the evolution of the galaxy parameters effective radius, stellar velocity dispersion, and the dynamical to stellar mass ratio with redshift. As the effective radii of BOSS galaxies at these redshifts are not well resolved in the Sloan Digital Sky Survey (SDSS) imaging we calibrate the SDSS size measurements with Hubble Space Telescope/COSMOS photometry for a sub-sample of galaxies. We further apply a correction for progenitor bias to build a sample which consists of a coeval, passively evolving population. Systematic errors due to size correction and the calculation of dynamical mass are assessed through Monte Carlo simulations. At fixed stellar or dynamical mass, we find moderate evolution in galaxy size and stellar velocity dispersion, in agreement with previous studies. We show that this results in a decrease of the dynamical to stellar mass ratio with redshift at >2σ significance. By combining our sample with high-redshift literature data, we find that this evolution of the dynamical to stellar mass ratio continues beyond z ∼ 0.7 up to z > 2 as M{sub dyn}/M{sub *} ∼(1 + z){sup –0.30±0.12}, further strengthening the evidence for an increase of M{sub dyn}/M{sub *} with cosmic time. This result is in line with recent predictions from galaxy formation simulations based on minor merger driven mass growth, in which the dark matter fraction within the half-light radius increases with cosmic time.

  12. Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies

    NASA Technical Reports Server (NTRS)

    Jia, Jianjun; Ptak, Andrew; Heckman, Timothy M.; Overzier, Roderik A.; Hornschemeier, Ann; LaMassa, Stephanie M.

    2011-01-01

    We have used XMM-Newton to observe six Lyman break analogs (LBAs): members of the rare population of local galaxies that have properties that are very similar to distant Lyman break galaxies. Our six targets were specifically selected because they have optical emission-line properties that are intermediate between starbursts and Type 2 (obscured) active galactic nuclei (AGNs). Our new X-ray data provide an important diagnostic of the presence of an AGN. We find X-ray luminosities of order 10(sup 42) erg per second and ratios of X-ray to far-IR lummositles that are higher than values in pure starburst galaxies by factors ranging from approximately 3 to 30. This strongly suggests the presence of an AGN in at least some of the galaxies. The ratios of the luminosities of the hard (2-10 keV) X-ray to [O III] emission line are low by about an order of magnitude compared with Type 1 AGN, but are consistent with the broad range seen in Type 2 AGN. Either the AGN hard X-rays are significantly obscured or the [O III] emission is dominated by the starburst. We searched for an iron emission line at approximately 6.4 ke V, which is a key feature of obscured AGNs, but only detected emission at the approximately 2sigma level. Finally, we find that the ratios of the mid-infrared (24 micrometer) continuum to [O III]lambda 5007 luminosities in these LBAs are higher than the values for Type 2 AGN by an average of 0.8 dex. Combining all these clues, we conclude that an AGN is likely to be present, but that the bolometric luminosity is produced primarily by an intense starburst. If these black holes are radiating at the Eddington limit, their masses would lie in the range of 10(sup 5) - 10(sup 6) solar mass. These objects may offer ideal local laboratories to investigate the processes by which black holes grew in the early universe.

  13. Redshift-Distance Survey of Early-Type Galaxies. I. Sample Selection, Properties, and Completeness

    NASA Astrophysics Data System (ADS)

    da Costa, L. N.; Bernardi, M.; Alonso, M. V.; Wegner, G.; Willmer, C. N. A.; Pellegrini, P. S.; Rité, C.; Maia, M. A. G.

    2000-07-01

    of the 7S and the recent Tully-Fisher surveys sampling a comparable volume. In subsequent papers of this series we intend to use the ENEAR sample by itself or in combination with the I-band field spiral (SFI) Tully-Fisher survey to analyze the properties of the local peculiar velocity field and to test how sensitive the results are to the different sampling of the galaxy distribution and to the distance relation used. We also anticipate that the homogeneous database assembled will be used for a variety of other applications and serve as a benchmark for similar studies at high redshift. Based on observations at Complejo Astronomico El Leoncito (CASLEO), operated under agreement between the Consejo Nacional de Investigaciones Cientí ficas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan; Cerro Totolo Interamerican Observatory (CTIO), operated by the National Optical Astronomical Observatories, under AURA; European Southern Observatory (ESO), partially under the ESO-ON agreement; Fred Lawrence Whipple Observatory (FLWO) Observatório do Pico dos Dias, operated by the Laboratório Nacional de Astrofísica (LNA) and the MDM Observatory at Kitt Peak.

  14. METALLICITY DISTRIBUTION FUNCTIONS OF FOUR LOCAL GROUP DWARF GALAXIES

    SciTech Connect

    Ross, Teresa L.; Holtzman, Jon; Saha, Abhijit; Anthony-Twarog, Barbara J. E-mail: holtz@nmsu.edu

    2015-06-15

    We present stellar metallicities in Leo I, Leo II, IC 1613, and Phoenix dwarf galaxies derived from medium (F390M) and broad (F555W, F814W) band photometry using the Wide Field Camera 3 instrument on board the Hubble Space Telescope. We measured metallicity distribution functions (MDFs) in two ways, (1) matching stars to isochrones in color–color diagrams and (2) solving for the best linear combination of synthetic populations to match the observed color–color diagram. The synthetic technique reduces the effect of photometric scatter and produces MDFs 30%–50% narrower than the MDFs produced from individually matched stars. We fit the synthetic and individual MDFs to analytical chemical evolution models (CEMs) to quantify the enrichment and the effect of gas flows within the galaxies. Additionally, we measure stellar metallicity gradients in Leo I and II. For IC 1613 and Phoenix our data do not have the radial extent to confirm a metallicity gradient for either galaxy. We find the MDF of Leo I (dwarf spheroidal) to be very peaked with a steep metal-rich cutoff and an extended metal-poor tail, while Leo II (dwarf spheroidal), Phoenix (dwarf transition), and IC 1613 (dwarf irregular) have wider, less peaked MDFs than Leo I. A simple CEM is not the best fit for any of our galaxies; therefore we also fit the “Best Accretion Model” of Lynden-Bell. For Leo II, IC 1613, and Phoenix we find similar accretion parameters for the CEM even though they all have different effective yields, masses, star formation histories, and morphologies. We suggest that the dynamical history of a galaxy is reflected in the MDF, where broad MDFs are seen in galaxies that have chemically evolved in relative isolation and narrowly peaked MDFs are seen in galaxies that have experienced more complicated dynamical interactions concurrent with their chemical evolution.

  15. Investigating the host galaxies of luminous AGN in the local universe with integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    McElroy, Rebecca; Croom, Scott; Husemann, Bernd; Close AGN Reference Survey; SAMI Galaxy Survey

    2017-01-01

    This thesis investigates how galaxies and their super massive black holes coevolve. We use integral field spectroscopy to search for evidence of AGN feedback and triggering. We demonstrate that outflows are ubiquitous among luminous local type 2 AGN using observations from the AAT's SPIRAL instrument. Using multiple component Gaussian emission line decomposition we are able to disentangle the kinematic and ionisation properties of these winds. This allows us to argue that the outflows from these AGN are directly impacting the surrounding ISM within the galaxies. We search for evidence of AGN triggering using data from The Close AGN Reference Survey (CARS). CARS aims to provide a detailed multi-wavelength view of 40 nearby (0.01 < z < 0.06) unobscured AGN to study the link between AGN and their host galaxies. The primary CARS observations come from the MUSE integral field unit on the VLT, and complementary multi-wavelength observations have been approved from SOFIA, Chandra, VLA, HST, and others. We compare the stellar kinematics of active galaxies from CARS to similar inactive galaxies. We then use kinemetry to estimate the degree of dynamical disturbance, to determine whether active nuclei are preferentially hosted in dynamically disturbed or merging systems. Finally, we highlight the discovery of an AGN that has changed spectral type not once, but twice. So called ‘changing look’ AGN are an uncommon phenomenon, but twice changed AGN are much rarer. This AGN first transitioned from a narrow line AGN (type 2) to a broad line AGN (type 1) in the 1980s. It was recently observed as part of CARS. Examination of the MUSE data for this particular source showed that it no longer had the spectral features typical of a type 1 AGN. The continuum emission from the accretion disk was no longer visible and the broad lines were dramatically diminished. In this talk we describe the possible reasons for this change, supported by analysis of multi-epoch optical photometry and

  16. Mapping the Properties of Blue Compact Dwarf Galaxies by Means of Integral Field Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cairós, L. M.; Caon, N.; Weilbacher, P.; Papaderos, P.; García-Lorenzo, B.

    Blue Compact Dwarf (BCD) galaxies are metal-poor and gas-rich systems undergoing intense, spatially extended star-forming activity. These galaxies offer a unique opportunity to investigate dwarf galaxy formation and evolution, and probe violent star formation and its implications on the chemical, dynamical and structural properties of low-mass extragalactic systems near and far. Several fundamental questions in BCD research, such as their star formation histories and the mechanisms that control their cyclic starburst activity, are still far from well understood. In order to improve our understanding on BCD evolution, we are carrying out a comprehensive Integral Field Spectroscopic (IFS) survey of a large sample of BCDs. Integral Field Unit (IFU) spectroscopy provides simultaneously spectral and spatial information, allowing, in just one shot, to study the morphology and evolutionary status of the stellar component, and the physical properties of the warm interstellar medium (e.g., extinction, chemical abundances, kinematics). This ongoing IFS survey will supply much needed local templates that will ease the interpretation of IFS data for intermediate and high-redshift star-forming galaxies.

  17. A redshift survey of IRAS galaxies. V - The acceleration on the Local Group

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    The acceleration on the Local Group is calculated based on a full-sky redshift survey of 5288 galaxies detected by IRAS. A formalism is developed to compute the distribution function of the IRAS acceleration for a given power spectrum of initial perturbations. The computed acceleration on the Local Group points 18-28 deg from the direction of the Local Group peculiar velocity vector. The data suggest that the CMB dipole is indeed due to the motion of the Local Group, that this motion is gravitationally induced, and that the distribution of IRAS galaxies on large scales is related to that of dark matter by a simple linear biasing model.

  18. A homogeneous sample of binary galaxies: Basic observational properties

    NASA Technical Reports Server (NTRS)

    Karachentsev, I. D.

    1990-01-01

    A survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies. Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f(solar), with the mean value (7.8 plus or minus 0.7) f(solar). Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12 plus or minus 0.02 and characteristic merger timescale 0.2 H(exp -1) may significantly influence the rate of dynamical evolution of galaxies.

  19. Galaxy Clusters and Properties in the CFHTLS/VIPERS Survey

    NASA Astrophysics Data System (ADS)

    Gallego Gallego, Sofia Carolina; Murphy, David; Hyazinth Puzia, Thomas

    2015-08-01

    We present our analysis of clusters in the CFHTLS Wide fields using a red-sequence based cluster finding code. The deep five-band photometry and panoramic coverage permits detection of galaxy clusters between z=0 and z~1 over 132 square degrees. We present a cluster catalogue and optical richness estimates as mass proxies, derived cluster properties from a novel template-fitting analysis and cluster redshift measurements utilizing data from the VLT/VIPERS spectroscopic survey.We complement our analysis with studies of mock cluster catalogues generated from N-body simulation lightcones featuring semi-analytic prescriptions of galaxy formation. These provide us with an insight into the performance of the cluster-finding technique, uncertainties in the derived properties of the detected cluster populations and an important comparison of the popular “lambda” optical richness estimator to known dark matter halo properties.This study serves as the perfect precursor to LSST-depth cluster science, providing an important input into how models describe the evolution of clusters and their members as a function of redshift and mass, and the role high-density environments play in galaxy evolution over half the Hubble time.

  20. Testing different AGN tracers on a local sample of Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Pozzi, F.

    2016-08-01

    I will present our new study on a local sample of Seyfert galaxies selected at 12 micron. This sample, given its plenty of information, both photometric and spectroscopic, is a perfect sample to compare, from a statistical point of view, different AGN selection criteria, and AGN derived intrinsic properties. In detail, I will compare AGN activity derived from SED-fitting technique, X-ray luminosity and AGN activity traced by high excitation IR lines, like [NeV] and [OIV]. Moreover, for one particular obscured X-ray Compton-thick source, thanks also to the availability of ALMA data, I will derive a self-consistent overview of the physics behind the emission in different bands,by taking advantage of the photoionization code CLOUDY.

  1. The HI Content of Galaxies as a Function of Local Density and Large-Scale Environment

    NASA Astrophysics Data System (ADS)

    Thoreen, Henry; Cantwell, Kelly; Maloney, Erin; Cane, Thomas; Brough Morris, Theodore; Flory, Oscar; Raskin, Mark; Crone-Odekon, Mary; ALFALFA Team

    2017-01-01

    We examine the HI content of galaxies as a function of environment, based on a catalogue of 41527 galaxies that are part of the 70% complete Arecibo Legacy Fast-ALFA (ALFALFA) survey. We use nearest-neighbor methods to characterize local environment, and a modified version of the algorithm developed for the Galaxy and Mass Assembly (GAMA) survey to classify large-scale environment as group, filament, tendril, or void. We compare the HI content in these environments using statistics that include both HI detections and the upper limits on detections from ALFALFA. The large size of the sample allows to statistically compare the HI content in different environments for early-type galaxies as well as late-type galaxies. This work is supported by NSF grants AST-1211005 and AST-1637339, the Skidmore Faculty-Student Summer Research program, and the Schupf Scholars program.

  2. The Star Formation Histories of Local Group Dwarf Galaxies. III. Characterizing Quenching in Low-mass Galaxies

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon; Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2015-05-01

    We explore the quenching of low-mass galaxies (104 ≲ {{M}\\star } ≲ 108 {{M}⊙ }) as a function of lookback time using the star formation histories (SFHs) of 38 Local Group dwarf galaxies. The SFHs were derived by analyzing color-magnitude diagrams of resolved stellar populations in archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. We find: (1) lower-mass galaxies quench earlier than higher-mass galaxies; (2) inside of Rvirial there is no correlation between a satellite’s current proximity to a massive host and its quenching epoch; and (3) there are hints of systematic differences in the quenching times of M31 and Milky Way (MW) satellites, although the sample size and uncertainties in the SFHs of M31 dwarfs prohibit definitive conclusions. Combined with results from the literature, we qualitatively consider the redshift evolution (z = 0-1) of the quenched galaxy fraction over ˜7 dex in stellar mass (104 ≲ {{M}\\star } ≲ 1011.5 {{M}⊙ }). The quenched fraction of all galaxies generally increases toward the present, with both the lowest and highest-mass systems exhibiting the largest quenched fractions at all redshifts. In contrast, galaxies between {{M}\\star } ˜ 108-1010 {{M}⊙ } have the lowest quenched fractions. We suggest that such intermediate-mass galaxies are the least efficient at quenching. Finally, we compare our quenching times with predictions for infall times for low-mass galaxies associated with the MW. We find that some of the lowest-mass satellites (e.g., CVn II, Leo IV) may have been quenched before infall, while higher-mass satellites (e.g., Leo I, Fornax) typically quench ˜1-4 Gyr after infall. Based on 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., under NASA constract NAS 5-26555.

  3. Scaling relations and the fundamental line of the local group dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Woo, Joanna; Courteau, Stéphane; Dekel, Avishai

    2008-11-01

    We study the scaling relations between global properties of dwarf galaxies in the local group. In addition to quantifying the correlations between pairs of variables, we explore the `shape' of the distribution of galaxies in log parameter space using standardized principal component analysis, the analysis is performed first in the 3D structural parameter space of stellar mass M*, internal velocity V and characteristic radius R* (or surface brightness μ*). It is then extended to a 4D space that includes a stellar population parameter such as metallicity Z or star formation rate . We find that the local group dwarfs basically define a one-parameter `fundamental line' (FL), primarily driven by stellar mass, M*. A more detailed inspection reveals differences between the star formation properties of dwarf irregulars (dI's) and dwarf ellipticals (dE's), beyond the tendency of the latter to be more massive. In particular, the metallicities of dI's are typically lower by a factor of 3 at a given M* and they grow faster with increasing M*, showing a tighter FL in the 4D space for the dE's. The structural scaling relations of dI's resemble those of the more massive spirals, but the dI's have lower star formation rates for a given M* which also grow faster with increasing M*. On the other hand, the FL of the dE's departs from the fundamental plane of bigger ellipticals. While the one-parameter nature of the FL and the associated slopes of the scaling relations are consistent with the general predictions of supernova feedback from Dekel & Woo, the differences between the FL's of the dE's and the dI's remain a challenge and should serve as a guide for the secondary physical processes responsible for these two types.

  4. The Nature of the Second Parameter in the IRX-β Relation for Local Galaxies

    NASA Astrophysics Data System (ADS)

    Grasha, Kathryn; Calzetti, D.; Andrews, J. E.; Lee, J. C.; Dale, D. A.

    2013-01-01

    We present an analysis of 98 galaxies of low-dust content, selected from the Spitzer Local Volume Legacy (LVL) survey, aimed at examining the dust attenuation relation in normal star-forming galaxies. The infrared-excess (IRX-β) diagram is a technique used to correct star-forming galaxies for dust attenuation solely from observations of the ultraviolet (UV) colors, β. The UV colors are tightly related to the total attenuation as measured by the ratio of the infrared (IR) to the far-UV (FUV) flux in starburst galaxies. However, normal star-forming galaxies, when compared to their starburst counterparts, have a much larger spread in the IR to FUV luminosity for a fixed UV spectral slope. We examine the role that the age of the stellar population plays as the ``second parameter'' responsible for the observed deviation in normal star-forming galaxies. We model the FUV to far-IR spectral energy distribution of each galaxy using Starburst99 synthetic stellar spectra, varying the metallicity, attenuation, and age with either constant star formation or instantaneous bursts. We find that, in virtually dust-free galaxies, the stellar population age influences galaxies that are represented with a bursting star formation history (SFH), where an increase in β correlates with an increase in the stellar population age at a significance level of 5σ. The same age-β relation is not seen in galaxies represented with a constant SFH. As a whole, we find that our galaxies have a tight correlation between the FUV to near-IR luminosity and β (6σ significance), suggesting that the scatter from the ``second parameter'' is better defined in terms of β as opposed to the distance from the starburst IRX relation.

  5. Galaxy populations in the Antlia cluster - III. Properties of faint early-type galaxies

    NASA Astrophysics Data System (ADS)

    Smith Castelli, Analía. V.; Cellone, Sergio A.; Faifer, Favio R.; Bassino, Lilia P.; Richtler, Tom; Romero, Gisela A.; Calderón, Juan Pablo; Caso, Juan Pablo

    2012-01-01

    We present a new analysis of the early-type galaxy population in the central region of the Antlia cluster, focusing on the faint systems such as dwarf ellipticals (dEs) and dwarf spheroidals (dSphs). The colour-magnitude relation (CMR) and the relation between luminosity and mean effective surface brightness for galaxies in the central region of Antlia have been previously studied in Paper I of the present series. Now we confirm 22 early-type galaxies as Antlia members, using Gemini-GMOS and Magellan-MIKE spectra. Among them, 15 are dEs from the FS90 Antlia Group catalogue, two belong to the rare type of compact ellipticals (cEs) and five are new faint dwarfs that had never been catalogued before. In addition, we present 16 newly identified low-surface-brightness galaxy candidates, almost half of them displaying morphologies consistent with being Antlia's counterparts of Local Group dSphs, which extend the faint luminosity limit of our study down to MB=-10.1(BT= 22.6) mag. With these new data, we built an improved CMR in the Washington photometric system, i.e. integrated T1 magnitudes versus (C-T1) colours, which extends ˜4 mag faintwards the limit of spectroscopically confirmed Antlia members. When only confirmed early-type members are considered, this relation extends over 10 mag in luminosity with no apparent change in slope or increase in colour dispersion towards its faint end. The intrinsic colour scatter of the relation is compared with those reported for other clusters of galaxies; we argue that it is likely that the large scatter of the CMR, usually reported at faint magnitudes, is mostly due to photometric errors along with an improper membership/morphological classification. The distinct behaviour of the luminosity versus mean effective surface brightness relation at the bright and faint ends is analysed, while it is confirmed that dE galaxies on the same relation present a very similar effective radius, regardless of their colour. The projected spatial

  6. THE STELLAR-TO-HALO MASS RELATION FOR LOCAL GROUP GALAXIES

    SciTech Connect

    Brook, C. B.; Cintio, A. Di; Knebe, A.; Yepes, G.; Gottlöber, S.; Hoffman, Y.; Garrison-Kimmel, S.

    2014-03-20

    We contend that a single power-law halo mass distribution is appropriate for direct matching to the stellar masses of observed Local Group dwarf galaxies, allowing the determination of the slope of the stellar mass-halo mass relation for low-mass galaxies. Errors in halo masses are well defined as the Poisson noise of simulated Local Group realizations, which we determine using local volume simulations. For the stellar mass range 10{sup 7} M {sub ☉}galaxies, we find that the stellar mass-halo mass relation follows a power law with slope of 3.1, significantly steeper than most values in the literature. This steep relation between stellar and halo masses would indicate that Local Group dwarf galaxies are hosted by dark matter halos with a small range of mass. Our methodology is robust down to the stellar mass to which the census of observed Local Group galaxies is complete, but the significant uncertainty in the currently measured slope of the stellar-to-halo mass relation will decrease dramatically if the Local Group completeness limit was 10{sup 6.5} M {sub ☉} or below, highlighting the importance of pushing such limit to lower masses and larger volumes.

  7. CONNECTIONS BETWEEN GALAXY MERGERS AND STARBURST: EVIDENCE FROM THE LOCAL UNIVERSE

    SciTech Connect

    Luo, Wentao; Yang, Xiaohu; Zhang, Youcai E-mail: xyang@sjtu.edu.cn

    2014-07-01

    Major mergers and interactions between gas-rich galaxies with comparable masses are thought to be the main triggers of starburst. In this work, we study, for a large stellar mass range, the interaction rate of the starburst galaxies in the local universe. We focus independently on central and satellite star forming galaxies extracted from the Sloan Digital Sky Survey. Here the starburst galaxies are selected in the star formation rate (SFR) stellar mass plane with SFRs five times larger than the median value found for ''star forming'' galaxies of the same stellar mass. Through visual inspection of their images together with close companions determined using spectroscopic redshifts, we find that ∼50% of the ''starburst'' populations show evident merger features, i.e., tidal tails, bridges between galaxies, double cores, and close companions. In contrast, in the control sample we selected from the normal star forming galaxies, only ∼19% of galaxies are associated with evident mergers. The interaction rates may increase by ∼5% for the starburst sample and 2% for the control sample if close companions determined using photometric redshifts are considered. The contrast of the merger rate between the two samples strengthens the hypothesis that mergers and interactions are indeed the main causes of starburst.

  8. Metallicity Distribution Functions of Four Local Group Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Ross, Teresa L.; Holtzman, Jon; Saha, Abhijit; Anthony-Twarog, Barbara J.

    2015-06-01

    We present stellar metallicities in Leo I, Leo II, IC 1613, and Phoenix dwarf galaxies derived from medium (F390M) and broad (F555W, F814W) band photometry using the Wide Field Camera 3 instrument on board the Hubble Space Telescope. We measured metallicity distribution functions (MDFs) in two ways, (1) matching stars to isochrones in color-color diagrams and (2) solving for the best linear combination of synthetic populations to match the observed color-color diagram. The synthetic technique reduces the effect of photometric scatter and produces MDFs 30%-50% narrower than the MDFs produced from individually matched stars. We fit the synthetic and individual MDFs to analytical chemical evolution models (CEMs) to quantify the enrichment and the effect of gas flows within the galaxies. Additionally, we measure stellar metallicity gradients in Leo I and II. For IC 1613 and Phoenix our data do not have the radial extent to confirm a metallicity gradient for either galaxy. We find the MDF of Leo I (dwarf spheroidal) to be very peaked with a steep metal-rich cutoff and an extended metal-poor tail, while Leo II (dwarf spheroidal), Phoenix (dwarf transition), and IC 1613 (dwarf irregular) have wider, less peaked MDFs than Leo I. A simple CEM is not the best fit for any of our galaxies; therefore we also fit the “Best Accretion Model” of Lynden-Bell. For Leo II, IC 1613, and Phoenix we find similar accretion parameters for the CEM even though they all have different effective yields, masses, star formation histories, and morphologies. We suggest that the dynamical history of a galaxy is reflected in the MDF, where broad MDFs are seen in galaxies that have chemically evolved in relative isolation and narrowly peaked MDFs are seen in galaxies that have experienced more complicated dynamical interactions concurrent with their chemical evolution. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is

  9. Galaxy properties in low X-ray luminosity clusters at z=0.25

    NASA Astrophysics Data System (ADS)

    Balogh, Michael; Bower, R. G.; Smail, Ian; Ziegler, B. L.; Davies, Roger L.; Gaztelu, A.; Fritz, Alexander

    2002-11-01

    We present the first spectroscopic survey of intrinsically low X-ray luminosity clusters at z>> 0, with Hubble Space Telescope (HST) WFPC2 imaging and spectroscopy from Calar Alto and WHT-LDSS2. We study 172 confirmed cluster members in a sample of ten clusters at 0.23 < z < 0.3, with LX<~ 4 × 1043h-2 erg s-1[0.1-2.4 keV] (Ωm= 0.3, Λ= 0.7). The core of each cluster is imaged with WFPC2 in the F702W filter, and the spectroscopic sample is statistically complete to Mr~-19.0 + 5 log h, within an 11 arcmin (~1.8 h-1 Mpc) field. The clusters are dynamically well-separated from the surrounding field and most have velocity distributions consistent with Gaussians. The velocity dispersions range from ~350-850 km s-1, consistent with the local LX-σ correlation. All 10 clusters host a bright, giant elliptical galaxy without emission lines, near the centre of the X-ray emission. We measure the equivalent width of two nebular emission lines, [OII] and Hα, and the Hδ absorption line to classify the cluster members spectrally. Galaxy morphologies are measured from the HST images, using the two-dimensional surface-brightness fitting software GIM2D. Emission-line galaxies in these clusters are relatively rare, comprising only 22 +/- 4 per cent of the sample. There is no evidence that these emission-line galaxies are dynamically distinct from the majority of the cluster population, though our sample is too small to rule out the ~30 per cent difference that has been observed in more massive clusters. We find 11 galaxies, comprising 6 per cent of the cluster members, that are disc-dominated but show no sign of emission in their spectrum. Most of these are relatively isolated, spiral galaxies with smooth discs. We find no cluster members with a starburst or post-starburst spectrum. The striking similarity between the spectral and morphological properties of galaxies in these clusters and those of galaxies in more massive systems at similar redshifts implies that the physical

  10. Photometric Properties of the Most Massive High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Robertson, Brant; Li, Yuexing; Cox, Thomas J.; Hernquist, Lars; Hopkins, Philip F.

    2007-09-01

    We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution hydrodynamical simulations of the hierarchical formation of a z~6 quasar, stellar population synthesis models, template active galactic nucleus (AGN) spectra, prescriptions for interstellar and intergalactic absorption, and the response of modern telescopes, the photometric evolution of galaxies destined to host z~6 quasars is modeled at redshifts z~4-14. These massive galaxies, with enormous stellar masses of M*~1011.5-1012 Msolar and star formation rates of SFR~103-104 Msolar yr-1 at z>~7, satisfy a variety of photometric selection criteria based on Lyman break techniques, including V-band dropouts at z>~5, i-band dropouts at z>~6, and z-band dropouts at z>~7. The observability of the most massive high-redshift galaxies is assessed and compared with a wide range of existing and proposed photometric surveys, including the Sloan Digital Sky Survey (SDSS), Great Observatories Origins Deep Survey (GOODS)/Hubble Ultra Deep Field (HUDF), National Optical Astronomy Observatory Deep Wide-Field Survey (NDWFS), UKIRT Infared Deep Sky Survey (UKIDSS), Infrared Array Camera (IRAC) Shallow Survey, Ultradeep Visible and Infrared Survey Telescope for Astronomy (VISTA), Dark Universe Explorer (DUNE), Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), Large Synoptic Survey Telescope (LSST), and Supernova/Acceleration Probe (SNAP). Massive stellar spheroids descended from z~6 quasars will likely be detected at z~4 by existing surveys, but owing to their low number densities the discovery of quasar progenitor galaxies at z>7 will likely require future surveys of large portions of the sky (>~0.5%) at wavelengths λ>~1 μm. The detection of rare, starbursting, massive galaxies at redshifts z>~6 would provide support for the

  11. Herschel/SPIRE Submillimeter Spectra of Local Active Galaxies

    NASA Astrophysics Data System (ADS)

    Pereira-Santaella, Miguel; Spinoglio, Luigi; Busquet, Gemma; Wilson, Christine D.; Glenn, Jason; Isaak, Kate G.; Kamenetzky, Julia; Rangwala, Naseem; Schirm, Maximilien R. P.; Baes, Maarten; Barlow, Michael J.; Boselli, Alessandro; Cooray, Asantha; Cormier, Diane

    2013-05-01

    We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from J up = 4 to 12, as well as the two [C I] fine structure lines at 492 and 809 GHz and the [N II]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n_H_2 \\sim 103.2-103.9 cm-3 and T kin ~ 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H2 emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C I] emission suggests that it is produced in cold (T kin < 30 K) and dense (n_H_2 \\gt 10^3 cm-3) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H2O emission lines are present. Additionally, three OH+ lines at 909, 971, and 1033 GHz are identified in NGC 7130.

  12. HERSCHEL/SPIRE SUBMILLIMETER SPECTRA OF LOCAL ACTIVE GALAXIES {sup ,}

    SciTech Connect

    Pereira-Santaella, Miguel; Spinoglio, Luigi; Busquet, Gemma; Wilson, Christine D.; Schirm, Maximilien R. P.; Glenn, Jason; Kamenetzky, Julia; Rangwala, Naseem; Isaak, Kate G.; Baes, Maarten; Barlow, Michael J.; Boselli, Alessandro; Cooray, Asantha; Cormier, Diane

    2013-05-01

    We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from J{sub up} = 4 to 12, as well as the two [C I] fine structure lines at 492 and 809 GHz and the [N II]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n{sub H{sub 2}}{approx} 10{sup 3.2}-10{sup 3.9} cm{sup -3} and T{sub kin} {approx} 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H{sub 2} emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C I] emission suggests that it is produced in cold (T{sub kin} < 30 K) and dense (n{sub H{sub 2}}>10{sup 3} cm{sup -3}) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H{sub 2}O emission lines are present. Additionally, three OH{sup +} lines at 909, 971, and 1033 GHz are identified in NGC 7130.

  13. The coevolution of galaxies and supermassive black holes: a local perspective.

    PubMed

    Heckman, Timothy M; Kauffmann, Guinevere

    2011-07-08

    One of the most fascinating discoveries in the past decade was that galaxies typically contain a centrally located black hole with a mass that is millions or even billions of times that of the Sun. There is now compelling evidence that we cannot understand how galaxies formed and evolved without understanding the life cycles of these supermassive black holes (and vice versa). We summarize the current understanding of this coevolution of galaxies and supermassive black holes (based largely on observations of the local, present-day universe) and describe prospects for the future.

  14. VIMOS Integral Field Spectroscopy of Gaseous Nebulae in Local Group Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Held, E. V.; Gullieuszik, M.; Saviane, I.; Sabbadin, F.; Momany, Y.; Rizzi, L.; Bresolin, F.

    The study of very metal-poor dwarf irregular (dIrr) galaxies is fundamental to test the cosmological scenarios of galaxy formation. Among Local Group galaxies, Leo A and SagDIG are probably the most metal-poor dwarfs, as suggested by estimates of their nebular abundances based on the empirical method [I. Saviane, L. Rizzi, E.V. Held, F. Bresolin, Y. Momany in Astron. Astrophys. 390, 59 (2002); E.D. Skillman, R. Terlevich, J. Melnick in Mon. Not. R. Astron. Soc. 240, 563 (1989); L. van Zee, E.D. Skillman, M.P. Haynes in Astrophys. J. 637, 269 (2006)].

  15. ISO Lensing Studies: background galaxies and foreground cluster properties

    NASA Astrophysics Data System (ADS)

    Perez-Martinez, Ricardo

    2003-02-01

    A number of ISO programmes, totaling over 100 hours of observation time, made use of the gravitational lensing phenomenon to extend the sensitivity of ISO observations. Substantial results derived from those programmes have been published, or are in the peer review process, addressing the MIR properties of the background lensed galaxy population. These results, which have important implications for galaxy evolution, and which resolve a large fraction of the 15 and 7 μm infrared-background light, will be briefly summarised. But the data has much further potential. Little has been published to date concerning the implications of the ISO lensing data for the foreground clusters themselves, nor addressing the overlap between the observed ISO sources and lensed populations seen at X-Ray and Sub-mm wavelengths. We report briefly on an ongoing programme to systematically reassess the set of ISO observations of lensing galaxy clusters and to describe and compare the IR properties of the clusters themselves. The overlap between ISO source lists and recently published lists of X-Ray and Sub-mm sources in the same fields is under study.

  16. The luminosity-specific Planetary Nebulae density in Local Group galaxies

    NASA Astrophysics Data System (ADS)

    Corradi, R. L. M.; Buzzoni, A.; Arnaboldi, M.

    The value of the α ratio, the number of PNe per unit bolometric luminosity in a galaxy, is computed using stellar population synthesis models covering the whole range of Hubble types of galaxies.Model predictions are compared with the PNe counts in the Local Group, which indicate a fairly constant value of α - between 1 and 6 PNe per 10^7 solar luminosities - along the Hubble sequence.

  17. The stellar mass-size relation for the most isolated galaxies in the local Universe

    NASA Astrophysics Data System (ADS)

    Fernández Lorenzo, M.; Sulentic, J.; Verdes-Montenegro, L.; Argudo-Fernández, M.

    2013-09-01

    Disentangling processes governing the formation and evolution of galaxies is a fundamental challenge in extragalactic research. In this sense, the current belief that galaxies grow by the action of minor mergers makes the study of the stellar mass-size relation in different environments an important tool for distinguishing effects of internal and external processes. The aim of this work is to study the effects of environment on the growth in size of galaxies. As part of Analysis of the Interstellar Medium of Isolated GAlaxies (AMIGA project), we examine the stellar mass-size relation for a sample of the most isolated galaxies in the local Universe interpreted as stellar systems where evolution has been mainly governed by internal processes. Effects of environment on the stellar mass-size relation are evaluated by comparing our results with samples of less isolated early- and late-type galaxies, as well as, for the first time, different spiral subtypes. Stellar masses in our sample were derived by fitting the SED of each galaxy with KCORRECT. We used two different size estimators, the half-light radius obtained with SEXTRACTOR and the effective radius calculated by fitting a Sérsic profile to the i-band image of each galaxy using GALFIT. We found good agreement between those size estimators when the Sérsic index fell in the range 2.5 < n < 4.5 and 0.5 < n < 2.5 for (visually classified) early- and late-type galaxies, respectively. We find no difference in the stellar mass-size relation for very isolated and less isolated early-type galaxies. We find that late-type isolated galaxies are ˜1.2 times larger than less isolated objects with similar mass. Isolated galaxies and comparison samples were divided into six morphological ranges (E/S0, Spirals, Sb, Sbc, Sc and Scd-Sdm) and five stellar mass bins between log (M*) = [9,11.5]. In all cases, the relation is better defined and has less scatter for the isolated galaxies. We find that as the morphological type becomes

  18. TIGHT CORRELATIONS BETWEEN MASSIVE GALAXY STRUCTURAL PROPERTIES AND DYNAMICS: THE MASS FUNDAMENTAL PLANE WAS IN PLACE BY z ∼ 2

    SciTech Connect

    Bezanson, Rachel; Van Dokkum, Pieter G.; Leja, Joel; Van de Sande, Jesse; Franx, Marijn; Kriek, Mariska

    2013-12-20

    The fundamental plane (FP) is an empirical relation between the size, surface brightness, and velocity dispersion of early-type galaxies. This relation has been studied extensively for early-type galaxies in the local universe to constrain galaxy formation mechanisms. The evolution of the zero point of this plane has been extended to high redshifts to study the luminosity evolution of massive galaxies, under the assumption of structural homology. In this work, we assess this assumption by replacing surface brightness with stellar mass density and present the evolution of the ''mass FP'' for massive, quiescent galaxies since z ∼ 2. By accounting for stellar populations, we thereby isolate and trace structural and dynamical evolution. Despite the observed dramatic evolution in the sizes and morphologies of massive galaxies since z ∼ 3, we find that quiescent galaxies lie on the mass FP out to z ∼ 2. In contrast with ∼1.4 dex evolution in the luminosity FP, average residuals from the z ∼ 0 mass FP are less than ∼0.15 dex since z ∼ 2. Assuming the Hyde and Bernardi mass FP slope, we find that this minimal offset scales as (1 + z){sup –0.095} {sup ±} {sup 0.043}. This result lends credence to previous studies that derived luminosity evolution from the FP. Therefore, despite their compact sizes and suggestions that massive galaxies are more disk-like at z ∼ 2, the relationship between their dynamics and structural properties are consistent with local early-type galaxies. Finally, we find no strong evidence for a tilt of the mass FP relative to the virial plane, but emphasize the need for full models including selection biases to fully investigate this issue.

  19. Selection and Physical Properties of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Fang, G. W.

    2014-09-01

    Extremely Red Objects (EROs) and BzKs continue to attract considerable interest. It has been suggested that they may be the direct progenitors of present-day massive E/S0 galaxies, and can provide crucial constraints on the current galaxy formation and evolution models. Therefore, the key question is to measure the relative fraction of OGs (old galaxies) and DGs (young, and dusty starburst galaxies) in the sample of EROs. Many groups have been currently investigating the fractions of these two ERO populations using a variety of observational approaches, but the fraction of OGs and DGs from different surveys is different. In the meantime, a number of observations suggest that the epoch of z˜2 also plays an important role in galaxy formation and evolution for various reasons: the cosmic star formation rate density (SFRD) begins to drop at z˜2 from a flat plateau at higher redshifts; the morphological type mix of field galaxies changes remarkably at z˜2; the number density of QSOs has a peak at z˜2; and about 50% to 70% of the stellar mass assembly of galaxies took place in the redshift range 1properties of passive and star-forming galaxies at z˜2 in the AEGIS field, and (3) the mid-infrared spectroscopy and multi-wavelength study of ultraluminous infrared galaxies (ULIRGs) at z˜2 in the AEGIS field. Chapter 1 gives a brief review on the research progresses of EROs at z˜1, BzKs at z˜2, and ULIRGs at z˜2, respectively. In Chapter 2 we present a quantitative study of the classification of EROs in the UDF and COSMOS field. Our sample includes 5264 (COSMOS, K_{Vega} ≤19.2) and 24 EROs (UDF, K_{Vega}≤22.0) with (i-K)_{AB}≥2.45. Using the fitting method of spectral energy distribution (SED), [3.6]-[8.0] color, and the nonparametric measures of galaxy morphology, we classify EROs into two classes: DGs and OGs. We find

  20. MASSIVE CLUMPS IN LOCAL GALAXIES: COMPARISONS WITH HIGH-REDSHIFT CLUMPS

    SciTech Connect

    Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Dewberry, J.; Putko, J.; Teich, Y.; Popinchalk, M.; Sanchez Almeida, J.; Munoz-Tunon, C.

    2013-09-01

    Local UV-bright galaxies in the Kiso survey include clumpy systems with kiloparsec-size star complexes that resemble clumpy young galaxies in surveys at high redshift. We compare clump masses and underlying disks in several dozen galaxies from each of these surveys to the star complexes and disks of normal spirals. Photometry and spectroscopy for the Kiso and spiral sample come from the Sloan Digital Sky Survey. We find that the largest Kiso clumpy galaxies resemble Ultra Deep Field (UDF) clumpies in terms of the star formation rates, clump masses, and clump surface densities. Clump masses and surface densities in normal spirals are smaller. If the clump masses are proportional to the turbulent Jeans mass in the interstellar medium, then for the most luminous galaxies in the sequence of normal:Kiso:UDF, the turbulent speeds and surface densities increase in the proportions 1.0:4.7:5.0 and 1.0:4.0:5.1, respectively, for fixed restframe B-band absolute magnitude. For the least luminous galaxies in the overlapping magnitude range, the turbulent speed and surface density trends are 1.0:2.7:7.4 and 1.0:1.4:3.0, respectively. We also find that while all three types have radially decreasing disk intensities when measured with ellipse-fit azimuthal averages, the average profiles are more irregular for UDF clumpies (which are viewed in their restframe UV) than for Kiso galaxies (viewed at g-band), and major axis intensity scans are even more irregular for the UDF than Kiso galaxies. Local clumpy galaxies in the Kiso survey appear to be intermediate between UDF clumpies and normal spirals.

  1. Gas-rich Local Dwarf Star-Forming Galaxies and Their Connection With the Distant Universe

    NASA Astrophysics Data System (ADS)

    Kunth, D.

    1999-07-01

    I discuss the properties of gas-rich forming galaxies. I particularlyemphasize the latest results on Lyα emission that are relevant to the search of distant young galaxies. The interdependance of the Lyα escape with the properties of the ISM in starburst galaxies is outlined. A new modelfrom G. Tenorio-Tagle and his collaborators explains Lyα profiles instarburst galaxies from the hydrodynamics of superbubbles powered by massivestars. I stress again that since Lyα is primarely a diagnostic ofthe ISM, it is mandatory to understand how the ISM and Lyα arerelated to firmly relate Lyα to the cosmic star-formation rate.

  2. Robust automatic photometry of local galaxies from SDSS. Dissecting the color magnitude relation with color profiles

    NASA Astrophysics Data System (ADS)

    Consolandi, Guido; Gavazzi, Giuseppe; Fumagalli, Michele; Dotti, Massimo; Fossati, Matteo

    2016-06-01

    We present an automatic procedure to perform reliable photometry of galaxies on SDSS images. We selected a sample of 5853 galaxies in the Coma and Virgo superclusters. For each galaxy, we derive Petrosian g and i magnitudes, surface brightness and color profiles. Unlike the SDSS pipeline, our procedure is not affected by the well known shredding problem and efficiently extracts Petrosian magnitudes for all galaxies. Hence we derived magnitudes even from the population of galaxies missed by the SDSS which represents ~25% of all local supercluster galaxies and ~95% of galaxies with g < 11 mag. After correcting the g and i magnitudes for Galactic and internal extinction, the blue and red sequences in the color magnitude diagram are well separated, with similar slopes. In addition, we study (i) the color-magnitude diagrams in different galaxy regions, the inner (r ≤ 1 kpc), intermediate (0.2RPet ≤ r ≤ 0.3RPet) and outer, disk-dominated (r ≥ 0.35RPet)) zone; and (ii), we compute template color profiles, discussing the dependences of the templates on the galaxy masses and on their morphological type. The two analyses consistently lead to a picture where elliptical galaxies show no color gradients, irrespective of their masses. Spirals, instead, display a steeper gradient in their color profiles with increasing mass, which is consistent with the growing relevance of a bulge and/or a bar component above 1010 M⊙. Full Table A.1 is 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/591/A38

  3. MCG 06-45-001 - Not a local group galaxy

    NASA Technical Reports Server (NTRS)

    Shore, Steven N.; Sage, Leslie J.

    1990-01-01

    Observations of (C-12)O and (C-13)O J = 1 to 0 for MCG 06-45-001 are examined. It is argued that two features of CO emission with velocities of 1 and 10 km/s indicate that the object is similar to the Galactic molecular clouds in the immediate vicinity, and not to a spiral galaxy as suggested previously. It is considered that CO emission cannot arise from a spiral galaxy at a distance of 2-5 Mpc and that the object is unlikely to be a nearby dwarf. The feature at 10 km/s is considered to arise from a molecular cloud associated with an H II region, which produces the observed IRAS flux.

  4. PACS photometry of the Herschel Reference Survey - far-infrared/submillimetre colours as tracers of dust properties in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Cortese, L.; Fritz, J.; Bianchi, S.; Boselli, A.; Ciesla, L.; Bendo, G. J.; Boquien, M.; Roussel, H.; Baes, M.; Buat, V.; Clemens, M.; Cooray, A.; Cormier, D.; Davies, J. I.; De Looze, I.; Eales, S. A.; Fuller, C.; Hunt, L. K.; Madden, S.; Munoz-Mateos, J.; Pappalardo, C.; Pierini, D.; Rémy-Ruyer, A.; Sauvage, M.; di Serego Alighieri, S.; Smith, M. W. L.; Spinoglio, L.; Vaccari, M.; Vlahakis, C.

    2014-05-01

    We present Herschel/PACS 100 and 160 μm integrated photometry for the 323 galaxies in the Herschel Reference Survey (HRS), a K-band, volume-limited sample of galaxies in the local Universe. Once combined with the Herschel/SPIRE observations already available, these data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the 100-500 μm wavelength range. In this paper, we take advantage of this unique data set to investigate the properties and shape of the far-infrared/submillimetre spectral energy distribution in nearby galaxies. We show that, in the stellar mass range covered by the HRS (8 ≲ log (M*/M⊙) ≲ 12), the far-infrared/submillimetre colours are inconsistent with a single modified blackbody having the same dust emissivity index β for all galaxies. In particular, either β decreases or multiple temperature components are needed, when moving from metal-rich/gas-poor to metal-poor/gas-rich galaxies. We thus investigate how the dust temperature and mass obtained from a single modified blackbody depend on the assumptions made on β. We show that, while the correlations between dust temperature, galaxy structure and star formation rate are strongly model dependent, the dust mass scaling relations are much more reliable, and variations of β only change the strength of the observed trends.

  5. THE METALLICITY EVOLUTION OF BLUE COMPACT DWARF GALAXIES FROM THE INTERMEDIATE REDSHIFT TO THE LOCAL UNIVERSE

    SciTech Connect

    Lian, Jianhui; Hu, Ning; Ye, Chengyun; Kong, Xu; Fang, Guanwen E-mail: xkong@ustc.edu.cn

    2016-03-01

    We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and D{sub n}(4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass–metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower D{sub n}(4000) index values. The insignificant deviation in the mass–metallicity and mass–SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models.

  6. The Properties of IRAS Detected Mergers in the Local Universe

    NASA Astrophysics Data System (ADS)

    Carpineti, Alfredo; Kaviraj, S.; Clements, D. L.; Darg, D.; Hyde, A. K.; Lintott, C.

    2012-01-01

    Galaxy merging is a fundamental aspect of the standard hierarchical galaxy formation paradigm. We have used a large, homogeneous set of nearby mergers, selected through direct visual inspection of the entire SDSS using the GalaxyZoo project, to perform the first blind far-infrared (FIR) study of the local merger population. 3300+ mergers were cross-matched with the Imperial IRAS-FSC Redshift Catalogue, resulting in 606 FIR detections. The IRAS- detected mergers are typically more massive, with smaller separations, weaker tidal forces and bluer colours than their undetected counterparts. The IRAS-detected mergers are mostly (98%) spiral-spiral systems, with a median FIR luminosity of 1011 LSun and a median star-formation rate of around 15 MSun per year. They reside in low density environments but we find no dependence between group richness and their infrared properties. Their SFR seems to depend on the total mass of the system with little dependence on the mass ratio. Optical emission line ratios indicate that the AGN fraction increases with increasing FIR luminosity with a dramatic increase in the members that are ULIRGs . Comparing the typical separations of mergers that are LIRGs and those that are ULIRGs we estimate the timescale for this transition and find a value of (50 ± 16) Myr .

  7. Properties of Galaxies and Groups at z < 1.4

    NASA Astrophysics Data System (ADS)

    Nascimento, R. S.; Lopes, P. A. A.; Ribeiro, A. L. B.

    2014-10-01

    In this work, we analyze a sample of galaxy groups constructed from the fourth data release of the Deep Extragalactic Evolutionary Probe 2 (DEEP2) including the Extended Groth Strip (EGS). This sample was obtained by Gerke et al. (2012) using the Voronoi-Delaunay Method. We selected 105 galaxy groups with at least 8 members in a radius of 4 Mpc. For each group we estimated its properties such as velocity dispersion (σ), physical radius (R_{200}) and mass (M_{200}). We also classify the groups as Gaussian and non-Gaussian (dynamic evolved or not) based on their galaxy velocity distributions. This classification is based on the following statistical tests: Anderson-Darling, Kolmogorov-Smirnov, Shapiro-Wilk, Jarque-Bera, Cramer-von Mises, D'Agostino and Dip test. When the Dip test confirms the hypothesis of the unimodality and all other tests prove the normality of the system, the group is classified as Gaussian. The behavior of gaussianity was checked varying the distance to the center of the group in 2-4 times its physical radius. Our results show that the number of systems classified as non-Gaussian groups grows with the increase of the physical radius.

  8. K-band Properties of Galaxy Clusters and Groups: Brightest Cluster Galaxies and Intracluster Light

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Ting; Mohr, Joseph J.

    2004-12-01

    We investigate the near-infrared K-band properties of the brightest cluster galaxies (BCGs) in a sample of 93 X-ray galaxy clusters and groups, using data from the Two Micron All Sky Survey. Our cluster sample spans a factor of 70 in mass, making it sensitive to any cluster mass-related trends. We derive the cumulative radial distribution for the BCGs in the ensemble and find that 70% of the BCGs are centered in the cluster to within 5% of the virial radius r200; this quantifies earlier findings that BCG position coincides with the cluster center as defined by the X-ray emission peak. We study the correlations between the luminosity of the BCGs (Lb) and the mass and the luminosity of the host clusters, finding that BCGs in more massive clusters are more luminous than their counterparts in less massive systems and that the BCGs become less important in the overall cluster light (L200) as cluster mass increases. By examining a large sample of optically selected groups, we find that these correlations hold for galactic systems less massive than our clusters (<3×1013 Msolar). From the differences between luminosity functions in high- and low-mass clusters, we argue that BCGs grow in luminosity mainly by merging with other luminous galaxies as the host clusters grow hierarchically; the decreasing BCG luminosity fraction (Lb/L200) with cluster mass indicates that the rate of luminosity growth in BCGs is slow compared to the rate at which clusters acquire galaxy light from the field or other merging clusters. Utilizing the observed correlation between the cluster luminosity and mass and a merger tree model for cluster formation, we estimate that the amount of intracluster light (ICL) increases with cluster mass; our calculations suggest that in 1015 Msolar clusters more than 50% of total stellar mass is in ICL, making the role of ICL very important in the evolution and thermodynamic history of clusters. The cluster baryon fraction accounting for the ICL is in good

  9. The impact of galactic properties and environment on the quenching of central and satellite galaxies: a comparison between SDSS, Illustris and L-Galaxies

    NASA Astrophysics Data System (ADS)

    Bluck, Asa F. L.; Mendel, J. Trevor; Ellison, Sara L.; Patton, David R.; Simard, Luc; Henriques, Bruno M. B.; Torrey, Paul; Teimoorinia, Hossen; Moreno, Jorge; Starkenburg, Else

    2016-11-01

    We quantify the impact that a variety of galactic and environmental properties have on the quenching of star formation. We collate a sample of ˜400 000 central and ˜100 000 satellite galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Specifically, we consider central velocity dispersion (σc), stellar, halo, bulge and disc mass, local density, bulge-to-total ratio, groupcentric distance and galaxy-halo mass ratio. We develop and apply a new statistical technique to quantify the impact on the quenched fraction (fQuench) of varying one parameter, while keeping the remaining parameters fixed. For centrals, we find that the fQuench-σc relationship is tighter and steeper than for any other variable considered. We compare to the Illustris hydrodynamical simulation and the Munich semi-analytic model (L-Galaxies), finding that our results for centrals are qualitatively consistent with their predictions for quenching via radio-mode AGN feedback, hinting at the viability of this process in explaining our observational trends. However, we also find evidence that quenching in L-Galaxies is too efficient and quenching in Illustris is not efficient enough, compared to observations. For satellites, we find strong evidence that environment affects their quenched fraction at fixed central velocity dispersion, particularly at lower masses. At higher masses, satellites behave identically to centrals in their quenching. Of the environmental parameters considered, local density affects the quenched fraction of satellites the most at fixed central velocity dispersion.

  10. Interaction/merger-induced starbursts in local very metal-poor dwarfs: link to the common SF in high-z young galaxies

    NASA Astrophysics Data System (ADS)

    Pustilnik, S. A.; Ekta; Kniazev, A. Y.; Chengalur, J. N.; Vanzi, L.

    Introduction. Widespread galaxy formation from pregalactic gas took place in the first 1-3 Gyr after the Big Bang, with most of them forming in low-mass halos (i.e., M in the range of 10^7-10^10 Mo). Observations at high redshifts (z=4-7) are, however, mainly limited to the rare massive "tip of the iceberg" objects. Detailed studies of the properties and the evolution of more common lower-mass young galaxies will have to await the next generation mega telescopes. Although the properties of early galaxies are poorly constrained, it seems reasonable to assume that they should share the following three attributes, viz. a) they should be much more metal-poor than typical local galaxies; b) they should be very gas-rich, and c) due to the much higher galaxy density in the early Universe, interaction/merger induced galaxy-wide SF should be one of the main SF modes. Fortunately, there exist in the local Universe a few good analogs of low-mass young galaxies whose properties can serve as a first approximation for understanding those of the main population of high-redshift galaxies. These are the so-called eXtremely Metal-Deficient (XMD, Z = 1/30 - 1/10 Zo) blue compact galaxies (BCGs). Method. We have conducted a multi-wavelength (including optical/NIR morphology/ photometry, HI imaging, and H-alpha-line kinematics) of a sample of such XMD BCGs and find in a large fraction of them clear evidences that strong interactions or mergers with low-mass objects, provide a trigger mechanism for their observed starbursts. Results. We present about 20 such XMD BCGs arranged in a Toomre-like sequence and also the first results of detailed studies of several individual objects from this sample. Discussion. Since both SF (through cooling rate and the IMF) and its feedback (through the massive star evolution and interaction with the ISM) depend substantially on the ISM metallicity, comprehensive multiwavelength studies of local XMD galaxy mergers, coupled with theoretical modelling

  11. THE NATURE OF THE SECOND PARAMETER IN THE IRX-{beta} RELATION FOR LOCAL GALAXIES

    SciTech Connect

    Grasha, Kathryn; Calzetti, Daniela; Andrews, Jennifer E.; Lee, Janice C.; Dale, Daniel A.

    2013-08-20

    We present an analysis of 98 galaxies of low-dust content, selected from the Spitzer Local Volume Legacy survey, aimed at examining the relation between the ultraviolet (UV) color and dust attenuation in normal star-forming galaxies. The IRX-{beta} diagram relates the total dust attenuation in a galaxy, traced by the far-IR (FIR) to UV ratio, to the observed UV color, indicated by {beta}. Previous research has indicated that while starburst galaxies exhibit a relatively tight IRX-{beta} relation, normal star-forming galaxies do not, and have a much larger spread in the total-IR to far-UV (FUV) luminosity for a fixed UV color. We examine the role that the age of the stellar population plays as the ''second parameter'' responsible for the observed deviation and spread of star-forming galaxies from the starburst relation. We model the FUV to FIR spectral energy distribution of each galaxy according to two broad bins of star formation history (SFH): constant and instantaneous burst. We find clear trends between stellar population mean age estimators (extinction-corrected FUV/NIR, U - B, and EW(H{alpha})) and the UV color {beta}; the trends are mostly driven by the galaxies best-described by instantaneous burst populations. We also find a significant correlation between {beta} and the mean age directly determined from the best-fit instantaneous models. As already indicated by other authors, the UV attenuation in star-forming galaxies may not be recovered with the UV color alone and is highly influenced by the stellar population's mean age and SFH. Overall, the scatter in the IRX-{beta} diagram is better correlated with {beta} than with the perpendicular distance, d{sub p}.

  12. The progenitors of local ultra-massive galaxies across cosmic time: from dusty star-bursting to quiescent stellar populations

    SciTech Connect

    Marchesini, Danilo; Marsan, Cemile Z.; Muzzin, Adam; Franx, Marijn; Stefanon, Mauro; Brammer, Gabriel G.; Vulcani, Benedetta; Fynbo, J. P. U.; Milvang-Jensen, Bo; Dunlop, James S.; Buitrago, Fernando

    2014-10-10

    Using the UltraVISTA catalogs, we investigate the evolution in the 11.4 Gyr since z = 3 of the progenitors of local ultra-massive galaxies (log (M {sub star}/M {sub ☉}) ≈ 11.8; UMGs), providing a complete and consistent picture of how the most massive galaxies at z = 0 have assembled. By selecting the progenitors with a semi-empirical approach using abundance matching, we infer a growth in stellar mass of 0.56{sub −0.25}{sup +0.35} dex, 0.45{sub −0.20}{sup +0.16} dex, and 0.27{sub −0.12}{sup +0.08} dex from z = 3, z = 2, and z = 1, respectively, to z = 0. At z < 1, the progenitors of UMGs constitute a homogeneous population of only quiescent galaxies with old stellar populations. At z > 1, the contribution from star-forming galaxies progressively increases, with the progenitors at 2 < z < 3 being dominated by massive (M {sub star} ≈ 2 × 10{sup 11} M {sub ☉}), dusty (A {sub V} ∼ 1-2.2 mag), star-forming (SFR ∼ 100-400 M {sub ☉} yr{sup –1}) galaxies with a large range in stellar ages. At z = 2.75, ∼15% of the progenitors are quiescent, with properties typical of post-starburst galaxies with little dust extinction and strong Balmer break, and showing a large scatter in color. Our findings indicate that at least half of the stellar content of local UMGs was assembled at z > 1, whereas the remaining was assembled via merging from z ∼ 1 to the present. Most of the quenching of the star-forming progenitors happened between z = 2.75 and z = 1.25, in good agreement with the typical formation redshift and scatter in age of z = 0 UMGs as derived from their fossil records. The progenitors of local UMGs, including the star-forming ones, never lived on the blue cloud since z = 3. We propose an alternative path for the formation of local UMGs that refines previously proposed pictures and that is fully consistent with our findings.

  13. X-ray properties of elliptical galaxies as determined by feedback from their central black holes

    NASA Astrophysics Data System (ADS)

    Pellegrini, Silvia; Ciotti, Luca; Ostriker, Jeremiah

    The centers of elliptical galaxies host supermassive black holes that - through feedback resulting from the accretion process - are believed to significantly affect their hot interstellar medium. The evolution of this hot gas together with that of the nuclear emission during the whole galaxies lifetime has been studied with the aid of high-resolution hydrodynamical simulations, with cooling and heating functions including photoionization plus Compton process, and specific for an average AGN spectral energy distribution (Ciotti and Ostriker 2007). It has been found that nuclear outbursts take place, with duty cycles at the present epoch small enough to account for the small fraction of massive ellipticals observed to be in the "on" (AGN) phase. More recently, the models have been extended to include low radiative efficiency states (ADAFs) and also mechanical coupling between the ISM and the nuclear outflows. Here we present the observational properties resulting for the simulated hot gas and for the nuclear emission. These properties are compared with those of real galaxies, particularly taking into account the recent Chandra results for ellipticals of the local (and possibly low redshift) Universe.

  14. Low surface brightness galaxies

    NASA Technical Reports Server (NTRS)

    Vanderhulst, J. M.; Deblok, W. J. G.; Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    A program to investigate the properties of low surface brightness (LSB) galaxies involving surface photometry in U, B, V, R, I, and H-alpha, HI imaging with the Westerbork Synthesis Radio Telescope (WSRT) and the very large array (VLA) and spectrophotometry of H2 regions in LSB galaxies is underway. The goal is to verify the idea that LSB galaxies have low star formation rates because the local gas density falls below the critical density for star formation, and to study the stellar population and abundances in LSB galaxies. Such information should help understanding the evolutionary history of LSB galaxies. Some preliminary results are reported.

  15. A LOCAL BASELINE OF THE BLACK HOLE MASS SCALING RELATIONS FOR ACTIVE GALAXIES. I. METHODOLOGY AND RESULTS OF PILOT STUDY

    SciTech Connect

    Bennert, Vardha Nicola; Auger, Matthew W.; Treu, Tommaso; Woo, Jong-Hak; Malkan, Matthew A. E-mail: mauger@physics.ucsb.edu E-mail: woo@astro.snu.ac.kr

    2011-01-10

    We present high-quality Keck/LRIS long-slit spectroscopy of a pilot sample of 25 local active galaxies selected from the SDSS (0.02 {<=}z {<=} 0.1; M{sub BH}>10{sup 7} M{sub sun}) to study the relations between black hole mass (M{sub BH}) and host-galaxy properties. We determine stellar kinematics of the host galaxy, deriving stellar-velocity dispersion profiles and rotation curves from three spectral regions (including CaH and K, MgIb triplet, and Ca II triplet). In addition, we perform surface photometry on SDSS images, using a newly developed code for joint multi-band analysis. BH masses are estimated from the width of the H{beta} emission line and the host-galaxy free 5100 A active galactic nucleus (AGN) luminosity. Combining results from spectroscopy and imaging allows us to study four M{sub BH} scaling relations: M{sub BH}-{sigma}, M{sub BH}-L{sub sph}, M{sub BH}-M{sub sph,*}, and M{sub BH}-M{sub sph,dyn}. We find the following results. First, stellar-velocity dispersions determined from aperture spectra (e.g., SDSS fiber spectra or unresolved data from distant galaxies) can be biased, depending on aperture size, AGN contamination, and host-galaxy morphology. However, such a bias cannot explain the offset seen in the M{sub BH}-{sigma} relation at higher redshifts. Second, while the CaT region is the cleanest to determine stellar-velocity dispersions, both the MgIb region, corrected for Fe II emission, and the CaHK region, although often swamped by the AGN power-law continuum and emission lines, can give results accurate to within a few percent. Third, the M{sub BH} scaling relations of our pilot sample agree in slope and scatter with those of other local active and inactive galaxies. In the next papers of the series we will quantify the scaling relations, exploiting the full sample of {approx}100 objects.

  16. Local expansion flows of galaxies: quantifying acceleration effect of dark energy

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Teerikorpi, P.

    2013-08-01

    The nearest expansion flow of galaxies observed around the Local group is studied as an archetypical example of the newly discovered local expansion flows around groups and clusters of galaxies in the nearby Universe. The flow is accelerating due to the antigravity produced by the universal dark energy background. We introduce a new acceleration measure of the flow which is the dimensionless ``acceleration parameter" Q (x) = x - x-2 depending on the normalized distance x only. The parameter is zero at the zero-gravity distance x = 1, and Q(x) ∝ x, when x ≫ 1. At the distance x = 3, the parameter Q = 2.9. Since the expansion flows have a self-similar structure in normalized variables, we expect that the result is valid as well for all the other expansion flows around groups and clusters of galaxies on the spatial scales from ˜ 1 to ˜ 10 Mpc everywhere in the Universe.

  17. Properties of intra-group stars and galaxies in galaxy groups: `normal' versus `fossil' groups

    NASA Astrophysics Data System (ADS)

    Sommer-Larsen, Jesper

    2006-06-01

    Cosmological [cold dark matter (ΛCDM)] TreeSPH simulations of the formation and evolution of 12 galaxy groups of virial mass ~1014Msolar have been performed. The simulations invoke star formation, chemical evolution with non-instantaneous recycling, metallicity-dependent radiative cooling, strong star-burst driven galactic super-winds and effects of a meta-galactic ultraviolet (UV) field. The intra-group (IG) stars are found to contribute 12-45 per cent of the total group B-band luminosity at z = 0. The lowest fractions are found for groups with only a small difference between the R-band magnitudes of the first and second ranked group galaxy (Δm12,R <~ 0.5), the larger fractions are typical of `fossil' groups (FGs, Δm12,R >= 2). A similar conclusion is obtained from BVRIJK surface brightness profiles of the IG star populations. The IG stars in the four FGs are found to be older than the ones in the eight `normal' groups (non-FGs), on average by about 0.3-0.5 Gyr. The typical colour of the IG stellar population is B - R = 1.4-1.5, for both types of systems in good agreement with observations. The mean iron abundance of the IG stars is slightly sub-solar in the central part of the groups (r ~ 100 kpc) decreasing to about 40 per cent solar at about half the virial radius. The IG stars are α-element enhanced with a trend of [O/Fe] increasing with r and an overall [O/Fe] ~ 0.45 dex, indicative of dominant enrichment from Type II supernovae. The abundance properties are similar for both types of systems. The velocity distributions of the IG stars are, at r >~ 30 kpc, significantly more radially anisotropic for FGs than for the non-FGs; this also holds for the velocity distributions of the group galaxies. This indicates that an important characteristic determining whether a group becomes fossil or not, apart from its formation time, as discussed by D'Onghia et al., is the `initial' velocity distribution of the group galaxies. For FGs, one can dynamically infer the

  18. RR Lyrae stars in local group galaxies. I. NGC 185

    SciTech Connect

    Saha, A.; Hoessel, J.G. Space Telescope Science Institute, Baltimore, MD Washburn Observatory, Madison, WI )

    1990-01-01

    Deep CCD images of NGC 185 taken with the 4-shooter on the Hale 5-m telescope have been processed to find and photometrically measure RR Lyrae stars. 176 variable stars have been found, of which 151 are surmised to be RR Lyrae stars. Finding charts, periods, and light curves are presented. The RR Lyrae stars in this galaxy have a very wide distribution of periods indicating a wide range of metallicity. The mean magnitudes of the RR Lyraes is determined to be 25.20 mag. A distance modulus of 23.79 is derived, based on the best currently available values of foreground extinction and mean absolute magnitudes of RR Lyrae stars. 33 refs.

  19. The JCMT nearby galaxies legacy survey - X. Environmental effects on the molecular gas and star formation properties of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, C. D.; Golding, J.; Warren, B. E.; Israel, F. P.; Serjeant, S.; Knapen, J. H.; Sánchez-Gallego, J. R.; Barmby, P.; Bendo, G. J.; Rosolowsky, E.; van der Werf, P.

    2016-03-01

    We present a study of the molecular gas properties in a sample of 98 H I - flux selected spiral galaxies within ˜25 Mpc, using the CO J = 3 - 2 line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H2 mass in the Virgo galaxies, despite their lower mean H I mass. This leads to a significantly higher H2 to H I ratio for Virgo galaxies. Combining our data with complementary Hα star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H2 masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative of differences in the star formation process between low- and high-mass galaxies, and a negative correlation between the molecular gas depletion time and the specific star formation rate.

  20. Power spectrum tomography of dark matter annihilation with local galaxy distribution

    SciTech Connect

    Ando, Shin'ichiro

    2014-10-01

    Cross-correlating the gamma-ray background with local galaxy catalogs potentially gives stringent constraints on dark matter annihilation. We provide updated theoretical estimates of sensitivities to the annihilation cross section from gamma-ray data with Fermi telescope and 2MASS galaxy catalogs, by elaborating the galaxy power spectrum and astrophysical backgrounds, and adopting the Markov-Chain Monte Carlo simulations. In particular, we show that taking tomographic approach by dividing the galaxy catalogs into more than one redshift slice will improve the sensitivity by a factor of a few to several. If dark matter halos contain lots of bright substructures, yielding a large annihilation boost (e.g., a factor of ∼100 for galaxy-size halos), then one may be able to probe the canonical annihilation cross section for thermal production mechanism up to masses of ∼700 GeV. Even with modest substructure boost (e.g., a factor of ∼10 for galaxy-size halos), on the other hand, the sensitivities could still reach a factor of three larger than the canonical cross section for dark matter masses of tens to a few hundreds of GeV.

  1. What have we learned from the XMM-Newton surveys of Local Group Galaxies?

    NASA Astrophysics Data System (ADS)

    Haberl, F.

    2016-06-01

    The study of X-ray source populations and diffuse X-ray emission in nearby galaxies is of major importance in understanding the X-ray output of more distant galaxies as well as learning about processes that occur on interstellar scales within our own Galaxy. Depending on the star formation history of the galaxies different types of X-ray sources dominate the total X-ray emission. With modern observatories like XMM-Newton the various classes of X-ray sources (high and low mass X-ray binaries, supernova remnants, super-soft sources) can be studied to the faintest end of their luminosity distribution in Local Group galaxies. XMM-Newton successfully surveyed the large spiral galaxies M31 and M33 and the star forming, irregular Magellanic Clouds. I'll summarise the most important results we have obtained from older populations like low mass X-ray binaries and classical novae in M31 to the younger populations of high mass X-ray binaries and supernova remnants in the Magellanic Clouds. I'll discuss still open questions in this field of research which can be addressed using the high sensitivity of the XMM-Newton instruments.

  2. Neutral hydrogen and optical properties of three amorphous galaxies

    NASA Technical Reports Server (NTRS)

    Hunter, Deidre A.; Woerden, Hugo Van; Gallagher, John S., III

    1994-01-01

    (exp 9) solar mass for NGC 1800 at 1.5 R(sub H). At approximately R(sub 25) to the east there is a large H I shell. Also at approximately R(sub 25) on both sides the velocity gradient switches by 90 deg, and in the interior the rotation is about the major axis. The central gas density is low and falls off slowly. In the inner regions NGC 4670 resembles an S0/a galaxy seen rather edge-on. It contains a central supergiant H II region with very high velocity widths (FWHM less than or equal to 180 km/s) and complex velocity structures. It is a radio continuum source as well. The H I gas is a single spherical cloud or a disk at low inclination centered on the galaxy with a slight elongation along the optical major axis and rotation about the minor axis. The central gas density is high, and there is a high degree of concentration. The rotation speed indicates a total mass of 5 x 10(exp 10) solar mass at 1.1 R(sub H). We compare these characteristics with properties of gas in the presence of stellar bar potentials, gas warps, and interacting and merging galaxy models. Although there are inconsistencies and uncertainties, we conclude that NGC 1140 is a spiral of low surface brightness that has undergone a merger, while NGC 1800 and NGC 4670 are, respectively, probably an Im system and a spiral that had an encounter of the Noguchi (1988a) kind.

  3. X-Ray Properties of Lyman Break Galaxies in the Hubble Deep Field North Region

    NASA Technical Reports Server (NTRS)

    Nandra, K.; Mushotzky, R. F.; Arnaud, K.; Steidel, C. C.; Adelberger, K. L.; Gardner, J. P.; Teplitz, H. I.; Windhorst, R. A.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We describe the X-ray properties of a large sample of z approximately 3 Lyman Break Galaxies (LBGs) in the region of the Hubble Deep Field North, derived from the 1 Ms public Chandra observation. Of our sample of 148 LBGs, four are detected individually. This immediately gives a measure of the bright AGN (active galactic nuclei) fraction in these galaxies of approximately 3 per cent, which is in agreement with that derived from the UV (ultraviolet) spectra. The X-ray color of the detected sources indicates that they are probably moderately obscured. Stacking of the remainder shows a significant detection (6 sigma) with an average luminosity of 3.5 x 10(exp 41) erg/s per galaxy in the rest frame 2-10 keV band. We have also studied a comparison sample of 95 z approximately 1 "Balmer Break" galaxies. Eight of these are detected directly, with at least two clear AGN based on their high X-ray luminosity and very hard X-ray spectra respectively. The remainder are of relatively low luminosity (< 10(exp 42) erg/s, and the X-rays could arise from either AGN or rapid star-formation. The X-ray colors and evidence from other wavebands favor the latter interpretation. Excluding the clear AGN, we deduce a mean X-ray luminosity of 6.6 x 10(exp 40) erg/s, a factor approximately 5 lower than the LBGs. The average ratio of the UV and X-ray luminosities of these star forming galaxies L(sub UV)/L (sub X), however, is approximately the same at z = 1 as it is at z = 3. This scaling implies that the X-ray emission follows the current star formation rate, as measured by the UV luminosity. We use our results to constrain the star formation rate at z approximately 3 from an X-ray perspective. Assuming the locally established correlation between X-ray and far-IR (infrared) luminosity, the average inferred star formation rate in each Lyman break galaxy is found to be approximately 60 solar mass/yr, in excellent agreement with the extinction-corrected UV estimates. This provides an external

  4. The complex evolutionary paths of local infrared bright galaxies: a high-angular resolution mid-infrared view

    NASA Astrophysics Data System (ADS)

    Alonso-Herrero, A.; Poulton, R.; Roche, P. F.; Hernán-Caballero, A.; Aretxaga, I.; Martínez-Paredes, M.; Ramos Almeida, C.; Pereira-Santaella, M.; Díaz-Santos, T.; Levenson, N. A.; Packham, C.; Colina, L.; Esquej, P.; González-Martín, O.; Ichikawa, K.; Imanishi, M.; Rodríguez Espinosa, J. M.; Telesco, C.

    2016-12-01

    We investigate the evolutionary connection between local infrared (IR)-bright galaxies (log LIR ≥ 11.4 L⊙) and quasars. We use high-angular resolution (˜0.3-0.4 arcsec ˜ few hundred parsecs) 8-13 μm ground-based spectroscopy to disentangle the active galactic nuclei (AGN) mid-IR properties from those of star formation. The comparison between the nuclear 11.3 μm polycyclic aromatic hydrocarbon feature emission and that measured with Spitzer/Spitzer Infrared Spectrograph indicates that the star formation is extended over a few kpc in the IR-bright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or projected nuclear separation. This suggests that the changes in the distribution of the nuclear obscuring material may be taking place rapidly and at different interaction stages washing out the evidence of an evolutionary path. When compared to normal AGN, the nuclear star formation activity of quasars appears to be dimming, whereas it is enhanced in some IR-bright nuclei, suggesting that the latter are in an earlier star formation-dominated phase.

  5. The role of galaxy interaction in the SFR-M {sub *} relation: characterizing morphological properties of Herschel-selected galaxies at 0.2 < z < 1.5

    SciTech Connect

    Hung, Chao-Ling; Sanders, D. B.; Casey, C. M.; Lee, N.; Barnes, J. E.; Koss, M.; Larson, K. L.; Lockhart, K.; Man, A. W. S.; Mann, A. W.; Capak, P.; Kartaltepe, J. S.; Le Floc'h, E.; Riguccini, L.; Scoville, N.; Symeonidis, M.

    2013-12-01

    Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L {sub IR} ≳ 10{sup 11.6} L {sub ☉}) in the local universe (z ≲ 0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M {sub *} relation or the {sup g}alaxy main sequence{sup )} have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at a given M {sub *} increases with redshift, the existence of the galaxy main sequence implies that massive, IR-luminous galaxies at high z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M {sub *} relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Using a detailed visual classification scheme, we show that the fraction of 'disk galaxies' decreases and the fraction of 'irregular' galaxies increases systematically with increasing L {sub IR} out to z ≲ 1.5 and z ≲ 1.0, respectively. At L {sub IR} >10{sup 11.5} L {sub ☉}, ≳ 50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M {sub *} relation, supporting the view that galaxies falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that ≳ 18% of massive IR-luminous 'main-sequence galaxies' are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model.

  6. On the nature of local instabilities in rotating galactic coronae and cool cores of galaxy clusters

    SciTech Connect

    Nipoti, Carlo; Posti, Lorenzo

    2014-09-01

    A long-standing question is whether radiative cooling can lead to local condensation of cold gas in the hot atmospheres of galaxies and galaxy clusters. We address this problem by studying the nature of local instabilities in rotating, stratified, weakly magnetized, optically thin plasmas in the presence of radiative cooling and anisotropic thermal conduction. For both axisymmetric and nonaxisymmetric linear perturbations, we provide general equations which can be applied locally to specific systems to establish whether they are unstable and, in case of instability, to determine the kind of evolution (monotonically growing or overstable) and the growth rates of the unstable modes. We present results for models of rotating plasmas representative of Milky-Way-like galaxy coronae and cool-cores of galaxy clusters. We show that the unstable modes arise from a combination of thermal, magnetothermal, magnetorotational, and heat-flux-driven buoyancy instabilities. Local condensation of cold clouds tends to be hampered in cluster cool cores, while it is possible under certain conditions in rotating galactic coronae. If the magnetic field is sufficiently weak, then the magnetorotational instability is dominant even in these pressure-supported systems.

  7. A general relativistic signature in the galaxy bispectrum: the local effects of observing on the lightcone

    NASA Astrophysics Data System (ADS)

    Umeh, Obinna; Jolicoeur, Sheean; Maartens, Roy; Clarkson, Chris

    2017-03-01

    Next-generation galaxy surveys will increasingly rely on the galaxy bispectrum to improve cosmological constraints, especially on primordial non-Gaussianity. A key theoretical requirement that remains to be developed is the analysis of general relativistic effects on the bispectrum, which arise from observing galaxies on the past lightcone, as well as from relativistic corrections to the dynamics. As an initial step towards a fully relativistic analysis of the galaxy bispectrum, we compute for the first time the local relativistic lightcone effects on the bispectrum, which come from Doppler and gravitational potential contributions. For the galaxy bispectrum, the problem is much more complex than for the power spectrum, since we need the lightcone corrections at second order. Mode-coupling contributions at second order mean that relativistic corrections can be non-negligible at smaller scales than in the case of the power spectrum. In a primordial Gaussian universe, we show that the local lightcone projection effects for squeezed shapes at z ~ 1 mean that the bispectrum can differ from the Newtonian prediction by gtrsim 10% when the short modes are k lesssim (50 Mpc)‑1. These relativistic projection effects, if ignored in the analysis of observations, could be mistaken for primordial non-Gaussianity. For upcoming surveys which probe equality scales and beyond, all relativistic lightcone effects and relativistic dynamical corrections should be included for an accurate measurement of primordial non-Gaussianity.

  8. Infrared properties of z = 7 galaxies from cosmological simulations

    SciTech Connect

    Cen, Renyue; Kimm, Taysun

    2014-02-10

    Three-dimensional panchromatic dust radiative transfer calculations are performed on a set of 198 galaxies of stellar masses in the range of 5 × 10{sup 8} to 3 × 10{sup 10} M {sub ☉} from a cosmological hydrodynamic simulation (resolved at 29 h {sup –1} pc) at z ∼ 7. In a companion paper, the stellar mass and UV luminosity functions and the UV-optical and FUV-NUV colors are shown to be in good agreement with observations if a Small Magellanic Cloud type dust extinction curve is adopted. Here, we make useful predictions, self-consistently, of the infrared properties of these z ∼ 7 simulated galaxies that can be confronted with upcoming ALMA data. Our findings are as follows. (1) The effective radius in the rest-frame MIPS70 μm band is in the range of 80-400 pc proper for z = 7 galaxies with L {sub FIR} = 10{sup 11.3}-10{sup 12} L {sub ☉}. (2) The median of the peak wavelength of the far-infrared (FIR) spectral energy distribution is in the range of 45-60 μm, depending on the dust-to-metal ratio. (3) For star formation rate in the range of 3-100 M {sub ☉} yr{sup –1}, the median FIR to bolometric luminosity ratio is 60%-90%. (4) The FIR luminosity function displays a power law in the high end with a slope of –3.1 ± 0.4 instead of the usual exponential decline.

  9. RELATIONS BETWEEN CENTRAL BLACK HOLE MASS AND TOTAL GALAXY STELLAR MASS IN THE LOCAL UNIVERSE

    SciTech Connect

    Reines, Amy E.; Volonteri, Marta

    2015-11-10

    Scaling relations between central black hole (BH) mass and host galaxy properties are of fundamental importance to studies of BH and galaxy evolution throughout cosmic time. Here we investigate the relationship between BH mass and host galaxy total stellar mass using a sample of 262 broad-line active galactic nuclei (AGNs) in the nearby universe (z < 0.055), as well as 79 galaxies with dynamical BH masses. The vast majority of our AGN sample is constructed using Sloan Digital Sky Survey spectroscopy and searching for Seyfert-like narrow-line ratios and broad Hα emission. BH masses are estimated using standard virial techniques. We also include a small number of dwarf galaxies with total stellar masses M{sub stellar} ≲ 10{sup 9.5} M{sub ⊙} and a subsample of the reverberation-mapped AGNs. Total stellar masses of all 341 galaxies are calculated in the most consistent manner feasible using color-dependent mass-to-light ratios. We find a clear correlation between BH mass and total stellar mass for the AGN host galaxies, with M{sub BH} ∝ M{sub stellar}, similar to that of early-type galaxies with dynamically detected BHs. However, the relation defined by the AGNs has a normalization that is lower by more than an order of magnitude, with a BH-to-total stellar mass fraction of M{sub BH}/M{sub stellar} ∼ 0.025% across the stellar mass range 10{sup 8} ≤ M{sub stellar}/M{sub ⊙} ≤ 10{sup 12}. This result has significant implications for studies at high redshift and cosmological simulations in which stellar bulges cannot be resolved.

  10. Brightest cluster galaxies in the extended GMRT radio halo cluster sample. Radio properties and cluster dynamics

    NASA Astrophysics Data System (ADS)

    Kale, R.; Venturi, T.; Cassano, R.; Giacintucci, S.; Bardelli, S.; Dallacasa, D.; Zucca, E.

    2015-09-01

    Aims: First-ranked galaxies in clusters, usually referred to as brightest cluster galaxies (BCGs), show exceptional properties over the whole electromagnetic spectrum. They are the most massive elliptical galaxies and show the highest probability to be radio loud. Moreover, their special location at the centres of galaxy clusters raises the question of the role of the environment in shaping their radio properties. In the attempt to separate the effect of the galaxy mass and of the environment on their statistical radio properties, we investigate the possible dependence of the occurrence of radio loudness and of the fractional radio luminosity function on the dynamical state of the hosting cluster. Methods: We studied the radio properties of the BCGs in the Extended GMRT Radio Halo Survey (EGRHS), which consists of 65 clusters in the redshift range 0.2-0.4, with X-ray luminosity LX ≥ 5 × 1044 erg s-1, and quantitative information on their dynamical state from high-quality Chandra imaging. We obtained a statistical sample of 59 BCGs, which we divided into two classes, depending on whether the dynamical state of the host cluster was merging (M) or relaxed (R). Results: Of the 59 BCGs, 28 are radio loud and 31 are radio quiet. The radio-loud sources are favourably located in relaxed clusters (71%), while the reverse is true for the radio-quiet BCGs, which are mostly located in merging systems (81%). The fractional radio luminosity function for the BCGs in merging and relaxed clusters is different, and it is considerably higher for BCGs in relaxed clusters, where the total fraction of radio loudness reaches almost 90%, to be compared to the ~30% in merging clusters. For relaxed clusters, we found a positive correlation between the radio power of the BCGs and the strength of the cool core, consistent with previous studies on local samples. Conclusions: Our study suggests that the radio loudness of the BCGs strongly depends on the cluster dynamics; their fraction is

  11. THE L-{sigma} RELATION OF LOCAL H II GALAXIES

    SciTech Connect

    Bordalo, V.; Telles, E. E-mail: etelles@on.br

    2011-07-01

    For the first time we present a new data set of emission line widths for 118 star-forming regions in H II galaxies (HIIGs). This homogeneous set is used to investigate the L-{sigma} relation in conjunction with optical spectrophotometric observations. We were able to classify their nebular emission line profiles due to our high-resolution spectra. Peculiarities in the line profiles such as sharp lines, wings, asymmetries, and in some cases more than one component in emission were verified. From a new independent homogeneous set of spectrophotometric data, we derived physical condition parameters and performed statistical principal component analysis. We have investigated the potential role of metallicity (O/H), H{beta} equivalent width (W{sub H{beta}}), and ionization ratio [O III]/[O II] to account for the observational scatter of the L-{sigma} relation. Our results indicate that the L-{sigma} relation for HIIGs is more sensitive to the evolution of the current starburst event (short-term evolution) and dated by W{sub H}{beta} or even the [O III]/[O II] ratio. The long-term evolution measured by O/H also plays a potential role in determining the luminosity of the current burst for a given velocity dispersion and age as previously suggested. Additionally, galaxies showing Gaussian line profiles present tighter correlations indicating that they are the best targets for the application of the parametric relations as an extragalactic cosmological distance indicator. Best fits for a restricted homogeneous sample of 45 HIIGs provide us with a set of new extragalactic distance indicators with an rms scatter compatible with observational errors of {delta}log L{sub H}{alpha} = 0.2 dex or 0.5 mag. Improvements may still come from future optimized observational programs to reduce the observational uncertainties on the predicted luminosities of HIIGs in order to achieve the precision required for the application of these relations as tests of cosmological models.

  12. LOCAL LUMINOUS INFRARED GALAXIES. III. CO-EVOLUTION OF BLACK HOLE GROWTH AND STAR FORMATION ACTIVITY?

    SciTech Connect

    Alonso-Herrero, Almudena; Hernan-Caballero, Antonio; Pereira-Santaella, Miguel; Rieke, George H.; Diamond-Stanic, Aleksandar M.; Wang Yiping; Rigopoulou, Dimitra

    2013-03-10

    Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78 Mpc). We estimate typical BH masses of 3 Multiplication-Sign 10{sup 7} M{sub Sun} using [Ne III] 15.56 {mu}m and optical [O III] {lambda}5007 gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs, the current SFR is taking place not only in the inner nuclear {approx}1.5 kpc region, as estimated from the nuclear 11.3 {mu}m PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar active galactic nucleus (AGN) luminosities. However, the majority of the IR-bright galaxies in the revised-Shapley-Ames Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All of this suggests that in local LIRGs there is a distinct IR-bright star-forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy.

  13. The ACS Nearby Galaxy Survey Treasury. VIII. The Global Star Formation Histories of 60 Dwarf Galaxies in the Local Volume

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Dalcanton, Julianne J.; Williams, Benjamin F.; Gilbert, Karoline M.; Skillman, Evan D.; Seth, Anil C.; Dolphin, Andrew E.; McQuinn, Kristen B. W.; Gogarten, Stephanie M.; Holtzman, Jon; Rosema, Keith; Cole, Andrew; Karachentsev, Igor D.; Zaritsky, Dennis

    2011-09-01

    We present uniformly measured star formation histories (SFHs) of 60 nearby (D <~ 4 Mpc) dwarf galaxies based on color-magnitude diagrams of resolved stellar populations from images taken with the Hubble Space Telescope and analyzed as part of the ACS Nearby Galaxy Survey Treasury program (ANGST). This volume-limited sample contains 12 dwarf spheroidal (dSph)/dwarf elliptical (dE), 5 dwarf spiral, 28 dwarf irregular (dI), 12 dSph/dI (transition), and 3 tidal dwarf galaxies. The sample spans a range of ~10 mag in MB and covers a wide range of environments, from highly interacting to truly isolated. From the best-fit SFHs, we find three significant results for dwarf galaxies in the ANGST volume: (1) the majority of dwarf galaxies formed the bulk of their mass prior to z ~ 1, regardless of current morphological type; (2) the mean SFHs of dIs, transition dwarf galaxies (dTrans), and dSphs are similar over most of cosmic time, and only begin to diverge a few Gyr ago, with the clearest differences between the three appearing during the most recent 1 Gyr and (3) the SFHs are complex and the mean values are inconsistent with simple SFH models, e.g., single bursts, constant star formation rates (SFRs), or smooth, exponentially declining SFRs. The mean SFHs show clear divergence from the cosmic SFH at z <~ 0.7, which could be evidence that low-mass systems have experienced delayed star formation relative to more massive galaxies. The sample shows a strong density-morphology relationship, such that the dSphs in the sample are less isolated than the dIs. We find that the transition from a gas-rich to gas-poor galaxy cannot be solely due to internal mechanisms such as stellar feedback, and instead is likely the result of external mechanisms, e.g., ram pressure and tidal stripping and tidal forces. In terms of their environments, SFHs, and gas fractions, the majority of the dTrans appear to be low-mass dIs that simply lack Hα emission, similar to Local Group (LG) dTrans DDO 210

  14. Physical Properties of Emission-Line Galaxies at 2 from Near-Infrared Spectroscopy with Magellan FIRE

    NASA Astrophysics Data System (ADS)

    Masters, Daniel C.; McCarthy, P. J.; Malkan, M. A.; Siana, B. D.; Scarlata, C.; Hathi, N. P.; Atek, H.; Henry, A. L.; WISP Team

    2014-01-01

    We present results from near-infrared spectroscopy with Magellan FIRE of 26 strong emission-line galaxies at 2.2 and 1.5. The sample was selected from the WFC3 Infrared Spectroscopic Parallels (WISP) survey, which uses the near-infrared grism capability of the Hubble Space Telescope Wide Field Camera 3 to detect emission-line galaxies over 0.5 < z < 2.3. High-resolution ( 5000) follow-up spectroscopy with Magellan FIRE over 1.0--2.5 microns resolves important rest-frame optical emission lines, allowing us to measure physical properties such as dust obscuration, metal abundance, star formation rate, ionization parameter, and emission line kinematics. We also analyze the properties of composite spectra derived from the FIRE-observed sample. With this relatively large sample of rest-frame optical spectra we can make statistical inferences about the population of emission-line galaxies at 2. We find that the galaxies are low metallicity ( 1/5-1/2 Z_solar) as determined from the R23 calibration. The galaxies are low dust extinction on average (E(B-V 0.2) but with significant scatter. The dust-corrected H-alpha star formation rates range from ~10--150 M_sun yr^-1 with a mean of 50 M_su yr^-1. The average ionization parameter for the sample, log U ~ -2.5, is higher than typically found for star-forming galaxies in the local universe but consistent with those found in more intense starbursting regions in galaxies such as M82. Emission line velocity dispersions are measured to be 71 +- 38 km s^-1, in good agreement with other studies that have probed the H-alpha kinematics of star-forming galaxies at similar redshift. The galaxies are compact, with half-light radii of < 2 kpc, and ~50% show evidence for multiple structures or asymmetries in the WFC3 imaging. Based on the line velocity dispersions and the location of the galaxies on BPT diagnostic plots, there is little evidence for significant AGN contribution to most emission-line galaxies at 2.

  15. Chemical properties in the most distant radio galaxy

    NASA Astrophysics Data System (ADS)

    Matsuoka, K.; Nagao, T.; Maiolino, R.; Marconi, A.; Taniguchi, Y.

    2011-08-01

    We present a deep optical spectrum of TN J0924-2201, the most distant radio galaxy at z = 5.19, obtained with FOCAS on the Subaru Telescope. We successfully detect, for the first time, the C ivλ1549 emission line from the narrow-line region. In addition to the emission-line fluxes of Lyα and C iv, we set upper limits on the N v and He ii emissions. We use these line detections and upper limits to constrain the chemical properties of TN J0924-2201. By comparing the observed emission-line flux ratios with photoionization models, we infer that the carbon-to-oxygen relative abundance is already [C/O] > -0.5 at a cosmic age of ~1.1 Gyr. This lower limit on [C/O] is higher than the ratio expected at the earliest phases of the galaxy chemical evolution, indicating that TN J0924-2201 has already experienced significant chemical evolution at z = 5.19.

  16. Investigating star formation properties of galaxies in massive clusters with Herschel and ALMA

    NASA Astrophysics Data System (ADS)

    Wu, John F.; Baker, Andrew J.; Aguirre, Paula; Barkats, D.; Halpern, Mark; Hilton, Matt; Hughes, John Patrick; Infante, Leopoldo; Lindner, Robert; Marriage, Tobias; Menanteau, Felipe; Sifon, Cristobal; Weiss, Axel; ACT Collaboration

    2016-01-01

    I will present results from an investigation of star formation properties of galaxies residing in two massive z ~ 1 clusters (including the 'El Gordo' merger) that were initially selected via their Sunyaev-Zeldovich decrements by the Atacama Cosmology Telescope (ACT) southern survey. This study uses new Herschel Space Observatory and Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 observations, which provide information about the dust and cold gas content of galaxies in our targeted clusters. We have detected CO (4-3) and [CI] in individual star-forming cluster galaxies, and also measured stacked continuum and spectral line fluxes at long (e.g., far-infrared, submillimeter, and radio) wavelengths. We use these results to explore the relations between star formation and local environment and cluster dynamical state.This work has been supported by (i) an award issued by JPL/Caltech in association with Herschel, which is a European Space Agency Cornerstone Mission with significant participation by NASA, and (ii) the National Science Foundation through award GSSP SOSPA2-018 from the National Radio Astronomy Observatory, which is operated under cooperative agreement by Associated Universities, Inc.

  17. VizieR Online Data Catalog: OmegaWINGS local clusters of galaxies redshifts (Moretti+, 2017)

    NASA Astrophysics Data System (ADS)

    Moretti, A.; Gullieuszik, M.; Poggianti, B.; Paccagnella, A.; Couch, W. J.; Vulcani, B.; Bettoni, D.; Fritz, J.; Cava, A.; Fasaano, G.; D'Onofrio, M.; Omizzolo, A.

    2017-02-01

    Redshifts, magnitude/radial completeness, and memberships are given for the 17985 galaxies observed as part of the OmegaWINGS survey of local clusters of galaxies over 1 square degree. Redshifts have been measured using both absorption and emission lines features. The sample magnitude completeness is 80% at V=20. Thanks to the observing strategy, the radial completeness turned out to be relatively constant (90%) within the AAOmega field of view. The success rate in measuring redshifts is 95%, at all radii. Cluster members are flagged 1 or 2, depending on the cluster structure/secondary structure, and 0 if they are not cluster members. (1 data file).

  18. RR Lyrae stars in local group galaxies. II. NGC 147

    SciTech Connect

    Saha, A.; Hoessel, J.G.; Mossman, A.E. Space Telescope Science Institute, Baltimore, MD Washburn Observatory, Madison, WI )

    1990-07-01

    Deep CCD images of NGC 147 taken with the 4-shooter on the Hale 5 m telescope have been processed to find and photometrically measure RR Lyrae stars. 36 variable stars have been found, of which 32 are surmised to be RR Lyrae stars. Finding charts, periods, and light curves are presented. The mean magnitude of the RR Lyraes is determined to be 25.25 mag. A distance modulus 23.92 is derived, based on the best currently available values of foreground extinction and mean absolute magnitudes of RR Lyrae stars. A wide range of periods is seen for the RR Lyrae stars, indicating a correspondingly wide range of metallicities for the stars in NGC 147. The distance modulus derived here places NGC 147 at a distance of 154 kpc from the center of M31, and in conjunction with the line sight velocities of these two galaxies, this implies a lower limit of 7.2 x 10 to the 11th solar masses for the mass of M31. 23 refs.

  19. The Local Group: Our Galactic Neighborhood.

    ERIC Educational Resources Information Center

    Hodge, Paul

    1987-01-01

    Presents information on the properties and largest spirals of the Local Group galaxies. Explains the three categories of galaxies, identifies the brightest members of the Local Group, and discusses recent discoveries within the group. (ML)

  20. The Herschel Exploitation of Local Galaxy Andromeda (HELGA). IV. Dust scaling relations at sub-kpc resolution

    NASA Astrophysics Data System (ADS)

    Viaene, S.; Fritz, J.; Baes, M.; Bendo, G. J.; Blommaert, J. A. D. L.; Boquien, M.; Boselli, A.; Ciesla, L.; Cortese, L.; De Looze, I.; Gear, W. K.; Gentile, G.; Hughes, T. M.; Jarrett, T.; Karczewski, O. Ł.; Smith, M. W. L.; Spinoglio, L.; Tamm, A.; Tempel, E.; Thilker, D.; Verstappen, J.

    2014-07-01

    Context. Dust and stars play a complex game of interactions in the interstellar medium and around young stars. The imprints of these processes are visible in scaling relations between stellar characteristics, star formation parameters, and dust properties. Aims: In the present work, we aim to examine dust scaling relations on a sub-kpc resolution in the Andromeda galaxy (M 31). The goal is to investigate the properties of M 31 on both a global and local scale and compare them to other galaxies of the local universe. Methods: New Herschel observations are combined with available data from GALEX, SDSS, WISE, and Spitzer to construct a dataset covering UV to submm wavelengths. All images were brought to the beam size and pixel grid of the SPIRE 500 μm frame. This divides M 31 in 22 437 pixels of 36 arcseconds in size on the sky, corresponding to physical regions of 137 × 608 pc in the galaxy's disk. A panchromatic spectral energy distribution was modelled for each pixel and maps of the physical quantities were constructed. Several scaling relations were investigated, focussing on the interactions of dust with starlight. Results: We find, on a sub-kpc scale, strong correlations between Mdust/M⋆ and NUV-r, and between Mdust/M⋆ and μ⋆ (the stellar mass surface density). Striking similarities with corresponding relations based on integrated galaxies are found. We decompose M 31 in four macro-regions based on their far-infrared morphology; the bulge, inner disk, star forming ring, and the outer disk region. In the scaling relations, all regions closely follow the galaxy-scale average trends and behave like galaxies of different morphological types. The specific star formation characteristics we derive for these macro-regions give strong hints of an inside-out formation of the bulge-disk geometry, as well as an internal downsizing process. Within each macro-region, however, a great diversity in individual micro-regions is found, regardless of the properties of the

  1. The MOSDEF Survey: AGN Multi-wavelength Identification, Selection Biases, and Host Galaxy Properties

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR, and optically selected active galactic nuclei (AGNs) at 1.4< z< 3.8. We obtain rest-frame optical spectra of galaxies and AGNs and use the BPT diagram to identify optical AGNs. We examine the uniqueness and overlap of the AGNs identified at different wavelengths. There is a strong bias against identifying AGNs at any wavelength in low-mass galaxies, and an additional bias against identifying IR AGNs in the most massive galaxies. AGN hosts span a wide range of star formation rates (SFRs), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we find (at ∼2–3σ significance) that IR AGNs are in less dusty galaxies with relatively higher SFR and optical AGNs in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at lower redshifts. Within star-forming galaxies, once selection biases are accounted for, we find AGNs in galaxies with similar physical properties as inactive galaxies, with no evidence for AGN activity in particular types of galaxies. This is consistent with AGNs being fueled stochastically in any star-forming host galaxy. We do not detect a significant correlation between SFR and AGN luminosity for individual AGN hosts, which may indicate the timescale difference between the growth of galaxies and their supermassive black holes.

  2. Stellar mass and color dependence of the three-point correlation function of galaxies in the local universe

    SciTech Connect

    Guo, Hong; Li, Cheng; Jing, Y. P.; Börner, Gerhard

    2014-01-10

    The three-point correlation function (3PCF) for galaxies provides an opportunity to measure the non-Gaussianity generated from nonlinear structure formation and also probes information about galaxy formation and evolution that is generally not available from the two-point correlation function (2PCF). We measure the 3PCF of the Sloan Digital Sky Survey DR7 main sample galaxies in both redshift and projected spaces on scales up to 40 h {sup –1} Mpc. We explore the dependence of the 3PCF on galaxy stellar mass and color in order to constrain the formation and evolution for galaxies of different properties. The study of the dependence on these properties also helps better constrain the relation between galaxy stellar mass and color and the properties of their hosting dark-matter halos. We focus on the study of the reduced 3PCF, Q, defined as the ratio between the 3PCF and the sum of the products of the 2PCFs. We find a very weak stellar-mass dependence of Q in both redshift and projected spaces. On small scales, more massive galaxies tend to have slightly higher amplitudes of Q. The shape dependence of Q is also weak on these small scales, regardless of stellar mass and color. The reduced 3PCF has a strong color dependence for the low-mass galaxies, while no significant dependence on color is found for the high-mass galaxies. Low-mass red galaxies have higher amplitudes and stronger shape dependence of the reduced 3PCF than the blue galaxies, implying that these low-mass red galaxies tend to populate filamentary structures. The linear galaxy bias model fails to interpret the color dependence of Q, emphasizing the importance of a nonvanishing quadratic bias parameter in the correct modeling of the galaxy color distribution.

  3. The photometric properties of galaxies in the early Universe

    NASA Astrophysics Data System (ADS)

    Wilkins, Stephen M.; Feng, Yu; Di-Matteo, Tiziana; Croft, Rupert; Stanway, Elizabeth R.; Bunker, Andrew; Waters, Dacen; Lovell, Christopher

    2016-08-01

    We use the large cosmological hydro-dynamic simulation BLUETIDES to predict the photometric properties of galaxies during the epoch of reionization (z = 8-15). These properties include the rest-frame UV to near-IR broad-band spectral energy distributions, the Lyman continuum (LyC) photon production, the UV star formation rate calibration, and intrinsic UV continuum slope. In particular we focus on exploring the effect of various modelling assumptions, including the assumed choice of stellar population synthesis (SPS) model, initial mass function, and the escape fraction of LyC photons, upon these quantities. We find that these modelling assumptions can have a dramatic effect on photometric properties leading to consequences for the accurate determination of physical properties from observations. For example, at z = 8 we predict that nebular emission can account for up to 50 per cent of the rest-frame R-band luminosity, while the choice of SPS model can change the LyC production rate up to a factor of ×2.

  4. Friends-of-friends galaxy group finder with membership refinement. Application to the local Universe

    NASA Astrophysics Data System (ADS)

    Tempel, E.; Kipper, R.; Tamm, A.; Gramann, M.; Einasto, M.; Sepp, T.; Tuvikene, T.

    2016-04-01

    Context. Groups form the most abundant class of galaxy systems. They act as the principal drivers of galaxy evolution and can be used as tracers of the large-scale structure and the underlying cosmology. However, the detection of galaxy groups from galaxy redshift survey data is hampered by several observational limitations. Aims: We improve the widely used friends-of-friends (FoF) group finding algorithm with membership refinement procedures and apply the method to a combined dataset of galaxies in the local Universe. A major aim of the refinement is to detect subgroups within the FoF groups, enabling a more reliable suppression of the fingers-of-God effect. Methods: The FoF algorithm is often suspected of leaving subsystems of groups and clusters undetected. We used a galaxy sample built of the 2MRS, CF2, and 2M++ survey data comprising nearly 80 000 galaxies within the local volume of 430 Mpc radius to detect FoF groups. We conducted a multimodality check on the detected groups in search for subgroups. We furthermore refined group membership using the group virial radius and escape velocity to expose unbound galaxies. We used the virial theorem to estimate group masses. Results: The analysis results in a catalogue of 6282 galaxy groups in the 2MRS sample with two or more members, together with their mass estimates. About half of the initial FoF groups with ten or more members were split into smaller systems with the multimodality check. An interesting comparison to our detected groups is provided by another group catalogue that is based on similar data but a completely different methodology. Two thirds of the groups are identical or very similar. Differences mostly concern the smallest and largest of these other groups, the former sometimes missing and the latter being divided into subsystems in our catalogue. The catalogues are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  5. VizieR Online Data Catalog: Properties of SN host galaxies (Kelly+, 2014)

    NASA Astrophysics Data System (ADS)

    Kelly, P. L.; Filippenko, A. V.; Modjaz, M.; Kocevski, D.

    2017-03-01

    We study the host galaxies of both nearby (z<0.2) core-collapse SNe discovered by "galaxy-untargeted" transient searches (e.g., the Palomar Transient Factory (PTF); Rau et al., 2009PASP..121.1334R; Law et al., 2009PASP..121.1395L), which do not target specific potential hosts or z<1.2 LGRBs detected by gamma-ray satellites. We use the SDSS spectroscopic sample to build a control sample of low-redshift star-forming galaxies and SDSS photometry and spectroscopy to measure properties of both the sample of low-redshift star-forming galaxies and the host galaxies of the nearby SNe. For the host galaxies of z<1.2 LGRBs, we estimate host properties using published photometry and HST imaging. (2 data files).

  6. Local Effect of Space-Time Expansion ---- How Galaxies Form and Evolve

    NASA Astrophysics Data System (ADS)

    Yang, Jian Liang; Hua, He Yu

    2016-09-01

    generalize gravitational theory of central field to the expanding space-time, and realize the unification of structure of big scope space-time and physical phenomena of small scope, and reasonably and systematically explain gravitational anomalies of solar system such as extra receding rate of lunar orbit, the increase of astronomical unit, the secular change of day length, the earth's expansion as well as the extra acceleration of artificial aerocrafts and so on, which cannot be treated by current knowledge. Besides, it is disclosed that galaxies form from continued growth but not the assemblage of existent matter after big bang, new matter continuously creates in the interior of celestial bodies, celestial bodies, galaxies and space simultaneously enlarge at the same proportion, and it is the local effect of space-time expansion that determines formation and evolution of galaxies.

  7. On the recovery of the local group motion from galaxy redshift surveys

    SciTech Connect

    Nusser, Adi; Davis, Marc; Branchini, Enzo E-mail: mdavis@berkeley.edu

    2014-06-20

    There is an ∼150 km s{sup –1} discrepancy between the measured motion of the Local Group (LG) of galaxies with respect to the cosmic microwave background and the linear theory prediction based on the gravitational force field of the large-scale structure in full-sky redshift surveys. We perform a variety of tests which show that the LG motion cannot be recovered to better than 150-200 km s{sup –1} in amplitude and within ≈10° in direction. The tests rely on catalogs of mock galaxies identified in the Millennium simulation using semi-analytic galaxy formation models. We compare these results to the K{sub s} = 11.75 Two-Mass Galaxy Redshift Survey, which provides the deepest and most complete all-sky spatial distribution of galaxies with spectroscopic redshifts available thus far. In our analysis, we use a new concise relation for deriving the LG motion and bulk flow from the true distribution of galaxies in redshift space. Our results show that the main source of uncertainty is the small effective depth of surveys like the Two-Mass Redshift Survey (2MRS), which prevents a proper sampling of the large-scale structure beyond ∼100 h {sup –1} Mpc. Deeper redshift surveys are needed to reach the 'convergence scale' of ≈250 h {sup –1} Mpc in a ΛCDM universe. Deeper surveys would also mitigate the impact of the 'Kaiser rocket' which, in a survey like 2MRS, remains a significant source of uncertainty. Thanks to the quiet and moderate density environment of the LG, purely dynamical uncertainties of the linear predictions are subdominant at the level of ∼90 km s{sup –1}. Finally, we show that deviations from linear galaxy biasing and shot noise errors provide a minor contribution to the total error budget.

  8. On the Recovery of the Local Group Motion from Galaxy Redshift Surveys

    NASA Astrophysics Data System (ADS)

    Nusser, Adi; Davis, Marc; Branchini, Enzo

    2014-06-01

    There is an ~150 km s-1 discrepancy between the measured motion of the Local Group (LG) of galaxies with respect to the cosmic microwave background and the linear theory prediction based on the gravitational force field of the large-scale structure in full-sky redshift surveys. We perform a variety of tests which show that the LG motion cannot be recovered to better than 150-200 km s-1 in amplitude and within ≈10° in direction. The tests rely on catalogs of mock galaxies identified in the Millennium simulation using semi-analytic galaxy formation models. We compare these results to the Ks = 11.75 Two-Mass Galaxy Redshift Survey, which provides the deepest and most complete all-sky spatial distribution of galaxies with spectroscopic redshifts available thus far. In our analysis, we use a new concise relation for deriving the LG motion and bulk flow from the true distribution of galaxies in redshift space. Our results show that the main source of uncertainty is the small effective depth of surveys like the Two-Mass Redshift Survey (2MRS), which prevents a proper sampling of the large-scale structure beyond ~100 h -1 Mpc. Deeper redshift surveys are needed to reach the "convergence scale" of ≈250 h -1 Mpc in a ΛCDM universe. Deeper surveys would also mitigate the impact of the "Kaiser rocket" which, in a survey like 2MRS, remains a significant source of uncertainty. Thanks to the quiet and moderate density environment of the LG, purely dynamical uncertainties of the linear predictions are subdominant at the level of ~90 km s-1. Finally, we show that deviations from linear galaxy biasing and shot noise errors provide a minor contribution to the total error budget.

  9. Far-infrared properties of Markarian galaxies with multiple nuclei - Warm dust emission in mergers

    NASA Technical Reports Server (NTRS)

    Mazzarella, Joseph M.; Bothun, Gregory D.; Boroson, Todd A.

    1991-01-01

    An investigation of coadded IRAS data is performed on 187 Markarian galaxies where distinguishing morphological characteristics or multiple optical nuclei are present. The far-IR properties of Markarian galaxies are compared to the IRAS Bright Galaxy Sample, and a much higher median dust temperature is found in the multiple nucleus galaxies, suggesting that more far-IR luminosity results from active star formation. Both optical/UV and far-IR selection techniques are necessary to extract complete samples of AGNs since the far-IR two-color plane can miss up to 50 percent of the galaxies. A systematic increase in the contribution of warm dust emission due to active star formation and AGNs is found in a statistical comparison of merger candidates and other galaxy samples. The assumed nature of precursor galaxies determines the assumed enhancement of far-IR luminosity caused by galaxy collisions. A model is presented which describes the properties of the Markarian galaxies in terms of enhanced OB star formation and different grain size distributions. The results of the investigation are shown to be consistent with a 'subdued' interpretation of merging galaxies with high luminosities.

  10. VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

    NASA Astrophysics Data System (ADS)

    Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

    We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

  11. HUBBLE SPACE TELESCOPE Observations of the Local Group Dwarf Galaxy Leo I

    NASA Astrophysics Data System (ADS)

    Gallart, Carme; Freedman, Wendy L.; Mateo, Mario; Chiosi, Cesare; Thompson, Ian B.; Aparicio, Antonio; Bertelli, Gianpaolo; Hodge, Paul W.; Lee, Myung G.; Olszewski, Edward W.; Saha, Abhijit; Stetson, Peter B.; Suntzeff, Nicholas B.

    1999-04-01

    We present deep HST F555W (V) and F814W (I) observations of a central field in the Local Group dwarf spheroidal (dSph) galaxy Leo I. The resulting color-magnitude diagram (CMD) reaches I~=26 and reveals the oldest ~=10-15 Gyr old turnoffs. Nevertheless, a horizontal branch is not obvious in the CMD. Given the low metallicity of the galaxy, this likely indicates that the first substantial star formation in the galaxy may have been somehow delayed in Leo I in comparison with the other dSph satellites of the Milky Way. The subgiant region is well and uniformly populated from the oldest turnoffs up to the 1 Gyr old turnoff, indicating that star formation has proceeded in a continuous way, with possible variations in intensity but no big gaps between successive bursts, over the galaxy's lifetime. The structure of the red clump of core He-burning stars is consistent with the large amount of intermediate-age population inferred from the main sequence and the subgiant region. In spite of the lack of gas in Leo I, the CMD clearly shows star formation continuing until 1 Gyr ago and possibly until a few hundred Myr ago in the central part of the galaxy.

  12. A LOCAL BASELINE OF THE BLACK HOLE MASS SCALING RELATIONS FOR ACTIVE GALAXIES. II. MEASURING STELLAR VELOCITY DISPERSION IN ACTIVE GALAXIES

    SciTech Connect

    Harris, Chelsea E.; Bennert, Vardha N.; Auger, Matthew W.; Treu, Tommaso; Woo, Jong-Hak; Malkan, Matthew A. E-mail: mauger@physics.ucsb.edu E-mail: vbennert@calpoly.edu E-mail: malkan@astro.ucla.edu

    2012-08-01

    We derive spatially resolved stellar kinematics for a sample of 84 out of 104 observed local (0.02 < z < 0.09) galaxies hosting type-1 active galactic nuclei (AGNs), based on long-slit spectra obtained at the 10 m W. M. Keck-1 Telescope. In addition to providing central stellar velocity dispersions, we measure major axis rotation curves and velocity dispersion profiles using three separate wavelength regions, including the prominent Ca H and K, Mg Ib, and Ca II NIR stellar features. In this paper, we compare kinematic measurements of stellar velocity dispersion obtained for different apertures, wavelength regions, and signal-to-noise ratios, and provide recipes to cross-calibrate the measurements reducing systematic effects to the level of a few percent. We also provide simple recipes based on readily observable quantities such as global colors and Ca H and K equivalent width that will allow observers of high-redshift AGN hosts to increase the probability of obtaining reliable stellar kinematic measurements from unresolved spectra in the region surrounding the Ca H and K lines. In subsequent papers in this series, we will combine this unprecedented spectroscopic data set with surface photometry and black hole mass measurements to study in detail the scaling relations between host galaxy properties and black hole mass.

  13. Improved system for object detection and star/galaxy classification via local subspace analysis.

    PubMed

    Liu, Zhi-Yong; Chiu, Kai-Chun; Xu, Lei

    2003-01-01

    The two traditional tasks of object detection and star/galaxy classification in astronomy can be automated by neural networks because the nature of the problems is that of pattern recognition. A typical existing system can be further improved by using one of the local Principal Component Analysis (PCA) models. Our analysis in the context of object detection and star/galaxy classification reveals that local PCA is not only superior to global PCA in feature extraction, but is also superior to gaussian mixture in clustering analysis. Unlike global PCA which performs PCA for the whole data set, local PCA applies PCA individually to each cluster of data. As a result, local PCA often outperforms global PCA for data of multi-modes. Moreover, since local PCA can effectively avoid the trouble of having to specify a large number of free elements of each covariance matrix of gaussian mixture, it can give a better description of local subspace structures of each cluster when applied on high dimensional data with small sample size. In this paper, the local PCA model proposed by Xu [IEEE Trans. Neural Networks 12 (2001) 822] under the general framework of Bayesian Ying Yang (BYY) normalization learning will be adopted. Endowed with the automatic model selection ability of BYY learning, the BYY normalization learning-based local PCA model can cope with those object detection and star/galaxy classification tasks with unknown model complexity. A detailed algorithm for implementation of the local PCA model will be proposed, and experimental results using both synthetic and real astronomical data will be demonstrated.

  14. Molecular Gas and Star Formation in Local Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Bureau, M.; Davis, T. A.; Alatalo, K.; Crocker, A. F.; Blitz, L.; Young, L. M.; Combes, F.; Bois, M.; Bournaud, F.; Cappellari, M.; Davies, R. L.; de Zeeuw, P. T.; Duc, P.-A.; Emsellem, E.; Khochfar, S.; Krajnović, D.; Kuntschner, H.; Lablanche, P.-Y.; McDermid, R. M.; Morganti, R.; Naab, T.; Oosterloo, T.; Sarzi, M.; Scott, N.; Serra, P.; Weijmans, A.

    2011-12-01

    The molecular gas content of local early-type galaxies is constrained and discussed in relation to their evolution. First, as part of the ATLAS3D survey, we present the first complete, large (260 objects), volume-limited single-dish survey of CO in normal local early-type galaxies. We find a surprisingly high detection rate of 22%, independent of luminosity and at best weakly dependent on environment. Second, the extent of the molecular gas is constrained with CO synthesis imaging, and a variety of morphologies is revealed. The kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in over a third of the systems, although this behaviour is drastically diffferent between field and cluster environments. Third, many objects appear to be in the process of forming regular kpc-size decoupled disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Last, early-type galaxies do not seem to systematically obey all our usual prejudices regarding star formation, following the standard Schmidt-Kennicutt law but not the far infrared-radio correlation. This may suggest a greater diversity in star formation processes than observed in disk galaxies. Using multiple molecular tracers, we are thus starting to probe the physical conditions of the cold gas in early-types.

  15. A multiwavelength and multiscale study of Luminous and Ultraluminous Infrared Galaxies in the local Universe

    NASA Astrophysics Data System (ADS)

    Herrero-Illana, Rubén

    2014-10-01

    This dissertation deals with the multiwavelength study of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs, respectively) in the local Universe under different spatial scales. The work is focused on the properties of massive starbursts, the contribution of active galactic nuclei (AGN) and the interplay between both phenomena. The study of local (U)LIRGs is the best scenario where to understand the properties of these objects at cosmological distances, where their luminosity contribution dominates the cosmic infrared background. Our first approach to the study of (U)LIRGs consisted of a spectral line study in the millimeter range, obtained with the IRAM 30m radio-telescope in Pico Veleta, Granada of a subsample of 56 (U)LIRGs from the GOALS project sample. We observed and analyzed spectra of several molecular features, focusing in the study of carbon monoxide (CO), a well-known tracer of cold molecular gas. We explored the relation between them as well as the properties of molecular gas. Besides of the sample characterization, we confirmed the increase of the isotopic ratio 12CO/13CO with the dust temperature, explained by the 12CO optical depth decreasing with temperature. We have also studied the kinematics and gas distribution using the spectral profiles of several molecular transitions. In a second part of this thesis, we analyzed the central kiloparsec region of a sample of 12 LIRGs, stressing the importance of the multiwavelength approach, aimed at deriving the star formation processes of these galaxies, as well as to study the contribution of the putative AGN to the bolometric luminosity in our sample. For one of these LIRGs, NGC1614, we performed a deep multiwavelength study, including data from radio, infrared, optical and X-rays. These data allowed us to establish that the the IR emission in the circumnuclear region is completely dominated by a powerful starburst and, in case it hosts an AGN, its contribution is irrelevant. We also performed

  16. Computational analysis of local membrane properties

    NASA Astrophysics Data System (ADS)

    Gapsys, Vytautas; de Groot, Bert L.; Briones, Rodolfo

    2013-10-01

    In the field of biomolecular simulations, dynamics of phospholipid membranes is of special interest. A number of proteins, including channels, transporters, receptors and short peptides are embedded in lipid bilayers and tightly interact with phospholipids. While the experimental measurements report on the spatial and/or temporal average membrane properties, simulation results are not restricted to the average properties. In the current study, we present a collection of methods for an efficient local membrane property calculation, comprising bilayer thickness, area per lipid, deuterium order parameters, Gaussian and mean curvature. The local membrane property calculation allows for a direct mapping of the membrane features, which subsequently can be used for further analysis and visualization of the processes of interest. The main features of the described methods are highlighted in a number of membrane systems, namely: a pure dimyristoyl-phosphatidyl-choline (DMPC) bilayer, a fusion peptide interacting with a membrane, voltage-dependent anion channel protein embedded in a DMPC bilayer, cholesterol enriched bilayer and a coarse grained simulation of a curved palmitoyl-oleoyl-phosphatidyl-choline lipid membrane. The local membrane property analysis proves to provide an intuitive and detailed view on the observables that are otherwise interpreted as averaged bilayer properties.

  17. Galaxy clusters in visible light (I): catalogues, large-scale distribution, and general properties.

    NASA Astrophysics Data System (ADS)

    Bian, Yulin

    1995-12-01

    While the nature, behaviour, and evolution of galaxy clusters is a such wide research field, only some of their optical properties are underlined in the present review. The whole article is divided into two parts, of which this is the first one, contributed to cluster catalogues, large-scale distribution, and some general characteristics of galaxy clusters.

  18. TESTING FOR A LARGE LOCAL VOID BY INVESTIGATING THE NEAR-INFRARED GALAXY LUMINOSITY FUNCTION

    SciTech Connect

    Keenan, R. C.; Wang, W.-H.; Barger, A. J.; Wold, I.; Cowie, L. L.; Trouille, L.

    2012-08-01

    Recent cosmological modeling efforts have shown that a local underdensity on scales of a few hundred Mpc (out to z {approx} 0.1) could produce the apparent acceleration of the expansion of the universe observed via Type Ia supernovae. Several studies of galaxy counts in the near-infrared (NIR) have found that the local universe appears underdense by {approx}25%-50% compared with regions a few hundred Mpc distant. Galaxy counts at low redshifts sample primarily L {approx} L* galaxies. Thus, if the local universe is underdense, then the normalization of the NIR galaxy luminosity function (LF) at z > 0.1 should be higher than that measured for z < 0.1. Here we present a highly complete (>90%) spectroscopic sample of 1436 galaxies selected in the H band (1.6 {mu}m) to study the normalization of the NIR LF at 0.1 < z < 0.3 and address the question of whether or not we reside in a large local underdensity. Our survey sample consists of all galaxies brighter than 18th magnitude in the H band drawn from six widely separated fields at high Galactic latitudes, which cover a total of {approx}2 deg{sup 2} on the sky. We find that for the combination of our six fields, the product {phi}*L* at 0.1 < z < 0.3 is {approx}30% higher than that measured at lower redshifts. While our statistical errors in this measurement are on the {approx}10% level, we find the systematics due to cosmic variance may be larger still. We investigate the effects of cosmic variance on our measurement using the COSMOS cone mock catalogs from the Millennium Simulation and recent empirical estimates of cosmic variance. We find that our survey is subject to systematic uncertainties due to cosmic variance at the 15% level (1{sigma}), representing an improvement by a factor of {approx}2 over previous studies in this redshift range. We conclude that observations cannot yet rule out the possibility that the local universe is underdense at z < 0.1. The fields studied in this work have a large amount of publicly

  19. 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

  20. Optical Properties of Radio-Selected Narrow Line Seyfert 1 Galaxies

    SciTech Connect

    Whalen, J; Laurent-Muehleisen, S A; Moran, E C; Becker, R H

    2006-01-05

    We present results from the analysis of the optical spectra of 47 radio-selected narrow-line Seyfert 1 galaxies (NLS1s). These objects are a subset of the First Bright Quasar Survey (FBQS) and were initially detected at 20 cm (flux density limit {approx} 1 mJy) in the VLA FIRST Survey. We run Spearman rank correlation tests on several sets of parameters and conclude that, except for their radio properties, radio-selected NLS1 galaxies do not exhibit significant differences from traditional NLS1 galaxies. Our results are also in agreement with previous studies suggesting that NLS1 galaxies have small black hole masses that are accreting very close to the Eddington rate. We have found 16 new radio-loud NLS1 galaxies, which increases the number of known radio-loud NLS1 galaxies by a factor of {approx} 5.

  1. Galaxies and the Universe: Properties of the universe are revealed by the rotation of galaxies and their distribution in space.

    PubMed

    Oort, J H

    1970-12-25

    A brief review is given of what the study of galaxies has taught us about properties of the universe. It is assumed that the universe started from a general "explosion," and that the general expansion observed today, as well as the 3 degrees K blackbody radiation, are consequences of this explosion. The present average density in the universe is probably close to the critical value of 10(-29) g/cm(3). Only about 3 percent of this is contained in galaxies; the rest consists probably of intergalactic gas at a temperature between 10(5) and 10(6) degrees K. Observations in our own galaxy indicate that this intergalactic gas is still flowing into it.

  2. Is the Pegasus Dwarf Galaxy a Member of the Local Group?

    NASA Astrophysics Data System (ADS)

    Lee, Myung Gyoon

    1995-10-01

    Deep VI CCD photometry of the Pegasus dwarf irregular galaxy shows that tip of the red giant branch (RGB) is located at I = 21.15+-0.10 mag and (V-I) = 1.58+-0.03. Using the I magnitude of the tip of the RGB(TRGB), the distance modulus of the Pegasus galaxy is estimated to be (m-M)o = 25.13+-0.11 mag(corresponding to a distance of d = 1060+-50kpc). This result is in a good agreement with the recent distance estimate based on the TRGB method by Aparicio[1994, ApJ, 437, L27], (m-M)o = 24.9 (d = 950kpc). However, our distance estimate is much smaller than that based on the Cepheid variable candidates by Hoessel et al.[1990, AJ, 100, 1151], (m-M)o = 26.22+-0.20(d = 1750+-160 kpc) mag. The color-magnitude diagram illustrates that the Cepheid candidates used by Hoessel et al. are not located in the Cepheid instability strip, but in the upper part of the giant branch. This result shows that the Cepheid candidates studied by Hoessel et al. are probably not Cepheids, but other types of variable stars. Taking the average of our distance estimate and Aparicio's, the distance to the Pegasus galaxy is d = 1000+-80 kpc. Considering the distance and velocity of the Pegasus galaxy with respect to the center of the Local Group, we conclude that the Pegasus galaxy is probably a member of the Local Group.

  3. Physical properties of galaxies: towards a consistent comparison between hydrodynamical simulations and SDSS

    NASA Astrophysics Data System (ADS)

    Guidi, Giovanni; Scannapieco, Cecilia; Walcher, Jakob; Gallazzi, Anna

    2016-10-01

    We study the effects of applying observational techniques to derive the properties of simulated galaxies, with the aim of making an unbiased comparison between observations and simulations. For our study, we used 15 galaxies simulated in a cosmological context using three different feedback and chemical enrichment models, and compared their z = 0 properties with data from the Sloan Digital Sky Survey (SDSS). We show that the physical properties obtained directly from the simulations without post-processing can be very different from those obtained mimicking observational techniques. In order to provide simulators a way to reliably compare their galaxies with SDSS data, for each physical property that we studied - colours, magnitudes, gas and stellar metallicities, mean stellar ages and star formation rates - we give scaling relations that can be easily applied to the values extracted from the simulations; these scalings have in general a high correlation, except for the gas oxygen metallicities. Our simulated galaxies are photometrically similar to galaxies in the blue sequence/green valley, but in general they appear older, passive and with lower metal content compared to most of the spirals in SDSS. As a careful assessment of the agreement/disagreement with observations is the primary test of the baryonic physics implemented in hydrodynamical codes, our study shows that considering the observational biases in the derivation of the galaxies' properties is of fundamental importance to decide on the failure/success of a galaxy formation model.

  4. The Properties of the Dense Gas in the Nuclei of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Paglione, Timothy A. D.

    1997-01-01

    The properties of the star-forming clouds in galactic nuclei are largely unknown, and no clear explanation exists for the origin and evolution of starburst galaxies-galaxies with unusually high star formation rates. My goal is to determine the relation between the interstellar cloud properties in galaxies and their star formation activity by estimating the gas densities in starburst galaxies and comparing them to those of normal galaxies and the Milky Way. I perform three programs: observing the emission from dense gas in galaxies, wide-field mapping of the Milky Way, and millimeter-wave interferometry of starburst galaxies. In starburst galaxies, I map the millimeter- and submillimeter-wave emission from molecules that require high densities for excitation, such as hydrogen cyanide and carbon monosulfide. This emission is closely tied to star forming regions. I find that the densest clouds lie within several hundred parsecs of starburst nuclei, and the star formation efficiency of a galaxy is correlated with its average gas density. Unfortunately, the spatial resolution of most observations of galaxies is poor, but comparing different sources properly requires examining them on similar spatial scales. Therefore, to compare the gas properties of starburst galaxies and the Milky Way, I utilize innovations at millimeter-wave telescopes to map the large-scale emission from dense gas in the Milky Way. I find that dense gas comprises a higher fraction of the molecular mass in starburst galaxies than in the Milky Way. Further, the density derived from the averaged spectra of the Milky Way equals the mean density found from modeling each map position. Therefore, analyses of this type probe the average gas properties in galaxies. Finally, I use millimeter-wave interferometry to examine dense gas in starburst galaxies on the spatial scales of individual cloud complexes. I find that dense clouds in starburst galaxies are associated with star-forming regions, and some clouds

  5. THE STELLAR-TO-HALO MASS RELATION OF LOCAL GALAXIES SEGREGATES BY COLOR

    SciTech Connect

    Rodríguez-Puebla, Aldo; Yang, Xiaohu; Foucaud, Sebastien; Jing, Y. P.; Avila-Reese, Vladimir; Drory, Niv

    2015-02-01

    By means of a statistical approach that combines different semi-empirical methods of galaxy-halo connection, we derive the stellar-to-halo mass relations (SHMR) of local blue and red central galaxies. We also constrain the fraction of halos hosting blue/red central galaxies and the occupation statistics of blue and red satellites as a function of halo mass, M {sub h}. For the observational input we use the blue and red central/satellite galaxy stellar mass functions and two-point correlation functions in the stellar mass range of 9 < log(M {sub *}/M {sub ☉}) <12. We find that: (1) the SHMR of central galaxies is segregated by color, with blue centrals having a SHMR above that of red centrals; at log(M {sub h}/M {sub ☉}) ∼12, the M {sub *}-to-M {sub h} ratio of the blue centrals is ≈0.05, which is ∼1.7 times larger than the value of red centrals. (2) The constrained scatters around the SHMRs of red and blue centrals are ≈0.14 and ≈0.11 dex, respectively. The scatter of the average SHMR of all central galaxies changes from ∼0.20 dex to ∼0.14 dex in the 11.3 < log(M {sub h}/M {sub ☉}) <15 range. (3) The fraction of halos hosting blue centrals at M{sub h}=10{sup 11} M {sub ☉} is 87%, but at 2 × 10{sup 12} M {sub ☉} decays to ∼20%, approaching a few percent at higher masses. The characteristic mass at which this fraction is the same for blue and red galaxies is M{sub h}≈7×10{sup 11} M {sub ☉}. Our results suggest that the SHMR of central galaxies at large masses is shaped by mass quenching. At low masses processes that delay star formation without invoking too strong supernova-driven outflows could explain the high M {sub *}-to-M {sub h} ratios of blue centrals as compared to those of the scarce red centrals.

  6. Link prediction based on local community properties

    NASA Astrophysics Data System (ADS)

    Yang, Xu-Hua; Zhang, Hai-Feng; Ling, Fei; Cheng, Zhi; Weng, Guo-Qing; Huang, Yu-Jiao

    2016-09-01

    The link prediction algorithm is one of the key technologies to reveal the inherent rule of network evolution. This paper proposes a novel link prediction algorithm based on the properties of the local community, which is composed of the common neighbor nodes of any two nodes in the network and the links between these nodes. By referring to the node degree and the condition of assortativity or disassortativity in a network, we comprehensively consider the effect of the shortest path and edge clustering coefficient within the local community on node similarity. We numerically show the proposed method provide good link prediction results.

  7. Cosmic evolution of star formation properties of galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Sungeun

    2014-01-01

    Development of bolometer array and camera at submillimeter wavelength has played an important role in detecting submillimeter bright galaxies, so called submillimeter galaxies. These galaxies seem to be progenitors of present-day massive galaxies and account for their considerable contributions to the light from the early universe and their expected high star formation rates if there is a close link between the submillimeter galaxies and the star formation activities, and the interstellar dust in galaxies is mainly heated by the star light. We review assembly of submillimeter galaxies chosen from the AzTEC and the Herschel SPIRE/PACS data archives, and investigate their spectral energy distribution fits including the data at other wavelengths to deduce details about stellar parameters including star formation rates and parameters yielding the metallicity, composition and abundance in dust, and disc structure of these galaxies. This work has been supported in part by Mid-career Researcher Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology 2011-0028001.

  8. INDIRECT EVIDENCE FOR ESCAPING IONIZING PHOTONS IN LOCAL LYMAN BREAK GALAXY ANALOGS

    SciTech Connect

    Alexandroff, Rachael M.; Heckman, Timothy M.; Borthakur, Sanchayeeta; Overzier, Roderik; Leitherer, Claus

    2015-09-10

    A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear, however, what conditions and physical processes would enable a significant fraction of the ionizing (Lyman continuum) photons to escape from these gas-rich galaxies. In this paper we present the results of the analysis of Hubble Space Telescope Cosmic Origins Spectrograph far-UV (FUV) spectroscopy plus ancillary multi-waveband data of a sample of 22 low-redshift galaxies that are good analogs to typical star-forming galaxies at high redshift. We measure three parameters that provide indirect evidence of the escape of ionizing radiation (leakiness): (1) the residual intensity in the cores of saturated interstellar low-ionization absorption lines, which indicates incomplete covering by that gas in the galaxy; (2) the relative amount of blueshifted Lyα line emission, which can indicate the existence of holes in the neutral hydrogen on the front-side of the galaxy outflow, and (3) the relative weakness of the [S ii] optical emission lines that trace matter-bounded H ii regions. We show that our residual intensity measures are only negligibly affected by infilling from resonance emission lines. We find all three diagnostics agree well with one another. We use these diagnostics to rank-order our sample in terms of likely leakiness, noting that a direct measure of escaping Lyman continuum has recently been made for one of the leakiest members of our sample. We then examine the correlations between our ranking and other proposed diagnostics of leakiness. We find a good correlation with the equivalent width of the Lyα emission line, but no significant correlations with either the flux ratio of the [O iii]/[O ii] emission lines or the ratio of star-formation rates derived from the (dust-corrected) FUV and Hα luminosities. Turning to galaxy properties, we find the strongest correlations with leakiness are with the compactness of the star

  9. Constraints on physical properties of z ~ 6 galaxies using cosmological hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Finlator, Kristian; Davé, Romeel; Oppenheimer, Benjamin D.

    2007-04-01

    We conduct a detailed comparison of broad-band spectral energy distributions of six z >~ 5.5 galaxies against galaxies drawn from cosmological hydrodynamic simulations. We employ a new tool called SPOC (Simulated photometry-derived observational constraints), which constrains the physical properties of observed galaxies through a Bayesian likelihood comparison with model galaxies. We first show that SPOC self-consistently recovers the physical properties of a test sample of high-redshift galaxies drawn from our simulations, although dust extinction can yield systematic uncertainties at the ~50 per cent level. We then use SPOC to test whether our simulations can reproduce the observed photometry of six z > 5.5 galaxies drawn from the literature. We compare physical properties derived from simulated star formation histories (SFHs) versus assuming simple models such as constant, exponentially decaying and constantly rising. For five objects, our simulated galaxies match the observations at least as well as simple SFH models, with similar favoured values obtained for the intrinsic physical parameters such as stellar mass and star formation rate, but with substantially smaller uncertainties. Our results are broadly insensitive to simulation choices for galactic outflows and dust reddening. Hence the existence of early galaxies as observed is broadly consistent with current hierarchical structure formation models. However, one of the six objects has photometry that is best fitted by a bursty SFH unlike anything produced in our simulations, driven primarily by a high K-band flux. These findings illustrate how SPOC provides a robust tool for optimally utilizing hydrodynamic simulations (or any model that predicts galaxy SFHs) to constrain the physical properties of individual galaxies having only photometric data, as well as identify objects that challenge current models.

  10. VizieR Online Data Catalog: Physical properties of VVDS galaxies (Lamareille+, 2009)

    NASA Astrophysics Data System (ADS)

    Lamareille, F.; Brinchmann, J.; Contini, T.; Walcher, C. J.; Charlot, S.; Perez-Montero, E.; Zamorani, G.; Pozzetti, L.; Bolzonella, M.; Garilli, B.; Paltani, S.; Bongiorno, A.; Le Fevre, O.; Bottini, D.; Le Brun, V.; Maccagni, D.; Scaramella, R.; Scodeggio, M.; Tresse, L.; Vettolani, G.; Zanichelli, A.; Adami, C.; Arnouts, S.; Bardelli, S.; Cappi, A.; Ciliegi, P.; Foucaud, S.; Franzetti, P.; Gavignaud, I.; Guzzo, L.; Ilbert, O.; Iovino, A.; McCracken, H. J.; Marano, B.; Marinoni, C.; Mazure, A.; Meneux, B.; Merighi, R.; Pello, R.; Pollo, A.; Radovich, M.; Vergani, D.; Zucca, E.; Romano, A.; Grado, A.; Limatola, L.

    2009-01-01

    This catalog gives emission-line measurements and spectral indices for galaxies observed in the VIMOS/VLT Deep Survery (VVDS), together with derived physical properties such as stellar masses and metallicities. (3 data files).

  11. Local dark energy: HST evidence from the vicinity of the M81/M82 galaxy group

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Karachentsev, I. D.; Kashibadze, O. G.; Makarov, D. I.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.

    2007-10-01

    The Hubble Space Telescope observations of the nearby galaxy group M81/M82 and its vicinity indicate that the dynamics of the expansion outflow around the group is dominated by the antigravity of the dark energy background. The local density of dark energy in the area is estimated to be near the global dark energy density or perhaps exactly equal to it. This conclusion agrees well with our previous results for the Local Group vicinity and the vicinity of the Cen A/M83 group.

  12. The Formation, Evolution, and Multi-Band Properties of z ˜ 6 Quasars and Their Galaxy Progenitors

    NASA Astrophysics Data System (ADS)

    Li, Y.; Hernquist, L.; Fazio, G.

    2008-10-01

    We model the formation, evolution, and multi-band properties of quasars at z ˜ 6, by combining hydrodynamic simulations (Li et al. 2007) with radiative transfer calculations using ART^2 -- All-wavelength Radiative Transfer with Adaptive Refinement Tree (Li et al. 2008). Our model shows that luminous quasars at z ˜ 6 can form through hierarchical galaxy mergers in the LCDM cosmology, and our calculations reproduce a number of observations of z ˜ 6 quasars, including the black hole masses, dust properties, and multi-wavelength SEDs and luminosities. We find that SMBHs grow via gas accretion under Eddington limit, without invoking exotic process. The quasar host obeys the Magorrian relation observed locally as a result of coeval growth of the SMBH and its host galaxy. Furthermore, the quasar systems evolve from cold to warm ULIRGs as they transform from a starburst to a quasar.

  13. Environmental Effects on the ISM and Star Formation Properties of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, Christine

    2015-08-01

    We present the results from a sample of HI flux-selected spiral galaxies within 25 Mpc from the JCMT Nearby Galaxies Legacy Survey (NGLS), subdivided into isolated, group, and Virgo cluster samples. The CO J=3-2 line was observed with the James Clerk Maxwell Telescope (JCMT), a tracer for the dense molecular gas linked to star formation. We combine the CO data with integrated star formation rates using H-alpha measurements and stellar masses from the S4G Survey in order to study the link between the gas and stars inside these galaxies. We find that while the mean atomic gas mass is lower for the Virgo galaxies compared to the isolated galaxies, the distributions of molecular gas masses are not significantly different between the three samples. The specific star formation rate is also lower for the Virgo sample, followed by the group and isolated galaxies. Finally, the molecular gas depletion time is longer for the Virgo galaxies compared to the group and isolated galaxies, which suggests the possible effects of environment on the galaxy's star formation properties.

  14. Far-UV Emission Properties of FR1 Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Danforth, Charles W.; Stocke, John T.; France, Kevin; Begelman, Mitchell C.; Perlman, Eric

    2016-11-01

    The power mechanism and accretion geometry for low-power FR 1 radio galaxies are poorly understood in comparison to those for Seyfert galaxies and QSOs. In this paper, we use the diagnostic power of the Lyα recombination line observed using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope (HST) to investigate the accretion flows in three well-known, nearby FR 1s: M87, NGC 4696, and Hydra A. The Lyα emission line’s luminosity, velocity structure, and the limited knowledge of its spatial extent provided by COS are used to assess conditions within a few parsecs of the supermassive black hole in these radio-mode active galactic nuclei. We observe strong Lyα emission in all three objects with total luminosity similar to that seen in BL Lacertae objects. M87 shows a complicated emission-line profile in Lyα, which varies spatially across the COS aperture and possibly temporally over several epochs of observation. In both NGC 4696 and M87, the Lyα luminosities ˜1040 erg s-1 are closely consistent with the observed strength of the ionizing continuum in Case B recombination theory and with the assumption of a near-unity covering factor. It is possible that the Lyα-emitting clouds are ionized largely by beamed radiation associated with the jets. Long-slit UV spectroscopy can be used to test this hypothesis. Hydra A and the several BL Lac objects studied in this and previous papers have Lyα luminosities larger than M87 but their extrapolated, nonthermal continua are so luminous that they overpredict the observed strength of Lyα, a clear indicator of relativistic beaming in our direction. Given their substantial space density (˜4 × 10-3 Mpc-3), the unbeamed Lyman continuum radiation of FR 1s may make a substantial minority contribution (˜10%) to the local UV background if all FR 1s are similar to M87 in ionizing flux level.

  15. Late Stages of Stellar Evolution and their Impact on Spectrophotometric Properties of Galaxies

    NASA Astrophysics Data System (ADS)

    Buzzoni, A.

    2007-12-01

    The connection between AGB evolution of stellar populations and infrared vs. ultraviolet properties of the parent galaxies is reviewed relying on the updated lookout provided by population-synthesis theory. In particular, planetary-nebula events and hot horizontal-branch evolution are assessed in a unitary view to outline a plain general picture of galaxy spectrophotometric evolution. This will include a brief discussion of relevant phenomena such as the ``UV upturn'' in ellipticals and the stellar mass loss properties along the galaxy morphological sequence.

  16. SDSS-IV MaNGA: properties of galaxies with kinematically decoupled stellar and gaseous components

    NASA Astrophysics Data System (ADS)

    Jin, Yifei; Chen, Yanmei; Shi, Yong; Tremonti, C. A.; Bershady, M. A.; Merrifield, M.; Emsellem, E.; Fu, Hai; Wake, D.; Bundy, K.; Lin, Lihwai; Argudo-Fernandez, M.; Huang, Song; Stark, D. V.; Storchi-Bergmann, T.; Bizyaev, D.; Brownstein, J.; Chisholm, J.; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Masters, K. L.; Malanushenko, E.; Pan, Kaike; Riffel, R. A.; Roman-Lopes, A.; Simmons, A.; Thomas, D.; Wang, Lan; Westfall, K.; Yan, Renbin

    2016-11-01

    We study the properties of 66 galaxies with kinematically misaligned gas and stars from MaNGA survey. The fraction of kinematically misaligned galaxies varies with galaxy physical parameters, i.e. M*, SFR and sSFR. According to their sSFR, we further classify these 66 galaxies into three categories, 10 star-forming, 26 `Green Valley' and 30 quiescent ones. The properties of different types of kinematically misaligned galaxies are different in that the star-forming ones have positive gradient in Dn4000 and higher gas-phase metallicity, while the green valley/quiescent ones have negative Dn4000 gradients and lower gas-phase metallicity on average. There is evidence that all types of the kinematically misaligned galaxies tend to live in more isolated environment. Based on all these observational results, we propose a scenario for the formation of star-forming galaxies with kinematically misaligned gas and stars - the progenitor accretes misaligned gas from a gas-rich dwarf or cosmic web, the cancellation of angular momentum from gas-gas collisions between the pre-existing gas and the accreted gas largely accelerates gas inflow, leading to fast centrally concentrated star formation. The higher metallicity is due to enrichment from this star formation. For the kinematically misaligned green valley and quiescent galaxies, they might be formed through gas-poor progenitors accreting kinematically misaligned gas from satellites which are smaller in mass.

  17. HST Emission Line Galaxies at z ~ 2: Comparing Physical Properties of Lyman Alpha and Optical Emission Line Selected Galaxies

    NASA Astrophysics Data System (ADS)

    Hagen, Alex; Zeimann, Gregory R.; Behrens, Christoph; Ciardullo, Robin; Grasshorn Gebhardt, Henry S.; Gronwall, Caryl; Bridge, Joanna S.; Fox, Derek B.; Schneider, Donald P.; Trump, Jonathan R.; Blanc, Guillermo A.; Chiang, Yi-Kuan; Chonis, Taylor S.; Finkelstein, Steven L.; Hill, Gary J.; Jogee, Shardha; Gawiser, Eric

    2016-01-01

    We compare the physical and morphological properties of z ˜ 2 Lyα emitting galaxies (LAEs) identified in the HETDEX Pilot Survey and narrow band studies with those of z ˜ 2 optical emission line selected galaxies (oELGs) identified via HST WFC3 infrared grism spectroscopy. Both sets of galaxies extend over the same range in stellar mass (7.5\\lt {log}M/{M}⊙ \\lt 10.5), size (0.5 < R < 3.0 kpc), and star formation rate (˜ 1\\lt {{SFR}}\\lt 100 {M}⊙ yr-1). Remarkably, a comparison of the most commonly used physical and morphological parameters—stellar mass, half-light radius, UV slope, SFR, ellipticity, nearest neighbor distance, star formation surface density, specific SFR, [O iii] luminosity, and [O iii] equivalent width—reveals no statistically significant differences between the populations. This suggests that the processes and conditions which regulate the escape of Lyα from a z ˜ 2 star-forming galaxy do not depend on these quantities. In particular, the lack of dependence on the UV slope suggests that Lyα emission is not being significantly modulated by diffuse dust in the interstellar medium. We develop a simple model of Lyα emission that connects LAEs to all high-redshift star-forming galaxies where the escape of Lyα depends on the sightline through the galaxy. Using this model, we find that mean solid angle for Lyα escape is {{{Ω }}}{{Ly}α }=2.4+/- 0.8 steradians; this value is consistent with those calculated from other studies.

  18. Constraining the Multi-Phase Gas Content of Galaxies in the Local Cosmic Web

    NASA Astrophysics Data System (ADS)

    Stark, David; Kannappan, S. J.; Wei, L. H.; Baker, A. J.; Haynes, M. P.; Giovanelli, R.; Heitsch, F.; RESOLVE Team; ALFALFA Team

    2010-01-01

    The RESOLVE (REsolved Spectroscopy Of a Local VolumE) Survey is a census of gas, stars, and dark matter in 1500 galaxies down to dwarf-scale baryonic masses of 109 Msun, occupying a range of cluster, group, and filament environments in the local cosmic web. We discuss strategies to estimate the gas mass in HI, H2, and warmer phases. RESOLVE falls largely within the footprint of the ongoing ALFALFA survey, allowing us to acquire accurate HI data for much of the sample. Any missing HI masses will be estimated from color and environment data, based on trends calibrated using the ALFALFA data set. Initially, our constraints on the molecular gas component will be largely indirect, based on either AKARI FIR data or a new technique presented here that links CO-derived H2/HI ratios to stellar-mass normalized color gradients. We discuss additional strategies under development to better measure molecular gas and constrain the mass in warmer phases. In particular, we describe observational constraints on the nature of additional gas that is detected dynamically in a sample of very blue, gas-dominated galaxies, possibly representing a warm-hot phase or a low-metallicity molecular component. Obtaining a full gas census for the RESOLVE survey will allow us to model gas phase transitions and star formation, specifically examining how baryonic mass component ratios and conversion timescales depend on galaxy mass and environment.

  19. Mapping the Similarities of Spectra: Global and Locally-biased Approaches to SDSS Galaxies

    NASA Astrophysics Data System (ADS)

    Lawlor, David; Budavári, Tamás; Mahoney, Michael W.

    2016-12-01

    We present a novel approach to studying the diversity of galaxies. It is based on a novel spectral graph technique, that of locally-biased semi-supervised eigenvectors. Our method introduces new coordinates that summarize an entire spectrum, similar to but going well beyond the widely used Principal Component Analysis (PCA). Unlike PCA, however, this technique does not assume that the Euclidean distance between galaxy spectra is a good global measure of similarity. Instead, we relax that condition to only the most similar spectra, and we show that doing so yields more reliable results for many astronomical questions of interest. The global variant of our approach can identify very finely numerous astronomical phenomena of interest. The locally-biased variants of our basic approach enable us to explore subtle trends around a set of chosen objects. The power of the method is demonstrated in the Sloan Digital Sky Survey Main Galaxy Sample, by illustrating that the derived spectral coordinates carry an unprecedented amount of information.

  20. Polarization properties of localized structures in VCSELs

    NASA Astrophysics Data System (ADS)

    Averlant, Etienne; Tlidi, Mustapha; Ackemann, Thorsten; Thienpont, Hugo; Panajotov, Krassimir

    2016-04-01

    Broad area Vertical-Cavity Surface-Emitting Lasers (VCSELs) have peculiar polarization properties which are a field of study by itself.1-3 These properties have already been used for localized structure generation, in a simple configuration, where only one polarization component was used.4 Here, we present new experimental and theoretical results on the complex polarization behavior of localized structures generated in an optically-injected broad area VCSEL. A linear stability analysis of the spin-flip VCSEL model is performed for the case of broad area devices, in a restrained and experimentally relevant parameter set. Numerical simulations are performed, in one and two dimensions. They reveal existence of vector localized structures. These structures have a complex polarization state, which is not simply a linear polarization following the one of the optical injection. Experimental results confirm theoretical predictions. Applications of this work can lead to the encoding of small color images in the polarization state of an ensemble of localized structures at the surface of a broad area VCSEL.

  1. Systematic properties of CO emission from galaxies. I - Luminosity function

    NASA Technical Reports Server (NTRS)

    Verter, Frances

    1987-01-01

    A sensitive survey of normal galaxies covering a wide range of luminosities and morphological types is combined with galaxy observations in the literature to provide a sample for statistical study. The global CO emission of these galaxies is extrapolated by modeling the galaxies with an exponential radial profile. The maximum-likelihood distribution functions of CO luminosity and CO/H I flux ratio are similar in behavior. Both have long tails of bright galaxies. However, the typical galaxy has a CO luminosity of about 10 to the 6th Jy km/s Mpc-squared or less and a CO/H I ratio of the order of 10 or less. Averages of the distributions of CO luminosity and CO/H I flux ratio are higher for galaxies of Hubble type Sb-Sbc than for groups of earlier or later types. Quantitative estimates of the possible error sources in the conversion of CO luminosity to molecular mass indicates that the peaking of CO emission at intermediate types is a fairly confident result.

  2. Gas and Dust Properties in Dwarf Irregular Galaxies

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  3. The effect of cosmic web filaments on the properties of groups and their central galaxies

    NASA Astrophysics Data System (ADS)

    Poudel, A.; Heinämäki, P.; Tempel, E.; Einasto, M.; Lietzen, H.; Nurmi, P.

    2017-01-01

    Context. The nature versus nurture scenario in galaxy and group evolution is a long-standing problem not yet fully understood on cosmological scales. Aims: We study the properties of groups and their central galaxies in different large-scale environments defined by the luminosity density field and the cosmic web filaments. Methods: We use the luminosity density field constructed using 8 h-1 Mpc smoothing to characterize the large-scale environments. We use the Bisous model to extract the filamentary structures in different large-scale environments. We study the properties of galaxy groups as a function of their dynamical mass in different large-scale environments. Results: We find differences in the properties of central galaxies and their groups in and outside of filaments at fixed halo and large-scale environments. In high-density environments, the group mass function has higher number densities in filaments compared to that outside of filaments towards the massive end. The relation is the opposite in low-density environments. At fixed group mass and large-scale luminosity density, mass-to-light ratios show that groups in filaments are slightly more luminous than those outside of filaments. At fixed group mass and large-scale luminosity density, central galaxies in filaments have redder colors, higher stellar masses, and lower specific star formation rates than those outside of filaments. However, the differences in central galaxy and group properties in and outside of filaments are not clear in some group mass bins. We show that the differences in central galaxy properties are due to the higher abundances of elliptical galaxies in filaments. Conclusions: Filamentary structures in the cosmic web are not simply visual associations of galaxies, but rather play an important role in shaping the properties of groups and their central galaxies. The differences in central galaxy and group properties in and outside of cosmic web filaments are not simple effects related

  4. VizieR Online Data Catalog: JKs photometry of local universe galaxies (Grauer+, 2003)

    NASA Astrophysics Data System (ADS)

    Grauer, A. D.; Rieke, M. J.; Quillen, A. C.

    2003-11-01

    This paper presents empirical results from a deep imaging survey of galaxies in the local universe at the J and Ks wavelengths. Three hundred ninety-one images have been obtained and calibrated using the same camera and filter set with the Steward Observatory 1.6m Kuiper Telescope on Mount Bigelow and the 2.3m Bok Telescope on Kitt Peak. The limiting magnitude is typically 22mag/arcsec at J and 21mag/arcsec at Ks. The central surface brightness, apparent magnitudes, sizes, scale lengths, and inclinations are tabulated from measurements made using these data. The purpose of this paper is to provide basic near-infrared data on a variety of galaxy types. (2 data files).

  5. UV Properties and Evolution of High-redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.

  6. Accounting for the dispersion in the x ray properties of early-type galaxies

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III; Sarazin, Craig L.

    1990-01-01

    The x ray luminosities of early-type galaxies are correlated with their optical (e.g., blue) luminosities (L sub X approx. L sub B exp 1.6), but the x ray luminosities exhibit considerable scatter for a given optical luminosity L sub B. This dispersion in x ray luminosity is much greater than the dispersion of other properties of early-type galaxies (for a given L sub B), such as luminosity scale-length, velocity dispersion, color, and metallicity. Here, researchers consider several possible sources for the dispersion in x ray luminosity. Some of the scatter in x ray luminosity may result from stellar population variations between galaxies with similar L sub B. Since the x ray emitting gas is from accumulated stellar mass loss, the L sub X dispersion may be due to variations in integrated stellar mass loss rates. Another possible cause of the L sub X dispersion may be variations in the amount of cool material in the galaxies; cool gas may act as an energy sink for the hot gas. Infrared emission may be used to trace such cool material, so researchers look for a correlation between the infrared emission and the x ray emission of early-type galaxies at fixed L sub B. Velocity dispersion variations between galaxies of similar L sub B may also contribute to the L sub X dispersion. The most likely a priori source of the dispersion in L sub X is probably the varying amount of ram-pressure stripping in a range of galaxy environments. The hot gaseous halos of early-type galaxies can be stripped in encounters with other galaxies or with ambient cluster gas if the intracluster gas is sufficiently dense. Researchers find that the most likely cause of dispersion in the x ray properties of early type galaxies is probably the ram-pressure stripping of gaseous halos from galaxies. For a sample of 81 early-type galaxies with x ray luminosities or upper limits derived from Einstein Observatory observations (CFT) researchers calculated the cumulative distribution of angular distances

  7. Intracluster medium cooling, AGN feedback, and brightest cluster galaxy properties of galaxy groups. Five properties where groups differ from clusters

    NASA Astrophysics Data System (ADS)

    Bharadwaj, V.; Reiprich, T. H.; Schellenberger, G.; Eckmiller, H. J.; Mittal, R.; Israel, H.

    2014-12-01

    Aims: We aim to investigate cool-core and non-cool-core properties of galaxy groups through X-ray data and compare them to the AGN radio output to understand the network of intracluster medium (ICM) cooling and feedback by supermassive black holes. We also aim to investigate the brightest cluster galaxies (BCGs) to see how they are affected by cooling and heating processes, and compare the properties of groups to those of clusters. Methods: Using Chandra data for a sample of 26 galaxy groups, we constrained the central cooling times (CCTs) of the ICM and classified the groups as strong cool-core (SCC), weak cool-core (WCC), and non-cool-core (NCC) based on their CCTs. The total radio luminosity of the BCG was obtained using radio catalogue data and/or literature, which in turn was compared to the cooling time of the ICM to understand the link between gas cooling and radio output. We determined K-band luminosities of the BCG with 2MASS data, and used a scaling relation to constrain the masses of the supermassive black holes, which were then compared to the radio output. We also tested for correlations between the BCG luminosity and the overall X-ray luminosity and mass of the group. The results obtained for the group sample were also compared to previous results for clusters. Results: The observed cool-core/non-cool-core fractions for groups are comparable to those of clusters. However, notable differences are seen: 1) for clusters, all SCCs have a central temperature drop, but for groups this is not the case as some have centrally rising temperature profiles despite very short cooling times; 2) while for the cluster sample, all SCC clusters have a central radio source as opposed to only 45% of the NCCs, for the group sample, all NCC groups have a central radio source as opposed to 77% of the SCC groups; 3) for clusters, there are indications of an anticorrelation trend between radio luminosity and CCT. However, for groups this trend is absent; 4) the indication of

  8. Herschel-ATLAS: the surprising diversity of dust-selected galaxies in the local submillimetre Universe

    NASA Astrophysics Data System (ADS)

    Clark, C. J. R.; Dunne, L.; Gomez, H. L.; Maddox, S.; De Vis, P.; Smith, M. W. L.; Eales, S. A.; Baes, M.; Bendo, G. J.; Bourne, N.; Driver, S. P.; Dye, S.; Furlanetto, C.; Grootes, M. W.; Ivison, R. J.; Schofield, S. P.; Robotham, A. S. G.; Rowlands, K.; Valiante, E.; Vlahakis, C.; van der Werf, P.; Wright, A. H.; de Zotti, G.

    2015-09-01

    We present the properties of the first 250 μm blind sample of nearby galaxies (15 < D < 46 Mpc) containing 42 objects from the Herschel Astrophysical Terahertz Large Area Survey. Herschel's sensitivity probes the faint end of the dust luminosity function for the first time, spanning a range of stellar mass (7.4 < M⋆ < 11.3 log10 M⊙), star formation activity (-11.8 < SSFR < -8.9 log10 yr-1), gas fraction (3-96 per cent), and colour (0.6 < FUV-KS < 7.0 mag). The median cold dust temperature is 14.6 K, colder than in the Herschel Reference Survey (18.5 K) and Planck Early Release Compact Source Catalogue (17.7 K). The mean dust-to-stellar mass ratio in our sample is higher than these surveys by factors of 3.7 and 1.8, with a dust mass volume density of (3.7 ± 0.7) × 105 M⊙ Mpc-3. Counter-intuitively, we find that the more dust rich a galaxy, the lower its UV attenuation. Over half of our dust-selected sample are very blue in FUV-KS colour, with irregular and/or highly flocculent morphology; these galaxies account for only 6 per cent of the sample's stellar mass but contain over 35 per cent of the dust mass. They are the most actively star-forming galaxies in the sample, with the highest gas fractions and lowest UV attenuation. They also appear to be in an early stage of converting their gas into stars, providing valuable insights into the chemical evolution of young galaxies.

  9. The nuclear properties and extended morphologies of powerful radio galaxies: the roles of host galaxy and environment

    NASA Astrophysics Data System (ADS)

    Miraghaei, H.; Best, P. N.

    2017-01-01

    Powerful radio galaxies exist as either compact or extended sources, with the extended sources traditionally classified by their radio morphologies as Fanaroff-Riley (FR) type I and II sources. FRI/II and compact radio galaxies have also been classified by their optical spectra into two different types: high excitation (HERG; quasar-mode) and low excitation (LERG; jet-mode). We present a catalogue of visual morphologies for a complete sample of >1000 1.4-GHz-selected extended radio sources from the Sloan Digital Sky Survey. We study the environment and host galaxy properties of FRI/II and compact sources, classified into HERG/LERG types, in order to separate and distinguish the factors that drive the radio morphological variations from those responsible for the spectral properties. Comparing FRI LERGs with FRII LERGs at fixed stellar mass and radio luminosity, we show that FRIs typically reside in richer environments and are hosted by smaller galaxies with higher mass surface density; this is consistent with extrinsic effects of jet disruption driving the FR dichotomy. Using matched samples of HERGs and LERGs, we show that HERG host galaxies are more frequently star-forming, with more evidence for disk-like structure than LERGs, in accordance with currently-favoured models of fundamentally different fuelling mechanisms. Comparing FRI/II LERGs with compact LERGs, we find the primary difference is that compact objects typically harbour less massive black holes. This suggests that lower-mass black holes may be less efficient at launching stable radio jets, or do so for shorter times. Finally, we investigate rarer sub-classes: wide-angle tail, head-tail, FR-hybrid and double-double sources.

  10. Structural Properties and Visual Morphologies of 2 Galaxies in the CANDELS Fields and Hydrodynamical Simulations

    NASA Astrophysics Data System (ADS)

    Mozena, Mark; Faber, S. M.; Koo, D. C.; Primack, J. R.; Dekel, A.; Moody, C. E.; Ceverino, D.; CANDELS

    2013-01-01

    The 2 universe is an active epoch of increased star formation and AGN activity. Through major mergers, minor mergers, and cold flow gas accretion, galaxies are quickly increasing their masses and changing their global structural properties and morphologies. Using the deepest optical (ACS) and near infra-red (WFC3) observations from the HST Multi-Cycle Treasury CANDELS (Cosmic Assembly Near Infra-Red Deep Extragalactic Legacy Survey), we compare the structural properties of 2 galaxies in the rest-frame near-UV and optical to those predicted by the latest cosmologically motivated hydrodynamical simulations (Hydro-ART by Ceverino, Dekel and Primack and ERIS by Guedes and Madau). We render these simulated galaxy images to mimic the observed ACS and WFC3 images in CANDELS, and include the effects of dust obscuration. We explore how the sizes, masses, and morphologies of 2 galaxies observed in the hydrodynamical models compare with the global properties of galaxies observed in the CANDELS fields. Comparing the observations of 2 CANDELS galaxies with those from the latest hydrodynamical models provides new and important insights into the nature of galaxy formation and assembly in the exciting 2 universe.

  11. Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

    NASA Technical Reports Server (NTRS)

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-01-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  12. A comparative study of local galaxy clusters - I. Derived X-ray observables

    NASA Astrophysics Data System (ADS)

    Rozo, E.; Rykoff, E. S.; Bartlett, J. G.; Evrard, A.

    2014-02-01

    We examine systematic differences in the derived X-ray properties of galaxy clusters as reported by three different groups: Vikhlinin et al., Mantz et al. and Plank Collaboration. The sample overlap between any two pairs of works ranges between 16 to 28 galaxy clusters. We find systematic differences in most reported X-ray properties, including the total cluster mass, M500. The most extreme case is an average 45 ± 5 per cent difference in cluster mass between the Plank Collaboration and Mantz et al., for clusters at z > 0.13 (averaged over 16 clusters). These differences also induce differences in cluster observables defined within an R500 aperture. After accounting for aperture differences, we find very good agreement in gas mass estimates between the different groups. However, the soft-band X-ray luminosity, LX, core-excised spectroscopic temperature, TX, and gas thermal energy, YX = MgasTX display mean differences at the 5-15 per cent level. We also find that the low (z ≤ 0.13) and high (z ≥ 0.13) redshift galaxy cluster samples in Plank Collaboration appear to be systematically different: the YSZ/YX ratio for each of these two sub-samples is ln (YSZ/YX) = -0.06 ± 0.04 and ln (YSZ/YX) = 0.08 ± 0.04, respectively.

  13. Alignments of the galaxies in and around the Virgo cluster with the local velocity shear

    SciTech Connect

    Lee, Jounghun; Rey, Soo Chang; Kim, Suk

    2014-08-10

    Observational evidence is presented for the alignment between the cosmic sheet and the principal axis of the velocity shear field at the position of the Virgo cluster. The galaxies in and around the Virgo cluster from the Extended Virgo Cluster Catalog that was recently constructed by Kim et al. are used to determine the direction of the local sheet. The peculiar velocity field reconstructed from the Sloan Digital Sky Survey Data Release 7 is analyzed to estimate the local velocity shear tensor at the Virgo center. Showing first that the minor principal axis of the local velocity shear tensor is almost parallel to the direction of the line of sight, we detect a clear signal of alignment between the positions of the Virgo satellites and the intermediate principal axis of the local velocity shear projected onto the plane of the sky. Furthermore, the dwarf satellites are found to appear more strongly aligned than their normal counterparts, which is interpreted as an indication of the following. (1) The normal satellites and the dwarf satellites fall in the Virgo cluster preferentially along the local filament and the local sheet, respectively. (2) The local filament is aligned with the minor principal axis of the local velocity shear while the local sheet is parallel to the plane spanned by the minor and intermediate principal axes. Our result is consistent with the recent numerical claim that the velocity shear is a good tracer of the cosmic web.

  14. Properties of galaxies reproduced by a hydrodynamic simulation.

    PubMed

    Vogelsberger, M; Genel, S; Springel, V; Torrey, P; Sijacki, D; Xu, D; Snyder, G; Bird, S; Nelson, D; Hernquist, L

    2014-05-08

    Previous simulations of the growth of cosmic structures have broadly reproduced the 'cosmic web' of galaxies that we see in the Universe, but failed to create a mixed population of elliptical and spiral galaxies, because of numerical inaccuracies and incomplete physical models. Moreover, they were unable to track the small-scale evolution of gas and stars to the present epoch within a representative portion of the Universe. Here we report a simulation that starts 12 million years after the Big Bang, and traces 13 billion years of cosmic evolution with 12 billion resolution elements in a cube of 106.5 megaparsecs a side. It yields a reasonable population of ellipticals and spirals, reproduces the observed distribution of galaxies in clusters and characteristics of hydrogen on large scales, and at the same time matches the 'metal' and hydrogen content of galaxies on small scales.

  15. High-resolution UV studies of SAURON galaxies with WFC3: constraining recent star formation and its drivers in local early-type galaxies

    NASA Astrophysics Data System (ADS)

    Kaviraj, Sugata

    2011-10-01

    A significant recent discovery, using survey data in the rest-frame ultraviolet {UV}, is the unambiguous detection of widespread, low-level recent star formation {RSF} in nearby early-type galaxies {ETGs}. Its extreme sensitivity to young stars makes the UV the ideal tool to accurately quantify the weak star formation in ETGs, which were traditionally thought to be evolving largely passively. We aim to combine the UV capabilities of WFC3 with the powerful SAURON survey - which offers optical integral-field spectroscopy of local ETGs - to study RSF in ETGs in unprecedented detail. Our targets are a subset of SAURON with fully mapped molecular CO and signatures of star formation. For each target we aim to {1} use a pixel-by-pixel analysis to spatially map the properties of the young stars {ages/mass fractions/metallicities} {2} calculate ages/metallicities of individual globular clusters to probe the galaxyâ??s mass assembly over time {3} combine UV-derived RSF estimates with CO gas maps to study the star formation law on unprecedentedly small scales {4} compare the age-dated substructure to numerical simulations of minor mergers to constrain characteristics of the last merger event {e.g. mass ratios, satellite gas fractions} in ETGs that are likely to be merger remnants. The research leverages our past work with UV data {e.g. GALEX} and a published WFC3 study of NGC 4150, which we use to explicitly demonstrate the scope and quality of the science results. The unique WFC3 combination of high UV sensitivity and spatial resolution are critical and we demonstrate why this proposal cannot be fulfilled using any other facility. The proposal targets 10 ETGs with 15 orbits.

  16. Ultraviolet Properties of Primeval Galaxies: Theoretical Models from Stellar Population Synthesis

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto

    2002-03-01

    The ultraviolet luminosity evolution of star-forming galaxies is explored from the theoretical point of view, especially focusing on the theory of UV energetics in simple and composite stellar populations and its relationship to the star formation rate and other main evolutionary parameters. Galaxy emission below λ<3000 Å directly correlates with actual star formation, not depending on the total mass of the system. A straightforward calibration is obtained, in this sense, from the theoretical models at 1600, 2000, and 2800 Å, and a full comparison is carried out with IUE data and other balloon-borne observations for local galaxies. The claimed role of late-type systems as prevailing contributors to the cosmic UV background is reinforced by our results; at 2000 Å, Im irregulars are found in fact nearly 4 orders of magnitude brighter than ellipticals, per unit luminous mass. The role of dust absorption in the observation of high-redshift galaxies is assessed, comparing the model output and observed spectral energy distribution of local galaxy samples. Similar to what we observe in our own galaxy, a quick evolution in the dust environment might be envisaged in primeval galaxies, with an increasing fraction of luminous matter that would escape the regions of harder and ``clumpy'' dust absorption on a timescale of some 107 yr, comparable to the lifetime of stars of 5-10 Msolar.

  17. Dwarf galaxies in the Local Group: cornerstones for stellar astrophysics and cosmology

    NASA Astrophysics Data System (ADS)

    Bono, G.; Stetson, P. B.; Monelli, M.; Fabrizio, M.; Sanna, N.; Nonino, M.; Walker, A. R.; Bresolin, F.; Buonanno, R.; Caputo, F.; Castellani, M.; Corsi, C. E.; Dall'Ora, M.; Ferraro, I.; François, P.; Iannicola, G.; Matsunaga, M.; Pulone, L.; Romaniello, M.; Storm, J.; Thévenin, F.

    2010-12-01

    Dwarf galaxies have been the crossroad of significant theoretical and observational efforts, but we still lack firm constraints concerning their formation and evolution. They are also fundamental laboratories to investigate the impact of the environment on star formation and on chemical evolution in stellar systems that are order of magnitudes smaller than giant galaxies. We present some recent results concerning the dwarf spheroidal Carina and the dwarf irregular IC10. In particular, we focus our attention on the evolutionary properties of their stellar populations using accurate and deep color-magnitude diagrams. We also briefly discuss the impact that the transition from old, low-mass (horizontal branch) to intermediate-age (red clump) helium burning stars has in constraining the star formation history of complex stellar systems.

  18. CENTRAL STELLAR MASS DEFICITS IN THE BULGES OF LOCAL LENTICULAR GALAXIES, AND THE CONNECTION WITH COMPACT z {approx} 1.5 GALAXIES

    SciTech Connect

    Dullo, Bililign T.; Graham, Alister W.

    2013-05-01

    We have used the full radial extent of images from the Hubble Space Telescope's Advanced Camera for Surveys and Wide Field Planetary Camera 2 to extract surface brightness profiles from a sample of six, local lenticular galaxy candidates. We have modeled these profiles using a core-Sersic bulge plus an exponential disk model. Our fast rotating lenticular disk galaxies with bulge magnitudes M{sub V} {approx}< -21.30 mag have central stellar deficits, suggesting that these bulges may have formed from ''dry'' merger events involving supermassive black holes (BHs) while their surrounding disk was subsequently built up, perhaps via cold gas accretion scenarios. The central stellar mass deficits M{sub def} are roughly 0.5-2 M{sub BH} (BH mass), rather than {approx}10-20 M{sub BH} as claimed from some past studies, which is in accord with core-Sersic model mass deficit measurements in elliptical galaxies. Furthermore, these bulges have Sersic indices n {approx}3, half-light radii R{sub e} < 2 kpc and masses >10{sup 11} M{sub Sun }, and therefore appear to be descendants of the compact galaxies reported at z {approx} 1.5-2. Past studies which have searched for these local counterparts by using single-component galaxy models to provide the z {approx} 0 size comparisons have overlooked these dense, compact, and massive bulges in today's early-type disk galaxies. This evolutionary scenario not only accounts for what are today generally old bulges-which must be present in z {approx} 1.5 images-residing in what are generally young disks, but it eliminates the uncomfortable suggestion of a factor of three to five growth in size for the compact, z {approx} 1.5 galaxies that are known to possess infant disks.

  19. Mid-IR emission of galaxies in the Virgo cluster. II. Integrated properties

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Lequeux, J.; Sauvage, M.; Boulade, O.; Boulanger, F.; Cesarsky, D.; Dupraz, C.; Madden, S.; Viallefond, F.; Vigroux, L.

    1998-07-01

    We analyse the integrated properties of the Mid-IR emission of a complete, optically selected sample of galaxies in the Virgo cluster observed with the ISOCAM instrument on board the ISO satellite. The ISOCAM data allows us to construct the luminosity distribution at 6.75 and 15 mu m of galaxies for different morphological classes. These data are used to study the spectral energy distribution of galaxies of different type and luminosity in the wavelength range 2000 Angstroms - 100 mu m. The analysis shows that the Mid-IR emission up to 15 mu m of optically-selected, normal early-type galaxies (E, S0 and S0a) is dominated by the Rayleigh-Jeans tail of the cold stellar component. The Mid-IR emission of late-type galaxies is instead dominated by the thermal emission from dust. As in the Milky Way, the small dust grains emitting in the Mid-IR have an excess of emission if compared to big grains emitting in the Far-IR. While the Far-IR emission of galaxies increases with the intensity of the interstellar radiation field, their Mid-IR emission is non-linearly related to the UV radiation field. The spectral energy distributions of the target galaxies indicate that there is a linear relationship between the UV radiation field and the Mid-IR emission of galaxies for low or intermediate activities of star formation, while the emission from the hot dust seems to drop for strong UV fields. The Mid-IR colour of late-type galaxies is not related to their activity of star formation. The properties of the dust emission in the Mid-IR seem more related to the mass than to the morphological type of the target galaxy. Since the activity of star formation is anticorrelated to the mass of galaxies, this reflects a relationship between the emission of dust in the Mid-IR and the UV radiation field: galaxies with the lowest Mid-IR emission for a given UV field are low mass, dwarf galaxies. These observational evidences are easily explained if the carriers of the Unidentified Infrared Bands

  20. The CALIFA survey across the Hubble sequence. Spatially resolved stellar population properties in galaxies

    NASA Astrophysics Data System (ADS)

    González Delgado, R. M.; García-Benito, R.; Pérez, E.; Cid Fernandes, R.; de Amorim, A. L.; Cortijo-Ferrero, C.; Lacerda, E. A. D.; López Fernández, R.; Vale-Asari, N.; Sánchez, S. F.; Mollá, M.; Ruiz-Lara, T.; Sánchez-Blázquez, P.; Walcher, C. J.; Alves, J.; Aguerri, J. A. L.; Bekeraité, S.; Bland-Hawthorn, J.; Galbany, L.; Gallazzi, A.; Husemann, B.; Iglesias-Páramo, J.; Kalinova, V.; López-Sánchez, A. R.; Marino, R. A.; Márquez, I.; Masegosa, J.; Mast, D.; Méndez-Abreu, J.; Mendoza, A.; del Olmo, A.; Pérez, I.; Quirrenbach, A.; Zibetti, S.

    2015-09-01

    Various different physical processes contribute to the star formation and stellar mass assembly histories of galaxies. One important approach to understanding the significance of these different processes on galaxy evolution is the study of the stellar population content of today's galaxies in a spatially resolved manner. The aim of this paper is to characterize in detail the radial structure of stellar population properties of galaxies in the nearby universe, based on a uniquely large galaxy sample, considering the quality and coverage of the data. The sample under study was drawn from the CALIFA survey and contains 300 galaxies observed with integral field spectroscopy. These cover a wide range of Hubble types, from spheroids to spiral galaxies, while stellar masses range from M⋆ ~ 109 to 7 × 1011 M⊙. We apply the fossil record method based on spectral synthesis techniques to recover the following physical properties for each spatial resolution element in our target galaxies: the stellar mass surface density (μ⋆), stellar extinction (AV), light-weighted and mass-weighted ages (⟨log age⟩L, ⟨log age⟩M), and mass-weighted metallicity (⟨log Z⋆⟩M). To study mean trends with overall galaxy properties, the individual radial profiles are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd). We confirm that more massive galaxies are more compact, older, moremetal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M⋆, which is evidence that quenching is related to morphology, but not driven by mass. Negative gradients of ⟨log age⟩L are consistent with an inside-out growth of galaxies, with the largest ⟨log age⟩L gradients in Sb-Sbc galaxies. Further, the mean stellar ages of disks and bulges are

  1. The Magellanic Analog Dwarf Companions and Stellar Halos (MADCASH) Survey: Near-Field Cosmology with Resolved Stellar Populations Around Local Volume LMC Stellar-Mass Galaxies

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Sand, David J.; Willman, Beth; Brodie, Jean P.; Crnojevic, Denija; Peter, Annika; Price, Paul A.; Romanowsky, Aaron J.; Spekkens, Kristine; Strader, Jay

    2017-01-01

    We discuss the first results of our observational program to comprehensively map nearly the entire virial volumes of roughly LMC stellar mass galaxies at distances of ~2-4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. These will inform our understanding of the recent DES discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. We will detail our discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru+HyperSuprimeCam imaging reaching ~2 magnitudes below its TRGB. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to assess the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles. We outline the constraints on galaxy formation models that will be provided by our observations of low-mass galaxy halos and their satellites.

  2. Properties of the most metal-poor gas-rich LSB dwarf galaxies SDSS J0015+0104 and J2354-0005 residing in the Eridanus void

    NASA Astrophysics Data System (ADS)

    Pustilnik, S. A.; Martin, J.-M.; Lyamina, Y. A.; Kniazev, A. Y.

    2013-07-01

    SDSS J0015+0104 is the lowest metallicity low surface brightness dwarf (LSBD) galaxy known. The oxygen abundance in its H II region SDSS J001520.70+010436.9 (at ˜1.5 kpc from the galaxy centre) is 12+log (O/H) = 7.07 (Guseva et al.). This galaxy, at the distance of 28.4 Mpc, appears to reside deeply in the volume devoid of luminous massive galaxies, known as the Eridanus void. SDSS J235437.29-000501.6 is another Eridanus void LSBD galaxy, with parameter 12+log (O/H) = 7.36 (also Guseva et al.). We present the results of their H I observations with the Nançay Radio Telescope revealing their high ratios of M(H I)/LB ˜ 2.3. Based on the Sloan Digital Sky Survey images, we derived for both galaxies their radial surface brightness profiles and the main photometric parameters. Their colours and total magnitudes are used to estimate the galaxy stellar mass and ages. The related gas mass fractions, fg ˜ 0.98 and ˜0.97, and the extremely low metallicities (much lower than for their more typical counterparts with the same luminosity) indicate their unevolved status. We compare these Eridanus void LSBDs with several extreme LSBD galaxies residing in the nearby Lynx-Cancer void. Based on the combination of all their unusual properties, the two discussed LSBD galaxies are similar to the unusual LSBDs residing in the closer void. This finding presents additional evidence for the existence in voids of a sizeable fraction of low-mass unevolved galaxies. Their dedicated search might result in the substantial increase of the number of such objects in the local Universe and in the advancement of understanding their nature.

  3. Type Ia Supernova Hubble Residuals and Host-Galaxy Properties

    SciTech Connect

    Nearby Supernova Factory; Kim, A. G.; Aldering, G.; Antilogus, P.; Aragon, C.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Cellier-Holzem, F.; Childress, M.; Chotard, N.; Copin, Y.; Fakhouri, H. K.; Feindt, U.; Fleury, M.; Gangler, E.; Greskovic, P.; Guy, J.; Kowalski, M.; Lombardo, S.; Nordin, J.; Nugent, P.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Rigault, M.; Runge, K.; Saunders, C.; Scalzo, R.; Smadja, G.; Tao, C.; Thomas, R. C.; Weaver, B. A.

    2014-01-17

    Kim et al. (2013) [K13] introduced a new methodology for determining peak- brightness absolute magnitudes of type Ia supernovae from multi-band light curves. We examine the relation between their parameterization of light curves and Hubble residuals, based on photometry synthesized from the Nearby Supernova Factory spec- trophotometric time series, with global host-galaxy properties. The K13 Hubble residual step with host mass is 0.013 ? 0.031 mag for a supernova subsample with data coverage corresponding to the K13 training; at ? 1?, the step is not significant and lower than previous measurements. Relaxing the data coverage requirement the Hubble residual step with host mass is 0.045 ? 0.026 mag for the larger sample; a calculation using the modes of the distributions, less sensitive to outliers, yields a step of 0.019 mag. The analysis of this article uses K13 inferred luminosities, as distinguished from previous works that use magnitude corrections as a function of SALT2 color and stretch param- eters: Steps at> 2? significance are found in SALT2 Hubble residuals in samples split by the values of their K13 x(1) and x(2) light-curve parameters. x(1) affects the light- curve width and color around peak (similar to the∆m15 and stretch parameters), and x(2) affects colors, the near-UV light-curve width, and the light-curve decline 20 to 30 days after peak brightness. The novel light-curve analysis, increased parameter set, and magnitude corrections of K13 may be capturing features of SN Ia diversity arising from progenitor stellar evolution.

  4. Type Ia supernova Hubble residuals and host-galaxy properties

    SciTech Connect

    Kim, A. G.; Aldering, G.; Aragon, C.; Bailey, S.; Fakhouri, H. K.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Fleury, M.; Guy, J.; Baltay, C.; Buton, C.; Feindt, U.; Greskovic, P.; Kowalski, M.; Childress, M.; Chotard, N.; Copin, Y.; Gangler, E. [Université de Lyon, F-69622 Lyon; Université de Lyon 1, Villeurbanne; CNRS and others

    2014-03-20

    Kim et al. introduced a new methodology for determining peak-brightness absolute magnitudes of type Ia supernovae from multi-band light curves. We examine the relation between their parameterization of light curves and Hubble residuals, based on photometry synthesized from the Nearby Supernova Factory spectrophotometric time series, with global host-galaxy properties. The K13 Hubble residual step with host mass is 0.013 ± 0.031 mag for a supernova subsample with data coverage corresponding to the K13 training; at <<1σ, the step is not significant and lower than previous measurements. Relaxing the data coverage requirement of the Hubble residual step with the host mass is 0.045 ± 0.026 mag for the larger sample; a calculation using the modes of the distributions, less sensitive to outliers, yields a step of 0.019 mag. The analysis of this article uses K13 inferred luminosities, as distinguished from previous works that use magnitude corrections as a function of SALT2 color and stretch parameters: steps at >2σ significance are found in SALT2 Hubble residuals in samples split by the values of their K13 x(1) and x(2) light-curve parameters. x(1) affects the light-curve width and color around peak (similar to the Δm {sub 15} and stretch parameters), and x(2) affects colors, the near-UV light-curve width, and the light-curve decline 20-30 days after peak brightness. The novel light-curve analysis, increased parameter set, and magnitude corrections of K13 may be capturing features of SN Ia diversity arising from progenitor stellar evolution.

  5. Local Turbulent Disks: analogs of high-redshift vigorously star-forming disks and laboratories for galaxy assembly?

    NASA Astrophysics Data System (ADS)

    Damjanov, Ivana

    2012-10-01

    Kinematical investigations at redshifts 1galaxies exhibit very high internal velocity dispersions. Dynamical data collected with integral field spectrographs {IFS} suggest that the level of rotational support in these systems follows a trend in mass, with compact dispersion-dominated Lyman Break Galaxies at lower stelar masses and large dynamically unstable turbulent disks at stellar masses larger than 10^10 solar masses. The high velocity dispersion of these young disks results in a large characteristic scale for star-forming clusters thereby also explaining their 'clump cluster' morphology. Galaxies like these were thought to be absent from the local Universe. As part of a IFS campaign to observe the most H-alpha luminous galaxies in SDSS, we have discovered a sample of very rare objects seemingly identical to these high-z turbulent disks. In this proposal we seek imaging in H-alpha of thirteen local disk galaxies in our sample, using the ACS tunable-wavelength ramp filters. Our goal is to measure the size distribution of the star-forming complexes in these objects, with ten times the typical physical resolution of HST observations of high-z galaxies, in order to test the idea that they are indeed dynamically unstable turbulent disks caught in the process of formation. In synergy with existing high resolution HST imaging of the local analogs of low-mass dispersion-dominated galaxies at high redshift {Lyman Break Analogs}, our proposed observations of the local counterparts to large turbulent disks at high redshift will help to paint a complete picture of local analogs of high-z star-forming galaxies.

  6. EVIDENCE FOR A ∼300 MEGAPARSEC SCALE UNDER-DENSITY IN THE LOCAL GALAXY DISTRIBUTION

    SciTech Connect

    Keenan, R. C.; Barger, A. J.; Cowie, L. L.

    2013-09-20

    Galaxy counts and recent measurements of the luminosity density in the near-infrared have indicated the possibility that the local universe may be under-dense on scales of several hundred megaparsecs. The presence of a large-scale under-density in the local universe could introduce significant biases into the interpretation of cosmological observables, and, in particular, into the inferred effects of dark energy on the expansion rate. Here we measure the K-band luminosity density as a function of redshift to test for such a local under-density. For our primary sample in this study, we select galaxies from the UKIDSS Large Area Survey and use spectroscopy from the Sloan Digital Sky Survey (SDSS), the Two-degree Field Galaxy Redshift Survey, the Galaxy And Mass Assembly Survey (GAMA), and other redshift surveys to generate a K-selected catalog of ∼35, 000 galaxies that is ∼95% spectroscopically complete at K{sub AB} < 16.3 (K{sub AB} < 17 in the GAMA fields). To complement this sample at low redshifts, we also analyze a K-selected sample from the 2M++ catalog, which combines Two Micron All Sky Survey (2MASS) photometry with redshifts from the 2MASS redshift survey, the Six-degree Field Galaxy Redshift Survey, and the SDSS. The combination of these samples allows for a detailed measurement of the K-band luminosity density as a function of distance over the redshift range 0.01 < z < 0.2 (radial distances D ∼ 50-800 h{sub 70}{sup -1} Mpc). We find that the overall shape of the z = 0 rest-frame K-band luminosity function (M*-5log (h{sub 70}) = –22.15 ± 0.04 and α = –1.02 ± 0.03) appears to be relatively constant as a function of environment and distance from us. We find a local (z < 0.07, D < 300 h{sub 70}{sup -1} Mpc) luminosity density that is in good agreement with previous studies. Beyond z ∼ 0.07, we detect a rising luminosity density that reaches a value of roughly ∼1.5 times higher than that measured locally at z > 0.1. This suggests that the

  7. A search for CO in the Local Group dwarf irregular galaxy WLM

    NASA Astrophysics Data System (ADS)

    Taylor, C. L.; Klein, U.

    2001-02-01

    We present 12CO J = 1-> 0 and J = 2-> 1 observations of the low metallicity (12 + log(O/H) = 7.74) Local Group dwarf irregular galaxy WLM made with the 15 m SEST and 14 m FCRAO telescopes. Despite the presence a number of HII regions, we find no CO emission. We obtain low upper limits on the integrated intensity (I_CO<= 0.18 K km s-1 for CO (1->0)). The non-detection is consistent with the result of Taylor, Kobulnicky & Skillman (\\cite{TKS}), that dwarf galaxies below a metallicity of ~ 7.9 are not detected in CO emission. WLM shows that this trend continues for low metallicity galaxies even as their metallicities approach 7.9. These results are consistent with the models of the metal poor ISM by Norman & Spaans (\\cite{NS}). By comparing our CO data with observations of star formation in WLM, we find evidence for a high CO to H_2 conversion factor.

  8. The star formation histories of local group dwarf galaxies. II. Searching for signatures of reionization

    SciTech Connect

    Weisz, Daniel R.; Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon; Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2014-07-10

    We search for signatures of reionization in the star formation histories (SFHs) of 38 Local Group dwarf galaxies (10{sup 4} < M{sub *} < 10{sup 9} M{sub ☉}). The SFHs are derived from color-magnitude diagrams using archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. Only five quenched galaxies (And V, And VI, And XIII, Leo IV, and Hercules) are consistent with forming the bulk of their stars before reionization, when full uncertainties are considered. Observations of 13 of the predicted 'true fossils' identified by Bovill and Ricotti show that only two (Hercules and Leo IV) indicate star formation quenched by reionization. However, both are within the virial radius of the Milky Way and evidence of tidal disturbance complicates this interpretation. We argue that the late-time gas capture scenario posited by Ricotti for the low mass, gas-rich, and star-forming fossil candidate Leo T is observationally indistinguishable from simple gas retention. Given the ambiguity between environmental effects and reionization, the best reionization fossil candidates are quenched low mass field galaxies (e.g., KKR 25).

  9. Carbon star survey in the Local Group. VII. NGC 3109 a galaxy without a stellar halo

    NASA Astrophysics Data System (ADS)

    Demers, S.; Battinelli, P.; Letarte, B.

    2003-11-01

    We present a CFH12K wide field survey of the carbon star population in and around NGC 3109. Carbon stars, the brightest members of the intermediate-age population, were found nearly exclusively in and near the disk of NGC 3109, ruling out the existence of an extensive intermediate-age halo like the one found in NGC 6822. Over 400 carbon stars identified have = -4.71, confirming the nearly universality of mean magnitude of C star populations in Local Group galaxies. Star counts over the field reveal that NGC 3109 is a truncated disk shaped galaxy without an extensive stellar halo. The minor axis star counts reach the foreground density between 4' and 5', a distance that can be explained by an inclined disk rather than a spheroidal halo. We calculate a global C/M ratio of 1.75 +/- 0.20, a value expected for such a metal poor galaxy. The complete Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/795

  10. Physical properties of high-redshift WFC3 galaxies at z=7-10

    NASA Astrophysics Data System (ADS)

    Nagamine, Kentaro

    2010-09-01

    Over the past decade, large samples of Ly-break galaxies {LBGs} have been assembled at z=3-6. The observers are now pushing the forefront of galaxy formation study into the range of z=7-9 utilizing the new data from the WFC3 camera. However, due to the faintness of the sources at these redshifts, it is difficult to derive the physical parameters such as stellar mass and star formation histories of the candidate galaxies. Therefore, it would be helpful to obtain predictions on these quantities from theoretical models using self-consistent, cosmological hydrodynamic simulations of galaxy formation. In the proposed work, we will examine the physical properties of high-redshift star-forming galaxies at z=7-10 using cosmological hydrodynamic simulations. In the first step, we will develop a model for estimating the variable extinction values of individual galaxies based on their metal column densities. We will also examine the spectro-photometric properties, stellar masses, star formation histories, and spatial correlations, and provide feedback to the WFC3 observations. The second step of our project is to perform the radiative transfer calculations of stellar radiation from high-z galaxies using the Authentic Radiative Transfer {ART} code. This exact RT calculation will allow us to check the accuracy of our earlier results from part {1}, and to develop a better model of dust distribution in cosmological simulations.

  11. USING M DWARF SPECTRA TO MAP EXTINCTION IN THE LOCAL GALAXY

    SciTech Connect

    Jones, David O.; West, Andrew A.; Foster, Jonathan B.

    2011-08-15

    We use spectra of more than 56,000 M dwarfs from the Sloan Digital Sky Survey (SDSS) to create a high-latitude extinction map of the local Galaxy. Our technique compares spectra from the stars in the SDSS Data Release 7 M dwarf sample in low-extinction lines of sight, as determined by Schlegel et al., to other SDSS M dwarf spectra in order to derive improved distance estimates and accurate line-of-sight extinctions. Unlike most previous studies, which have used a two-color method to determine extinction, we fit extinction curves to fluxes across the spectral range from 5700 to 9200 A for every star in our sample. Our result is an A{sub V} map that extends from a few tens of pc to approximately 2 kpc away from the Sun. We also use a similar technique to create a map of R{sub V} values within approximately 1 kpc of the Sun and find that they are consistent with the widely accepted diffuse interstellar medium value of 3.1. Using our extinction data, we derive a dust scale height for the local Galaxy of 119 {+-} 15 pc and find evidence for a local dust cavity.

  12. The frequency and properties of young tidal dwarf galaxies in nearby groups

    NASA Astrophysics Data System (ADS)

    Lee-Waddell, K.; Spekkens, K.; Chandra, P.; Patra, N.; Cuillandre, J.-C.; Wang, J.; Haynes, M. P.; Cannon, J.; Stierwalt, S.; Sick, J.; Giovanelli, R.

    2017-03-01

    We present the results of a multi-wavelength investigation of the dwarf galaxy populations in three interacting galaxy groups: NGC 871/6/7, NGC 3166/9, NGC 4725/47. Using degree-scale Giant Metrewave Radio Telescope Hi mosaics and deep optical photometry from the Canada-France-Hawaii Telescope, we measured the Hi and stellar properties of the gas-rich low-mass group members to classify each one as a classical dwarf galaxy, a short-lived tidal knot or a tidal dwarf galaxy (TDG). Our observations detect several dwarf irregulars and various tidal knots. We identify four potentially long-lived tidal objects in the three groups, implying that TDGs are not readily produced. The tidal objects examined in this small survey also appear to have a wider variety of properties than TDGs formed in current simulations.

  13. PROPERTIES OF THE INTERSTELLAR MEDIUM IN STAR-FORMING GALAXIES AT z ∼ 1.4 REVEALED WITH ALMA

    SciTech Connect

    Seko, Akifumi; Ohta, Kouji; Iwamuro, Fumihide; and others

    2016-03-01

    We conducted observations of {sup 12}CO(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-H{sub 2} 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) × 10{sup 10} M{sub ⊙} 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) × 10{sup 7} M{sub ⊙}. 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) × 10{sup 8} yr while the results of the stacking analysis show ∼3 × 10{sup 8} 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.

  14. The Influence Of Environment On The Star Formation Properties Of Galaxies

    NASA Astrophysics Data System (ADS)

    Rodriguez Del Pino, Bruno

    2015-10-01

    This thesis explores the properties of galaxies that reside in regions of high density and the influence of the environment in their evolution. n particular, it aims to shed more light on the understanding of how galaxies stop forming stars, becoming passive objects, and the role played by environment in this process. The work presented here includes the study of the properties of galaxies in clusters at two different stages of their evolution: we first look at cluster galaxies that have recently stopped forming stars, and then we investigate the influence of environment on galaxies while they are still forming stars. The first study is based on Integral Field Spectroscopic (IFS) observations of a sample of disk `k+a' galaxies in a cluster at z 0.3. The `k+a' spectral feature imply a recent suppression of star formation in the galaxies, and therefore the study of their properties is crucial to understanding how the suppression happened. We study the kinematics and spatial distributions of the different stellar populations inhabiting these galaxies. We found that the last stars that were formed (i.e., younger stars) are rotationally-supported and behave similar to the older stars. Moreover, the spatial distribution of the young stars also resembles that of the older stellar populations, although the young stars tend to be more concentrated towards the central regions of the galaxies. These findings indicate that the process responsible for the suppression of the star formation in the cluster disk galaxies had to be gentle, withouth perturbing significantly the old stellar disks. However, a significant number of galaxies with centrally-concentrated young populations were found to have close companions, therefore implying that galaxy-galaxy interactions might also contribute to the cessation of the star formation. These results provide very valuable information on the putative transformation of star-forming galaxies into passive S0s. We then move to the study of the

  15. Constraining the Evolution of Galaxy Properties in Interacting Systems with UV-FIR Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Lanz, Lauranne; Zezas, A.; Brassington, N.; Smith, H. A.; Ashby, M. N.; da Cunha, E.; Hayward, C. C.; Jonsson, P.; Hernquist, L. E.; Fazio, G. G.

    2013-01-01

    The evolution of galaxies is greatly influenced by their interactions. As part of the Spitzer Interacting Galaxy Survey (SIGS), we imaged 48 nearby systems with Spitzer. We measured and modeled the spectral energy distributions (SEDs) at wavelengths from the ultraviolet (UV) to the far-infrared (FIR) of the set of these galaxies with publicly available Herschel SPIRE observations. We fit these SEDs with the Bayesian SED-fitting program MAGPHYS developed by da Cunha et al. (2008). In order to determine the reliability of the parameters extracted, we determined how well MAGPHYS recovers parameters of hydrodynamic simulations run with GADGET (Springel et al. 2005) and for which simulated photometry was calculated using the SUNRISE radiative transfer code (Jonsson et al. 2010). We present our conclusions on the variations with interaction stage of galaxy properties including: star formation histories; dust luminosities, temperatures, and masses; and stellar masses. We discuss how successfully MAGPHYS recovers galaxy properties and which instruments are most crucial for constraining masses, star formation histories, and dust properties. We compare the simulations directly to the observations, examining how unique a diagnostic an interacting galaxy SED can be. Finally, we compare and discuss how well the many simple star formation estimating relations (using 24 micron flux, for example) succeed and why.

  16. Spectral Investigation and Physical Properties of Markarian Galaxies from SDSS

    NASA Astrophysics Data System (ADS)

    Gyulzadyan, M. V.; Mickaelian, A. M.; Abrahamyan, H. V.; Paronyan, G. M.

    2016-06-01

    Beginning in the mid-1960s and continuing through 1978, the first large-area objective-prism survey for galaxies with blue and ultraviolet excess in their continuum radiation was conducted by Markarian, Lipovetskii and Stepanian (published in Lists I-XV). Observations were carried out using primarily a 1.5° objective prism with the 40″/52″ (1.0/1.3 m) Schmidt telescope at Byurakan Astrophysical Observatory. Their setup produced an inverse dispersion of 2500 Å/mm at Hβ (Markarian 1967). The publication of the List XV (Markarian et al. 1981) completed the Markarian Survey (also known as FBS, First Byurakan Survey). We present some average characteristics for 1493 Markarian galaxies derived from SDSS images and spectra and compare them to those of the two groups of the Second Byurakan Survey galaxies, defined using two indicators of activity as observed on objective-prism spectra: the presence of UV excess (860 UVX) in the continuum and the presence of emission lines (813 ELs). The parameters used for the comparison were morphology, redshift, apparent magnitude, absolute magnitude, the ratio of the small and the large semi-axes R (J), and close environment. For UVG the average apparent magnitude is 16.95m, for Mrk it is 15.2m, and for ELG it is 16.7m; the average absolute magnitude is 20.1m for Mrk, 20.73m for UVG, and 20.67m for ELG; the redshift is 0.024 for Mrk, 0.046 for UVG and 0.035 for ELG; the ratio of the small and the large semi-axes R (J) is 0.74 for Mrk and UVG, and 0.67 for ELG. On average, there are more spiral and compact galaxies among Mrk, UVG, and ELG objects. Some 31% of Mrk galaxies, 38% of UVG and 25% of ELG have neighboring galaxies in a circle with a radius of 50 kpc. In the course of the Markarian survey, more than 200 Seyfert galaxies, and hundreds of starburst, blue compact, and HII galaxies were discovered.

  17. Is Galaxy Dark Matter a Property of Spacetime?

    NASA Astrophysics Data System (ADS)

    Carmeli, M.

    We describe the motion of a particle in a central field in an expanding universe. Use is made of a double expansion in 1/c and 1/T, where c and T are the speed of light and the Hubble time. In the lowest approximation the fourth power of the rotational velocity is shown to be proportional to (2/3)GMcHo, where G is Newton's gravitational constant, M is the mass of the central body (galaxy) and Ho is the Hubble constant. This formula satisfies observations of stars moving in spiral and elliptical galaxies, and in accordance with the familiar Tully-Fisher law.

  18. Is galaxy dark matter a property of spacetime?

    NASA Astrophysics Data System (ADS)

    Carmeli, M.

    1998-10-01

    The author describes the motion of a particle in a central field in an expanding universe. Use is made of a double expansion in 1/c and 1/τ, where c and τ are the speed of light and the Hubble time. In the lowest approximation the rotational velocity is shown to satisfy ν4 = 2/3 GMcH0, where G is Newton's gravitational constant, M is the mass of the central body (galaxy), and H0 is the Hubble constant. This formula satisfies observations of stars moving in spiral and elliptical galaxies, and is in accordance with the familiar Tully-Fisher law.

  19. VizieR Online Data Catalog: Local SDSS galaxies in Herschel Stripe 82 (Rosario+, 2016)

    NASA Astrophysics Data System (ADS)

    Rosario, D. J.; Mendel, J. T.; Ellison, S. L.; Lutz, D.; Trump, J. R.

    2016-11-01

    We draw on the extensive set of measurements (redshifts, stellar masses, line fluxes, etc.) available from the SDSS/MPA-JHU data base to define and classify our sample of galaxies for study, and to understand their range of observed properties. Where possible, we employ Herschel and Wide-field Infrared Survey Explorer (WISE) photometry to constrain the TIR using spectral energy distribution (SED) fits, and GALEX FUV photometry to correct for stellar emission not absorbed by dust. These data are brought to bear on the cross-assessment of infrared (IR), UV and optical SFRs. (1 data file).

  20. LOCAL LUMINOUS INFRARED GALAXIES. I. SPATIALLY RESOLVED OBSERVATIONS WITH THE SPITZER INFRARED SPECTROGRAPH

    SciTech Connect

    Pereira-Santaella, Miguel; Alonso-Herrero, Almudena; Colina, Luis; Diaz-Santos, Tanio; Rieke, George H.; Engelbracht, Charles W.; Smith, J.-D. T.; Perez-Gonzalez, Pablo G.

    2010-06-15

    We present results from the Spitzer Infrared Spectrograph spectral mapping observations of 15 local luminous infrared galaxies (LIRGs). In this paper, we investigate the spatial variations of the mid-IR emission which includes fine structure lines, molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum emission, and the 9.7 {mu}m silicate feature. We also compare the nuclear and integrated spectra. We find that the star formation takes place in extended regions (several kpc) as probed by the PAH emission, as well as the [Ne II]12.81 {mu}m and [Ne III]15.56 {mu}m emissions. The behavior of the integrated PAH emission and 9.7 {mu}m silicate feature is similar to that of local starburst galaxies. We also find that the minima of the [Ne III]15.56 {mu}m/[Ne II]12.81 {mu}m ratio tends to be located at the nuclei and its value is lower than that of H II regions in our LIRGs and nearby galaxies. It is likely that increased densities in the nuclei of LIRGs are responsible for the smaller nuclear [Ne III]15.56 {mu}m/[Ne II]12.81 {mu}m ratios. This includes the possibility that some of the most massive stars in the nuclei are still embedded in ultracompact H II regions. In a large fraction of our sample, the 11.3 {mu}m PAH emission appears more extended than the dust 5.5 {mu}m continuum emission. We find a dependency of the 11.3 {mu}m PAH/7.7 {mu}m PAH and [Ne II]12.81 {mu}m/11.3 {mu}m PAH ratios with the age of the stellar populations. Smaller and larger ratios, respectively, indicate recent star formation. The estimated warm (300 K local starbursts, and Seyfert galaxies. Finally we find that the [Ne II]12.81 {mu}m velocity fields for most of the LIRGs in our sample are compatible with a rotating disk at {approx}kpc scales, and they are in a good agreement with H{alpha} velocity fields.

  1. STRUCTURE IN THE 3D GALAXY DISTRIBUTION. II. VOIDS AND WATERSHEDS OF LOCAL MAXIMA AND MINIMA

    SciTech Connect

    Way, M. J.; Gazis, P. R.; Scargle, Jeffrey D. E-mail: PGazis@sbcglobal.net

    2015-01-20

    The major uncertainties in studies of the multi-scale structure of the universe arise not from observational errors but from the variety of legitimate definitions and detection methods for individual structures. To facilitate the study of these methodological dependencies, we have carried out 12 different analyses defining structures in various ways. This has been done in a purely geometrical way by utilizing the HOP algorithm as a unique parameter-free method of assigning groups of galaxies to local density maxima or minima. From three density estimation techniques (smoothing kernels, Bayesian blocks, and self-organizing maps) applied to three data sets (the Sloan Digital Sky Survey Data Release 7, the Millennium simulation, and randomly distributed points) we tabulate information that can be used to construct catalogs of structures connected to local density maxima and minima. We also introduce a void finder that utilizes a method to assemble Delaunay tetrahedra into connected structures and characterizes regions empty of galaxies in the source catalog.

  2. A test of star formation laws in disk galaxies. II. Dependence on dynamical properties

    SciTech Connect

    Suwannajak, Chutipong; Tan, Jonathan C.; Leroy, Adam K.

    2014-05-20

    We use the observed radial profiles of the mass surface densities of total, Σ {sub g}, and molecular, Σ{sub H2}, gas, rotation velocity, and star formation rate (SFR) surface density, Σ{sub sfr}, of the molecular-rich (Σ{sub H2} ≥ Σ{sub HI}/2) regions of 16 nearby disk galaxies to test several star formation (SF) laws: a 'Kennicutt-Schmidt (K-S)' law, Σ{sub sfr}=A{sub g}Σ{sub g,2}{sup 1.5}; a 'Constant Molecular' law, Σ{sub sfr} = A {sub H2}Σ{sub H2,2}; the turbulence-regulated laws of Krumholz and McKee (KM05) and Krumholz, McKee, and Tumlinson (KMT09); a 'Gas-Ω' law, Σ{sub sfr}=B{sub Ω}Σ{sub g}Ω; and a shear-driven 'giant molecular cloud (GMC) Collision' law, Σ{sub sfr} = B {sub CC}Σ {sub g}Ω(1-0.7β), where β ≡ d ln v {sub circ}/d ln r. If allowed one free normalization parameter for each galaxy, these laws predict the SFR with rms errors of factors of 1.4-1.8. If a single normalization parameter is used by each law for the entire galaxy sample, then rms errors range from factors of 1.5-2.1. Although the Constant Molecular law gives the smallest rms errors, the improvement over the KMT, K-S, and GMC Collision laws is not especially significant, particularly given the different observational inputs that the laws utilize and the scope of included physics, which ranges from empirical relations to detailed treatment of interstellar medium processes. We next search for systematic variation of SF law parameters with local and global galactic dynamical properties of disk shear rate (related to β), rotation speed, and presence of a bar. We demonstrate with high significance that higher shear rates enhance SF efficiency per local orbital time. Such a trend is expected if GMC collisions play an important role in SF, while an opposite trend would be expected if the development of disk gravitational instabilities is the controlling physics.

  3. A Test of Star Formation Laws in Disk Galaxies. II. Dependence on Dynamical Properties

    NASA Astrophysics Data System (ADS)

    Suwannajak, Chutipong; Tan, Jonathan C.; Leroy, Adam K.

    2014-05-01

    We use the observed radial profiles of the mass surface densities of total, Σ g , and molecular, ΣH2, gas, rotation velocity, and star formation rate (SFR) surface density, Σsfr, of the molecular-rich (ΣH2 >= ΣHI/2) regions of 16 nearby disk galaxies to test several star formation (SF) laws: a "Kennicutt-Schmidt (K-S)" law, \\Sigma _{sfr}=A_g\\Sigma _{g,2}^{1.5}; a "Constant Molecular" law, Σsfr = A H2ΣH2, 2; the turbulence-regulated laws of Krumholz & McKee (KM05) and Krumholz, McKee, & Tumlinson (KMT09); a "Gas-Ω" law, \\Sigma _{sfr}=B_\\Omega \\Sigma _g\\Omega; and a shear-driven "giant molecular cloud (GMC) Collision" law, Σsfr = B CCΣ g Ω(1-0.7β), where β ≡ d ln v circ/d ln r. If allowed one free normalization parameter for each galaxy, these laws predict the SFR with rms errors of factors of 1.4-1.8. If a single normalization parameter is used by each law for the entire galaxy sample, then rms errors range from factors of 1.5-2.1. Although the Constant Molecular law gives the smallest rms errors, the improvement over the KMT, K-S, and GMC Collision laws is not especially significant, particularly given the different observational inputs that the laws utilize and the scope of included physics, which ranges from empirical relations to detailed treatment of interstellar medium processes. We next search for systematic variation of SF law parameters with local and global galactic dynamical properties of disk shear rate (related to β), rotation speed, and presence of a bar. We demonstrate with high significance that higher shear rates enhance SF efficiency per local orbital time. Such a trend is expected if GMC collisions play an important role in SF, while an opposite trend would be expected if the development of disk gravitational instabilities is the controlling physics.

  4. Effect of local environment and stellar mass on galaxy quenching at 0.3 < z < 2.5 in ZFOURGE

    NASA Astrophysics Data System (ADS)

    Kawinwanichakij, Lalitwadee; Papovich, Casey J.; Quadri, Ryan; ZFOURGE Team

    2017-01-01

    We study the effects of stellar mass and local environment on the star-formation activity of galaxies at 0.3 < z < 2.5 with log(M/MSun) > 8.8 using the data from the FourStar Galaxy Evolution Survey (ZFOURGE), which is a deep near-infrared survey with the FourStar camera on Magellan. The medium-band filters from ZFOURGE provide well-constrained photometric redshifts at 1 < z < 4. This accurate photometric redshift measurement allows us to estimate the environmental densities around galaxies. We apply two local projected density estimators -- a Bayesian local density estimator and the traditional Nth nearest neighbor -- on a mock galaxy catalog to demonstrate that the Bayesian local density estimator with N = 3, where distances to the first, second, and third near neighbors are all incorporated, is better correlated with the spectroscopic density estimator in comparison with the traditional 3th nearest neighbor. We find a higher quiescent fraction of galaxies in denser environments even at fixed mass out to at least z ˜ 2, but the effect is weaker than at z < 1. We quantify environmental quenching by comparing the quiescent fractions at fixed stellar mass and redshift in low-density environment to those in high-density environment. Similarly, we quantify mass quenching by comparing the quiescent fractions of our lowest-mass galaxy sample in high-density environment to those of more massive galaxies in the same environment. At all redshifts, mass-quenching is a dominant quenching mechanism for massive galaxies (log(M/MSun) >10.2). At z < 1.0, in the high-density environment, an environmental quenching process increases its contribution to suppress the star-formation, and eventually it is a dominant quenching mechanism for lowest-mass galaxies relative to mass-quenching process. We do not find any difference in the morphologies of quiescent galaxies in high- and low-density environments, suggesting that quiescent galaxies in high-density region have been quenched due

  5. Second launch of the Diffuse X-ray emission from the Local Galaxy (DXL) mission

    NASA Astrophysics Data System (ADS)

    Mohan Sapkota, Dhaka

    2016-04-01

    The Diffuse X-ray emission from the Local Galaxy (DXL) is a sounding rocket mission to study the Solar Wind Charge Exchange (SWCX) and Local Hot Bubble (LHB) X-ray emission. After a successful launch of December 2012, DXL’s capabilities were expanded by using two additional proportional counters and three unique filters for the launch of December 2015. Employing Be-, B- and C-based plastic filters, DXL mission re-scanned the Helium Focusing Cone for better spectral and positional information (to address the IBEX controversy). In this paper, we will review the upgraded mission hardware and performance, while sharing some preliminary results from the latest observation.Submitted for the DXL Collaboration

  6. Bayesian approaches to infer the physical properties of star-forming galaxies at cosmic dawn

    NASA Astrophysics Data System (ADS)

    Salmon, Brett Weston Killebrew

    In this thesis, I seek to advance our understanding of galaxy formation and evolution in the early universe. Using the largest single project ever conducted by the Hubble Space Telescope (the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, CANDELS) I use deep and wide broadband photometric imaging to infer the physical properties of galaxies from z=8.5 to z=1.5. First, I will present a study that extends the relationship between the star-formation rates (SFRs) and stellar masses (M⋆) of galaxies to 3.5galaxy SFRs, I then place new constrains on how dust is attenuated in galaxies. I calculate the Bayesian evidence for galaxies under different assumptions of their underlying dust-attenuation law. By modeling galaxy ultraviolet-to-near-IR broadband CANDELS data I produce Bayesian evidence towards the dust law in individual galaxies that is confirmed by their observed IR luminosities. Moreover, I find a tight correlation between the strength of attenuation in galaxies and their dust law, a relation reinforced by the results from radiative transfer simulations. Finally, I use the Bayesian methods developed in this thesis to study the number density of SFR in galaxies from z=8 to z=4, and resolve the current disconnect between its evolution and that of the stellar mass function. In doing so, I place the first constraints on the dust law of z>4 galaxies, finding it obeys a similar relation as found at z˜2. I find a clear excess in number density at high SFRs. This new SFR function is in better agreement with the observed stellar mass functions, the few to-date infrared detections at high redshifts, and the connection to the observed distribution of lower redshift infrared sources. Together, these studies greatly improve our understanding of the

  7. TYPE Ia SUPERNOVA PROPERTIES AS A FUNCTION OF THE DISTANCE TO THE HOST GALAXY IN THE SDSS-II SN SURVEY

    SciTech Connect

    Galbany, Lluis; Miquel, Ramon; Oestman, Linda; Brown, Peter J.; Olmstead, Matthew D.; Cinabro, David; D'Andrea, Chris B.; Nichol, Robert C.; Frieman, Joshua; Jha, Saurabh W.; Marriner, John; Nordin, Jakob; Sako, Masao; Schneider, Donald P.; Smith, Mathew; Sollerman, Jesper; Pan, Kaike; Snedden, Stephanie; Bizyaev, Dmitry; Brewington, Howard; and others

    2012-08-20

    We use Type Ia supernovae (SNe Ia) discovered by the Sloan Digital Sky Survey-II SN Survey to search for dependencies between SN Ia properties and the projected distance to the host-galaxy center, using the distance as a proxy for local galaxy properties (local star formation rate, local metallicity, etc.). The sample consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at redshifts below 0.25. The sample is split into two groups depending on the morphology of the host galaxy. We fit light curves using both MLCS2K2 and SALT2, and determine color (A{sub V} , c) and light-curve shape ({Delta}, x{sub 1}) parameters for each SN Ia, as well as its residual in the Hubble diagram. We then correlate these parameters with both the physical and the normalized distances to the center of the host galaxy and look for trends in the mean values and scatters of these parameters with increasing distance. The most significant (at the 4{sigma} level) finding is that the average fitted A{sub V} from MLCS2K2 and c from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies. We also find indications that supernovae (SNe) in elliptical galaxies tend to have narrower light curves if they explode at larger distances, although this may be due to selection effects in our sample. We do not find strong correlations between the residuals of the distance moduli with respect to the Hubble flow and the galactocentric distances, which indicates a limited correlation between SN magnitudes after standardization and local host metallicity.

  8. Type Ia Supernova Properties as a Function of the Distance to the Host Galaxy in the SDSS-II SN Survey

    SciTech Connect

    Galbany, Lluis; et al.

    2012-08-20

    We use type-Ia supernovae (SNe Ia) discovered by the SDSS-II SN Survey to search for dependencies between SN Ia properties and the projected distance to the host galaxy center, using the distance as a proxy for local galaxy properties (local star-formation rate, local metallicity, etc.). The sample consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at redshifts below 0.25. The sample is split into two groups depending on the morphology of the host galaxy. We fit light-curves using both MLCS2k2 and SALT2, and determine color (AV, c) and light-curve shape (delta, x1) parameters for each SN Ia, as well as its residual in the Hubble diagram. We then correlate these parameters with both the physical and the normalized distances to the center of the host galaxy and look for trends in the mean values and scatters of these parameters with increasing distance. The most significant (at the 4-sigma level) finding is that the average fitted AV from MLCS2k2 and c from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies. We also find indications that SNe in elliptical galaxies tend to have narrower light-curves if they explode at larger distances, although this may be due to selection effects in our sample. We do not find strong correlations between the residuals of the distance moduli with respect to the Hubble flow and the galactocentric distances, which indicates a limited correlation between SN magnitudes after standardization and local host metallicity.

  9. OmegaWINGS: The First Complete Census of Post-starburst Galaxies in Clusters in the Local Universe

    NASA Astrophysics Data System (ADS)

    Paccagnella, A.; Vulcani, B.; Poggianti, B. M.; Fritz, J.; Fasano, G.; Moretti, A.; Jaffé, Yara L.; Biviano, A.; Gullieuszik, M.; Bettoni, D.; Cava, A.; Couch, W.; D’Onofrio, M.

    2017-04-01

    Galaxies that abruptly interrupt their star formation in < 1.5 {Gyr} present recognizable features in their spectra (no emission and Hδ in absorption) and are called post-starburst (PSB) galaxies. By studying their stellar population properties and their location within the clusters, we obtain valuable insights on the physical processes responsible for star formation quenching. We present the first complete characterization of PSB galaxies in clusters at 0.04< z< 0.07, based on WINGS and OmegaWINGS data, and contrast their properties to those of passive (PAS) and emission-line (EML) galaxies. For V< 20, PSBs represent 7.2 ± 0.2% of cluster galaxies within 1.2 virial radii. Their incidence slightly increases from the outskirts toward the cluster center and from the least toward the most luminous and massive clusters, defined in terms of X-ray luminosity and velocity dispersion. The phase-space analysis and velocity-dispersion profile suggest that PSBs represent a combination of galaxies with different accretion histories. Moreover, PSBs with the strongest Hδ are consistent with being recently accreted. PSBs have stellar masses, magnitudes, colors, and morphologies intermediate between PAS and EML galaxies, typical of a population in transition from being star-forming to passive. Comparing the fraction of PSBs to the fraction of galaxies in transition on longer timescales, we estimate that the short-timescale star formation quenching channel contributes two times more than the long timescale one to the growth of the passive population. Processes like ram-pressure stripping and galaxy–galaxy interactions are more efficient than strangulation in affecting star formation.

  10. Segmented nanowires displaying locally controllable properties

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2013-03-05

    Vapor-liquid-solid growth of nanowires is tailored to achieve complex one-dimensional material geometries using phase diagrams determined for nanoscale materials. Segmented one-dimensional nanowires having constant composition display locally variable electronic band structures that are determined by the diameter of the nanowires. The unique electrical and optical properties of the segmented nanowires are exploited to form electronic and optoelectronic devices. Using gold-germanium as a model system, in situ transmission electron microscopy establishes, for nanometer-sized Au--Ge alloy drops at the tips of Ge nanowires (NWs), the parts of the phase diagram that determine their temperature-dependent equilibrium composition. The nanoscale phase diagram is then used to determine the exchange of material between the NW and the drop. The phase diagram for the nanoscale drop deviates significantly from that of the bulk alloy.

  11. How does metallicity affect the gas and dust properties of galaxies?

    NASA Astrophysics Data System (ADS)

    Madden, Suzanne C.; Cormier, Diane; Rémy-Ruyer, Aurélie

    Comparison of the ISM properties of a wide range of metal poor galaxies with normal metal-rich galaxies reveals striking differences. We find that the combination of the low dust abundance and the active star formation results in a very porous ISM filled with hard photons, heating the dust in dwarf galaxies to overall higher temperatures than their metal-rich counterparts. This results in photodissociation of molecular clouds to greater depths, leaving relatively large PDR envelopes and difficult-to-detect CO cores. From detailed modeling of the low-metallicity ISM, we find significant fractions of CO-dark H2 - a reservoir of molecular gas not traced by CO, but present in the [CII] and [CI]-emitting envelopes. Self-consistent analyses of the neutral and ionized gas diagnostics along with the dust SED is the necessary way forward in uncovering the multiphase structure of galaxies.

  12. Properties of the Local Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Dring, Andrew R.

    1998-07-01

    We present a comprehensive overview of the Local Interstellar Medium (LISM), defined roughly as the region within 200 pc of the Sun, and list the best values for the physical properties of the LISM. We find that the LISM is a very low density environment with a neutral hydrogen density of 0.01 cm-3 with a temperature of roughly 106 K and is probably the remnant of a supernova explosion. Within this hot ionized medium exist many small partially ionized clouds with neutral hydrogen densities of order 0.1 cm-3 and temperatures around 8000 K. The best studied of these clouds is the one in which our Sun resides, termed the Local Interstellar Cloud (LIC). Because the Sun lies inside the LIC, it is seen in absorption in nearly all directions allowing a fairly accurate determination of the LIC's space motion through Doppler triangulation. The LIC is moving at 27 ± 3 km s-1 in the direction Galactic langitude = 184 ± 3o and Galactic latitude = [-]16/pm3o. The measured deuterium to hydrogen ratio for the LIC along every sightline is consistent with a value of 1.6×10-5, the best determined value being the beta Cas line of sight with D/H = 1.7/pm0.3×10-5. We also present evidence for a stellar hydrogen wall around the star epsilon Eri.

  13. Secular evolution in disk galaxies

    NASA Astrophysics Data System (ADS)

    Knapen, J. H.

    2013-05-01

    The detailed study of the different structural components of nearby galaxies can supply vital information about the secular, or internal, evolution of these galaxies which they may have undergone since their formation. We highlight a series of new studies based on the analysis of mid-infrared images of over 2000 local galaxies which we are collecting within the Spitzer Survey of Stellar Structure in Galaxies (S^4G). In particular, we discuss new results on the thick and thin disk components of galaxies, which turn out to be roughly equally massive, and whose properties indicate that the thick disks mostly formed in situ, and to a lesser degree as a result of galaxy-galaxy interactions and secular evolution. We then briefly review recent research into rings in galaxies, which are common and closely linked to secular evolution of galaxies. Finally, we report on the research into local galaxy morphology, kinematics and stellar populations that we will perform over the coming four years within the EU-funded initial training network DAGAL (Detailed Anatomy of GALaxies).

  14. CARBON-RICH DUST PRODUCTION IN METAL-POOR GALAXIES IN THE LOCAL GROUP

    SciTech Connect

    Sloan, G. C.; Matsuura, M.; Lagadec, E.; Van Loon, J. Th.; Kraemer, K. E.; McDonald, I.; Zijlstra, A. A.; Groenewegen, M. A. T.; Wood, P. R.; Bernard-Salas, J.

    2012-06-20

    We have observed a sample of 19 carbon stars in the Sculptor, Carina, Fornax, and Leo I dwarf spheroidal galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. The spectra show significant quantities of dust around the carbon stars in Sculptor, Fornax, and Leo I, but little in Carina. Previous comparisons of carbon stars with similar pulsation properties in the Galaxy and the Magellanic Clouds revealed no evidence that metallicity affected the production of dust by carbon stars. However, the more metal-poor stars in the current sample appear to be generating less dust. These data extend two known trends to lower metallicities. In more metal-poor samples, the SiC dust emission weakens, while the acetylene absorption strengthens. The bolometric magnitudes and infrared spectral properties of the carbon stars in Fornax are consistent with metallicities more similar to carbon stars in the Magellanic Clouds than in the other dwarf spheroidals in our sample. A study of the carbon budget in these stars reinforces previous considerations that the dredge-up of sufficient quantities of carbon from the stellar cores may trigger the final superwind phase, ending a star's lifetime on the asymptotic giant branch.

  15. It takes a supercluster to raise a galaxy

    NASA Astrophysics Data System (ADS)

    Lietzen, Heidi; Einasto, Maret

    2016-10-01

    The properties of galaxies depend on their environment: red, passive elliptical galaxies are usually located in denser environments than blue, star-forming spiral galaxies. This difference in galaxy populations can be detected at all scales from groups of galaxies to superclusters. In this paper, we will discuss the effect of the large-scale environment on galaxies. Our results suggest that galaxies in superclusters are more likely to be passive than galaxies in voids even when they belong to groups with the same richness. In addition, the galaxies in superclusters are also affected by the morphology of the supercluster: filament-type superclusters contain relatively more red, passive galaxies than spider-type superclusters. These results suggest that the evolution of a galaxy is not determined by its local environment alone, but the large-scale environment also affects.

  16. The frequency and properties of young tidal dwarf galaxies in nearby gas-rich groups

    NASA Astrophysics Data System (ADS)

    Lee-Waddell, K.; Spekkens, K.; Chandra, P.; Patra, N.; Cuillandre, J.-C.; Wang, J.; Haynes, M. P.; Cannon, J.; Stierwalt, S.; Sick, J.; Giovanelli, R.

    2016-08-01

    We present high-resolution Giant Metrewave Radio Telescope (GMRT) H I observations and deep Canada-France-Hawaii Telescope (CFHT) optical imaging of two galaxy groups: NGC 4725/47 and NGC 3166/9. These data are part of a multi-wavelength unbiased survey of the gas-rich dwarf galaxy populations in three nearby interacting galaxy groups. The NGC 4725/47 group hosts two tidal knots and one dwarf irregular galaxy (dIrr). Both tidal knots are located within a prominent H I tidal tail, appear to have sufficient mass (Mgas ≈ 108 M⊙) to evolve into long-lived tidal dwarf galaxies (TDGs) and are fairly young in age. The NGC 3166/9 group contains a TDG candidate, AGC 208457, at least three dIrrs and four H I knots. Deep CFHT imaging confirms that the optical component of AGC 208457 is bluer - with a 0.28 mag g - r colour - and a few Gyr younger than its purported parent galaxies. Combining the results for these groups with those from the NGC 871/6/7 group reported earlier, we find that the H I properties, estimated stellar ages and baryonic content of the gas-rich dwarfs clearly distinguish tidal features from their classical counterparts. We optimistically identify four potentially long-lived tidal objects associated with three separate pairs of interacting galaxies, implying that TDGs are not readily produced during interaction events as suggested by some recent simulations. The tidal objects examined in this survey also appear to have a wider variety of properties than TDGs of similar mass formed in current simulations of interacting galaxies, which could be the result of pre- or post-formation environmental influences.

  17. First-Ever Census of Variable Mira-Type Stars in Galaxy Outside the Local Group

    NASA Astrophysics Data System (ADS)

    2003-05-01

    First-Ever Census of Variable Mira-Type Stars in Galaxy Outsidethe Local Group Summary An international team led by ESO astronomer Marina Rejkuba [1] has discovered more than 1000 luminous red variable stars in the nearby elliptical galaxy Centaurus A (NGC 5128) . Brightness changes and periods of these stars were measured accurately and reveal that they are mostly cool long-period variable stars of the so-called "Mira-type" . The observed variability is caused by stellar pulsation. This is the first time a detailed census of variable stars has been accomplished for a galaxy outside the Local Group of Galaxies (of which the Milky Way galaxy in which we live is a member). It also opens an entirely new window towards the detailed study of stellar content and evolution of giant elliptical galaxies . These massive objects are presumed to play a major role in the gravitational assembly of galaxy clusters in the Universe (especially during the early phases). This unprecedented research project is based on near-infrared observations obtained over more than three years with the ISAAC multi-mode instrument at the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory . PR Photo 14a/03 : Colour image of the peculiar galaxy Centaurus A . PR Photo 14b/03 : Location of the fields in Centaurus A, now studied. PR Photo 14c/03 : "Field 1" in Centaurus A (visual light; FORS1). PR Photo 14d/03 : "Field 2" in Centaurus A (visual light; FORS1). PR Photo 14e/03 : "Field 1" in Centaurus A (near-infrared; ISAAC). PR Photo 14f/03 : "Field 2" in Centaurus A (near-infrared; ISAAC). PR Photo 14g/03 : Light variation of six variable stars in Centaurus A PR Photo 14h/03 : Light variation of stars in Centaurus A (Animated GIF) PR Photo 14i/03 : Light curves of four variable stars in Centaurus A. Mira-type variable stars Among the stars that are visible in the sky to the unaided eye, roughly one out of three hundred (0.3%) displays brightness variations and is referred to by astronomers as a

  18. Probing The Stellar, Gaseous, And Dust Properties Of Galaxies Through Analysis Of Their Spectral Energy Distributions

    NASA Astrophysics Data System (ADS)

    Eufrasio, Rafael T.

    The spectral energy distributions (SEDs) of galaxies are shaped by their physical properties and they are our primary source of information on galaxies stellar, gaseous, and dust content. Nearby galaxies (less than 100 Mpc away) are spatially resolved by current telescopes from the ultraviolet (UV) to radio wavelengths, allowing the study of the SEDs of subgalactic regions. Such studies are necessary for deriving maps and spatial trends of the physical properties across a galaxy. In principle, the complex history of the formation, growth, and evolution of a galaxy or a region of a galaxy can be inferred from its radiative output. In practice, this task is complicated by the fact that a significant fraction of the star formation activity takes place in dust obscured regions, in which a significant fraction of the stellar radiative output is absorbed, scattered, and reradiated by the gas and dust in the interstellar medium (ISM). This reprocessing of the stellar radiation takes place in ionized interstellar gas regions (H II regions) surrounding massive hot stars, in diffuse atomic gas (H I regions), and in dense molecular clouds. For this work, we have analyzed two galaxies in detail, NGC 6872 and NGC 6946, also known as Condor and Fireworks Galaxy, respectively. The Condor galaxy is the largest-known spiral galaxy. It is part a group of galaxies, the Pavo group, with 12 other galaxies. It has, however, interacted in the past ~150 Myr with a smaller companion, previously believed to have shaped the physical extent of the giant spiral. We have performed detailed SED fitting from the UV to mid-infrared (mid-IR) to obtain star formation histories of seventeen sub-galactic regions across the Condor. These regions are large enough to be galaxies themselves, with 32.3 million light-years in diameter. We find that the Condor was already very massive before this interaction and that it was much less affected by the passage of the companion than previously thought. We also

  19. A census of AGB stars in Local Group galaxies. II. NGC 185 and NGC 147

    NASA Astrophysics Data System (ADS)

    Nowotny, W.; Kerschbaum, F.; Olofsson, H.; Schwarz, H. E.

    2003-05-01

    We present results of our ongoing photometric survey of Local Group galaxies, using a four filter technique based on the method of Wing (\\cite{Wing71}) to identify and characterise the late-type stellar content. Two narrow band filters centred on spectral features of TiO and CN allow us to distinguish between AGB stars of different chemistries [M-type (O-rich) and C-type (C-rich)]. The major parts of two dwarf galaxies of the M 31 subgroup - NGC 185 and NGC 147 - were observed. From photometry in V and i we estimate the tip of the RGB, and derive distance moduli respectively. With additional photometric data in the narrow band filters TiO and CN we identify 154 new AGB carbon stars in NGC 185 and 146 in NGC 147. C/M ratios are derived, as well as mean absolute magnitudes , bolometric magnitudes M_bol, luminosity functions, and the spatial/radial distributions of the C stars in both galaxies. 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. Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strabg.fr/cgi-bin/qcat?J/A+A/403/93

  20. X-ray Source Population Study of the Local Group Galaxy M 31

    NASA Astrophysics Data System (ADS)

    Stiele, Holger

    2010-11-01

    This dissertation presents the analysis of a large and deep XMM-Newton survey of the second large Local Group spiral galaxy M31. The survey observations, taken between June 2006 and February 2008, together with re-analysed archival observations from June 2000 to July 2004 cover, for the first time, the whole D25 ellipse of M 31 with XMM-Newton down to a limiting luminosity of ˜10^35 erg s-1 in the 0.2-4.5 keV band. The main goal of the thesis was a study of the different source populations of M 31 that can be observed in X-rays. Therefore a catalogue was created, which contains all 1 948 sources detected in the 0.2 - 12.0 keV range. 961 of these sources were detected in X-rays for the first time. Source classification and identification was based on X-ray hardness ratios, spatial extent of the sources, and by cross correlating with catalogues in the X-ray, optical, infrared and radio wavelengths. An additional classification criterion was the long-term temporal variability of the sources in X-rays. This variability allows us to distinguish between X-ray binaries and active galactic nuclei. Furthermore, supernova remnant classifications of previous studies that did not use long-term variability as a classification criterion, could be validated. Including previous Chandra and ROSAT observations in the long-term variability study allowed me to detect additional transient or at least highly variable sources, which are good candidates for being X-ray binaries. Fourteen of the 40 supersoft source (SSS) candidates correlated with optical novae and therefore can be considered the supersoft emission of the optical novae. Among them is the first nova/SSS detected in a globular cluster of M 31. Correlations with previous ROSAT and Chandra studies revealed that only three SSSs are visible for at least one decade. This result underlines the strong long-term variability found for the class of SSSs. In addition the correlations demonstrated that strict selection criteria have to

  1. The SAURON Project - XIV. No escape from Vesc: a global and local parameter in early-type galaxy evolution

    NASA Astrophysics Data System (ADS)

    Scott, Nicholas; Cappellari, Michele; Davies, Roger L.; Bacon, R.; de Zeeuw, P. T.; Emsellem, Eric; Falcón-Barroso, Jésus; Krajnović, Davor; Kuntschner, Harald; McDermid, Richard M.; Peletier, Reynier F.; Pipino, Antonio; Sarzi, Marc; van den Bosch, Remco C. E.; van de Ven, Glenn; van Scherpenzeel, Eveline

    2009-10-01

    We present the results of an investigation of the local escape velocity (Vesc) - line strength index relationship for 48 early-type galaxies from the SAURON sample, the first such study based on a large sample of galaxies with both detailed integral field observations and extensive dynamical modelling. Values of Vesc are computed using multi-Gaussian expansion (MGE) photometric fitting and axisymmetric, anisotropic Jeans' dynamical modelling simultaneously on Hubble Space Telescope and ground-based images. We determine line strengths and escape velocities at multiple radii within each galaxy, allowing an investigation of the correlation within individual galaxies as well as amongst galaxies. We find a tight correlation between Vesc and the line-strength indices. For Mgb, we find that this correlation exists not only between different galaxies but also inside individual galaxies - it is both a local and global correlation. The Mgb-Vesc relation has the form: log(Mgb/4Å) = (0.32 +/- 0.03) log(Vesc/500km s-1) - (0.031 +/- 0.007) with an rms scatter σ = 0.033. The relation within individual galaxies has the same slope and offset as the global relation to a good level of agreement, though there is significant intrinsic scatter in the local gradients. We transform our line strength index measurements to the single stellar population (SSP) equivalent ages (t), metallicity ([Z/H]) and enhancement ([α/Fe]) and carry out a principal component analysis of our SSP and Vesc data. We find that in this four-dimensional parameter space the galaxies in our sample are to a good approximation confined to a plane, given by log (V esc/500 kms -1) = 0.85 [Z/H] + 0.43 log (t/Gyr) - 0.29. It is surprising that a combination of age and metallicity is conserved; this may indicate a `conspiracy' between age and metallicity or a weakness in the SSP models. How the connection between stellar populations and the gravitational potential, both locally and globally, is preserved as galaxies

  2. A Local Baseline of the Black Hole Mass Scaling Relations for Active Galaxies. III.The MBH - σ Relation

    NASA Astrophysics Data System (ADS)

    Bennert, Vardha N.; Treu, Tommaso; Auger, Matthew W.; Cosens, Maren; Park, Daeseong; Rosen, Rebecca; Harris, Chelsea E.; Malkan, Matthew A.; Woo, Jong-Hak

    2015-08-01

    We create a baseline of the black hole (BH) mass (MBH)—stellar-velocity dispersion (σ) relation for active galaxies, using a sample of 66 local (0.02galaxies, selected from the Sloan Digital Sky Survey (SDSS). Analysis of SDSS images yields AGN luminosities free of host-galaxy contamination, and morphological classification. 51/66 galaxies have spiral morphology. Out of these, 28 bulges have Sérsic index n<2 and are considered candidate pseudo-bulges, with eight being definite pseudo-bulges based on multiple classification criteria met. Only 4/66 galaxies show signs of interaction/merging. High signal-to-noise ratio Keck spectra provide the width of the broad Hβ emission line free of Fe ii emission and stellar absorption. AGN luminosity and Hβ line widths are used to estimate MBH. The Keck-based spatially resolved kinematics is used to determine stellar-velocity dispersion within the spheroid effective radius (σ spat,reff). We find that σ can vary on average by up to 40% across definitions commonly used in the literature, emphasizing the importance of using self-consistent definitions in comparisons and evolutionary studies. The MBH-σ relation for our Seyfert-1 galaxy sample has the same intercept and scatter as that of reverberation-mapped AGNs as well as that of quiescent galaxies, consistent with the hypothesis that our single epoch MBH estimator and sample selection function do not introduce significant biases. Barred galaxies, merging galaxies, and those hosting pseudo-bulges do not represent outliers in the MBH-σ relation. This is in contrast with previous work, although no firm conclusion can be drawn on this matter due to the small sample size and limited resolution of the SDSS images.

  3. The Nobeyama 45 m 12CO(J=1-0) Survey of local Luminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Yamashita, Takuji; Komugi, Shinya; Matsuhara, Hideo; Armus, Lee; Inami, Hanae; Ueda, Junko; Iono, Daisuke; Kohno, Kotaro; Stierwalt, Sabrina; Arimatsu, Ko; Evans, Aaron

    2015-08-01

    Cold molecular gas and star formation in local Luminous Infrared Galaxies (LIRGs) are studied along the stage of the galaxy merger sequence. Most local LIRGs are starbursting and are involved with galaxy-galaxy interactions or mergers. The evolution and the direct trigger of the merger-driven starbursts are not clear observationally, although there are several theoretical explanations. In order to address these issues, information of the molecular gas, which is traced by a 12CO(J=1-0) emission line, of an unbiased LIRG sample is required. To this end, a CO survey of 79 galaxies in 62 LIRG systems were conducted with the Nobeyama 45 m telescope. A method is developed to estimate the extent of CO gas in galaxies using combinations of two single-aperture telescopes with different beam sizes. The majority of the sources have the CO radius of less than ~ 4 kpc. The CO extent is found to possibly decrease from the early stage to the late stage of the merger. The molecular gas mass in the central several kilo-parsecs is constant throughout the merger sequence. These results statistically support a theoretically predicted scenario where the global gas inflow towards the galaxy center is common in merging LIRGs. The star formation efficiencies (SFE) in the central regions are derived and are high compared to disk star-forming galaxies as is well known. The SFE are found to be fairly independent of the merger stage. The star formation of merging LIRGs may be controlled by a common relation from gas to stars regardless of the merger stage, where SFR and resultant IR luminosity are determined by the amount of the molecular gas supplied by global inflow.

  4. Stellar Tidal Streams in Spiral Galaxies of the Local Volume: A Pilot Survey with Modest Aperture Telescopes

    NASA Astrophysics Data System (ADS)

    Martínez-Delgado, David; Gabany, R. Jay; Crawford, Ken; Zibetti, Stefano; Majewski, Steven R.; Rix, Hans-Walter; Fliri, Jürgen; Carballo-Bello, Julio A.; Bardalez-Gagliuffi, Daniella C.; Peñarrubia, Jorge; Chonis, Taylor S.; Madore, Barry; Trujillo, Ignacio; Schirmer, Mischa; McDavid, David A.

    2010-10-01

    Within the hierarchical framework for galaxy formation, minor merging and tidal interactions are expected to shape all large galaxies to the present day. As a consequence, most seemingly normal disk galaxies should be surrounded by spatially extended stellar "tidal features" of low surface brightness. As part of a pilot survey for such interaction signatures, we have carried out ultra deep, wide field imaging of eight isolated spiral galaxies in the Local Volume, with data taken at small (D = 0.1-0.5 m) robotic telescopes that provide exquisite surface brightness sensitivity (μlim(V) ~ 28.5 mag arcsec-2). This initial observational effort has led to the discovery of six previously undetected extensive (to ~30 kpc) stellar structures in the halos surrounding these galaxies, likely debris from tidally disrupted satellites. In addition, we confirm and clarify several enormous stellar over-densities previously reported in the literature, but never before interpreted as tidal streams. Even this pilot sample of galaxies exhibits strikingly diverse morphological characteristics of these extended stellar features: great circle-like features that resemble the Sagittarius stream surrounding the Milky Way, remote shells and giant clouds of presumed tidal debris far beyond the main stellar body, as well as jet-like features emerging from galactic disks. Together with presumed remains of already disrupted companions, our observations also capture surviving satellites caught in the act of tidal disruption. A qualitative comparison with available simulations set in a ΛCold Dark Matter cosmology (that model the stellar halo as the result of satellite disruption evolution) shows that the extraordinary variety of stellar morphologies detected in this pilot survey matches that seen in those simulations. The common existence of these tidal features around "normal" disk galaxies and the morphological match to the simulations constitutes new evidence that these theoretical models also

  5. Are the Faraday Rotating Magnetic Fields Local to Intracluster Radio Galaxies?

    NASA Astrophysics Data System (ADS)

    Ensslin, Torsten A.; Vogt, Corina; Clarke, T. E.; Taylor, Greg B.

    2003-11-01

    We investigate the origin of the high Faraday rotation measures (RMs) found for polarized radio galaxies in clusters. The two most likely origins are magnetic fields local to the source or magnetic fields located in the foreground intracluster medium. The latter is identified as the null hypothesis. Rudnick & Blundell have recently suggested that the presence of magnetic fields local to the source may be revealed in correlations of the position angles (PAs) of the source-intrinsic linear polarization and the RMs. We investigate the claim of Rudnick & Blundell that they have found a relationship between the intrinsic PA0 of the radio source PKS 1246-410 and its RM by testing the clustering strength of the PA0-RM scatter plot. We show that the claimed relationship is an artifact of an improperly performed null experiment. We describe a gradient alignment statistic aimed at finding correlations between PA0 and RM maps. This statistic does not require any null experiment since it gives a unique (zero) result in the case of uncorrelated maps. We apply it to a number of extended radio sources in galaxy clusters (PKS 1246-410, Cygnus A, Hydra A, and 3C 465). In no case is a significant large-scale alignment of PA0 and RM maps detected. We find significant small-scale co-alignment in all cases, but we are able to fully identify this with map-making artifacts through a suitable statistical test. We conclude that there is presently no existing evidence for Faraday rotation local to radio lobes. Given the existing independent pieces of evidence, we favor the null hypothesis that the observed Faraday screens are produced by intracluster magnetic fields.

  6. A multiwavelength study of the IRAS Deep Survey galaxy sample. III. Spectral classification and dynamical properties

    NASA Astrophysics Data System (ADS)

    Bettoni, D.; Mazzei, P.; Della Valle, A.

    2012-02-01

    Context. The infrared deep sample (IDS), in the north ecliptical polar region (NEPR), is the first complete, far-IR selected sample, on which numerous studies of galaxy evolution are based. Such a sample allows direct investigation of the evolution of dusty galaxies up to a redshift of about 0.3, where the global star formation rate is known to evolve very fast. As discussed in previous papers, we performed optical and IR (ISOCAM, 15 μm,) follow-up of its galaxies and exploited our IR observations to correct the 60 μm fluxes for confusion effects and observational biases. In them we found indications of a significant incompleteness of IDS sample below S(60) ≃ 80 mJy. We constructed 15 μm and far-IR (60 μm) luminosity functions of a complete sample of 56 ISO/IRAS sources. Aims: Here we present and analyze the spectral classification of several galaxies in the IDS sample together with rotation curves which allow estimating the lower mass limits of a subsample of objects. Methods: We measured fluxes and intensity ratios of the emission lines in the visible region of the spectrum (λ4000-9000 Å) for 75 galaxy members. Moreover, for some of them (55%), the spectra obtained with the Keck II telescope have sufficient wavelength and spatial resolution to derive their rotation curve. Results: These galaxies turn out to be disk like systems, with a high fraction (~50%) of interacting systems. The spectroscopic classification of 42 galaxies, using the emission-line ratio diagnostic diagrams, shows that the NEPR sample is predominantly composed of starburst galaxies (71%), while the fraction of AGNs (7%) and LINERs (21%) is small. The dynamical analysis allows us to estimate the lower mass limits of 39 galaxies. Conclusions: The rest-frame FIR luminosity distribution of these galaxies spans the same range as that of the FIR selected complete sample, i.e. three orders of magnitude, with the same mean value, log(LFIR) = 10.2. This emphasizes that such galaxies represent

  7. Galaxy population properties of the massive X-ray luminous galaxy cluster XDCP J0044.0-2033 at z = 1.58. Red-sequence formation, massive galaxy assembly, and central star formation activity

    NASA Astrophysics Data System (ADS)

    Fassbender, R.; Nastasi, A.; Santos, J. S.; Lidman, C.; Verdugo, M.; Koyama, Y.; Rosati, P.; Pierini, D.; Padilla, N.; Romeo, A. D.; Menci, N.; Bongiorno, A.; Castellano, M.; Cerulo, P.; Fontana, A.; Galametz, A.; Grazian, A.; Lamastra, A.; Pentericci, L.; Sommariva, V.; Strazzullo, V.; Šuhada, R.; Tozzi, P.

    2014-08-01

    Context. Recent observational progress has enabled the detection of galaxy clusters and groups out to very high redshifts and for the first time allows detailed studies of galaxy population properties in these densest environments in what was formerly known as the "redshift desert" at z> 1.5. Aims: We aim to investigate various galaxy population properties of the massive X-ray luminous galaxy cluster XDCP J0044.0-2033 at z = 1.58, which constitutes the most extreme currently known matter-density peak at this redshift. Methods: We analyzed deep VLT/HAWK-I near-infrared data with an image quality of 0.5'' and limiting Vega magnitudes (50% completeness) of 24.2 in J- and 22.8 in the Ks band, complemented by similarly deep Subaru imaging in i and V, Spitzer observations at 4.5 μm, and new spectroscopic observations with VLT/FORS 2. Results: We detect a cluster-associated excess population of about 90 galaxies, most of them located within the inner 30'' (250 kpc) of the X-ray centroid, which follows a centrally peaked, compact NFW galaxy surface-density profile with a concentration of c200 ≃ 10. Based on the Spitzer 4.5 μm imaging data, we measure a total enclosed stellar mass of M∗500 ≃ (6.3 ± 1.6) × 1012 M⊙ and a resulting stellar mass fraction of f∗,500 = M∗,500/M500 = (3.3 ± 1.4)%, consistent with local values. The total J- and Ks-band galaxy luminosity functions of the core region yield characteristic magnitudes J* and Ks* consistent with expectations from simple zf = 3 burst models. However, a detailed look at the morphologies and color distributions of the spectroscopically confirmed members reveals that the most massive galaxies are undergoing a very active mass-assembly epoch through merging processes. Consequently, the bright end of the cluster red sequence is not in place, while a red-locus population is present at intermediate magnitudes [Ks*, Ks* + 1.6], which is then sharply truncated at magnitudes fainter than Ks* + 1.6. The dominant

  8. The Horizon-AGN simulation: evolution of galaxy properties over cosmic time

    NASA Astrophysics Data System (ADS)

    Kaviraj, S.; Laigle, C.; Kimm, T.; Devriendt, J. E. G.; Dubois, Y.; Pichon, C.; Slyz, A.; Chisari, E.; Peirani, S.

    2017-01-01

    We compare the predictions of Horizon-AGN, a hydro-dynamical cosmological simulation that uses an adaptive mesh refinement code, to observational data in the redshift range 0 < z < 6. We study the reproduction, by the simulation, of quantities that trace the aggregate stellar-mass growth of galaxies over cosmic time: luminosity and stellar-mass functions, the star formation main sequence, rest-frame UV-optical-near infrared colours and the cosmic star-formation history. We show that Horizon-AGN, which is not tuned to reproduce the local Universe, produces good overall agreement with these quantities, from the present day to the epoch when the Universe was 5% of its current age. By comparison to Horizon-noAGN, a twin simulation without AGN feedback, we quantify how feedback from black holes is likely to help shape galaxy stellar-mass growth in the redshift range 0 < z < 6, particularly in the most massive galaxies. Our results demonstrate that Horizon-AGN successfully captures the evolutionary trends of observed galaxies over the lifetime of the Universe, making it an excellent tool for studying the processes that drive galaxy evolution and making predictions for the next generation of galaxy surveys.

  9. DEEP K{sub s} -NEAR-INFRARED SURFACE PHOTOMETRY OF 80 DWARF IRREGULAR GALAXIES IN THE LOCAL VOLUME

    SciTech Connect

    Fingerhut, Robin L.; McCall, Marshall L.; Argote, Mauricio; Cluver, Michelle E.; Nishiyama, Shogo; Rekola, Rami T. F.; Richer, Michael G.; Vaduvescu, Ovidiu; Woudt, Patrick A. E-mail: mccall@yorku.c E-mail: mcluver@ipac.caltech.ed E-mail: rareko@utu.f E-mail: ovidiuv@ing.iac.e

    2010-06-10

    We present deep near-infrared (K{sub s}) images and surface photometry for 80 dwarf irregular galaxies (dIs) within {approx}5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between large-scale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies.

  10. A high-dimensional look at VIPERS galaxies

    NASA Astrophysics Data System (ADS)

    Granett, Benjamin R.; Aff002

    2014-05-01

    We investigate how galaxies in VIPERS (the VIMOS Public Extragalactic Redshift Survey) inhabit the cosmological density field by examining the correlations across the observable parameter space of galaxy properties and clustering strength. The high-dimensional analysis is made manageable by the use of group-finding and regression tools. We find that the major trends in galaxy properties can be explained by a single parameter related to stellar mass. After subtracting this trend, residual correlations remain between galaxy properties and the local environment pointing to complex formation dependencies. As a specific application of this work we build subsamples of galaxies with specific clustering properties for use in cosmological tests.

  11. Gradients of stellar population properties and evolution clues in a nearby galaxy M101

    SciTech Connect

    Lin, Lin; Kong, Xu; Lin, Xuanbin; Mao, Yewei; Cheng, Fuzhen; Zou, Hu; Jiang, Zhaoji; Zhou, Xu E-mail: xkong@ustc.edu.cn

    2013-06-01

    Multiband photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of the nearby Scd-type galaxy M101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-A {sub FUV} relation, found to depend on a second parameter of birth rate b (ratio of present- and past-averaged star formation rates), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an 'inside-out' disk growth scenario. Two distinct disk regions with different gradients of age and color are discovered, similar to another late-type galaxy, NGC 628. The metallicity gradient of the stellar content is flatter than that of H II regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower compared with galaxies of similar and earlier morphological type. We note that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar which is relatively young, metal-rich, and contains much dust.

  12. Stellar populations properties of galaxies at 4 < z < 8: strong emission lines, SFRs, and quiescence

    NASA Astrophysics Data System (ADS)

    Labbe, Ivo

    2015-08-01

    Joint HST/WFC3 and Spitzer/IRAC observations are a powerful probe of the build up of galaxies in the early universe z > 4. A particularly surprising result in recent years has been the discovery of ubiquitous strong nebular emission lines in bright 4 < z < 8 galaxies. These strongly affect fundamental estimates, such as stellar mass, but apart from being a nuisance they also carry valuable information. Systematic studies of large samples offer exciting prospects, including studying the SFR distribution and dust attenuation, improving photometric redshifts, and selecting bright high-z galaxies using IRAC over wide fields. I will introduce GREATS: GOODS Re-ionization Era wide-Area Treasury from Spitzer, the 730 hour cycle-11 exploration ultradeep Spitzer/IRAC program over GOODS-North and GOODS-South to characterise the properties of normal L* galaxies at z > 7. Such ultradeep IRAC data are also crucial to address whether we are missing important constituents of the high redshift universe, such as massive post-starburst galaxies at z > 4. Recent results from our ZFOURGE survey revealed evidence for the existence of ultracompact quiescent galaxies with substantial ages at z ~ 4, suggesting they might exist at even higher redshift. I will discuss techniques to search for them.

  13. Gradients of Stellar Population Properties and Evolution Clues in a Nearby Galaxy M101

    NASA Astrophysics Data System (ADS)

    Lin, Lin; Zou, Hu; Kong, Xu; Lin, Xuanbin; Mao, Yewei; Cheng, Fuzhen; Jiang, Zhaoji; Zhou, Xu

    2013-06-01

    Multiband photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of the nearby Scd-type galaxy M101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-A FUV relation, found to depend on a second parameter of birth rate b (ratio of present- and past-averaged star formation rates), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an "inside-out" disk growth scenario. Two distinct disk regions with different gradients of age and color are discovered, similar to another late-type galaxy, NGC 628. The metallicity gradient of the stellar content is flatter than that of H II regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower compared with galaxies of similar and earlier morphological type. We note that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar which is relatively young, metal-rich, and contains much dust.

  14. Properties of Pseudo-bulges and Classical Bulges Identified Among SDSS Galaxies

    NASA Astrophysics Data System (ADS)

    Luo, Yifei; Rodriguez, Aldo; Koo, David C.; Primack, Joel R.; Faber, Sandra M.; Guo, Yicheng; Chen, Zhu; Fang, Jerome J.; Huertas-Company, Marc

    2017-01-01

    We have used publicly-available SDSS photometry and structural parameters to classify nearby galaxies(z<0.05) into four bulge-related groups, i.e., those galaxies with : 1) no bulges; 2) pseudo-bulges; 3) classical bulges; and 4) nearly pure bulges, i. e., elliptical-like. We adopt the stellar-mass surface-density within the inner 1 kpc (Σ1) radius as a key parameter. A sample of 1000 galaxies with previously-classified bulge-types by Gadotti (2009) is used to identify the regions within the Σ1 vs integrated, stellar-mass plane of galaxies to which each bulge group belongs. In this plane, galaxies with classical bulges appear to overlap the region of elliptical galaxies, while those with pseudo-bulges or no bulges lie at lower Σ1 at a given stellar mass. In contrast to some previous results, our main finding is that the properties of pseudo-bulge and classical-bulge groups have distributions that appear mostly blended or overlapping, i.e., continuous, rather being distinct, i.e., bimodal.

  15. SPECTROSCOPY OF LUMINOUS COMPACT BLUE GALAXIES IN DISTANT CLUSTERS. II. PHYSICAL PROPERTIES OF dE PROGENITOR CANDIDATES

    SciTech Connect

    Crawford, S. M.; Wirth, Gregory D.; Bershady, M. A.; Randriamampandry, S. M. E-mail: gregory.wirth@gmail.com

    2016-02-01

    Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M > 10{sup 15} M{sub ⊙}), intermediate redshift (0.5 < z < 0.9) galaxy clusters, we present their rest-frame properties including star formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size–luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs at the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.

  16. HST-WFC3 Near-Infrared Spectroscopy of Quenched Galaxies at zeta approx 1.5 from the WISP Survey: Stellar Populations Properties

    NASA Technical Reports Server (NTRS)

    Bedregal, A. G.; Scarlata, C.; Henry, A. L.; Atek, H.; Rafelski, M.; Teplitz, H. I.; Dominguez, A.; Siana, B.; Colbert, J. W.; Malkan, M.; Ross, N. R.; Martin, C. L.; Dressler, A.; Bridge, C.; Hathi, N. P.; Masters, D.; McCarthy, P. J.; Rutkowski, M. J.

    2013-01-01

    We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3- UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 microns] photometry to assemble a sample of massive (log(Mstar/M solar mass) at approx 11.0) and quenched (specific star formation rate < 0.01 G/yr(exp -1) galaxies at zeta approx 1.5. Our sample of 41 galaxies is the largest with G102+G141 NIR spectroscopy for quenched sources at these redshifts. In contrast to the local universe, zeta approx 1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find that their spectral energy distributions (SEDs) are well fitted with exponentially decreasing star formation histories and short star formation timescales (tau less than or equal to 100 M/yr). Quenched galaxies also show a wide distribution in ages, between 1 and 4 G/yr. In the (u - r)0-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the zeta appro. 1.5 red sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies on the RS have older median ages (3.1 G/yr) than the quenched galaxies off the RS (1.5 G/yr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies off the RS. We derive the upper limit on the fraction of massive galaxies on the RS at zeta approx 1.5 to be <43%.We speculate that the young quenched galaxies off the RS are in a transition phase between vigorous star formation at zeta > 2 and the zeta approx 1.5 RS. According to their estimated ages, the time required for quenched galaxies off the RS to join their counterparts on the z approx. 1.5 RS is of the order of approx. 1G/yr.

  17. HST/WFC3 near-infrared spectroscopy of quenched galaxies at z ∼ 1.5 from the WISP survey: Stellar population properties

    SciTech Connect

    Bedregal, A. G.; Scarlata, C.; Rutkowski, M. J.; Henry, A. L.; Martin, C. L.; Atek, H.; Colbert, J. W.; Rafelski, M.; Teplitz, H. I.; Dominguez, A.; Siana, B.; Masters, D.; Malkan, M.; Ross, N. R.; Dressler, A.; Bridge, C.; Hathi, N. P.; McCarthy, P. J.

    2013-12-01

    We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3-UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 μm] photometry to assemble a sample of massive (log (M {sub star}/M {sub ☉}) ∼ 11.0) and quenched (specific star formation rate <0.01 Gyr{sup –1}) galaxies at z ∼ 1.5. Our sample of 41 galaxies is the largest with G102+G141 NIR spectroscopy for quenched sources at these redshifts. In contrast to the local universe, z ∼ 1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find that their spectral energy distributions (SEDs) are well fitted with exponentially decreasing star formation histories and short star formation timescales (τ ≤ 100 Myr). Quenched galaxies also show a wide distribution in ages, between 1 and 4 Gyr. In the (u – r){sub 0}-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the z ∼ 1.5 red sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies on the RS have older median ages (3.1 Gyr) than the quenched galaxies off the RS (1.5 Gyr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies off the RS. We derive the upper limit on the fraction of massive galaxies on the RS at z ∼ 1.5 to be <43%. We speculate that the young quenched galaxies off the RS are in a transition phase between vigorous star formation at z > 2 and the z ∼ 1.5 RS. According to their estimated ages, the time required for quenched galaxies off the RS to join their counterparts on the z ∼ 1.5 RS is of the order of ∼1 Gyr.

  18. REVERBERATION MAPPING MEASUREMENTS OF BLACK HOLE MASSES IN SIX LOCAL SEYFERT GALAXIES

    SciTech Connect

    Denney, K. D.; Peterson, B. M.; Pogge, R. W.; Atlee, D. W.; Bentz, M. C.; Bird, J. C.; Comins, M. L.; Dietrich, M.; Eastman, J. D.; Adair, A.; Au-Yong, K.; Chisholm, E.; Ewald, S.; Ferbey, S.; Jackson, K.; Brokofsky, D. J.; Gaskell, C. M.; Hedrick, C. H.; Doroshenko, V. T.

    2010-09-20

    We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved H{beta} reverberation lag measurements for several relatively low-luminosity active galactic nuclei (AGNs). We have reliably measured the time delay between variations in the continuum and H{beta} emission line in six local Seyfert 1 galaxies. These measurements are used to calculate the mass of the supermassive black hole at the center of each of these AGNs. We place our results in context to the most current calibration of the broad-line region (BLR) R{sub BLR}-L relationship, where our results remove outliers and reduce the scatter at the low-luminosity end of this relationship. We also present velocity-resolved H{beta} time-delay measurements for our complete sample, though the clearest velocity-resolved kinematic signatures have already been published.

  19. Adaptive density estimator for galaxy surveys

    NASA Astrophysics Data System (ADS)

    Saar, Enn

    2016-10-01

    Galaxy number or luminosity density serves as a basis for many structure classification algorithms. Several methods are used to estimate this density. Among them kernel methods have probably the best statistical properties and allow also to estimate the local sample errors of the estimate. We introduce a kernel density estimator with an adaptive data-driven anisotropic kernel, describe its properties and demonstrate the wealth of additional information it gives us about the local properties of the galaxy distribution.

  20. SHELS: OPTICAL SPECTRAL PROPERTIES OF WISE 22 {mu}m SELECTED GALAXIES

    SciTech Connect

    Hwang, Ho Seong; Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G.; Dell'Antonio, Ian P. E-mail: mgeller@cfa.harvard.edu E-mail: dfabricant@cfa.harvard.edu

    2012-10-10

    We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4 deg{sup 2} region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22 {mu}m selected galaxies. Among 507 WISE 22 {mu}m selected sources with (S/N){sub 22{mu}m} {>=} 3 ( Almost-Equal-To S{sub 22{mu}m} {approx}> 2.5 mJy), we identify the optical counterparts of 481 sources ({approx}98%) at R < 25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R < 21 have SHELS spectroscopic data. Most of these objects are at z < 0.8. The infrared (IR) luminosities are in the range 4.5 Multiplication-Sign 10{sup 8}(L{sub Sun }) {approx}< L{sub IR} {approx}< 5.4 Multiplication-Sign 10{sup 12}(L{sub Sun }). Most 22 {mu}m selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000 A break. The stacked spectra of the 22 {mu}m selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to H{beta} grows with increasing IR luminosity. The optical spectra of the 22 {mu}m selected galaxies also show that there are some ({approx}2.8%) unusual galaxies with very strong [Ne III] {lambda}3869, 3968 emission lines that require hard ionizing radiation such as active galactic nuclei (AGNs) or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22 {mu}m flux densities are enhanced if the 22 {mu}m selected galaxies have close late-type neighbors. The sSFR distribution of the 22 {mu}m selected galaxies containing AGNs is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy candidates with large ({approx}> 1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z {approx} 2.

  1. The EFIGI catalogue of 4458 nearby galaxies with morphology. II. Statistical properties along the Hubble sequence

    NASA Astrophysics Data System (ADS)

    de Lapparent, V.; Baillard, A.; Bertin, E.

    2011-08-01

    Aims: The EFIGI catalogue of 4458 galaxies extracted from the PGC and SDSS DR4 was designed to provide a multiwavelength reference database of the morphological properties of nearby galaxies. The sample is limited in apparent diameter and densely samples all RC3 Hubble types. Methods: We examine the statistics of the 16 EFIGI shape attributes, describing the various dynamical components, the texture, and the contamination by the environment of each galaxy. Using the redshifts from SDSS, HyperLeda, or NED for 99.53% of EFIGI galaxies, we derive estimates of absolute major isophotal diameters and the corresponding mean surface brightness in the SDSS g-band. Results: We study the variations of the EFIGI morphological attributes with Hubble type and confirm that the visual Hubble sequence is a decreasing sequence of bulge-to-total ratio and an increasing sequence of disk contribution to the total galaxy flux. There is, nevertheless, a total spread of approximately five types for a given bulge-to-total ratio, because the Hubble sequence is primarily based on the strength and pitch angle of the spiral arms, independently from the bulge-to-total ratio. A steep decrease in the presence of dust from Sb to Sbc-Sc types appears to produce the grand spiral design of the Sc galaxies. In contrast, the scattered and giant HII regions show different strength variation patterns, with peaks for types Scd and Sm; hence, they do not appear to directly participate in the establishment of the visual Hubble sequence. The distortions from a symmetric profile also incidentally increase along the sequence. Bars and inner rings are frequent and occur in 41% and 25% of the disk galaxies respectively. Outer rings are half as frequent than inner rings, and outer pseudo-rings occur in 11% of barred galaxies. Finally, we find a smooth decrease in mean surface brightness and intrinsic size along the Hubble sequence. The largest galaxies are cD, ellipticals and Sab-Sbc intermediate spirals (20

  2. Spectral Analysis of CLU Galaxies

    NASA Astrophysics Data System (ADS)

    Sutter, Jessica; Cook, David O.; Kasliwal, Mansi M.; Dale, Daniel A.

    2017-01-01

    In order to help select possible EM signals from gravitational wave-emitting sources, a more complete catalog of local galaxies is being created. This catalog, called the Census of the Local Universe (CLU), will attempt to find the position of all star-forming galaxies within 200 Mpc. By doing this, the area on the sky from which a gravitational wave could possibly have originated is reduced by a factor of 100. Besides providing this valuable resource for gravitational wave follow-up, the CLU survey provides an exciting new opportunity for better understanding the properties of galaxies near the same age as the Milky Way. Using spectra obtained with the Palomar 200-inch double-prime spectrograph as well as data from the WISE survey, we have created a main sequence for the CLU survey. By analyzing how this main sequence behaves in local galaxies, we can better understand the relationship between current star formation rate and total galaxy stellar mass.

  3. Herschel-ATLAS: far-infrared properties of radio-selected galaxies

    NASA Astrophysics Data System (ADS)

    Hardcastle, M. J.; Virdee, J. S.; Jarvis, M. J.; Bonfield, D. G.; Dunne, L.; Rawlings, S.; Stevens, J. A.; Christopher, N. M.; Heywood, I.; Mauch, T.; Rigopoulou, D.; Verma, A.; Baldry, I. K.; Bamford, S. P.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooray, A.; Croom, S. M.; Dariush, A.; de Zotti, G.; Eales, S.; Fritz, J.; Hill, D. T.; Hughes, D.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Jones, D. H.; Loveday, J.; Maddox, S. J.; Michałowski, M. J.; Negrello, M.; Norberg, P.; Pohlen, M.; Prescott, M.; Rigby, E. E.; Robotham, A. S. G.; Rodighiero, G.; Scott, D.; Sharp, R.; Smith, D. J. B.; Temi, P.; van Kampen, E.

    2010-11-01

    We use the Herschel-Astrophysical Terahertz Large Area Survey (ATLAS) science demonstration data to investigate the star formation properties of radio-selected galaxies in the GAMA-9h field as a function of radio luminosity and redshift. Radio selection at the lowest radio luminosities, as expected, selects mostly starburst galaxies. At higher radio luminosities, where the population is dominated by active galactic nuclei (AGN), we find that some individual objects are associated with high far-infrared luminosities. However, the far-infrared properties of the radio-loud population are statistically indistinguishable from those of a comparison population of radio-quiet galaxies matched in redshift and K-band absolute magnitude. There is thus no evidence that the host galaxies of these largely low-luminosity (Fanaroff-Riley class I), and presumably low-excitation, AGN, as a population, have particularly unusual star formation histories. Models in which the AGN activity in higher luminosity, high-excitation radio galaxies is triggered by major mergers would predict a luminosity-dependent effect that is not seen in our data (which only span a limited range in radio luminosity) but which may well be detectable with the full Herschel-ATLAS data set. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. E-mail: m.j.hardcastle@herts.ac.uk

  4. How does the far-IR properties of star-forming galaxies depend on environment?

    NASA Astrophysics Data System (ADS)

    Guo, Qi

    2015-08-01

    Traditionally, most observational studies estimate SFRs using rest-frame UV luminosities or emission lines, which are subject to uncertain corrections for dust extinction. In star-forming regions, UV photons heat the dust, and their energy is re-emitted in the mid- and far-IR range. About half of the starlight is absorbed and re-emitted over the history of the Universe. Observations at IR wavelengths are thus an essential complement to UV and optical tracers of star formation. We use far-IR selected galaxies from the Herschel ATLAS (H-ATLAS) survey and optically selected galaxies from the Galaxy and Mass Assembly (GAMA) redshift survey to study the environmental effects on far-IR properties. It includes the following aspects. What is the typical halo mass of the low-redshift H-ATLAS sources? How does far-IR luminosity depend on host halo mass? How do the far-IR conditional luminosity functions depend on group masses and redshifts? How is the total far-IR light-to-mass ratio in groups of different masses at different redshifts? How much of the far-IR luminosity is contributed by galaxies in groups? Are there any environmental effects on the far-IR-to-optical colour? How does the far-IR properties depend on large-scale environments? Can we pose constrains on current galaxy formation models?

  5. A Treasury Study of Star-forming Regions in the Local Group. I. HST Photometry of Young Populations in Six Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Bianchi, Luciana; Efremova, Boryana; Hodge, Paul; Massey, Philip; Olsen, K. A. G.

    2012-03-01

    We present a comprehensive study of young stellar populations in six dwarf galaxies in or near the Local Group: Phoenix, Pegasus, Sextans A, Sextans B, WLM, and NGC 6822. Their star-forming regions, selected from GALEX wide-field far-UV imaging, were imaged (at sub-pc resolution) with the WFPC2 camera on board the Hubble Space Telescope (HST) in six bandpasses from far-UV to I to detect and characterize their hot massive star content. This study is part of HST treasury survey program HST-GO-11079; the general data characteristics and reduction procedures are detailed in this paper and results are presented for the first six galaxies. From a total of 180 HST images, we provide catalogs of the multi-band stellar photometry and derive the physical parameters of massive stars by analyzing it with model-atmosphere colors. We use the results to infer ages, number of massive stars, extinction, and spatial characteristics of the young stellar populations. The hot massive star content varies largely across our galaxy sample, from an inconspicuous presence in Phoenix and Pegasus to the highest relative abundance of young massive stars in Sextans A and WLM. Albeit to a largely varying extent, most galaxies show a very young population (a few Myrs, except for Phoenix), and older ones (a few 107 years in Sextans A, Sextans B, NGC 6822, and WLM, ~108yr in Phoenix and Pegasus), suggesting discrete bursts of recent star formation in the mapped regions. The hot massive star content (indicative of the young populations) broadly correlates with the total galaxy stellar mass represented by the integrated optical magnitude, although it varies by a factor of ~3 between Sextans A, WLM, and Sextans B, which have similar MV . Extinction properties are also derived.

  6. A TREASURY STUDY OF STAR-FORMING REGIONS IN THE LOCAL GROUP. I. HST PHOTOMETRY OF YOUNG POPULATIONS IN SIX DWARF GALAXIES

    SciTech Connect

    Bianchi, Luciana; Efremova, Boryana; Hodge, Paul; Massey, Philip; Olsen, K. A. G.

    2012-03-15

    We present a comprehensive study of young stellar populations in six dwarf galaxies in or near the Local Group: Phoenix, Pegasus, Sextans A, Sextans B, WLM, and NGC 6822. Their star-forming regions, selected from GALEX wide-field far-UV imaging, were imaged (at sub-pc resolution) with the WFPC2 camera on board the Hubble Space Telescope (HST) in six bandpasses from far-UV to I to detect and characterize their hot massive star content. This study is part of HST treasury survey program HST-GO-11079; the general data characteristics and reduction procedures are detailed in this paper and results are presented for the first six galaxies. From a total of 180 HST images, we provide catalogs of the multi-band stellar photometry and derive the physical parameters of massive stars by analyzing it with model-atmosphere colors. We use the results to infer ages, number of massive stars, extinction, and spatial characteristics of the young stellar populations. The hot massive star content varies largely across our galaxy sample, from an inconspicuous presence in Phoenix and Pegasus to the highest relative abundance of young massive stars in Sextans A and WLM. Albeit to a largely varying extent, most galaxies show a very young population (a few Myrs, except for Phoenix), and older ones (a few 10{sup 7} years in Sextans A, Sextans B, NGC 6822, and WLM, {approx}10{sup 8}yr in Phoenix and Pegasus), suggesting discrete bursts of recent star formation in the mapped regions. The hot massive star content (indicative of the young populations) broadly correlates with the total galaxy stellar mass represented by the integrated optical magnitude, although it varies by a factor of {approx}3 between Sextans A, WLM, and Sextans B, which have similar M{sub V}. Extinction properties are also derived.

  7. Linking dust emission to fundamental properties in galaxies: the low-metallicity picture

    NASA Astrophysics Data System (ADS)

    Rémy-Ruyer, A.; Madden, S. C.; Galliano, F.; Lebouteiller, V.; Baes, M.; Bendo, G. J.; Boselli, A.; Ciesla, L.; Cormier, D.; Cooray, A.; Cortese, L.; De Looze, I.; Doublier-Pritchard, V.; Galametz, M.; Jones, A. P.; Karczewski, O. Ł.; Lu, N.; Spinoglio, L.

    2015-10-01

    Aims: In this work, we aim to provide a consistent analysis of the dust properties from metal-poor to metal-rich environments by linking them to fundamental galactic parameters. Methods: We consider two samples of galaxies: the Dwarf Galaxy Survey (DGS) and the Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH), totalling 109 galaxies, spanning almost 2 dex in metallicity. We collect infrared (IR) to submillimetre (submm) data for both samples and present the complete data set for the DGS sample. We model the observed spectral energy distributions (SED) with a physically-motivated dust model to access the dust properties: dust mass, total-IR luminosity, polycyclic aromatic hydrocarbon (PAH) mass fraction, dust temperature distribution, and dust-to-stellar mass ratio. Results: Using a different SED model (modified black body), different dust composition (amorphous carbon in lieu of graphite), or a different wavelength coverage at submm wavelengths results in differences in the dust mass estimate of a factor two to three, showing that this parameter is subject to non-negligible systematic modelling uncertainties. We find half as much dust with the amorphous carbon dust composition. For eight galaxies in our sample, we find a rather small excess at 500 μm (≤1.5σ). We find that the dust SED of low-metallicity galaxies is broader and peaks at shorter wavelengths compared to more metal-rich systems, a sign of a clumpier medium in dwarf galaxies. The PAH mass fraction and dust temperature distribution are found to be driven mostly by the specific star formation rate, sSFR, with secondary effects from metallicity. The correlations between metallicity and dust mass or total-IR luminosity are direct consequences of the stellar mass-metallicity relation. The dust-to-stellar mass ratios of metal-rich sources follow the well-studied trend of decreasing ratio for decreasing sSFR. The relation is more complex for low-metallicity galaxies with high

  8. Chemical history of isolated dwarf galaxies of the Local Group - I. dSphs: Cetus and Tucana

    NASA Astrophysics Data System (ADS)

    Avila-Vergara, N.; Carigi, L.; Hidalgo, S. L.; Durazo, R.

    2016-04-01

    For the first time, we obtain chemical evolution models (CEMs) for Tucana and Cetus, two isolated dwarf spheroidal galaxies of the Local Group. The CEMs have been built from the star formation histories (SFHs) and the metallicity histories, both obtained independently by the Local Cosmology from Isolated Dwarfs (LCID) project from deep colour-magnitude diagrams. Based on our models, we find that the chemical histories were complex and can be divided into different epochs and scenarios. In particular, during 75 per cent of the SFH, the galaxies behaved as closed boxes and, during the remaining 25 per cent, either received a lot of primordial gas by accretion or they lost metals through metal-rich winds. In order to discriminate between these two scenarios, abundances ratios in old stars are needed. At t ˜ 4.5 Gyr, the galaxies lost most of their gas due to a short-strong, well-mixed wind. We obtain very similar CEMs for both galaxies, although Cetus is twice as massive as Tucana. We conclude that the star formation in both galaxies began with only 1.5 per cent of the baryonic mass fraction predicted by Λ cold dark matter.

  9. Kinematics of local and high-z galaxies through 3D modeling of emission-line datacubes

    NASA Astrophysics Data System (ADS)

    Di Teodoro, Enrico M.

    2015-12-01

    The kinematics is a fundamental tool to infer the dynamical structure of galaxies and to understand their formation and evolution. Spectroscopic observations of gas emission lines are often used to derive rotation curves and velocity dispersions. It is however difficult to disentangle these two quantities in low spatial-resolution data because of beam smearing. In this thesis, we present 3D-Barolo, a new software to derive the gas kinematics of disk galaxies from emission-line data-cubes. The code builds tilted-ring models in the 3D observational space and compares them with the actual data-cubes. 3D-Barolo works with data at a wide range of spatial resolutions without being affected by instrumental biases. We use 3D-Barolo to derive rotation curves and velocity dispersions of several galaxies in both the local and the high-redshift Universe. We run our code on HI observations of nearby galaxies and we compare our results with 2D traditional approaches. We show that a 3D approach to the derivation of the gas kinematics has to be preferred to a 2D approach whenever a galaxy is resolved with less than about 20 elements across the disk. We moreover analyze a sample of galaxies at z~1, observed in the H-alpha line with the KMOS/VLT spectrograph. Our 3D modeling reveals that the kinematics of these high-z systems is comparable to that of local disk galaxies, with steeply-rising rotation curves followed by a flat part and H-alpha velocity dispersions of 15-40 km/s over the whole disks. This evidence suggests that disk galaxies were already fully settled about 7-8 billion years ago. In summary, 3D-Barolo is a powerful and robust tool to separate physical and instrumental effects and to derive a reliable kinematics. The analysis of large samples of galaxies at different redshifts with 3D-Barolo will provide new insights on how galaxies assemble and evolve throughout cosmic time.

  10. PHYSICAL AND MORPHOLOGICAL PROPERTIES OF [O II] EMITTING GALAXIES IN THE HETDEX PILOT SURVEY

    SciTech Connect

    Bridge, Joanna S.; Gronwall, Caryl; Ciardullo, Robin; Hagen, Alex; Zeimann, Greg; Malz, A. I.; Schneider, Donald P. E-mail: caryl@astro.psu.edu E-mail: hagen@psu.edu E-mail: aimalz@psu.edu; and others

    2015-02-01

    The Hobby-Eberly Dark Energy Experiment pilot survey identified 284 [O II] λ3727 emitting galaxies in a 169 arcmin{sup 2} field of sky in the redshift range 0 < z < 0.57. This line flux limited sample provides a bridge between studies in the local universe and higher-redshift [O II] surveys. We present an analysis of the star formation rates (SFRs) of these galaxies as a function of stellar mass as determined via spectral energy distribution fitting. The [O II] emitters fall on the ''main sequence'' of star-forming galaxies with SFR decreasing at lower masses and redshifts. However, the slope of our relation is flatter than that found for most other samples, a result of the metallicity dependence of the [O II] star formation rate indicator. The mass-specific SFR is higher for lower mass objects, supporting the idea that massive galaxies formed more quickly and efficiently than their lower mass counterparts. This is confirmed by the fact that the equivalent widths of the [O II] emission lines trend smaller with larger stellar mass. Examination of the morphologies of the [O II] emitters reveals that their star formation is not a result of mergers, and the galaxies' half-light radii do not indicate evolution of physical sizes.

  11. Analyzing Star Formation Properties in Dusty Early Universe Galaxies Using Gravitational Lensing

    NASA Astrophysics Data System (ADS)

    Bradli, Jaclyn C.; Bussmann, R. Shane; Riechers, Dominik A.; Clements, David; Perez-Fournon, Ismael

    2015-01-01

    Strong gravitational lensing has recently become one of the most important tools for studying star formation properties in extremely high redshift galaxies. Dust-obscured star-forming galaxies found at far-infrared/sub-millimeter wavelengths are important in the assembly of stellar mass and the evolution of massive galaxies. We present Submillimeter Array (SMA) imaging of Lockman 102, a strongly lensed submillimeter galaxy at z=5.29, discovered by the Herschel Space Observatory. The system was observed at 250, 350, 500 and 1000 microns, corresponding to rest frame wavelengths of 40, 56, 80, and 159 microns respectively. The observations were targeted at the thermal dust emission and the [CII] interstellar medium cooling line. We report an estimated photometric redshift of ~1.9 for the lensing galaxy, making it possibly the most distant lens currently known. We use uvmcmcfit, a publicly available Markov Chain Monte Carlo software tool we have developed for interferometric data, to fit lens models to Lockman 102. The results obtained from uvmcmcfit suggest the lensed system is composed of a single lensing galaxy and two extended sources. We have strong constraints on an intrinsic flux density of Lockman 102 of 4.55 + 0.45 mJy magnified by a factor of 12.5 + 1.2. From a modified blackbody fit we compute an intrinsic far infrared luminosity of 5.5e12 L⊙.This implies a star formation rate of ~950 M⊙ yr-1, making Lockman 102 an extremely active dusty galaxy. We also compare Lockman 102 to other dusty luminous starburst galaxies at similar redshift, HLS0918 (Rawle et al. 2014) and AzTEC-3 (Riechers et al. 2014a) and determine it is among the most luminous and active galaxies ~1 Gyr after the Big Bang. It is only with strong lensing that the SMA is able to undertake such a detailed study of a galaxy at this distance; the continued improvements from new facilities such as ALMA offer a promising future in observing even more distant lensed systems.

  12. The MUSIC of Galaxy Clusters - III. Properties, evolution and Y-M scaling relation of protoclusters of galaxies

    NASA Astrophysics Data System (ADS)

    Sembolini, Federico; De Petris, Marco; Yepes, Gustavo; Foschi, Emma; Lamagna, Luca; Gottlöber, Stefan

    2014-06-01

    In this work, we study the properties of protoclusters of galaxies by employing the MultiDark SImulations of galaxy Clusters (MUSIC) set of hydrodynamical simulations, featuring a sample of 282 resimulated clusters with available merger trees up to z = 4. We study the characteristics and redshift evolution of the mass and the spatial distribution for all the protoclusters, which we define as the most massive progenitors of the clusters identified at z = 0. We extend the study of the baryon content to redshifts larger than 1 also in terms of gas and stars budgets: no remarkable variations with redshift are discovered. Furthermore, motivated by the proven potential of Sunyaev-Zel'dovich surveys to blindly search for faint distant objects, we compute the scaling relation between total object mass and integrated Compton y-parameter. We find that the slope of this scaling law is steeper than what expected for a self-similarity assumption among these objects, and it increases with redshift mainly when radiative processes are included. We use three different criteria to account for the dynamical state of the protoclusters, and find no significant dependence of the scaling parameters on the level of relaxation. We exclude the dynamical state as the cause of the observed deviations from self-similarity in protoclusters.

  13. The Grism Lens-Amplified Survey from Space (GLASS). VIII. The Influence of the Cluster Properties on Hα Emitter Galaxies at 0.3 < z < 0.7

    NASA Astrophysics Data System (ADS)

    Vulcani, Benedetta; Treu, Tommaso; Nipoti, Carlo; Schmidt, Kasper B.; Dressler, Alan; Morshita, Takahiro; Poggianti, Bianca M.; Malkan, Matthew; Hoag, Austin; Bradač, Marusa; Abramson, Louis; Trenti, Michele; Pentericci, Laura; von der Linden, Anja; Morris, Glenn; Wang, Xin

    2017-03-01

    Exploiting the data of the Grism Lens-Amplified Survey from Space (GLASS), we characterize the spatial distribution of star formation in 76 highly active star-forming galaxies in 10 clusters at 0.3< z< 0.7. All of these galaxies are likely restricted to first infall. In a companion paper, we contrast the properties of field and cluster galaxies, whereas here we correlate the properties of Hα emitters to a number of tracers of the cluster environment to investigate its role in driving galaxy transformations. Hα emitters are found in the clusters out to 0.5 virial radii, the maximum radius covered by GLASS. The peak of the Hα emission is offset with respect to the peak of the UV continuum. We decompose these offsets into a radial and a tangential component. The radial component points away from the cluster center in 60% of the cases, with 95% confidence. The decompositions agree with cosmological simulations; that is, the Hα emission offset correlates with galaxy velocity and ram-pressure stripping signatures. Trends between Hα emitter properties and surface mass density distributions and X-ray emissions emerge only for unrelaxed clusters. The lack of strong correlations with the global environment does not allow us to identify a unique environmental effect originating from the cluster center. In contrast, correlations between Hα morphology and local number density emerge. We conclude that local effects, uncorrelated to the cluster-centric radius, play a more important role in shaping galaxy properties.

  14. Statistics and properties of H II regions in a sample of grand-design galaxies. II. Physical properties.

    NASA Astrophysics Data System (ADS)

    Rozas, M.; Knapen, J. H.; Beckman, J. E.

    1996-08-01

    We describe statistical properties of complete samples of HII regions in the grand-design spiral galaxies NGC 157, NGC 3631, NGC 6764 and NGC 6951. We use the catalogues of HII regions obtained from high-quality Hα line images by Rozas et al. . Slopes and zero points of diameter distribution functions for these four galaxies coincide well with values published for other galaxies of similar morphological type. We also present density distributions and Hα scale lengths, as well as luminosity-volume and number-luminosity-size relations. The latter relations show evidence for the presence of a population of high luminosity density-bounded HII regions in the spiral arms. We see the change from ionization- to density-bounded HII regions occur clearly at a specific HII region flux level.

  15. Kinematic properties and dark matter fraction of Virgo dwarf early-type galaxies

    NASA Astrophysics Data System (ADS)

    Toloba, E.; Boselli, A.; Peletier, R.; Gorgas, J.

    2015-03-01

    What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity (Fig. 1). These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older (Fig. 1). Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and the spiral/disky structures of these galaxies. We find that on the the Faber-Jackson and the Fundamental Plane relations dEs deviate from the trends of massive elliptical galaxies towards the position of dark matter dominated systems such as the dwarf spheroidal satellites of the Milky Way and M31. Both, rotationally and pressure supported dEs, however, populate the same region in these diagrams. This indicates that dEs have a non-negligible dark matter fraction within their half light radius.

  16. Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Norberg, P.; Robotham, A. S. G.; Liske, J.; Andrae, E.; Baldry, I. K.; Gunawardhana, M.; Kelvin, L. S.; Madore, B. F.; Seibert, M.; Taylor, E. N.; Alpaslan, M.; Brown, M. J. I.; Cluver, M. E.; Driver, S. P.; Bland-Hawthorn, J.; Holwerda, B. W.; Hopkins, A. M.; Lopez-Sanchez, A. R.; Loveday, J.; Rushton, M.

    2017-03-01

    We quantify the effect of the galaxy group environment (for group masses of 1012.5–1014.0 M ⊙) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (i.e., late-type spiral) galaxies with redshift ≤0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M * ≥ 109.5 M ⊙. We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy–galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M * is controlled for by measuring offsets Δlog(ψ *) of grouped galaxies about a single power-law relation in specific SFR, {\\psi }* \\propto {M}* -0.45+/- 0.01, exhibited by non-grouped “field” galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of ψ * statistically indistinguishable from their field counterparts, for all M *, albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Δlog(ψ *), we find that (i) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of ∼1.5–5 x SFR and ∼1–4 x SFR, respectively; and (ii) the independence of the continuity of these gas flow cycles on M * appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of ∼100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on ∼Mpc scales, i.e., from gas not initially associated with the galaxies upon infall. Consequently

  17. Variable stars in Local Group Galaxies - II. Sculptor dSph

    NASA Astrophysics Data System (ADS)

    Martínez-Vázquez, C. E.; Stetson, P. B.; Monelli, M.; Bernard, E. J.; Fiorentino, G.; Gallart, C.; Bono, G.; Cassisi, S.; Dall'Ora, M.; Ferraro, I.; Iannicola, G.; Walker, A. R.

    2016-11-01

    We present the identification of 634 variable stars in the Milky Way dwarf spheroidal (dSph) satellite Sculptor based on archival ground-based optical observations spanning ˜24 yr and covering ˜2.5 deg2. We employed the same methodologies as the `Homogeneous Photometry' series published by Stetson. In particular, we have identified and characterized one of the largest (536) RR Lyrae samples so far in a Milky Way dSph satellite. We have also detected four Anomalous Cepheids, 23 SX Phoenicis stars, five eclipsing binaries, three field variable stars, three peculiar variable stars located above the horizontal branch - near to the locus of BL Herculis - that we are unable to classify properly. Additionally, we identify 37 long period variables plus 23 probable variable stars, for which the current data do not allow us to determine the period. We report positions and finding charts for all the variable stars, and basic properties (period, amplitude, mean magnitude) and light curves for 574 of them. We discuss the properties of the RR Lyrae stars in the Bailey diagram, which supports the coexistence of subpopulations with different chemical compositions. We estimate the mean mass of Anomalous Cepheids (˜1.5 M⊙) and SX Phoenicis stars (˜1 M⊙). We discuss in detail the nature of the former. The connections between the properties of the different families of variable stars are discussed in the context of the star formation history of the Sculptor dSph galaxy.

  18. Radio continuum properties of luminous infrared galaxies. Identifying the presence of an AGN in the radio

    NASA Astrophysics Data System (ADS)

    Vardoulaki, E.; Charmandaris, V.; Murphy, E. J.; Diaz-Santos, T.; Armus, L.; Evans, A. S.; Mazzarella, J. M.; Privon, G. C.; Stierwalt, S.; Barcos-Muñoz, L.

    2015-02-01

    Context. Luminous infrared galaxies (LIRGs) are systems enshrouded in dust, which absorbs most of their optical/UV emission and radiates it again in the mid- and far-infrared. Radio observations are largely unaffected by dust obscuration, enabling us to study the central regions of LIRGs in an unbiased manner. Aims: The main goal of this project is to examine how the radio properties of local LIRGs relate to their infrared spectral characteristics. Here we present an analysis of the radio continuum properties of a subset of the Great Observatories All-sky LIRG Survey (GOALS), which consists of 202 nearby systems (z< 0.088). Our radio sample consists of 35 systems, containing 46 individual galaxies, that were observed at both 1.49 and 8.44 GHz with the VLA with a resolution of about 1 arcsec (FWHM). The aim of the project is to use the radio imagery to probe the central kpc of these LIRGs in search of active galactic nuclei (AGN). Methods: We used the archival data at 1.49 and 8.44 GHz to create radio-spectral-index maps using the standard relation between flux density Sν and frequency ν, Sν ~ ν- α, where α is the radio spectral index. By studying the spatial variations in α, we classified the objects as radio-AGN, radio-SB, and AGN/SB (a mixture). We identified the presence of an active nucleus using the radio morphology, deviations from the radio/infrared correlation, and spatially resolved spectral index maps, and then correlated this to the usual mid-infrared ([NeV]/[NeII] and [OIV]/[NeII] line ratios and equivalent width of the 6.2 μm PAH feature) and optical (BPT diagram) AGN diagnostics. Results: We find that 21 out of the 46 objects in our sample (~45%) are radio-AGN, 9 out of the 46 (~20%) are classified as starbursts (SB) based on the radio analysis, and 16 (~35%) are AGN/SB. After comparing to other AGN diagnostics we find 3 objects out of the 46 (~7%) that are identified as AGN based on the radio analysis, but are not classified as such based on

  19. The Milky Way Bulge: Observed Properties and a Comparison to External Galaxies

    NASA Astrophysics Data System (ADS)

    Gonzalez, Oscar A.; Gadotti, Dimitri

    The Milky Way bulge offers a unique opportunity to investigate in detail the role that different processes such as dynamical instabilities, hierarchical merging, and dissipational collapse may have played in the history of the Galaxy formation and evolution based on its resolved stellar population properties. Large observation programs and surveys of the bulge are providing for the first time a look into the global view of the Milky Way bulge that can be compared with the bulges of other galaxies, and be used as a template for detailed comparison with models. The Milky Way has been shown to have a boxy/peanut (B/P) bulge and recent evidence seems to suggest the presence of an additional spheroidal component. In this review we summarize the global chemical abundances, kinematics and structural properties that allow us to disentangle these multiple components and provide constraints to understand their origin. The investigation of both detailed and global properties of the bulge now provide us with the opportunity to characterize the bulge as observed in models, and to place the mixed component bulge scenario in the general context of external galaxies. When writing this review, we considered the perspectives of researchers working with the Milky Way and researchers working with external galaxies. It is an attempt to approach both communities for a fruitful exchange of ideas.

  20. Spectroscopic Properties of Selected Narrow Emission Line Galaxies from the COSMOS Field

    NASA Astrophysics Data System (ADS)

    Colon, Amy M.; Carroll, P.; Roberts, R.; Wong, N.; Liu, C.

    2007-12-01

    We present properties of seven blue narrow emission line galaxies (NELGs) in the redshift range 0.25 < z < 0.73, initially selected as QSO candidates in the COSMOS 2-degree survey field. These galaxies have been selected for the high signal-to-noise of their spectra, as indicated by the presence of the emission line [NeIII] 3869 Angstroms. Emission line diagnostics are used to measure metallicities and star formation rates, and to test the presence of AGN. Hubble ACS images are used to measure their surface brightness distributions and quantitative morphologies. Preliminary results indicate that these objects are forming stars at a rate of 4 to 20 solar masses per year; and their metallicity appears not to vary with the galaxy's concentration index which ranges 0.42 to 0.63.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  2. Core-collapse supernova progenitor constraints using the spatial distributions of massive stars in local galaxies

    NASA Astrophysics Data System (ADS)

    Kangas, T.; Portinari, L.; Mattila, S.; Fraser, M.; Kankare, E.; Izzard, R. G.; James, P.; González-Fernández, C.; Maund, J. R.; Thompson, A.

    2017-01-01

    We studied the spatial correlations between the Hα emission and different types of massive stars in two local galaxies, the Large Magellanic Cloud (LMC) and Messier 33. We compared these to correlations derived for core-collapse supernovae (CCSNe) in the literature to connect CCSNe of different types with the initial masses of their progenitors and to test the validity of progenitor mass estimates which use the pixel statistics method. We obtained samples of evolved massive stars in both galaxies from catalogues with good spatial coverage and/or completeness, and combined them with coordinates of main-sequence stars in the LMC from the SIMBAD database. We calculated the spatial correlation of stars of different classes and spectral types with Hα emission. We also investigated the effects of distance, noise and positional errors on the pixel statistics method. A higher correlation with Hα emission is found to correspond to a shorter stellar lifespan, and we conclude that the method can be used as an indicator of the ages, and therefore initial masses, of SN progenitors. We find that the spatial distributions of type II-P SNe and red supergiants of appropriate initial mass (≳9 M⊙) are consistent with each other. We also find the distributions of type Ic SNe and WN stars with initial masses ≳20 M⊙ consistent, while supergiants with initial masses around 15 M⊙ are a better match for type IIb and II-L SNe. The type Ib distribution corresponds to the same stellar types as type II-P, which suggests an origin in interacting binaries. On the other hand, we find that luminous blue variable stars show a much stronger correlation with Hα emission than do type IIn SNe.

  3. Evolved stars in the Local Group galaxies - I. AGB evolution and dust production in IC 1613

    NASA Astrophysics Data System (ADS)

    Dell'Agli, F.; Di Criscienzo, M.; Boyer, M. L.; García-Hernández, D. A.

    2016-08-01

    We used models of thermally pulsing asymptotic giant branch (AGB) stars, which also describe the dust-formation process in the wind, to interpret the combination of near- and mid-infrared photometric data of the dwarf galaxy IC 1613. This is the first time that this approach is extended to an environment different from the Milky Way and the Magellanic Clouds (MCs). Our analysis, based on synthetic population techniques, shows nice agreement between the observations and the expected distribution of stars in the colour-magnitude diagrams obtained with JHK and Spitzer bands. This allows a characterization of the individual stars in the AGB sample in terms of mass, chemical composition and formation epoch of the progenitors. We identify the stars exhibiting the largest degree of obscuration as carbon stars evolving through the final AGB phases, descending from 1-1.25 M⊙ objects of metallicity Z = 10-3 and from 1.5-2.5 M⊙ stars with Z = 2 × 10-3. Oxygen-rich stars constitute the majority of the sample (˜65 per cent), mainly low-mass stars (<2 M⊙) that produce a negligible amount of dust (≤10-7 M⊙ yr-1). We predict the overall dust-production rate from IC 1613, mostly determined by carbon stars, to be ˜6 × 10-7 M⊙ yr-1 with an uncertainty of 30 per cent. The capability of the current generation of models to interpret the AGB population in an environment different from the MCs opens the possibility to extend this kind of analysis to other Local Group galaxies.

  4. Red Supergiants in the Inner Galaxy: Stellar Properties

    NASA Astrophysics Data System (ADS)

    Messineo, Maria; Zhu, Qingfeng; Menten, Karl M.; Ivanov, Valentin D.; Figer, Donald F.; Kudritzki, Rolf-Peter; Chen, C.-H. Rosie

    2017-02-01

    Red supergiants (RSGs) are luminous cool stars detectable in disks of distant spirals. About a thousand are known in the Galaxy. Here, we analyze a sample of late-type stars recently observed by Messineo et al. in the inner Galaxy (10^\\circ < l< 60^\\circ ). A total of 58 targets (25% of previously known RSGs) were reported as supergiants based on their large equivalent widths of the CO band-head at 2.293 μm (EWs > 45 Å, ≳M0I). In this work, luminosities are estimated with infrared measurements and distance moduli for 47 spectroscopically classified RSGs; they range from 3.2× {10}4 to 1.3× {10}5 {L}ȯ . Six other RSGs with smaller EW(CO)s are classified according to their luminosities. Using a prescription based on {K}{{s}}{--}[W4], moderate mass-loss rates from 10‑8 to {10}-6.5 {M}ȯ yr‑1 are inferred. In addition, we report on H and K spectra of 26 stars at R = 1500–2200. EWs of the CO at 2.293 and 1.620 μm, and of atomic lines, are consistent with those of nearby RSGs, within uncertainties. Mg i appears to be a useful diagnostic to confirm RSGs at R = 1500–2200. RSG #66 is a member of the cluster Alicante 7. Star #92 is projected onto the overdensity #495 of Camargo et al., but our analysis suggests they are unrelated. Remaining targets are isolated from other known RSGs within ≈3‧.

  5. Low Surface Brightness Galaxies Selected from the 40% Sky Area of the ALFALFA H I Survey. I. Sample and Statistical Properties

    NASA Astrophysics Data System (ADS)

    Du, Wei; Wu, Hong; Lam, Man I.; Zhu, Yinan; Lei, Fengjie; Zhou, Zhimin

    2015-06-01

    The population of low surface brightness (LSB) galaxies, which are objects with central surface brightnesses at least one magnitude fainter than the night sky, is crucial for understanding the extremes of galactic formation and evolution of the universe. As LSB galaxies are mostly rich in gas (H i), the α.40 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) sample is one of the best survey combinations to select a sample of them in the local universe. Since the sky backgrounds are systematically overestimated for galactic images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended LSB outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images accurately in both the g and r bands for each galaxy in the α.40 SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture using the SExtractor software and fitted geometric parameters with an exponential profile model using the Galfit software for each galactic image in the α.40 SDSS DR7 sample. Based on the photometric and geometric results, we further calculated the B-band central surface brightness, {{μ }0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with {{μ }0}(B) > 22.5 mag arcsec-2 and the axis ratio b/a > 0.3 from the 12,423 α.40 SDSS DR7 galaxies. This H i-selected sample of LSB galaxies is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in H i observation and the optical magnitude within the limit of the SDSS DR7 photometric survey. This LSB galactic sample spans from 22.5 to 28.3 in {{μ }0}(B) with a fraction of 4% fainter than 25.0 mag arcsec-2 in B-band central surface brightness and distributes from -27.0 to -12.3 mag in absolute magnitude in the B band (M(B)), including the 43 faintest galaxies (M(B) > -17.3 mag). This sample is a blue LSB

  6. The Dependence of Cluster Galaxy Properties on the Central Entropy of their Host Cluster

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Woo; Ko, Jongwan; Hwang, Ho Seong; Edge, Alastair C.; Lee, Joon Hyeop; Lee, Jong Chul; Jeong, Hyunjin

    2017-02-01

    We present a study of the connection between brightest cluster galaxies (BCGs) and their host galaxy clusters. Using galaxy clusters at 0.1< z< 0.3 from the Hectospec Cluster Survey (HeCS) with X-ray information from the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT), we confirm that BCGs in low central entropy clusters are well aligned with the X-ray center. Additionally, the magnitude difference between BCG and the second brightest galaxy also correlates with the central entropy of the intracluster medium. From the red-sequence (RS) galaxies, we cannot find significant dependence of RS color scatter and stellar population on the central entropy of the intracluster medium of their host cluster. However, BCGs in low-entropy clusters are systematically less massive than those in high-entropy clusters, although this is dependent on the method used to derive the stellar mass of BCGs. In contrast, the stellar velocity dispersion of BCGs shows no dependence on BCG activity and cluster central entropy. This implies that the potential of the BCG is established earlier and the activity leading to optical emission lines is dictated by the properties of the intracluster medium in the cluster core.

  7. Clustering properties of g-selected galaxies at z ˜ 0.8

    NASA Astrophysics Data System (ADS)

    Favole, Ginevra; Comparat, Johan; Prada, Francisco; Yepes, Gustavo; Jullo, Eric; Niemiec, Anna; Kneib, Jean-Paul; Rodríguez-Torres, Sergio A.; Klypin, Anatoly; Skibba, Ramin A.; McBride, Cameron K.; Eisenstein, Daniel J.; Schlegel, David J.; Nuza, Sebastián E.; Chuang, Chia-Hsun; Delubac, Timothée; Yèche, Christophe; Schneider, Donald P.

    2016-10-01

    Current and future large redshift surveys, as the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) or the Dark Energy Spectroscopic Instrument (DESI), will use emission-line galaxies (ELGs) to probe cosmological models by mapping the large-scale structure of the Universe in the redshift range 0.6 < z < 1.7. With current data, we explore the halo-galaxy connection by measuring three clustering properties of g-selected ELGs as matter tracers in the redshift range 0.6 < z < 1: (i) the redshift-space two-point correlation function using spectroscopic redshifts from the BOSS ELG sample and VIPERS; (ii) the angular two-point correlation function on the footprint of the CFHT-LS; (iii) the galaxy-galaxy lensing signal around the ELGs using the CFHTLenS. We interpret these observations by mapping them on to the latest high-resolution MultiDark Planck N-body simulation, using a novel (Sub)Halo-Abundance Matching technique that accounts for the ELG incompleteness. ELGs at z ˜ 0.8 live in haloes of (1 ± 0.5) × 1012 h-1M⊙ and 22.5 ± 2.5 per cent of them are satellites belonging to a larger halo. The halo occupation distribution of ELGs indicates that we are sampling the galaxies in which stars form in the most efficient way, according to their stellar-to-halo mass ratio.

  8. Building disc structure and galaxy properties through angular momentum: the DARK SAGE semi-analytic model

    NASA Astrophysics Data System (ADS)

    Stevens, Adam R. H.; Croton, Darren J.; Mutch, Simon J.

    2016-09-01

    We present the new semi-analytic model of galaxy evolution, DARK SAGE, a heavily modified version of the publicly available SAGE code. The model is designed for detailed evolution of galactic discs. We evolve discs in a series of annuli with fixed specific angular momentum, which allows us to make predictions for the radial and angular-momentum structure of galaxies. Most physical processes, including all channels of star formation and associated feedback, are performed in these annuli. We present the surface density profiles of our model spiral galaxies, both as a function of radius and specific angular momentum, and find that the discs naturally build a pseudo-bulge-like component. Our main results are focused on predictions relating to the integrated mass-specific angular momentum relation of stellar discs. The model produces a distinct sequence between these properties in remarkable agreement with recent observational literature. We investigate the impact Toomre disc instabilities have on shaping this sequence and find they are crucial for regulating both the mass and spin of discs. Without instabilities, high-mass discs would be systematically deficient in specific angular momentum by a factor of ˜2.5, with increased scatter. Instabilities also appear to drive the direction in which the mass-spin sequence of spiral galaxy discs evolves. With them, we find galaxies of fixed mass have higher specific angular momentum at later epochs.

  9. Global-, local-, and intermediate-scale structures in prototype spiral galaxies

    NASA Technical Reports Server (NTRS)

    Roberts, William W., Jr.

    1993-01-01

    The relationship between galactic spiral structure and the matter in the underlying disk constitutes one of the central problems in galactic dynamics. In Bertin et al. (1989), disk matter characterized by a low-dispersive speed is shown to be capable of playing a key role in the generation of large-scale spiral structure. In Roberts et al. (1992), this self-gravitating, low-dispersion disk matter is shown to be capable of playing an essential role in the formation of structure on local and intermediate scales. Both in computed cases where large-scale spiral structure is present and in those where it is not, the same dominant physical processes and fundamental dynamical mechanisms are active on local scales. The new perception, in which large-scale and small-scale phenomena operate somewhat independently as evidenced in the computational studies, permits a range of flocculent, multiarmed, and grand design spiral types to be simulated. In particular, grand design galaxies with ragged appearances exhibiting spurs, arm branchings, and interarm bridges in addition to the major spiral arms, similar to those often observed, can be generated.

  10. The Properties of Intracluster Light and the Halos of cD Galaxies

    NASA Astrophysics Data System (ADS)

    Feldmeier, John; Mihos, Chris; Morrison, Heather; Harding, Paul

    2002-02-01

    We propose deep imaging to continue our study of the intracluster light (ICL) and extended halos of cD galaxies in galaxy clusters as a function of cluster environment. The ICL is likely formed both from violent relaxation during cluster formation and from subsequent tidal stripping of cluster galaxies, so that its properties should be linked to the dynamical evolution of the cluster and to the distribution of dark matter in cluster galaxies. The structure of the ICL, therefore, should vary between clusters with different physical properties. Furthermore, the structure of cD halos - the deviation from or adherence to a pure R^1/4 law - may indicate whether these structures are formed predominantly during early cluster collapse or later infall and tidal stripping. To extend our studies, we will target six rich Abell clusters which span a range of Bautz-Morgan type, from cD- dominated type I clusters to type III clusters where the galaxy population is more uniform. In addition, we also plan to observe several MKW/AWM poor clusters to see how the properties of ICL vary as a function of cluster richness. This sample will allows us to probe how the properties of the ICL and cD halos vary over a range of cluster environments. We are requesting 7 dark nights on the 2.1m to reach (mu)_V=26.5 mag/sq arcsec in each cluster. This proposal received an average score of 8.40 last period but it was rejected due to scheduling constraints. We are therefore re- proposing for it this period.

  11. Insights into the content and spatial distribution of dust from the integrated spectral properties of galaxies

    NASA Astrophysics Data System (ADS)

    Chevallard, J.; Charlot, S.; Wandelt, B.; Wild, V.

    2013-07-01

    We present a new approach to investigate the content and spatial distribution of dust in structurally unresolved star-forming galaxies from the observed dependence of integrated spectral properties on galaxy inclination. Motivated by the observation that different stellar populations reside in different spatial components of nearby star-forming galaxies, we develop an innovative combination of generic models of radiative transfer in dusty media with a prescription for the spectral evolution of galaxies, via the association of different geometric components of galaxies with stars in different age ranges. We start by showing that a wide range of radiative transfer models all predict a quasi-universal relation between slope of the attenuation curve at any wavelength, from the ultraviolet to the near-infrared, and V-band attenuation optical depth in the diffuse interstellar medium (ISM), at all galaxy inclinations. This relation predicts steeper (shallower) dust attenuation curves than both the Calzetti and Milky Way curves at small (large) attenuation optical depths, which implies that geometry and orientation effects have a stronger influence on the shape of the attenuation curve than changes in the optical properties of dust grains. We use our new, combined radiative transfer and spectral evolution model to interpret the observed dependence of the Hα/Hβ ratio and ugrizYJH attenuation curve on inclination in a sample of about 23 000 nearby star-forming galaxies, which we correct for systematic biases by developing a general method based on importance sampling. From the exploration of the model parameter space by means of a Bayesian Markov chain Monte Carlo technique, we measure the central face-on B-band optical depth of this sample to be τB⊥ ≈ 1.8 ± 0.2 (corresponding to an angle-averaged {< hat{τ}^ISM_V> _θ }≈ 0.3). We also quantify the enhanced optical depth towards newly formed stars in their birth clouds, finding this to be significantly larger in

  12. THE INFLUENCE OF RED SPIRAL GALAXIES ON THE SHAPE OF THE LOCAL K-BAND LUMINOSITY FUNCTION

    SciTech Connect

    Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath; Pimbblet, Kevin A.

    2015-02-01

    We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K {sub tot} ≤ 10.75). Our sample is drawn from the Two Micron All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find that red spirals comprise 20%-50% of all spirals with –25 ≤ M{sub K}  < –20. Fainter than M{sub K} = –24, red spirals are as common as early types, explaining the different faint end slopes (α = –0.87 and –1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all M{sub K}  < –25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sérsic indices consistent with faded disks, rather than true bulge-dominated galaxies.

  13. The clustering properties of radio-selected AGN and star-forming galaxies up to redshifts z ˜ 3

    NASA Astrophysics Data System (ADS)

    Magliocchetti, M.; Popesso, P.; Brusa, M.; Salvato, M.; Laigle, C.; McCracken, H. J.; Ilbert, O.

    2017-01-01

    We present the clustering properties of a complete sample of 968 radio sources detected at 1.4 GHz by the Very Large Array (VLA)-COSMOS survey with radio fluxes brighter than 0.15 mJy. 92 per cent have redshift determinations from the Laigle et al. catalogue. Based on their radio luminosity, these objects have been divided into 644 AGN and 247 star-forming galaxies. By fixing the slope of the autocorrelation function to γ = 2, we find r_0=11.7^{+1.0}_{-1.1} Mpc for the clustering length of the whole sample, while r_0=11.2^{+2.5}_{-3.3} Mpc and r_0=7.8^{+1.6}_{-2.1} Mpc (r_0=6.8^{+1.4}_{-1.8} Mpc for z ≤ 0.9) are, respectively, obtained for AGN and star-forming galaxies. These values correspond to minimum masses for dark matter haloes of M_min=10^{13.6^{+0.3}_{-0.6}} M⊙ for radio-selected AGN and M_min=10^{13.1^{+0.4}_{-1.6}} M⊙ for radio-emitting star-forming galaxies (M_min=10^{12.7^{+0.7}_{-2.2}} M⊙ for z ≤ 0.9). Comparisons with previous works imply an independence of the clustering properties of the AGN population with respect to both radio luminosity and redshift. We also investigate the relationship between dark and luminous matter in both populations. We obtain /Mhalo ≲ 10- 2.7 for AGN, and /Mhalo ≲ 10- 2.4 in the case of star-forming galaxies. Furthermore, if we restrict to z ≲ 0.9 star-forming galaxies, we derive /Mhalo ≲ 10- 2.1, result that clearly shows the cosmic process of stellar build-up as one moves towards the more local universe. Comparisons between the observed space density of radio-selected AGN and that of dark matter haloes show that about one in two haloes is associated with a black hole in its radio-active phase. This suggests that the radio-active phase is a recurrent phenomenon.

  14. Broad-band colours and overall photometric properties of template galaxy models from stellar population synthesis

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto

    2005-08-01

    We present here a new set of evolutionary population synthesis models for template galaxies along the Hubble morphological sequence. The models, which account for the individual evolution of the bulge, disc, and halo components, provide basic morphological features, along with bolometric luminosity and colour evolution (including Johnson/Cousins, Gunn g, r, i, and Washington C, M, T1, T2 photometric systems) between 1 and 15 Gyr. The luminosity contribution from residual gas is also evaluated, both in terms of nebular continuum and Balmer-line enhancement. Our theoretical framework relies on the observed colours of present-day galaxies, coupled with a minimal set of physical assumptions related to simple stellar population (SSP) evolution theory, to constrain the overall distinctive properties of galaxies at earlier epochs. A comparison with more elaborate photometric models, and with empirical sets of reference spectral energy distributions (SEDs) for early- and late-type galaxies is accomplished, in order to test output reliability and investigate the internal uncertainty of the models. The match with observed colours of present-day galaxies tightly constrain the stellar birth rate, b, which smoothly increases from E to Im types. The comparison with the observed supernova (SN) rate in low-redshift galaxies shows, as well, a pretty good agreement, and allows us to tune up the inferred star formation activity and the SN and hypernova rates among the different galaxy morphological types. Among others, these results could find useful application also in cosmological studies, given for instance the claimed relationship between hypernova events and gamma-ray bursts. One outstanding feature of the back-in-time evolution model is the prevailing luminosity contribution of the bulge at early epochs. As a consequence, the current morphological look of galaxies might drastically change when moving to larger distances, and we discuss here how sensibly this bias could affect

  15. Molecular and atomic gas in the Local Group galaxy M 33

    NASA Astrophysics Data System (ADS)

    Gratier, P.; Braine, J.; Rodriguez-Fernandez, N. J.; Schuster, K. F.; Kramer, C.; Xilouris, E. M.; Tabatabaei, F. S.; Henkel, C.; Corbelli, E.; Israel, F.; van der Werf, P. P.; Calzetti, D.; Garcia-Burillo, S.; Sievers, A.; Combes, F.; Wiklind, T.; Brouillet, N.; Herpin, F.; Bontemps, S.; Aalto, S.; Koribalski, B.; van der Tak, F.; Wiedner, M. C.; Röllig, M.; Mookerjea, B.

    2010-11-01

    We present high-resolution large-scale observations of the molecular and atomic gas in the Local Group galaxy M 33. The observations were carried out using the HEterodyne Receiver Array (HERA) at the 30 m IRAM telescope in the CO(2-1) line, achieving a resolution of 12” × 2.6 km s-1, enabling individual giant molecular clouds (GMCs) to be resolved. The observed region is 650 square arcminutes mainly along the major axis and out to a radius of 8.5 kpc, and covers entirely the 2' × 40' radial strip observed with the HIFI and PACS Spectrometers as part of the HERM33ES Herschel key program. The achieved sensitivity in main-beam temperature is 20-50 mK at 2.6 km s-1 velocity resolution. The CO(2-1) luminosity of the observed region is 1.7±0.1 × 107 K km s-1 pc2 and is estimated to be 2.8±0.3 × 107 K km s-1 pc2 for the entire galaxy, corresponding to H2 masses of 1.9 × 108 Msun and 3.3 × 108 Msun respectively (including He), calculated with N(H2)/ICO(1-0) twice the Galactic value due to the half-solar metallicity of M 33. The H i 21 cm VLA archive observations were reduced, and the mosaic was imaged and cleaned using the multi-scale task in the CASA software package, yielding a series of datacubes with resolutions ranging from 5” to 25”. The H i mass within a radius of 8.5 kpc is estimated to be 1.4 × 109 Msun. The azimuthally averaged CO surface brightness decreases exponentially with a scale length of 1.9±0.1 kpc whereas the atomic gas surface density is constant at ΣH I = 6±2 Msun pc-2 deprojected to face-on. For an N(H2)/ICO(1-0) conversion factor twice that of the Milky Way, the central kiloparsec H2 surface density is ΣH2 = 8.5±0.2 Msun pc-2. The star formation rate per unit molecular gas (SF efficiency, the rate of transformation of molecular gas into stars), as traced by the ratio of CO to Hα and FIR brightness, is constant with radius. The SFE, with a N(H2)/ICO(1-0) factor twice galactic, appears 2-4 times greater than for large spiral

  16. Major-Merger Galaxy Pairs at Z = 0: Dust Properties and Companion Morphology

    NASA Astrophysics Data System (ADS)

    Domingue, Donovan L.; Cao, Chen; Xu, C. Kevin; Jarrett, Thomas H.; Ronca, Joseph; Hill, Emily; Jacques, Allison

    2016-10-01

    We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K s magnitude and redshift. The pairs represent the two populations of spiral-spiral (S+S) and mixed morphology spiral-elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer, and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not have the same level of enhancement of star formation and differ in dust composition. The spirals of mixed-morphology galaxy pairs do not exhibit the enhancements in interstellar radiation field and therefore dust temperature for spirals in S+S pairs in contrast to what would be expected according to standard models of gas redistribution due to encounter torques. This suggests the importance of the companion environment/morphology in determining the dust properties of a spiral galaxy in a close major-merger pair.

  17. THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES

    SciTech Connect

    Saintonge, Amelie; Fabello, Silvia; Wang Jing; Catinella, Barbara; Tacconi, Linda J.; Genzel, Reinhard; Gracia-Carpio, Javier; Wuyts, Stijn; Kramer, Carsten; Moran, Sean; Heckman, Timothy M.; Schiminovich, David; Schuster, Karl

    2012-10-20

    Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H{sub 2} mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M {sub *} plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies ({mu}{sub *} >5 Multiplication-Sign 10{sup 8} M {sub Sun} kpc{sup -2}, C > 2.6) that are either gas-poor (M{sub H{sub 2}}/M {sub *} <1.5%) or else on average less efficient by a factor of {approx}2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g., HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO

  18. The Herschel Virgo Cluster Survey - XII. FIR properties of optically selected Virgo cluster galaxies

    NASA Astrophysics Data System (ADS)

    Auld, R.; Bianchi, S.; Smith, M. W. L.; Davies, J. I.; Bendo, G. J.; di Serego, S. Alighieri; Cortese, L.; Baes, M.; Bomans, D. J.; Boquien, M.; Boselli, A.; Ciesla, L.; Clemens, M.; Corbelli, E.; De Looze, I.; Fritz, J.; Gavazzi, G.; Pappalardo, C.; Grossi, M.; Hunt, L. K.; Madden, S.; Magrini, L.; Pohlen, M.; Verstappen, J.; Vlahakis, C.; Xilouris, E. M.; Zibetti, S.

    2013-01-01

    The Herschel Virgo Cluster Survey (HeViCS) is the deepest, confusion-limited survey of the Virgo Cluster at far-infrared (FIR) wavelengths. The entire survey at full depth covers ˜55 deg2 in five bands (100-500 μm), encompassing the areas around the central dominant elliptical galaxies (M87, M86 and M49) and extends as far as the NW cloud, the W cloud and the Southern extension. The survey extends beyond this region with lower sensitivity so that the total area covered is 84 deg2. In this paper we describe the data, the data acquisition techniques and present the detection rates of the optically selected Virgo Cluster Catalogue (VCC). We detect 254 (34 per cent) of 750 VCC galaxies found within the survey boundary in at least one band and 171 galaxies are detected in all five bands. For the remainder of the galaxies we have measured strict upper limits for their FIR emission. The population of detected galaxies contains early as well as late types although the latter dominate the detection statistics. We have modelled 168 galaxies, showing no evidence of a strong synchrotron component in their FIR spectra, using a single-temperature modified blackbody spectrum with a fixed emissivity index (β = 2). A study of the χ2 distribution indicates that this model is not appropriate in all cases, and this is supported by the FIR colours which indicate a spread in β = 1-2. Statistical comparison of the dust mass and temperature distributions from 140 galaxies with χ2d.o.f. = 3 < 7.8 (95 per cent confidence level) shows that late types have typically colder, more massive dust reservoirs; the early-type dust masses have a mean of log[/M⊙] = 6.3 ± 0.3, while for late types log[/M⊙] = 7.1 ± 0.1. The late-type dust temperatures have a mean of = 19.4 ± 0.2 K, while for the early types, = 21.1 ± 0.8 K. Late-type galaxies in the cluster exhibit slightly lower dust masses than those in the field, but the cluster environment seems to have little effect on

  19. Obscuration, orientation, and the infrared properties of radio-loud active galaxies

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.; O'Dea, Christopher P.; Baum, Stefi A.; Laurikainen, Eija

    1994-01-01

    We report on a study of the mid- and far-infrared (MFIR) properties of several different classes of radio-loud active galactic nuclei (AGNs) using the IRAS database. Our goal is to try to improve the understanding of the possible relationships between the diverse classes of AGNs. The MFIR and radio properties of radio-loud AGNs are especially useful in this regard, since (excluding the blazar class, which we do not study here) the radio emission is thought to be emitted isotropically, and the radio and MFIR radiation should be much less affected by dust obscuration than radiation at shorter wavelengths. We have first compared samples of 3CR broad-line radio galaxies (BLRGs) and narrow-line radio galaxies (NLRGs) matched in radio flux and mean redshift. We find that the BLRGs are stronger than the NLRGs by a factor of 4-5 in their mid-IR emission but are similar to the NLRGs in the far-IR. This is qualitatively consistent with recent 'unification' models for NLRGs and BLRGs which invoke thermal MFIR emission from dusty 'obscuring tori,' but there may be an additional source of far-IR emission present in the more luminous broad-line objects (the radio-loud quasars) studied previously by Heckman, Chambers & Postman (1992). We have also compared samples of Fanaroff-Riley class I (FRI) and Fanaroff-Riley class II (FRII) radio galaxies matched in radio flux and redshift. The FRII galaxies are stronger MFIR emitters than the FRI galaxies by a factor of about 4. This is consistent with suggestions that the central engine in FRI galaxies produces relatively little radiant energy per unit jet power (expecially since we find that the weak MFIR emission from the FRI galaxies may not be powered by the AGN). Comparing samples of gigahertz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources versus non-GPS-CSS sources, we find that the GPS-CSS and non-GPS-CSS sources have similar MFIR strengths. This suggests that the efficiency of the conversion of jet kinetic energy

  20. Classification and Statistical Properties of Radio Galaxies with Extended Morphology at z<0.3

    NASA Astrophysics Data System (ADS)

    Lin, Yen-ting; Shen, Y.; Strauss, M.; Richards, G.; Lunnan, R.

    2011-01-01

    Extended radio galaxies (RGs) have traditionally been classified into Fanaroff-Riley (FR) I/II types, based on the ratio r of the separation between the brightest regions on either sides of the host galaxy and the total size of the radio source. We examine the distribution of various physical properties as a function of r of 1040 extended RGs at z<0.3. About 2/3 of the RGs are lobe dominated (LD) and 1/3 have prominent jets. If we follow the original definition of the FR types, i.e., a division based solely on r, FR I/II RGs overlap in their host properties. However, the rare, LD sources with r>0.8 and [OIII]5007 luminosity>106 Lsun are markedly different on average from the rest of the RGs, for they are hosted in lower mass galaxies, live in relatively sparse environments, and likely have higher accretion rates onto the supermassive black hole (SMBH). Thus, these high emission line luminosity, high-r LD RGs, and the rest of RGs form a well-defined dichotomy. Motivated by the stark differences in the nuclear emission line properties of the RG subsamples, we suggest that the accretion rate onto the SMBH may play the primary role in creating the different morphologies. At relatively high accretion rates, the accretion system may produce powerful jets that create the "classical double" morphology (roughly the LD sources with r>0.8 and emission lines); at lower accretion rates, the jets from a radiatively inefficient accretion flow generate radio lobes without apparent "hotspots" at the edge (corresponding to the majority of LD sources). At slightly lower accretion rates and in galaxies with dense galactic structure, sources with prominent jets result. It is possible that while the high accretion rate systems could affect sub-Mpc scale environments, the jets from lower accretion rate systems may efficiently suppress activity within the host galaxies.

  1. Effect of black holes in local dwarf spheroidal galaxies on gamma-ray constraints on dark matter annihilation

    NASA Astrophysics Data System (ADS)

    Gonzalez-Morales, Alma X.; Profumo, Stefano; Queiroz, Farinaldo S.

    2014-11-01

    Recent discoveries of optical signatures of black holes in dwarf galaxies indicates that low-mass galaxies can indeed host intermediate massive black holes. This motivates the assessment of the resulting effect on the host dark matter density profile, and the consequences for the constraints on the plane of the dark matter annihilation cross section versus mass, stemming from the nonobservation of gamma rays from local dwarf spheroidals with the Fermi Large Area Telescope. We compute the density profile using three different prescriptions for the black hole mass associated with a given spheroidal galaxy, and taking into account the cutoff to the density from dark matter pair-annihilation. We find that the limits on the dark matter annihilation rate from observations of individual dwarfs are enhanced by factors of a few up to 1 06 , depending on the specific galaxy, on the black hole mass prescription, and on the dark matter particle mass. We estimate limits from combined observations of a sample of 15 dwarfs, for a variety of assumptions on the dwarf black hole mass and on the dark matter density profile prior to adiabatic contraction. We find that if black holes are indeed present in local dwarf spheroidals, then, independent of assumptions, (i) the dark matter interpretation of the Galactic center gamma-ray excess would be conclusively ruled out, (ii) wino dark matter would be excluded up to masses of about 3 TeV, and (iii) vanilla thermal relic weakly interacting massive particles must be heavier than 100 GeV.

  2. Slow Quenching of Star Formation in OMEGAWINGS Clusters: Galaxies in Transition in the Local Universe

    NASA Astrophysics Data System (ADS)

    Paccagnella, A.; Vulcani, B.; Poggianti, B. M.; Moretti, A.; Fritz, J.; Gullieuszik, M.; Couch, W.; Bettoni, D.; Cava, A.; D'Onofrio, M.; Fasano, G.

    2016-01-01

    The star formation quenching depends on environment, but a full understanding of what mechanisms drive it is still missing. Exploiting a sample of galaxies with masses {M}*\\gt {10}9.8{M}⊙ , drawn from the WIde-field Nearby Galaxy-cluster Survey (WINGS) and its recent extension OMEGAWINGS, we investigate the star formation rate (SFR) as a function of stellar mass (M{}*) in galaxy clusters at 0.04\\lt z\\lt 0.07. We use non-member galaxies at 0.02 < z < 0.09 as a field control sample. Overall, we find agreement between the SFR-M{}* relation in the two environments, but detect a population of cluster galaxies with reduced SFRs, which is rare in the field. These transition galaxies are mainly found within the cluster virial radius (R200), but they impact on the SFR-M{}* relation only within 0.6R200. The ratio of transition to pure star-forming galaxies strongly depends on environment, being larger than 0.6 within 0.3R200 and rapidly decreasing with distance, while it is almost flat with M*. As galaxies move downward from the SFR-M{}* main sequence, they become redder and present older luminosity- and mass-weighted ages. These trends, together with the analysis of the star formation histories, suggest that transition galaxies have had a reduced SFR for the past 2-5 Gyr. Our results are consistent with the hypothesis that the interaction of galaxies with the intracluster medium via strangulation causes a gradual shut down of star formation, giving birth to an evolved population of galaxies in transition from being star forming to becoming passive.

  3. Characterizing ultraviolet and infrared observational properties for galaxies. II. Features of attenuation law

    SciTech Connect

    Mao, Ye-Wei; Kong, Xu; Lin, Lin E-mail: xkong@ustc.edu.cn

    2014-07-01

    Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-β relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Å bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Å bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.

  4. Semi-analytic models for the CANDELS survey: comparison of predictions for intrinsic galaxy properties

    SciTech Connect

    Lu, Yu; Wechsler, Risa H.; Somerville, Rachel S.; Croton, Darren; Porter, Lauren; Primack, Joel; Moody, Chris; Behroozi, Peter S.; Ferguson, Henry C.; Koo, David C.; Guo, Yicheng; Finlator, Kristian; Castellano, Marco; Sommariva, Veronica E-mail: rwechsler@stanford.edu

    2014-11-10

    We compare the predictions of three independently developed semi-analytic galaxy formation models (SAMs) that are being used to aid in the interpretation of results from the CANDELS survey. These models are each applied to the same set of halo merger trees extracted from the 'Bolshoi' high-resolution cosmological N-body simulation and are carefully tuned to match the local galaxy stellar mass function using the powerful method of Bayesian Inference coupled with Markov Chain Monte Carlo or by hand. The comparisons reveal that in spite of the significantly different parameterizations for star formation and feedback processes, the three models yield qualitatively similar predictions for the assembly histories of galaxy stellar mass and star formation over cosmic time. Comparing SAM predictions with existing estimates of the stellar mass function from z = 0-8, we show that the SAMs generally require strong outflows to suppress star formation in low-mass halos to match the present-day stellar mass function, as is the present common wisdom. However, all of the models considered produce predictions for the star formation rates (SFRs) and metallicities of low-mass galaxies that are inconsistent with existing data. The predictions for metallicity-stellar mass relations and their evolution clearly diverge between the models. We suggest that large differences in the metallicity relations and small differences in the stellar mass assembly histories of model galaxies stem from different assumptions for the outflow mass-loading factor produced by feedback. Importantly, while more accurate observational measurements for stellar mass, SFR and metallicity of galaxies at 1 < z < 5 will discriminate between models, the discrepancies between the constrained models and existing data of these observables have already revealed challenging problems in understanding star formation and its feedback in galaxy formation. The three sets of models are being used to construct catalogs of mock

  5. Comparing Local Starbursts to High-Redshift Galaxies: A Search for Lyman-Break Analogs

    NASA Technical Reports Server (NTRS)

    Petty, Sara M.; de Mello, Duila F.; Gallagher III, John S.; Gardner, Jonathan; Lotz, Jennifer M.; Mountain, C. Matt; Smith, Linda J.

    2008-01-01

    We compare the restframe far-ultraviolet (FUV) morphologies of 8 nearby interacting and starburst galaxies (Arp 269, M 82, Mrk 08, NGC 0520, NGC 1068, NGC 3079, NGC 3310, NGC 7673) with 54 galaxies at z approx.1.5 and 46 galaxies at z approx.4 in the Great Observatories Origins Deep Survey (GOODS) images taken with the Advanced Camera for Surveys onboard the Hubble Space Telescope. We calculate the Gini coefficient (G), the second order moment of 20% of the brightest pixels (M20), and the S ersic index (n). We find that 20% (11/54) of z approx.1.5 and 37% (17/46) of z approx.4 galaxies are bulge-like, using G and M20. We also find approx.70% of the z approx.1.5 and z approx.4 galaxies have exponential disks with n > 0.8. The 2D profile combined with the nonparametric methods provides more detail, concerning the nature of disturbed systems, such as merger and post-merger types. We also provide qualitative descriptions of each galaxy system and at each redshift. We conclude that Mrk 08, NGC 3079, and NGC 7673 have similar morphologies as the starburst FUV restframe galaxies and Lyman-break galaxies at z approx.1.5 and 4, and determine that they are Lyman-break analogs.

  6. Filaments from the galaxy distribution and from the velocity field in the local universe

    NASA Astrophysics Data System (ADS)

    Libeskind, Noam I.; Tempel, Elmo; Hoffman, Yehuda; Tully, R. Brent; Courtois, Hélène

    2015-10-01

    The cosmic web that characterizes the large-scale structure of the Universe can be quantified by a variety of methods. For example, large redshift surveys can be used in combination with point process algorithms to extract long curvilinear filaments in the galaxy distribution. Alternatively, given a full 3D reconstruction of the velocity field, kinematic techniques can be used to decompose the web into voids, sheets, filaments and knots. In this Letter, we look at how two such algorithms - the Bisous model and the velocity shear web - compare with each other in the local Universe (within 100 Mpc), finding good agreement. This is both remarkable and comforting, given that the two methods are radically different in ideology and applied to completely independent and different data sets. Unsurprisingly, the methods are in better agreement when applied to unbiased and complete data sets, like cosmological simulations, than when applied to observational samples. We conclude that more observational data is needed to improve on these methods, but that both methods are most likely properly tracing the underlying distribution of matter in the Universe.

  7. Evolution of galaxy properties across the peak of cosmic activity in cosmological hydrodynamics simulations

    NASA Astrophysics Data System (ADS)

    Devriendt, Julien

    2015-08-01

    In this talk I will review how numerical hydrodynamics simulations predict galaxies evolve in the redshift range 1properties (mass, size, morphology, star formation history).The discussion will be underpinned by recent efforts to measure the degree of alignment between galaxy spins and the large scale cosmic web filaments in which they are embedded. Relative contributions to property evolution will be split between major and minor, gas rich and gas poor mergers as well as smooth accretion, and quantitatively assessed. Finally, switching from nurture to nature, I will also discuss the role played by various feedback processes, whether of stellar origin or driven by active nuclei, in driving such changes or freezing them in.

  8. The Carnegie-Chicago Hubble Program: Discovery of the Most Distant Ultra-faint Dwarf Galaxy in the Local Universe

    NASA Astrophysics Data System (ADS)

    Lee, Myung Gyoon; Jang, In Sung; Beaton, Rachael; Seibert, Mark; Bono, Giuseppe; Madore, Barry

    2017-02-01

    Ultra-faint dwarf galaxies (UFDs) are the faintest known galaxies, and due to their incredibly low surface brightness, it is difficult to find them beyond the Local Group. We report a serendipitous discovery of a UFD, Fornax UFD1, in the outskirts of NGC 1316, a giant galaxy in the Fornax cluster. The new galaxy is located at a projected radius of 55 kpc in the south–east of NGC 1316. This UFD is found as a small group of resolved stars in the Hubble Space Telescope images of a halo field of NGC 1316, obtained as part of the Carnegie-Chicago Hubble Program. Resolved stars in this galaxy are consistent with being mostly metal-poor red giant branch (RGB) stars. Applying the tip of the RGB method to the mean magnitude of the two brightest RGB stars, we estimate the distance to this galaxy, 19.0 ± 1.3 Mpc. Fornax UFD1 is probably a member of the Fornax cluster. The color–magnitude diagram of these stars is matched by a 12 Gyr isochrone with low metallicity ([Fe/H] ≈ ‑2.4). Total magnitude and effective radius of Fornax UFD1 are MV ≈ ‑7.6 ± 0.2 mag and reff = 146 ± 9 pc, which are similar to those of Virgo UFD1 that was discovered recently in the intracluster field of Virgo by Jang & Lee. Fornax UFD1 is the most distant known UFD that is confirmed by resolved stars. This indicates that UFDs are ubiquitous and that more UFDs remain to be discovered in the Fornax cluster. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #10505 and #13691.

  9. The sub-galactic and nuclear main sequences for local star-forming galaxies

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    We describe a sub-galactic main sequence (SGMS) relating star formation rate (SFR) surface density (ΣSFR) and stellar mass density (Σ⋆) for distinct regions within star-forming galaxies, including their nuclei. We use a sample of 246 nearby star-forming galaxies from the 'Star Formation Reference Survey and demonstrate that the SGMS holds down to ∼1 kpc scales with a slope of α = 0.91 and a dispersion of 0.31 dex, similar to the well-known main sequence (MS) measured for globally integrated SFRs and stellar masses. The SGMS slope depends on galaxy morphology, with late-type galaxies (Sc-Irr) having α = 0.97 and early-type spirals (Sa-Sbc) having α = 0.81. The SGMS constructed from subregions of individual galaxies has on average the same characteristics as the composite SGMS from all galaxies. The SGMS for galaxy nuclei shows a dispersion similar to that seen for other subregions. Sampling a limited range of SFR-M⋆ space may produce either sublinearity or superlinearity of the SGMS slope. For nearly all galaxies, both SFR and stellar mass peak in the nucleus, indicating that circumnuclear clusters are among the most actively star-forming regions in the galaxy and the most massive. The nuclear SFR also correlates with total galaxy mass, forming a distinct sequence from the standard MS of star formation. The nuclear MS will be useful for studying bulge growth and for characterizing feedback processes connecting AGN and star formation.

  10. Properties of galaxies around AGNs with the most massive supermassive black holes revealed by clustering analysis

    NASA Astrophysics Data System (ADS)

    Shirasaki, Yuji; Komiya, Yutaka; Ohishi, Masatoshi; Mizumoto, Yoshihiko

    2016-04-01

    We present results of the clustering analysis between active galactic nuclei (AGNs) and galaxies at redshift 0.1-1.0, which was performed to investigate the properties of galaxies associated with the AGNs and reveal the nature of the fueling mechanism of supermassive black holes (SMBHs). We used 8059 AGNs/quasi-stellar objects (QSOs) for which virial masses of individual SMBHs were measured, and divided them into four mass groups.Cross-correlation analysis was performed to reconfirm our previous result that cross-correlation length increases with SMBH mass MBH; we obtained consistent results. A linear bias of AGN for each mass group was measured as 1.47 for MBH = 107.5-108.2 M⊙ and 3.08 for MBH = 109-1010 M⊙. The averaged color and luminosity distributions of galaxies around the AGNs/QSOs were also derived for each mass group. The galaxy color Dopt-IR was estimated from a spectral energy distribution (SED) constructed from a catalog derived by merging the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS) catalogs. The distributions of color and luminosity were derived by a subtraction method, which does not require redshift information of galaxies. The main results of this work are as follows. (1) A linear bias increases by a factor of two from the lower-mass group to the highest-mass group. (2) The environment around AGNs with the most massive SMBHs (MBH > 109 M⊙) is dominated by red sequence galaxies. (3) Marginal indication of decline in luminosity function at dimmer side of MIR > -19.5 is found for galaxies around AGNs with MBH = 108.2-109 M⊙ and nearest redshift group (z = 0.1-0.3). These results indicate that AGNs with the most massive SMBHs reside in haloes where a large fraction of galaxies have been transited to the red sequence. The accretion of hot halo gas as well as recycled gas from evolving stars can be one of the plausible mechanisms to fuel the SMBHs above ˜ 109 M⊙.

  11. Properties of Lya Emitters Around the Radio Galaxy MRC 0316-257

    SciTech Connect

    Venemans, B; Rottgering, H; Miley, G; Kurk, J; De Breuck, C; van Breugel, W; Carilli, C; Ford, H; Heckman, T; Pentericci, L; McCarthy, P

    2004-08-12

    Observations of the radio galaxy MRC 0316-257 at z = 3.13 and the surrounding field are presented. Using narrow- and broad-band imaging obtained with the VLT*, 92 candidate Ly{alpha} emitters with a rest-frame equivalent width of > 15 AngstromS were selected in a {approx} 7{prime} x 7{prime} field around the radio galaxy. Spectroscopy of 40 candidate emitters resulted in the discovery of 33 emission line galaxies of which 31 are Ly{alpha} emitters with redshifts similar to that of the radio galaxy, while the remaining two galaxies turned out to be [{omicron} II] emitters. The Ly{alpha} profiles had widths (FWHM) corresponding to 120-800 kms{sup -1},with a median of 260 kms{sup -1}. Where the signal-to-noise spectra was large enough, the Ly{alpha} profiles are found to be asymmetric, with apparent absorption troughs blueward of the profile peaks, indicative of absorption along the line of sight of an {Eta}{Iota} mass of 1-5000 {mu}{circle_dot}. Besides that of the radio galaxy and one of the emitters that is an QSO, the continuum of the emitters is faint, with luminosities ranging from 1.3 L{sub *} to < 0.03 L{sub *}.The colors of the confirmed emitters are, on average, very blue. The median UV continuum slope is {beta}=-1.65, bluer than the average slope of LBGs with Ly{alpha} emitters is 2.6 {Mu}{circle_dot}{sup -1} as measured by the Ly{alpha} emission line or < 3.9 {Mu}{circle_dot}{sup -1} as measured by the UV continuum. The properties of the Ly{alpha} galaxies (faint, blue and small) are consistent with young star forming galaxies which are nearly dust free. The density of Ly{alpha} emitting galaxies in the field around MRC 0316-257 is a factor of 3.3{sup +0.5}{sub -0.4} larger compared with the density of Ly{alpha} emitters at that redshift. The velocity distribution of the spectroscopically confirmed emitters has a dispersion of 640 km s{sup -1}, corresponding to a FWHM of 1510 km s{sup -1}, which is substantially smaller than the width of the narrow

  12. TIDAL INTERACTIONS AT THE EDGE OF THE LOCAL GROUP: NEW EVIDENCE FOR TIDAL FEATURES IN THE ANTLIA DWARF GALAXY

    SciTech Connect

    Penny, Samantha J.; Pimbblet, Kevin A.; Brown, Michael J. I.; Floyd, David J. E.; Conselice, Christopher J.; Gruetzbauch, Ruth

    2012-10-20

    Using deep B-band imaging down to {approx}{mu}{sub B} = 26 mag arcsec{sup -2}, we present evidence for tidal tails in the Antlia Dwarf galaxy, one of the most distant members of the Local Group. This elongation is in the direction of Antlia's nearest neighbor, the Magellanic-type NGC 3109. The tail is offset by <10 Degree-Sign from a vector linking the centers of the two galaxies, indicative of interactions between the pair. Combined with the warped disk previously identified in NGC 3109, Antlia and NGC 3109 must be at a small separation for tidal features to be present in Antlia. We calculate that Antlia cannot be completely disrupted by NGC 3109 in a single interaction unless its orbit pericenter is <6 kpc; however, multiple interactions could significantly alter its morphology. Therefore despite being located right at the edge of the Local Group, environmental effects are playing an important role in Antlia's evolution.

  13. THE LYMAN ALPHA MORPHOLOGY OF LOCAL STARBURST GALAXIES: RELEASE OF CALIBRATED IMAGES

    SciTech Connect

    Oestlin, Goeran; Hayes, Matthew; Kunth, Daniel; Atek, Hakim; Mas-Hesse, J. Miguel; Leitherer, Claus; Petrosian, Artashes E-mail: matthew.hayes@unige.ch

    2009-09-15

    We present reduced and calibrated high resolution Lyman-alpha (Ly{alpha}) images for a sample of six local star-forming galaxies. Targets were selected to represent a range in luminosity and metallicity and to include both known Ly{alpha} emitters and nonemitters. Far ultraviolet imaging was carried out with the Solar Blind Channel of the Advanced Camera for Surveys on the Hubble Space Telescope (HST) in the F122M (Ly{alpha} online) and F140LP (continuum) filters. The resulting Ly{alpha} images are the product of careful modeling of both the stellar and nebular continua, facilitated by supporting HST imaging at {lambda} {approx} 2200, 3300, 4400, 5500, H{alpha}, and 8000 A, combined with Starburst 99 evolutionary synthesis models, and prescriptions for dust extinction on the continuum. In all, the resulting morphologies in Ly{alpha}, H{alpha}, and UV continuum are qualitatively very different and we show that the bulk of Ly{alpha} emerges in a diffuse component resulting from resonant scattering events. Ly{alpha} escape fractions, computed from integrated H{alpha} luminosities and recombination theory, are found never to exceed 14%. Internal dust extinction is estimated in each pixel and used to correct Ly{alpha} fluxes. However, the extinction corrections are far too small (by factors from 2.6 to infinity) to reconcile the emerging global Ly{alpha} luminosities with standard recombination predictions. Surprisingly, when comparing the global equivalent widths of Ly{alpha} and H{alpha}, the two quantities appear to be anticorrelated, which may be due to the evolution of mechanical feedback from the starburst. This calls for caution in the interpretation of Ly{alpha} observations in terms of star formation rates. The images presented have a physical resolution 3 orders of magnitude better than attainable at high redshifts from the ground with current instrumentation and our images may therefore serve as useful templates for comparing with observations and modeling of

  14. Properties and Star Formation Histories of Intermediate Redshift Dwarf Low-Mass Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    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 improved constraints on the physical properties and star formation histories (SFHs) of a sample of intermediate redshift LMSFGs selected by their stellar mass or blue-compact-dwarf-like properties. Our work takes advantage of the deep UV-to-FIR photometric coverage available on the Extended-Chandra Deep Field South and our own dedicated deep VLT/VIMOS optical spectroscopy programs. On the one hand, we estimate the stellar mass (M_{*}), star formation rate (SFR), and SFH of each galaxy modeling its spectral energy distribution. We use a novel approach by Pacifici et al. 2012, that (1) consistently combines photometric (broad-band) and spectroscopic (emission line fluxes and equivalent widths) data, and (2) uses physically-motivated SFHs with non-uniform variations of the SFR as a function of time. On the other hand, we characterize the properties of their interstellar medium by analyzing the emission line features visible in the VIMOS spectroscopy. The final sample includes 91 spectroscopically confirmed LMSFGs (7.3 ≤ logM_{*}/M_{⊙} ≤ 9.5) at 0.3 galaxies over 2 dex in stellar mass, and high specific-SFR. Furthermore, they are characterized by strong emission lines, low metallicity, and an enhanced level of excitation. Our selection criterion based on mass gathers galaxies within a wide range of properties, and possibly, different evolutionary stages. Despite the individual differences, the average SFH that we obtain suggests a late and fast (˜2 Gyr prior their observation) assembly scenario for this type of system.

  15. Dark energy properties from large future galaxy surveys

    SciTech Connect

    Basse, Tobias; Bjælde, Ole Eggers; Hannestad, Steen; Hamann, Jan; Wong, Yvonne Y.Y. E-mail: oeb@phys.au.dk E-mail: sth@phys.au.dk

    2014-05-01

    We perform a detailed forecast on how well a Euclid-like survey will be able to constrain dark energy and neutrino parameters from a combination of its cosmic shear power spectrum, galaxy power spectrum, and cluster mass function measurements. We find that the combination of these three probes vastly improves the survey's potential to measure the time evolution of dark energy. In terms of a dark energy figure-of-merit defined as (σ(w{sub p})σ(w{sub a})){sup −1}, we find a value of 690 for Euclid-like data combined with Planck-like measurements of the cosmic microwave background anisotropies in a 10-dimensional cosmological parameter space, assuming a ΛCDM fiducial cosmology. For the more commonly used 7-parameter model, we find a figure-of-merit of 1900 for the same data combination. We consider also the survey's potential to measure dark energy perturbations in models wherein the dark energy is parameterised as a fluid with a nonstandard non-adiabatic sound speed, and find that in an optimistic scenario in which w{sub 0} deviates from -1 by as much as is currently observationally allowed, models with c-circumflex {sub s}{sup 2} = 10{sup −6} and c-circumflex {sub s}{sup 2} = 1 can be distinguished from one another at more than 2σ significance. We emphasise that constraints on the dark energy sound speed from cluster measurements are strongly dependent on the modelling of the cluster mass function; significantly weaker sensitivities ensue if we modify our model to include fewer features of nonlinear dark energy clustering. Finally, we find that the sum of neutrino masses can be measured with a 1σ precision of 0.015 eV, even in complex cosmological models in which the dark energy equation of state varies with time. The 1σ sensitivity to the effective number of relativistic species N{sub eff}{sup ml} is approximately 0.03, meaning that the small deviation of 0.046 from 3 in the standard value of N{sub eff}{sup ml} due to non-instantaneous decoupling and

  16. Dark energy properties from large future galaxy surveys

    NASA Astrophysics Data System (ADS)

    Basse, Tobias; Eggers Bjælde, Ole; Hamann, Jan; Hannestad, Steen; Wong, Yvonne Y. Y.

    2014-05-01

    We perform a detailed forecast on how well a Euclid-like survey will be able to constrain dark energy and neutrino parameters from a combination of its cosmic shear power spectrum, galaxy power spectrum, and cluster mass function measurements. We find that the combination of these three probes vastly improves the survey's potential to measure the time evolution of dark energy. In terms of a dark energy figure-of-merit defined as (σ(wp)σ(wa))-1, we find a value of 690 for Euclid-like data combined with Planck-like measurements of the cosmic microwave background anisotropies in a 10-dimensional cosmological parameter space, assuming a ΛCDM fiducial cosmology. For the more commonly used 7-parameter model, we find a figure-of-merit of 1900 for the same data combination. We consider also the survey's potential to measure dark energy perturbations in models wherein the dark energy is parameterised as a fluid with a nonstandard non-adiabatic sound speed, and find that in an optimistic scenario in which w0 deviates from -1 by as much as is currently observationally allowed, models with hat cs2 = 10-6 and hat cs2 = 1 can be distinguished from one another at more than 2σ significance. We emphasise that constraints on the dark energy sound speed from cluster measurements are strongly dependent on the modelling of the cluster mass function; significantly weaker sensitivities ensue if we modify our model to include fewer features of nonlinear dark energy clustering. Finally, we find that the sum of neutrino masses can be measured with a 1σ precision of 0.015 eV, even in complex cosmological models in which the dark energy equation of state varies with time. The 1σ sensitivity to the effective number of relativistic species Neffml is approximately 0.03, meaning that the small deviation of 0.046 from 3 in the standard value of Neffml due to non-instantaneous decoupling and finite temperature effects can be probed with 1σ precision for the first time.

  17. ACS Nearby Galaxy Survey

    NASA Astrophysics Data System (ADS)

    Dalcanton, Julianne

    2006-07-01

    Existing HST observations of nearby galaxies comprise a sparse and highly non-uniform archive, making comprehensive comparative studies among galaxies essentially impossible. We propose to secure HST's lasting impact on the study of nearby galaxies by undertaking a systematic, complete, and carefully crafted imaging survey of ALL galaxies in the Local Universe outside the Local Group. The resulting images will allow unprecedented measurements of: {1} the star formation history {SFH} of a >100 Mpc^3 volume of the Universe with a time resolution of Delta[log{t}]=0.25; {2} correlations between spatially resolved SFHs and environment; {3} the structure and properties of thick disks and stellar halos; and {4} the color distributions, sizes, and specific frequencies of globular and disk clusters as a function of galaxy mass and environment. To reach these goals, we will use a combination of wide-field tiling and pointed deep imaging to obtain uniform data on all 72 galaxies within a volume-limited sample extending to 3.5 Mpc, with an extension to the M81 group. For each galaxy, the wide-field imaging will cover out to 1.5 times the optical radius and will reach photometric depths of at least 2 magnitudes below the tip of the red giant branch throughout the limits of the survey volume. One additional deep pointing per galaxy will reach SNR 10 for red clump stars, sufficient to recover the ancient SFH from the color-magnitude diagram. This proposal will produce photometric information for 100 million stars {comparable to the number in the SDSS survey} and uniform multi-color images of half a square degree of sky. The resulting archive will establish the fundamental optical database for nearby galaxies, in preparation for the shift of high-resolution imaging to the near-infrared.

  18. Cosmic Dawn (CoDa): the First Radiation-Hydrodynamics Simulation of Reionization and Galaxy Formation in the Local Universe

    NASA Astrophysics Data System (ADS)

    Ocvirk, Pierre; Gillet, Nicolas; Shapiro, Paul R.; Aubert, Dominique; Iliev, Ilian T.; Teyssier, Romain; Yepes, Gustavo; Choi, Jun-Hwan; Sullivan, David; Knebe, Alexander; Gottlöber, Stefan; D'Aloisio, Anson; Park, Hyunbae; Hoffman, Yehuda; Stranex, Timothy

    2016-12-01

    Cosmic reionization by starlight from early galaxies affected their evolution, thereby impacting reionization itself. Star formation suppression, for example, may explain the observed underabundance of Local Group dwarfs relative to N-body predictions for cold dark matter. Reionization modelling requires simulating volumes large enough [˜ (100 Mpc)3] to sample reionization `patchiness', while resolving millions of galaxy sources above ˜108 M⊙ combining gravitational and gas dynamics with radiative transfer. Modelling the Local Group requires initial cosmological density fluctuations pre-selected to form the well-known structures of the Local Universe today. Cosmic Dawn (`CoDa') is the first such fully coupled, radiation-hydrodynamics simulation of reionization of the Local Universe. Our new hybrid CPU-GPU code, RAMSES-CUDATON, performs hundreds of radiative transfer and ionization rate-solver timesteps on the GPUs for each hydro-gravity timestep on the CPUs. CoDa simulated (91Mpc)3 with 40963 particles and cells, to redshift 4.23, on ORNL supercomputer Titan, utilizing 8192 cores and 8192 GPUs. Global reionization ended slightly later than observed. However, a simple temporal rescaling which brings the evolution of ionized fraction into agreement with observations also reconciles ionizing flux density, cosmic star formation history, CMB electron scattering optical depth and galaxy UV luminosity function with their observed values. Photoionization heating suppressed the star formation of haloes below ˜2 × 109 M⊙, decreasing the abundance of faint galaxies around MAB1600 = [-10, -12]. For most of reionization, star formation was dominated by haloes between 1010-1011 M⊙ , so low-mass halo suppression was not reflected by a distinct feature in the global star formation history. Intergalactic filaments display sheathed structures, with hot envelopes surrounding cooler cores, but do not self-shield, unlike regions denser than 100 <ρ>.

  19. The Abundance Properties of Nearby Late-type Galaxies. I. The Data

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    We investigate the oxygen and nitrogen abundance distributions across the optical disks of 130 nearby late-type galaxies using around 3740 published spectra of H II regions. We use these data in order to provide homogeneous abundance determinations for all objects in the sample, including H II regions in which not all of the usual diagnostic lines were measured. Examining the relation between N and O abundances in these galaxies we find that the abundances in their centers and at their isophotal R 25 disk radii follow the same relation. The variation in N/H at a given O/H is around 0.3 dex. We suggest that the observed spread in N/H may be partly caused by the time delay between N and O enrichment and the different star formation histories in galaxies of different morphological types and dimensions. We study the correlations between the abundance properties (central O and N abundances, radial O and N gradients) of a galaxy and its morphological type and dimension.

  20. Clustering properties of luminous red galaxies with the Sloan Digital Sky Survey imaging data

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil

    We study the 3D spatial clustering properties of luminous red galaxies in the Sloan Digital Sky Survey (SDSS) imaging data, and discuss their cosmological implications. The need to control systematics leads us to propose a new algorithm to photometrically calibrate wide-field imaging surveys. Applying this to the SDSS, we achieve a 1% relative photometric calibration over 8500 square degrees, an improvement of a factor of ~2 over current calibrations. We then calibrate distances, derived from only the SDSS imaging data, to a class of galaxies with very regular colours, the luminous red galaxies (LRGs). Measuring their 2-point correlation function allows us to detect the non-random clustering of galaxies on gigaparsec scales for the first time. We also detect the imprint of acoustic oscillations in the plasma of the early Universe on the clustering of the LRGs. We finally discuss cross-correlating the LRGs with the cosmic microwave background, detecting the integrated Sachs-Wolfe effect and providing further evidence for a late-time acceleration in the expansion of the Universe.

  1. Local topological and chiral properties of QCD.

    SciTech Connect

    de Forcrand, Ph.

    1998-10-30

    To elucidate the role played by instantons in chiral symmetry breaking, the authors explore their properties, in full QCD, around the critical temperature. They study in particular, spatial correlations between low-lying Dirac eigenmodes and instantons. Their measurements are compared with the predictions of instanton-based models.

  2. THE OBSERVED RELATION BETWEEN STELLAR MASS, DUST EXTINCTION, AND STAR FORMATION RATE IN LOCAL GALAXIES

    SciTech Connect

    Zahid, H. J.; Kewley, L. J.; Kudritzki, R. P.; Yates, R. M.

    2013-02-15

    In this study, we investigate the relation between stellar mass, dust extinction, and star formation rate (SFR) using {approx}150,000 star-forming galaxies from SDSS DR7. We show that the relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass, dust extinction is anti-correlated with the SFR at stellar masses <10{sup 10} M {sub Sun }. There is a sharp transition in the relation at a stellar mass of 10{sup 10} M {sub Sun }. At larger stellar masses, dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction, and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity, and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with stellar masses >10{sup 10} M {sub Sun} is shown to extend to the population of quiescent galaxies suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction, and SFR may be related to the processes leading to the shutdown of star formation in galaxies.

  3. The merger fraction of active and inactive galaxies in the local Universe through an improved non-parametric classification

    NASA Astrophysics Data System (ADS)

    Cotini, Stefano; Ripamonti, Emanuele; Caccianiga, Alessandro; Colpi, Monica; Della Ceca, Roberto; Mapelli, Michela; Severgnini, Paola; Segreto, Alberto

    2013-05-01

    We investigate the possible link between mergers and the enhanced activity of supermassive black holes (SMBHs) at the centre of galaxies, by comparing the merger fraction of a local sample (0.003 ≤ z < 0.03) of active galaxies - 59 active galactic nuclei host galaxies selected from the All-Sky Swift Burst Alert Telescope (BAT) Survey - with an appropriate control sample (247 sources extracted from the HyperLeda catalogue) that has the same redshift distribution as the BAT sample. We detect the interacting systems in the two samples on the basis of non-parametric structural indexes of concentration (C), asymmetry (A), clumpiness (S), Gini coefficient (G) and second-order momentum of light (M20). In particular, we propose a new morphological criterion, based on a combination of all these indexes, that improves the identification of interacting systems. We also present a new software - PyCASSo (PYTHON CAS software) - for the automatic computation of the structural indexes. After correcting for the completeness and reliability of the method, we find that the fraction of interacting galaxies among the active population (20{^{+ 7}_{- 5}} per cent) exceeds the merger fraction of the control sample (4{^{+ 1.7}_{- 1.2}} per cent). Choosing a mass-matched control sample leads to equivalent results, although with slightly lower statistical significance. Our findings support the scenario in which mergers trigger the nuclear activity of SMBHs.

  4. Mid-infrared properties of luminous infrared galaxies. II. Probing the dust and gas physics of the goals sample

    SciTech Connect

    Stierwalt, S.; Armus, L.; Diaz-Santos, T.; Marshall, J.; Haan, S.; Howell, J.; Murphy, E. J.; Inami, H.; Petric, A. O.; Charmandaris, V.; Evans, A. S.; Iwasawa, K.; Kim, D. C.; Rich, J. A.; Spoon, H. W. W.; U, V.

    2014-08-01

    The Great Observatories All-sky LIRG Survey (GOALS) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here, we present the results of a multi-component, spectral decomposition analysis of the low-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph spectra from 5-38 μm of 244 LIRG nuclei. The detailed fits and high-quality spectra allow for characterization of the individual polycyclic aromatic hydrocarbon (PAH) features, warm molecular hydrogen emission, and optical depths for both silicate dust grains and water ices. We find that starbursting LIRGs, which make up the majority of the GOALS sample, are very consistent in their MIR properties (i.e., τ{sub 9.7μm}, τ{sub ice}, neon line ratios, and PAH feature ratios). However, as their EQW{sub 6.2{sub μm}} decreases, usually an indicator of an increasingly dominant active galactic nucleus (AGN), LIRGs cover a larger spread in these MIR parameters. The contribution from PAH emission to the total IR luminosity (L(PAH)/L(IR)) in LIRGs varies from 2%-29% and LIRGs prior to their first encounter show significantly higher L(PAH)/L(IR) ratios on average. We observe a correlation between the strength of the starburst (represented by IR8 = L{sub IR}/L{sub 8{sub μm}}) and the PAH fraction at 8 μm but no obvious link between IR8 and the 7.7 to 11.3 PAH ratio, suggesting that the fractional photodissociation region (PDR) emission, and not the overall grain properties, is associated with the rise in IR8 for galaxies off the starburst main sequence. We detect crystalline silicate features in ∼6% of the sample but only in the most obscure sources (s{sub 9.7{sub μm}} < –1.24). Ice absorption features are observed in ∼11% (56%) of GOALS LIRGs (ULIRGs) in sources with a range of silicate depths. Most GOALS LIRGs have L(H{sub 2})/L(PAH) ratios elevated above those observed for normal star-forming galaxies and exhibit a trend for increasing L(H{sub 2})/L

  5. Connecting the Silicate Dust and Gas Properties of Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; Morrison, Sean

    2016-01-01

    We present recent results from our program investigating the silicate dust properties in distant galaxies using quasar absorption systems. The dust and gas properties of distant galaxies can be characterized by studying the absorption features produced by them along the sightlines to luminous background quasars. Based on our prior finding that silicate dust absorption in z<1.5 quasar absorption systems exhibits a range of optical depths and absorption feature substructures, suggestive of silicate grain property variations, we are investigating silicate dust absorption in quasar absorption systems toward quasars with archival Spitzer Space Telescope Infrared Spectrograph (IRS) spectra. We present our measurements of the 10 and/or 18 micron silicate dust absorption feature(s) in these systems, and discuss constraints on the grain properties, such as composition and crystallinity, based on the shape and substructure present in these features. We also investigate the correlations between the silicate dust properties and the reddening. Connections between the silicate dust and gas phase metal absorption properties can also be probed for some of our targets with archival ground-based spectra. These relationships will yield valuable insights into the star formation history and evolution of metals and dust. This work is supported by NASA through ADAP grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grant AST-1108830 to the University of South Carolina.

  6. Physical Properties of Compact Star-forming Galaxies at z ˜ 2-3

    NASA Astrophysics Data System (ADS)

    Fang, Guanwen; Ma, Zhongyang; Kong, Xu; Fan, Lulu

    2015-07-01

    We present a study on the physical properties of compact star-forming galaxies (cSFGs) with M* ≥ 1010M⊙ and 2 ≤ z ≤ 3 in the COSMOS (Cosmic Evolution Survey) and GOODS-S (Great Observatories Origins Deep Survey South) fields. We find that massive cSFGs have a comoving number density of (1.0