When the Jeans Do Not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies

International Nuclear Information System (INIS)

El-Badry, Kareem; Quataert, Eliot; Wetzel, Andrew R.; Hopkins, Philip F.; Geha, Marla; Kereš, Dusan; Chan, T. K.; Faucher-Giguère, Claude-André

2017-01-01

In low-mass galaxies, stellar feedback can drive gas outflows that generate non-equilibrium fluctuations in the gravitational potential. Using cosmological zoom-in baryonic simulations from the Feedback in Realistic Environments project, we investigate how these fluctuations affect stellar kinematics and the reliability of Jeans dynamical modeling in low-mass galaxies. We find that stellar velocity dispersion and anisotropy profiles fluctuate significantly over the course of galaxies’ starburst cycles. We therefore predict an observable correlation between star formation rate and stellar kinematics: dwarf galaxies with higher recent star formation rates should have systemically higher stellar velocity dispersions. This prediction provides an observational test of the role of stellar feedback in regulating both stellar and dark-matter densities in dwarf galaxies. We find that Jeans modeling, which treats galaxies as virialized systems in dynamical equilibrium, overestimates a galaxy’s dynamical mass during periods of post-starburst gas outflow and underestimates it during periods of net inflow. Short-timescale potential fluctuations lead to typical errors of ∼20% in dynamical mass estimates, even if full three-dimensional stellar kinematics—including the orbital anisotropy—are known exactly. When orbital anisotropy is not known a priori, typical mass errors arising from non-equilibrium fluctuations in the potential are larger than those arising from the mass-anisotropy degeneracy. However, Jeans modeling alone cannot reliably constrain the orbital anisotropy, and problematically, it often favors anisotropy models that do not reflect the true profile. If galaxies completely lose their gas and cease forming stars, fluctuations in the potential subside, and Jeans modeling becomes much more reliable.

Compact Starburst Galaxies with Fast Outflows: Spatially Resolved Stellar Mass Profiles

Science.gov (United States)

Gottlieb, Sophia; Diamond-Stanic, Aleksandar; Lipscomb, Charles; Ohene, Senyo; Rines, Josh; Moustakas, John; Sell, Paul; Tremonti, Christy; Coil, Alison; Rudnick, Gregory; Hickox, Ryan C.; Geach, James; Kepley, Amanda

2018-01-01

Powerful galactic winds driven by stellar feedback and black hole accretion are thought to play an important role in regulating star formation in galaxies. In particular, strong stellar feedback from supernovae, stellar winds, radiation pressure, and cosmic rays is required by simulations of star-forming galaxies to prevent the vast majority of baryons from cooling and collapsing to form stars. However, it remains unclear whether these stellar processes play a significant role in expelling gas and shutting down star formation in massive progenitors of quiescent galaxies. What are the limits of stellar feedback? We present multi-band photometry with HST/WFC3 (F475W, F814W, F160W) for a dozen compact starburst galaxies at z~0.6 with half-light radii that suggest incredibly large central escape velocities. These massive galaxies are driving fast (>1000 km/s) outflows that have been previously attributed to stellar feedback associated with the compact (r~100 pc) starburst. But how compact is the stellar mass? In the context of the stellar feedback hypothesis, it is unclear whether these fast outflows are being driven at velocities comparable to the escape velocity of an incredibly dense stellar system (as predicted by some models of radiation-pressure winds) or at velocities that exceed the central escape velocity by large factor. Our spatially resolved measurements with HST show that the stellar mass is more extended than the light, and this requires that the physical mechanism responsible for driving the winds must be able to launch gas at velocities that are factors of 5-10 beyond the central escape velocity.

Stellar mass estimation based on IRAC photometry for Spitzer SWIRE-field galaxies

International Nuclear Information System (INIS)

Zhu Yinan; Wu Hong; Li Haining; Cao Chen

2010-01-01

We analyze the feasibility of estimating the stellar mass of galaxies by mid-infrared luminosities based on a large sample of galaxies cross-identified from Spitzer SWIRE fields and the SDSS spectrographic survey. We derived the formulae to calculate the stellar mass by using IRAC 3.6 μm and 4.5 μm luminosities. The mass-to-luminosity ratios of IRAC 3.6 μm and 4.5 μm luminosities are more sensitive to the star formation history of galaxies than to other factors, such as the intrinsic extinction, metallicity and star formation rate. To remove the effect of star formation history, we used g - r color to recalibrate the formulae and obtain a better result. Researchers must be more careful when estimating the stellar mass of low metallicity galaxies using our formulae. Due to the emission from dust heated by the hottest young stars, luminous infrared galaxies present higher IRAC 4.5 μm luminosities compared to IRAC 3.6 μm luminosities. For most of type-II AGNs, the nuclear activity cannot enhance 3.6 μm and 4.5 μm luminosities compared with normal galaxies. Star formation in our AGN-hosting galaxies is also very weak, almost all of which are early-type galaxies.

The influence of galaxy environment on the stellar initial mass function of early-type galaxies

Science.gov (United States)

Rosani, Giulio; Pasquali, Anna; La Barbera, Francesco; Ferreras, Ignacio; Vazdekis, Alexandre

2018-06-01

In this paper, we investigate whether the stellar initial mass function (IMF) of early-type galaxies depends on their host environment. To this purpose, we have selected a sample of early-type galaxies from the SPIDER catalogue, characterized their environment through the group catalogue of Wang et al., and used their optical Sloan Digital Sky Survey (SDSS) spectra to constrain the IMF slope, through the analysis of IMF-sensitive spectral indices. To reach a high enough signal-to-noise ratio, we have stacked spectra in velocity dispersion (σ0) bins, on top of separating the sample by galaxy hierarchy and host halo mass, as proxies for galaxy environment. In order to constrain the IMF, we have compared observed line strengths and predictions of MIUSCAT/EMILES synthetic stellar population models, with varying age, metallicity, and `bimodal' (low-mass tapered) IMF slope (Γ _b). Consistent with previous studies, we find that Γ _b increases with σ0, becoming bottom-heavy (i.e. an excess of low-mass stars with respect to the Milky Way like IMF) at high σ0. We find that this result is robust against the set of isochrones used in the stellar population models, as well as the way the effect of elemental abundance ratios is taken into account. We thus conclude that it is possible to use currently state-of-the-art stellar population models and intermediate resolution spectra to consistently probe IMF variations. For the first time, we show that there is no dependence of Γb on environment or galaxy hierarchy, as measured within the 3 arcsec SDSS fibre, thus leaving the IMF as an intrinsic galaxy property, possibly set already at high redshift.

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

Science.gov (United States)

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.

First results from the IllustrisTNG simulations: the stellar mass content of groups and clusters of galaxies

Science.gov (United States)

Pillepich, Annalisa; Nelson, Dylan; Hernquist, Lars; Springel, Volker; Pakmor, Rüdiger; Torrey, Paul; Weinberger, Rainer; Genel, Shy; Naiman, Jill P.; Marinacci, Federico; Vogelsberger, Mark

2018-03-01

The IllustrisTNG project is a new suite of cosmological magnetohydrodynamical simulations of galaxy formation performed with the AREPO code and updated models for feedback physics. Here, we introduce the first two simulations of the series, TNG100 and TNG300, and quantify the stellar mass content of about 4000 massive galaxy groups and clusters (1013 ≤ M200c/M⊙ ≤ 1015) at recent times (z ≤ 1). The richest clusters have half of their total stellar mass bound to satellite galaxies, with the other half being associated with the central galaxy and the diffuse intracluster light. Haloes more massive than about 5 × 1014 M⊙ have more diffuse stellar mass outside 100 kpc than within 100 kpc, with power-law slopes of the radial mass density distribution as shallow as the dark matter's ( - 3.5 ≲ α3D ≲ -3). Total halo mass is a very good predictor of stellar mass, and vice versa: at z = 0, the 3D stellar mass measured within 30 kpc scales as ∝(M500c)0.49 with a ˜0.12 dex scatter. This is possibly too steep in comparison to the available observational constraints, even though the abundance of The Next Generation less-massive galaxies ( ≲ 1011 M⊙ in stars) is in good agreement with the measured galaxy stellar mass functions at recent epochs. The 3D sizes of massive galaxies fall too on a tight (˜0.16 dex scatter) power-law relation with halo mass, with r^stars_0.5 ∝ (M_200c)^{0.53}. Even more fundamentally, halo mass alone is a good predictor for the whole stellar mass profiles beyond the inner few kiloparsecs, and we show how on average these can be precisely recovered given a single-mass measurement of the galaxy or its halo.

SALPETER NORMALIZATION OF THE STELLAR INITIAL MASS FUNCTION FOR MASSIVE GALAXIES AT z ∼ 1

International Nuclear Information System (INIS)

Shetty, Shravan; Cappellari, Michele

2014-01-01

The stellar initial mass function (IMF) is a key parameter for studying galaxy evolution. Here we measure the IMF mass normalization for a sample of 68 field galaxies in the redshift range 0.7-0.9 within the Extended Groth Strip. To do this we derive the total (stellar + dark matter) mass-to-light [(M/L)] ratio using axisymmetric dynamical models. Within the region where we have kinematics (about one half-light radius), the models assume (1) that mass follows light, implying negligible differences between the slope of the stellar and total density profiles, (2) constant velocity anisotropy (β z ≡1−σ z 2 /σ R 2 =0.2), and (3) that galaxies are seen at the average inclination for random orientations (i.e., i = 60°, where i = 90° represents edge-on). The dynamical models are based on anisotropic Jeans equations, constrained by Hubble Space Telescope/Advanced Camera for Surveys imaging and the central velocity dispersion of the galaxies, extracted from good-quality spectra taken by the DEEP2 survey. The population (M/L) are derived from full-spectrum fitting of the same spectra with a grid of simple stellar population models. Recent dynamical modeling results from the ATLAS 3D project and numerical simulations of galaxy evolution indicate that the dark matter fraction within the central regions of our galaxies should be small. This suggests that our derived total (M/L) should closely approximate the stellar M/L. Our comparison of the dynamical (M/L) and the population (M/L) then implies that for galaxies with stellar mass M * ≳ 10 11 M ☉ , the average normalization of the IMF is consistent with a Salpeter slope, with a substantial scatter. This is similar to what is found within a similar mass range for nearby galaxies

The stellar mass-size evolution of galaxies from z=7 to z=0

NARCIS (Netherlands)

Mosleh, Moein

2013-01-01

One of the important properties of galaxies is their sizes which correlate with their stellar masses. Evidence is provided by many recent studies that the sizes of galaxies were smaller at higher redshifts compared to galaxies of similar mass in the local Universe. It is essential to understand

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

Energy Technology Data Exchange (ETDEWEB)

Jabran Zahid, H. [Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kudritzki, Rolf-Peter; Ho, I-Ting [University of Hawaii at Manoa, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Conroy, Charlie [Department of Astronomy, Harvard University, Cambridge, MA, 02138 (United States); Andrews, Brett, E-mail: zahid@cfa.harvard.edu [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260 (United States)

2017-09-20

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

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

International Nuclear Information System (INIS)

Jabran Zahid, H.; Kudritzki, Rolf-Peter; Ho, I-Ting; Conroy, Charlie; Andrews, Brett

2017-01-01

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

Dynamics of Dwarf Galaxies Disfavor Stellar-Mass Black Holes as Dark Matter.

Science.gov (United States)

Koushiappas, Savvas M; Loeb, Abraham

2017-07-28

We study the effects of black hole dark matter on the dynamical evolution of stars in dwarf galaxies. We find that mass segregation leads to a depletion of stars in the center of dwarf galaxies and the appearance of a ring in the projected stellar surface density profile. Using Segue 1 as an example we show that current observations of the projected surface stellar density rule out at the 99.9% confidence level the possibility that more than 6% of the dark matter is composed of black holes with a mass of few tens of solar masses.

Origin of a bottom-heavy stellar initial mass function in elliptical galaxies

International Nuclear Information System (INIS)

Bekki, Kenji

2013-01-01

We investigate the origin of a bottom-heavy stellar initial mass function (IMF) recently observed in elliptical galaxies by using chemical evolution models with a non-universal IMF. We adopt the variable Kroupa IMF with the three slopes (α 1 , α 2 , and α 3 ) dependent on metallicities ([Fe/H]) and densities (ρ g ) of star-forming gas clouds and thereby search for the best IMF model that can reproduce (1) the observed steep IMF slope (α 2 ∼ 3, i.e., bottom-heavy) for low stellar masses (m ≤ 1 M ☉ ) and (2) the correlation of α 2 with chemical properties of elliptical galaxies in a self-consistent manner. We find that if the IMF slope α 2 depends on both [Fe/H] and ρ g , then elliptical galaxies with higher [Mg/Fe] can have steeper α 2 (∼3) in our models. We also find that the observed positive correlation of stellar mass-to-light ratios (M/L) with [Mg/Fe] in elliptical galaxies can be quantitatively reproduced in our models with α 2 ∝β[Fe/H] + γlog ρ g , where β ∼ 0.5 and γ ∼ 2. We discuss whether the IMF slopes for low-mass (α 2 ) and high-mass stars (α 3 ) need to vary independently from each other to explain a number of IMF-related observational results self-consistently. We also briefly discuss why α 2 depends differently on [Fe/H] in dwarf and giant elliptical galaxies.

GAMA/H-ATLAS: THE DUST OPACITY-STELLAR MASS SURFACE DENSITY RELATION FOR SPIRAL GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Grootes, M. W.; Tuffs, R. J.; Andrae, E. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Popescu, C. C.; Pastrav, B. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Gunawardhana, M.; Taylor, E. N. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 206 (Australia); Kelvin, L. S.; Driver, S. P. [Scottish Universities' Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom); Liske, J. [European Southern Observatory, Karl-Schwarzschild Str. 2, D-85748 Garching (Germany); Seibert, M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Graham, Alister W. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Baldry, I. K. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Bourne, N. [Centre for Astronomy and Particle Theory, The School of Physics and Astronomy, Nottingham University, University Park Campus, Nottingham NG7 2RD (United Kingdom); Brough, S. [Australian Astronomical Observatory, P.O. Box 296, Epping, NSW 1710 (Australia); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Dariush, A. [Physics Department, Imperial College, Prince Consort Road, London SW7 2AZ (United Kingdom); De Zotti, G. [INAF-Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Dunne, L., E-mail: meiert.grootes@mpi-hd.mpg.de [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand); and others

2013-03-20

We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, {tau}{sup f}{sub B}, and the stellar mass surface density, {mu}{sub *}, of nearby (z {<=} 0.13) spiral galaxies. This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey, which were detected in the FIR/submillimeter (submm) in the Herschel-ATLAS science demonstration phase field. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to stellar mass surface density, we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and Sersic-profile morphological fits. Considered together with previously established empirical relationships of stellar mass to metallicity and gas mass, the near linearity and high constant of proportionality of the {tau}{sub B}{sup f} - {mu}{sub *} relation disfavors a stellar origin for the bulk of refractory grains in spiral galaxies, instead being consistent with the existence of a ubiquitous and very rapid mechanism for the growth of dust in the interstellar medium. We use the {tau}{sub B}{sup f} - {mu}{sub *} relation in conjunction with the radiation transfer model for spiral galaxies of Popescu and Tuffs to derive intrinsic scaling relations between specific star formation rate (SFR), stellar mass, and stellar surface density, in which attenuation of the UV light used for the measurement of SFR is corrected on an object-to-object basis. A marked reduction in scatter in these relations is achieved which we demonstrate is due to correction of both the inclination-dependent and face-on components of attenuation. Our results are consistent with a general picture of spiral galaxies in which most of the submm emission originates from grains residing in translucent structures, exposed to UV in the diffuse interstellar

The impact of Spitzer infrared data on stellar mass estimates - and a revised galaxy stellar mass function at 0 < z < 5

Science.gov (United States)

Elsner, F.; Feulner, G.; Hopp, U.

2008-01-01

Aims:We estimate stellar masses of galaxies in the high redshift universe with the intention of determining the influence of newly available Spitzer/IRAC infrared data on the analysis. Based on the results, we probe the mass assembly history of the universe. Methods: We use the GOODS-MUSIC catalog, which provides multiband photometry from the U-filter to the 8 μm Spitzer band for almost 15 000 galaxies with either spectroscopic (for ≈7% of the sample) or photometric redshifts, and apply a standard model fitting technique to estimate stellar masses. We than repeat our calculations with fixed photometric redshifts excluding Spitzer photometry and directly compare the outcomes to look for systematic deviations. Finally we use our results to compute stellar mass functions and mass densities up to redshift z = 5. Results: We find that stellar masses tend to be overestimated on average if further constraining Spitzer data are not included into the analysis. Whilst this trend is small up to intermediate redshifts z ⪉ 2.5 and falls within the typical error in mass, the deviation increases strongly for higher redshifts and reaches a maximum of a factor of three at redshift z ≈ 3.5. Thus, up to intermediate redshifts, results for stellar mass density are in good agreement with values taken from literature calculated without additional Spitzer photometry. At higher redshifts, however, we find a systematic trend towards lower mass densities if Spitzer/IRAC data are included.

Glimpsing the imprint of local environment on the galaxy stellar mass function

Science.gov (United States)

Tomczak, Adam R.; Lemaux, Brian C.; Lubin, Lori M.; Gal, Roy R.; Wu, Po-Feng; Holden, Bradford; Kocevski, Dale D.; Mei, Simona; Pelliccia, Debora; Rumbaugh, Nicholas; Shen, Lu

2017-12-01

We investigate the impact of local environment on the galaxy stellar mass function (SMF) spanning a wide range of galaxy densities from the field up to dense cores of massive galaxy clusters. Data are drawn from a sample of eight fields from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. Deep photometry allow us to select mass-complete samples of galaxies down to 109 M⊙. Taking advantage of >4000 secure spectroscopic redshifts from ORELSE and precise photometric redshifts, we construct three-dimensional density maps between 0.55 environmental dependence in the SMFs of star-forming and quiescent galaxies, although not quite as strongly for the quiescent subsample. To characterize the connection between the SMF of field galaxies and that of denser environments, we devise a simple semi-empirical model. The model begins with a sample of ≈106 galaxies at zstart = 5 with stellar masses distributed according to the field. Simulated galaxies then evolve down to zfinal = 0.8 following empirical prescriptions for star-formation, quenching and galaxy-galaxy merging. We run the simulation multiple times, testing a variety of scenarios with differing overall amounts of merging. Our model suggests that a large number of mergers are required to reproduce the SMF in dense environments. Additionally, a large majority of these mergers would have to occur in intermediate density environments (e.g. galaxy groups).

Characterization of Omega-WINGS galaxy clusters. I. Stellar light and mass profiles

Science.gov (United States)

Cariddi, S.; D'Onofrio, M.; Fasano, G.; Poggianti, B. M.; Moretti, A.; Gullieuszik, M.; Bettoni, D.; Sciarratta, M.

2018-02-01

Context. Galaxy clusters are the largest virialized structures in the observable Universe. Knowledge of their properties provides many useful astrophysical and cosmological information. Aims: Our aim is to derive the luminosity and stellar mass profiles of the nearby galaxy clusters of the Omega-WINGS survey and to study the main scaling relations valid for such systems. Methods: We merged data from the WINGS and Omega-WINGS databases, sorted the sources according to the distance from the brightest cluster galaxy (BCG), and calculated the integrated luminosity profiles in the B and V bands, taking into account extinction, photometric and spatial completeness, K correction, and background contribution. Then, by exploiting the spectroscopic sample we derived the stellar mass profiles of the clusters. Results: We obtained the luminosity profiles of 46 galaxy clusters, reaching r200 in 30 cases, and the stellar mass profiles of 42 of our objects. We successfully fitted all the integrated luminosity growth profiles with one or two embedded Sérsic components, deriving the main clusters parameters. Finally, we checked the main scaling relation among the clusters parameters in comparison with those obtained for a selected sample of early-type galaxies (ETGs) of the same clusters. Conclusions: We found that the nearby galaxy clusters are non-homologous structures such as ETGs and exhibit a color-magnitude (CM) red-sequence relation very similar to that observed for galaxies in clusters. These properties are not expected in the current cluster formation scenarios. In particular the existence of a CM relation for clusters, shown here for the first time, suggests that the baryonic structures grow and evolve in a similar way at all scales.

STELLAR, GAS, AND DARK MATTER CONTENT OF BARRED GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Cervantes Sodi, Bernardo, E-mail: b.cervantes@crya.unam.mx [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Campus Morelia, A.P. 3-72, C.P. 58089 Michoacán, México (Mexico)

2017-01-20

We select a sample of galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) where galaxies are classified, through visual inspection, as hosting strong bars, weak bars, or as unbarred galaxies, and make use of H i mass and kinematic information from the Arecibo Legacy Fast ALFA survey catalog, to study the stellar, atomic gas, and dark matter content of barred disk galaxies. We find, in agreement with previous studies, that the bar fraction increases with increasing stellar mass. A similar trend is found with total baryonic mass, although the dependence is not as strong as with stellar mass, due to the contribution of gas. The bar fraction shows a decrease with increasing gas mass fraction. This anticorrelation between the likelihood of a galaxy hosting a bar with the gas richness of the galaxy results from the inhibiting effect the gas has in the formation of bars. We also find that for massive galaxies with stellar masses larger than 10{sup 10} M {sub ⊙}, at fixed stellar mass, the bar fraction decreases with increasing global halo mass (i.e., halo mass measured up to a radius of the order of the H i disk extent).

MOIRCS DEEP SURVEY. V. A UNIVERSAL RELATION FOR STELLAR MASS AND SURFACE BRIGHTNESS OF GALAXIES

International Nuclear Information System (INIS)

Ichikawa, Takashi; Kajisawa, Masaru; Yamada, Toru; Akiyama, Masayuki; Yoshikawa, Tomohiro; Onodera, Masato; Konishi, Masahiro

2010-01-01

We present a universal linear correlation between the stellar mass and surface brightness (SB) of galaxies at 0.3 -2.0∼-0.8 , in addition to dimming as (1 + z) 4 by the cosmological expansion effect. The brightening depends on galaxy color and stellar mass. The blue population (rest-frame U - V -0.8±0.3 in the rest-V band. On the other hand, the red population (U - V>0) and the massive galaxies (M * >10 10 M sun ) show stronger brightening, (1 + z) -1.5±0.1 . By comparison with galaxy evolution models, the phenomena are well understood by the pure luminosity evolution of galaxies out to z ∼ 3.

The dwarfs beyond: The stellar-to-halo mass relation for a new sample of intermediate redshift low-mass galaxies

Energy Technology Data Exchange (ETDEWEB)

Miller, Sarah H.; Ellis, Richard S.; Newman, Andrew B. [California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 (United States); Benson, Andrew, E-mail: smiller@astro.caltech.edu [Carnegie Observatories, 813 Santa Barbara St, Pasadena, CA 91101 (United States)

2014-02-20

A number of recent challenges to the standard ΛCDM paradigm relate to discrepancies that arise in comparing the abundance and kinematics of local dwarf galaxies with the predictions of numerical simulations. Such arguments rely heavily on the assumption that the Local Volume's dwarf and satellite galaxies form a representative distribution in terms of their stellar-to-halo mass ratios. To address this question, we present new, deep spectroscopy using DEIMOS on Keck for 82 low-mass (10{sup 7}-10{sup 9} M {sub ☉}), star-forming galaxies at intermediate redshift (0.2 < z < 1). For 50% of these we are able to determine resolved rotation curves using nebular emission lines and thereby construct the stellar mass Tully-Fisher relation to masses as low as 10{sup 7} M {sub ☉}. Using scaling relations determined from weak lensing data, we convert this to a stellar-to-halo mass relation for comparison with abundance matching predictions. We find a discrepancy between our observations and the predictions from abundance matching in the sense that we observe 3-12 times more stellar mass at a given halo mass. We suggest possible reasons for this discrepancy, as well as improved tests for the future.

SDSS-IV MaNGA: global stellar population and gradients for about 2000 early-type and spiral galaxies on the mass-size plane

Science.gov (United States)

Li, Hongyu; Mao, Shude; Cappellari, Michele; Ge, Junqiang; Long, R. J.; Li, Ran; Mo, H. J.; Li, Cheng; Zheng, Zheng; Bundy, Kevin; Thomas, Daniel; Brownstein, Joel R.; Roman Lopes, Alexandre; Law, David R.; Drory, Niv

2018-05-01

We perform full spectrum fitting stellar population analysis and Jeans Anisotropic modelling of the stellar kinematics for about 2000 early-type galaxies (ETGs) and spiral galaxies from the MaNGA DR14 sample. Galaxies with different morphologies are found to be located on a remarkably tight mass plane which is close to the prediction of the virial theorem, extending previous results for ETGs. By examining an inclined projection (`the mass-size' plane), we find that spiral and early-type galaxies occupy different regions on the plane, and their stellar population properties (i.e. age, metallicity, and stellar mass-to-light ratio) vary systematically along roughly the direction of velocity dispersion, which is a proxy for the bulge fraction. Galaxies with higher velocity dispersions have typically older ages, larger stellar mass-to-light ratios and are more metal rich, which indicates that galaxies increase their bulge fractions as their stellar populations age and become enriched chemically. The age and stellar mass-to-light ratio gradients for low-mass galaxies in our sample tend to be positive (centre Spiral galaxies with large mass and size have the steepest gradients, while the most massive ETGs, especially above the critical mass Mcrit ≳ 2 × 1011 M⊙, where slow rotator ETGs start dominating, have much flatter gradients. This may be due to differences in their evolution histories, e.g. mergers.

Mass density slope of elliptical galaxies from strong lensing and resolved stellar kinematics

Science.gov (United States)

Lyskova, N.; Churazov, E.; Naab, T.

2018-04-01

We discuss constraints on the mass density distribution (parametrized as ρ ∝ r-γ) in early-type galaxies provided by strong lensing and stellar kinematics data. The constraints come from mass measurements at two `pinch' radii. One `pinch' radius r1 = 2.2REinst is defined such that the Einstein (i.e. aperture) mass can be converted into the spherical mass almost independently of the mass-model. Another `pinch' radius r2 = Ropt is chosen so that the dynamical mass, derived from the line-of-sight velocity dispersion, is least sensitive to the anisotropy of stellar orbits. We verified the performance of this approach on a sample of simulated elliptical galaxies and on a sample of 15 SLACS lens galaxies at 0.01 ≤ z ≤ 0.35, which have already been analysed in Barnabè et al. by the self-consistent joint lensing and kinematic code. For massive simulated galaxies, the density slope γ is recovered with an accuracy of ˜13 per cent, unless r1 and r2 happen to be close to each other. For SLACS galaxies, we found good overall agreement with the results of Barnabè et al. with a sample-averaged slope γ = 2.1 ± 0.05. Although the two-pinch-radii approach has larger statistical uncertainties, it is much simpler and uses only few arithmetic operations with directly observable quantities.

SDSS-IV MaNGA: Variation of the Stellar Initial Mass Function in Spiral and Early-type Galaxies

Science.gov (United States)

Li, Hongyu; Ge, Junqiang; Mao, Shude; Cappellari, Michele; Long, R. J.; Li, Ran; Emsellem, Eric; Dutton, Aaron A.; Li, Cheng; Bundy, Kevin; Thomas, Daniel; Drory, Niv; Lopes, Alexandre Roman

2017-04-01

We perform Jeans anisotropic modeling (JAM) on elliptical and spiral galaxies from the MaNGA DR13 sample. By comparing the stellar mass-to-light ratios estimated from stellar population synthesis and from JAM, we find a systematic variation of the initial mass function (IMF) similar to that in the earlier {{ATLAS}}3{{D}} results. Early-type galaxies (elliptical and lenticular) with lower velocity dispersions within one effective radius are consistent with a Chabrier-like IMF, while galaxies with higher velocity dispersions are consistent with a more bottom-heavy IMF such as the Salpeter IMF. Spiral galaxies have similar systematic IMF variations, but with slightly different slopes and larger scatters, due to the uncertainties caused by the higher gas fractions and extinctions for these galaxies. Furthermore, we examine the effects of stellar mass-to-light ratio gradients on our JAM modeling, and we find that the trends become stronger after considering the gradients.

Modeling Nearly Spherical Pure-bulge Galaxies with a Stellar Mass-to-light Ratio Gradient under the ΛCDM and MOND Paradigms. I. Methodology, Dynamical Stellar Mass, and Fundamental Mass Plane

Science.gov (United States)

Chae, Kyu-Hyun; Bernardi, Mariangela; Sheth, Ravi K.

2018-06-01

We carry out spherical Jeans modeling of nearly round pure-bulge galaxies selected from the ATLAS3D sample. Our modeling allows for gradients in the stellar mass-to-light ratio (M ⋆/L) through analytic prescriptions parameterized with a “gradient strength” K introduced to accommodate any viable gradient. We use a generalized Osipkov–Merritt model for the velocity dispersion (VD) anisotropy. We produce Monte Carlo sets of models based on the stellar VD profiles under both the ΛCDM and MOND paradigms. Here, we describe the galaxy data, the empirical inputs, and the modeling procedures of obtaining the Monte Carlo sets. We then present the projected dynamical stellar mass, {M}\\star {{e}}, within the effective radius R e, and the fundamental mass plane (FMP) as a function of K. We find the scaling of the K-dependent mass with respect to the ATLAS3D reported mass as: {log}}10[{M}\\star {{e}}(K)/{M}\\star {{e}}{{A}3{{D}}}]=a\\prime +b\\prime K with a‧ = ‑0.019 ± 0.012 and b‧ = ‑0.18 ± 0.02 (ΛCDM), or a‧ = ‑0.023 ± 0.014 and b‧ = ‑0.23 ± 0.03 (MOND), for 0 ≤ K expectation and only the zero-point scales with K. The median value of K for the ATLAS3D galaxies is ={0.53}-0.04+0.05. We perform a similar analysis of the much larger SDSS DR7 spectroscopic sample. In this case, only the VD within a single aperture is available, so we impose the additional requirement that the VD slope be similar to that in the ATLAS3D galaxies. Our analysis of the SDSS galaxies suggests a positive correlation of K with stellar mass.

Stellar Velocity Dispersion: Linking Quiescent Galaxies to Their Dark Matter Halos

Science.gov (United States)

Zahid, H. Jabran; Sohn, Jubee; Geller, Margaret J.

2018-06-01

We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This proportionality holds even when a line-of-sight aperture dispersion is calculated in analogy to observations. In contrast, at a given stellar velocity dispersion, the dark matter halo mass of satellite galaxies is smaller than virial equilibrium expectations. This deviation from virial equilibrium probably results from tidal stripping of the outer dark matter halo. Stellar velocity dispersion appears insensitive to tidal effects and thus reflects the correlation between stellar velocity dispersion and dark matter halo mass prior to infall. There is a tight relation (≲0.2 dex scatter) between line-of-sight aperture stellar velocity dispersion and dark matter halo mass suggesting that the dark matter halo mass may be estimated from the measured stellar velocity dispersion for both central and satellite galaxies. We evaluate the impact of treating all objects as central galaxies if the relation we derive is applied to a statistical ensemble. A large fraction (≳2/3) of massive quiescent galaxies are central galaxies and systematic uncertainty in the inferred dark matter halo mass is ≲0.1 dex thus simplifying application of the simulation results to currently available observations.

STELLAR MASSES OF LYMAN BREAK GALAXIES, Lyα EMITTERS, AND RADIO GALAXIES IN OVERDENSE REGIONS AT z = 4-6

International Nuclear Information System (INIS)

Overzier, Roderik A.; Shu Xinwen; Zheng Wei; Rettura, Alessandro; Zirm, Andrew; Ford, Holland; Bouwens, Rychard J.; Illingworth, Garth D.; Miley, George K.; Venemans, Bram; White, Richard L.

2009-01-01

We present new information on galaxies in the vicinity of luminous radio galaxies (RGs) and quasars at z≅4, 5, and 6. These fields were previously found to contain overdensities of Lyman Break Galaxies (LBGs) or spectroscopic Lyα emitters, which were interpreted as evidence for clusters-in-formation ('protoclusters'). We use Hubble Space Telescope and Spitzer data to infer stellar masses from stellar synthesis models calibrated against the Millennium Run simulations, and contrast our results with large samples of LBGs in more average environments as probed by the Great Observatories Origins Deep Survey (GOODS). The following results were obtained. First, LBGs in both overdense regions and in the field at z = 4-5 lie on a very similar sequence in a z'-[3.6] versus 3.6 μm color-magnitude diagram. This is interpreted as a sequence in stellar mass (M * ∼ 10 9 -10 11 M sun ) in which galaxies become increasingly red due to dust and age as their star formation rate (SFR) increases, while their specific SFR stays constant. Second, the two RGs are among the most massive objects (M * ∼ 10 11 M sun ) known to exist at z ≅ 4-5, and are extremely rare based on the low number density of such objects as estimated from the ∼25x larger area GOODS survey. We suggest that the presence of the massive (radio) galaxies and associated supermassive black holes has been boosted through rapid accretion of gas or merging inside overdense regions. Third, the total stellar mass found in the z = 4 protocluster TN1338 accounts for 4, based on a comparison with the massive X-ray cluster Cl1252 at z = 1.2. Although future near-infrared observations should determine whether any massive galaxies are currently being missed by our UV/Lyα selections, one possible explanation for this mass difference is that TN1338 evolves into a smaller cluster than Cl1252. This raises the interesting question of whether the most massive protocluster regions at z > 4 remain yet to be discovered.

NEW CONSTRAINTS ON THE EVOLUTION OF THE STELLAR-TO-DARK MATTER CONNECTION: A COMBINED ANALYSIS OF GALAXY-GALAXY LENSING, CLUSTERING, AND STELLAR MASS FUNCTIONS FROM z = 0.2 to z = 1

Energy Technology Data Exchange (ETDEWEB)

Leauthaud, Alexie [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Chiba 277-8582 (Japan); Tinker, Jeremy [Center for Cosmology and Particle Physics, Department of Physics, New York University, NY (United States); Bundy, Kevin; George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Behroozi, Peter S.; Wechsler, Risa H.; Busha, Michael T.; Schrabback, Tim [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, and SLAC National Accelerator Laboratory, Stanford, CA 94305 (United States); Massey, Richard [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason; Benson, Andrew [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kneib, Jean-Paul; Ilbert, Olivier; Le Fevre, Oliver [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 E. California Blvd. Pasadena, CA 91125 (United States); Cortes, Marina [Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Lilly, Simon [Institute of Astronomy, Department of Physics, ETH Zurich, CH-8093 (Switzerland); McCracken, Henry J. [Institut d' Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, 75014 Paris (France); Salvato, Mara, E-mail: asleauthaud@lbl.gov [SUPA, Institute for Astronomy, The University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); and others

2012-01-10

Using data from the COSMOS survey, we perform the first joint analysis of galaxy-galaxy weak lensing, galaxy spatial clustering, and galaxy number densities. Carefully accounting for sample variance and for scatter between stellar and halo mass, we model all three observables simultaneously using a novel and self-consistent theoretical framework. Our results provide strong constraints on the shape and redshift evolution of the stellar-to-halo mass relation (SHMR) from z = 0.2 to z = 1. At low stellar mass, we find that halo mass scales as M{sub h} {proportional_to}M{sup 0.46}{sub *} and that this scaling does not evolve significantly with redshift from z = 0.2 to z = 1. The slope of the SHMR rises sharply at M{sub *} > 5 Multiplication-Sign 10{sup 10} M{sub Sun} and as a consequence, the stellar mass of a central galaxy becomes a poor tracer of its parent halo mass. We show that the dark-to-stellar ratio, M{sub h} /M{sub *}, varies from low to high masses, reaching a minimum of M{sub h} /M{sub *} {approx} 27 at M{sub *} = 4.5 Multiplication-Sign 10{sup 10} M{sub Sun} and M{sub h} = 1.2 Multiplication-Sign 10{sup 12} M{sub Sun }. This minimum is important for models of galaxy formation because it marks the mass at which the accumulated stellar growth of the central galaxy has been the most efficient. We describe the SHMR at this minimum in terms of the 'pivot stellar mass', M{sup piv}{sub *}, the 'pivot halo mass', M{sup piv}{sub h}, and the 'pivot ratio', (M{sub h} /M{sub *}){sup piv}. Thanks to a homogeneous analysis of a single data set spanning a large redshift range, we report the first detection of mass downsizing trends for both M{sup piv}{sub h} and M{sup piv}{sub *}. The pivot stellar mass decreases from M{sup piv}{sub *} = 5.75 {+-} 0.13 Multiplication-Sign 10{sup 10} M{sub Sun} at z = 0.88 to M{sup piv}{sub *} = 3.55 {+-} 0.17 Multiplication-Sign 10{sup 10} M{sub Sun} at z = 0.37. Intriguingly, however, the corresponding

Evolution of Galaxy Luminosity and Stellar-Mass Functions since $z=1$ with the Dark Energy Survey Science Verification Data

Energy Technology Data Exchange (ETDEWEB)

Capozzi, D.; et al.

2017-07-27

We present the first study of the evolution of the galaxy luminosity and stellar-mass functions (GLF and GSMF) carried out by the Dark Energy Survey (DES). We describe the COMMODORE galaxy catalogue selected from Science Verification images. This catalogue is made of $\\sim 4\\times 10^{6}$ galaxies at $0galaxy catalogues and they enable us to study the evolution of GLF and GSMF at $0galaxies build up their masses over cosmic time. We find that both the ${\\it i}$-band galaxy luminosity and stellar mass functions are characterised by a double-Schechter shape at $z<0.2$. Both functions agree well with those based on spectroscopic redshifts. The DES GSMF agrees especially with those measured for the GAlaxy Mass Assembly and the PRism MUlti-object Survey out to $z\\sim1$. At $0.2stellar-mass densities respectively to be constant ($\\rho_{\\rm L}\\propto (1+z)^{-0.12\\pm0.11}$) and decreasing ($\\rho_{\\rm Mstar}\\propto (1+z)^{-0.5\\pm0.1}$) with $z$. This indicates that, while at higher redshift galaxies have less stellar mass, their luminosities do not change substantially because of their younger and brighter stellar populations. Finally, we also find evidence for a top-down mass-dependent evolution of the GSMF.

The Spitzer Survey of Stellar Structure in Galaxies (S4G): Precise Stellar Mass Distributions from Automated Dust Correction at 3.6 μm

Science.gov (United States)

Querejeta, Miguel; Meidt, Sharon E.; Schinnerer, Eva; Cisternas, Mauricio; Muñoz-Mateos, Juan Carlos; Sheth, Kartik; Knapen, Johan; van de Ven, Glenn; Norris, Mark A.; Peletier, Reynier; Laurikainen, Eija; Salo, Heikki; Holwerda, Benne W.; Athanassoula, E.; Bosma, Albert; Groves, Brent; Ho, Luis C.; Gadotti, Dimitri A.; Zaritsky, Dennis; Regan, Michael; Hinz, Joannah; Gil de Paz, Armando; Menendez-Delmestre, Karin; Seibert, Mark; Mizusawa, Trisha; Kim, Taehyun; Erroz-Ferrer, Santiago; Laine, Jarkko; Comerón, Sébastien

2015-07-01

The mid-infrared is an optimal window to trace stellar mass in nearby galaxies and the 3.6 μ {{m}} IRAC band has been exploited to this effect, but such mass estimates can be biased by dust emission. We present our pipeline to reveal the old stellar flux at 3.6 μm and obtain stellar mass maps for more than 1600 galaxies available from the Spitzer Survey of Stellar Structure in Galaxies (S4G). This survey consists of images in two infrared bands (3.6 and 4.5 μ {{m}}), and we use the Independent Component Analysis (ICA) method presented in Meidt et al. to separate the dominant light from old stars and the dust emission that can significantly contribute to the observed 3.6 μ {{m}} flux. We exclude from our ICA analysis galaxies with low signal-to-noise ratio ({{S}}/{{N}}\\lt 10) and those with original [3.6]-[4.5] colors compatible with an old stellar population, indicative of little dust emission (mostly early Hubble types, which can directly provide good mass maps). For the remaining 1251 galaxies to which ICA was successfully applied, we find that as much as 10%-30% of the total light at 3.6 μ {{m}} typically originates from dust, and locally it can reach even higher values. This contamination fraction shows a correlation with specific star formation rates, confirming that the dust emission that we detect is related to star formation. Additionally, we have used our large sample of mass estimates to calibrate a relationship of effective mass-to-light ratio (M/L) as a function of observed [3.6]-[4.5] color: {log}({\\text{}}M/L) = -0.339(+/- 0.057) × ([3.6]-[4.5])-0.336(+/- 0.002). Our final pipeline products have been made public through IRSA, providing the astronomical community with an unprecedentedly large set of stellar mass maps ready to use for scientific applications.

CONSTRAINTS ON THE RELATIONSHIP BETWEEN STELLAR MASS AND HALO MASS AT LOW AND HIGH REDSHIFT

International Nuclear Information System (INIS)

Moster, Benjamin P.; Somerville, Rachel S.; Maulbetsch, Christian; Van den Bosch, Frank C.; Maccio, Andrea V.; Naab, Thorsten; Oser, Ludwig

2010-01-01

We use a statistical approach to determine the relationship between the stellar masses of galaxies and the masses of the dark matter halos in which they reside. We obtain a parameterized stellar-to-halo mass (SHM) relation by populating halos and subhalos in an N-body simulation with galaxies and requiring that the observed stellar mass function be reproduced. We find good agreement with constraints from galaxy-galaxy lensing and predictions of semi-analytic models. Using this mapping, and the positions of the halos and subhalos obtained from the simulation, we find that our model predictions for the galaxy two-point correlation function (CF) as a function of stellar mass are in excellent agreement with the observed clustering properties in the Sloan Digital Sky Survey at z = 0. We show that the clustering data do not provide additional strong constraints on the SHM function and conclude that our model can therefore predict clustering as a function of stellar mass. We compute the conditional mass function, which yields the average number of galaxies with stellar masses in the range m ± dm/2 that reside in a halo of mass M. We study the redshift dependence of the SHM relation and show that, for low-mass halos, the SHM ratio is lower at higher redshift. The derived SHM relation is used to predict the stellar mass dependent galaxy CF and bias at high redshift. Our model predicts that not only are massive galaxies more biased than low-mass galaxies at all redshifts, but also the bias increases more rapidly with increasing redshift for massive galaxies than for low-mass ones. We present convenient fitting functions for the SHM relation as a function of redshift, the conditional mass function, and the bias as a function of stellar mass and redshift.

A PHYSICAL MODEL FOR THE 0 {approx}< z {approx}< 8 REDSHIFT EVOLUTION OF THE GALAXY ULTRAVIOLET LUMINOSITY AND STELLAR MASS FUNCTIONS

Energy Technology Data Exchange (ETDEWEB)

Tacchella, Sandro; Carollo, C. Marcella [Department of Physics, Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Trenti, Michele, E-mail: tasandro@phys.ethz.ch [Kavli Institute for Cosmology and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)

2013-05-10

We present a model to understand the redshift evolution of the UV luminosity and stellar mass functions of Lyman break galaxies. Our approach is based on the assumption that the luminosity and stellar mass of a galaxy is related to its dark-matter (DM) halo assembly and gas infall rate. Specifically, galaxies experience a burst of star formation at the halo assembly time, followed by a constant star formation rate, representing a secular star formation activity sustained by steady gas accretion. Star formation from steady gas accretion is the dominant contribution to the galaxy UV luminosity at all redshifts. The model is calibrated by constructing a galaxy luminosity versus halo mass relation at z = 4 via abundance matching. After this luminosity calibration, the model naturally fits the z = 4 stellar mass function, and correctly predicts the evolution of both luminosity and stellar mass functions from z = 0 to z = 8. While the details of star formation efficiency and feedback are hidden within our calibrated luminosity versus halo mass relation, our study highlights that the primary driver of galaxy evolution across cosmic time is the buildup of DM halos, without the need to invoke a redshift-dependent efficiency in converting gas into stars.

The COSMOS2015 galaxy stellar mass function . Thirteen billion years of stellar mass assembly in ten snapshots

Science.gov (United States)

Davidzon, I.; Ilbert, O.; Laigle, C.; Coupon, J.; McCracken, H. J.; Delvecchio, I.; Masters, D.; Capak, P.; Hsieh, B. C.; Le Fèvre, O.; Tresse, L.; Bethermin, M.; Chang, Y.-Y.; Faisst, A. L.; Le Floc'h, E.; Steinhardt, C.; Toft, S.; Aussel, H.; Dubois, C.; Hasinger, G.; Salvato, M.; Sanders, D. B.; Scoville, N.; Silverman, J. D.

2017-09-01

We measure the stellar mass function (SMF) and stellar mass density of galaxies in the COSMOS field up to z 6. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper Suprime-Cam. At z> 2.5 we use new precise photometric redshifts with error σz = 0.03(1 + z) and an outlier fraction of 12%, estimated by means of the unique spectroscopic sample of COSMOS ( 100 000 spectroscopic measurements in total, more than one thousand having robust zspec> 2.5). The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the completeness at high z with respect to previous UltraVISTA catalogues (e.g. our sample is >75% complete at 1010 ℳ⊙ and z = 5). We also identify passive galaxies through a robust colour-colour selection, extending their SMF estimate up to z = 4. Our work provides a comprehensive view of galaxy-stellar-mass assembly between z = 0.1 and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from ΛCDM simulations, finding that at z> 3 both functions decline with a similar slope in thehigh-mass end. This feature could be explained assuming that mechanisms quenching star formation in massive haloes become less effective at high redshifts; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as it moves towards higher redshifts, with α decreasing from -1.47+0.02-0.02 at z ≃ 0.1 to -2.11+0.30-0.13 at z ≃ 5. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in different best

Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation Rate

Science.gov (United States)

Ly, Chun; Rigby, Jane R.; Cooper, Michael; Yan, Renbin

2015-01-01

We report on the discovery of 28 redshift (z) approximately equal to 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFR with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 dex above the redshift (z) approximately 1 stellar mass-SFR relation and 0.23 plus or minus 0.23 dex below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 dex, but significant dispersion remains dex with 0.16 dex due to measurement uncertainties). This dispersion suggests that gas accretion, star formation, and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately equal to 100 (sup plus 310) (sub minus 75) million years which suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 94.4 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas but has not had time to drive the metal-enriched gas out with feedback mechanisms.

Relations between stellar mass and electron temperature-based metallicity for star-forming galaxies in a wide mass range

International Nuclear Information System (INIS)

Shi Wei-Bin; Zhao Gang; Ruan Gui-Ping; Zhou Li; Liang Yan-Chun; Shao Xu; Liu Xiao-Wei; Hammer Francois; Flores Hector; Zhang Yong

2014-01-01

We select 947 star-forming galaxies from SDSS-DR7 with [O III]λ4363 emission lines detected at a signal-to-noise ratio larger than 5σ. Their electron temperatures and direct oxygen abundances are then determined. We compare the results from different methods. t 2 , the electron temperature in the low ionization region, estimated from t 3 , that in the high ionization region, is compared using three analysis relations between t 2 – t 3 . These show obvious differences, which result in some different ionic oxygen abundances. The results of t 3 , t 2 , O ++ /H + and O + /H + derived by using methods from IRAF and literature are also compared. The ionic abundances O ++ /H + are higher than O + /H + for most cases. The different oxygen abundances derived from T e and the strong-line ratios show a clear discrepancy, which is more obvious following increasing stellar mass and strong-line ratio R 23 . The sample of galaxies from SDSS with detected [O III]λ4363 have lower metallicites and higher star formation rates, so they may not be typical representatives of the whole population of galaxies. Adopting data objects from Andrews and Martini, Liang et al. and Lee et al. data, we derive new relations of stellar mass and metallicity for star-forming galaxies in a much wider stellar mass range: from 10 6 M ⊙ to 10 11 M ⊙ . (research papers)

The Spectroscopy and H-band Imaging of Virgo Cluster Galaxies (SHIVir) Survey: Scaling Relations and the Stellar-to-total Mass Relation

Energy Technology Data Exchange (ETDEWEB)

Ouellette, Nathalie N.-Q.; Courteau, Stéphane [Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, ON K7L 3N6 (Canada); Holtzman, Jon A. [Department of Physics and Astronomy, New Mexico State University, Las Cruces, NM, 88003-8001 (United States); Dutton, Aaron A. [Department of Physics, New York University Abu Dhabi, Abu Dhabi (United Arab Emirates); Cappellari, Michele [Sub-department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Seattle, WA, 98195 (United States); McDonald, Michael [MIT Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA, 02139 (United States); Roediger, Joel C.; Côté, Patrick; Ferrarese, Laura [Herzberg Institute of Astrophysics, National Research Council, Victoria, BC, V9E 2E7 (Canada); Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1 (Canada); Tully, R. Brent [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822-1839 (United States); Peng, Eric W. [Department of Astronomy, Peking University, Beijing 100871 (China)

2017-07-01

We present parameter distributions and fundamental scaling relations for 190 Virgo cluster galaxies in the SHIVir survey. The distribution of galaxy velocities is bimodal about V {sub circ} ∼ 125 km s{sup −1}, hinting at the existence of dynamically unstable modes in the inner regions of galaxies. An analysis of the Tully-Fisher relation (TFR) of late-type galaxies (LTGs) and the fundamental plane (FP) of early-type galaxies (ETGs) is presented, yielding a compendium of galaxy scaling relations. The slope and zero-point of the Virgo TFR match those of field galaxies, while scatter differences likely reflect distinct evolutionary histories. The velocities minimizing scatter for the TFR and FP are measured at large apertures where the baryonic fraction becomes subdominant. While TFR residuals remain independent of any galaxy parameters, FP residuals (i.e., the FP “tilt”) correlate strongly with the dynamical-to-stellar mass ratio, yielding stringent galaxy formation constraints. We construct a stellar-to-total mass relation (STMR) for ETGs and LTGs and find linear but distinct trends over the range M {sub *} = 10{sup 8–11} M {sub ⊙}. Stellar-to-halo mass relations (SHMRs), which probe the extended dark matter halo, can be scaled down to masses estimated within the optical radius, showing a tight match with the Virgo STMR at low masses; possibly inadequate halo abundance matching prescriptions and broad radial scalings complicate this comparison at all masses. While ETGs appear to be more compact than LTGs of the same stellar mass in projected space, their mass-size relations in physical space are identical. The trends reported here may soon be validated through well-resolved numerical simulations.

THE XMM CLUSTER SURVEY: THE BUILD-UP OF STELLAR MASS IN BRIGHTEST CLUSTER GALAXIES AT HIGH REDSHIFT

International Nuclear Information System (INIS)

Stott, J. P.; Collins, C. A.; Hilton, M.; Capozzi, D.; Sahlen, M.; Lloyd-Davies, E.; Hosmer, M.; Liddle, A. R.; Mehrtens, N.; Romer, A. K.; Miller, C. J.; Stanford, S. A.; Viana, P. T. P.; Davidson, M.; Hoyle, B.; Kay, S. T.; Nichol, R. C.

2010-01-01

We present deep J- and K s -band photometry of 20 high redshift galaxy clusters between z = 0.8 and1.5, 19 of which are observed with the MOIRCS instrument on the Subaru telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at ∼9 x 10 11 M sun since z ∼ 1.5. We investigate the effect on this result of differing star formation histories generated by three well-known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar mass of BCGs over the last 9-10 Gyr in stark contrast to the predictions of semi-analytic models, based on the hierarchical merging of dark matter halos, which predict a more protracted mass build-up over a Hubble time. However, we discuss that there is potential for reconciliation between observation and theory if there is a significant growth of material in the intracluster light over the same period.

THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ≤ z ≤ 6.5 IN CANDELS

International Nuclear Information System (INIS)

Salmon, Brett; Papovich, Casey; Tilvi, Vithal; Finkelstein, Steven L.; Finlator, Kristian; Behroozi, Peter; Lu, Yu; Wechsler, Risa H.; Dahlen, Tomas; Ferguson, Henry C.; Davé, Romeel; Dekel, Avishai; Dickinson, Mark; Giavalisco, Mauro; Long, James; Mobasher, Bahram; Reddy, Naveen; Somerville, Rachel S.

2015-01-01

Distant star-forming galaxies show a correlation between their star formation rates (SFRs) and stellar masses, and this has deep implications for galaxy formation. Here, we present a study on the evolution of the slope and scatter of the SFR-stellar mass relation for galaxies at 3.5 ≤ z ≤ 6.5 using multi-wavelength photometry in GOODS-S from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and Spitzer Extended Deep Survey. We describe an updated, Bayesian spectral-energy distribution fitting method that incorporates effects of nebular line emission, star formation histories that are constant or rising with time, and different dust-attenuation prescriptions (starburst and Small Magellanic Cloud). From z = 6.5 to z = 3.5 star-forming galaxies in CANDELS follow a nearly unevolving correlation between stellar mass and SFR that follows SFR ∼ M ⋆ a with a =0.54 ± 0.16 at z ∼ 6 and 0.70 ± 0.21 at z ∼ 4. This evolution requires a star formation history that increases with decreasing redshift (on average, the SFRs of individual galaxies rise with time). The observed scatter in the SFR-stellar mass relation is tight, σ(log SFR/M ☉ yr –1 ) < 0.3-0.4 dex, for galaxies with log M * /M ☉ > 9 dex. Assuming that the SFR is tied to the net gas inflow rate (SFR ∼ M-dot gas ), then the scatter in the gas inflow rate is also smaller than 0.3–0.4 dex for star-forming galaxies in these stellar mass and redshift ranges, at least when averaged over the timescale of star formation. We further show that the implied star formation history of objects selected on the basis of their co-moving number densities is consistent with the evolution in the SFR-stellar mass relation

Stellar Velocity Dispersion: Linking Quiescent Galaxies to their Dark Matter Halos

OpenAIRE

Zahid, H. Jabran; Sohn, Jubee; Geller, Margaret J.

2018-01-01

We analyze the Illustris-1 hydrodynamical cosmological simulation to explore the stellar velocity dispersion of quiescent galaxies as an observational probe of dark matter halo velocity dispersion and mass. Stellar velocity dispersion is proportional to dark matter halo velocity dispersion for both central and satellite galaxies. The dark matter halos of central galaxies are in virial equilibrium and thus the stellar velocity dispersion is also proportional to dark matter halo mass. This prop...

Galaxy And Mass Assembly (GAMA): the galaxy stellar mass function to z = 0.1 from the r-band selected equatorial regions

Science.gov (United States)

Wright, A. H.; Robotham, A. S. G.; Driver, S. P.; Alpaslan, M.; Andrews, S. K.; Baldry, I. K.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Colless, M.; da Cunha, E.; Davies, L. J. M.; Graham, Alister W.; Holwerda, B. W.; Hopkins, A. M.; Kafle, P. R.; Kelvin, L. S.; Loveday, J.; Maddox, S. J.; Meyer, M. J.; Moffett, A. J.; Norberg, P.; Phillipps, S.; Rowlands, K.; Taylor, E. N.; Wang, L.; Wilkins, S. M.

2017-09-01

We derive the low-redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) data set covering 180 deg2. We construct the mass function using a density-corrected maximum volume method, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane (M⋆-μ), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 107.5 M⊙. The galaxy distribution in the M-μ plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is fitted with a double Schechter function, with M^\\star =10^{10.78± 0.01± 0.20} M_{⊙}, φ ^\\star _1=(2.93± 0.40)× 10^{-3} h_{70}^3 Mpc-3, α1 = -0.62 ± 0.03 ± 0.15, φ ^\\star _2=(0.63± 0.10)× 10^{-3} h_{70}^3 Mpc-3 and α2 = -1.50 ± 0.01 ± 0.15. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value of M^\\star. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as 107.5 M⊙, and assess limits to 106.5 M⊙. Combining GAMA-II with data from G10-COSMOS, we are able to comment qualitatively on the shape of the GSMF down to masses as low as 106 M⊙. Beyond the well-known upturn seen in the GSMF at 109.5, the distribution appears to maintain a single power-law slope from 109 to 106.5. We calculate the stellar mass density parameter given our best-estimate GSMF, finding Ω _\\star = 1.66^{+0.24}_{-0.23}± 0.97 h^{-1}_{70} × 10^{-3}, inclusive of random and systematic uncertainties.

The hELENa project - I. Stellar populations of early-type galaxies linked with local environment and galaxy mass

OpenAIRE

Sybilska, A.; Lisker, T.; Kuntschner, H.; Vazdekis, A.; van de Ven, G.; Peletier, R.; Falcón-Barroso, J.; Vijayaraghavan, R.; Janz, J.

2017-01-01

We present the first in a series of papers in T$h$e role of $E$nvironment in shaping $L$ow-mass $E$arly-type $N$earby g$a$laxies (hELENa) project. In this paper we combine our sample of 20 low-mass early types (dEs) with 258 massive early types (ETGs) from the ATLAS$^{\\mathrm{3D}}$ survey - all observed with the SAURON integral field unit (IFU) - to investigate early-type galaxies' stellar population scaling relations and the dependence of the population properties on local environment, exten...

The stellar metallicity gradients in galaxy discs in a cosmological scenario

Science.gov (United States)

Tissera, Patricia B.; Machado, Rubens E. G.; Sanchez-Blazquez, Patricia; Pedrosa, Susana E.; Sánchez, Sebastián F.; Snaith, Owain; Vilchez, Jose

2016-08-01

Context. The stellar metallicity gradients of disc galaxies provide information on disc assembly, star formation processes, and chemical evolution. They also might store information on dynamical processes that could affect the distribution of chemical elements in the gas phase and the stellar components. Understanding their joint effects within a hierarchical clustering scenario is of paramount importance. Aims: We studied the stellar metallicity gradients of simulated discs in a cosmological simulation. We explored the dependence of the stellar metallicity gradients on stellar age and on the size and mass of the stellar discs. Methods: We used a catalogue of galaxies with disc components selected from a cosmological hydrodynamical simulation performed including a physically motivated supernova feedback and chemical evolution. Disc components were defined based on angular momentum and binding energy criteria. The metallicity profiles were estimated for stars with different ages. We confront our numerical findings with results from the Calar Alto Legacy Integral Field Area (CALIFA) Survey. Results: The simulated stellar discs are found to have metallicity profiles with slopes in global agreement with observations. Low stellar mass galaxies tend to have a larger variety of metallicity slopes. When normalized by the half-mass radius, the stellar metallicity gradients do not show any dependence and the dispersion increases significantly, regardless of the galaxy mass. Galaxies with stellar masses o f around 1010M⊙ show steeper negative metallicity gradients. The stellar metallicity gradients correlate with the half-mass radius. However, the correlation signal is not present when they are normalized by the half-mass radius. Stellar discs with positive age gradients are detected to have negative and positive metallicity gradients, depending on the relative importance of recent star formation activity in the central regions. Conclusions: Our results suggest that inside

The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies

OpenAIRE

Kirby, Evan N.; Cohen, Judith G.; Guhathakurta, Puragra; Cheng, Lucy; Bullock, James S.; Gallazzi, Anna

2013-01-01

We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same massmetallicity relation as the dwarf spheroidal (dSph) satellites of both the Milky Way and M31: Z * σ M * 0.30±0. 02 . The uniformity of the relation is in contradiction to previous estimates of metallicity based on photometry. This relationship is roughly continuous with the stellar massstellar metallicity relation for galaxies as massive asM*...

A relation between the characteristic stellar ages of galaxies and their intrinsic shapes

Science.gov (United States)

van de Sande, Jesse; Scott, Nicholas; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Cortese, Luca; Croom, Scott M.; d'Eugenio, Francesco; Foster, Caroline; Goodwin, Michael; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; McDermid, Richard M.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel N.; Sharp, Rob

2018-04-01

Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum1-3. A galaxy's mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy's mass was assembled. Resolved stellar dynamics4 trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions5. With the rise of large multi-object integral field spectroscopic surveys, such as SAMI6 and MaNGA7, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8), CALIFA9, MASSIVE10), it is now feasible to connect a galaxy's star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment4,11,12. Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ, ɛe) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.

A relation between the characteristic stellar ages of galaxies and their intrinsic shapes

Science.gov (United States)

van de Sande, Jesse; Scott, Nicholas; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Cortese, Luca; Croom, Scott M.; d'Eugenio, Francesco; Foster, Caroline; Goodwin, Michael; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; McDermid, Richard M.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel N.; Sharp, Rob

2018-06-01

Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum1-3. A galaxy's mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy's mass was assembled. Resolved stellar dynamics4 trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions5. With the rise of large multi-object integral field spectroscopic surveys, such as SAMI6 and MaNGA7, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8), CALIFA9, MASSIVE10), it is now feasible to connect a galaxy's star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment4,11,12. Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ, ɛe) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.

STELLAR MASSES AND STAR FORMATION RATES OF LENSED, DUSTY, STAR-FORMING GALAXIES FROM THE SPT SURVEY

Energy Technology Data Exchange (ETDEWEB)

Ma, Jingzhe; Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Spilker, J. S.; Marrone, D. P. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Strandet, M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69 D-53121 Bonn (Germany); Ashby, M. L. N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Aravena, M. [Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago (Chile); Béthermin, M.; Breuck, C. de; Gullberg, B. [European Southern Observatory, Karl Schwarzschild Straße 2, D-85748 Garching (Germany); Bothwell, M. S. [Cavendish Laboratory, University of Cambridge, JJ Thompson Avenue, Cambridge CB3 0HA (United Kingdom); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Chapman, S. C. [Dalhousie University, Halifax, Nova Scotia (Canada); Fassnacht, C. D. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Hezaveh, Y. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Malkan, M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Saliwanchik, B. R., E-mail: jingzhema@ufl.edu [Department of Physics, Case Western Reserve University, Cleveland, OH 44106 (United States); and others

2015-10-10

To understand cosmic mass assembly in the universe at early epochs, we primarily rely on measurements of the stellar masses and star formation rates (SFRs) of distant galaxies. In this paper, we present stellar masses and SFRs of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from Atacama Large Millimeter/submillimeter Array observations. We have conducted follow-up observations to obtain multi-wavelength imaging data using the Hubble Space Telescope (HST), Spitzer, Herschel, and the Atacama Pathfinder EXperiment. We use the high-resolution HST/Wide Field Camera 3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and SFRs. The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ∼5 ×10{sup 10} M{sub ⊙}. The intrinsic IR luminosities range from 4 × 10{sup 12} L{sub ⊙} to 4 × 10{sup 13} L{sub ⊙}. They all have prodigious intrinsic SFRs of 510–4800 M{sub ⊙} yr{sup −1}. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing ongoing strong starburst events that may be driven by major mergers.

Dark matter contraction and stellar-mass-to-light ratio gradients in massive early-type galaxies

Science.gov (United States)

Oldham, Lindsay J.; Auger, Matthew W.

2018-05-01

We present models for the dark and luminous mass structure of 12 strong lensing early-type galaxies. We combine pixel-based modelling of multiband Hubble Space Telescope imaging with Jeans modelling of kinematics obtained from Keck/ESI spectra to disentangle the dark and luminous contributions to the mass. Assuming a generalised NFW (gNFW) profile for the dark matter halo and a spatially constant stellar-mass-to-light ratio ϒ⋆ for the baryonic mass, we infer distributions for ϒ⋆ consistent with initial mass functions (IMFs) that are heavier than the Milky Way's (with a global mean mismatch parameter relative to a Chabrier IMF μαc = 1.80 ± 0.14) and halo inner density slopes that span a large range but are generally cuspier than the dark-matter-only prediction (μ _{γ ^' }} = 2.01_{-0.22}^{+0.19}). We investigate possible reasons for overestimating the halo slope, including the neglect of spatially varying stellar-mass-to-light ratios and/or stellar orbital anisotropy, and find that a quarter of the systems prefer radially declining stellar-mass-to-light ratio gradients, but that the overall effect on our inference on the halo slope is small. We suggest a coherent explanation of these results in the context of inside-out galaxy growth, and that the relative importance of different baryonic processes in shaping the dark halo may depend on halo environment.

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

Science.gov (United States)

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

2012-04-01

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

Multiple populations within globular clusters in Early-type galaxies Exploring their effect on stellar initial mass function estimates

Science.gov (United States)

Chantereau, W.; Usher, C.; Bastian, N.

2018-05-01

It is now well-established that most (if not all) ancient globular clusters host multiple populations, that are characterised by distinct chemical features such as helium abundance variations along with N-C and Na-O anti-correlations, at fixed [Fe/H]. These very distinct chemical features are similar to what is found in the centres of the massive early-type galaxies and may influence measurements of the global properties of the galaxies. Additionally, recent results have suggested that M/L variations found in the centres of massive early-type galaxies might be due to a bottom-heavy stellar initial mass function. We present an analysis of the effects of globular cluster-like multiple populations on the integrated properties of early-type galaxies. In particular, we focus on spectral features in the integrated optical spectrum and the global mass-to-light ratio that have been used to infer variations in the stellar initial mass function. To achieve this we develop appropriate stellar population synthesis models and take into account, for the first time, an initial-final mass relation which takes into consideration a varying He abundance. We conclude that while the multiple populations may be present in massive early-type galaxies, they are likely not responsible for the observed variations in the mass-to-light ratio and IMF sensitive line strengths. Finally, we estimate the fraction of stars with multiple populations chemistry that come from disrupted globular clusters within massive ellipticals and find that they may explain some of the observed chemical patterns in the centres of these galaxies.

THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ≤ z ≤ 6.5 IN CANDELS

Energy Technology Data Exchange (ETDEWEB)

Salmon, Brett; Papovich, Casey; Tilvi, Vithal [George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy Texas A and M University, College Station, TX 77843 (United States); Finkelstein, Steven L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Finlator, Kristian [DARK fellow, Dark Cosmology Centre, Niels Bohr Institute, Copenhagen University, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark); Behroozi, Peter; Lu, Yu; Wechsler, Risa H. [Physics Department, Stanford University, Particle Astrophysics, SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology Stanford, CA 94305 (United States); Dahlen, Tomas; Ferguson, Henry C. [Space Telescope Science Institute, Baltimore, MD (United States); Davé, Romeel [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Dekel, Avishai [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Dickinson, Mark [National Optical Astronomy Observatories, Tucson, AZ (United States); Giavalisco, Mauro [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Long, James [Department of Statistics, Texas A and M University, College Station, TX 77843-3143 (United States); Mobasher, Bahram; Reddy, Naveen [Department of Physics and Astronomy, University of California, Riverside, 900 University Avenue, Riverside, CA 92521 (United States); Somerville, Rachel S., E-mail: bsalmon@physics.tamu.edu [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)

2015-02-01

Distant star-forming galaxies show a correlation between their star formation rates (SFRs) and stellar masses, and this has deep implications for galaxy formation. Here, we present a study on the evolution of the slope and scatter of the SFR-stellar mass relation for galaxies at 3.5 ≤ z ≤ 6.5 using multi-wavelength photometry in GOODS-S from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and Spitzer Extended Deep Survey. We describe an updated, Bayesian spectral-energy distribution fitting method that incorporates effects of nebular line emission, star formation histories that are constant or rising with time, and different dust-attenuation prescriptions (starburst and Small Magellanic Cloud). From z = 6.5 to z = 3.5 star-forming galaxies in CANDELS follow a nearly unevolving correlation between stellar mass and SFR that follows SFR ∼ M{sub ⋆}{sup a} with a =0.54 ± 0.16 at z ∼ 6 and 0.70 ± 0.21 at z ∼ 4. This evolution requires a star formation history that increases with decreasing redshift (on average, the SFRs of individual galaxies rise with time). The observed scatter in the SFR-stellar mass relation is tight, σ(log SFR/M {sub ☉} yr{sup –1}) < 0.3-0.4 dex, for galaxies with log M {sub *}/M {sub ☉} > 9 dex. Assuming that the SFR is tied to the net gas inflow rate (SFR ∼ M-dot {sub gas}), then the scatter in the gas inflow rate is also smaller than 0.3–0.4 dex for star-forming galaxies in these stellar mass and redshift ranges, at least when averaged over the timescale of star formation. We further show that the implied star formation history of objects selected on the basis of their co-moving number densities is consistent with the evolution in the SFR-stellar mass relation.

Comparing Dark Energy Survey and HST –CLASH observations of the galaxy cluster RXC J2248.7-4431: implications for stellar mass versus dark matter

Energy Technology Data Exchange (ETDEWEB)

Palmese, A.; Lahav, O.; Banerji, M.; Gruen, D.; Jouvel, S.; Melchior, P.; Aleksić, J.; Annis, J.; Diehl, H. T.; Hartley, W. G.; Jeltema, T.; Romer, A. K.; Rozo, E.; Rykoff, E. S.; Seitz, S.; Suchyta, E.; Zhang, Y.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Crocce, M.; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Dietrich, J. P.; Doel, P.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Li, T. S.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Miller, C. J.; Miquel, R.; Nord, B.; Ogando, R.; Plazas, A. A.; Roodman, A.; Sanchez, E.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D.; Vikram, V.

2016-08-20

We derive the stellar mass fraction in the galaxy cluster RXC J2248.7-4431 observed with the Dark Energy Survey (DES) during the Science Verification period. We compare the stellar mass results from DES (five filters) with those from the Hubble Space Telescope Cluster Lensing And Supernova Survey (CLASH; 17 filters). When the cluster spectroscopic redshift is assumed, we show that stellar masses from DES can be estimated within 25 per cent of CLASH values. We compute the stellar mass contribution coming from red and blue galaxies, and study the relation between stellar mass and the underlying dark matter using weak lensing studies with DES and CLASH. An analysis of the radial profiles of the DES total and stellar mass yields a stellar-to-total fraction of f(star) = (6.8 +/- 1.7) x 10(-3) within a radius of r(200c) similar or equal to 2 Mpc. Our analysis also includes a comparison of photometric redshifts and star/galaxy separation efficiency for both data sets. We conclude that space-based small field imaging can be used to calibrate the galaxy properties in DES for the much wider field of view. The technique developed to derive the stellar mass fraction in galaxy clusters can be applied to the similar to 100 000 clusters that will be observed within this survey and yield important information about galaxy evolution.

Strong bimodality in the host halo mass of central galaxies from galaxy-galaxy lensing

Science.gov (United States)

Mandelbaum, Rachel; Wang, Wenting; Zu, Ying; White, Simon; Henriques, Bruno; More, Surhud

2016-04-01

We use galaxy-galaxy lensing to study the dark matter haloes surrounding a sample of locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey. We measure mean halo mass as a function of the stellar mass and colour of the central galaxy. Mock catalogues constructed from semi-analytic galaxy formation simulations demonstrate that most LBGs are the central objects of their haloes, greatly reducing interpretation uncertainties due to satellite contributions to the lensing signal. Over the full stellar mass range, 10.3 10.7. Tests using the mock catalogues and on the data themselves clarify the effects of LBG selection and show that it cannot artificially induce a systematic dependence of halo mass on LBG colour. The bimodality in halo mass at fixed stellar mass is reproduced by the astrophysical model underlying our mock catalogue, but the sign of the effect is inconsistent with recent, nearly parameter-free age-matching models. The sign and magnitude of the effect can, however, be reproduced by halo occupation distribution models with a simple (few-parameter) prescription for type dependence.

SMOOTH(ER) STELLAR MASS MAPS IN CANDELS: CONSTRAINTS ON THE LONGEVITY OF CLUMPS IN HIGH-REDSHIFT STAR-FORMING GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Wuyts, Stijn; Foerster Schreiber, Natascha M.; Genzel, Reinhard; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, Giessenbachstr., D-85741 Garching (Germany); Guo Yicheng; Giavalisco, Mauro [Astronomy Department, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Barro, Guillermo; Faber, Sandra M.; Kocevski, Dale D.; Koo, David C.; McGrath, Elizabeth [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Dekel, Avishai [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M.; Lotz, Jennifer [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hathi, Nimish P. [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States); Huang, Kuang-Han [Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Newman, Jeffrey A. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); and others

2012-07-10

We perform a detailed analysis of the resolved colors and stellar populations of a complete sample of 323 star-forming galaxies (SFGs) at 0.5 < z < 1.5 and 326 SFGs at 1.5 < z < 2.5 in the ERS and CANDELS-Deep region of GOODS-South. Galaxies were selected to be more massive than 10{sup 10} M{sub Sun} and have specific star formation rates (SFRs) above 1/t{sub H} . We model the seven-band optical ACS + near-IR WFC3 spectral energy distributions of individual bins of pixels, accounting simultaneously for the galaxy-integrated photometric constraints available over a longer wavelength range. We analyze variations in rest-frame color, stellar surface mass density, age, and extinction as a function of galactocentric radius and local surface brightness/density, and measure structural parameters on luminosity and stellar mass maps. We find evidence for redder colors, older stellar ages, and increased dust extinction in the nuclei of galaxies. Big star-forming clumps seen in star formation tracers are less prominent or even invisible in the inferred stellar mass distributions. Off-center clumps contribute up to {approx}20% to the integrated SFR, but only 7% or less to the integrated mass of all massive SFGs at z {approx} 1 and z {approx} 2, with the fractional contributions being a decreasing function of wavelength used to select the clumps. The stellar mass profiles tend to have smaller sizes and M20 coefficients, and higher concentration and Gini coefficients than the light distribution. Our results are consistent with an inside-out disk growth scenario with brief (100-200 Myr) episodic local enhancements in star formation superposed on the underlying disk. Alternatively, the young ages of off-center clumps may signal inward clump migration, provided this happens efficiently on the order of an orbital timescale.

The Role Of Environment In Stellar Mass Growth

Science.gov (United States)

Thomas, Daniel

2017-06-01

In this talk I give a brief summary of methods to measure galaxy environment. I then discuss the dependence of stellar population properties on environmental density: it turns out that the latter are driven by galaxy mass, and galaxy environment only plays a secondary role, mostly at late times in low-mass galaxies. I show that this evidence has now been extended to stellar population gradients using the IFU survey SDSS/MaNGA that again turn out to be independent of environment, including central-satellite classification. Finally I present results from the DES, where the dependence of the stellar mass function with redshift and environmental density is explored. It is found that the fraction of massive galaxies is larger in high density environments than in low density environments. The low density and high density components converge with increasing redshift up to z 1.0 where the shapes of the mass function components are indistinguishable. This study shows how high density structures build up around massive galaxies through cosmic time, which sets new valuable constraints on galaxy formation models.

RESOLVE AND ECO: THE HALO MASS-DEPENDENT SHAPE OF GALAXY STELLAR AND BARYONIC MASS FUNCTIONS

Energy Technology Data Exchange (ETDEWEB)

Eckert, Kathleen D.; Kannappan, Sheila J.; Stark, David V.; Moffett, Amanda J.; Norris, Mark A. [Department of Physics and Astronomy, University of North Carolina, 141 Chapman Hall CB 3255, Chapel Hill, NC 27599 (United States); Berlind, Andreas A., E-mail: keckert@physics.unc.edu [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

2016-06-20

In this work, we present galaxy stellar and baryonic (stars plus cold gas) mass functions (SMF and BMF) and their halo mass dependence for two volume-limited data sets. The first, RESOLVE-B, coincides with the Stripe 82 footprint and is extremely complete down to baryonic mass M {sub bary} ∼ 10{sup 9.1} M {sub ⊙}, probing the gas-rich dwarf regime below M {sub bary} ∼ 10{sup 10} M {sub ⊙}. The second, ECO, covers a ∼40× larger volume (containing RESOLVE-A) and is complete to M {sub bary} ∼ 10{sup 9.4} M {sub ⊙}. To construct the SMF and BMF we implement a new “cross-bin sampling” technique with Monte Carlo sampling from the full likelihood distributions of stellar or baryonic mass. Our SMFs exhibit the “plateau” feature starting below M {sub star} ∼ 10{sup 10} M {sub ⊙} that has been described in prior work. However, the BMF fills in this feature and rises as a straight power law below ∼10{sup 10} M {sub ⊙}, as gas-dominated galaxies become the majority of the population. Nonetheless, the low-mass slope of the BMF is not as steep as that of the theoretical dark matter halo MF. Moreover, we assign group halo masses by abundance matching, finding that the SMF and BMF, separated into four physically motivated halo mass regimes, reveal complex structure underlying the simple shape of the overall MFs. In particular, the satellite MFs are depressed below the central galaxy MF “humps” in groups with mass <10{sup 13.5} M {sub ⊙} yet rise steeply in clusters. Our results suggest that satellite destruction and stripping are active from the point of nascent group formation. We show that the key role of groups in shaping MFs enables reconstruction of a given survey’s SMF or BMF based on its group halo mass distribution.

SDSS-IV MaNGA: stellar population gradients as a function of galaxy environment

Science.gov (United States)

Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo-Fernández, M.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Storchi-Bergmann, T.

2017-02-01

We study the internal radial gradients of stellar population properties within 1.5 Re and analyse the impact of galaxy environment. We use a representative sample of 721 galaxies with masses ranging between 109 M⊙ and 1011.5 M⊙ from the SDSS-IV survey MaNGA. We split this sample by morphology into early-type and late-type galaxies. Using the full spectral fitting code FIREFLY, we derive the light and mass-weighted stellar population properties, age and metallicity, and calculate the gradients of these properties. We use three independent methods to quantify galaxy environment, namely the Nth nearest neighbour, the tidal strength parameter Q and distinguish between central and satellite galaxies. In our analysis, we find that early-type galaxies generally exhibit shallow light-weighted age gradients in agreement with the literature and mass-weighted median age gradients tend to be slightly positive. Late-type galaxies, instead, have negative light-weighted age gradients. We detect negative metallicity gradients in both early- and late-type galaxies that correlate with galaxy mass, with the gradients being steeper and the correlation with mass being stronger in late-types. We find, however, that stellar population gradients, for both morphological classifications, have no significant correlation with galaxy environment for all three characterizations of environment. Our results suggest that galaxy mass is the main driver of stellar population gradients in both early and late-type galaxies, and any environmental dependence, if present at all, must be very subtle.

A comparison of LBGs, DRGs, and BzK galaxies: their contribution to the stellar mass density in the GOODS-MUSIC sample

Science.gov (United States)

Grazian, A.; Salimbeni, S.; Pentericci, L.; Fontana, A.; Nonino, M.; Vanzella, E.; Cristiani, S.; de Santis, C.; Gallozzi, S.; Giallongo, E.; Santini, P.

2007-04-01

Context: The classification scheme for high redshift galaxies is complex at the present time, with simple colour-selection criteria (i.e. EROs, IEROs, LBGs, DRGs, BzKs), resulting in ill-defined properties for the stellar mass and star formation rate of these distant galaxies. Aims: The goal of this work is to investigate the properties of different classes of high-z galaxies, focusing in particular on the stellar masses of LBGs, DRGs, and BzKs, in order to derive their contribution to the total mass budget of the distant Universe. Methods: We used the GOODS-MUSIC catalog, containing ~3000 Ks-selected (~10 000 z-selected) galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8~μm band, with spectroscopic or accurate photometric redshifts. We selected samples of BM/BX/LBGs, DRGs, and BzK galaxies to discuss the overlap and the limitations of these criteria, which can be overridden by a selection criterion based on physical parameters. We then measured the stellar masses of these galaxies and computed the stellar mass density (SMD) for the different samples up to redshift ≃4. Results: We show that the BzK-PE criterion is not optimal for selecting early type galaxies at the faint end. On the other hand, BzK-SF is highly contaminated by passively evolving galaxies at red z-Ks colours. We find that LBGs and DRGs contribute almost equally to the global SMD at z≥ 2 and, in general, that star-forming galaxies form a substantial fraction of the universal SMD. Passively evolving galaxies show a strong negative density evolution from redshift 2 to 3, indicating that we are witnessing the epoch of mass assembly of such objects. Finally we have indications that by pushing the selection to deeper magnitudes, the contribution of less massive DRGs could overtake that of LBGs. Deeper surveys, like the HUDF, are required to confirm this suggestion.

Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

DEFF Research Database (Denmark)

Planck Collaboration,; Ade, P. A. R.; Aghanim, N.

2013-01-01

We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo ......We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar...... range extending from rich clusters down to $M_{500}\\sim 2\\times 10^{13} \\Msolar$, and there is a clear indication of signal down to $M_{500}\\sim 4\\times 10^{12} \\Msolar$. Planck's SZ detections in such low-mass halos imply that about a quarter of all baryons have now been seen in the form of hot halo...... gas, and that this gas must be less concentrated than the dark matter in such halos in order to remain consistent with X-ray observations. At the high-mass end, the measured SZ signal is 20% lower than found from observations of X-ray clusters, a difference consistent with Malmquist bias effects...

CENTRAL DARK MATTER TRENDS IN EARLY-TYPE GALAXIES FROM STRONG LENSING, DYNAMICS, AND STELLAR POPULATIONS

International Nuclear Information System (INIS)

Tortora, C.; Jetzer, P.; Napolitano, N. R.; Romanowsky, A. J.

2010-01-01

We analyze the correlations between central dark matter (DM) content of early-type galaxies and their sizes and ages, using a sample of intermediate-redshift (z ∼ 0.2) gravitational lenses from the SLACS survey, and by comparing them to a larger sample of z ∼ 0 galaxies. We decompose the deprojected galaxy masses into DM and stellar components using combinations of strong lensing, stellar dynamics, and stellar populations modeling. For a given stellar mass, we find that for galaxies with larger sizes, the DM fraction increases and the mean DM density decreases, consistently with the cuspy halos expected in cosmological formation scenarios. The DM fraction also decreases with stellar age, which can be partially explained by the inverse correlation between size and age. The residual trend may point to systematic dependencies on formation epoch of halo contraction or stellar initial mass functions. These results are in agreement with recent findings based on local galaxies by Napolitano et al. and suggest negligible evidence of galaxy evolution over the last ∼2.5 Gyr other than passive stellar aging.

SMOOTH(ER) STELLAR MASS MAPS IN CANDELS: CONSTRAINTS ON THE LONGEVITY OF CLUMPS IN HIGH-REDSHIFT STAR-FORMING GALAXIES

International Nuclear Information System (INIS)

Wuyts, Stijn; Förster Schreiber, Natascha M.; Genzel, Reinhard; Lutz, Dieter; Guo Yicheng; Giavalisco, Mauro; Barro, Guillermo; Faber, Sandra M.; Kocevski, Dale D.; Koo, David C.; McGrath, Elizabeth; Bell, Eric F.; Dekel, Avishai; Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M.; Lotz, Jennifer; Hathi, Nimish P.; Huang, Kuang-Han; Newman, Jeffrey A.

2012-01-01

We perform a detailed analysis of the resolved colors and stellar populations of a complete sample of 323 star-forming galaxies (SFGs) at 0.5 10 M ☉ and have specific star formation rates (SFRs) above 1/t H . We model the seven-band optical ACS + near-IR WFC3 spectral energy distributions of individual bins of pixels, accounting simultaneously for the galaxy-integrated photometric constraints available over a longer wavelength range. We analyze variations in rest-frame color, stellar surface mass density, age, and extinction as a function of galactocentric radius and local surface brightness/density, and measure structural parameters on luminosity and stellar mass maps. We find evidence for redder colors, older stellar ages, and increased dust extinction in the nuclei of galaxies. Big star-forming clumps seen in star formation tracers are less prominent or even invisible in the inferred stellar mass distributions. Off-center clumps contribute up to ∼20% to the integrated SFR, but only 7% or less to the integrated mass of all massive SFGs at z ∼ 1 and z ∼ 2, with the fractional contributions being a decreasing function of wavelength used to select the clumps. The stellar mass profiles tend to have smaller sizes and M20 coefficients, and higher concentration and Gini coefficients than the light distribution. Our results are consistent with an inside-out disk growth scenario with brief (100-200 Myr) episodic local enhancements in star formation superposed on the underlying disk. Alternatively, the young ages of off-center clumps may signal inward clump migration, provided this happens efficiently on the order of an orbital timescale.

The Masses and Stellar Content of Nuclei in Early-Type Galaxies from Multi-Band Photometry and Spectroscopy

Science.gov (United States)

Spengler, Chelsea; Côté, Patrick; Roediger, Joel; Ferrarese, Laura; Sánchez-Janssen, Rubén; Toloba, Elisa; Liu, Yiqing; Guhathakurta, Puragra; Cuillandre, Jean-Charles; Gwyn, Stephen; Zirm, Andrew; Muñoz, Roberto; Puzia, Thomas; Lançon, Ariane; Peng, Eric; Mei, Simona; Powalka, Mathieu

2018-01-01

It is now established that most, if not all, massive galaxies host central supermassive black holes (SMBHs), and that these SMBHs are linked to the growth their host galaxies as shown by several scaling relations. Within the last couple of decades, it has become apparent that most lower-mass galaxies without obvious SMBHs nevertheless contain some sort of central massive object in the form of compact stellar nuclei that also follow identical (or similar) scaling relations. These nuclei are challenging to study given their small sizes and relatively faint magnitudes, but understanding their origins and relationship to their hosts is critical to gaining a more complete picture of galaxy evolution. To that end, we highlight selected results from an analysis of 39 nuclei and their early-type hosts in the Virgo Cluster using ten broadband filters: F300W, F475W, F850LP, F160W, u*griz, and Ks. We estimate masses, metallicities and ages using simple stellar population (SSP) models. For 19 nuclei, we compare to SSP parameters derived from Keck and Gemini spectra and find reasonable agreement between the photometric and spectroscopic metallicity: the RMS scatter is 0.3 dex. We reproduce the nucleus-galaxy mass fraction of 0.33 ± 0.08% for galaxy stellar masses 108.4-1010.3 M⊙ with a typical precision of ~35% for the nuclei masses. Based on available model predictions, there is no single preferred formation scenario for nuclei, suggesting that nuclei are formed stochastically through a mix of processes. Nuclei metallicities are statistically identical to those of their hosts, appearing 0.07 ± 0.3 dex more metal-rich on average — although, omitting galaxies with unusual origins (i.e., compact ellipticals), nuclei are 0.20 ± 0.28 dex more metal-rich. We find no clear age difference between nuclei and their galaxies, with nuclei displaying a broad range of ages. Interestingly, we find that the most massive nuclei may be flatter and more closely aligned with the semi

The PyCASSO database: spatially resolved stellar population properties for CALIFA galaxies

Science.gov (United States)

de Amorim, A. L.; García-Benito, R.; Cid Fernandes, R.; Cortijo-Ferrero, C.; González Delgado, R. M.; Lacerda, E. A. D.; López Fernández, R.; Pérez, E.; Vale Asari, N.

2017-11-01

The Calar Alto Legacy Integral Field Area (CALIFA) survey, a pioneer in integral field spectroscopy legacy projects, has fostered many studies exploring the information encoded on the spatially resolved data on gaseous and stellar features in the optical range of galaxies. We describe a value-added catalogue of stellar population properties for CALIFA galaxies analysed with the spectral synthesis code starlight and processed with the pycasso platform. Our public database (http://pycasso.ufsc.br/, mirror at http://pycasso.iaa.es/) comprises 445 galaxies from the CALIFA Data Release 3 with COMBO data. The catalogue provides maps for the stellar mass surface density, mean stellar ages and metallicities, stellar dust attenuation, star formation rates, and kinematics. Example applications both for individual galaxies and for statistical studies are presented to illustrate the power of this data set. We revisit and update a few of our own results on mass density radial profiles and on the local mass-metallicity relation. We also show how to employ the catalogue for new investigations, and show a pseudo Schmidt-Kennicutt relation entirely made with information extracted from the stellar continuum. Combinations to other databases are also illustrated. Among other results, we find a very good agreement between star formation rate surface densities derived from the stellar continuum and the H α emission. This public catalogue joins the scientific community's effort towards transparency and reproducibility, and will be useful for researchers focusing on (or complementing their studies with) stellar properties of CALIFA galaxies.

CONFIRMATION OF SMALL DYNAMICAL AND STELLAR MASSES FOR EXTREME EMISSION LINE GALAXIES AT z ∼ 2

Energy Technology Data Exchange (ETDEWEB)

Maseda, Michael V.; Van der Wel, Arjen; Da Cunha, Elisabete; Rix, Hans-Walter [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Pacifici, Camilla [Yonsei University Observatory, Yonsei University, Seoul 120-749 (Korea, Republic of); Momcheva, Ivelina; Van Dokkum, Pieter; Nelson, Erica J. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Brammer, Gabriel B.; Grogin, Norman A.; Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Franx, Marijn; Fumagalli, Mattia; Patel, Shannon G. [Leiden Observatory, Leiden University, Leiden (Netherlands); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Kocevski, Dale D. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Lundgren, Britt F. [Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States); Marchesini, Danilo [Physics and Astronomy Department, Tufts University, Robinson Hall, Room 257, Medford, MA 02155 (United States); Skelton, Rosalind E. [South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa); Straughn, Amber N., E-mail: maseda@mpia.de [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); and others

2013-11-20

Spectroscopic observations from the Large Binocular Telescope and the Very Large Telescope reveal kinematically narrow lines (∼50 km s{sup –1}) for a sample of 14 extreme emission line galaxies at redshifts 1.4 < z < 2.3. These measurements imply that the total dynamical masses of these systems are low (≲ 3 × 10{sup 9} M {sub ☉}). Their large [O III] λ5007 equivalent widths (500-1100 Å) and faint blue continuum emission imply young ages of 10-100 Myr and stellar masses of 10{sup 8}-10{sup 9} M {sub ☉}, confirming the presence of a violent starburst. The dynamical masses represent the first such determinations for low-mass galaxies at z > 1. The stellar mass formed in this vigorous starburst phase represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggests that supernova-driven winds must be of critical importance in the subsequent evolution of these systems.

The Importance of Preventive Feedback: Inference from Observations of the Stellar Masses and Metallicities of Milky Way Dwarf Galaxies

Energy Technology Data Exchange (ETDEWEB)

Lu, Yu; Benson, Andrew; Wetzel, Andrew; Tonnesen, Stephanie [The Observatories, The Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Mao, Yao-Yuan [Department of Physics and Astronomy and the Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, Pittsburgh, PA 15260 (United States); Peter, Annika H. G. [CCAPP and Department of Physics, The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210 (United States); Boylan-Kolchin, Michael [Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States); Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University, Stanford, CA 94305 (United States)

2017-09-01

Dwarf galaxies are known to have remarkably low star formation efficiency due to strong feedback. Adopting the dwarf galaxies of the Milky Way (MW) as a laboratory, we explore a flexible semi-analytic galaxy formation model to understand how the feedback processes shape the satellite galaxies of the MW. Using Markov Chain Monte Carlo, we exhaustively search a large parameter space of the model and rigorously show that the general wisdom of strong outflows as the primary feedback mechanism cannot simultaneously explain the stellar mass function and the mass–metallicity relation of the MW satellites. An extended model that assumes that a fraction of baryons is prevented from collapsing into low-mass halos in the first place can be accurately constrained to simultaneously reproduce those observations. The inference suggests that two different physical mechanisms are needed to explain the two different data sets. In particular, moderate outflows with weak halo mass dependence are needed to explain the mass–metallicity relation, and prevention of baryons falling into shallow gravitational potentials of low-mass halos (e.g., “pre-heating”) is needed to explain the low stellar mass fraction for a given subhalo mass.

Variation of galactic cold gas reservoirs with stellar mass

NARCIS (Netherlands)

Maddox, Natasha; Hess, Kelley M.; Obreschkow, Danail; Blyth, S.-L.; Jarvis, Matt J.

The stellar and neutral hydrogen (H I) mass functions at z ˜ 0 are fundamental benchmarks for current models of galaxy evolution. A natural extension of these benchmarks is the two-dimensional distribution of galaxies in the plane spanned by stellar and H I mass, which provides a more stringent test

THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT

Energy Technology Data Exchange (ETDEWEB)

Geha, Marla [Astronomy Department, Yale University, New Haven, CT 06520 (United States); Brown, Thomas M.; Tumlinson, Jason; Kalirai, Jason S.; Avila, Roberto J.; Ferguson, Henry C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Simon, Joshua D. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Kirby, Evan N. [Department of Physics and Astronomy, University of California Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); VandenBerg, Don A. [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6 (Canada); Munoz, Ricardo R. [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Guhathakurta, Puragra, E-mail: marla.geha@yale.edu, E-mail: tbrown@stsci.edu, E-mail: tumlinson@stsci.edu [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

2013-07-01

We present constraints on the stellar initial mass function (IMF) in two ultra-faint dwarf (UFD) galaxies, Hercules and Leo IV, based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. The Hercules and Leo IV galaxies are extremely low luminosity (M{sub V} = -6.2, -5.5), metal-poor (([Fe/H]) = -2.4, -2.5) systems that have old stellar populations (>11 Gyr). Because they have long relaxation times, we can directly measure the low-mass stellar IMF by counting stars below the main-sequence turnoff without correcting for dynamical evolution. Over the stellar mass range probed by our data, 0.52-0.77 M{sub Sun }, the IMF is best fit by a power-law slope of {alpha}= 1.2{sub -0.5}{sup +0.4} for Hercules and {alpha} = 1.3 {+-} 0.8 for Leo IV. For Hercules, the IMF slope is more shallow than a Salpeter ({alpha} = 2.35) IMF at the 5.8{sigma} level, and a Kroupa ({alpha} = 2.3 above 0.5 M{sub Sun }) IMF slope at 5.4{sigma} level. We simultaneously fit for the binary fraction, f{sub binary}, finding f{sub binary}= 0.47{sup +0.16}{sub -0.14} for Hercules, and 0.47{sup +0.37}{sub -0.17} for Leo IV. The UFD binary fractions are consistent with that inferred for Milky Way stars in the same mass range, despite very different metallicities. In contrast, the IMF slopes in the UFDs are shallower than other galactic environments. In the mass range 0.5-0.8 M{sub Sun }, we see a trend across the handful of galaxies with directly measured IMFs such that the power-law slopes become shallower (more bottom-light) with decreasing galactic velocity dispersion and metallicity. This trend is qualitatively consistent with results in elliptical galaxies inferred via indirect methods and is direct evidence for IMF variations with galactic environment.

The rise and fall of stellar across the peak of cosmic star formation history: effects of mergers versus diffuse stellar mass acquisition

Science.gov (United States)

Welker, C.; Dubois, Y.; Devriendt, J.; Pichon, C.; Kaviraj, S.; Peirani, S.

2017-02-01

Building galaxy merger trees from a state-of-the-art cosmological hydrodynamical simulation, Horizon-AGN, we perform a statistical study of how mergers and diffuse stellar mass acquisition processes drive galaxy morphologic properties above z > 1. By diffuse mass acquisition here, we mean both accretion of stars by unresolved mergers (relative stellar mass growth smaller than 4.5 per cent) as well as in situ star formation when no resolved mergers are detected along the main progenitor branch of a galaxy. We investigate how stellar densities, galaxy sizes and galaxy morphologies (defined via shape parameters derived from the inertia tensor of the stellar density) depend on mergers of different mass ratios. We investigate how stellar densities, effective radii and shape parameters derived from the inertia tensor depend on mergers of different mass ratios. We find strong evidence that diffuse stellar accretion and in situ formation tend to flatten small galaxies over cosmic time, leading to the formation of discs. On the other hand, mergers, and not only the major ones, exhibit a propensity to puff up and destroy stellar discs, confirming the origin of elliptical galaxies. We confirm that mergers grow galaxy sizes more efficiently than diffuse processes (r_{0.5}∝ M_s^{0.85} and r_{0.5}∝ M_s^{0.1} on average, respectively) and we also find that elliptical galaxies are more susceptible to grow in size through mergers than disc galaxies with a size-mass evolution r_{0.5}∝ M_s^{1.2} instead of r_{0.5}∝ M_s^{-0.5}-M^{0.5} for discs depending on the merger mass ratio. The gas content drives the size-mass evolution due to merger with a faster size growth for gas-poor galaxies r_{0.5}∝ M_s2 than for gas-rich galaxies r0.5 ∝ Ms.

The evolution of the stellar mass functions of star-forming and quiescent galaxies to z = 4 from the COSMOS/ultraVISTA survey

DEFF Research Database (Denmark)

Muzzin, Adam; Marchesini, Danilo; Stefano, Mauro

2013-01-01

We present measurements of the stellar mass functions (SMFs) of star-forming and quiescent galaxies to z = 4 using a sample of 95,675 Ks -selected galaxies in the COSMOS/UltraVISTA field. The SMFs of the combined population are in good agreement with previous measurements and show that the stellar...

SDSS IV MaNGA: the global and local stellar mass assemby histories of galaxies

Science.gov (United States)

Ibarra-Medel, Héctor J.; Sánchez, Sebastián F.; Avila-Reese, Vladimir; Hernández-Toledo, Héctor M.; González, J. Jesús; Drory, Niv; Bundy, Kevin; Bizyaev, Dmitry; Cano-Díaz, Mariana; Malanushenko, Elena; Pan, Kaike; Roman-Lopes, Alexandre; Thomas, Daniel

2016-12-01

Using the fossil record method implemented through Pipe3D, we reconstruct the global and radial stellar mass growth histories (MGHs) of a large sample of galaxies, ranging from dwarf to giant objects, from the Mapping Nearby Galaxies at the Apache Point Observatory (MaNGA) survey. We confirm that the main driver of the global MGHs is mass, with more massive galaxies assembling earlier (downsizing), though for a given mass, the global MGHs segregate by colour, specific star formation rate and morphological type. From the inferred radial mean MGHs, we find that at fractions of assembled mass larger than ˜80 per cent, the innermost regions formed stars, on average, in the inside-out mode. At earlier epochs, when the age estimation of the method becomes poor, the MGHs seem to be spatially homogeneous or even in the outside-in mode, especially for the red/quiescent/early-type galaxies. The innermost MGHs are, in general, less scattered around the mean than the outermost MGHs. For dwarf and low-mass galaxies, we do not find evidence of an outside-in formation mode; instead, their radial MGHs are very diverse most of the time, with periods of outside-in and inside-out modes (or strong radial migration), suggesting this is an episodic star formation history. Blue/star-forming/late-type galaxies present, on average, a significantly more pronounced inside-out formation mode than red/quiescent/early-type galaxies, independently of mass. We discuss our results in the light of the processes of galaxy formation, quenching and radial migration. We also discuss the uncertainties and biases of the fossil record method and how these could affect our results.

Stellar streams and the galaxies they reside in

Science.gov (United States)

Pearson, Sarah

2018-01-01

As galaxies collide, as smaller galaxies are disrupted by larger galaxies, or as clusters of stars orbit a galaxy, a gravitational tidal interaction unfolds and the systems tear apart into distinct morphological and kinematic structures. In my thesis, I have exploited these structures to understand various components of galaxies, such as the baryon cycle in dwarf galaxy interactions (Pearson et al. 2016, Pearson et al. 2017b). In this talk, I will focus on my thesis work related to the stellar stream emerging from the old, globular cluster, Palomar 5 (Pal 5), orbiting our own Milky Way. As the stellar stream members were once closely tied together in energy and angular momentum space, we can use their distribution in phase space to trace back where they were once located and what affected them along their paths. In particular, I will show that the mere existence of Pal 5’s thin stream can rule out a moderately triaxial potential model of our Galaxy (Pearson et al. 2015) and that the debris of Pal 5-like streams will spread much further in space in a triaxial potential (a mechanism which I dubbed “stream fanning”) . Additionally, I will show that the Milky Way's Galactic bar, can punch holes in stellar streams and explain the recently discovered length asymmetry between Pal 5’s leading and trailing arm (Pearson et al. 2017a). These holes grow and have locations along stellar streams dependent on the Galactic bar orientation, mass and rotational speed, which provides an intriguing methodology for studying our own Milky Way’s Galactic bar in more detail. The fact that the bar can create under densities in stellar streams, further demonstrates that we should be careful when interpreting gaps in stellar streams as indirect evidence of the existence of dark matter subhalos in our Galaxy.

THE STELLAR VELOCITY DISPERSION OF A COMPACT MASSIVE GALAXY AT z = 1.80 USING X-SHOOTER: CONFIRMATION OF THE EVOLUTION IN THE MASS-SIZE AND MASS-DISPERSION RELATIONS ,

International Nuclear Information System (INIS)

Van de Sande, Jesse; Franx, Marijn; Labbe, Ivo; Kriek, Mariska; Van Dokkum, Pieter G.; Bezanson, Rachel; Whitaker, Katherine E.; Brammer, Gabriel; Groot, Paul J.; Kaper, Lex

2011-01-01

Recent photometric studies have shown that early-type galaxies at fixed stellar mass were smaller and denser at earlier times. In this Letter, we assess that finding by deriving the dynamical mass of such a compact quiescent galaxy at z = 1.8. We have obtained a high-quality spectrum with full UV-NIR wavelength coverage of galaxy NMBS-C7447 using X-Shooter on the Very Large Telescope. We determined a velocity dispersion of 294 ± 51 km s -1 . Given this velocity dispersion and the effective radius of 1.64 ± 0.15 kpc (as determined from Hubble Space Telescope Wide Field Camera 3 F160W observations) we derive a dynamical mass of (1.7 ± 0.5) x 10 11 M sun . Comparison of the full spectrum with stellar population synthesis models indicates that NMBS-C774 has a relatively young stellar population (0.40 Gyr) with little or no star formation and a stellar mass of M * ∼ 1.5 x 10 11 M sun . The dynamical and photometric stellar masses are in good agreement. Thus, our study supports the conclusion that the mass densities of quiescent galaxies were indeed higher at earlier times, and this earlier result is not caused by systematic measurement errors. By combining available spectroscopic measurements at different redshifts, we find that the velocity dispersion at fixed dynamical mass was a factor of ∼1.8 higher at z = 1.8 compared with z = 0. Finally, we show that the apparent discrepancies between the few available velocity dispersion measurements at z > 1.5 are consistent with the intrinsic scatter of the mass-size relation.

The X-Ray Luminosity Functions of Field Low-Mass X-Ray Binaries in Early-Type Galaxies: Evidence for a Stellar Age Dependence

Science.gov (United States)

Lehmer, B. D.; Berkeley, M.; Zezas, A.; Alexander, D. M.; Basu-Zych, A.; Bauer, F. E.; Brandt, W. N.; Fragos, T.; Hornschemeier, A. E.; Kalogera, V.;

PRIMUS: CONSTRAINTS ON STAR FORMATION QUENCHING AND GALAXY MERGING, AND THE EVOLUTION OF THE STELLAR MASS FUNCTION FROM z = 0-1

Energy Technology Data Exchange (ETDEWEB)

Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States); Coil, Alison L.; Mendez, Alexander J. [Center for Astrophysics and Space Sciences, Department of Physics, University of California, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Aird, James [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Cool, Richard J. [MMT Observatory, University of Arizona, 1540 E Second Street, Tucson, AZ 85721 (United States); Eisenstein, Daniel J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wong, Kenneth C. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Zhu, Guangtun [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Arnouts, Stephane, E-mail: jmoustakas@siena.edu [Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States)

2013-04-10

We measure the evolution of the stellar mass function (SMF) from z = 0-1 using multi-wavelength imaging and spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From PRIMUS we construct an i < 23 flux-limited sample of {approx}40, 000 galaxies at z = 0.2-1.0 over five fields totaling Almost-Equal-To 5.5 deg{sup 2}, and from the SDSS we select {approx}170, 000 galaxies at z = 0.01-0.2 that we analyze consistently with respect to PRIMUS to minimize systematic errors in our evolutionary measurements. We find that the SMF of all galaxies evolves relatively little since z = 1, although we do find evidence for mass assembly downsizing; we measure a Almost-Equal-To 30% increase in the number density of {approx}10{sup 10} M{sub sun} galaxies since z Almost-Equal-To 0.6, and a {approx}< 10% change in the number density of all {approx}> 10{sup 11} M{sub sun} galaxies since z Almost-Equal-To 1. Dividing the sample into star-forming and quiescent using an evolving cut in specific star formation rate, we find that the number density of {approx}10{sup 10} M{sub sun} star-forming galaxies stays relatively constant since z Almost-Equal-To 0.6, whereas the space density of {approx}> 10{sup 11} M{sub sun} star-forming galaxies decreases by Almost-Equal-To 50% between z Almost-Equal-To 1 and z Almost-Equal-To 0. Meanwhile, the number density of {approx}10{sup 10} M{sub sun} quiescent galaxies increases steeply toward low redshift, by a factor of {approx}2-3 since z Almost-Equal-To 0.6, while the number of massive quiescent galaxies remains approximately constant since z Almost-Equal-To 1. These results suggest that the rate at which star-forming galaxies are quenched increases with decreasing stellar mass, but that the bulk of the stellar mass buildup within the quiescent population occurs around {approx}10{sup 10.8} M{sub sun}. In addition, we conclude that mergers do not appear to be a dominant channel for the stellar mass

The stellar initial mass function of early-type galaxies from low to high stellar velocity dispersion: homogeneous analysis of ATLAS3D and Sloan Lens ACS galaxies

Science.gov (United States)

Posacki, Silvia; Cappellari, Michele; Treu, Tommaso; Pellegrini, Silvia; Ciotti, Luca

2015-01-01

We present an investigation about the shape of the initial mass function (IMF) of early-type galaxies (ETGs), based on a joint lensing and dynamical analysis, and on stellar population synthesis models, for a sample of 55 lens ETGs identified by the Sloan Lens Advanced Camera for Surveys (SLACS). We construct axisymmetric dynamical models based on the Jeans equations which allow for orbital anisotropy and include a dark matter halo. The models reproduce in detail the observed Hubble Space Telescope photometry and are constrained by the total projected mass within the Einstein radius and the stellar velocity dispersion (σ) within the Sloan Digital Sky Survey fibres. Comparing the dynamically-derived stellar mass-to-light ratios (M*/L)dyn, obtained for an assumed halo slope ρh ∝ r-1, to the stellar population ones (M*/L)Salp, derived from full-spectrum fitting and assuming a Salpeter IMF, we infer the mass normalization of the IMF. Our results confirm the previous analysis by the SLACS team that the mass normalization of the IMF of high-σ galaxies is consistent on average with a Salpeter slope. Our study allows for a fully consistent study of the trend between IMF and σ for both the SLACS and atlas3D samples, which explore quite different σ ranges. The two samples are highly complementary, the first being essentially σ selected, and the latter volume-limited and nearly mass selected. We find that the two samples merge smoothly into a single trend of the form log α = (0.38 ± 0.04) × log (σe/200 km s-1) + ( - 0.06 ± 0.01), where α = (M*/L)dyn/(M*/L)Salp and σe is the luminosity averaged σ within one effective radius Re. This is consistent with a systematic variation of the IMF normalization from Kroupa to Salpeter in the interval σe ≈ 90-270 km s-1.

The Galaxy mass function up to z =4 in the GOODS-MUSIC sample: into the epoch of formation of massive galaxies

Science.gov (United States)

Fontana, A.; Salimbeni, S.; Grazian, A.; Giallongo, E.; Pentericci, L.; Nonino, M.; Fontanot, F.; Menci, N.; Monaco, P.; Cristiani, S.; Vanzella, E.; de Santis, C.; Gallozzi, S.

2006-12-01

Aims.The goal of this work is to measure the evolution of the Galaxy Stellar Mass Function and of the resulting Stellar Mass Density up to redshift ≃4, in order to study the assembly of massive galaxies in the high redshift Universe. Methods: .We have used the GOODS-MUSIC catalog, containing 3000 Ks-selected galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8 μm band, of which 27% have spectroscopic redshifts and the remaining fraction have accurate photometric redshifts. On this sample we have applied a standard fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass Function and the resulting Stellar Mass Density up to redshift ≃4, taking into proper account the biases and incompleteness effects. Results: .Within the well known trend of global decline of the Stellar Mass Density with redshift, we show that the decline of the more massive galaxies may be described by an exponential timescale of ≃6 Gyr up to z≃ 1.5, and proceeds much faster thereafter, with an exponential timescale of ≃0.6 Gyr. We also show that there is some evidence for a differential evolution of the Galaxy Stellar Mass Function, with low mass galaxies evolving faster than more massive ones up to z≃ 1{-}1.5 and that the Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close to the local one) up to z≃ 1{-}1.3. Conclusions: .The observed behaviour of the Galaxy Stellar Mass Function is consistent with a scenario where about 50% of present-day massive galaxies formed at a vigorous rate in the epoch between redshift 4 and 1.5, followed by a milder evolution until the present-day epoch.

The Stellar Initial Mass Function in Early-type Galaxies from Absorption Line Spectroscopy. I. Data and Empirical Trends

Science.gov (United States)

van Dokkum, Pieter G.; Conroy, Charlie

2012-11-01

The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted CCDs with little or no fringing it has recently become possible to obtain accurate measurements of these features. Here, we present spectra covering the wavelength ranges 0.35-0.55 μm and 0.72-1.03 μm for the bulge of M31 and 34 early-type galaxies from the SAURON sample, obtained with the Low Resolution Imaging Spectrometer on Keck. The signal-to-noise ratio is >~ 200 Å-1 out to 1 μm, which is sufficient to measure gravity-sensitive features for individual galaxies and to determine how they depend on other properties of the galaxies. Combining the new data with previously obtained spectra for globular clusters in M31 and the most massive elliptical galaxies in the Virgo cluster, we find that the dwarf-sensitive Na I λ8183, 8195 doublet and the FeH λ9916 Wing-Ford band increase systematically with velocity dispersion, while the giant-sensitive Ca II λ8498, 8542, 8662 triplet decreases with dispersion. These trends are consistent with a varying IMF, such that galaxies with deeper potential wells have more dwarf-enriched mass functions. In a companion paper, we use a comprehensive stellar population synthesis model to demonstrate that IMF effects can be separated from age and abundance variations and quantify the IMF variation among early-type galaxies.

THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES FROM ABSORPTION LINE SPECTROSCOPY. I. DATA AND EMPIRICAL TRENDS

International Nuclear Information System (INIS)

Van Dokkum, Pieter G.; Conroy, Charlie

2012-01-01

The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted CCDs with little or no fringing it has recently become possible to obtain accurate measurements of these features. Here, we present spectra covering the wavelength ranges 0.35-0.55 μm and 0.72-1.03 μm for the bulge of M31 and 34 early-type galaxies from the SAURON sample, obtained with the Low Resolution Imaging Spectrometer on Keck. The signal-to-noise ratio is ∼> 200 Å –1 out to 1 μm, which is sufficient to measure gravity-sensitive features for individual galaxies and to determine how they depend on other properties of the galaxies. Combining the new data with previously obtained spectra for globular clusters in M31 and the most massive elliptical galaxies in the Virgo cluster, we find that the dwarf-sensitive Na I λ8183, 8195 doublet and the FeH λ9916 Wing-Ford band increase systematically with velocity dispersion, while the giant-sensitive Ca II λ8498, 8542, 8662 triplet decreases with dispersion. These trends are consistent with a varying IMF, such that galaxies with deeper potential wells have more dwarf-enriched mass functions. In a companion paper, we use a comprehensive stellar population synthesis model to demonstrate that IMF effects can be separated from age and abundance variations and quantify the IMF variation among early-type galaxies.

Dark-Matter in Galaxies from Gravitational Lensing and Stellar Dynamics Studies

NARCIS (Netherlands)

Koopmans, L. V. E.; Corbett, IF

2010-01-01

Strong gravitational lensing and stellar dynamics provide two complementary methods in the study of the mass distribution of dark matter in galaxies out to redshift of unity. They are particularly powerful in the determination of the total mass and the density profile of mass early-type galaxies on

ORIGIN OF THE GALAXY MASS-METALLICITY-STAR FORMATION RELATION

International Nuclear Information System (INIS)

Harwit, Martin; Brisbin, Drew

2015-01-01

We describe an equilibrium model that links the metallicity of low-redshift galaxies to stellar evolution models. It enables the testing of different stellar initial mass functions and metal yields against observed galaxy metallicities. We show that the metallicities of more than 80,000 Sloan Digital Sky Survey galaxies in the low-redshift range 0.07 ≤ z ≤ 0.3 considerably constrain stellar evolution models that simultaneously relate galaxy stellar mass, metallicity, and star formation rates to the infall rate of low-metallicity extragalactic gas and outflow of enriched matter. A feature of our model is that it encompasses both the active star forming phases of a galaxy and epochs during which the same galaxy may lie fallow. We show that the galaxy mass-metallicity-star formation relation can be traced to infall of extragalactic gas mixing with native gas from host galaxies to form stars of observed metallicities, the most massive of which eject oxygen into extragalactic space. Most consequential among our findings is that, on average, extragalactic infall accounts for one half of the gas required for star formation, a ratio that is remarkably constant across galaxies with stellar masses ranging at least from M* = 2 × 10 9 to 6 × 10 10 M ☉ . This leads us to propose that star formation is initiated when extragalactic infall roughly doubles the mass of marginally stable interstellar clouds. The processes described may also account quantitatively for the metallicity of extragalactic space, though to check this the fraction of extragalactic baryons will need to be more firmly established

ORIGIN OF THE GALAXY MASS-METALLICITY-STAR FORMATION RELATION

Energy Technology Data Exchange (ETDEWEB)

Harwit, Martin; Brisbin, Drew, E-mail: harwit@verizon.net [Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States)

2015-02-20

We describe an equilibrium model that links the metallicity of low-redshift galaxies to stellar evolution models. It enables the testing of different stellar initial mass functions and metal yields against observed galaxy metallicities. We show that the metallicities of more than 80,000 Sloan Digital Sky Survey galaxies in the low-redshift range 0.07 ≤ z ≤ 0.3 considerably constrain stellar evolution models that simultaneously relate galaxy stellar mass, metallicity, and star formation rates to the infall rate of low-metallicity extragalactic gas and outflow of enriched matter. A feature of our model is that it encompasses both the active star forming phases of a galaxy and epochs during which the same galaxy may lie fallow. We show that the galaxy mass-metallicity-star formation relation can be traced to infall of extragalactic gas mixing with native gas from host galaxies to form stars of observed metallicities, the most massive of which eject oxygen into extragalactic space. Most consequential among our findings is that, on average, extragalactic infall accounts for one half of the gas required for star formation, a ratio that is remarkably constant across galaxies with stellar masses ranging at least from M* = 2 × 10{sup 9} to 6 × 10{sup 10} M {sub ☉}. This leads us to propose that star formation is initiated when extragalactic infall roughly doubles the mass of marginally stable interstellar clouds. The processes described may also account quantitatively for the metallicity of extragalactic space, though to check this the fraction of extragalactic baryons will need to be more firmly established.

SDSS-IV MaNGA: The Spatially Resolved Stellar Initial Mass Function in ˜400 Early-Type Galaxies

Science.gov (United States)

Parikh, Taniya; Thomas, Daniel; Maraston, Claudia; Westfall, Kyle B.; Goddard, Daniel; Lian, Jianhui; Meneses-Goytia, Sofia; Jones, Amy; Vaughan, Sam; Andrews, Brett H.; Bershady, Matthew; Bizyaev, Dmitry; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Drory, Niv; Emsellem, Eric; Law, David R.; Newman, Jeffrey A.; Roman-Lopes, Alexandre; Wake, David; Yan, Renbin; Zheng, Zheng

2018-03-01

MaNGA provides the opportunity to make precise spatially resolved measurements of the IMF slope in galaxies owing to its unique combination of spatial resolution, wavelength coverage and sample size. We derive radial gradients in age, element abundances and IMF slope analysing optical and near-infrared absorption features from stacked spectra out to the half-light radius of 366 early-type galaxies with masses 9.9 - 10.8 log M/M⊙. We find flat gradients in age and [α/Fe] ratio, as well as negative gradients in metallicity, consistent with the literature. We further derive significant negative gradients in the [Na/Fe] ratio with galaxy centres being well enhanced in Na abundance by up to 0.5 dex. Finally, we find a gradient in IMF slope with a bottom-heavy IMF in the centre (typical mass excess factor of 1.5) and a Milky Way-type IMF at the half-light radius. This pattern is mass-dependent with the lowest mass galaxies in our sample featuring only a shallow gradient around a Milky Way IMF. Our results imply the local IMF-σ relation within galaxies to be even steeper than the global relation and hint towards the local metallicity being the dominating factor behind the IMF variations. We also employ different stellar population models in our analysis and show that a radial IMF gradient is found independently of the stellar population model used. A similar analysis of the Wing-Ford band provides inconsistent results and further evidence of the difficulty in measuring and modelling this particular feature.

Galaxy Masses : A Review

NARCIS (Netherlands)

Courteau, Stephane; Cappellari, Michele; Jong, Roelof S. de; Dutton, Aaron A.; Koopmans, L.V.E.

2013-01-01

Galaxy masses play a fundamental role in our understanding of structure formation models. This review addresses the variety and reliability of mass estimators that pertain to stars, gas, and dark matter. The dierent sections on masses from stellar populations, dynamical masses of gas-rich and

SUPERDENSE GALAXIES AND THE MASS-SIZE RELATION AT LOW REDSHIFT

International Nuclear Information System (INIS)

Poggianti, B. M.; Calvi, R.; Fasano, G.; Vulcani, B.; Bettoni, D.; Gullieuszik, M.; Omizzolo, A.; Bindoni, D.; D'Onofrio, M.; Moretti, A.; Valentinuzzi, T.; Fritz, J.; De Lucia, G.

2013-01-01

We search for massive and compact galaxies (superdense galaxies, hereafter SDGs) at z = 0.03-0.11 in the Padova-Millennium Galaxy and Group Catalogue, a spectroscopically complete sample representative of the general field population of the local universe. We find that compact galaxies with radii and mass densities comparable to high-z massive and passive galaxies represent 4.4% of all galaxies with stellar masses above 3 × 10 10 M ☉ , yielding a number density of 4.3 × 10 –4 h 3 Mpc –3 . Most of them are S0s (70%) or ellipticals (23%), are red, and have intermediate-to-old stellar populations, with a median luminosity-weighted age of 5.4 Gyr and a median mass-weighted age of 9.2 Gyr. Their velocity dispersions and dynamical masses are consistent with the small radii and high stellar mass estimates. Comparing with the WINGS sample of cluster galaxies at similar redshifts, the fraction of SDGs is three times smaller in the field than in clusters, and cluster SDGs are on average 4 Gyr older than field SDGs. We confirm the existence of a universal trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. As a consequence, the median mass-size relation shifts toward smaller radii for galaxies with older stars, but the effect is much more pronounced in clusters than in the field. Our results show that, on top of the well-known dependence of stellar age on galaxy mass, the luminosity-weighted age of galaxies depends on galaxy compactness at fixed mass and, for a fixed mass and radius, on environment. This effect needs to be taken into account in order not to overestimate the evolution of galaxy sizes from high to low z. Our results and hierarchical simulations suggest that a significant fraction of the massive compact galaxies at high z have evolved into compact galaxies in galaxy clusters today. When stellar age and environmental effects are taken into account, the average amount of size evolution of individual galaxies between high and low

Stellar Dynamics and Star Formation Histories of z ∼ 1 Radio-loud Galaxies

Energy Technology Data Exchange (ETDEWEB)

Barišić, Ivana; Van der Wel, Arjen; Chauké, Priscilla; Van Houdt, Josha; Straatman, Caroline [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Bezanson, Rachel [Department of Astrophysics, Princeton University, Princeton, NJ 08544 (United States); Pacifici, Camilla [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Noeske, Kai [experimenta gGmbH, Kranenstraße 14, 74072 Heilbronn (Germany); Muñoz-Mateos, Juan C. [European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago (Chile); Franx, Marijn; Labbé, Ivo; Maseda, Michael V.; Sobral, David [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 AA Leiden (Netherlands); Smolčić, Vernesa [Department of Physics, Faculty of Science, University of Zagreb, Bijenicka cesta 32, 10000 Zagreb (Croatia); Bell, Eric F. [Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109 (United States); Brammer, Gabriel [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Calhau, João [Department of Physics, Lancaster University, Lancaster LA1 4 YB (United Kingdom); Van Dokkum, Pieter G. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Gallazzi, Anna [INAF-Osservatorio Astrofsico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Muzzin, Adam, E-mail: barisic@mpia.de [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, Ontario, ON MJ3 1P3 (Canada); and others

2017-09-20

We investigate the stellar kinematics and stellar populations of 58 radio-loud galaxies of intermediate luminosities ( L {sub 3} {sub GHz} > 10{sup 23} W Hz{sup −1}) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz data set. The LEGA-C continuum spectra reveal for the first time stellar velocity dispersions and age indicators of z ∼ 1 radio galaxies. We find that z ∼ 1 radio-loud active galactic nucleus (AGN) occur exclusively in predominantly old galaxies with high velocity dispersions: σ {sub *} > 175 km s{sup −1}, corresponding to black hole masses in excess of 10{sup 8} M {sub ⊙}. Furthermore, we confirm that at a fixed stellar mass the fraction of radio-loud AGN at z ∼ 1 is five to 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z ∼ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black hole masses, radio loudness, and quiescence at z ∼ 1.

Exploring the luminosity evolution and stellar mass assembly of 2SLAQ luminous red galaxies between redshifts 0.4 and 0.8

Science.gov (United States)

Banerji, Manda; Ferreras, Ignacio; Abdalla, Filipe B.; Hewett, Paul; Lahav, Ofer

2010-03-01

We present an analysis of the evolution of 8625 luminous red galaxies (LRGs) between z = 0.4 and 0.8 in the 2dF and Sloan Digital Sky Survey LRG and QSO (2SLAQ) survey. The LRGs are split into redshift bins and the evolution of both the luminosity and stellar mass function with redshift is considered and compared to the assumptions of a passive evolution scenario. We draw attention to several sources of systematic error that could bias the evolutionary predictions made in this paper. While the inferred evolution is found to be relatively unaffected by the exact choice of spectral evolution model used to compute K + e corrections, we conclude that photometric errors could be a source of significant bias in colour-selected samples such as this, in particular when using parametric maximum likelihood based estimators. We find that the evolution of the most massive LRGs is consistent with the assumptions of passive evolution and that the stellar mass assembly of the LRGs is largely complete by z ~ 0.8. Our findings suggest that massive galaxies with stellar masses above 1011Msolar must have undergone merging and star formation processes at a very early stage (z >~ 1). This supports the emerging picture of downsizing in both the star formation as well as the mass assembly of early-type galaxies. Given that our spectroscopic sample covers an unprecedentedly large volume and probes the most massive end of the galaxy mass function, we find that these observational results present a significant challenge for many current models of galaxy formation.

BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES

International Nuclear Information System (INIS)

El-Badry, Kareem; Geha, Marla; Wetzel, Andrew; Hopkins, Philip F.; Kereš, Dusan; Chan, T. K.; Faucher-Giguère, Claude-André

2016-01-01

We examine the effects of stellar feedback and bursty star formation on low-mass galaxies (M star  = 2 × 10 6  − 5 × 10 10 M ⊙ ) using the Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized the impact of feedback on dark matter profiles, we investigate the impact on the stellar component: kinematics, radial migration, size evolution, and population gradients. Feedback-driven outflows/inflows drive significant radial stellar migration over both short and long timescales via two processes: (1) outflowing/infalling gas can remain star-forming, producing young stars that migrate ∼1 kpc within their first 100 Myr, and (2) gas outflows/inflows drive strong fluctuations in the global potential, transferring energy to all stars. These processes produce several dramatic effects. First, galaxies’ effective radii can fluctuate by factors of >2 over ∼200 Myr, and these rapid size fluctuations can account for much of the observed scatter in the radius at fixed M star . Second, the cumulative effects of many outflow/infall episodes steadily heat stellar orbits, causing old stars to migrate outward most strongly. This age-dependent radial migration mixes—and even inverts—intrinsic age and metallicity gradients. Thus, the galactic-archaeology approach of calculating radial star formation histories from stellar populations at z = 0 can be severely biased. These effects are strongest at M star  ≈ 10 7–9.6 M ⊙ , the same regime where feedback most efficiently cores galaxies. Thus, detailed measurements of stellar kinematics in low-mass galaxies can strongly constrain feedback models and test baryonic solutions to small-scale problems in ΛCDM

INSIGHTS ON THE STELLAR MASS-METALLICITY RELATION FROM THE CALIFA SURVEY

Energy Technology Data Exchange (ETDEWEB)

González Delgado, R. M.; García-Benito, R.; Pérez, E.; Cortijo-Ferrero, C.; López Fernández, R.; Sánchez, S. F. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, E-18008 Granada (Spain); Cid Fernandes, R.; De Amorim, A. L.; Lacerda, E. A. D.; Vale Asari, N. [Departamento de Física, Universidade Federal de Santa Catarina, P.O. Box 476, 88040-900 Florianópolis, SC (Brazil); Alves, J. [University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna (Austria); Bland-Hawthorn, J. [Sydney Institute for Astronomy, The University of Sydney, NSW 2006 (Australia); Galbany, L. [Millennium Institute of Astrophysics and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Gallazzi, A. [INAF—Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Husemann, B. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. München (Germany); Bekeraite, S. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Jungwiert, B. [Astronomical Institute of the Academy of Sciences of the Czech Republic, v.v.i., Bocni II 1401, 14131 Prague (Czech Republic); López-Sánchez, A. R. [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); De Lorenzo-Cáceres, A. [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Marino, R. A. [CEI Campus Moncloa, UCM-UPM, Departamento de Astrofísica y CC. de la Atmósfera, Facultad de CC. Físicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain); Collaboration: CALIFA collaboration920; and others

2014-08-10

We use spatially and temporally resolved maps of stellar population properties of 300 galaxies from the CALIFA integral field survey to investigate how the stellar metallicity (Z {sub *}) relates to the total stellar mass (M {sub *}) and the local mass surface density (μ{sub *}) in both spheroidal- and disk-dominated galaxies. The galaxies are shown to follow a clear stellar mass-metallicity relation (MZR) over the whole 10{sup 9}-10{sup 12} M {sub ☉} range. This relation is steeper than the one derived from nebular abundances, which is similar to the flatter stellar MZR derived when we consider only young stars. We also find a strong relation between the local values of μ{sub *} and Z {sub *} (the μZR), betraying the influence of local factors in determining Z {sub *}. This shows that both local (μ{sub *}-driven) and global (M {sub *}-driven) processes are important in determining metallicity in galaxies. We find that the overall balance between local and global effects varies with the location within a galaxy. In disks, μ{sub *} regulates Z {sub *}, producing a strong μZR whose amplitude is modulated by M {sub *}. In spheroids it is M {sub *} that dominates the physics of star formation and chemical enrichment, with μ{sub *} playing a minor, secondary role. These findings agree with our previous analysis of the star formation histories of CALIFA galaxies, which showed that mean stellar ages are mainly governed by surface density in galaxy disks and by total mass in spheroids.

Blueberry Galaxies: The Lowest Mass Young Starbursts

Science.gov (United States)

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

2017-09-01

Searching for extreme emission line galaxies allows us to find low-mass metal-poor galaxies that are good analogs of high redshift Lyα emitting galaxies. These low-mass extreme emission line galaxies are also potential Lyman-continuum leakers. Finding them at very low redshifts (z≲ 0.05) allows us to be sensitive to even lower stellar masses and metallicities. We report on a sample of extreme emission line galaxies at z≲ 0.05 (blueberry galaxies). We selected them from SDSS broadband images on the basis of their broadband colors and studied their properties with MMT spectroscopy. From the entire SDSS DR12 photometric catalog, we found 51 photometric candidates. We spectroscopically confirm 40 as blueberry galaxies. (An additional seven candidates are contaminants, and four remain without spectra.) These blueberries are dwarf starburst galaxies with very small sizes (<1 kpc) and very high ionization ([O III]/[O II] ˜ 10-60). They also have some of the lowest stellar masses ({log}(M/{M}⊙ )˜ 6.5{--}7.5) and lowest metallicities (7.1< 12+{log}({{O}}/{{H}})< 7.8) of starburst galaxies. Thus, they are small counterparts to green pea galaxies and high redshift Lyα emitting galaxies.

Evolution of the Stellar Mass–Metallicity Relation. I. Galaxies in the z ∼ 0.4 Cluster Cl0024

Science.gov (United States)

Leethochawalit, Nicha; Kirby, Evan N.; Moran, Sean M.; Ellis, Richard S.; Treu, Tommaso

2018-03-01

We present the stellar mass–stellar metallicity relationship (MZR) in the galaxy cluster Cl0024+1654 at z ∼ 0.4 using full-spectrum stellar population synthesis modeling of individual quiescent galaxies. The lower limit of our stellar mass range is M * = 109.7 M ⊙, the lowest galaxy mass at which individual stellar metallicity has been measured beyond the local universe. We report a detection of an evolution of the stellar MZR with observed redshift at 0.037 ± 0.007 dex per Gyr, consistent with the predictions from hydrodynamical simulations. Additionally, we find that the evolution of the stellar MZR with observed redshift can be explained by an evolution of the stellar MZR with the formation time of galaxies, i.e., when the single stellar population (SSP)-equivalent ages of galaxies are taken into account. This behavior is consistent with stars forming out of gas that also has an MZR with a normalization that decreases with redshift. Lastly, we find that over the observed mass range, the MZR can be described by a linear function with a shallow slope ([{Fe}/{{H}}]\\propto (0.16+/- 0.03){log}{M}* ). The slope suggests that galaxy feedback, in terms of mass-loading factor, might be mass-independent over the observed mass and redshift range.

Stellar population in star formation regions of galaxies

Science.gov (United States)

Gusev, Alexander S.; Shimanovskaya, Elena V.; Shatsky, Nikolai I.; Sakhibov, Firouz; Piskunov, Anatoly E.; Kharchenko, Nina V.

2018-05-01

We developed techniques for searching young unresolved star groupings (clusters, associations, and their complexes) and of estimating their physical parameters. Our study is based on spectroscopic, spectrophotometric, and UBVRI photometric observations of 19 spiral galaxies. In the studied galaxies, we found 1510 objects younger than 10 Myr and present their catalogue. Having combined photometric and spectroscopic data, we derived extinctions, chemical abundances, sizes, ages, and masses of these groupings. We discuss separately the specific cases, when the gas extinction does not agree with the interstellar one. We assume that this is due to spatial offset of Hii clouds with respect to the related stellar population.We developed a method to estimate age of stellar population of the studied complexes using their morphology and the relation with associated H emission region. In result we obtained the estimates of chemical abundances for 80, masses for 63, and ages for 57 young objects observed in seven galaxies.

DARK MATTER CONTRACTION AND THE STELLAR CONTENT OF MASSIVE EARLY-TYPE GALAXIES: DISFAVORING 'LIGHT' INITIAL MASS FUNCTIONS

International Nuclear Information System (INIS)

Auger, M. W.; Treu, T.; Gavazzi, R.; Bolton, A. S.; Koopmans, L. V. E.; Marshall, P. J.

2010-01-01

We use stellar dynamics, strong lensing, stellar population synthesis models, and weak lensing shear measurements to constrain the dark matter (DM) profile and stellar mass in a sample of 53 massive early-type galaxies. We explore three DM halo models (unperturbed Navarro, Frenk, and White (NFW) halos and the adiabatic contraction models of Blumenthal and Gnedin) and impose a model for the relationship between the stellar and virial mass (i.e., a relationship for the star formation efficiency as a function of halo mass). We show that, given our model assumptions, the data clearly prefer a Salpeter-like initial mass function (IMF) over a lighter IMF (e.g., Chabrier or Kroupa), irrespective of the choice of DM halo. In addition, we find that the data prefer at most a moderate amount of adiabatic contraction (Blumenthal adiabatic contraction is strongly disfavored) and are only consistent with no adiabatic contraction (i.e., an NFW halo) if a mass-dependent IMF is assumed, in the sense of a more massive normalization of the IMF for more massive halos.

The Pan-STARRS1 medium-deep survey: The role of galaxy group environment in the star formation rate versus stellar mass relation and quiescent fraction out to z ∼ 0.8

Energy Technology Data Exchange (ETDEWEB)

Lin, Lihwai; Chen, Chin-Wei; Coupon, Jean; Hsieh, Bau-Ching [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan, R.O.C. (China); Jian, Hung-Yu [Department of Physics, National Taiwan University, Taipei 106, Taiwan, R.O.C. (China); Foucaud, Sebastien [Department of Earth Sciences, National Taiwan Normal University, N°88, Tingzhou Road, Sec. 4, Taipei 11677, Taiwan, R.O.C. (China); Norberg, Peder; Bower, R. G.; Cole, Shaun; Arnalte-Mur, Pablo; Draper, P. [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Heinis, Sebastien [Department of Astronomy, University of Maryland, MD 20742 (United States); Phleps, Stefanie [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, D-85748 Garching (Germany); Chen, Wen-Ping [Graduate Institute of Astronomy, National Central University, Chung-Li 32054, Taiwan, R.O.C. (China); Lee, Chien-Hsiu [University Observatory Munich, Scheinerstrasse 1, D-81679 Munich (Germany); Burgett, William; Chambers, K. C.; Denneau, L.; Flewelling, H.; Hodapp, K. W., E-mail: lihwailin@asiaa.sinica.edu.tw [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); and others

2014-02-10

Using a large optically selected sample of field and group galaxies drawn from the Pan-STARRS1 Medium-Deep Survey (PS1/MDS), we present a detailed analysis of the specific star formation rate (SSFR)—stellar mass (M {sub *}) relation, as well as the quiescent fraction versus M {sub *} relation in different environments. While both the SSFR and the quiescent fraction depend strongly on stellar mass, the environment also plays an important role. Using this large galaxy sample, we confirm that the fraction of quiescent galaxies is strongly dependent on environment at a fixed stellar mass, but that the amplitude and the slope of the star-forming sequence is similar between the field and groups: in other words, the SSFR-density relation at a fixed stellar mass is primarily driven by the change in the star-forming and quiescent fractions between different environments rather than a global suppression in the star formation rate for the star-forming population. However, when we restrict our sample to the cluster-scale environments (M > 10{sup 14} M {sub ☉}), we find a global reduction in the SSFR of the star-forming sequence of 17% at 4σ confidence as opposed to its field counterpart. After removing the stellar mass dependence of the quiescent fraction seen in field galaxies, the excess in the quiescent fraction due to the environment quenching in groups and clusters is found to increase with stellar mass, although deeper and larger data from the full PS1/MDS will be required to draw firm conclusions. We argue that these results are in favor of galaxy mergers to be the primary environment quenching mechanism operating in galaxy groups whereas strangulation is able to reproduce the observed trend in the environment quenching efficiency and stellar mass relation seen in clusters. Our results also suggest that the relative importance between mass quenching and environment quenching depends on stellar mass—the mass quenching plays a dominant role in producing quiescent

The Pan-STARRS1 medium-deep survey: The role of galaxy group environment in the star formation rate versus stellar mass relation and quiescent fraction out to z ∼ 0.8

International Nuclear Information System (INIS)

Lin, Lihwai; Chen, Chin-Wei; Coupon, Jean; Hsieh, Bau-Ching; Jian, Hung-Yu; Foucaud, Sebastien; Norberg, Peder; Bower, R. G.; Cole, Shaun; Arnalte-Mur, Pablo; Draper, P.; Heinis, Sebastien; Phleps, Stefanie; Chen, Wen-Ping; Lee, Chien-Hsiu; Burgett, William; Chambers, K. C.; Denneau, L.; Flewelling, H.; Hodapp, K. W.

2014-01-01

Using a large optically selected sample of field and group galaxies drawn from the Pan-STARRS1 Medium-Deep Survey (PS1/MDS), we present a detailed analysis of the specific star formation rate (SSFR)—stellar mass (M * ) relation, as well as the quiescent fraction versus M * relation in different environments. While both the SSFR and the quiescent fraction depend strongly on stellar mass, the environment also plays an important role. Using this large galaxy sample, we confirm that the fraction of quiescent galaxies is strongly dependent on environment at a fixed stellar mass, but that the amplitude and the slope of the star-forming sequence is similar between the field and groups: in other words, the SSFR-density relation at a fixed stellar mass is primarily driven by the change in the star-forming and quiescent fractions between different environments rather than a global suppression in the star formation rate for the star-forming population. However, when we restrict our sample to the cluster-scale environments (M > 10 14 M ☉ ), we find a global reduction in the SSFR of the star-forming sequence of 17% at 4σ confidence as opposed to its field counterpart. After removing the stellar mass dependence of the quiescent fraction seen in field galaxies, the excess in the quiescent fraction due to the environment quenching in groups and clusters is found to increase with stellar mass, although deeper and larger data from the full PS1/MDS will be required to draw firm conclusions. We argue that these results are in favor of galaxy mergers to be the primary environment quenching mechanism operating in galaxy groups whereas strangulation is able to reproduce the observed trend in the environment quenching efficiency and stellar mass relation seen in clusters. Our results also suggest that the relative importance between mass quenching and environment quenching depends on stellar mass—the mass quenching plays a dominant role in producing quiescent galaxies for more

SDSS-IV MaNGA: Star Formation Cessation in Low-redshift Galaxies. I. Dependence on Stellar Mass and Structural Properties

Science.gov (United States)

Wang, Enci; Li, Cheng; Xiao, Ting; Lin, Lin; Bershady, Matthew; Law, David R.; Merrifield, Michael; Sanchez, Sebastian F.; Riffel, Rogemar A.; Riffel, Rogerio; Yan, Renbin

2018-04-01

We investigate radial gradients in the recent star formation history (SFH) of 1917 galaxies with 0.01 < z < 0.14 from the Mapping Nearby Galaxies at Apache Point Observatory project. For each galaxy, we obtain two-dimensional maps and radial profiles for three spectroscopically measured parameters that are sensitive to the recent SFH: D n (4000) (the 4000 Å break), EW(Hδ A ), and EW(Hα) (the equivalent width of the Hδ absorption and the Hα emission line). The majority of the spaxels are consistent with models of a continuously declining star formation rate, indicating that starbursts occur rarely in local galaxies with regular morphologies. We classify the galaxies into three classes: fully star-forming (SF), partly quenched (PQ), and totally quenched (TQ). The galaxies that are less massive than 1010 M ⊙ present at most weak radial gradients in the diagnostic parameters. In contrast, massive galaxies with a stellar mass above 1010 M ⊙ present significant gradients in the three diagnostic parameters if they are classified as SF or PQ but show weak gradients in D n (4000) and EW(Hδ A ) and no gradients in EW(Hα) if they are in the TQ class. This implies the existence of a critical stellar mass (∼1010 M ⊙) above which the star formation in a galaxy is shut down from the inside out. Galaxies tend to evolve synchronously from the inner to the outer regions before their mass reaches the critical value. We have further divided the sample at a fixed mass by both bulge-to-total luminosity ratio and morphological type, finding that our conclusions hold regardless of these factors; it appears that the presence of a central dense object is not a driving parameter but rather a by-product of the star formation cessation process.

Estimatining biases in the stellar dynamical black hole mass measurements in barred galaxies and prospects for measuring SMBH masses with JWST

Science.gov (United States)

Valluri, Monica; Vasiliev, Eugene; Bentz, Misty; Shen, Juntai

2018-04-01

Although 60% of disk galaxies are barred, stellar dynamical measurements of the masses of supermassive black holes (SMBH) in barred galaxies have always been obtained under the assumption that the bulges are axisymmetric. We use N-body simulations with self-consistently grown SMBHs in barred and unbarred galaxies to create a suite of mock Integral Field Spectrographic (IFS) datasets for galaxies with various observed orientations. We then apply an axisymmetric orbit superposition code to these mock IFS datasets to assess the reliability with which SMBH masses can be recovered. We also assess which disk and bar orientations give rise to biases. We use these simulations to assess whether or not existing SMBH measurements in barred galaxies are likely to be biased. We also present a brief preview of our JWST Early Release Science proposal to study the nuclear dynamics of nearby Seyfert I galaxy NGC 4151 with the NIRSpec Integral Field Spectrograph and describe how simulations of disk galaxies will used to create mock NIRSpec data to prepare for the real data.

Introducing galactic structure finder: the multiple stellar kinematic structures of a simulated Milky Way mass galaxy

Science.gov (United States)

Obreja, Aura; Macciò, Andrea V.; Moster, Benjamin; Dutton, Aaron A.; Buck, Tobias; Wang, Gregory S. Stinson Liang

2018-04-01

We present the first results of applying Gaussian Mixture Models in the stellar kinematic space of normalized angular momentum and binding energy on NIHAO high resolution galaxies to separate the stars into multiple components. We exemplify this method using a simulated Milky Way analogue, whose stellar component hosts: thin and thick discs, classical and pseudo bulges, and a stellar halo. The properties of these stellar structures are in good agreement with observational expectations in terms of sizes, shapes and rotational support. Interestingly, the two kinematic discs show surface mass density profiles more centrally concentrated than exponentials, while the bulges and the stellar halo are purely exponential. We trace back in time the Lagrangian mass of each component separately to study their formation history. Between z ˜ 3 and the end of halo virialization, z ˜ 1.3, all components lose a fraction of their angular momentum. The classical bulge loses the most (˜95%) and the thin disc the least (˜60%). Both bulges formed their stars in-situ at high redshift, while the thin disc formed ˜98% in-situ, but with a constant SFR ˜ 1.5M⊙yr-1 over the last ˜ 11 Gyr. Accreted stars (6% of total stellar mass) are mainly incorporated to the thick disc or the stellar halo, which formed ex-situ 8% and 45% of their respective masses. Our analysis pipeline is freely available at https://github.com/aobr/gsf.

Do Low Surface Brightness Galaxies Host Stellar Bars?

International Nuclear Information System (INIS)

Cervantes Sodi, Bernardo; Sánchez García, Osbaldo

2017-01-01

With the aim of assessing if low surface brightness galaxies host stellar bars and by studying the dependence of the occurrence of bars as a function of surface brightness, we use the Galaxy Zoo 2 data set to construct a large volume-limited sample of galaxies and then segregate these galaxies as having low or high surface brightness in terms of their central surface brightness. We find that the fraction of low surface brightness galaxies hosting strong bars is systematically lower than that found for high surface brightness galaxies. The dependence of the bar fraction on the central surface brightness is mostly driven by a correlation of the surface brightness with the spin and the gas richness of the galaxies, showing only a minor dependence on the surface brightness. We also find that the length of the bars is strongly dependent on the surface brightness, and although some of this dependence is attributed to the gas content, even at a fixed gas-to-stellar mass ratio, high surface brightness galaxies host longer bars than their low surface brightness counterparts, which we attribute to an anticorrelation of the surface brightness with the spin.

Do Low Surface Brightness Galaxies Host Stellar Bars?

Energy Technology Data Exchange (ETDEWEB)

Cervantes Sodi, Bernardo; Sánchez García, Osbaldo, E-mail: b.cervantes@irya.unam.mx, E-mail: o.sanchez@irya.unam.mx [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Campus Morelia, A.P. 3-72, C.P. 58089 Michoacán, México (Mexico)

2017-09-20

With the aim of assessing if low surface brightness galaxies host stellar bars and by studying the dependence of the occurrence of bars as a function of surface brightness, we use the Galaxy Zoo 2 data set to construct a large volume-limited sample of galaxies and then segregate these galaxies as having low or high surface brightness in terms of their central surface brightness. We find that the fraction of low surface brightness galaxies hosting strong bars is systematically lower than that found for high surface brightness galaxies. The dependence of the bar fraction on the central surface brightness is mostly driven by a correlation of the surface brightness with the spin and the gas richness of the galaxies, showing only a minor dependence on the surface brightness. We also find that the length of the bars is strongly dependent on the surface brightness, and although some of this dependence is attributed to the gas content, even at a fixed gas-to-stellar mass ratio, high surface brightness galaxies host longer bars than their low surface brightness counterparts, which we attribute to an anticorrelation of the surface brightness with the spin.

BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES

Energy Technology Data Exchange (ETDEWEB)

El-Badry, Kareem; Geha, Marla [Department of Astronomy, Yale University, New Haven, CT (United States); Wetzel, Andrew; Hopkins, Philip F. [TAPIR, California Institute of Technology, Pasadena, CA USA (United States); Kereš, Dusan; Chan, T. K. [Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla (United States); Faucher-Giguère, Claude-André, E-mail: kareem.el-badry@yale.edu [Department of Physics and Astronomy and CIERA, Northwestern University, Evanston, IL (United States)

2016-04-01

We examine the effects of stellar feedback and bursty star formation on low-mass galaxies (M{sub star} = 2 × 10{sup 6} − 5 × 10{sup 10} M{sub ⊙}) using the Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized the impact of feedback on dark matter profiles, we investigate the impact on the stellar component: kinematics, radial migration, size evolution, and population gradients. Feedback-driven outflows/inflows drive significant radial stellar migration over both short and long timescales via two processes: (1) outflowing/infalling gas can remain star-forming, producing young stars that migrate ∼1 kpc within their first 100 Myr, and (2) gas outflows/inflows drive strong fluctuations in the global potential, transferring energy to all stars. These processes produce several dramatic effects. First, galaxies’ effective radii can fluctuate by factors of >2 over ∼200 Myr, and these rapid size fluctuations can account for much of the observed scatter in the radius at fixed M{sub star}. Second, the cumulative effects of many outflow/infall episodes steadily heat stellar orbits, causing old stars to migrate outward most strongly. This age-dependent radial migration mixes—and even inverts—intrinsic age and metallicity gradients. Thus, the galactic-archaeology approach of calculating radial star formation histories from stellar populations at z = 0 can be severely biased. These effects are strongest at M{sub star} ≈ 10{sup 7–9.6} M{sub ⊙}, the same regime where feedback most efficiently cores galaxies. Thus, detailed measurements of stellar kinematics in low-mass galaxies can strongly constrain feedback models and test baryonic solutions to small-scale problems in ΛCDM.

The ATLAS3D project - XX. Mass-size and mass-σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function

Science.gov (United States)

Cappellari, Michele; McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bois, Maxime; Bournaud, Frédéric; Bureau, M.; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

2013-07-01

In the companion Paper XV of this series, we derive accurate total mass-to-light ratios (M/L)_JAM≈ (M/L)({r}= {R_e}) within a sphere of radius r= {R_e} centred on the galaxy, as well as stellar (M/L)stars (with the dark matter removed) for the volume-limited and nearly mass-selected (stellar mass M_star ≳ 6× 10^9 { M_{⊙}}) ATLAS3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). Here, we use those parameters to study the two orthogonal projections ({M_JAM}, {σ _e}) and ({M_JAM}, {R_e^maj}) of the thin Mass Plane (MP) ({M_JAM}, {σ _e}, {R_e^maj}) which describes the distribution of the galaxy population, where {M_JAM}≡ L× (M/L)_JAM≈ M_star. The distribution of galaxy properties on both projections of the MP is characterized by: (i) the same zone of exclusion (ZOE), which can be transformed from one projection to the other using the scalar virial equation. The ZOE is roughly described by two power laws, joined by a break at a characteristic mass {M_JAM}≈ 3× 10^{10} { M_{⊙}}, which corresponds to the minimum Re and maximum stellar density. This results in a break in the mean {M_JAM}-{σ _e} relation with trends {M_JAM}∝ σ _e^{2.3} and {M_JAM}∝ σ _e^{4.7} at small and large σe, respectively; (ii) a characteristic mass {M_JAM}≈ 2× 10^{11} { M_{⊙}} which separates a population dominated by flat fast rotator with discs and spiral galaxies at lower masses, from one dominated by quite round slow rotators at larger masses; (iii) below that mass the distribution of ETGs' properties on the two projections of the MP tends to be constant along lines of roughly constant σe, or equivalently along lines with {R_e^maj}∝ {M_JAM}, respectively (or even better parallel to the ZOE: {R_e^maj}∝ M_JAM^{0.75}); (iv) it forms a continuous and parallel sequence with the distribution of spiral galaxies; (v) at even lower masses, the distribution of fast-rotator ETGs and late spirals naturally extends to that of dwarf ETGs (Sph

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

Energy Technology Data Exchange (ETDEWEB)

Hemmati, Shoubaneh; Mobasher, Bahram; Darvish, Behnam [University of California, Riverside, CA 92512 (United States); Nayyeri, Hooshang; Miller, Sarah [University of California, Irvine, CA 92697 (United States); Sobral, David, E-mail: shemm001@ucr.edu [Universidade de Lisboa, PT1349-018 Lisbon (Portugal)

2015-11-20

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

THE SL2S GALAXY-SCALE LENS SAMPLE. IV. THE DEPENDENCE OF THE TOTAL MASS DENSITY PROFILE OF EARLY-TYPE GALAXIES ON REDSHIFT, STELLAR MASS, AND SIZE

Energy Technology Data Exchange (ETDEWEB)

Sonnenfeld, Alessandro; Treu, Tommaso; Suyu, Sherry H. [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Gavazzi, Raphaël [Institut d' Astrophysique de Paris, UMR7095 CNRS-Université Pierre et Marie Curie, 98bis bd Arago, F-75014 Paris (France); Marshall, Philip J. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States); Auger, Matthew W. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Nipoti, Carlo, E-mail: sonnen@physics.ucsb.edu [Astronomy Department, University of Bologna, via Ranzani 1, I-40127 Bologna (Italy)

2013-11-10

We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in the redshift range z{sub d} = 0.2-0.8, while the lensed sources are at z{sub s} = 1-3.5. We combine these data with photometric and lensing measurements presented in the companion paper III and with lenses from the Sloan Lens Advanced Camera for Surveys and Lènses Structure and Dynamics surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. We study the dependence of the slope of the total mass density profile, γ' (ρ(r)∝r{sup -γ{sup '}}), on stellar mass, size, and redshift. We find that two parameters are sufficient to determine γ' with less than 6% residual scatter. At fixed redshift, γ' depends solely on the surface stellar mass density ∂γ'/∂Σ{sub *} = 0.38 ± 0.07, i.e., galaxies with denser stars also have steeper slopes. At fixed M{sub *} and R{sub eff}, γ' depends on redshift, in the sense that galaxies at a lower redshift have steeper slopes (∂γ'/∂z = –0.31 ± 0.10). However, the mean redshift evolution of γ' for an individual galaxy is consistent with zero dγ'/dz = –0.10 ± 0.12. This result is obtained by combining our measured dependencies of γ' on z, M{sub *},R{sub eff} with the evolution of the R{sub eff}-M{sub *} taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work.

THE SL2S GALAXY-SCALE LENS SAMPLE. IV. THE DEPENDENCE OF THE TOTAL MASS DENSITY PROFILE OF EARLY-TYPE GALAXIES ON REDSHIFT, STELLAR MASS, AND SIZE

International Nuclear Information System (INIS)

Sonnenfeld, Alessandro; Treu, Tommaso; Suyu, Sherry H.; Gavazzi, Raphaël; Marshall, Philip J.; Auger, Matthew W.; Nipoti, Carlo

2013-01-01

We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in the redshift range z d = 0.2-0.8, while the lensed sources are at z s = 1-3.5. We combine these data with photometric and lensing measurements presented in the companion paper III and with lenses from the Sloan Lens Advanced Camera for Surveys and Lènses Structure and Dynamics surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. We study the dependence of the slope of the total mass density profile, γ' (ρ(r)∝r -γ ' ), on stellar mass, size, and redshift. We find that two parameters are sufficient to determine γ' with less than 6% residual scatter. At fixed redshift, γ' depends solely on the surface stellar mass density ∂γ'/∂Σ * = 0.38 ± 0.07, i.e., galaxies with denser stars also have steeper slopes. At fixed M * and R eff , γ' depends on redshift, in the sense that galaxies at a lower redshift have steeper slopes (∂γ'/∂z = –0.31 ± 0.10). However, the mean redshift evolution of γ' for an individual galaxy is consistent with zero dγ'/dz = –0.10 ± 0.12. This result is obtained by combining our measured dependencies of γ' on z, M * ,R eff with the evolution of the R eff -M * taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work

DWARFS GOBBLING DWARFS: A STELLAR TIDAL STREAM AROUND NGC 4449 AND HIERARCHICAL GALAXY FORMATION ON SMALL SCALES

International Nuclear Information System (INIS)

Martínez-Delgado, David; Rix, Hans-Walter; Macciò, Andrea V.; Romanowsky, Aaron J.; Arnold, Jacob A.; Brodie, Jean P.; Jay Gabany, R.; Annibali, Francesca; Fliri, Jürgen; Zibetti, Stefano; Van der Marel, Roeland P.; Aloisi, Alessandra; Chonis, Taylor S.; Carballo-Bello, Julio A.; Gallego-Laborda, J.; Merrifield, Michael R.

2012-01-01

A candidate diffuse stellar substructure was previously reported in the halo of the nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination of deep integrated-light images from the BlackBird 0.5 m telescope, and high-resolution wide-field images from the 8 m Subaru Telescope, which resolve the nebulosity into a stream of red giant branch stars, and confirm its physical association with NGC 4449. The properties of the stream imply a massive dwarf spheroidal progenitor, which after complete disruption will deposit an amount of stellar mass that is comparable to the existing stellar halo of the main galaxy. The stellar mass ratio between the two galaxies is ∼1:50, while the indirectly measured dynamical mass ratio, when including dark matter, may be ∼1:10-1:5. This system may thus represent a 'stealth' merger, where an infalling satellite galaxy is nearly undetectable by conventional means, yet has a substantial dynamical influence on its host galaxy. This singular discovery also suggests that satellite accretion can play a significant role in building up the stellar halos of low-mass galaxies, and possibly in triggering their starbursts.

THE SL2S GALAXY-SCALE LENS SAMPLE. V. DARK MATTER HALOS AND STELLAR IMF OF MASSIVE EARLY-TYPE GALAXIES OUT TO REDSHIFT 0.8

Energy Technology Data Exchange (ETDEWEB)

Sonnenfeld, Alessandro; Treu, Tommaso [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Marshall, Philip J. [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS29, Stanford, CA 94309 (United States); Suyu, Sherry H. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Gavazzi, Raphaël [Institut d' Astrophysique de Paris, UMR7095 CNRS-Université Pierre et Marie Curie, 98bis bd Arago, F-75014 Paris (France); Auger, Matthew W. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Nipoti, Carlo, E-mail: sonnen@physics.ucsb.edu [Department of Physics and Astronomy, Bologna University, viale Berti-Pichat 6/2, I-40127 Bologna (Italy)

2015-02-20

We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the Strong Lensing Legacy Survey and Sloan ACS Lens Survey and combine the results with a hierarchical Bayesian inference method to measure the distribution of dark matter mass and stellar initial mass function (IMF) across the population of massive early-type galaxies. Lensing selection effects are taken into account. We find that the dark matter mass projected within the inner 5 kpc increases for increasing redshift, decreases for increasing stellar mass density, but is roughly constant along the evolutionary tracks of early-type galaxies. The average dark matter slope is consistent with that of a Navarro-Frenk-White profile, but is not well constrained. The stellar IMF normalization is close to a Salpeter IMF at log M {sub *} = 11.5 and scales strongly with increasing stellar mass. No dependence of the IMF on redshift or stellar mass density is detected. The anti-correlation between dark matter mass and stellar mass density supports the idea of mergers being more frequent in more massive dark matter halos.

LUMINOUS AND HIGH STELLAR MASS CANDIDATE GALAXIES AT z ≈ 8 DISCOVERED IN THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY

International Nuclear Information System (INIS)

Yan Haojing; Finkelstein, Steven L.; Huang, Kuang-Han; Ryan, Russell E.; Ferguson, Henry C.; Koekemoer, Anton M.; Grogin, Norman A.; Dickinson, Mark; Newman, Jeffrey A.; Somerville, Rachel S.; Davé, Romeel; Faber, S. M.; Papovich, Casey; Guo Yicheng; Giavalisco, Mauro; Lee, Kyoung-soo; Reddy, Naveen; Siana, Brian D.; Cooray, Asantha R.; Hathi, Nimish P.

2012-01-01

One key goal of the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey is to track galaxy evolution back to z ≈ 8. Its two-tiered ''wide and deep'' strategy bridges significant gaps in existing near-infrared surveys. Here we report on z ≈ 8 galaxy candidates selected as F105W-band dropouts in one of its deep fields, which covers 50.1 arcmin 2 to 4 ks depth in each of three near-infrared bands in the Great Observatories Origins Deep Survey southern field. Two of our candidates have J 1 mag brighter than any previously known F105W-dropouts. We derive constraints on the bright end of the rest-frame ultraviolet luminosity function of galaxies at z ≈ 8, and show that the number density of such very bright objects is higher than expected from the previous Schechter luminosity function estimates at this redshift. Another two candidates are securely detected in Spitzer Infrared Array Camera images, which are the first such individual detections at z ≈ 8. Their derived stellar masses are on the order of a few × 10 9 M ☉ , from which we obtain the first measurement of the high-mass end of the galaxy stellar mass function at z ≈ 8. The high number density of very luminous and very massive galaxies at z ≈ 8, if real, could imply a large stellar-to-halo mass ratio and an efficient conversion of baryons to stars at such an early time.

Eight luminous early-type galaxies in nearby pairs and sparse groups. I. Stellar populations spatially analysed

Science.gov (United States)

Rosa, D. A.; Milone, A. C.; Krabbe, A. C.; Rodrigues, I.

2018-06-01

We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may have interaction with another galaxy of similar mass. We have spatially measured luminosity-weighted averages of age, [M/H], [Fe/H], and [α /Fe] in the sample galaxies to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the well-established stellar population synthesis code starlight using semi-empirical simple stellar population models. Radial variations of luminosity- weighted means of age, [M/H], [Fe/H], and [α /Fe] were quantified up to half of the effective radius of each galaxy. We found trends between representative values of age, [M/H], [α /Fe], and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1-4 Gyr old stellar populations were quantified in IC 5328 and NGC 6758 as well as 4-8 Gyr old ones in NGC 5812. Extended gas is present in IC 5328, NGC 1052, NGC 1209, and NGC 6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are basically dominated by α -enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and [α /Fe] gradients are null and the [M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass cannot be discarded in the formation and evolution of early-type galaxies.

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

Energy Technology Data Exchange (ETDEWEB)

Levesque, Emily M. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado 389-UCB, Boulder, CO 80309 (United States); Leitherer, Claus, E-mail: Emily.Levesque@colorado.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2013-12-20

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

ULTRADEEP INFRARED ARRAY CAMERA OBSERVATIONS OF SUB-L* z ∼ 7 AND z ∼ 8 GALAXIES IN THE HUBBLE ULTRA DEEP FIELD: THE CONTRIBUTION OF LOW-LUMINOSITY GALAXIES TO THE STELLAR MASS DENSITY AND REIONIZATION

International Nuclear Information System (INIS)

Labbe, I.; Gonzalez, V.; Bouwens, R. J.; Illingworth, G. D.; Magee, D.; Oesch, P. A.; Carollo, C. M.; Van Dokkum, P. G.; Franx, M.; Stiavelli, M.; Trenti, M.; Kriek, M.

2010-01-01

We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z ∼ 7 z 850 -dropout galaxies and 5z ∼ 8 Y 105 -dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 μm and 4.5 μm. None of the galaxies are detected to [3.6] ∼ 26.9 (AB, 2σ), but a stacking analysis reveals a robust detection for the z 850 -dropouts and an upper limit for the Y 105 -dropouts. We construct average broadband spectral energy distributions using the stacked Advanced Camera for Surveys (ACS), WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z 850 -dropouts, we find z = 6.9 +0.1 -0.1 , (U - V) rest ∼ 0.4, reddening A V = 0, stellar mass (M*) = 1.2 +0.3 -0.6 x 10 9 M sun (Salpeter initial mass function). The best-fit ages ∼300 Myr, M/L V ∼ 0.2, and SSFR ∼1.7 Gyr -1 are similar to values reported for luminous z ∼ 7 galaxies, indicating the galaxies are smaller but not much younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7 +0.1 -0.2 Y 105 -dropouts have stellar masses that are uncertain by 1.5 dex due to the near-complete reliance on far-UV data. Adopting the 2σ upper limit on the M/L(z = 8), the stellar mass density to M UV,AB +1.4 -1.8 x 10 6 M sun Mpc -3 to ρ*(z = 8) 5 M sun Mpc -3 , following ∝(1 + z) -6 over 3 < z < 8. Lower masses at z = 8 would signify more dramatic evolution, which can be established with deeper IRAC observations, long before the arrival of the James Webb Space Telescope.

The hELENa project - I. Stellar populations of early-type galaxies linked with local environment and galaxy mass

Science.gov (United States)

Sybilska, A.; Lisker, T.; Kuntschner, H.; Vazdekis, A.; van de Ven, G.; Peletier, R.; Falcón-Barroso, J.; Vijayaraghavan, R.; Janz, J.

2017-09-01

We present the first in a series of papers in The role of Environment in shaping Low-mass Early-type Nearby galaxies (hELENa) project. In this paper, we combine our sample of 20 low-mass early types (dEs) with 258 massive early types (ETGs) from the ATLAS3D survey - all observed with the SAURON integral field unit - to investigate early-type galaxies' stellar population scaling relations and the dependence of the population properties on local environment, extended to the low-σ regime of dEs. The ages in our sample show more scatter at lower σ values, indicative of less massive galaxies being affected by the environment to a higher degree. The shape of the age-σ relations for cluster versus non-cluster galaxies suggests that cluster environment speeds up the placing of galaxies on the red sequence. While the scaling relations are tighter for cluster than for the field/group objects, we find no evidence for a difference in average population characteristics of the two samples. We investigate the properties of our sample in the Virgo cluster as a function of number density (rather than simple clustrocentric distance) and find that dE ages correlate with the local density such that galaxies in regions of lower density are younger, likely because they are later arrivals to the cluster or have experienced less pre-processing in groups, and consequently used up their gas reservoir more recently. Overall, dE properties correlate more strongly with density than those of massive ETGs, which was expected as less massive galaxies are more susceptible to external influences.

THE BLACK HOLE MASS, STELLAR MASS-TO-LIGHT RATIO, AND DARK HALO IN M87

International Nuclear Information System (INIS)

Gebhardt, Karl; Thomas, Jens

2009-01-01

We model the dynamical structure of M87 (NGC4486) using high spatial resolution long-slit observations of stellar light in the central regions, two-dimensional stellar light kinematics out to half of the effective radius, and globular cluster velocities out to eight effective radii. We simultaneously fit for four parameters: black hole mass, dark halo core radius, dark halo circular velocity, and stellar mass-to-light (M/L) ratio. We find a black hole mass of 6.4(±0.5) x 10 9 M sun (the uncertainty is 68% confidence marginalized over the other parameters). The stellar M/L V = 6.3 ± 0.8. The best-fit dark halo core radius is 14 ± 2 kpc, assuming a cored logarithmic potential. The best-fit dark halo circular velocity is 715 ± 15 km s -1 . Our black hole mass is over a factor of 2 larger than previous stellar dynamical measures, and our derived stellar M/L ratio is two times lower than previous dynamical measures. When we do not include a dark halo, we measure a black hole mass and stellar M/L ratio that is consistent with previous measures, implying that the major difference is in the model assumptions. The stellar M/L ratio from our models is very similar to that derived from stellar population models of M87. The reason for the difference in the black hole mass is because we allow the M/L ratio to change with radius. The dark halo is degenerate with the stellar M/L ratio, which is subsequently degenerate with the black hole mass. We argue that dynamical models of galaxies that do not include the contribution from a dark halo may produce a biased result for the black hole mass. This bias is especially large for a galaxy with a shallow light profile such as M87, and may not be as severe in galaxies with steeper light profiles unless they have a large stellar population change with radius.

Galaxy And Mass Assembly (GAMA): gas fuelling of spiral galaxies in the local Universe II. - direct measurement of the dependencies on redshift and host halo mass of stellar mass growth in central disc galaxies

Science.gov (United States)

Grootes, M. W.; Dvornik, A.; Laureijs, R. J.; Tuffs, R. J.; Popescu, C. C.; Robotham, A. S. G.; Liske, J.; Brown, M. J. I.; Holwerda, B. W.; Wang, L.

2018-06-01

We present a detailed analysis of the specific star formation rate-stellar mass (sSFR-M*) of z ≤ 0.13 disc central galaxies using a morphologically selected mass-complete sample (M* ≥ 109.5 M⊙). Considering samples of grouped and ungrouped galaxies, we find the sSFR-M* relations of disc-dominated central galaxies to have no detectable dependence on host dark-matter halo (DMH) mass, even where weak-lensing measurements indicate a difference in halo mass of a factor ≳ 5. We further detect a gradual evolution of the sSFR-M* relation of non-grouped (field) central disc galaxies with redshift, even over a Δz ≈ 0.04 (≈5 × 108 yr) interval, while the scatter remains constant. This evolution is consistent with extrapolation of the `main sequence of star-forming-galaxies' from previous literature that uses larger redshift baselines and coarser sampling. Taken together, our results present new constraints on the paradigm under which the SFR of galaxies is determined by a self-regulated balance between gas inflows and outflows, and consumption of gas by star formation in discs, with the inflow being determined by the product of the cosmological accretion rate and a fuelling efficiency - \\dot{M}_{b,halo}ζ. In particular, maintaining the paradigm requires \\dot{M}_{b,halo}ζ to be independent of the mass Mhalo of the host DMH. Furthermore, it requires the fuelling efficiency ζ to have a strong redshift dependence (∝(1 + z)2.7 for M* = 1010.3 M⊙ over z = 0-0.13), even though no morphological transformation to spheroids can be invoked to explain this in our disc-dominated sample. The physical mechanisms capable of giving rise to such dependencies of ζ on Mhalo and z for discs are unclear.

STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS

Energy Technology Data Exchange (ETDEWEB)

Santini, P.; Fontana, A.; Castellano, M.; Grazian, A.; Amorin, R. [INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monte Porzio Catone, Roma (Italy); Ferguson, H. C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Mobasher, B. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Barro, G. [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Finkelstein, S. L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Hsu, L. T.; Salvato, M.; Wuyts, S.; Galametz, A. [Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, D-85741 Garching (Germany); Lee, B. [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Lee, S.-K. [Center for the Exploration of the Origin of the Universe, Department of Physics and Astronomy, Seoul National University, Seoul (Korea, Republic of); Pforr, J. [National Optical Astronomy Observatories, 950 N Cherry Avenue, Tucson, AZ 85719 (United States); Wiklind, T. [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Almaini, O. [University of Nottingham, School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Cooper, M. C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Weiner, B., E-mail: paola.santini@oa-roma.inaf.it [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); and others

2015-03-10

We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. We combine the effort from 10 different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ∼80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age <100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for <20 Myr sources) if nebular contribution is ignored.

STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS

International Nuclear Information System (INIS)

Santini, P.; Fontana, A.; Castellano, M.; Grazian, A.; Amorin, R.; Ferguson, H. C.; Mobasher, B.; Barro, G.; Finkelstein, S. L.; Hsu, L. T.; Salvato, M.; Wuyts, S.; Galametz, A.; Lee, B.; Lee, S.-K.; Pforr, J.; Wiklind, T.; Almaini, O.; Cooper, M. C.; Weiner, B.

2015-01-01

We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. We combine the effort from 10 different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ∼80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age <100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for <20 Myr sources) if nebular contribution is ignored

Spitzer IRAC Confirmation of z850-Dropout Galaxies in the Hubble Ultra Deep Field: Stellar Masses and Ages at z ~ 7

Science.gov (United States)

Labbé, Ivo; Bouwens, Rychard; Illingworth, G. D.; Franx, M.

2006-10-01

Using Spitzer IRAC mid-infrared imaging from the Great Observatories Origins Deep Survey, we study z850-dropout sources in the Hubble Ultra Deep Field. After carefully removing contaminating flux from foreground sources, we clearly detect two z850 dropouts at 3.6 and 4.5 μm, while two others are marginally detected. The mid-infrared fluxes strongly support their interpretation as galaxies at z~7, seen when the universe was only 750 Myr old. The IRAC observations allow us for the first time to constrain the rest-frame optical colors, stellar masses, and ages of the highest redshift galaxies. Fitting stellar population models to the spectral energy distributions, we find photometric redshifts in the range 6.7-7.4, rest-frame colors U-V=0.2-0.4, V-band luminosities LV=(0.6-3)×1010 Lsolar, stellar masses (1-10)×109 Msolar, stellar ages 50-200 Myr, star formation rates up to ~25 Msolar yr-1, and low reddening AV~8, during the era of cosmic reionization, but the star formation rate density derived from their stellar masses and ages is not nearly sufficient to reionize the universe. The simplest explanation for this deficiency is that lower mass galaxies beyond our detection limit reionized the universe. Based on observations with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through contract 125790 issued by JPL/Caltech. Based on observations 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 NAS5-26555. Based on service mode observations collected at the European Southern Observatory, Paranal, Chile (ESO program 073.A-0764A).

PRIMUS: THE DEPENDENCE OF AGN ACCRETION ON HOST STELLAR MASS AND COLOR

Energy Technology Data Exchange (ETDEWEB)

Aird, James; Coil, Alison L.; Moustakas, John; Smith, M. Stephen M. [Center for Astrophysics and Space Sciences, Department of Physics, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093 (United States); Blanton, Michael R.; Zhu Guangtun [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Burles, Scott M. [D.E. Shaw and Co., L.P., 20400 Stevens Creek Blvd., Suite 850, Cupertino, CA 95014 (United States); Cool, Richard J. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States); Eisenstein, Daniel J. [Harvard College Observatory, 60 Garden St., Cambridge, MA 02138 (United States); Wong, Kenneth C. [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)

2012-02-10

We present evidence that the incidence of active galactic nuclei (AGNs) and the distribution of their accretion rates do not depend on the stellar masses of their host galaxies, contrary to previous studies. We use hard (2-10 keV) X-ray data from three extragalactic fields (XMM-LSS, COSMOS, and ELAIS-S1) with redshifts from the Prism Multi-object Survey to identify 242 AGNs with L{sub 2-10keV} = 10{sup 42-44} erg s{sup -1} within a parent sample of {approx}25,000 galaxies at 0.2 < z < 1.0 over {approx}3.4 deg{sup 2} and to i {approx} 23. We find that although the fraction of galaxies hosting an AGN at fixed X-ray luminosity rises strongly with stellar mass, the distribution of X-ray luminosities is independent of mass. Furthermore, we show that the probability that a galaxy will host an AGN can be defined by a universal Eddington ratio distribution that is independent of the host galaxy stellar mass and has a power-law shape with slope -0.65. These results demonstrate that AGNs are prevalent at all stellar masses in the range 9.5< log M{sub *}/M{sub sun}<12 and that the same physical processes regulate AGN activity in all galaxies in this stellar mass range. While a higher AGN fraction may be observed in massive galaxies, this is a selection effect related to the underlying Eddington ratio distribution. We also find that the AGN fraction drops rapidly between z {approx} 1 and the present day and is moderately enhanced (factor {approx}2) in galaxies with blue or green optical colors. Consequently, while AGN activity and star formation appear to be globally correlated, we do not find evidence that the presence of an AGN is related to the quenching of star formation or the color transformation of galaxies.

Ultradeep Infrared Array Camera Observations of Sub-L* z ~ 7 and z ~ 8 Galaxies in the Hubble Ultra Deep Field: the Contribution of Low-Luminosity Galaxies to the Stellar Mass Density and Reionization

Science.gov (United States)

Labbé, I.; González, V.; Bouwens, R. J.; Illingworth, G. D.; Oesch, P. A.; van Dokkum, P. G.; Carollo, C. M.; Franx, M.; Stiavelli, M.; Trenti, M.; Magee, D.; Kriek, M.

2010-01-01

We study the Spitzer Infrared Array Camera (IRAC) mid-infrared (rest-frame optical) fluxes of 14 newly WFC3/IR-detected z ~ 7 z 850-dropout galaxies and 5z ~ 8 Y 105-dropout galaxies. The WFC3/IR depth and spatial resolution allow accurate removal of contaminating foreground light, enabling reliable flux measurements at 3.6 μm and 4.5 μm. None of the galaxies are detected to [3.6] ≈ 26.9 (AB, 2σ), but a stacking analysis reveals a robust detection for the z 850-dropouts and an upper limit for the Y 105-dropouts. We construct average broadband spectral energy distributions using the stacked Advanced Camera for Surveys (ACS), WFC3, and IRAC fluxes and fit stellar population synthesis models to derive mean redshifts, stellar masses, and ages. For the z 850-dropouts, we find z = 6.9+0.1 -0.1, (U - V)rest ≈ 0.4, reddening AV = 0, stellar mass langM*rang = 1.2+0.3 -0.6 × 109 M sun (Salpeter initial mass function). The best-fit ages ~300 Myr, M/LV ≈ 0.2, and SSFR ~1.7 Gyr-1 are similar to values reported for luminous z ~ 7 galaxies, indicating the galaxies are smaller but not much younger. The sub-L* galaxies observed here contribute significantly to the stellar mass density and under favorable conditions may have provided enough photons for sustained reionization at 7 dropouts have stellar masses that are uncertain by 1.5 dex due to the near-complete reliance on far-UV data. Adopting the 2σ upper limit on the M/L(z = 8), the stellar mass density to M UV,AB Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #11563, 9797. Based on observations with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through contract 125790 issued by JPL/Caltech. Based on service mode observations collected at the European Southern Observatory, Paranal, Chile (ESO Program

REVISED MASS-TO-LIGHT RATIOS FOR NEARBY GALAXY GROUPS AND CLUSTERS

International Nuclear Information System (INIS)

Shan, Yutong; Courteau, Stéphane; McDonald, Michael

2015-01-01

We present a detailed investigation of the cluster stellar mass-to-light (M*/L) ratio and cumulative stellar masses, derived on a galaxy-by-galaxy basis, for 12 massive (M 500 ∼ 10 14 -10 15 M ☉ ), nearby clusters with available optical imaging data from the Sloan Digital Sky Survey Data Release 10 and X-ray data from the Chandra X-ray Observatory. Our method involves a statistical cluster membership using both photometric and spectroscopic redshifts when available to maximize completeness while minimizing contamination effects. We show that different methods of estimating the stellar mass-to-light ratio from observed photometry result in systematic discrepancies in the total stellar masses and average mass-to-light ratios of cluster galaxies. Nonetheless, all conversion methodologies point to a lack of correlation between M*/L i and total cluster mass, even though low-mass groups contain relatively more blue galaxies. We also find no statistically significant correlation between M*/L i and the fraction of blue galaxies (g – i < 0.85). For the mass range covered by our sample, the assumption of a Chabrier initial mass function (IMF) yields an integrated M*/L i ≅ 1.7 ± 0.2 M ☉ /L i, ☉ , a lower value than used in most similar studies, though consistent with the study of low-mass galaxy groups by Leauthaud et al. A light (diet) Salpeter IMF would imply a ∼60% increase in M*/L i

The Role of Stellar Feedback on the Structure of the ISM and Star Formation in Galaxies

Science.gov (United States)

Grisdale, Kearn Michael

2017-08-01

Stellar feedback refers to the injection of energy, momentum and mass into the interstellar medium (ISM) by massive stars. This feedback owes to a combination of ionising radiation, radiation pressure, stellar winds and supernovae and is likely responsible both for the inefficiency of star formation in galaxies, and the observed super-sonic turbulence of the ISM. In this thesis, I study how stellar feedback shapes the ISM thereby regulating galaxy evolution. In particular, I focus on three key questions: (i) How does stellar feedback shape the gas density distribution of the ISM? (ii) How does feedback change or influence the distribution of the kinetic energy in the ISM? and (iii) What role does feedback play in determining the star formation efficiency of giant molecular clouds (GMCs)? To answer these questions, I run high resolution (Deltax 4.6 pc) numerical simulations of three isolated galaxies, both with and without stellar feedback. I compare these simulations to observations of six galaxies from The HI Nearby Galaxy Survey (THINGS) using power spectra, and I use clump finding techniques to identify GMCs in my simulations and calculate their properties. I find that the kinetic energy power spectra in stellar feedback- regulated galaxies, regardless of the galaxy's mass and size, show scalings in excellent agreement with supersonic turbulence on scales below the thickness of the HI layer. I show that feedback influences the gas density field, and drives gas turbulence, up to large (kiloparsec) scales. This is in stark contrast to the density fields generated by large-scale gravity-only driven turbulence (i.e. without stellar feedback). Simulations with stellar feedback are able to reproduce the internal properties of GMCs such as: mass, size and velocity dispersion. Finally, I demonstrate that my simulations naturally reproduce the observed scatter (3.5-4 dex) in the star formation efficiency per free-fall time of GMCs, despite only employing a simple Schmidt

An Integrated Picture of Star Formation, Metallicity Evolution, and Galactic Stellar Mass Assembly

Science.gov (United States)

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

2008-10-01

We present an integrated study of star formation and galactic stellar mass assembly from z = 0.05 to 1.5 and galactic metallicity evolution from z = 0.05 to 0.9 using a very large and highly spectroscopically complete sample selected by rest-frame NIR bolometric flux in the GOODS-N. We assume a Salpeter IMF and fit Bruzual & Charlot models to compute the galactic stellar masses and extinctions. We determine the expected formed stellar mass density growth rates produced by star formation and compare them with the growth rates measured from the formed stellar mass functions by mass interval. We show that the growth rates match if the IMF is slightly increased from the Salpeter IMF at intermediate masses (~10 M⊙). We investigate the evolution of galaxy color, spectral type, and morphology with mass and redshift and the evolution of mass with environment. We find that applying extinction corrections is critical when analyzing galaxy colors; e.g., nearly all of the galaxies in the green valley are 24 μm sources, but after correcting for extinction, the bulk of the 24 μm sources lie in the blue cloud. We find an evolution of the metallicity-mass relation corresponding to a decrease of 0.21 +/- 0.03 dex between the local value and the value at z = 0.77 in the 1010-1011 M⊙ range. We use the metallicity evolution to estimate the gas mass of the galaxies, which we compare with the galactic stellar mass assembly and star formation histories. Overall, our measurements are consistent with a galaxy evolution process dominated by episodic bursts of star formation and where star formation in the most massive galaxies (gtrsim1011 M⊙) ceases at z Technology, the University of California, and NASA and was made possible by the generous financial support of the W. M. Keck Foundation.

Strong Stellar-driven Outflows Shape the Evolution of Galaxies at Cosmic Dawn

Energy Technology Data Exchange (ETDEWEB)

Fontanot, Fabio; De Lucia, Gabriella [INAF—Astronomical Observatory of Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Hirschmann, Michaela [Sorbonne Universités, UPMC-CNRS, UMR7095, Institut d’Astrophysique de Paris, F-75014 Paris (France)

2017-06-20

We study galaxy mass assembly and cosmic star formation rate (SFR) at high redshift (z ≳ 4), by comparing data from multiwavelength surveys with predictions from the GAlaxy Evolution and Assembly (gaea) model. gaea implements a stellar feedback scheme partially based on cosmological hydrodynamical simulations, which features strong stellar-driven outflows and mass-dependent timescales for the re-accretion of ejected gas. In previous work, we have shown that this scheme is able to correctly reproduce the evolution of the galaxy stellar mass function (GSMF) up to z ∼ 3. We contrast model predictions with both rest-frame ultraviolet (UV) and optical luminosity functions (LFs), which are mostly sensitive to the SFR and stellar mass, respectively. We show that gaea is able to reproduce the shape and redshift evolution of both sets of LFs. We study the impact of dust on the predicted LFs, and we find that the required level of dust attenuation is in qualitative agreement with recent estimates based on the UV continuum slope. The consistency between data and model predictions holds for the redshift evolution of the physical quantities well beyond the redshift range considered for the calibration of the original model. In particular, we show that gaea is able to recover the evolution of the GSMF up to z ∼ 7 and the cosmic SFR density up to z ∼ 10.

Strong Stellar-driven Outflows Shape the Evolution of Galaxies at Cosmic Dawn

International Nuclear Information System (INIS)

Fontanot, Fabio; De Lucia, Gabriella; Hirschmann, Michaela

2017-01-01

We study galaxy mass assembly and cosmic star formation rate (SFR) at high redshift (z ≳ 4), by comparing data from multiwavelength surveys with predictions from the GAlaxy Evolution and Assembly (gaea) model. gaea implements a stellar feedback scheme partially based on cosmological hydrodynamical simulations, which features strong stellar-driven outflows and mass-dependent timescales for the re-accretion of ejected gas. In previous work, we have shown that this scheme is able to correctly reproduce the evolution of the galaxy stellar mass function (GSMF) up to z ∼ 3. We contrast model predictions with both rest-frame ultraviolet (UV) and optical luminosity functions (LFs), which are mostly sensitive to the SFR and stellar mass, respectively. We show that gaea is able to reproduce the shape and redshift evolution of both sets of LFs. We study the impact of dust on the predicted LFs, and we find that the required level of dust attenuation is in qualitative agreement with recent estimates based on the UV continuum slope. The consistency between data and model predictions holds for the redshift evolution of the physical quantities well beyond the redshift range considered for the calibration of the original model. In particular, we show that gaea is able to recover the evolution of the GSMF up to z ∼ 7 and the cosmic SFR density up to z ∼ 10.

Galaxy and mass assembly (GAMA): the consistency of GAMA and WISE derived mass-to-light ratios

Science.gov (United States)

Kettlety, T.; Hesling, J.; Phillipps, S.; Bremer, M. N.; Cluver, M. E.; Taylor, E. N.; Bland-Hawthorn, J.; Brough, S.; De Propris, R.; Driver, S. P.; Holwerda, B. W.; Kelvin, L. S.; Sutherland, W.; Wright, A. H.

2018-01-01

Recent work has suggested that mid-IR wavelengths are optimal for estimating the mass-to-light ratios of stellar populations and hence the stellar masses of galaxies. We compare stellar masses deduced from spectral energy distribution (SED) models, fitted to multiwavelength optical-NIR photometry, to luminosities derived from WISE photometry in the W1 and W2 bands at 3.6 and 4.5 μm for non-star forming galaxies. The SED-derived masses for a carefully selected sample of low-redshift (z ≤ 0.15) passive galaxies agree with the prediction from stellar population synthesis models such that M*/LW1 ≃ 0.6 for all such galaxies, independent of other stellar population parameters. The small scatter between masses predicted from the optical SED and from the WISE measurements implies that random errors (as opposed to systematic ones such as the use of different initial mass functions) are smaller than previous, deliberately conservative, estimates for the SED fits. This test is subtly different from simultaneously fitting at a wide range of optical and mid-IR wavelengths, which may just generate a compromised fit: we are directly checking that the best-fitting model to the optical data generates an SED whose M*/LW1 is also consistent with separate mid-IR data. We confirm that for passive low-redshift galaxies a fixed M*/LW1 = 0.65 can generate masses at least as accurate as those obtained from more complex methods. Going beyond the mean value, in agreement with expectations from the models, we see a modest change in M*/LW1 with SED fitted stellar population age but an insignificant one with metallicity.

The ATLAS3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies

Science.gov (United States)

McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

2015-04-01

We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (MJAM, σe, R^maj_e), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 per cent of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>1010.5 M⊙), which themselves formed 90 per cent of their stars by z ˜ 2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions.

Spatially unresolved SED fitting can underestimate galaxy masses: a solution to the missing mass problem

Science.gov (United States)

Sorba, Robert; Sawicki, Marcin

2018-05-01

We perform spatially resolved, pixel-by-pixel Spectral Energy Distribution (SED) fitting on galaxies up to z ˜ 2.5 in the Hubble eXtreme Deep Field (XDF). Comparing stellar mass estimates from spatially resolved and spatially unresolved photometry we find that unresolved masses can be systematically underestimated by factors of up to 5. The ratio of the unresolved to resolved mass measurement depends on the galaxy's specific star formation rate (sSFR): at low sSFRs the bias is small, but above sSFR ˜ 10-9.5 yr-1 the discrepancy increases rapidly such that galaxies with sSFRs ˜ 10-8 yr-1 have unresolved mass estimates of only one-half to one-fifth of the resolved value. This result indicates that stellar masses estimated from spatially unresolved data sets need to be systematically corrected, in some cases by large amounts, and we provide an analytic prescription for applying this correction. We show that correcting stellar mass measurements for this bias changes the normalization and slope of the star-forming main sequence and reduces its intrinsic width; most dramatically, correcting for the mass bias increases the stellar mass density of the Universe at high redshift and can resolve the long-standing discrepancy between the directly measured cosmic SFR density at z ≳ 1 and that inferred from stellar mass densities (`the missing mass problem').

SDSS-IV MaNGA: Spatially resolved star formation histories in galaxies as a function of galaxy mass and type

Science.gov (United States)

Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo-Fernández, M.; Lian, J.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Storchi-Bergmann, T.; Schneider, D. P.

2017-04-01

We study the internal gradients of stellar population properties within 1.5 Re for a representative sample of 721 galaxies, with stellar masses ranging between 109 M⊙ and 1011.5 M⊙ from the SDSS-IV MaNGA Integral-Field-Unit survey. Through the use of our full spectral fitting code firefly, we derive light- and mass-weighted stellar population properties and their radial gradients, as well as full star formation and metal enrichment histories. We also quantify the impact that different stellar population models and full spectral fitting routines have on the derived stellar population properties and the radial gradient measurements. In our analysis, we find that age gradients tend to be shallow for both early-type and late-type galaxies. Mass-weighted age gradients of early-types arepositive (˜0.09 dex/Re) pointing to 'outside-in' progression of star formation, while late-type galaxies have negative light-weighted age gradients (˜-0.11 dex/Re), suggesting an 'inside-out' formation of discs. We detect negative metallicity gradients in both early- and late-type galaxies, but these are significantly steeper in late-types, suggesting that the radial dependence of chemical enrichment processes and the effect of gas inflow and metal transport are far more pronounced in discs. Metallicity gradients of both morphological classes correlate with galaxy mass, with negative metallicity gradients becoming steeper with increasing galaxy mass. The correlation with mass is stronger for late-type galaxies, with a slope of d(∇[Z/H])/d(log M) ˜ -0.2 ± 0.05 , compared to d(∇[Z/H])/d(log M) ˜ -0.05 ± 0.05 for early-types. This result suggests that the merger history plays a relatively small role in shaping metallicity gradients of galaxies.

The SAMI Galaxy Survey: Gravitational Potential and Surface Density Drive Stellar Populations. I. Early-type Galaxies

Science.gov (United States)

Barone, Tania M.; D’Eugenio, Francesco; Colless, Matthew; Scott, Nicholas; van de Sande, Jesse; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Cortese, Luca; Croom, Scott M.; Foster, Caroline; Goodwin, Michael; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; Lorente, Nuria P. F.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel N.

2018-03-01

The well-established correlations between the mass of a galaxy and the properties of its stars are considered to be evidence for mass driving the evolution of the stellar population (SP). However, for early-type galaxies (ETGs), we find that g ‑ i color and stellar metallicity [Z/H] correlate more strongly with gravitational potential Φ than with mass M, whereas SP age correlates best with surface density Σ. Specifically, for our sample of 625 ETGs with integral-field spectroscopy from the Sydney-AAO Multi-object Integral-field Galaxy Survey, compared to correlations with mass, the color–Φ, [Z/H]–Φ, and age–Σ relations show both a smaller scatter and a lower residual trend with galaxy size. For the star formation duration proxy [α/Fe], we find comparable results for trends with Φ and Σ, with both being significantly stronger than the [α/Fe]–M relation. In determining the strength of a trend, we analyze both the overall scatter, and the observational uncertainty on the parameters, in order to compare the intrinsic scatter in each correlation. These results lead us to the following inferences and interpretations: (1) the color–Φ diagram is a more precise tool for determining the developmental stage of the SP than the conventional color–mass diagram; and (2) gravitational potential is the primary regulator of global stellar metallicity, via its relation to the gas escape velocity. Furthermore, we propose the following two mechanisms for the age and [α/Fe] relations with Σ: (a) the age–Σ and [α/Fe]–Σ correlations arise as results of compactness-driven quenching mechanisms; and/or (b) as fossil records of the {{{Σ }}}SFR}\\propto {{{Σ }}}gas} relation in their disk-dominated progenitors.

THE REDSHIFT EVOLUTION OF THE RELATION BETWEEN STELLAR MASS, STAR FORMATION RATE, AND GAS METALLICITY OF GALAXIES

International Nuclear Information System (INIS)

Niino, Yuu

2012-01-01

We investigate the relation between stellar mass (M * ), star formation rate (SFR), and metallicity (Z) of galaxies, the so-called fundamental metallicity relation, in the galaxy sample of the Sloan Digital Sky Survey Data Release 7. We separate the galaxies into narrow redshift bins and compare the relation at different redshifts and find statistically significant (>99%) evolution. We test various observational effects that might cause seeming Z evolution and find it difficult to explain the evolution of the relation only by the observational effects. In the current sample of low-redshift galaxies, galaxies with different M * and SFR are sampled from different redshifts, and there is degeneracy between M * /SFR and redshift. Hence, it is not straightforward to distinguish a relation between Z and SFR from a relation between Z and redshift. The separation of the intrinsic relation from the redshift evolution effect is a crucial issue in the understanding of the evolution of galaxies.

Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disc morphology

Science.gov (United States)

Willett, Kyle W.; Schawinski, Kevin; Simmons, Brooke D.; Masters, Karen L.; Skibba, Ramin A.; Kaviraj, Sugata; Melvin, Thomas; Wong, O. Ivy; Nichol, Robert C.; Cheung, Edmond; Lintott, Chris J.; Fortson, Lucy

2015-05-01

We measure the stellar mass-star formation rate (SFR) relation in star-forming disc galaxies at z ≤ 0.085, using Galaxy Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disc, and show that both the slope and dispersion of the M⋆-SFR relation is constant when varying all the above parameters. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by ˜0.3 dex; this is significantly smaller than the increase seen in merging systems at z > 1. Of the galaxies lying significantly above the M⋆-SFR relation in the local Universe, more than 50 per cent are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

METALLICITY AND AGE OF THE STELLAR STREAM AROUND THE DISK GALAXY NGC 5907

Energy Technology Data Exchange (ETDEWEB)

Laine, Seppo; Grillmair, Carl J.; Capak, Peter [Spitzer Science Center-Caltech, MS 314-6, Pasadena, CA 91125 (United States); Arendt, Richard G. [CRESST/UMBC/NASA GSFC, Code 665, Greenbelt, MD 20771 (United States); Romanowsky, Aaron J. [Department of Physics and Astronomy, San José State University, One Washington Square, San Jose, CA 95192 (United States); Martínez-Delgado, David [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Ashby, Matthew L. N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Davies, James E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Majewski, Stephen R. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Brodie, Jean P.; Arnold, Jacob A. [University of California Observatories and Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); GaBany, R. Jay, E-mail: seppo@ipac.caltech.edu [Black Bird Observatory, 5660 Brionne Drive, San Jose, CA 95118 (United States)

2016-09-01

Stellar streams have become central to studies of the interaction histories of nearby galaxies. To characterize the most prominent parts of the stellar stream around the well-known nearby ( d  = 17 Mpc) edge-on disk galaxy NGC 5907, we have obtained and analyzed new, deep gri Subaru/Suprime-Cam and 3.6 μ m Spitzer /Infrared Array Camera observations. Combining the near-infrared 3.6 μ m data with visible-light images allows us to use a long wavelength baseline to estimate the metallicity and age of the stellar population along an ∼60 kpc long segment of the stream. We have fitted the stellar spectral energy distribution with a single-burst stellar population synthesis model and we use it to distinguish between the proposed satellite accretion and minor/major merger formation models of the stellar stream around this galaxy. We conclude that a massive minor merger (stellar mass ratio of at least 1:8) can best account for the metallicity of −0.3 inferred along the brightest parts of the stream.

The ATLAS(3D) project - XX. Mass-size and mass-Sigma distributions of early-type galaxies : bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function

NARCIS (Netherlands)

Cappellari, Michele; McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bois, Maxime; Bournaud, Frederic; Bureau, M.; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

2013-01-01

In the companion Paper XV of this series, we derive accurate total mass-to-light ratios (M/L)(JAM) approximate to (M/L)(r = R-e) within a sphere of radius r = R-e centred on the galaxy, as well as stellar (M/L)(stars) (with the dark matter removed) for the volume-limited and nearly mass-selected

Hot model of formation of galaxies: galaxy sizes and the origin of the stellar component

International Nuclear Information System (INIS)

Suchkov, A.A.

1988-01-01

Within the framework of the ''hot'' model of the formation of galaxies, a mechanism proposed is by which a protogalaxy transforms into a stellar system. It gives a quantitative relation between the mass and size of galaxy which well fits in with the observational relation; also it specifies two characteristic values of mass which coincide with masses of stars and globular clusters. It is shown that a ''hot protogalaxy'' (T ∼ 10 7 K) contracting under the gravity of a massive dark halo attains a critical size and fragments into separate clouds via thermal instability. The clouds form a collisionless system which collapses quasiadiabatically and reaches the equilibrium after its size decreases approximately by a factor of two. This defines the final zero of the system:R S ∼ 10 (M S /10 11 M sun ) 1/2 kpc. It is close to the sizes of elliptical galaxies and halos of spiral galaxies, and agree with the Faber-Jackson relation. The instability forms clouds with temperatures T c ' ∼ 10 4 K and T c ∼ (10-10 2 ) K. The sharp temperature and density change caused by the cloud formation leads to a sharp change of the Jeans mass. It value drops to M J ∼ 10 5 M sun for the clouds with T c ∼ 10 4 K, and to M J ' ∼ (10 -1 -10) M sun for the clouds with T c ' ∼ (10-10 2 ) K. This may explain why the mass spectrum of galactic objects is rather sharply peaked at two values corresponding to stellar mass and globular cluster mass

Lyα-EMITTING GALAXIES AT z = 2.1: STELLAR MASSES, DUST, AND STAR FORMATION HISTORIES FROM SPECTRAL ENERGY DISTRIBUTION FITTING

International Nuclear Information System (INIS)

Guaita, Lucia; Padilla, Nelson; Acquaviva, Viviana; Gawiser, Eric; Bond, Nicholas A.; Kurczynski, Peter; Ciardullo, Robin; Gronwall, Caryl; Treister, Ezequiel; Lira, Paulina; Schawinski, Kevin

2011-01-01

We study the physical properties of 216 z ≅ 2.1 Lyα-emitting galaxies (LAEs) discovered in an ultra-deep narrow- MUSYC image of the ECDF-S. We fit their stacked spectral energy distribution (SED) using Charlot and Bruzual templates. We consider star formation histories (SFHs) parameterized by the e-folding time parameter τ, allowing for exponentially decreasing (τ > 0), exponentially increasing (τ * /M sun ) = 8.6[8.4-9.1], E(B - V) = 0.22[0.00-0.31], τ = -0.02[(- 4)-18] Gyr, and age SF = 0.018[0.009-3] Gyr. Thus, we obtain robust measurements of low stellar mass and dust content, but we cannot place meaningful constraints on the age or SFH of the LAEs. We also calculate the instantaneous SFR to be 35[0.003-170] M sun yr -1 , with its average over the last 100 Myr before observation giving (SFR) 100 = 4[2-30] M sun yr -1 . When we compare the results for the same SFH, typical LAEs at z ≅ 2.1 appear dustier and show higher instantaneous SFRs than z ≅ 3.1 LAEs, while the observed stellar masses of the two samples seem consistent. Because the majority are low-mass galaxies, our typical LAEs appear to occupy the low-mass end of the distribution of star-forming galaxies at z ∼ 2. We perform SED fitting on several sub-samples selected based on photometric properties and find that LAE sub-samples at z ≅ 2.1 exhibit heterogeneous properties. The typical IRAC-bright, UV-bright, and red LAEs have the largest stellar mass and dust reddening. The typical UV-faint, IRAC-faint, and high EW LAE sub-samples appear less massive ( 9 M sun ) and less dusty, with E(B - V) consistent with zero.

The optimally sampled galaxy-wide stellar initial mass function. Observational tests and the publicly available GalIMF code

Science.gov (United States)

Yan, Zhiqiang; Jerabkova, Tereza; Kroupa, Pavel

2017-11-01

Here we present a full description of the integrated galaxy-wide initial mass function (IGIMF) theory in terms of the optimal sampling and compare it with available observations. Optimal sampling is the method we use to discretize the IMF deterministically into stellar masses. Evidence indicates that nature may be closer to deterministic sampling as observations suggest a smaller scatter of various relevant observables than random sampling would give, which may result from a high level of self-regulation during the star formation process. We document the variation of IGIMFs under various assumptions. The results of the IGIMF theory are consistent with the empirical relation between the total mass of a star cluster and the mass of its most massive star, and the empirical relation between the star formation rate (SFR) of a galaxy and the mass of its most massive cluster. Particularly, we note a natural agreement with the empirical relation between the IMF power-law index and the SFR of a galaxy. The IGIMF also results in a relation between the SFR of a galaxy and the mass of its most massive star such that, if there were no binaries, galaxies with SFR first time, we show optimally sampled galaxy-wide IMFs (OSGIMF) that mimic the IGIMF with an additional serrated feature. Finally, a Python module, GalIMF, is provided allowing the calculation of the IGIMF and OSGIMF dependent on the galaxy-wide SFR and metallicity. A copy of the python code model is 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/607/A126

GAMA/G10-COSMOS/3D-HST: the 0 history, stellar-mass, and dust-mass densities

Science.gov (United States)

Driver, Simon P.; Andrews, Stephen K.; da Cunha, Elisabete; Davies, Luke J.; Lagos, Claudia; Robotham, Aaron S. G.; Vinsen, Kevin; Wright, Angus H.; Alpaslan, Mehmet; Bland-Hawthorn, Joss; Bourne, Nathan; Brough, Sarah; Bremer, Malcolm N.; Cluver, Michelle; Colless, Matthew; Conselice, Christopher J.; Dunne, Loretta; Eales, Steve A.; Gomez, Haley; Holwerda, Benne; Hopkins, Andrew M.; Kafle, Prajwal R.; Kelvin, Lee S.; Loveday, Jon; Liske, Jochen; Maddox, Steve J.; Phillipps, Steven; Pimbblet, Kevin; Rowlands, Kate; Sansom, Anne E.; Taylor, Edward; Wang, Lingyu; Wilkins, Stephen M.

2018-04-01

We use the energy-balance code MAGPHYS to determine stellar and dust masses, and dust corrected star formation rates for over 200 000 GAMA galaxies, 170 000 G10-COSMOS galaxies, and 200 000 3D-HST galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous data set spanning a broad range in stellar-mass (108-1012 M⊙), dust-mass (106-109 M⊙), and star formation rates (0.01-100 M⊙yr-1), and over a broad redshift range (0.0 history (CSFH), the stellar-mass density (SMD), and the dust-mass density (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous data set using consistent mass and star formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our CSFH we precisely reproduce the SMD with an interstellar medium replenishment factor of 0.50 ± 0.07, consistent with our choice of Chabrier initial mass function plus some modest amount of stripped stellar mass. Exploring the cosmic dust density evolution, we find a gradual increase in dust density with lookback time. We build a simple phenomenological model from the CSFH to account for the dust-mass evolution, and infer two key conclusions: (1) For every unit of stellar mass which is formed 0.0065-0.004 units of dust mass is also formed. (2) Over the history of the Universe approximately 90-95 per cent of all dust formed has been destroyed and/or ejected.

The origin of ultra diffuse galaxies: stellar feedback and quenching

Science.gov (United States)

Chan, T. K.; Kereš, D.; Wetzel, A.; Hopkins, P. F.; Faucher-Giguère, C.-A.; El-Badry, K.; Garrison-Kimmel, S.; Boylan-Kolchin, M.

2018-05-01

We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies (UDGs). We show that outflows that dynamically heat galactic stars, together with a passively aging stellar population after imposed quenching, naturally reproduce the observed population of red UDGs, without the need for high spin halos, or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius and absolute magnitude of the observed red UDGs by quenching simulated galaxies at a range of different times. They represent a mostly uniform population of dark matter-dominated dwarf galaxies with M* ˜ 108 M⊙, low metallicity and a broad range of ages; the more massive the UDGs, the older they are. The most massive red UDG in our sample (M* ˜ 3 × 108M⊙) requires quenching at z ˜ 3 when its halo reached Mh ˜ 1011 M⊙. Our simulated UDGs form with normal stellar-to-halo ratios and match the central enclosed masses and the velocity dispersions of the observed UDGs. Enclosed masses remain largely fixed across a broad range of quenching times because the central regions of their dark matter halos complete their growth early. If our simulated dwarfs are not quenched, they evolve into bluer low-surface brightness galaxies with M/L similar to observed field dwarfs. While our simulation sample covers a limited range of formation histories and halo masses, we predict that UDG is a common, and perhaps even dominant, galaxy type around M* ˜ 108 M⊙, both in the field and in clusters.

TRACING THE EVOLUTION OF HIGH-REDSHIFT GALAXIES USING STELLAR ABUNDANCES

Energy Technology Data Exchange (ETDEWEB)

Crosby, Brian D.; O’Shea, Brian W. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Beers, Timothy C. [Department of Physics and JINA—Center for the Evolution of the Elements, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Tumlinson, Jason, E-mail: crosby.bd@gmail.com [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2016-03-20

This paper presents the first results from a model for chemical evolution that can be applied to N-body cosmological simulations and quantitatively compared to measured stellar abundances from large astronomical surveys. This model convolves the chemical yield sets from a range of stellar nucleosynthesis calculations (including asymptotic giant branch stars, Type Ia and II supernovae, and stellar wind models) with a user-specified stellar initial mass function (IMF) and metallicity to calculate the time-dependent chemical evolution model for a “simple stellar population” (SSP) of uniform metallicity and formation time. These SSP models are combined with a semianalytic model for galaxy formation and evolution that uses merger trees from N-body cosmological simulations to track several α- and iron-peak elements for the stellar and multiphase interstellar medium components of several thousand galaxies in the early (z ≥ 6) universe. The simulated galaxy population is then quantitatively compared to two complementary data sets of abundances in the Milky Way stellar halo and is capable of reproducing many of the observed abundance trends. The observed abundance ratio distributions are best reproduced with a Chabrier IMF, a chemically enriched star formation efficiency of 0.2, and a redshift of reionization of 7. Many abundances are qualitatively well matched by our model, but our model consistently overpredicts the carbon-enhanced fraction of stars at low metallicities, likely owing to incomplete coverage of Population III stellar yields and supernova models and the lack of dust as a component of our model.

STAR FORMATION RATES AND STELLAR MASSES OF z = 7-8 GALAXIES FROM IRAC OBSERVATIONS OF THE WFC3/IR EARLY RELEASE SCIENCE AND THE HUDF FIELDS

International Nuclear Information System (INIS)

Labbe, I.; Gonzalez, V.; Bouwens, R. J.; Illingworth, G. D.; Magee, D.; Franx, M.; Trenti, M.; Oesch, P. A.; Carollo, C. M.; Van Dokkum, P. G.; Stiavelli, M.; Kriek, M.

2010-01-01

We investigate the Spitzer/IRAC properties of 36 z ∼ 7 z 850 -dropout galaxies and three z ∼ 8 Y 098 galaxies derived from deep/wide-area WFC3/IR data of the Early Release Science, the ultradeep HUDF09, and wide-area NICMOS data. We fit stellar population synthesis models to the spectral energy distributions to derive mean redshifts, stellar masses, and ages. The z ∼ 7 galaxies are best characterized by substantial ages (>100 Myr) and M/L V ∼ 0.2. The main trend with decreasing luminosity is that of bluing of the far-UV slope from β ∼ -2.0 to β ∼ -3.0. This can be explained by decreasing metallicity, except for the lowest luminosity galaxies (0.1L* z =3 ), where low metallicity and smooth star formation histories (SFHs) fail to match the blue far-UV and moderately red H - [3.6] color. Such colors may require episodic SFHs with short periods of activity and quiescence ('on-off' cycles) and/or a contribution from emission lines. The stellar mass of our sample of z ∼ 7 star-forming galaxies correlates with star formation rate (SFR) according to log M* = 8.70(±0.09) + 1.06(±0.10)log SFR, implying that star formation may have commenced at z > 10. No galaxies are found with SFRs much higher or lower than the past averaged SFR suggesting that the typical star formation timescales are probably a substantial fraction of the Hubble time. We report the first IRAC detection of Y 098 -dropout galaxies at z ∼ 8. The average rest-frame U - V ∼ 0.3 (AB) of the three galaxies are similar to faint z ∼ 7 galaxies, implying similar M/L. The stellar mass density to M UV,AB +0.7 -1.0 x 10 6 M sun Mpc -3 , following log ρ*(z) = 10.6(±0.6) - 4.4(±0.7) log(1 + z) [M sun Mpc -3 ] over 3 < z < 8.

The stellar orbit distribution in present-day galaxies inferred from the CALIFA survey

Science.gov (United States)

Zhu, Ling; van de Ven, Glenn; Bosch, Remco van den; Rix, Hans-Walter; Lyubenova, Mariya; Falcón-Barroso, Jesús; Martig, Marie; Mao, Shude; Xu, Dandan; Jin, Yunpeng; Obreja, Aura; Grand, Robert J. J.; Dutton, Aaron A.; Macciò, Andrea V.; Gómez, Facundo A.; Walcher, Jakob C.; García-Benito, Rubén; Zibetti, Stefano; Sánchez, Sebastian F.

2018-03-01

Galaxy formation entails the hierarchical assembly of mass, along with the condensation of baryons and the ensuing, self-regulating star formation1,2. The stars form a collisionless system whose orbit distribution retains dynamical memory that can constrain a galaxy's formation history3. The orbits dominated by ordered rotation, with near-maximum circularity λz ≈ 1, are called kinematically cold, and the orbits dominated by random motion, with low circularity λz ≈ 0, are kinematically hot. The fraction of stars on `cold' orbits, compared with the fraction on `hot' orbits, speaks directly to the quiescence or violence of the galaxies' formation histories4,5. Here we present such orbit distributions, derived from stellar kinematic maps through orbit-based modelling for a well-defined, large sample of 300 nearby galaxies. The sample, drawn from the CALIFA survey6, includes the main morphological galaxy types and spans a total stellar mass range from 108.7 to 1011.9 solar masses. Our analysis derives the orbit-circularity distribution as a function of galaxy mass and its volume-averaged total distribution. We find that across most of the considered mass range and across morphological types, there are more stars on `warm' orbits defined as 0.25 ≤ λz ≤ 0.8 than on either `cold' or `hot' orbits. This orbit-based `Hubble diagram' provides a benchmark for galaxy formation simulations in a cosmological context.

Non-parametric cell-based photometric proxies for galaxy morphology: methodology and application to the morphologically defined star formation-stellar mass relation of spiral galaxies in the local universe

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Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Robotham, A. S. G.; Seibert, M.; Kelvin, L. S.

2014-02-01

We present a non-parametric cell-based method of selecting highly pure and largely complete samples of spiral galaxies using photometric and structural parameters as provided by standard photometric pipelines and simple shape fitting algorithms. The performance of the method is quantified for different parameter combinations, using purely human-based classifications as a benchmark. The discretization of the parameter space allows a markedly superior selection than commonly used proxies relying on a fixed curve or surface of separation. Moreover, we find structural parameters derived using passbands longwards of the g band and linked to older stellar populations, especially the stellar mass surface density μ* and the r-band effective radius re, to perform at least equally well as parameters more traditionally linked to the identification of spirals by means of their young stellar populations, e.g. UV/optical colours. In particular, the distinct bimodality in the parameter μ*, consistent with expectations of different evolutionary paths for spirals and ellipticals, represents an often overlooked yet powerful parameter in differentiating between spiral and non-spiral/elliptical galaxies. We use the cell-based method for the optical parameter set including re in combination with the Sérsic index n and the i-band magnitude to investigate the intrinsic specific star formation rate-stellar mass relation (ψ*-M*) for a morphologically defined volume-limited sample of local Universe spiral galaxies. The relation is found to be well described by ψ _* ∝ M_*^{-0.5} over the range of 109.5 ≤ M* ≤ 1011 M⊙ with a mean interquartile range of 0.4 dex. This is somewhat steeper than previous determinations based on colour-selected samples of star-forming galaxies, primarily due to the inclusion in the sample of red quiescent discs.

Kinematic scaling relations of CALIFA galaxies: A dynamical mass proxy for galaxies across the Hubble sequence.

Science.gov (United States)

Aquino-Ortíz, E.; Valenzuela, O.; Sánchez, S. F.; Hernández-Toledo, H.; Ávila-Reese, V.; van de Ven, G.; Rodríguez-Puebla, A.; Zhu, L.; Mancillas, B.; Cano-Díaz, M.; García-Benito, R.

2018-06-01

We used ionized gas and stellar kinematics for 667 spatially resolved galaxies publicly available from the Calar Alto Legacy Integral Field Area survey (CALIFA) 3rd Data Release with the aim of studying kinematic scaling relations as the Tully & Fisher (TF) relation using rotation velocity, Vrot, the Faber & Jackson (FJ) relation using velocity dispersion, σ, and also a combination of Vrot and σ through the SK parameter defined as SK^2 = KV_{rot}^2 + σ ^2 with constant K. Late-type and early-type galaxies reproduce the TF and FJ relations. Some early-type galaxies also follow the TF relation and some late-type galaxies the FJ relation, but always with larger scatter. On the contrary, when we use the SK parameter, all galaxies, regardless of the morphological type, lie on the same scaling relation, showing a tight correlation with the total stellar mass, M⋆. Indeed, we find that the scatter in this relation is smaller or equal to that of the TF and FJ relations. We explore different values of the K parameter without significant differences (slope and scatter) in our final results with respect the case K = 0.5 besides than a small change in the zero point. We calibrate the kinematic SK^2 dynamical mass proxy in order to make it consistent with sophisticated published dynamical models within 0.15 dex. We show that the SK proxy is able to reproduce the relation between the dynamical mass and the stellar mass in the inner regions of galaxies. Our result may be useful in order to produce fast estimations of the central dynamical mass in galaxies and to study correlations in large galaxy surveys.

Linking black hole growth with host galaxies: the accretion-stellar mass relation and its cosmic evolution

Science.gov (United States)

Yang, G.; Brandt, W. N.; Vito, F.; Chen, C.-T. J.; Trump, J. R.; Luo, B.; Sun, M. Y.; Xue, Y. Q.; Koekemoer, A. M.; Schneider, D. P.; Vignali, C.; Wang, J.-X.

2018-04-01

Previous studies suggest that the growth of supermassive black holes (SMBHs) may be fundamentally related to host-galaxy stellar mass (M⋆). To investigate this SMBH growth-M⋆ relation in detail, we calculate long-term SMBH accretion rate as a function of M⋆ and redshift [\\overlineBHAR(M_{\\star }, z)] over ranges of log (M⋆/M⊙) = 9.5-12 and z = 0.4-4. Our \\overlineBHAR(M_{\\star }, z) is constrained by high-quality survey data (GOODS-South, GOODS-North and COSMOS), and by the stellar mass function and the X-ray luminosity function. At a given M⋆, \\overlineBHAR is higher at high redshift. This redshift dependence is stronger in more massive systems [for log (M⋆/M⊙) ≈ 11.5, \\overlineBHAR is three decades higher at z = 4 than at z = 0.5], possibly due to AGN feedback. Our results indicate that the ratio between \\overlineBHAR and average star formation rate (\\overlineSFR) rises towards high M⋆ at a given redshift. This \\overlineBHAR/\\overlineSFR dependence on M⋆ does not support the scenario that SMBH and galaxy growth are in lockstep. We calculate SMBH mass history [MBH(z)] based on our \\overlineBHAR(M_{\\star }, z) and the M⋆(z) from the literature, and find that the MBH-M⋆ relation has weak redshift evolution since z ≈ 2. The MBH/M⋆ ratio is higher towards massive galaxies: it rises from ≈1/5000 at log M⋆ ≲ 10.5 to ≈1/500 at log M⋆ ≳ 11.2. Our predicted MBH/M⋆ ratio at high M⋆ is similar to that observed in local giant ellipticals, suggesting that SMBH growth from mergers is unlikely to dominate over growth from accretion.

Measuring the Stellar Masses of z ~ 7 Galaxies with the Spitzer UltRaFaint SUrvey Program (SURFS UP)

Science.gov (United States)

Ryan, R. E., Jr.; Gonzalez, A. H.; Lemaux, B. C.; Bradač, M.; Casertano, S.; Allen, S.; Cain, B.; Gladders, M.; Hall, N.; Hildebradt, H.; Hinz, J.; Huang, K.-H.; Lubin, L.; Schrabback, T.; Stiavelli, M.; Treu, T.; von der Linden, A.; Zaritsky, D.

2014-05-01

We present Spitzer/IRAC observations of nine z'-band dropouts highly magnified (2 ~ 7. By modeling the broadband photometry, we estimate the galaxy has an intrinsic star formation rate (SFR) of SFR ~ 1.3 M ⊙ yr-1 and stellar mass of M ~ 2.0 × 109 M ⊙, which gives a specific star formation rate of sSFR ~ 0.7 Gyr-1. If this galaxy had sustained this SFR since z ~ 20, it could have formed the observed stellar mass (to within a factor of ~2). We also discuss alternate star formation histories and argue that the exponentially increasing model is unlikely. Finally, based on the intrinsic SFR, we estimate that this galaxy has a likely [C II] flux of langf [C II]rang = 1.6 mJy. Observations were carried out using the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research is also 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 and NNX08AD79G. These observations are associated with programs Spitzer 3550, 60034, 90009, HST GO 10200, GO 10863, 11099, and 11591, and ESO Large Program 181.A-0485.

THE STRUCTURE AND STELLAR CONTENT OF THE OUTER DISKS OF GALAXIES: A NEW VIEW FROM THE Pan-STARRS1 MEDIUM DEEP SURVEY

Energy Technology Data Exchange (ETDEWEB)

Zheng, Zheng; Thilker, David A.; Heckman, Timothy M. [Department of Physics and Astronomy, Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218 (United States); Meurer, Gerhardt R. [International Center for Radio Astronomy Research, The University of Western Australia, M468, 35 StirlingHighway, Crawley, WA 6009 (Australia); Burgett, W. S.; Huber, M. E.; Kaiser, N.; Magnier, E. A.; Tonry, J. L.; Wainscoat, R. J.; Waters, C. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Chambers, K. C.; Metcalfe, N. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Price, P. A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2015-02-20

We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (grizy) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis spectral energy distribution fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of about twice Petrosian r {sub 90}, beyond which the halo light becomes significant. We measure normalized radial profiles for sub-samples of galaxies in three bins each of stellar mass and concentration. We also fit radial profiles to each galaxy. The majority of galaxies have down-bending radial surface brightness profiles in the bluer bands with a break radius at roughly r {sub 90}. However, they typically show single unbroken exponentials in the reddest bands and in the stellar surface mass density. We find that the mass/light ratio and stellar age radial profiles have a characteristic 'U' shape. There is a good correlation between the amplitude of the down-bend in the surface brightness profile and the rate of the increase in the M/L ratio in the outer disk. As we move from late- to early-type galaxies, the amplitude of the down-bend and the radial gradient in M/L both decrease. Our results imply a combination of stellar radial migration and suppression of recent star formation can account for the stellar populations of the outer disk.

M*/L gradients driven by IMF variation: large impact on dynamical stellar mass estimates

Science.gov (United States)

Bernardi, M.; Sheth, R. K.; Dominguez-Sanchez, H.; Fischer, J.-L.; Chae, K.-H.; Huertas-Company, M.; Shankar, F.

2018-06-01

Within a galaxy the stellar mass-to-light ratio ϒ* is not constant. Recent studies of spatially resolved kinematics of nearby early-type galaxies suggest that allowing for a variable initial mass function (IMF) returns significantly larger ϒ* gradients than if the IMF is held fixed. We show that ignoring such IMF-driven ϒ* gradients can have dramatic effect on dynamical (M_*^dyn), though stellar population (M_*^SP) based estimates of early-type galaxy stellar masses are also affected. This is because M_*^dyn is usually calibrated using the velocity dispersion measured in the central regions (e.g. Re/8) where stars are expected to dominate the mass (i.e. the dark matter fraction is small). On the other hand, M_*^SP is often computed from larger apertures (e.g. using a mean ϒ* estimated from colours). If ϒ* is greater in the central regions, then ignoring the gradient can overestimate M_*^dyn by as much as a factor of two for the most massive galaxies. Large ϒ*-gradients have four main consequences: First, M_*^dyn cannot be estimated independently of stellar population synthesis models. Secondly, if there is a lower limit to ϒ* and gradients are unknown, then requiring M_*^dyn=M_*^SP constrains them. Thirdly, if gradients are stronger in more massive galaxies, then accounting for this reduces the slope of the correlation between M_*^dyn/M_*^SP of a galaxy with its velocity dispersion. In particular, IMF-driven gradients bring M_*^dyn and M_*^SP into agreement, not by shifting M_*^SP upwards by invoking constant bottom-heavy IMFs, as advocated by a number of recent studies, but by revising M_*^dyn estimates in the literature downwards. Fourthly, accounting for ϒ* gradients changes the high-mass slope of the stellar mass function φ (M_*^dyn), and reduces the associated stellar mass density. These conclusions potentially impact estimates of the need for feedback and adiabatic contraction, so our results highlight the importance of measuring ϒ* gradients in

ON THE ORIGIN OF STELLAR MASSES

International Nuclear Information System (INIS)

Krumholz, Mark R.

2011-01-01

It has been a longstanding problem to determine, as far as possible, the characteristic masses of stars in terms of fundamental constants; the almost complete invariance of this mass as a function of the star-forming environment suggests that this should be possible. Here I provide such a calculation. The typical stellar mass is set by the characteristic fragment mass in a star-forming cloud, which depends on the cloud's density and temperature structure. Except in the very early universe, the latter is determined mainly by the radiation released as matter falls onto seed protostars. The energy yield from this process is ultimately set by the properties of deuterium burning in protostellar cores, which determines the stars' radii. I show that it is possible to combine these considerations to compute a characteristic stellar mass almost entirely in terms of fundamental constants, with an extremely weak residual dependence on the interstellar pressure and metallicity. This result not only explains the invariance of stellar masses, it resolves a second mystery: why fragmentation of a cold, low-density interstellar cloud, a process with no obvious dependence on the properties of nuclear reactions, happens to select a stellar mass scale such that stellar cores can ignite hydrogen. Finally, the weak residual dependence on the interstellar pressure and metallicity may explain recent observational hints of a smaller characteristic mass in the high-pressure, high-metallicity cores of giant elliptical galaxies.

The next generation of galaxy evolution models: A symbiosis of stellar populations and chemical abundances

Science.gov (United States)

Kotulla, Ralf

2012-10-01

Over its lifespan Hubble has invested significant effort into detailed observations of galaxies both in the local and distant universe. To extract the physical information from the observed {spectro-}photometry requires detailed and accurate models. Stellar population synthesis models are frequently used to obtain stellar masses, star formation rate, galaxy ages and star formation histories. Chemical evolution models offer another valuable and complementary approach to gain insight into many of the same aspects, yet these two methods have rarely been used in combination.Our proposed next generation of galaxy evolution models will help us improve our understanding of how galaxies form and evolve. Building on GALEV evolutionary synthesis models we incorporate state-of-the-art input physics for stellar evolution of binaries and rotating stars as well as new spectral libraries well matched to the modern observational capabilities. Our improved chemical evolution model allows us to self-consistently trace abundances of individual elements, fully accounting for the increasing initial abundances of successive stellar generations. GALEV will support variable Initial Mass Functions {IMF}, enabling us to test recent observational findings of a non-universal IMF by predicting chemical properties and integrated spectra in an integrated and consistent manner.HST is the perfect instrument for testing this approach. Its wide wavelength coverage from UV to NIR enables precise SED fitting, and with its spatial resolution we can compare the inferred chemical evolution to studies of star clusters and resolved stellar populations in nearby galaxies.

Galaxy And Mass Assembly (GAMA): deconstructing bimodality - I. Red ones and blue ones

Science.gov (United States)

Taylor, Edward N.; Hopkins, Andrew M.; Baldry, Ivan K.; Bland-Hawthorn, Joss; Brown, Michael J. I.; Colless, Matthew; Driver, Simon; Norberg, Peder; Robotham, Aaron S. G.; Alpaslan, Mehmet; Brough, Sarah; Cluver, Michelle E.; Gunawardhana, Madusha; Kelvin, Lee S.; Liske, Jochen; Conselice, Christopher J.; Croom, Scott; Foster, Caroline; Jarrett, Thomas H.; Lara-Lopez, Maritza; Loveday, Jon

2015-01-01

We measure the mass functions for generically red and blue galaxies, using a z 8.7 field galaxies from the Galaxy And Mass Assembly (GAMA) survey. Our motivation is that, as we show, the dominant uncertainty in existing measurements stems from how `red' and `blue' galaxies have been selected/defined. Accordingly, we model our data as two naturally overlapping populations, each with their own mass function and colour-mass relation, which enables us characterize the two populations without having to specify a priori which galaxies are `red' and `blue'. Our results then provide the means to derive objective operational definitions for the terms `red' and `blue', which are based on the phenomenology of the colour-mass diagrams. Informed by this descriptive modelling, we show that (1) after accounting for dust, the stellar colours of `blue' galaxies do not depend strongly on mass; (2) the tight, flat `dead sequence' does not extend much below log M* ˜ 10.5; instead, (3) the stellar colours of `red' galaxies vary rather strongly with mass, such that lower mass `red' galaxies have bluer stellar populations; (4) below log M* ˜ 9.3, the `red' population dissolves into obscurity, and it becomes problematic to talk about two distinct populations; as a consequence, (5) it is hard to meaningfully constrain the shape, including the existence of an upturn, of the `red' galaxy mass function below log M* ˜ 9.3. Points 1-4 provide meaningful targets for models of galaxy formation and evolution to aim for.

Implications of Stellar Feedback for Dynamical Modeling of the Milky Way and Dwarf Galaxies

Science.gov (United States)

Wetzel, Andrew

2018-04-01

I will present recent results on dynamical modeling of stellar populations from the FIRE cosmological zoom-in baryonic simulations of Milky Way-like and dwarf galaxies. First, I will discuss the dynamical formation of the Milky Way, including the origin of thin+thick stellar disk morphology. I also will discuss the curious origin of metal-rich stars on halo-like orbits near the Sun, as recently measured by Gaia, with new insights from FIRE simulations on stellar radial migration/heating. Next, I will discuss role of stellar feedback in generating non-equilibrium fluctuations of the gravitational potential in low-mass 'dwarf' galaxies, which can explain the origin of cores in their dark-matter density profiles. In particular, we predict significant observable effects on stellar dynamics, including radial migration, size fluctuations, and population gradients, which can provide observational tests of feedback-driven core formation. Finally, this scenario can explain the formation of newly discovered 'ultra-diffuse' galaxies.

THE STAR FORMATION HISTORIES OF RED-SEQUENCE GALAXIES, MASS-TO-LIGHT RATIOS AND THE FUNDAMENTAL PLANE

International Nuclear Information System (INIS)

Allanson, Steven P.; Hudson, Michael J.; Smith, Russell J.; Lucey, John R.

2009-01-01

This paper addresses the challenge of understanding the typical star formation histories of red-sequence galaxies, using linestrength indices and mass-to-light ratios as complementary constraints on their stellar age distribution. We first construct simple parametric models of the star formation history that bracket a range of scenarios, and fit these models to the linestrength indices of low-redshift cluster red-sequence galaxies. For giant galaxies, we confirm the downsizing trend, i.e., the stellar populations are younger, on average, for lower σ galaxies. We find, however, that this trend flattens or reverses at σ ∼ -1 . We then compare predicted stellar mass-to-light ratios with dynamical mass-to-light ratios derived from the fundamental plane (FP), or by the SAURON group. For galaxies with σ ∼ 70 km s -1 , models with a late 'frosting' of young stars and models with exponential star formation histories have stellar mass-to-light ratios that are larger than observed dynamical mass-to-light ratios by factors of 1.7 and 1.4, respectively, and so are rejected. The single stellar population (SSP) model is consistent with the FP, and requires a modest amount of dark matter (between 20% and 30%) to account for the difference between stellar and dynamical mass-to-light ratios. A model in which star formation was 'quenched' at intermediate ages is also consistent with the observations, although in this case less dark matter is required for low mass galaxies. We also find that the contribution of stellar populations to the 'tilt' of the fundamental plane is highly dependent on the assumed star formation history: for the SSP model, the tilt of the FP is driven primarily by stellar-population effects. For a quenched model, two-thirds of the tilt is due to stellar populations and only one-third is due to dark matter or non-homology.

THE STELLAR INITIAL MASS FUNCTION AT 0.9 < z < 1.5

Energy Technology Data Exchange (ETDEWEB)

Martín-Navarro, Ignacio; Trujillo, Ignacio; Vazdekis, Alexandre [Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, E38205 - La Laguna, Tenerife (Spain); Pérez-González, Pablo G.; Esquej, Pilar; Sánchez, Helena Domínguez; Espino, Néstor [Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Barro, Guillermo [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Bruzual, Gustavo [Centro de Radioastronomía y Astrofísica, UNAM, Campus Morelia, México (Mexico); Charlot, Stéphane [UPMC-CNRS, UMR7095, Institut d' Astrophysique de Paris, F-75014 Paris (France); Cava, Antonio [Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix (Switzerland); Ferreras, Ignacio [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom); Barbera, Francesco La [INAF-Osservatorio Astronomico di Capodimonte, Napoli (Italy); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Cenarro, A. Javier, E-mail: imartin@iac [Centro de Estudios de Física del Cosmos de Aragǿn, Plaza San Juan 1, E-44001 Teruel (Spain)

2015-01-01

We explore the stellar initial mass function (IMF) of a sample of 49 massive quiescent galaxies (MQGs) at 0.9 < z < 1.5. We base our analysis on intermediate resolution spectro-photometric data in the GOODS-N field taken in the near-infrared and optical with the Hubble Space Telescope Wide Field Camera 3 G141 grism and the Survey for High-z Absorption Red and Dead Sources. To constrain the slope of the IMF, we have measured the TiO{sub 2} spectral feature, whose strength depends strongly on the content of low-mass stars, as well as on stellar age. Using ultraviolet to near-infrared individual and stacked spectral energy distributions, we have independently estimated the stellar ages of our galaxies. Knowing the age of the stellar population, we interpret the strong differences in the TiO{sub 2} feature as an IMF variation. In particular, for the heaviest z ∼ 1 MQGs (M > 10{sup 11} M {sub ☉}), we find an average age of 1.7 ± 0.3 Gyr and a bottom-heavy IMF (Γ {sub b} = 3.2 ± 0.2). Lighter MQGs (2 × 10{sup 10} < M < 10{sup 11} M {sub ☉}) at the same redshift are younger on average (1.0 ± 0.2 Gyr) and present a shallower IMF slope (Γ{sub b}=2.7{sub −0.4}{sup +0.3}). Our results are in good agreement with the findings about the IMF slope in early-type galaxies of similar mass in the present-day universe. This suggests that the IMF, a key characteristic of the stellar populations in galaxies, is bottom-heavier for more massive galaxies and has remained unchanged in the last ∼8 Gyr.

The Metallicity Evolution of Low Mass Galaxies: New Contraints at Intermediate Redshift

Science.gov (United States)

Henry, Alaina; Martin, Crystal L.; Finlator, Kristian; Dressler, Alan

2013-01-01

We present abundance measurements from 26 emission-line-selected galaxies at z approx. 0.6-0.7. By reaching stellar masses as low as 10(exp 8) M stellar mass, these observations provide the first measurement of the intermediate-redshift mass-metallicity (MZ) relation below 10(exp 9)M stellar mass. For the portion of our sample above M is greater than 10(exp 9)M (8/26 galaxies), we find good agreement with previous measurements of the intermediate-redshift MZ relation. Compared to the local relation, we measure an evolution that corresponds to a 0.12 dex decrease in oxygen abundances at intermediate redshifts. This result confirms the trend that metallicity evolution becomes more significant toward lower stellar masses, in keeping with a downsizing scenario where low-mass galaxies evolve onto the local MZ relation at later cosmic times. We show that these galaxies follow the local fundamental metallicity relation, where objects with higher specific (mass-normalized) star formation rates (SFRs) have lower metallicities. Furthermore, we show that the galaxies in our sample lie on an extrapolation of the SFR-M* relation (the star-forming main sequence). Leveraging the MZ relation and star-forming main sequence (and combining our data with higher-mass measurements from the literature), we test models that assume an equilibrium between mass inflow, outflow, and star formation.We find that outflows are required to describe the data. By comparing different outflow prescriptions, we show that momentum, driven winds can describe the MZ relation; however, this model underpredicts the amount of star formation in low-mass galaxies. This disagreement may indicate that preventive feedback from gas heating has been overestimated, or it may signify a more fundamental deviation from the equilibrium assumption.

Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

International Nuclear Information System (INIS)

Khosroshahi, Habib G.; Raouf, Mojtaba; Miraghaei, Halime; Brough, Sarah; Croton, Darren J.; Graham, Alister; Driver, Simon; Baldry, Ivan; Brown, Michael; Prescott, Matt; Wang, Lingyu

2017-01-01

We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.

Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

Energy Technology Data Exchange (ETDEWEB)

Khosroshahi, Habib G.; Raouf, Mojtaba; Miraghaei, Halime [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5746 (Iran, Islamic Republic of); Brough, Sarah [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Croton, Darren J.; Graham, Alister [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia); Driver, Simon [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Baldry, Ivan [Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Brown, Michael [School of Physics, Monash University, Clayton, VIC 3800 (Australia); Prescott, Matt [Astrophysics Group, The University of Western Cape, Robert Sobukwe Road, Bellville 7530 (South Africa); Wang, Lingyu, E-mail: habib@ipm.ir [SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen (Netherlands)

2017-06-20

We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.

Black Hole Growth Is Mainly Linked to Host-galaxy Stellar Mass Rather Than Star Formation Rate

Science.gov (United States)

Yang, G.; Chen, C.-T. J.; Vito, F.; Brandt, W. N.; Alexander, D. M.; Luo, B.; Sun, M. Y.; Xue, Y. Q.; Bauer, F. E.; Koekemoer, A. M.; Lehmer, B. D.; Liu, T.; Schneider, D. P.; Shemmer, O.; Trump, J. R.; Vignali, C.; Wang, J.-X.

2017-06-01

We investigate the dependence of black hole accretion rate (BHAR) on host-galaxy star formation rate (SFR) and stellar mass (M *) in the CANDELS/GOODS-South field in the redshift range of 0.5≤slant zteam through spectral energy distribution fitting. The average BHAR is correlated positively with both SFR and M *, and the BHAR-SFR and BHAR-M * relations can both be described acceptably by linear models with a slope of unity. However, BHAR appears to be correlated more strongly with M * than SFR. This result indicates that M * is the primary host-galaxy property related to supermassive black hole (SMBH) growth, and the apparent BHAR-SFR relation is largely a secondary effect due to the star-forming main sequence. Among our sources, massive galaxies ({M}* ≳ {10}10{M}⊙ ) have significantly higher BHAR/SFR ratios than less massive galaxies, indicating that the former have higher SMBH fueling efficiency and/or higher SMBH occupation fraction than the latter. Our results can naturally explain the observed proportionality between {M}{BH} and M * for local giant ellipticals and suggest that their {M}{BH}/{M}* is higher than that of local star-forming galaxies. Among local star-forming galaxies, massive systems might have higher {M}{BH}/{M}* compared to dwarfs.

Old stellar populations how to study the fossil record of galaxy formation

CERN Document Server

Cassisi, Santi

2013-01-01

The book discusses the theoretical path to decoding the information gathered from observations of old stellar systems. It focuses on old stellar systems because these are the fossil record of galaxy formation and provide invaluable information ont he evolution of cosmic structures and the universe as a whole. The aim is to present results obtained in the past few years for theoretical developments in low mass star research and in advances in our knowledge of the evolution of old stellar systems. A particularly representative case is the recent discovery of multiple stellar populations in galac

Rate of stellar collapses in the Galaxy

International Nuclear Information System (INIS)

Lande, K.; Stephens, W.E.

1977-01-01

From an analysis of pulsar spatial and luminosity distributions, the number density of observed pulsars in the local region is determined to be 1.1+-0.4x10 -7 pulsar pc -3 . Multiplication by the detection factor and by the ratio of Galaxy mass to local matter density and division by a mean lifetime of pulsars of 3x10 6 yr suggests a pulsar birth every 4 yr. A stellar collapse might occur even more often. (Auth.)

Ultraviolet photometry of stellar populations in galaxies

International Nuclear Information System (INIS)

Deharveng, J.M.

1981-01-01

The UV flux of stellar populations, which is essentially emitted by young stars, conveys information on the process of star formation and its recent history. However, the evaluation of the flux arising from the young stellar component may be difficult. In the case of late type galaxies it is hampered by the extinction and the effect of scattered stellar radiation. In the case of early type galaxies, the star formation, if any, has to be disentangled from the contribution of hot evolved stars and of a possible 'active' phenomenon. A review of observations and results relevant two cases is presented [fr

CONNECTION BETWEEN DYNAMICALLY DERIVED INITIAL MASS FUNCTION NORMALIZATION AND STELLAR POPULATION PARAMETERS

International Nuclear Information System (INIS)

McDermid, Richard M.; Cappellari, Michele; Bayet, Estelle; Bureau, Martin; Davies, Roger L.; Alatalo, Katherine; Blitz, Leo; Bois, Maxime; Bournaud, Frédéric; Duc, Pierre-Alain; Crocker, Alison F.; Davis, Timothy A.; De Zeeuw, P. T.; Emsellem, Eric; Kuntschner, Harald; Khochfar, Sadegh; Krajnović, Davor; Morganti, Raffaella; Oosterloo, Tom; Naab, Thorsten

2014-01-01

We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS 3D project. We study trends between our dynamically derived IMF normalization α dyn ≡ (M/L) stars /(M/L) Salp and absorption line strengths, and interpret these via single stellar population-equivalent ages, abundance ratios (measured as [α/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalization of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of α dyn at a given population parameter. As a result, we find weak α dyn -[α/Fe] and α dyn –Age correlations and no significant α dyn –[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalization via the low-mass star demographics inferred through stellar spectral analysis

Connection between Dynamically Derived Initial Mass Function Normalization and Stellar Population Parameters

Science.gov (United States)

McDermid, Richard M.; Cappellari, Michele; Alatalo, Katherine; Bayet, Estelle; Blitz, Leo; Bois, Maxime; Bournaud, Frédéric; Bureau, Martin; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

2014-09-01

We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS3D project. We study trends between our dynamically derived IMF normalization αdyn ≡ (M/L)stars/(M/L)Salp and absorption line strengths, and interpret these via single stellar population-equivalent ages, abundance ratios (measured as [α/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalization of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of αdyn at a given population parameter. As a result, we find weak αdyn-[α/Fe] and αdyn -Age correlations and no significant αdyn -[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalization via the low-mass star demographics inferred through stellar spectral analysis.

GAS REGULATION OF GALAXIES: THE EVOLUTION OF THE COSMIC SPECIFIC STAR FORMATION RATE, THE METALLICITY-MASS-STAR-FORMATION RATE RELATION, AND THE STELLAR CONTENT OF HALOS

Energy Technology Data Exchange (ETDEWEB)

Lilly, Simon J.; Carollo, C. Marcella; Pipino, Antonio; Peng Yingjie [Institute for Astronomy, Department of Physics, ETH Zurich, CH-8093 Zurich (Switzerland); Renzini, Alvio [Department of Physics and Astronomy Galileo Galilei, Universita degli Studi di Padova, via Marzolo 8, I-35131 Padova (Italy)

2013-08-01

A very simple physical model of galaxies is one in which the formation of stars is instantaneously regulated by the mass of gas in a reservoir with mass loss scaling with the star-formation rate (SFR). This model links together three different aspects of the evolving galaxy population: (1) the cosmic time evolution of the specific star-formation rate (sSFR) relative to the growth of halos, (2) the gas-phase metallicities across the galaxy population and over cosmic time, and (3) the ratio of the stellar to dark matter mass of halos. The gas regulator is defined by the gas consumption timescale ({epsilon}{sup -1}) and the mass loading {lambda} of the wind outflow {lambda}{center_dot}SFR. The simplest regulator, in which {epsilon} and {lambda} are constant, sets the sSFR equal to exactly the specific accretion rate of the galaxy; more realistic situations lead to an sSFR that is perturbed from this precise relation. Because the gas consumption timescale is shorter than the timescale on which the system evolves, the metallicity Z is set primarily by the instantaneous operation of the regulator system rather than by the past history of the system. The metallicity of the gas reservoir depends on {epsilon}, {lambda}, and sSFR, and the regulator system therefore naturally produces a Z(m{sub star}, SFR) relation if {epsilon} and {lambda} depend on the stellar mass m{sub star}. Furthermore, this relation will be the same at all epochs unless the parameters {epsilon} and {lambda} themselves change with time. A so-called fundamental metallicity relation is naturally produced by these conditions. The overall mass-metallicity relation Z(m{sub star}) directly provides the fraction f{sub star}(m{sub star}) of incoming baryons that are being transformed into stars. The observed Z(m{sub star}) relation of Sloan Digital Sky Survey (SDSS) galaxies implies a strong dependence of stellar mass on halo mass that reconciles the different faint-end slopes of the stellar and halo mass

Star Formation Rates and Stellar Masses of z = 7-8 Galaxies from IRAC Observations of the WFC3/IR Early Release Science and the HUDF Fields

Science.gov (United States)

Labbé, I.; González, V.; Bouwens, R. J.; Illingworth, G. D.; Franx, M.; Trenti, M.; Oesch, P. A.; van Dokkum, P. G.; Stiavelli, M.; Carollo, C. M.; Kriek, M.; Magee, D.

2010-06-01

We investigate the Spitzer/IRAC properties of 36 z ~ 7 z 850-dropout galaxies and three z ~ 8 Y 098 galaxies derived from deep/wide-area WFC3/IR data of the Early Release Science, the ultradeep HUDF09, and wide-area NICMOS data. We fit stellar population synthesis models to the spectral energy distributions to derive mean redshifts, stellar masses, and ages. The z ~ 7 galaxies are best characterized by substantial ages (>100 Myr) and M/LV ≈ 0.2. The main trend with decreasing luminosity is that of bluing of the far-UV slope from β ~ -2.0 to β ~ -3.0. This can be explained by decreasing metallicity, except for the lowest luminosity galaxies (0.1L* z = 3), where low metallicity and smooth star formation histories (SFHs) fail to match the blue far-UV and moderately red H - [3.6] color. Such colors may require episodic SFHs with short periods of activity and quiescence ("on-off" cycles) and/or a contribution from emission lines. The stellar mass of our sample of z ~ 7 star-forming galaxies correlates with star formation rate (SFR) according to log M* = 8.70(±0.09) + 1.06(±0.10)log SFR, implying that star formation may have commenced at z > 10. No galaxies are found with SFRs much higher or lower than the past averaged SFR suggesting that the typical star formation timescales are probably a substantial fraction of the Hubble time. We report the first IRAC detection of Y 098-dropout galaxies at z ~ 8. The average rest-frame U - V ≈ 0.3 (AB) of the three galaxies are similar to faint z ~ 7 galaxies, implying similar M/L. The stellar mass density to M UV,AB Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 11563, 9797. Based on observations with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through contract 125790 issued by JPL/Caltech. Based on service

The SLUGGS survey: a comparison of total-mass profiles of early-type galaxies from observations and cosmological simulations, to ˜4 effective radii

Science.gov (United States)

Bellstedt, Sabine; Forbes, Duncan A.; Romanowsky, Aaron J.; Remus, Rhea-Silvia; Stevens, Adam R. H.; Brodie, Jean P.; Poci, Adriano; McDermid, Richard; Alabi, Adebusola; Chevalier, Leonie; Adams, Caitlin; Ferré-Mateu, Anna; Wasserman, Asher; Pandya, Viraj

2018-06-01

We apply the Jeans Anisotropic Multi-Gaussian Expansion dynamical modelling method to SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey data of early-type galaxies in the stellar mass range 1010 physical processes shaping the mass distributions of galaxies in cosmological simulations are still incomplete. For galaxies with M* > 1010.7 M⊙ in the Magneticum simulations, we identify a significant anticorrelation between total-mass density profile slopes and the fraction of stellar mass formed ex situ (i.e. accreted), whereas this anticorrelation is weaker for lower stellar masses, implying that the measured total-mass density slopes for low-mass galaxies are less likely to be determined by merger activity.

Dependence of the clustering properties of galaxies on stellar velocity dispersion in the Main galaxy sample of SDSS DR10

Science.gov (United States)

Deng, Xin-Fa; Song, Jun; Chen, Yi-Qing; Jiang, Peng; Ding, Ying-Ping

2014-08-01

Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 10 (SDSS DR10), we investigate the dependence of the clustering properties of galaxies on stellar velocity dispersion by cluster analysis. It is found that in the luminous volume-limited Main galaxy sample, except at r=1.2, richer and larger systems can be more easily formed in the large stellar velocity dispersion subsample, while in the faint volume-limited Main galaxy sample, at r≥0.9, an opposite trend is observed. According to statistical analyses of the multiplicity functions, we conclude in two volume-limited Main galaxy samples: small stellar velocity dispersion galaxies preferentially form isolated galaxies, close pairs and small group, while large stellar velocity dispersion galaxies preferentially inhabit the dense groups and clusters. However, we note the difference between two volume-limited Main galaxy samples: in the faint volume-limited Main galaxy sample, at r≥0.9, the small stellar velocity dispersion subsample has a higher proportion of galaxies in superclusters ( n≥200) than the large stellar velocity dispersion subsample.

The Origin of Stellar Species: constraining stellar evolution scenarios with Local Group galaxy surveys

Science.gov (United States)

Sarbadhicary, Sumit; Badenes, Carles; Chomiuk, Laura; Maldonado, Jessica; Caprioli, Damiano; Heger, Mairead; Huizenga, Daniel

2018-01-01

Our understanding of the progenitors of many stellar species, such as supernovae, massive and low-mass He-burning stars, is limited because of many poorly constrained aspects of stellar evolution theory. For my dissertation, I have focused on using Local Group galaxy surveys to constrain stellar evolution scenarios by measuring delay-time distributions (DTD). The DTD is the hypothetical occurrence rate of a stellar object per elapsed time after a brief burst of star formation. It is the measured distribution of timescales on which stars evolve, and therefore serves as a powerful observational constraint on theoretical progenitor models. The DTD can be measured from a survey of stellar objects and a set of star-formation histories of the host galaxy, and is particularly effective in the Local Group, where high-quality star-formation histories are available from resolved stellar populations. I am currently calculating a SN DTD with supernova remnants (SNRs) in order to provide the strongest constraints on the progenitors of thermonuclear and core-collapse supernovae. However, most SNRs do not have reliable age measurements and their evolution depends on the ambient environment. For this reason, I wrote a radio light curve model of an SNR population to extract the visibility times and rates of supernovae - crucial ingredients for the DTD - from an SNR survey. The model uses observational constraints on the local environments from multi-wavelength surveys, accounts for missing SNRs and employs the latest models of shock-driven particle acceleration. The final calculation of the SN DTD in the Local Group is awaiting completion of a systematic SNR catalog from deep radio-continuum images, now in preparation by a group led by Dr. Laura Chomiuk. I have also calculated DTDs for the LMC population of RR Lyrae and Cepheid variables, which serve as important distance calibrators and stellar population tracers. We find that Cepheids can have delay-times between 10 Myrs - 1 Gyr

Old star clusters: Bench tests of low mass stellar models

Directory of Open Access Journals (Sweden)

Salaris M.

2013-03-01

Full Text Available Old star clusters in the Milky Way and external galaxies have been (and still are traditionally used to constrain the age of the universe and the timescales of galaxy formation. A parallel avenue of old star cluster research considers these objects as bench tests of low-mass stellar models. This short review will highlight some recent tests of stellar evolution models that make use of photometric and spectroscopic observations of resolved old star clusters. In some cases these tests have pointed to additional physical processes efficient in low-mass stars, that are not routinely included in model computations. Moreover, recent results from the Kepler mission about the old open cluster NGC6791 are adding new tight constraints to the models.

THE MASS-DEPENDENT CLUSTERING HISTORY OF K-SELECTED GALAXIES AT z < 4 IN THE SXDS/UDS FIELD

International Nuclear Information System (INIS)

Furusawa, Junko; Sekiguchi, Kazuhiro; Takata, Tadafumi; Furusawa, Hisanori; Shimasaku, Kazuhiro; Simpson, Chris; Akiyama, Masayuki

2011-01-01

We investigate mass-dependent galaxy evolution based on a large sample of (more than 50,000) K-band selected galaxies in a multi-wavelength catalog of the Subaru/XMM-Newton Deep Survey and the UKIRT Infrared Deep Sky Survey/Ultra Deep Survey. We employ optical to near-infrared photometry to determine photometric redshifts of these galaxies. Then, we estimate the stellar mass of our sample galaxies using a standard fitting procedure as we used for estimation of the photometric redshift. From the sample galaxies, we obtain the stellar mass function of galaxies and the cosmic stellar mass density up to z ∼ 4. Our results are consistent with previous studies and we find a considerable number of low-mass galaxies (M * ∼ 10 10.5 ) at the redshift range 3 14 M sun ) to low (10 13 M sun ) with decreasing redshift at around z ∼ 2. We also find some high-mass density regions of massive galaxies at 1.4 ≤ z < 2.5 in our sample. These concentrations of massive galaxies may be candidate progenitors of the present-day clusters of galaxies. At this redshift range, massive star-forming galaxies are the dominant population making up the structures and the passively evolving galaxies show stronger clustering and they may have formed earlier than those star-forming galaxies.

AN INITIAL MASS FUNCTION STUDY OF THE DWARF STARBURST GALAXY NGC 4214

Energy Technology Data Exchange (ETDEWEB)

Andrews, J. E.; Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Chandar, R. [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Lee, J. C.; Whitmore, B. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Elmegreen, B. G. [IBM T. J. Watson Research Center, Yorktown Heights, NY (United States); Kennicutt, R. C. [Institute of Astronomy, Cambridge University, Cambridge (United Kingdom); Kissel, J. S. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Da Silva, Robert L.; Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); O' Connell, R. W. [Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States); Dopita, M. A. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Frogel, Jay A. [Galaxies Unlimited, 1 Tremblant Court, Lutherville, MD (United States); Kim, Hwihyun, E-mail: jandrews@astro.umass.edu, E-mail: callzetti@astro.umass.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States)

2013-04-10

The production rate of ionizing photons in young ({<=}8 Myr), unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses {approx}<10{sup 3} M{sub Sun }. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in H{alpha} luminosities, which needs to be taken into account when conducting this type of analysis.

Can physical stellar collisions explain the blue stragglers in the dwarf spheroidal galaxies?

International Nuclear Information System (INIS)

Leonard, P.J.T.

1993-01-01

The hypothesis that the blue stragglers in the dwarf spheroidal galaxie have a collisional origin is considered. If all of the dark matter in these galaxies is in the form of low-mass stars and the binary frequency is ≅ 50%, then it is quite possible that ≅ 10% to 20% of their blue stragglers have been produced by physical stellar collisions

THE BLACK HOLE MASS IN THE BRIGHTEST CLUSTER GALAXY NGC 6086

International Nuclear Information System (INIS)

McConnell, Nicholas J.; Ma, Chung-Pei; Graham, James R.; Wright, Shelley A.; Gebhardt, Karl; Lauer, Tod R.; Richstone, Douglas O.

2011-01-01

We present the first direct measurement of the central black hole mass, M . , in NGC 6086, the Brightest Cluster Galaxy (BCG) in A2162. Our investigation demonstrates for the first time that stellar-dynamical measurements of M . in BCGs are possible beyond the nearest few galaxy clusters. We observed NGC 6086 with laser guide star adaptive optics and the integral-field spectrograph (IFS) OSIRIS at the W. M. Keck Observatory and with the seeing-limited IFS GMOS-N at Gemini Observatory North. We combined the IFS data sets with existing major-axis kinematics and used axisymmetric stellar orbit models to determine M . and the R-band stellar mass-to-light ratio, M * /L R . We find M . = 3.6 +1.7 -1.1 x 10 9 M sun and M * /L R = 4.6 +0.3 -0.7 M sun L sun -1 (68% confidence) from models using the most massive dark matter halo allowed within the gravitational potential of the host cluster. Models fitting only IFS data confirm M . ∼ 3 x 10 9 M sun and M * /L R ∼ 4 M sun L sun -1 , with weak dependence on the assumed dark matter halo structure. When data out to 19 kpc are included, the unrealistic omission of dark matter causes the best-fit black hole mass to decrease dramatically, to 0.6 x 10 9 M sun , and the best-fit stellar mass-to-light ratio to increase to 6.7 M sun L -1 sun,R . The latter value is at further odds with stellar population studies favoring M * /L R ∼ 2 M sun L -1 sun . Biases from dark matter omission could extend to dynamical models of other galaxies with stellar cores, and revised measurements of M . could steepen the empirical scaling relationships between black holes and their host galaxies.

Galaxy spin as a formation probe: the stellar-to-halo specific angular momentum relation

Science.gov (United States)

Posti, Lorenzo; Pezzulli, Gabriele; Fraternali, Filippo; Di Teodoro, Enrico M.

2018-03-01

We derive the stellar-to-halo specific angular momentum relation (SHSAMR) of galaxies at z = 0 by combining (i) the standard Λcold dark matter tidal torque theory, (ii) the observed relation between stellar mass and specific angular momentum (the Fall relation), and (iii) various determinations of the stellar-to-halo mass relation (SHMR). We find that the ratio fj = j*/jh of the specific angular momentum of stars to that of the dark matter (i) varies with mass as a double power law, (ii) always has a peak in the mass range explored and iii) is three to five times larger for spirals than for ellipticals. The results have some dependence on the adopted SHMR and we provide fitting formulae in each case. For any choice of the SHMR, the peak of fj occurs at the same mass where the stellar-to-halo mass ratio f* = M*/Mh has a maximum. This is mostly driven by the straightness and tightness of the Fall relation, which requires fj and f* to be correlated with each other roughly as f_j∝ f_\\ast ^{2/3}, as expected if the outer and more angular momentum rich parts of a halo failed to accrete on to the central galaxy and form stars (biased collapse). We also confirm that the difference in the angular momentum of spirals and ellipticals at a given mass is too large to be ascribed only to different spins of the parent dark-matter haloes (spin bias).

No Assembly Required: Mergers are Mostly Irrelevant for the Growth of Low-mass Dwarf Galaxies

Science.gov (United States)

Fitts, Alex; Boylan-Kolchin, Michael; Bullock, James S.; Weisz, Daniel R.; El-Badry, Kareem; Wheeler, Coral; Faucher-Giguère, Claude-André; Quataert, Eliot; Hopkins, Philip F.; Kereš, Dušan; Wetzel, Andrew; Hayward, Christopher C.

2018-06-01

We investigate the merger histories of isolated dwarf galaxies based on a suite of 15 high-resolution cosmological zoom-in simulations, all with masses of Mhalo ≈ 1010 M⊙ (and M⋆ ˜ 105 - 107 M⊙) at z = 0, from the Feedback in Realistic Environments (FIRE) project. The stellar populations of these dwarf galaxies at z = 0 are formed essentially entirely "in situ": over 90% of the stellar mass is formed in the main progenitor in all but two cases, and all 15 of the galaxies have >70% of their stellar mass formed in situ. Virtually all galaxy mergers occur prior to z ˜ 3, meaning that accreted stellar populations are ancient. On average, our simulated dwarfs undergo 5 galaxy mergers in their lifetimes, with typical pre-merger galaxy mass ratios that are less than 1:10. This merger frequency is generally comparable to what has been found in dissipationless simulations when coupled with abundance matching. Two of the simulated dwarfs have a luminous satellite companion at z = 0. These ultra-faint dwarfs lie at or below current detectability thresholds but are intriguing targets for next-generation facilities. The small contribution of accreted stars make it extremely difficult to discern the effects of mergers in the vast majority of dwarfs either photometrically or using resolved-star color-magnitude diagrams (CMDs). The important implication for near-field cosmology is that star formation histories of comparably massive galaxies derived from resolved CMDs should trace the build-up of stellar mass in one main system across cosmic time as opposed to reflecting the contributions of many individual star formation histories of merged dwarfs.

HUBBLE RESIDUALS OF NEARBY TYPE Ia SUPERNOVAE ARE CORRELATED WITH HOST GALAXY MASSES

International Nuclear Information System (INIS)

Kelly, Patrick L.; Burke, David L.; Hicken, Malcolm; Mandel, Kaisey S.; Kirshner, Robert P.

2010-01-01

From Sloan Digital Sky Survey u'g'r'i'z' imaging, we estimate the stellar masses of the host galaxies of 70 low-redshift Type Ia supernovae (SNe Ia, 0.015 10.8 M sun in a cosmology fit yields 1 + w = 0.22 +0.152 -0.108 , while a combination where the 30 nearby SNe instead have host masses greater than 10 10.8 M sun yields 1 + w = -0.03 +0.217 -0.143 . Progenitor metallicity, stellar population age, and dust extinction correlate with galaxy mass and may be responsible for these systematic effects. Host galaxy measurements will yield improved distances to SNe Ia.

ON THE MAXIMUM MASS OF STELLAR BLACK HOLES

International Nuclear Information System (INIS)

Belczynski, Krzysztof; Fryer, Chris L.; Bulik, Tomasz; Ruiter, Ashley; Valsecchi, Francesca; Vink, Jorick S.; Hurley, Jarrod R.

2010-01-01

We present the spectrum of compact object masses: neutron stars and black holes (BHs) that originate from single stars in different environments. In particular, we calculate the dependence of maximum BH mass on metallicity and on some specific wind mass loss rates (e.g., Hurley et al. and Vink et al.). Our calculations show that the highest mass BHs observed in the Galaxy M bh ∼ 15 M sun in the high metallicity environment (Z = Z sun = 0.02) can be explained with stellar models and the wind mass loss rates adopted here. To reach this result we had to set luminous blue variable mass loss rates at the level of ∼10 -4 M sun yr -1 and to employ metallicity-dependent Wolf-Rayet winds. With such winds, calibrated on Galactic BH mass measurements, the maximum BH mass obtained for moderate metallicity (Z = 0.3 Z sun = 0.006) is M bh,max = 30 M sun . This is a rather striking finding as the mass of the most massive known stellar BH is M bh = 23-34 M sun and, in fact, it is located in a small star-forming galaxy with moderate metallicity. We find that in the very low (globular cluster-like) metallicity environment the maximum BH mass can be as high as M bh,max = 80 M sun (Z = 0.01 Z sun = 0.0002). It is interesting to note that X-ray luminosity from Eddington-limited accretion onto an 80 M sun BH is of the order of ∼10 40 erg s -1 and is comparable to luminosities of some known ultra-luminous X-ray sources. We emphasize that our results were obtained for single stars only and that binary interactions may alter these maximum BH masses (e.g., accretion from a close companion). This is strictly a proof-of-principle study which demonstrates that stellar models can naturally explain even the most massive known stellar BHs.

THE MOST MASSIVE GALAXIES AT 3.0 ≤ z < 4.0 IN THE NEWFIRM MEDIUM-BAND SURVEY: PROPERTIES AND IMPROVED CONSTRAINTS ON THE STELLAR MASS FUNCTION

International Nuclear Information System (INIS)

Marchesini, Danilo; Whitaker, Katherine E.; Brammer, Gabriel; Van Dokkum, Pieter G.; Muzzin, Adam; Wake, David; Labbe, Ivo; Quadri, Ryan F.; Franx, Marijn; Kriek, Mariska; Lee, Kyoung-Soo; Rudnick, Gregory; Illingworth, Garth D.

2010-01-01

We use the optical to mid-infrared coverage of the NEWFIRM Medium-Band Survey (NMBS) to characterize, for the first time, the properties of a mass-complete sample of 14 galaxies at 3.0 ≤ z star >2.5 x 10 11 M sun , and to derive significantly more accurate measurements of the high-mass end of the stellar mass function (SMF) of galaxies at 3.0 ≤ z tot ) = 26.1, and median rest-frame U - V colors of (U - V) = 1.6. About 60% of the mass-complete sample has optical colors satisfying either the U- or the B-dropout color criteria, although ∼50% of these galaxies has r>25.5. We find that ∼30% of the sample has star formation rates (SFRs) from SED modeling consistent with zero, although SFRs of up to ∼1-18 M sun yr -1 are also allowed within 1σ. However, >80% of the sample is detected at 24 μm, resulting in total infrared luminosities in the range (0.5-4.0) x 10 13 L sun . This implies the presence of either dust-enshrouded starburst activity (with SFRs of 600-4300 M sun yr -1 ) and/or highly obscured active galactic nuclei (AGNs). The contribution of galaxies with M star >2.5 x 10 11 M sun to the total stellar mass budget at 3.0 ≤ z +13 -3 %. Compared to recent estimates of the stellar mass density in galaxies with M star ∼ 10 9 -10 11 M sun at z ∼ 5 and z ∼ 6, we find an evolution by a factor of 2-7 and 3-22 from z ∼ 5 and z ∼ 6, respectively, to z = 3.5. The previously found disagreement at the high-mass end between observed and model-predicted SMFs is now significant at the 3σ level when only random uncertainties are considered. However, systematic uncertainties dominate the total error budget, with errors up to a factor of ∼8 in the densities at the high-mass end, bringing the observed SMF in marginal agreement with the predicted SMF. Additional systematic uncertainties on the high-mass end could be potentially introduced by either (1) the intense star formation and/or the very common AGN activities as inferred from the MIPS 24 �

Stochastic 2-D galaxy disk evolution models. Resolved stellar populations in the galaxy M33

Science.gov (United States)

Mineikis, T.; Vansevičius, V.

We improved the stochastic 2-D galaxy disk models (Mineikis & Vansevičius 2014a) by introducing enriched gas outflows from galaxies and synthetic color-magnitude diagrams of stellar populations. To test the models, we use the HST/ACS stellar photometry data in four fields located along the major axis of the galaxy M33 (Williams et al. 2009) and demonstrate the potential of the models to derive 2-D star formation histories in the resolved disk galaxies.

CONNECTION BETWEEN DYNAMICALLY DERIVED INITIAL MASS FUNCTION NORMALIZATION AND STELLAR POPULATION PARAMETERS

Energy Technology Data Exchange (ETDEWEB)

McDermid, Richard M. [Department of Physics and Astronomy, Macquarie University, Sydney NSW 2109 (Australia); Cappellari, Michele; Bayet, Estelle; Bureau, Martin; Davies, Roger L. [Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Alatalo, Katherine [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Blitz, Leo [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Bois, Maxime [Observatoire de Paris, LERMA and CNRS, 61 Av. de l' Observatoire, F-75014 Paris (France); Bournaud, Frédéric; Duc, Pierre-Alain [Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp- CNRS-Université Paris Diderot, F-91191 Gif-sur-Yvette Cedex (France); Crocker, Alison F. [Ritter Astrophysical Observatory, University of Toledo, Toledo, OH 43606 (United States); Davis, Timothy A.; De Zeeuw, P. T.; Emsellem, Eric; Kuntschner, Harald [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany); Khochfar, Sadegh [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Krajnović, Davor [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Morganti, Raffaella; Oosterloo, Tom [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Naab, Thorsten, E-mail: richard.mcdermid@mq.edu.au [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); and others

2014-09-10

We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS{sup 3D} project. We study trends between our dynamically derived IMF normalization α{sub dyn} ≡ (M/L){sub stars}/(M/L){sub Salp} and absorption line strengths, and interpret these via single stellar population-equivalent ages, abundance ratios (measured as [α/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalization of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of α{sub dyn} at a given population parameter. As a result, we find weak α{sub dyn}-[α/Fe] and α{sub dyn} –Age correlations and no significant α{sub dyn} –[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalization via the low-mass star demographics inferred through stellar spectral analysis.

The cosmic baryon cycle and galaxy mass assembly in the FIRE simulations

Science.gov (United States)

Anglés-Alcázar, Daniel; Faucher-Giguère, Claude-André; Kereš, Dušan; Hopkins, Philip F.; Quataert, Eliot; Murray, Norman

2017-10-01

We use cosmological simulations from the FIRE (Feedback In Realistic Environments) project to study the baryon cycle and galaxy mass assembly for central galaxies in the halo mass range Mhalo ˜ 1010-1013 M⊙. By tracing cosmic inflows, galactic outflows, gas recycling and merger histories, we quantify the contribution of physically distinct sources of material to galaxy growth. We show that in situ star formation fuelled by fresh accretion dominates the early growth of galaxies of all masses, while the re-accretion of gas previously ejected in galactic winds often dominates the gas supply for a large portion of every galaxy's evolution. Externally processed material contributes increasingly to the growth of central galaxies at lower redshifts. This includes stars formed ex situ and gas delivered by mergers, as well as smooth intergalactic transfer of gas from other galaxies, an important but previously underappreciated growth mode. By z = 0, wind transfer, I.e. the exchange of gas between galaxies via winds, can dominate gas accretion on to ˜L* galaxies over fresh accretion and standard wind recycling. Galaxies of all masses re-accrete ≳50 per cent of the gas ejected in winds and recurrent recycling is common. The total mass deposited in the intergalactic medium per unit stellar mass formed increases in lower mass galaxies. Re-accretion of wind ejecta occurs over a broad range of time-scales, with median recycling times (˜100-350 Myr) shorter than previously found. Wind recycling typically occurs at the scale radius of the halo, independent of halo mass and redshift, suggesting a characteristic recycling zone around galaxies that scales with the size of the inner halo and the galaxy's stellar component.

3D-HST + CANDELS: the Evolution of the Galaxy Size-mass Distribution Since Z=3

Science.gov (United States)

VanDerWel, A.; Franx, M.; vanDokkum, P. G.; Skelton, R. E.; Momcheva, I. G.; Whitaker, K. E.; Brammer, G. B.; Bell, E. F.; Rix, H.-W.; Wuyts, S.;

The Prospect for Detecting Stellar Coronal Mass Ejections

Science.gov (United States)

Osten, Rachel A.; Crosley, Michael Kevin

2018-06-01

The astrophysical study of mass loss, both steady-state and transient, on the cool half of the HR diagram has implications bothfor the star itself and the conditions created around the star that can be hospitable or inimical to supporting life. Recent results from exoplanet studies show that planets around M dwarfs are exceedingly common, which together with the commonality of M dwarfs in our galaxy make this the dominant mode of star and planet configurations. The closeness of the exoplanets to the parent M star motivate a comprehensive understanding of habitability for these systems. Radio observations provide the most clear signature of accelerated particles and shocks in stars arising as the result of MHD processes in the stellar outer atmosphere. Stellar coronal mass ejections have not been conclusively detected, despite the ubiquity with which their radiative counterparts in an eruptive event (stellar flares) have. I will review some of the different observational methods which have been used and possibly could be used in the future in the stellar case, emphasizing some of the difficulties inherent in such attempts. I will provide a framework for interpreting potential transient stellar mass loss in light of the properties of flares known to occur on magnetically active stars. This uses a physically motivated way to connect the properties of flares and coronal mass ejections and provides a testable hypothesis for observing or constraining transient stellar mass loss. I will describe recent results using radio observations to detect stellar coronal mass ejections, and what those results imply about transient stellar mass loss. I will provide some motivation for what could be learned in this topic from space-based low frequency radio experiments.

3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since z = 3

Science.gov (United States)

van der Wel, A.; Franx, M.; van Dokkum, P. G.; Skelton, R. E.; Momcheva, I. G.; Whitaker, K. E.; Brammer, G. B.; Bell, E. F.; Rix, H.-W.; Wuyts, S.; Ferguson, H. C.; Holden, B. P.; Barro, G.; Koekemoer, A. M.; Chang, Yu-Yen; McGrath, E. J.; Häussler, B.; Dekel, A.; Behroozi, P.; Fumagalli, M.; Leja, J.; Lundgren, B. F.; Maseda, M. V.; Nelson, E. J.; Wake, D. A.; Patel, S. G.; Labbé, I.; Faber, S. M.; Grogin, N. A.; Kocevski, D. D.

2014-06-01

Spectroscopic+photometric redshifts, stellar mass estimates, and rest-frame colors from the 3D-HST survey are combined with structural parameter measurements from CANDELS imaging to determine the galaxy size-mass distribution over the redshift range 0 3 × 109 M ⊙, and steep, R_{eff}\\propto M_*^{0.75}, for early-type galaxies with stellar mass >2 × 1010 M ⊙. The intrinsic scatter is lsim0.2 dex for all galaxy types and redshifts. For late-type galaxies, the logarithmic size distribution is not symmetric but is skewed toward small sizes: at all redshifts and masses, a tail of small late-type galaxies exists that overlaps in size with the early-type galaxy population. The number density of massive (~1011 M ⊙), compact (R eff < 2 kpc) early-type galaxies increases from z = 3 to z = 1.5-2 and then strongly decreases at later cosmic times.

Young stellar populations in early-type galaxies in the Sloan Digital Sky Survey

Science.gov (United States)

Nolan, Louisa A.; Raychaudhury, Somak; Kabán, Ata

2007-02-01

We use a purely data-driven rectified factor analysis to identify early-type galaxies with recent star formation in Data Release 4 of the Sloan Digital Sky Survey Spectroscopic Catalogue. We compare the spectra and environment of these galaxies with those of `normal' early-type galaxies, and a sample of independently selected E+A galaxies. We calculate the projected local galaxy surface density from the nearest five and 10 neighbours (Σ5 and Σ10) for each galaxy in our sample, and find that the dependence on projected local density, of the properties of E+A galaxies, is not significantly different from that of early-type galaxies with young stellar populations, dropping off rapidly towards denser environments, and flattening off at densities ~10 per cent of the stellar mass in these galaxies. This, together with the similarity of the environments in which this `E+F' population and the E+A galaxy sample are found, suggests that E+F galaxies used to be E+A galaxies, but have evolved by a further ~ one to a few Gyr. Our rectified factor analysis is sensitive enough to identify this hidden population, which allows us to study the global and intrinsic properties of early-type galaxies created in major mergers or interactions, and compare them with those early-types which have had the bulk of their stars in place since a much earlier epoch.

Connection between Dynamically Derived Initial Mass Function Normalization and Stellar Population Parameters

NARCIS (Netherlands)

McDermid, Richard M.; Cappellari, Michele; Alatalo, Katherine; Bayet, Estelle; Blitz, Leo; Bois, Maxime; Bournaud, Frédéric; Bureau, Martin; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS3D project. We study trends between our dynamically derived IMF normalization αdyn ≡

SDSS-IV MaNGA: Stellar angular momentum of about 2300 galaxies: unveiling the bimodality of massive galaxy properties

Science.gov (United States)

Graham, Mark T.; Cappellari, Michele; Li, Hongyu; Mao, Shude; Bershady, Matthew; Bizyaev, Dmitry; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Drory, Niv; Law, David R.; Pan, Kaike; Thomas, Daniel; Wake, David A.; Weijmans, Anne-Marie; Westfall, Kyle B.; Yan, Renbin

2018-03-01

We measure λ _{R_e}, a proxy for galaxy specific stellar angular momentum within one effective radius, and the ellipticity, ɛ, for about 2300 galaxies of all morphological types observed with integral field spectroscopy as part of the MaNGA survey, the largest such sample to date. We use the (λ _{R_e}, ɛ ) diagram to separate early-type galaxies into fast and slow rotators. We also visually classify each galaxy according to its optical morphology and two-dimensional stellar velocity field. Comparing these classifications to quantitative λ _{R_e} measurements reveals tight relationships between angular momentum and galaxy structure. In order to account for atmospheric seeing, we use realistic models of galaxy kinematics to derive a general approximate analytic correction for λ _{R_e}. Thanks to the size of the sample and the large number of massive galaxies, we unambiguously detect a clear bimodality in the (λ _{R_e}, ɛ ) diagram which may result from fundamental differences in galaxy assembly history. There is a sharp secondary density peak inside the region of the diagram with low λ _{R_e} and ɛ their distribution of the misalignments between the photometric and kinematic position angles. We confirm that genuine slow rotators start appearing above M ≥ 2 × 1011M⊙ where a significant number of high-mass fast rotators also exist.

SPARC: MASS MODELS FOR 175 DISK GALAXIES WITH SPITZER PHOTOMETRY AND ACCURATE ROTATION CURVES

Energy Technology Data Exchange (ETDEWEB)

Lelli, Federico; McGaugh, Stacy S. [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Schombert, James M., E-mail: federico.lelli@case.edu [Department of Physics, University of Oregon, Eugene, OR 97403 (United States)

2016-12-01

We introduce SPARC ( Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6  μ m and high-quality rotation curves from previous H i/H α studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i   mass–radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic to observed velocity ( V {sub bar}/ V {sub obs}) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ{sub ⋆}) at [3.6]. Assuming ϒ{sub ⋆} ≃ 0.5 M {sub ⊙}/ L {sub ⊙} (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity; (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii)  V {sub bar}/ V {sub obs} varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ{sub ⋆} ≃ 0.2 M {sub ⊙}/ L {sub ⊙} as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ{sub ⋆} ≃ 0.7 M {sub ⊙}/ L {sub ⊙} at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.

STELLAR NUCLEI AND INNER POLAR DISKS IN LENTICULAR GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Sil’chenko, Olga K., E-mail: olga@sai.msu.su [Sternberg Astronomical Institute, M.V. Lomonosov Moscow State University, Moscow, 119992 (Russian Federation); Isaac Newton Institute, Chile, Moscow Branch (Chile)

2016-09-01

I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of the Isaac Newton Group. I also estimate the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with the running tilted-ring technique, I have found seven new cases of inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10%, which is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample, implying similar histories of multiple gas-accretion events from various directions.

STELLAR NUCLEI AND INNER POLAR DISKS IN LENTICULAR GALAXIES

International Nuclear Information System (INIS)

Sil’chenko, Olga K.

2016-01-01

I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of the Isaac Newton Group. I also estimate the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with the running tilted-ring technique, I have found seven new cases of inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10%, which is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample, implying similar histories of multiple gas-accretion events from various directions.

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

Science.gov (United States)

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

2017-05-01

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

SDSS-IV MaNGA: environmental dependence of stellar age and metallicity gradients in nearby galaxies

Science.gov (United States)

Zheng, Zheng; Wang, Huiyuan; Ge, Junqiang; Mao, Shude; Li, Cheng; Li, Ran; Mo, Houjun; Goddard, Daniel; Bundy, Kevin; Li, Hongyu; Nair, Preethi; Lin, Lihwai; Long, R. J.; Riffel, Rogério; Thomas, Daniel; Masters, Karen; Bizyaev, Dmitry; Brownstein, Joel R.; Zhang, Kai; Law, David R.; Drory, Niv; Roman Lopes, Alexandre; Malanushenko, Olena

2017-03-01

We present a study on the stellar age and metallicity distributions for 1105 galaxies using the STARLIGHT software on MaNGA (Mapping Nearby Galaxies at APO) integral field spectra. We derive age and metallicity gradients by fitting straight lines to the radial profiles, and explore their correlations with total stellar mass M*, NUV - r colour and environments, as identified by both the large-scale structure (LSS) type and the local density. We find that the mean age and metallicity gradients are close to zero but slightly negative, which is consistent with the inside-out formation scenario. Within our sample, we find that both the age and metallicity gradients show weak or no correlation with either the LSS type or local density environment. In addition, we also study the environmental dependence of age and metallicity values at the effective radii. The age and metallicity values are highly correlated with M* and NUV - r and are also dependent on LSS type as well as local density. Low-mass galaxies tend to be younger and have lower metallicity in low-density environments while high-mass galaxies are less affected by environment.

Galaxy masses in large surveys: Connecting luminous and dark matter with weak lensing and kinematics

Science.gov (United States)

Reyes, Reinabelle

2011-01-01

Galaxy masses are difficult to determine because light traces stars and gas in a non-trivial way, and does not trace dark matter, which extends well beyond the luminous regions of galaxies. In this thesis, I use the most direct probes of dark matter available---weak gravitational lensing and galaxy kinematics---to trace the total mass in galaxies (and galaxy clusters) in large surveys. In particular, I use the large, homogeneous dataset from the Sloan Digital Sky Survey (SDSS), which provides spectroscopic redshifts for a large sample of galaxies at z ≲ 0.2 and imaging data to a depth of r < 22. By combining complementary probes, I am able to obtain robust observational constraints that cannot be obtained from any single technique alone. First, I use weak lensing of galaxy clusters to derive an optimal optical tracer of cluster mass, which was found to be a combination of cluster richness and the luminosity of the brightest cluster galaxy. Next, I combine weak lensing of luminous red galaxies with redshift distortions and clustering measurements to derive a robust probe of gravity on cosmological scales. Finally, I combine weak lensing with the kinematics of disk galaxies to constrain the total mass profile over several orders of magnitude. I derive a minimal-scatter relation between disk velocity and stellar mass (also known as the Tully-Fisher relation) that can be used, by construction, on a similarly-selected lens sample. Then, I combine this relation with halo mass measurements from weak lensing to place constraints on the ratio of the optical to virial velocities, as well as the ratio of halo to stellar masses, both as a function of stellar mass. These results will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work.

CHARACTERIZING THE STAR FORMATION OF THE LOW-MASS SHIELD GALAXIES FROM HUBBLE SPACE TELESCOPE IMAGING

Energy Technology Data Exchange (ETDEWEB)

McQuinn, Kristen B. W.; Skillman, Evan D.; Simones, Jacob E. [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church Street, S.E., Minneapolis, MN 55455 (United States); Cannon, John M. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Haynes, Martha P.; Giovanelli, Riccardo [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Salzer, John J. [Department of Astronomy, Indiana University, 727 East 3rd Street, Bloomington, IN 47405 (United States); Adams, Elizabeth A. K. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7900 AA Dwingeloo (Netherlands); Elson, Ed C. [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Ott, Jürgen, E-mail: kmcquinn@astro.umn.edu [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States)

2015-03-20

The Survey of Hi in Extremely Low-mass Dwarfs is an on-going multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies that populate the faint end of the galaxy luminosity function. The galaxies were selected from the first ∼10% of the Hi Arecibo Legacy Fast ALFA survey based on their low Hi mass and low baryonic mass. Here, we measure the star formation properties from optically resolved stellar populations for 12 galaxies using a color–magnitude diagram fitting technique. We derive lifetime average star formation rates (SFRs), recent SFRs, stellar masses, and gas fractions. Overall, the recent SFRs are comparable to the lifetime SFRs with mean birthrate parameter of 1.4, with a surprisingly narrow standard deviation of 0.7. Two galaxies are classified as dwarf transition galaxies (dTrans). These dTrans systems have star formation and gas properties consistent with the rest of the sample, in agreement with previous results that some dTrans galaxies may simply be low-luminosity dwarf irregulars. We do not find a correlation between the recent star formation activity and the distance to the nearest neighboring galaxy, suggesting that the star formation process is not driven by gravitational interactions, but regulated internally. Further, we find a broadening in the star formation and gas properties (i.e., specific SFRs, stellar masses, and gas fractions) compared to the generally tight correlation found in more massive galaxies. Overall, the star formation and gas properties indicate these very low-mass galaxies host a fluctuating, non-deterministic, and inefficient star formation process.

Galaxy Detection in 2MASS: Global Expectations and Results from Several Fields

Science.gov (United States)

Chester, T.; Jarrett, T.

1995-01-01

An alogorithm has been developed and used to find galaxies in the 2MASS data. It uses the central surface brightness and measured size to discriminate galaxies from the much larger stellar population.

MASS AND ENVIRONMENT AS DRIVERS OF GALAXY EVOLUTION. II. THE QUENCHING OF SATELLITE GALAXIES AS THE ORIGIN OF ENVIRONMENTAL EFFECTS

Energy Technology Data Exchange (ETDEWEB)

Peng Yingjie; Lilly, Simon J.; Carollo, Marcella [Institute of Astronomy, ETH Zurich, 8093 Zurich (Switzerland); Renzini, Alvio [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

2012-09-20

We extend the phenomenological study of the evolving galaxy population of Peng et al. (2010) to the central/satellite dichotomy in Yang et al. Sloan Digital Sky Survey (SDSS) groups. We find that satellite galaxies are responsible for all the environmental effects in our earlier work. The fraction of centrals that are red does not depend on their environment but only on their stellar masses, whereas that of the satellites depends on both. We define a relative satellite quenching efficiency {epsilon}{sub sat}, which is the fraction of blue centrals that are quenched upon becoming the satellite of another galaxy. This is shown to be independent of stellar mass, but to depend strongly on local overdensity, {delta}, ranging between 0.2 and at least 0.8. The red fraction of satellites correlate much better with the local overdensity {delta}, a measure of location within the group, than with the richness of the group, i.e., dark matter halo mass. This, and the fact that satellite quenching depends on local density and not on either the stellar mass of the galaxy or the dark matter halo mass, gives clues as to the nature of the satellite-quenching process. We furthermore show that the action of mass quenching on satellite galaxies is also independent of the dark matter mass of the parent halo. We then apply the Peng et al. approach to predict the mass functions of central and satellite galaxies, split into passive and active galaxies, and show that these match very well the observed mass functions from SDSS, further strengthening the validity of this phenomenological approach. We highlight the fact that the observed M* is exactly the same for the star-forming centrals and satellites and the observed M* for the star-forming satellites is independent of halo mass above 10{sup 12} M{sub Sun }, which emphasizes the universality of the mass-quenching process that we identified in Peng et al. Post-quenching merging modifies the mass function of the central galaxies but can

ON THE DISTRIBUTION OF STELLAR MASSES IN GAMMA-RAY BURST HOST GALAXIES

International Nuclear Information System (INIS)

Castro Ceron, J. M.; Michalowski, M. J.; Hjorth, J.; Malesani, D.; Watson, D.; Fynbo, J. P. U.; Gorosabel, J.; Morales Calderon, M.

2010-01-01

We analyze Spitzer images of 30 long-duration gamma-ray burst (GRB) host galaxies. We estimate their total stellar masses (M * ) based on the rest-frame K-band luminosities (L K rest ) and constrain their star formation rates (SFRs; not corrected for dust extinction) based on the rest-frame UV continua. Further, we compute a mean M * /L K rest = 0.45 M sun /L sun . We find that the hosts are low M * , star-forming systems. The median M * in our sample ((M * ) = 10 9.7 M sun ) is lower than that of 'field' galaxies (e.g., Gemini Deep Deep Survey). The range spanned by M * is 10 7 M sun * 11 M sun , while the range spanned by the dust-uncorrected UV SFR is 10 -2 M sun yr -1 sun yr -1 . There is no evidence for intrinsic evolution in the distribution of M * with redshift. We show that extinction by dust must be present in at least 25% of the GRB hosts in our sample and suggest that this is a way to reconcile our finding of a relatively lower UV-based, specific SFR (φ ≡ SFR/M * ) with previous claims that GRBs have some of the highest φ values. We also examine the effect that the inability to resolve the star-forming regions in the hosts has on φ.

THE MASS-METALLICITY RELATION WITH THE DIRECT METHOD ON STACKED SPECTRA OF SDSS GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Andrews, Brett H.; Martini, Paul, E-mail: andrews@astronomy.ohio-state.edu [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

2013-03-10

The relation between galaxy stellar mass and gas-phase metallicity is a sensitive diagnostic of the main processes that drive galaxy evolution, namely cosmological gas inflow, metal production in stars, and gas outflow via galactic winds. We employed the direct method to measure the metallicities of {approx}200,000 star-forming galaxies from the Sloan Digital Sky Survey that were stacked in bins of (1) stellar mass and (2) both stellar mass and star formation rate (SFR) to significantly enhance the signal-to-noise ratio of the weak [O III] {lambda}4363 and [O II] {lambda}{lambda}7320, 7330 auroral lines required to apply the direct method. These metallicity measurements span three decades in stellar mass from log(M{sub *}/M{sub Sun }) = 7.4-10.5, which allows the direct method mass-metallicity relation to simultaneously capture the high-mass turnover and extend a full decade lower in mass than previous studies that employed more uncertain strong line methods. The direct method mass-metallicity relation rises steeply at low mass (O/H {proportional_to} M{sub *} {sup 1/2}) until it turns over at log(M{sub *}/M{sub Sun }) = 8.9 and asymptotes to 12 + log(O/H) = 8.8 at high mass. The direct method mass-metallicity relation has a steeper slope, a lower turnover mass, and a factor of two to three greater dependence on SFR than strong line mass-metallicity relations. Furthermore, the SFR-dependence appears monotonic with stellar mass, unlike strong line mass-metallicity relations. We also measure the N/O abundance ratio, an important tracer of star formation history, and find the clear signature of primary and secondary nitrogen enrichment. N/O correlates tightly with oxygen abundance, and even more so with stellar mass.

LLAMA: nuclear stellar properties of Swift-BAT AGN and matched inactive galaxies

Science.gov (United States)

Lin, Ming-Yi; Davies, R. I.; Hicks, E. K. S.; Burtscher, L.; Contursi, A.; Genzel, R.; Koss, M.; 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.

2018-02-01

In a complete sample of local 14-195 keV selected active galactic nuclei (AGNs) and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and luminosity distributions at near-infrared wavelengths on scales of 10-150 pc, using SINFONI on the VLT. In this paper, we present the first half of the sample, which comprises 13 galaxies, eight AGNs and five inactive galaxies. The stellar velocity fields show a disc-like rotating pattern, for which the kinematic position angle is in agreement with the photometric position angle obtained from large scale images. For this set of galaxies, the stellar surface brightness of the inactive galaxy sample is generally comparable to the matched sample of AGN, but extends to lower surface brightness. After removal of the bulge contribution, we find a nuclear stellar light excess with an extended nuclear disc structure, which exhibits a size-luminosity relation. While we expect the excess luminosity to be associated with a dynamically cooler young stellar population, we do not typically see a matching drop in dispersion. This may be because these galaxies have pseudo-bulges in which the intrinsic dispersion increases towards the centre. And although the young stars may have an impact in the observed kinematics, their fraction is too small to dominate over the bulge and compensate the increase in dispersion at small radii, so no dispersion drop is seen. Finally, we find no evidence for a difference in the stellar kinematics and nuclear stellar luminosity excess between these active and inactive galaxies.

Stellar chemical signatures and hierarchical galaxy formation

NARCIS (Netherlands)

Venn, KA; Irwin, M; Shetrone, MD; Tout, CA; Hill, [No Value; Tolstoy, E

To compare the chemistries of stars in the Milky Way dwarf spheroidal (dSph) satellite galaxies with stars in the Galaxy, we have compiled a large sample of Galactic stellar abundances from the literature. When kinematic information is available, we have assigned the stars to standard Galactic

THE STELLAR MASS–HALO MASS RELATION FOR LOW-MASS X-RAY GROUPS AT 0.5< z< 1 IN THE CDFS WITH CSI

International Nuclear Information System (INIS)

Patel, Shannon G.; Kelson, Daniel D.; Williams, Rik J.; Mulchaey, John S.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A.

2015-01-01

Since z∼1, the stellar mass density locked in low-mass groups and clusters has grown by a factor of ∼8. Here, we make the first statistical measurements of the stellar mass content of low-mass X-ray groups at 0.5stellar-to-halo mass scales for wide-field optical and infrared surveys. Groups are selected from combined Chandra and XMM-Newton X-ray observations in the Chandra Deep Field South. These ultra-deep observations allow us to identify bona fide low-mass groups at high redshift and enable measurements of their total halo masses. We compute aggregate stellar masses for these halos using galaxies from the Carnegie-Spitzer-IMACS (CSI) spectroscopic redshift survey. Stars comprise ∼3%–4% of the total mass of group halos with masses 10 12.8 mass of Fornax and one-fiftieth the mass of Virgo). Complementing our sample with higher mass halos at these redshifts, we find that the stellar-to-halo mass ratio decreases toward higher halo masses, consistent with other work in the local and high redshift universe. The observed scatter about the stellar–halo mass relation is σ∼0.25 dex, which is relatively small and suggests that total group stellar mass can serve as a rough proxy for halo mass. We find no evidence for any significant evolution in the stellar–halo mass relation since z≲1. Quantifying the stellar content in groups since this epoch is critical given that hierarchical assembly leads to such halos growing in number density and hosting increasing shares of quiescent galaxies

Individual stellar haloes of massive galaxies measured to 100 kpc at 0.3 < z < 0.5 using Hyper Suprime-Cam

Science.gov (United States)

Huang, Song; Leauthaud, Alexie; Greene, Jenny E.; Bundy, Kevin; Lin, Yen-Ting; Tanaka, Masayuki; Miyazaki, Satoshi; Komiyama, Yutaka

2018-04-01

Massive galaxies display extended light profiles that can reach several hundreds of kiloparsecs. We use data from the Hyper Suprime-Cam (HSC) survey that is simultaneously wide (˜100 deg2) and deep (>28.5 mag arcsec-2 in i band) to study the stellar haloes of a sample of ˜7000 massive galaxies at z ˜ 0.4. The depth of the HSC data enables us to measure surface mass density profiles to 100 kpc for individual galaxies without stacking. As in previous work, we find that more massive galaxies exhibit more extended outer profiles than smaller galaxies. When this extended light is not properly accounted for (because of shallow imaging and/or inadequate profile modelling), the derived stellar mass function can be significantly underestimated at the high-mass end. Across our sample, the ellipticity of outer light profile increases substantially with radius. We show for the first time that these ellipticity gradients steepen dramatically as a function of galaxy mass, but we detect no mass dependence in outer colour gradients. Our results support the two-phase formation scenario for massive galaxies in which outer envelopes are built up at a later time from a series of merging events. We provide surface mass density profiles in a convenient tabulated format to facilitate comparisons with predictions from numerical simulations of galaxy formation.

The galaxy-subhalo connection in low-redshift galaxy clusters from weak gravitational lensing

Science.gov (United States)

Sifón, Cristóbal; Herbonnet, Ricardo; Hoekstra, Henk; van der Burg, Remco F. J.; Viola, Massimo

2018-05-01

We measure the gravitational lensing signal around satellite galaxies in a sample of galaxy clusters at z physically-motivated definition of subhalo mass, namely the mass bound to the subhalo, mbg, similar to definitions used by common subhalo finders in numerical simulations. Binning the satellites by stellar mass we provide a direct measurement of the subhalo-to-stellar-mass relation, log mbg/M⊙ = (11.54 ± 0.05) + (0.95 ± 0.10)log [m⋆/(2 × 1010M⊙)]. This best-fitting relation implies that, at a stellar mass m⋆ ˜ 3 × 1010 M⊙, subhalo masses are roughly 50 per cent of those of central galaxies, and this fraction decreases at higher stellar masses. We find some evidence for a sharp change in the total-to-stellar mass ratio around the clusters' scale radius, which could be interpreted as galaxies within the scale radius having suffered more strongly from tidal stripping, but remain cautious regarding this interpretation.

The Stellar Initial Mass Function in Early-type Galaxies from Absorption Line Spectroscopy. IV. A Super-Salpeter IMF in the Center of NGC 1407 from Non-parametric Models

Energy Technology Data Exchange (ETDEWEB)

Conroy, Charlie [Department of Astronomy, Harvard University, Cambridge, MA, 02138 (United States); Van Dokkum, Pieter G. [Department of Astronomy, Yale University, New Haven, CT, 06511 (United States); Villaume, Alexa [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

2017-03-10

It is now well-established that the stellar initial mass function (IMF) can be determined from the absorption line spectra of old stellar systems, and this has been used to measure the IMF and its variation across the early-type galaxy population. Previous work focused on measuring the slope of the IMF over one or more stellar mass intervals, implicitly assuming that this is a good description of the IMF and that the IMF has a universal low-mass cutoff. In this work we consider more flexible IMFs, including two-component power laws with a variable low-mass cutoff and a general non-parametric model. We demonstrate with mock spectra that the detailed shape of the IMF can be accurately recovered as long as the data quality is high (S/N ≳ 300 Å{sup −1}) and cover a wide wavelength range (0.4–1.0 μ m). We apply these flexible IMF models to a high S/N spectrum of the center of the massive elliptical galaxy NGC 1407. Fitting the spectrum with non-parametric IMFs, we find that the IMF in the center shows a continuous rise extending toward the hydrogen-burning limit, with a behavior that is well-approximated by a power law with an index of −2.7. These results provide strong evidence for the existence of extreme (super-Salpeter) IMFs in the cores of massive galaxies.

Looking for Galaxies in All the Right Places: A Search for Stellar Populations in ALFALFA’s Ultra-compact High Velocity Clouds

Science.gov (United States)

Janesh, William; Rhode, Katherine L.; Salzer, John J.; Janowiecki, Steven; Adams, Elizabeth; Haynes, Martha P.; Giovanelli, Riccardo; Cannon, John M.

2018-01-01

Nearby gas-rich dwarf galaxies are excellent laboratories for investigating the baryonic feedback processes that govern star formation and galaxy evolution in galaxies at the extreme end of the mass function. Detecting and studying such objects may help resolve the well-known tension between cosmological model predictions for low-mass dark matter halos and observations. The ALFALFA neutral hydrogen (Hi) survey has detected a sample of isolated ultra-compact high-velocity Hi clouds (UCHVCs) with kinematic properties that make them likely members of the Local Volume, but that have no optical counterparts in existing optical surveys. This UCHVC sample possesses Hi properties (at 1 Mpc, Hi masses of ~105-106 M⊙, Hi diameters of ~2-3 kpc, and dynamical masses of ~107-108 M⊙) similar to other known ultra-faint dwarf galaxies like Leo T. Following the discovery of Leo P, an extremely metal-poor, gas-rich star-forming dwarf galaxy associated with an ALFALFA UCHVC, we have initiated a campaign to obtain deep optical imaging of 56 UCHVCs using the wide field-of-view, high-resolution ODI camera on the WIYN 3.5-m telescope. Here we present a brief overview of our campaign to search for resolved stellar populations associated with the UCHVCs in our optical images, and initial results from our survey.After creating a stellar catalog from the pipeline-reduced and stacked ODI g- and i-band images, we apply a color-magnitude filter tuned for old, metal-poor stellar populations to select red giant branch stars at distances between 250 kpc and 2 Mpc. The spatial distribution of the stars selected by the filter is then smoothed, and overdensities in the fields are identified. Of the 22 targets analyzed to date, seven have associated stellar populations detected at a high confidence (92% to 99.9% significance). The detected objects have a range of distances (from 350 kpc to 1.6 Mpc) and have optical properties similar to those of ultra-faint dwarf galaxies. These objects have

The EDGE-CALIFA survey: validating stellar dynamical mass models with CO kinematics

Science.gov (United States)

Leung, Gigi Y. C.; Leaman, Ryan; van de Ven, Glenn; Lyubenova, Mariya; Zhu, Ling; Bolatto, Alberto D.; Falcón-Barroso, Jesus; Blitz, Leo; Dannerbauer, Helmut; Fisher, David B.; Levy, Rebecca C.; Sanchez, Sebastian F.; Utomo, Dyas; Vogel, Stuart; Wong, Tony; Ziegler, Bodo

2018-06-01

Deriving circular velocities of galaxies from stellar kinematics can provide an estimate of their total dynamical mass, provided a contribution from the velocity dispersion of the stars is taken into account. Molecular gas (e.g. CO), on the other hand, is a dynamically cold tracer and hence acts as an independent circular velocity estimate without needing such a correction. In this paper, we test the underlying assumptions of three commonly used dynamical models, deriving circular velocities from stellar kinematics of 54 galaxies (S0-Sd) that have observations of both stellar kinematics from the Calar Alto Legacy Integral Field Area (CALIFA) survey, and CO kinematics from the Extragalactic Database for Galaxy Evolution (EDGE) survey. We test the asymmetric drift correction (ADC) method, as well as Jeans, and Schwarzschild models. The three methods each reproduce the CO circular velocity at 1Re to within 10 per cent. All three methods show larger scatter (up to 20 per cent) in the inner regions (R < 0.4Re) that may be due to an increasingly spherical mass distribution (which is not captured by the thin disc assumption in ADC), or non-constant stellar M/L ratios (for both the JAM and Schwarzschild models). This homogeneous analysis of stellar and gaseous kinematics validates that all three models can recover Mdyn at 1Re to better than 20 per cent, but users should be mindful of scatter in the inner regions where some assumptions may break down.

INTEGRAL-FIELD STELLAR AND IONIZED GAS KINEMATICS OF PECULIAR VIRGO CLUSTER SPIRAL GALAXIES

International Nuclear Information System (INIS)

Cortés, Juan R.; Hardy, Eduardo; Kenney, Jeffrey D. P.

2015-01-01

We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5 m telescope in order to look for kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. Two-dimensional maps of the stellar velocity V, stellar velocity dispersion σ, and the ionized gas velocity (Hβ and/or [O III]) are presented for the galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axes are found in several galaxies. While in some cases this is due to a bar, in other cases it seems to be associated with gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxies have signatures of kinematically distinct stellar components, which are likely signatures of accretion or mergers. For all of our galaxies, we compute the angular momentum parameter λ R . An evaluation of the galaxies in the λ R ellipticity plane shows that all but two of the galaxies have significant support from random stellar motions, and have likely experienced gravitational interactions. This includes some galaxies with very small bulges and truncated/compact Hα morphologies, indicating that such galaxies cannot be fully explained by simple ram pressure stripping, but must have had significant gravitational encounters. Most of the sample galaxies show evidence for ICM-ISM stripping as well as gravitational interactions, indicating that the evolution of a significant fraction of cluster galaxies is likely strongly impacted by both effects

MAJOR-MERGER GALAXY PAIRS IN THE COSMOS FIELD—MASS-DEPENDENT MERGER RATE EVOLUTION SINCE z = 1

International Nuclear Information System (INIS)

Xu, C. Kevin; Zhao, Yinghe; Gao, Y.; Scoville, N.; Capak, P.; Drory, N.

2012-01-01

We present results of a statistical study of the cosmic evolution of the mass-dependent major-merger rate since z = 1. A stellar mass limited sample of close major-merger pairs (the CPAIR sample) was selected from the archive of the COSMOS survey. Pair fractions at different redshifts derived using the CPAIR sample and a local K-band-selected pair sample show no significant variations with stellar mass. The pair fraction exhibits moderately strong cosmic evolution, with the best-fitting function of f pair = 10 –1.88(±0.03) (1 + z) 2.2(±0.2) . The best-fitting function for the merger rate is R mg (Gyr –1 ) = 0.053 × (M star /10 10.7 M ☉ ) 0.3 (1 + z) 2.2 /(1 + z/8). This rate implies that galaxies of M star ∼ 10 10 -10 11.5 M ☉ have undergone ∼0.5-1.5 major mergers since z = 1. Our results show that, for massive galaxies (M star ≥ 10 10.5 M ☉ ) at z ≤ 1, major mergers involving star-forming galaxies (i.e., wet and mixed mergers) can account for the formation of both ellipticals and red quiescent galaxies (RQGs). On the other hand, major mergers cannot be responsible for the formation of most low mass ellipticals and RQGs of M star ∼ 10.3 M ☉ . Our quantitative estimates indicate that major mergers have significant impact on the stellar mass assembly of the most massive galaxies (M star ≥ 10 11.3 M ☉ ), but for less massive galaxies the stellar mass assembly is dominated by the star formation. Comparison with the mass-dependent (ultra)luminous infrared galaxies ((U)LIRG) rates suggests that the frequency of major-merger events is comparable to or higher than that of (U)LIRGs.

Stellar Relics from the Early Galaxy T. Sivarani

Indian Academy of Sciences (India)

metal-poor stars is used to study the chemical history of the galaxy. Apart from this,. 5 .... They fit a color-magnitude diagram in order to trace different stellar population and derived a ... distinctly different stellar population with a different origin.

THE STELLAR AND GAS KINEMATICS OF THE LITTLE THINGS DWARF IRREGULAR GALAXY NGC 1569

International Nuclear Information System (INIS)

Johnson, Megan; Hunter, Deidre A.; Zhang, Hong-Xin; Herrmann, Kimberly; Oh, Se-Heon; Elmegreen, Bruce; Brinks, Elias; Tollerud, Erik

2012-01-01

In order to understand the formation and evolution of Magellanic-type dwarf irregular (dIm) galaxies, one needs to understand their three-dimensional structure. We present measurements of the stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy. The stellar vertical velocity dispersion, σ z , coupled with the maximum rotational velocity derived from H I observations, V max , gives a measure of how kinematically hot the galaxy is, and, therefore, indicates its structure. We conclude that the stars in NGC 1569 are in a thick disk with a V max /σ z = 2.4 ± 0.7. In addition to the structure, we analyze the ionized gas kinematics from O III observations along the morphological major axis. These data show evidence for outflow from the inner starburst region and a potential expanding shell near supermassive star cluster (SSC) A. When compared to the stellar kinematics, the velocity dispersion of the stars increases in the region of SSC A supporting the hypothesis of an expanding shell. The stellar kinematics closely follow the motion of the gas. Analysis of high-resolution H I data clearly reveals the presence of an H I cloud that appears to be impacting the eastern edge of NGC 1569. Also, an ultra-dense H I cloud can be seen extending to the west of the impacting H I cloud. This dense cloud is likely the remains of a dense H I bridge that extended through what is now the central starburst area. The impacting H I cloud was the catalyst for the starburst, thus turning the dense gas into stars over a short timescale, ∼1 Gyr. We performed a careful study of the spectral energy distribution using infrared, optical, and ultraviolet photometry, producing a state-of-the-art mass model for the stellar disk. This mass modeling shows that stars dominate the gravitational potential in the inner 1 kpc. The dynamical mass of NGC 1569, derived from V max , shows that the disk may be dark matter deficient in the inner region, although, when compared to the

EARLY-TYPE GALAXIES AT z ∼ 1.3. II. MASSES AND AGES OF EARLY-TYPE GALAXIES IN DIFFERENT ENVIRONMENTS AND THEIR DEPENDENCE ON STELLAR POPULATION MODEL ASSUMPTIONS

International Nuclear Information System (INIS)

Raichoor, A.; Mei, S.; Huertas-Company, M.; Nakata, F.; Kodama, T.; Stanford, S. A.; Rettura, A.; Jee, M. J.; Holden, B. P.; Illingworth, G.; Postman, M.; White, R. L.; Rosati, P.; Blakeslee, J. P.; Demarco, R.; Eisenhardt, P.; Tanaka, M.

2011-01-01

We have derived masses and ages for 79 early-type galaxies (ETGs) in different environments at z ∼ 1.3 in the Lynx supercluster and in the GOODS/CDF-S field using multi-wavelength (0.6-4.5 μm; KPNO, Palomar, Keck, Hubble Space Telescope, Spitzer) data sets. At this redshift the contribution of the thermally pulsing asymptotic giant branch (TP-AGB) phase is important for ETGs, and the mass and age estimates depend on the choice of the stellar population model used in the spectral energy distribution fits. We describe in detail the differences among model predictions for a large range of galaxy ages, showing the dependence of these differences on age. Current models still yield large uncertainties. While recent models from Maraston and Charlot and Bruzual offer better modeling of the TP-AGB phase with respect to less recent Bruzual and Charlot models, their predictions do not often match. The modeling of this TP-AGB phase has a significant impact on the derived parameters for galaxies observed at high redshift. Some of our results do not depend on the choice of the model: for all models, the most massive galaxies are the oldest ones, independent of the environment. When using the Maraston and Charlot and Bruzual models, the mass distribution is similar in the clusters and in the groups, whereas in our field sample there is a deficit of massive (M ∼> 10 11 M sun ) ETGs. According to those last models, ETGs belonging to the cluster environment host on average older stars with respect to group and field populations. This difference is less significant than the age difference in galaxies of different masses.

Evidence for AGN feedback in low-mass galaxies

Science.gov (United States)

Masters, Karen; Penny, Sam; Smethurst, Rebecca; Krawczyk, Coleman; Nichol, Bob; SDSS-IV MaNGA

2018-01-01

Despite being the dominant galaxy population by number in groups and clusters, the formation and quenching mechanism of dwarf galaxies remains unknown. We present evidence for AGN feedback in a subset of 69 quenched low-mass galaxies (M* less than 5e9 Msun, fainter than Mr = -19) selected from the first two years of the MaNGA survey. The majority (85 per cent) of these quenched galaxies appear to reside in a group environment. We find 6 galaxies in our sample that appear to have an active AGN that is preventing on-going star-formation; this is the first time such a feedback mechanism has been observed in this mass range. Interestingly, five of these six galaxies have an ionised gas component that is kinematically offset from their stellar component, suggesting the gas is either recently accreted or outflowing. We hypothesise these six galaxies are low-mass equivalents to the “red geysers” observed in more massive galaxies. Of the other 62 galaxies in the sample, we find 8 do appear to have some low-level, residual star formation, or emission from hot, evolved stars. The remaining galaxies in our sample have no detectable ionised gas emission throughout their structures, consistent with them being quenched. I will show that despite being the "simplest" galaxies in our current models of galaxy formation, these quenched dwarf galaxies are a diverse population.

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

Science.gov (United States)

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.

Star formation and mass assembly in high redshift galaxies

Science.gov (United States)

Santini, P.; Fontana, A.; Grazian, A.; Salimbeni, S.; Fiore, F.; Fontanot, F.; Boutsia, K.; Castellano, M.; Cristiani, S.; de Santis, C.; Gallozzi, S.; Giallongo, E.; Menci, N.; Nonino, M.; Paris, D.; Pentericci, L.; Vanzella, E.

2009-09-01

Aims: The goal of this work is to infer the star formation properties and the mass assembly process of high redshift (0.3 ≤ z MUSIC catalog, which has multiwavelength coverage from 0.3 to 24 μm and either spectroscopic or accurate photometric redshifts. We describe how the catalog has been extended by the addition of mid-IR fluxes derived from the MIPS 24 μm image. We compared two different estimators of the star formation rate (SFR hereafter). One is the total infrared emission derived from 24 μm, estimated using both synthetic and empirical IR templates. The other one is a multiwavelength fit to the full galaxy SED, which automatically accounts for dust reddening and age-star formation activity degeneracies. For both estimates, we computed the SFR density and the specific SFR. Results: We show that the two SFR indicators are roughly consistent, once the uncertainties involved are taken into account. However, they show a systematic trend, IR-based estimates exceeding the fit-based ones as the star formation rate increases. With this new catalog, we show that: a) at z>0.3, the star formation rate is correlated well with stellar mass, and this relationship seems to steepen with redshift if one relies on IR-based estimates of the SFR; b) the contribution to the global SFRD by massive galaxies increases with redshift up to ≃ 2.5, more rapidly than for galaxies of lower mass, but appears to flatten at higher z; c) despite this increase, the most important contributors to the SFRD at any z are galaxies of about, or immediately lower than, the characteristic stellar mass; d) at z≃ 2, massive galaxies are actively star-forming, with a median {SFR} ≃ 300 M_⊙ yr-1. During this epoch, our targeted galaxies assemble a substantial part of their final stellar mass; e) the specific SFR (SSFR) shows a clear bimodal distribution. Conclusions: The analysis of the SFR density and the SSFR seems to support the downsizing scenario, according to which high mass galaxies

A Multiwavelength Study of POX 52, a Dwarf Seyfert Galaxy with an Intermediate Mass Black Hole

Science.gov (United States)

Barth, Aaron

2004-09-01

POX 52 is a Seyfert 1 galaxy with unprecedented properties: its host galaxy is a dwarf elliptical, and its stellar velocity dispersion is only 36 km/s. The stellar velocity dispersion and the broad emission-line widths both suggest a black hole mass of order 10^5 solar masses. We request HST ACS/HRC imaging to perform a definitive measurement of the host galaxy structure; STIS UV and optical spectroscopy to study the nonstellar continuum and the structure of the broad-line region; and Chandra ACIS imaging to investigate the spectral and variability properties of the X-ray emission. The results of this program will give a detailed understanding of the host galaxy and accretion properties of one of the very few known black holes in the mass range around 10^5 solar masses.

Modeling The GRB Host Galaxy Mass Distribution: Are GRBs Unbiased Tracers of Star Formation?

Energy Technology Data Exchange (ETDEWEB)

Kocevski, Daniel; /KIPAC, Menlo Park; West, Andrew A.; /UC, Berkeley, Astron. Dept. /MIT, MKI; Modjaz, Maryam; /UC, Berkeley, Astron. Dept.

2009-08-03

We model the mass distribution of long gamma-ray burst (GRB) host galaxies given recent results suggesting that GRBs occur in low metallicity environments. By utilizing measurements of the redshift evolution of the mass-metallicity (M-Z) relationship for galaxies, along with a sharp host metallicity cut-off suggested by Modjaz and collaborators, we estimate an upper limit on the stellar mass of a galaxy that can efficiently produce a GRB as a function of redshift. By employing consistent abundance indicators, we find that sub-solar metallicity cut-offs effectively limit GRBs to low stellar mass spirals and dwarf galaxies at low redshift. At higher redshifts, as the average metallicity of galaxies in the Universe falls, the mass range of galaxies capable of hosting a GRB broadens, with an upper bound approaching the mass of even the largest spiral galaxies. We compare these predicted limits to the growing number of published GRB host masses and find that extremely low metallicity cut-offs of 0.1 to 0.5 Z{sub {circle_dot}} are effectively ruled out by a large number of intermediate mass galaxies at low redshift. A mass function that includes a smooth decrease in the efficiency of producing GRBs in galaxies of metallicity above 12+log(O/H){sub KK04} = 8.7 can, however, accommodate a majority of the measured host galaxy masses. We find that at z {approx} 1, the peak in the observed GRB host mass distribution is inconsistent with the expected peak in the mass of galaxies harboring most of the star formation. This suggests that GRBs are metallicity biased tracers of star formation at low and intermediate redshifts, although our model predicts that this bias should disappear at higher redshifts due to the evolving metallicity content of the universe.

MODELING THE GRB HOST GALAXY MASS DISTRIBUTION: ARE GRBs UNBIASED TRACERS OF STAR FORMATION?

International Nuclear Information System (INIS)

Kocevski, Daniel; West, Andrew A.; Modjaz, Maryam

2009-01-01

We model the mass distribution of long gamma-ray burst (GRB) host galaxies given recent results suggesting that GRBs occur in low-metallicity environments. By utilizing measurements of the redshift evolution of the mass-metallicity relationship for galaxies, along with a sharp host metallicity cutoff suggested by Modjaz and collaborators, we estimate an upper limit on the stellar mass of a galaxy that can efficiently produce a GRB as a function of redshift. By employing consistent abundance indicators, we find that subsolar metallicity cutoffs effectively limit GRBs to low-stellar mass spirals and dwarf galaxies at low redshift. At higher redshifts, as the average metallicity of galaxies in the Universe falls, the mass range of galaxies capable of hosting a GRB broadens, with an upper bound approaching the mass of even the largest spiral galaxies. We compare these predicted limits to the growing number of published GRB host masses and find that extremely low-metallicity cutoffs of 0.1 to 0.5 Z sun are effectively ruled out by a large number of intermediate mass galaxies at low redshift. A mass function that includes a smooth decrease in the efficiency of producing GRBs in galaxies of metallicity above 12+log(O/H) KK04 = 8.7 can, however, accommodate a majority of the measured host galaxy masses. We find that at z ∼ 1, the peak in the observed GRB host mass distribution is inconsistent with the expected peak in the mass of galaxies harboring most of the star formation. This suggests that GRBs are metallicity-biased tracers of star formation at low and intermediate redshifts, although our model predicts that this bias should disappear at higher redshifts due to the evolving metallicity content of the universe.

The Intrinsic Characteristics of Galaxies on the SFR–M ∗ Plane at 1.2 < z < 4: I. The Correlation between Stellar Age, Central Density, and Position Relative to the Main Sequence

Science.gov (United States)

Lee, Bomee; Giavalisco, Mauro; Whitaker, Katherine; Williams, Christina C.; Ferguson, Henry C.; Acquaviva, Viviana; Koekemoer, Anton M.; Straughn, Amber N.; Guo, Yicheng; Kartaltepe, Jeyhan S.; Lotz, Jennifer; Pacifici, Camilla; Croton, Darren J.; Somerville, Rachel S.; Lu, Yu

2018-02-01

We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M *), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the mass-weighted stellar age, in galaxies at 1.2history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the ({M}* ;{SFR}) plane bends at high mass. We observe clear morphological differences among galaxies across the MS, which also correlate with stellar age. At all redshifts, galaxies that are quenching or quenched, and thus old, have high {{{Σ }}}1 (the projected density within the central 1 kpc), while younger, star-forming galaxies span a much broader range of {{{Σ }}}1, which includes the high values observed for quenched galaxies, but also extends to much lower values. As galaxies age and quench, the stellar age and the dispersion of {{{Σ }}}1 for fixed values of M * shows two different regimes: one at the low-mass end, where quenching might be driven by causes external to the galaxies; the other at the high-mass end, where quenching is driven by internal causes, very likely the mass given the low scatter of {{{Σ }}}1 (mass quenching). We suggest that the monotonic increase of central density as galaxies grow is one manifestation of a more general phenomenon of structural transformation that galaxies undergo as they evolve.

Resolving the age bimodality of galaxy stellar populations on kpc scales

NARCIS (Netherlands)

Zibetti, Stefano; Gallazzi, Anna R.; Ascasibar, Y.; Charlot, S.; Galbany, L.; García Benito, R.; Kehrig, C.; de Lorenzo-Cáceres, A.; Lyubenova, M.; Marino, R. A.; Márquez, I.; Sánchez, S. F.; van de Ven, G.; Walcher, C. J.; Wisotzki, L.

2017-01-01

Galaxies in the local Universe are known to follow bimodal distributions in the global stellar population properties. We analyse the distribution of the local average stellar population ages of 654 053 sub-galactic regions resolved on ˜1 kpc scales in a volume-corrected sample of 394 galaxies, drawn

The galaxy-subhalo connection in low-redshift galaxy clusters from weak gravitational lensing

Science.gov (United States)

Sifón, Cristóbal; Herbonnet, Ricardo; Hoekstra, Henk; van der Burg, Remco F. J.; Viola, Massimo

2018-07-01

We measure the gravitational lensing signal around satellite galaxies in a sample of galaxy clusters at z measurements of faint, background sources in the vicinity of bright satellite galaxies. We find a small but significant bias, as light from the lenses makes the shapes of background galaxies appear radially aligned with the lens. We account for this bias by applying a correction that depends on both lens size and magnitude. We also correct for contamination of the source sample by cluster members. We use a physically motivated definition of subhalo mass, namely the mass bound to the subhalo, mbg, similar to definitions used by common subhalo finders in numerical simulations. Binning the satellites by stellar mass we provide a direct measurement of the subhalo-to-stellar-mass relation, log mbg/M⊙ = (11.54 ± 0.05) + (0.95 ± 0.10)log [m⋆/(2 × 1010 M⊙)]. This best-fitting relation implies that, at a stellar mass m⋆ ˜ 3 × 1010 M⊙, subhalo masses are roughly 50 per cent of those of central galaxies, and this fraction decreases at higher stellar masses. We find some evidence for a sharp change in the total-to-stellar mass ratio around the clusters' scale radius, which could be interpreted as galaxies within the scale radius having suffered more strongly from tidal stripping, but remain cautious regarding this interpretation.

Deriving Stellar Masses for the ALFALFA α.100 Sample

Science.gov (United States)

Hess, Logan; Cornell 2017 Summer REU

2018-01-01

For this project, we explore different methods of deriving the stellar masses of galaxies in the ALFALFA (Arecibo Legacy Fast ALFA) α.100 survey. In particular, we measure the effectiveness of SED (Spectral Energy Distribution) on the sample. SED fitting was preformed by MAGPHYS (Multi-wavelength Analysis of Galaxy Physical Properties), utilizing a wide range of photometry in the UV, optical, and IR bands. Photometry was taken from GALAX GR6/7 (UV), SDSS DR13 (optical), WISE All-Sky (near-IR), and Herschel PACS/SPIRE (far-IR). The efficiency of SED fitting increases with a broader range of photometry, however detection rates varied significantly across the different bands. Using a more “comprehensive” sample of galaxies, the GSWLC-A (GALAX, SDSS, WISE Legacy Catalog All-Sky Survey), we aimed to measure which combination of bands provided the largest sample return with the lowest amount of uncertainty, which could then be used to estimate the masses of the galaxies in the α.100 sample.

MEASUREMENT OF THE MASS AND STELLAR POPULATION DISTRIBUTION IN M82 WITH THE LBT

Energy Technology Data Exchange (ETDEWEB)

Greco, Johnny P.; Martini, Paul; Thompson, Todd A., E-mail: greco.40@buckeyemail.osu.edu [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States)

2012-09-20

We present a K-band spectroscopic study of the stellar and gas kinematics, mass distribution, and stellar populations of the archetypical starburst galaxy M82. Our results are based on a single spectrum at a position angle of 67.{sup 0}5 through the K-band nucleus. We used the {sup 12}CO stellar absorption band head at 2.29 {mu}m (CO{sub 2.29}) to measure the rotation curve out to nearly 4 kpc radius on both the eastern and western sides of the galaxy. Our data show that the rotation curve is flat from 1 to 4 kpc. This stands in sharp contrast to some previous studies, which have interpreted H I and CO emission-line position-velocity diagrams as evidence for a declining rotation curve. The kinematics of the Br{gamma}, H{sub 2}, and He I emission lines are consistent with, although characterized by slightly higher velocities than, the stellar kinematics. We derived M82's mass distribution from our stellar kinematic measurements and estimate that its total dynamical mass is {approx}10{sup 10} M{sub Sun }. We measured the equivalent width of CO{sub 2.29} (W{sub 2.29}) as a function of distance from the center of the galaxy to investigate the spatial extent of the red supergiant (RSG) population. The variation in W{sub 2.29} with radius clearly shows that RSGs dominate the light inside 500 pc radius. M82's superwind is likely launched from this region, where we estimate that the enclosed mass is {approx}<2 Multiplication-Sign 10{sup 9} M{sub Sun }.

Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy.

Science.gov (United States)

Geach, J E; Hickox, R C; Diamond-Stanic, A M; Krips, M; Rudnick, G H; Tremonti, C A; Sell, P H; Coil, A L; Moustakas, J

2014-12-04

Recent observations have revealed that starburst galaxies can drive molecular gas outflows through stellar radiation pressure. Molecular gas is the phase of the interstellar medium from which stars form, so these outflows curtail stellar mass growth in galaxies. Previously known outflows, however, involve small fractions of the total molecular gas content and have typical scales of less than a kiloparsec. In at least some cases, input from active galactic nuclei is dynamically important, so pure stellar feedback (the momentum return into the interstellar medium) has been considered incapable of rapidly terminating star formation on galactic scales. Molecular gas has been detected outside the galactic plane of the archetypal starburst galaxy M82 (refs 4 and 5), but so far there has been no evidence that starbursts can propel substantial quantities of cold molecular gas to the same galactocentric radius (about 10 kiloparsecs) as the warmer gas that has been traced by metal ion absorbers in the circumgalactic medium. Here we report observations of molecular gas in a compact (effective radius 100 parsecs) massive starburst galaxy at redshift 0.7, which is known to drive a fast outflow of ionized gas. We find that 35 per cent of the total molecular gas extends approximately 10 kiloparsecs, and one-third of this extended gas has a velocity of up to 1,000 kilometres per second. The kinetic energy associated with this high-velocity component is consistent with the momentum flux available from stellar radiation pressure. This demonstrates that nuclear bursts of star formation are capable of ejecting large amounts of cold gas from the central regions of galaxies, thereby strongly affecting their evolution by truncating star formation and redistributing matter.

Host galaxy properties of mergers of stellar binary black holes and their implications for advanced LIGO gravitational wave sources

Science.gov (United States)

Cao, Liang; Lu, Youjun; Zhao, Yuetong

2018-03-01

Understanding the host galaxy properties of stellar binary black hole (SBBH) mergers is important for revealing the origin of the SBBH gravitational wave sources detected by advanced LIGO and helpful for identifying their electromagnetic counterparts. Here, we present a comprehensive analysis of the host galaxy properties of SBBHs by implementing semi-analytical recipes for SBBH formation and merger into cosmological galaxy formation model. If the time delay between SBBH formation and merger ranges from ≲ Gyr to the Hubble time, SBBH mergers at redshift z ≲ 0.3 occur preferentially in big galaxies with stellar mass M* ≳ 2 × 1010 M⊙ and metallicities Z peaking at ˜0.6 Z⊙. However, the host galaxy stellar mass distribution of heavy SBBH mergers (M•• ≳ 50 M⊙) is bimodal with one peak at ˜109 M⊙ and the other peak at ˜2 × 1010 M⊙. The contribution fraction from host galaxies with Z ≲ 0.2 Z⊙ to heavy mergers is much larger than that to less heavy mergers. If SBBHs were formed in the early Universe (e.g. z > 6), their mergers detected at z ≲ 0.3 occur preferentially in even more massive galaxies with M* > 3 × 1010 M⊙ and in galaxies with metallicities mostly ≳ 0.2 Z⊙ and peaking at Z ˜ 0.6 Z⊙, due to later cosmic assembly and enrichment of their host galaxies. SBBH mergers at z ≲ 0.3 mainly occur in spiral galaxies, but the fraction of SBBH mergers that occur in elliptical galaxies can be significant if those SBBHs were formed in the early Universe; and about two-thirds of those mergers occur in the central galaxies of dark matter haloes. We also present results on the host galaxy properties of SBBH mergers at higher redshift.

RECONCILING THE OBSERVED STAR-FORMING SEQUENCE WITH THE OBSERVED STELLAR MASS FUNCTION

International Nuclear Information System (INIS)

Leja, Joel; Van Dokkum, Pieter G.; Franx, Marijn; Whitaker, Katherine E.

2015-01-01

We examine the connection between the observed star-forming sequence (SFR ∝ M α ) and the observed evolution of the stellar mass function in the range 0.2 < z < 2.5. We find that the star-forming sequence cannot have a slope α ≲ 0.9 at all masses and redshifts because this would result in a much higher number density at 10 < log (M/M ☉ ) < 11 by z = 1 than is observed. We show that a transition in the slope of the star-forming sequence, such that α = 1 at log (M/M ☉ ) < 10.5 and α = 0.7-0.13z (Whitaker et al.) at log (M/M ☉ ) > 10.5, greatly improves agreement with the evolution of the stellar mass function. We then derive a star-forming sequence that reproduces the evolution of the mass function by design. This star-forming sequence is also well described by a broken power law, with a shallow slope at high masses and a steep slope at low masses. At z = 2, it is offset by ∼0.3 dex from the observed star-forming sequence, consistent with the mild disagreement between the cosmic star formation rate (SFR) and recent observations of the growth of the stellar mass density. It is unclear whether this problem stems from errors in stellar mass estimates, errors in SFRs, or other effects. We show that a mass-dependent slope is also seen in other self-consistent models of galaxy evolution, including semianalytical, hydrodynamical, and abundance-matching models. As part of the analysis, we demonstrate that neither mergers nor hidden low-mass quiescent galaxies are likely to reconcile the evolution of the mass function and the star-forming sequence. These results are supported by observations from Whitaker et al

A direct measurement of the baryonic mass function of galaxies & implications for the galactic baryon fraction

NARCIS (Netherlands)

Papastergis, Emmanouil; Cattaneo, Andrea; Huang, Shan; Giovanelli, Riccardo; Haynes, Martha P.

2012-01-01

We use both an HI-selected and an optically-selected galaxy sample to directly measure the abundance of galaxies as a function of their "baryonic" mass (stars + atomic gas). Stellar masses are calculated based on optical data from the Sloan Digital Sky Survey (SDSS) and atomic gas masses are

Connecting traces of galaxy evolution: the missing core mass-morphological fine structure relation

Science.gov (United States)

Bonfini, P.; Bitsakis, T.; Zezas, A.; Duc, P.-A.; Iodice, E.; González-Martín, O.; Bruzual, G.; González Sanoja, A. J.

2018-01-01

Deep exposure imaging of early-type galaxies (ETGs) are revealing the second-order complexity of these objects, which have been long considered uniform, dispersion-supported spheroidals. `Fine structure' features (e.g. ripples, plumes, tidal tails, rings) as well as depleted stellar cores (i.e. central light deficits) characterize a number of massive ETG galaxies, and can be interpreted as the result of galaxy-galaxy interactions. We discuss how the time-scale for the evolution of cores and fine structures are comparable, and hence it is expected that they develop in parallel after the major interaction event which shaped the ETG. Using archival data, we compare the `depleted stellar mass' (i.e. the mass missing from the depleted stellar core) against the prominence of the fine structure features, and observe that they correlate inversely. This result confirms our expectation that, while the supermassive black hole (SMBH) binary (constituted by the SMBHs of the merger progenitors) excavates the core via three-body interactions, the gravitational potential of the newborn galaxy relaxes, and the fine structures fade below detection levels. We expect the inverse correlation to hold at least within the first Gyr from the merger which created the SMBH binary; after then, the fine structure evolves independently.

Timing the formation and assembly of early-type galaxies via spatially resolved stellar populations analysis

Science.gov (United States)

Martín-Navarro, Ignacio; Vazdekis, Alexandre; Falcón-Barroso, Jesús; La Barbera, Francesco; Yıldırım, Akın; van de Ven, Glenn

2018-04-01

To investigate star formation and assembly processes of massive galaxies, we present here a spatially resolved stellar population analysis of a sample of 45 elliptical galaxies (Es) selected from the Calar Alto Legacy Integral Field Area survey. We find rather flat age and [Mg/Fe] radial gradients, weakly dependent on the effective velocity dispersion of the galaxy within half-light radius. However, our analysis shows that metallicity gradients become steeper with increasing galaxy velocity dispersion. In addition, we have homogeneously compared the stellar population gradients of our sample of Es to a sample of nearby relic galaxies, i.e. local remnants of the high-z population of red nuggets. This comparison indicates that, first, the cores of present-day massive galaxies were likely formed in gas-rich, rapid star formation events at high redshift (z ≳ 2). This led to radial metallicity variations steeper than observed in the local Universe, and positive [Mg/Fe] gradients. Secondly, our analysis also suggests that a later sequence of minor dry mergers, populating the outskirts of early-type galaxies (ETGs), flattened the pristine [Mg/Fe] and metallicity gradients. Finally, we find a tight age-[Mg/Fe] relation, supporting that the duration of the star formation is the main driver of the [Mg/Fe] enhancement in massive ETGs. However, the star formation time-scale alone is not able to fully explain our [Mg/Fe] measurements. Interestingly, our results match the expected effect that a variable stellar initial mass function would have on the [Mg/Fe] ratio.

Mapping stellar content to dark matter haloes - III. Environmental dependence and conformity of galaxy colours

Science.gov (United States)

Zu, Ying; Mandelbaum, Rachel

2018-05-01

Recent studies suggest that the quenching properties of galaxies are correlated over several megaparsecs. The large-scale `galactic conformity' phenomenon around central galaxies has been regarded as a potential signature of `galaxy assembly bias' or `pre-heating', both of which interpret conformity as a result of direct environmental effects acting on galaxy formation. Building on the iHOD halo quenching framework developed in Zu and Mandelbaum, we discover that our fiducial halo mass quenching model, without any galaxy assembly bias, can successfully explain the overall environmental dependence and the conformity of galaxy colours in Sloan Digital Sky Survey, as measured by the mark correlation functions of galaxy colours and the red galaxy fractions around isolated primaries, respectively. Our fiducial iHOD halo quenching mock also correctly predicts the differences in the spatial clustering and galaxy-galaxy lensing signals between the more versus less red galaxy subsamples, split by the red-sequence ridge line at fixed stellar mass. Meanwhile, models that tie galaxy colours fully or partially to halo assembly bias have difficulties in matching all these observables simultaneously. Therefore, we demonstrate that the observed environmental dependence of galaxy colours can be naturally explained by the combination of (1) halo quenching and (2) the variation of halo mass function with environment - an indirect environmental effect mediated by two separate physical processes.

THE STELLAR AND GAS KINEMATICS OF THE LITTLE THINGS DWARF IRREGULAR GALAXY NGC 1569

Energy Technology Data Exchange (ETDEWEB)

Johnson, Megan [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Hunter, Deidre A.; Zhang, Hong-Xin; Herrmann, Kimberly [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Oh, Se-Heon [International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Elmegreen, Bruce [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Hts., NY 10598 (United States); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, AL10 9AB (United Kingdom); Tollerud, Erik, E-mail: mjohnson@nrao.edu, E-mail: dah@lowell.edu, E-mail: hxzhang@lowell.edu, E-mail: herrmann@lowell.edu, E-mail: se-heon.oh@uwa.edu.au, E-mail: bge@us.ibm.com, E-mail: E.Brinks@herts.ac.uk, E-mail: etolleru@uci.edu [Center For Cosmology, Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States)

2012-11-01

In order to understand the formation and evolution of Magellanic-type dwarf irregular (dIm) galaxies, one needs to understand their three-dimensional structure. We present measurements of the stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy. The stellar vertical velocity dispersion, {sigma}{sub z}, coupled with the maximum rotational velocity derived from H I observations, V{sub max}, gives a measure of how kinematically hot the galaxy is, and, therefore, indicates its structure. We conclude that the stars in NGC 1569 are in a thick disk with a V{sub max}/{sigma}{sub z} = 2.4 {+-} 0.7. In addition to the structure, we analyze the ionized gas kinematics from O III observations along the morphological major axis. These data show evidence for outflow from the inner starburst region and a potential expanding shell near supermassive star cluster (SSC) A. When compared to the stellar kinematics, the velocity dispersion of the stars increases in the region of SSC A supporting the hypothesis of an expanding shell. The stellar kinematics closely follow the motion of the gas. Analysis of high-resolution H I data clearly reveals the presence of an H I cloud that appears to be impacting the eastern edge of NGC 1569. Also, an ultra-dense H I cloud can be seen extending to the west of the impacting H I cloud. This dense cloud is likely the remains of a dense H I bridge that extended through what is now the central starburst area. The impacting H I cloud was the catalyst for the starburst, thus turning the dense gas into stars over a short timescale, {approx}1 Gyr. We performed a careful study of the spectral energy distribution using infrared, optical, and ultraviolet photometry, producing a state-of-the-art mass model for the stellar disk. This mass modeling shows that stars dominate the gravitational potential in the inner 1 kpc. The dynamical mass of NGC 1569, derived from V{sub max}, shows that the disk may be dark matter deficient in the inner

Correlation between the Total Gravitating Mass of Groups and Clusters and the Supermassive Black Hole Mass of Brightest Galaxies

Science.gov (United States)

Bogdán, Ákos; Lovisari, Lorenzo; Volonteri, Marta; Dubois, Yohan

2018-01-01

Supermassive black holes (BHs) residing in the brightest cluster galaxies are over-massive relative to the stellar bulge mass or central stellar velocity dispersion of their host galaxies. As BHs residing at the bottom of the galaxy cluster’s potential well may undergo physical processes that are driven by the large-scale characteristics of the galaxy clusters, it is possible that the growth of these BHs is (indirectly) governed by the properties of their host clusters. In this work, we explore the connection between the mass of BHs residing in the brightest group/cluster galaxies (BGGs/BCGs) and the virial temperature, and hence total gravitating mass, of galaxy groups/clusters. To this end, we investigate a sample of 17 BGGs/BCGs with dynamical BH mass measurements and utilize XMM-Newton X-ray observations to measure the virial temperatures and infer the {M}500 mass of the galaxy groups/clusters. We find that the {M}{BH}{--}{kT} relation is significantly tighter and exhibits smaller scatter than the {M}{BH}{--}{M}{bulge} relations. The best-fitting power-law relations are {{log}}10({M}{BH}/{10}9 {M}ȯ )=0.20+1.74{{log}}10({kT}/1 {keV}) and {{log}}10({M}{BH}/{10}9 {M}ȯ ) = -0.80+1.72{{log}}10({M}{bulge}/{10}11 {M}ȯ ). Thus, the BH mass of BGGs/BCGs may be set by physical processes that are governed by the properties of the host galaxy group/cluster. These results are confronted with the Horizon-AGN simulation, which reproduces the observed relations well, albeit the simulated relations exhibit notably smaller scatter.

Clustered star formation and the origin of stellar masses.

Science.gov (United States)

Pudritz, Ralph E

2002-01-04

Star clusters are ubiquitous in galaxies of all types and at all stages of their evolution. We also observe them to be forming in a wide variety of environments, ranging from nearby giant molecular clouds to the supergiant molecular clouds found in starburst and merging galaxies. The typical star in our galaxy and probably in others formed as a member of a star cluster, so star formation is an intrinsically clustered and not an isolated phenomenon. The greatest challenge regarding clustered star formation is to understand why stars have a mass spectrum that appears to be universal. This review examines the observations and models that have been proposed to explain these fundamental issues in stellar formation.

The Constant Average Relationship Between Dust-obscured Star Formation and Stellar Mass from z=0 to z=2.5

Science.gov (United States)

Whitaker, Katherine E.; Pope, Alexandra; Cybulski, Ryan; Casey, Caitlin M.; Popping, Gergo; Yun, Min; 3D-HST Collaboration

2018-01-01

The total star formation budget of galaxies consists of the sum of the unobscured star formation, as observed in the rest-frame ultraviolet (UV), together with the obscured component that is absorbed and re-radiated by dust grains in the infrared. We explore how the fraction of obscured star formation depends (SFR) and stellar mass for mass-complete samples of galaxies at 0 MIPS 24μm photometry in the well-studied 5 extragalactic CANDELS fields. We find a strong dependence of the fraction of obscured star formation (f_obscured=SFR_IR/SFR_UV+IR) on stellar mass, with remarkably little evolution in this fraction with redshift out to z=2.5. 50% of star formation is obscured for galaxies with log(M/M⊙)=9.4 although unobscured star formation dominates the budget at lower masses, there exists a tail of low mass extremely obscured star-forming galaxies at z > 1. For log(M/M⊙)>10.5, >90% of star formation is obscured at all redshifts. We also show that at fixed total SFR, f_obscured is lower at higher redshift. At fixed mass, high-redshift galaxies are observed to have more compact sizes and much higher star formation rates, gas fractions and hence surface densities (implying higher dust obscuration), yet we observe no redshift evolution in f_obscured with stellar mass. This poses a challenge to theoretical models to reproduce, where the observed compact sizes at high redshift seem in tension with lower dust obscuration.

Evidence of Cosmic Evolution of the Stellar Initial Mass Function

Science.gov (United States)

van Dokkum, Pieter G.

2008-02-01

Theoretical arguments and indirect observational evidence suggest that the stellar IMF may evolve with time, such that it is more weighted toward high-mass stars at higher redshift. Here we test this idea by comparing the rate of luminosity evolution of massive early-type galaxies in clusters at 0.02 measured evolution of the M/LB ratio gives x = - 0.3+ 0.4-0.7 for the logarithmic slope of the IMF in the region around 1 M⊙, significantly flatter than the present-day value in the Milky Way disk of x = 1.3 +/- 0.3. The best-fitting luminosity-weighted formation redshift of the stars in massive cluster galaxies is 3.7+ 2.3-0.8, and a possible interpretation is that the characteristic mass mc had a value of ~2 M⊙ at z ~ 4 (compared to mc ~ 0.1 M⊙ today), in qualitative agreement with models in which the characteristic mass is a function of the Jeans mass in molecular clouds. Such a "bottom-light" IMF for massive cluster galaxies has significant implications for the interpretation of measurements of galaxy formation and evolution. Applying a simple form of IMF evolution to literature data, we find that the volume-averaged SFR at high redshift may have been overestimated (by a factor of 3-4 at z > 4), and the cosmic star formation history may have a fairly well defined peak at z ~ 1.5. The M/LV ratios of galaxies are less affected than their SFRs, and future data on the stellar mass density at z > 3 will provide further constraints on IMF evolution. The formal errors likely underestimate the uncertainties, and confirmation of these results requires a larger sample of clusters and the inclusion of redder rest-frame colors in the analysis. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Stellar orbits in the Galaxy and mass extinctions on the Earth: a connection?

Science.gov (United States)

Porto de Mello, G. F.; Dias, W. S.; Lepine, J.; Lorenzo-Oliveira, D.; Kazu, R. S.

2014-03-01

The orbits of the stars in the disk of the Galaxy, and their passages through the Galactic spiral arms, are a rarely mentioned factor of biosphere stability which might be important for long-term planetary climate evolution, with a possible bearing on mass extinctions. The Sun lies very near the co-rotation radius, where stars revolve around the Galaxy in the same period as the density wave perturbations of the spiral arms (Dias & Lepine 2005). Conventional wisdom generally considers that this status makes for few passages through the spiral arms. Controversy still surrounds whether time spent inside or around spiral arms is dangerous to biospheres and conducive to mass extinctions (Bailer-Jones 2009). Possible threats include giant molecular clouds disturbing the Oort comet cloud and provoking heavy bombardment (Clube & Napier 1982); a higher exposure to cosmic rays near star forming regions triggering increased cloudiness in Earth's atmosphere and ice ages (Gies & Helsel 2005); and the destruction of Earth's ozone layer posed by supernova explosions (Gehrels et al 2003). We present detailed calculations of the history of spiral arm passages for all 212 solartype stars nearer than 20 parsecs, including the total time spent inside the spiral arms in the last 500 million years, when the spiral arm position can be traced with good accuracy. There is a very large diversity of stellar orbits amongst solar neighborhood solar-type stars, and the time fraction spent inside spiral arms can vary from a few percent to nearly half the time. The Sun, despite its proximity to the galactic co-rotation radius, has exceptionally low eccentricity and a low vertical velocity component, and therefore spends 40% of its lifetime crossing the spiral arms, more than nearly all nearby stars. We discuss the possible implications of this fact to the long-term habitability of the Earth, and possible correlations of the Sun's passage through the spiral arms with the five great mass

Galaxy And Mass Assembly (GAMA): The mechanisms for quiescent galaxy formation at z < 1

Science.gov (United States)

Rowlands, K.; Wild, V.; Bourne, N.; Bremer, M.; Brough, S.; Driver, S. P.; Hopkins, A. M.; Owers, M. S.; Phillipps, S.; Pimbblet, K.; Sansom, A. E.; Wang, L.; Alpaslan, M.; Bland-Hawthorn, J.; Colless, M.; Holwerda, B. W.; Taylor, E. N.

2018-01-01

One key problem in astrophysics is understanding how and why galaxies switch off their star formation, building the quiescent population that we observe in the local Universe. From the Galaxy And Mass Assembly and VIsible MultiObject Spectrograph Public Extragalactic Redshift surveys, we use spectroscopic indices to select quiescent and candidate transition galaxies. We identify potentially rapidly transitioning post-starburst (PSB) galaxies and slower transitioning green-valley galaxies. Over the last 8 Gyr, the quiescent population has grown more slowly in number density at high masses ({M}_\\ast >10^{11}{M_{⊙}) than at intermediate masses ({M}_\\ast >10^{10.6}{M_{⊙}). There is evolution in both the PSB and green-valley stellar mass functions, consistent with higher mass galaxies quenching at earlier cosmic times. At intermediate masses ({M}_\\ast >10^{10.6}{M_{⊙}), we find a green-valley transition time-scale of 2.6 Gyr. Alternatively, at z ∼ 0.7, the entire growth rate could be explained by fast-quenching PSB galaxies, with a visibility time-scale of 0.5 Gyr. At lower redshift, the number density of PSBs is so low that an unphysically short visibility window would be required for them to contribute significantly to the quiescent population growth. The importance of the fast-quenching route may rapidly diminish at z 10^{11}{M_{⊙}), there is tension between the large number of candidate transition galaxies compared to the slow growth of the quiescent population. This could be resolved if not all high-mass PSB and green-valley galaxies are transitioning from star forming to quiescent, for example if they rejuvenate out of the quiescent population following the accretion of gas and triggering of star formation, or if they fail to completely quench their star formation.

THE RELATION BETWEEN DYNAMICAL MASS-TO-LIGHT RATIO AND COLOR FOR MASSIVE QUIESCENT GALAXIES OUT TO z ∼ 2 AND COMPARISON WITH STELLAR POPULATION SYNTHESIS MODELS

International Nuclear Information System (INIS)

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

2015-01-01

We explore the relation between the dynamical mass-to-light ratio (M/L) and rest-frame color of massive quiescent galaxies out to z ∼ 2. We use a galaxy sample with measured stellar velocity dispersions in combination with Hubble Space Telescope and ground-based multi-band photometry. Our sample spans a large range in log M dyn /L g (of 1.6 dex) and log M dyn /L K (of 1.3 dex). There is a strong, approximately linear correlation between the M/L for different wavebands and rest-frame color. The root-mean-square scatter in log M dyn /L residuals implies that it is possible to estimate the M/L with an accuracy of ∼0.25 dex from a single rest-frame optical color. Stellar population synthesis (SPS) models with a Salpeter stellar initial mass function (IMF) cannot simultaneously match M dyn /L g versus (g – z) rest-frame and M dyn /L K versus (g – K) rest-frame . By changing the slope of the IMF we are still unable to explain the M/L of the bluest and reddest galaxies. We find that an IMF with a slope between α = 2.35 and α = 1.35 provides the best match. We also explore a broken IMF with a Salpeter slope at M < 1 M ☉ and M > 4 M ☉ and a slope α in the intermediate region. The data favor a slope of α = 1.35 over α = 2.35. Nonetheless, our results show that variations between different SPS models are comparable to the IMF variations. In our analysis we assume that the variation in M/L and color is driven by differences in age, and that other contributions (e.g., metallicity evolution, dark matter) are small. These assumptions may be an important source of uncertainty as galaxies evolve in more complex ways

Evolution of LMC/M33-mass dwarf galaxies in the EAGLE simulation

Science.gov (United States)

Shao, Shi; Cautun, Marius; Deason, Alis J.; Frenk, Carlos S.; Theuns, Tom

2018-06-01

We investigate the population of dwarf galaxies with stellar masses similar to the Large Magellanic Cloud (LMC) and M33 in the EAGLE galaxy formation simulation. In the field, galaxies reside in haloes with stellar-to-halo mass ratios of 1.03^{+0.50}_{-0.31}× 10^{-2} (68% confidence level); systems like the LMC, which have an SMC-mass satellite, reside in haloes about 1.3 times more massive, which suggests an LMC halo mass at infall, M_{200}=3.4^{+1.8}_{-1.2}× 10^{11}{ M_⊙ } (68% confidence level). The colour distribution of dwarfs is bimodal, with the red galaxies (g - r > 0.6) being mostly satellites. The fraction of red LMC-mass dwarfs is 15% for centrals, and for satellites this fraction increases rapidly with host mass: from 10% for satellites of Milky Way (MW)-mass haloes to nearly 90% for satellites of groups and clusters. The quenching timescale, defined as the time after infall when half of the satellites have acquired red colours, decreases with host mass from >5 Gyrs for MW-mass hosts to 2.5 Gyrs for cluster mass hosts. The satellites of MW-mass haloes have higher star formation rates and bluer colours than field galaxies. This is due to enhanced star formation triggered by gas compression shortly after accretion. Both the LMC and M33 have enhanced recent star formation that could be a manifestation of this process. After infall into their MW-mass hosts, the g - r colours of LMC-mass dwarfs become bluer for the first 2 Gyrs, after which they rapidly redden. LMC-mass dwarfs fell into their MW-mass hosts only relatively recently, with more than half having an infall time of less than 3.5 Gyrs.

ON THE SIZE AND COMOVING MASS DENSITY EVOLUTION OF EARLY-TYPE GALAXIES

International Nuclear Information System (INIS)

Van der Wel, Arjen; Bell, Eric F.; Van den Bosch, Frank C.; Gallazzi, Anna; Rix, Hans-Walter

2009-01-01

We present a simple, empirically motivated model that simultaneously predicts the evolution of the mean size and the comoving mass density of massive (>10 11 M sun ) early-type galaxies from z = 2 to the present. First, we demonstrate that some size evolution of the population can be expected simply due to the continuous emergence of early-type galaxies. The Sloan Digital Sky Survey (SDSS) data reveal that in the present-day universe more compact early-type galaxies with a given dynamical mass have older stellar populations. This implies that with increasing look-back time, the more extended galaxies will be more and more absent from the population. In contrast, at a given stellar velocity dispersion, SDSS data show that there is no relation between size and age, which implies that the velocity dispersion can be used to estimate the epoch at which galaxies stopped forming stars, turning into early-type galaxies. Based on this, we define an empirically motivated, redshift-dependent velocity dispersion threshold above which galaxies do not form stars at a significant rate, which we associate with the transformation into early-type galaxies. Applying this 'formation' criterion to a large sample of nearby early-type galaxies, we predict the redshift evolution in the size distribution and the comoving mass density. The resulting evolution in the mean size is roughly half of the observed evolution. Then we include a prescription for the merger histories of galaxies between the 'formation' redshift and the present, based on cosmological simulations of the assembly of dark matter halos. Such mergers after the transformation into an early-type galaxy are presumably dissipationless ('dry'), where the increase in size is expected to be approximately proportional to the increase in mass. This model successfully reproduces the observed evolution since z ∼ 2 in the mean size and in the comoving mass density of early-type galaxies with mass M > 10 11 M sun . We conclude that

THE PROPAGATION OF UNCERTAINTIES IN STELLAR POPULATION SYNTHESIS MODELING. II. THE CHALLENGE OF COMPARING GALAXY EVOLUTION MODELS TO OBSERVATIONS

International Nuclear Information System (INIS)

Conroy, Charlie; Gunn, James E.; White, Martin

2010-01-01

Models for the formation and evolution of galaxies readily predict physical properties such as star formation rates, metal-enrichment histories, and, increasingly, gas and dust content of synthetic galaxies. Such predictions are frequently compared to the spectral energy distributions of observed galaxies via the stellar population synthesis (SPS) technique. Substantial uncertainties in SPS exist, and yet their relevance to the task of comparing galaxy evolution models to observations has received little attention. In the present work, we begin to address this issue by investigating the importance of uncertainties in stellar evolution, the initial stellar mass function (IMF), and dust and interstellar medium (ISM) properties on the translation from models to observations. We demonstrate that these uncertainties translate into substantial uncertainties in the ultraviolet, optical, and near-infrared colors of synthetic galaxies. Aspects that carry significant uncertainties include the logarithmic slope of the IMF above 1 M sun , dust attenuation law, molecular cloud disruption timescale, clumpiness of the ISM, fraction of unobscured starlight, and treatment of advanced stages of stellar evolution including blue stragglers, the horizontal branch, and the thermally pulsating asymptotic giant branch. The interpretation of the resulting uncertainties in the derived colors is highly non-trivial because many of the uncertainties are likely systematic, and possibly correlated with the physical properties of galaxies. We therefore urge caution when comparing models to observations.

Detection of Enhanced Central Mass-to-light Ratios in Low-mass Early-type Galaxies: Evidence for Black Holes?

Science.gov (United States)

Pechetti, Renuka; Seth, Anil; Cappellari, Michele; McDermid, Richard; den Brok, Mark; Mieske, Steffen; Strader, Jay

2017-11-01

We present dynamical measurements of the central mass-to-light ratio (M/L) of a sample of 27 low-mass early-type {{ATLAS}}3{{D}} galaxies. We consider all {{ATLAS}}3{{D}} galaxies with 9.7 text{}}M/L{{s}} are higher than dynamical {\\text{}}M/L{{s}} derived at larger radii and stellar population estimates of the galaxy centers in ˜80% of galaxies, with a median enhancement of ˜14% and a statistical significance of 3.3σ. We show that the enhancement in the central M/L is best described either by the presence of black holes in these galaxies or by radial initial mass function variations. Assuming a black hole model, we derive black hole masses for the sample of galaxies. In two galaxies, NGC 4458 and NGC 4660, the data suggest significantly overmassive black holes, while in most others only upper limits are obtained. We also show that the level of M/L enhancements we see in these early-type galaxy nuclei are consistent with the larger enhancements seen in ultracompact dwarf galaxies (UCDs), supporting the scenario where massive UCDs are created by stripping galaxies of these masses.

The mass-metallicity relations for gas and stars in star-forming galaxies: strong outflow versus variable IMF

Science.gov (United States)

Lian, Jianhui; Thomas, Daniel; Maraston, Claudia; Goddard, Daniel; Comparat, Johan; Gonzalez-Perez, Violeta; Ventura, Paolo

2018-02-01

We investigate the mass-metallicity relations for the gaseous (MZRgas) and stellar components (MZRstar) of local star-forming galaxies based on a representative sample from Sloan Digital Sky Survey Data Release 12. The mass-weighted average stellar metallicities are systematically lower than the gas metallicities. This difference in metallicity increases towards galaxies with lower masses and reaches 0.4-0.8 dex at 109 M⊙ (depending on the gas metallicity calibration). As a result, the MZRstar is much steeper than the MZRgas. The much lower metallicities in stars compared to the gas in low-mass galaxies imply dramatic metallicity evolution with suppressed metal enrichment at early times. The aim of this paper is to explain the observed large difference in gas and stellar metallicity and to infer the origin of the mass-metallicity relations. To this end we develop a galactic chemical evolution model accounting for star formation, gas inflow and outflow. By combining the observed mass-metallicity relation for both gas and stellar components to constrain the models, we find that only two scenarios are able to reproduce the observations. Either strong metal outflow or a steep initial mass function (IMF) slope at early epochs of galaxy evolution is needed. Based on these two scenarios, for the first time we successfully reproduce the observed MZRgas and MZRstar simultaneously, together with other independent observational constraints in the local Universe. Our model also naturally reproduces the flattening of the MZRgas at the high-mass end leaving the MZRstar intact, as seen in observational data.

LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY

International Nuclear Information System (INIS)

McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle; Dolphin, Andrew; Cannon, John M.; Salzer, John J.; Rhode, Katherine L.; Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P.; Girardi, Léo

2015-01-01

Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ∼0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M ⊙ . The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ∼10 −5 M ⊙ yr −1 . The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites

LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY

Energy Technology Data Exchange (ETDEWEB)

McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle [Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street, S.E., University of Minnesota, Minneapolis, MN 55455 (United States); Dolphin, Andrew [Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Cannon, John M. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Salzer, John J.; Rhode, Katherine L. [Department of Astronomy, Indiana University, 727 East 3rd Street, Bloomington, IN 47405 (United States); Adams, Elizabeth A. K. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Giovanelli, Riccardo; Haynes, Martha P. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Girardi, Léo, E-mail: kmcquinn@astro.umn.edu [Osservatorio Astronomico di Padova, INAF, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy)

2015-10-20

Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ∼0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M{sub ⊙}. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ∼10{sup −5} M{sub ⊙} yr{sup −1}. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.

Galaxies in x-ray selected clusters and groups in Dark Energy Survey Data I: Stellar mass growth of bright central galaxies since Z similar to 1.2

Energy Technology Data Exchange (ETDEWEB)

Zhang, Y.; Miller, C.; McKay, T.; Rooney, P.; Evrard, A. E.; Romer, A. K.; Perfecto, R.; Song, J; Desai, S.; Mohr, J. J.; Vikram, V.

2016-01-10

Using the science verification data of the Dark Energy Survey for a new sample of 106 X-ray selected clusters and groups, we study the stellar mass growth of bright central galaxies (BCGs) since redshift z similar to 1.2. Compared with the expectation in a semi-analytical model applied to the Millennium Simulation, the observed BCGs become under-massive/under-luminous with decreasing redshift. We incorporate the uncertainties associated with cluster mass, redshift, and BCG stellar mass measurements into an analysis of a redshift-dependent BCG-cluster mass relation, m(*) proportional to (M-200/1.5 x 10(14)M(circle dot))(0.24 +/- 0.08)(1+z)(-0.19 +/- 0.34), and compare the observed relation to the model prediction. We estimate the average growth rate since z = 1.0 for BCGs hosted by clusters of M-200,M-z = 10(13.8)M(circle dot); at z = 1.0: m(*, BCG) appears to have grown by 0.13 +/- 0.11 dex, in tension at the similar to 2.5 sigma significance level with the 0.40 dex growth rate expected from the semi-analytic model. We show that the build-up of extended intracluster light after z = 1.0 may alleviate this tension in BCG growth rates.

Stellar Mass-gap as a Probe of Halo Assembly History and Concentration: Youth Hidden among Old Fossils

Science.gov (United States)

Deason, A. J.; Conroy, C.; Wetzel, A. R.; Tinker, J. L.

2013-11-01

We investigate the use of the halo mass-gap statistic—defined as the logarithmic difference in mass between the host halo and its most massive satellite subhalo—as a probe of halo age and concentration. A cosmological N-body simulation is used to study N ~ 25, 000 group/cluster-sized halos in the mass range 1012.5 time and concentration. On average, older and more highly concentrated halos have larger halo mass-gaps, and this trend is stronger than the mass-concentration relation over a similar dynamic range. However, there is a large amount of scatter owing to the transitory nature of the satellite subhalo population, which limits the use of the halo mass-gap statistic on an object-by-object basis. For example, we find that 20% of very large halo mass-gap systems (akin to "fossil groups") are young and have likely experienced a recent merger between a massive satellite subhalo and the central subhalo. We relate halo mass-gap to the observable stellar mass-gap via abundance matching. Using a galaxy group catalog constructed from the Sloan Digital Sky Survey Data Release 7, we find that the star formation and structural properties of galaxies at fixed mass show no trend with stellar mass-gap. This is despite a variation in halo age of ≈2.5 Gyr over ≈1.2 dex in stellar mass-gap. Thus, we find no evidence to suggest that the halo formation history significantly affects galaxy properties.

A Multiwavelength Study of POX 52, a Dwarf Seyfert Galaxy with an Intermediate-Mass Black Hole

Science.gov (United States)

Barth, Aaron

2004-07-01

We propose a comprehensive optical, UV, and X-ray investigation of the unique galaxy POX 52. POX 52 is a Seyfert 1 galaxy with unprecedented properties: its host galaxy appears to be a dwarf elliptical, and its stellar velocity dispersion is only 36 km/s. The stellar velocity dispersion and the broad emission-line widths both suggest a black hole mass of order 10^5 solar masses, placing POX 52 in a region of AGN parameter space that is almost completely unexplored at present. We request ACS/HRC imaging to perform a definitive measurement of the host galaxy structure; STIS UV and optical spectroscopy to study the nonstellar continuum and the structure of the broad-line region; and Chandra ACS imaging to detect the X-ray emission from the nucleus and investigate its spectral and variability properties. The results of this program will give a detailed understanding of the host galaxy and accretion properties of one of the very few known black holes in the mass range around 10^5 solar masses.

ENHANCED OFF-CENTER STELLAR TIDAL DISRUPTIONS BY SUPERMASSIVE BLACK HOLES IN MERGING GALAXIES

International Nuclear Information System (INIS)

Liu, F. K.; Chen, Xian

2013-01-01

Off-center stellar tidal disruption flares have been suggested to be a powerful probe of recoiling supermassive black holes (SMBHs) out of galactic centers due to anisotropic gravitational wave radiations. However, off-center tidal flares can also be produced by SMBHs in merging galaxies. In this paper, we computed the tidal flare rates by dual SMBHs in two merging galaxies before the SMBHs become self-gravitationally bounded. We employ an analytical model to calculate the tidal loss-cone feeding rates for both SMBHs, taking into account two-body relaxation of stars, tidal perturbations by the companion galaxy, and chaotic stellar orbits in triaxial gravitational potential. We show that for typical SMBHs with masses 10 7 M ☉ , the loss-cone feeding rates are enhanced by mergers up to Γ ∼ 10 –2 yr –1 , about two orders of magnitude higher than those by single SMBHs in isolated galaxies and about four orders of magnitude higher than those by recoiling SMBHs. The enhancements are mainly due to tidal perturbations by the companion galaxy. We suggest that off-center tidal flares are overwhelmed by those from merging galaxies, making the identification of recoiling SMBHs challenging. Based on the calculated rates, we estimate the relative contributions of tidal flare events by single, binary, and dual SMBH systems during cosmic time. Our calculations show that the off-center tidal disruption flares by un-bound SMBHs in merging galaxies contribute a fraction comparable to that by single SMBHs in isolated galaxies. We conclude that off-center tidal disruptions are powerful tracers of the merging history of galaxies and SMBHs.

EVOLUTION OF THE GALAXY-DARK MATTER CONNECTION AND THE ASSEMBLY OF GALAXIES IN DARK MATTER HALOS

Energy Technology Data Exchange (ETDEWEB)

Yang Xiaohu; Zhang Youcai; Han Jiaxin [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Mo, H. J. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Van den Bosch, Frank C., E-mail: xhyang@shao.ac.cn [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

2012-06-10

We present a new model to describe the galaxy-dark matter connection across cosmic time, which unlike the popular subhalo abundance-matching technique is self-consistent in that it takes account of the facts that (1) subhalos are accreted at different times and (2) the properties of satellite galaxies may evolve after accretion. Using observations of galaxy stellar mass functions (SMFs) out to z {approx} 4, the conditional SMF at z {approx} 0.1 obtained from Sloan Digital Sky Survey galaxy group catalogs, and the two-point correlation function (2PCF) of galaxies at z {approx} 0.1 as a function of stellar mass, we constrain the relation between galaxies and dark matter halos over the entire cosmic history from z {approx} 4 to the present. This relation is then used to predict the median assembly histories of different stellar mass components within dark matter halos (central galaxies, satellite galaxies, and halo stars). We also make predictions for the 2PCFs of high-z galaxies as function of stellar mass. Our main findings are the following: (1) Our model reasonably fits all data within the observational uncertainties, indicating that the {Lambda}CDM concordance cosmology is consistent with a wide variety of data regarding the galaxy population across cosmic time. (2) At low-z, the stellar mass of central galaxies increases with halo mass as M{sup 0.3} and M{sup {approx}>4.0} at the massive and low-mass ends, respectively. The ratio M{sub *,c}/M reveals a maximum of {approx}0.03 at a halo mass M {approx} 10{sup 11.8} h{sup -1} M{sub Sun }, much lower than the universal baryon fraction ({approx}0.17). At higher redshifts the maximum in M{sub *,c}/M remains close to {approx}0.03, but shifts to higher halo mass. (3) The inferred timescale for the disruption of satellite galaxies is about the same as the dynamical friction timescale of their subhalos. (4) The stellar mass assembly history of central galaxies is completely decoupled from the assembly history of its host

ELLIPTICAL GALAXY MASSES OUT TO FIVE EFFECTIVE RADII: THE REALM OF DARK MATTER

International Nuclear Information System (INIS)

Deason, A. J; Belokurov, V.; Evans, N. W.; McCarthy, I. G.

2012-01-01

We estimate the masses of elliptical galaxies out to five effective radii using planetary nebulae and globular clusters as tracers. A sample of 15 elliptical galaxies with a broad variation in mass is compiled from the literature. A distribution function-maximum likelihood analysis is used to estimate the overall potential slope, normalization, and velocity anisotropy of the tracers. We assume power-law profiles for the potential and tracer density and a constant velocity anisotropy. The derived potential power-law indices lie in between the isothermal and Keplerian regime and vary with mass: there is tentative evidence that the less massive galaxies have steeper potential profiles than the more massive galaxies. We use stellar mass-to-light ratios appropriate for either a Chabrier/KTG (Kroupa, Tout and Gilmore) or Salpeter initial mass function to disentangle the stellar and dark matter components. The fraction of dark matter within five effective radii increases with mass, in agreement with several other studies. We employ simple models to show that a combination of star formation efficiency and baryon extent are able to account for this trend. These models are in good agreement with both our measurements out to five effective radii and recent Sloan Lens ACS Survey measurements within one effective radii when a universal Chabrier/KTG initial mass function is adopted.

Unveiling the Low Surface Brightness Stellar Peripheries of Galaxies

Science.gov (United States)

Ferguson, Annette M. N.

2018-01-01

The low surface brightness peripheral regions of galaxies contain a gold mine of information about how minor mergers and accretions have influenced their evolution over cosmic time. Enormous stellar envelopes and copious amounts of faint tidal debris are natural outcomes of the hierarchical assembly process and the search for and study of these features, albeit highly challenging, offers the potential for unrivalled insight into the mechanisms of galaxy growth. Over the last two decades, there has been burgeoning interest in probing galaxy outskirts using resolved stellar populations. Wide-field surveys have uncovered vast tidal debris features and new populations of very remote globular clusters, while deep Hubble Space Telescope photometry has provided exquisite star formation histories back to the earliest epochs. I will highlight some recent results from studies within and beyond the Local Group and conclude by briefly discussing the great potential of future facilities, such as JWST, Euclid, LSST and WFIRST, for major breakthroughs in low surface brightness galaxy periphery science.

The SLUGGS survey: wide-field stellar kinematics of early-type galaxies

Energy Technology Data Exchange (ETDEWEB)

Arnold, Jacob A. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Romanowsky, Aaron J.; Brodie, Jean P.; Woodley, Kristin A. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Forbes, Duncan A.; Blom, Christina; Kartha, Sreeja S.; Pastorello, Nicola; Pota, Vincenzo; Usher, Christopher [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Spitler, Lee R. [Department of Physics and Astronomy, Faculty of Sciences, Macquarie University, Sydney, NSW 2109 (Australia); Foster, Caroline, E-mail: romanow@ucolick.org [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW (Australia)

2014-08-20

We present stellar kinematics of 22 nearby early-type galaxies (ETGs), based on two-dimensional (2D) absorption line stellar spectroscopy out to ∼2-4 R {sub e} (effective radii), as part of the ongoing SLUGGS Survey. The galaxies span a factor of 20 in intrinsic luminosity, as well as a full range of environment and ETG morphology. Our data consist of good velocity resolution (σ{sub inst} ∼ 25 km s{sup –1}) integrated stellar-light spectra extracted from the individual slitlets of custom made Keck/DEIMOS slitmasks. We extract stellar kinematics measurements (V, σ, h {sub 3}, and h {sub 4}) for each galaxy. Combining with literature values from smaller radii, we present 2D spatially resolved maps of the large-scale kinematic structure in each galaxy. We find that the kinematic homogeneity found inside 1 R {sub e} often breaks down at larger radii, where a variety of kinematic behaviors are observed. While central slow rotators remain slowly rotating in their halos, central fast rotators show more diversity, ranging from rapidly increasing to rapidly declining specific angular momentum profiles in the outer regions. There are indications that the outer trends depend on morphological type, raising questions about the proposed unification of the elliptical and lenticular (S0) galaxy families in the ATLAS{sup 3D} survey. Several galaxies in our sample show multiple lines of evidence for distinct disk components embedded in more slowly rotating spheroids, and we suggest a joint photometric-kinematic approach for robust bulge-disk decomposition. Our observational results appear generally consistent with a picture of two-phase (in-situ plus accretion) galaxy formation.

The FMOS-COSMOS survey of star-forming galaxies at z ∼ 1.6. II. The mass-metallicity relation and the dependence on star formation rate and dust extinction

Energy Technology Data Exchange (ETDEWEB)

Zahid, H. J.; Sanders, D. B.; Chu, J.; Hasinger, G. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Kashino, D. [Division of Particle and Astrophysical Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602 (Japan); Silverman, J. D. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwanoha, Kashiwa, 277-8583 (Japan); Kewley, L. J. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Daddi, E. [CEA-Saclay, Service d' Astrophysique, F-91191 Gif-sur-Yvette (France); Renzini, A. [INAF Osservatorio Astronomico di Padova, vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Rodighiero, G. [Dipartimento di Astronomia, Università di Padova, vicolo dell Osservatorio 3, I-35122 Padova (Italy); Nagao, T. [The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302 (Japan); Arimoto, N. [National Astronomical Observatory of Japan, Subaru Telescope, 650 North Aohoku Place, Hilo, HI 96720 (United States); Kartaltepe, J. [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States); Lilly, S. J.; Carollo, C. M. [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-strasse 27, 8093 Zürich (Switzerland); Maier, C. [Vienna University, Department of Astrophysics, Tuerkenschanzstrasse 17, 1180 Vienna (Austria); Geller, M. J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Capak, P. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Ilbert, O. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, 13388, Marseille (France); Kajisawa, M., E-mail: jabran@ifa.hawaii.edu [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama, Ehime 790-8577 (Japan); Collaboration: COSMOS Team; and others

2014-09-01

We investigate the relationships between stellar mass, gas-phase oxygen abundance (metallicity), star formation rate (SFR), and dust content of star-forming galaxies at z ∼ 1.6 using Subaru/FMOS spectroscopy in the COSMOS field. The mass-metallicity (MZ) relation at z ∼ 1.6 is steeper than the relation observed in the local universe. The steeper MZ relation at z ∼ 1.6 is mainly due to evolution in the stellar mass where the MZ relation begins to turnover and flatten. This turnover mass is 1.2 dex larger at z ∼ 1.6. The most massive galaxies at z ∼ 1.6 (∼10{sup 11} M {sub ☉}) are enriched to the level observed in massive galaxies in the local universe. The MZ relation we measure at z ∼ 1.6 supports the suggestion of an empirical upper metallicity limit that does not significantly evolve with redshift. We find an anti-correlation between metallicity and SFR for galaxies at a fixed stellar mass at z ∼ 1.6, which is similar to trends observed in the local universe. We do not find a relation between stellar mass, metallicity, and SFR that is independent of redshift; rather, our data suggest that there is redshift evolution in this relation. We examine the relation between stellar mass, metallicity, and dust extinction, and find that at a fixed stellar mass, dustier galaxies tend to be more metal rich. From examination of the stellar masses, metallicities, SFRs, and dust extinctions, we conclude that stellar mass is most closely related to dust extinction.

The “Building Blocks” of Stellar Halos

Directory of Open Access Journals (Sweden)

Kyle A. Oman

2017-08-01

Full Text Available The stellar halos of galaxies encode their accretion histories. In particular, the median metallicity of a halo is determined primarily by the mass of the most massive accreted object. We use hydrodynamical cosmological simulations from the apostle project to study the connection between the stellar mass, the metallicity distribution, and the stellar age distribution of a halo and the identity of its most massive progenitor. We find that the stellar populations in an accreted halo typically resemble the old stellar populations in a present-day dwarf galaxy with a stellar mass ∼0.2–0.5 dex greater than that of the stellar halo. This suggests that had they not been accreted, the primary progenitors of stellar halos would have evolved to resemble typical nearby dwarf irregulars.

Dwarf galaxy dark matter density profiles inferred from stellar and gas kinematics

International Nuclear Information System (INIS)

Adams, Joshua J.; Simon, Joshua D.; Fabricius, Maximilian H.; Bender, Ralf; Thomas, Jens; Van den Bosch, Remco C. E.; Van de Ven, Glenn; Barentine, John C.; Gebhardt, Karl; Hill, Gary J.; Murphy, Jeremy D.; Swaters, R. A.

2014-01-01

We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low-mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high-resolution integral-field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although two of the seven galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, γ, are generally robust. The mean and standard deviation of the logarithmic slope for the population are γ = 0.67 ± 0.10 when measured in the stars and γ = 0.58 ± 0.24 when measured in the gas. We also find that the halos are not under-concentrated at the radii of half their maximum velocities. Finally, we search for correlations of the DM density profile with stellar velocity anisotropy and other baryonic properties. Two popular mechanisms to explain cored DM halos are an exotic DM component or feedback models that strongly couple the energy of supernovae into repeatedly driving out gas and dynamically heating the DM halos. While such models do not yet have falsifiable predictions that we can measure, we investigate correlations that may eventually be used to test models. We do not find a secondary parameter that strongly correlates with the central DM density slope, but we do find some weak correlations. The central DM density slope weakly correlates with the abundance of α elements in the stellar population, anti-correlates with H I fraction, and anti-correlates with vertical orbital anisotropy. We expect, if anything, the opposite of these

Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

International Nuclear Information System (INIS)

Stewart, K.

2009-01-01

We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies - such as close pair counts, starburst counts, and the morphologically disturbed fraction - likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M > 0.3 mass ratio events into typical L ∼> fL * galaxies follows the simple relation dN/dt ≅ 0.03(1+f)Gyr -1 (1+z) 2.1 . Despite the rapid increase in merger rate with redshift, only a small fraction of > 0.4L * high-redshift galaxies (∼ 3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t 0.3) in the last 700 Myr and conclude that mergers almost certainly play an important role in delivering baryons and influencing the kinematic properties of Lyman Break Galaxies (LBGs)

Intermediate-mass black holes in dwarf galaxies out to redshift ˜ 2.4 in the Chandra COSMOS Legacy Survey

Science.gov (United States)

Mezcua, M.; Civano, F.; Marchesi, S.; Suh, H.; Fabbiano, G.; Volonteri, M.

2018-05-01

We present a sample of 40 AGN in dwarf galaxies at redshifts z ≲ 2.4. The galaxies are drawn from the Chandra COSMOS-Legacy survey as having stellar masses 107 ≤ M* ≤ 3 × 109 M⊙. Most of the dwarf galaxies are star-forming. After removing the contribution from star formation to the X-ray emission, the AGN luminosities of the 40 dwarf galaxies are in the range L0.5-10keV ˜ 1039 - 1044 erg s-1. With 12 sources at z > 0.5, our sample constitutes the highest-redshift discovery of AGN in dwarf galaxies. The record-holder is cid_1192, at z = 2.39 and with L0.5-10keV ˜ 1044 erg s-1. One of the dwarf galaxies has M* = 6.6 × 107 M⊙ and is the least massive galaxy found so far to host an AGN. All the AGN are of type 2 and consistent with hosting intermediate-mass black holes (BHs) with masses ˜104 - 105 M⊙ and typical Eddington ratios >1%. We also study the evolution, corrected for completeness, of AGN fraction with stellar mass, X-ray luminosity, and redshift in dwarf galaxies out to z = 0.7. We find that the AGN fraction for 109 < M* ≤ 3 × 109 M⊙ and LX ˜ 1041 - 1042 erg s-1 is ˜0.4% for z ≤ 0.3 and that it decreases with X-ray luminosity and decreasing stellar mass. Unlike massive galaxies, the AGN fraction seems to decrease with redshift, suggesting that AGN in dwarf galaxies evolve differently than those in high-mass galaxies. Mindful of potential caveats, the results seem to favor a direct collapse formation mechanism for the seed BHs in the early Universe.

Constraining the Stellar Populations and Star Formation Histories of Blue Compact Dwarf Galaxies with SED Fits

Energy Technology Data Exchange (ETDEWEB)

Janowiecki, Steven [International Center for Radio Astronomy Research, M468, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009 (Australia); Salzer, John J.; Zee, Liese van [Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States); Rosenberg, Jessica L. [Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030 (United States); Skillman, Evan, E-mail: steven.janowiecki@uwa.edu.au [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street, SE Minneapolis, MN, 55455 (United States)

2017-02-10

We discuss and test possible evolutionary connections between blue compact dwarf galaxies (BCDs) and other types of dwarf galaxies. BCDs provide ideal laboratories to study intense star formation episodes in low-mass dwarf galaxies, and have sometimes been considered a short-lived evolutionary stage between types of dwarf galaxies. To test these connections, we consider a sample of BCDs as well as a comparison sample of nearby galaxies from the Local Volume Legacy (LVL) survey for context. We fit the multi-wavelength spectral energy distributions (SED, far-ultra-violet to far-infrared) of each galaxy with a grid of theoretical models to determine their stellar masses and star formation properties. We compare our results for BCDs with the LVL galaxies to put BCDs in the context of normal galaxy evolution. The SED fits demonstrate that the star formation events currently underway in BCDs are at the extreme of the continuum of normal dwarf galaxies, both in terms of the relative mass involved and in the relative increase over previous star formation rates. Today’s BCDs are distinctive objects in a state of extreme star formation that is rapidly transforming them. This study also suggests ways to identify former BCDs whose star formation episodes have since faded.

Detection of [O III] at z ∼ 3: A Galaxy Above the Main Sequence, Rapidly Assembling Its Stellar Mass

Science.gov (United States)

Vishwas, Amit; Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen C.; Schoenwald, Justin P.; Stacey, Gordon J.; Higdon, Sarah J. U.; Higdon, James L.; Weiss, Axel; Güsten, Rolf; Menten, Karl M.

2018-04-01

We detect bright emission in the far-infrared (far-IR) fine structure [O III] 88 μm line from a strong lensing candidate galaxy, H-ATLAS J113526.3-014605, hereafter G12v2.43, at z = 3.127, using the second-generation Redshift (z) and Early Universe Spectrometer (ZEUS-2) at the Atacama Pathfinder Experiment Telescope (APEX). This is only the fifth detection of this far-IR line from a submillimeter galaxy at the epoch of galaxy assembly. The observed [O III] luminosity of 7.1 × 109 ≤ft(\\tfrac{10}{μ }\\right) L ⊙ likely arises from H II regions around massive stars, and the amount of Lyman continuum photons required to support the ionization indicate the presence of (1.2–5.2) × 106 ≤ft(\\tfrac{10}{μ }\\right) equivalent O5.5 or higher stars, where μ would be the lensing magnification factor. The observed line luminosity also requires a minimum mass of ∼2 × 108 ≤ft(\\tfrac{10}{μ }\\right) M ⊙ in ionized gas, that is 0.33% of the estimated total molecular gas mass of 6 × 1010 ≤ft(\\tfrac{10}{μ }\\right) M ⊙. We compile multi-band photometry tracing rest-frame ultraviolet to millimeter continuum emission to further constrain the properties of this dusty high-redshift, star-forming galaxy. Via SED modeling we find G12v2.43 is forming stars at a rate of 916 ≤ft(\\tfrac{10}{μ }\\right) M ⊙ yr‑1 and already has a stellar mass of 8 × 1010 ≤ft(\\tfrac{10}{μ }\\right) M ⊙. We also constrain the age of the current starburst to be ≤slant 5 Myr, making G12v2.43 a gas-rich galaxy lying above the star-forming main sequence at z ∼ 3, undergoing a growth spurt, and it could be on the main sequence within the derived gas depletion timescale of ∼66 Myr.

THE CONTRIBUTION OF TP-AGB AND RHeB STARS TO THE NEAR-IR LUMINOSITY OF LOCAL GALAXIES: IMPLICATIONS FOR STELLAR MASS MEASUREMENTS OF HIGH-REDSHIFT GALAXIES

International Nuclear Information System (INIS)

Melbourne, J.; Williams, Benjamin F.; Dalcanton, Julianne J.; Rosenfield, Philip; Weisz, D.

2012-01-01

Using high spatial resolution Hubble Space Telescope WFC3 and Advanced Camera for Surveys imaging of resolved stellar populations, we constrain the contribution of thermally pulsing asymptotic giant branch (TP-AGB) stars and red helium burning (RHeB) stars to the 1.6 μm near-infrared (NIR) luminosities of 23 nearby galaxies, including dwarfs and spirals. The TP-AGB phase contributes as much as 17% of the integrated F160W flux, even when the red giant branch is well populated. The RHeB population contribution can match or even exceed the TP-AGB contribution, providing as much as 21% (18% after a statistical correction for foreground) of the integrated F160W light. We estimate that these two short-lived phases may account for up to 70% of the rest-frame NIR flux at higher redshift. The NIR mass-to-light (M/L) ratio should therefore be expected to vary significantly due to fluctuations in the star formation rate (SFR) over timescales from 25 Myr to several Gyr, an effect that may be responsible for some of the lingering scatter in NIR galaxy scaling relations such as the Tully-Fisher and metallicity-luminosity relations. We compare our observational results to predictions based on optically derived star formation histories and stellar population synthesis (SPS) models, including models based on the 2008 Padova isochrones (used in popular SPS programs) and the updated 2010 Padova isochrones, which shorten the lifetimes of low-mass (old) low-metallicity TP-AGB populations. The updated (2010) SPS models generally reproduce the expected numbers of TP-AGB stars in the sample; indeed, for 65% of the galaxies, the discrepancy between modeled and observed numbers is smaller than the measurement uncertainties. The weighted mean model/data number ratio for TP-AGB stars is 1.5 (1.4 with outliers removed) with a standard deviation of 0.5. The same SPS models, however, give a larger discrepancy in the F160W flux contribution from the TP-AGB stars, overpredicting the flux by a

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

Science.gov (United States)

Bell, Eric F.; VanDerWel, Arjen; Papovich, Casey; Kocevski, Dale; Lotz, Jennifer; McIntosh, Daniel H.; Kartaltepe, Jeyhan; Faber, S. M.; Ferguson, Harry; Koekemoer, Anton;

The SWELLS survey - IV. Precision measurements of the stellar and dark matter distributions in a spiral lens galaxy

NARCIS (Netherlands)

Barnabè, Matteo; Dutton, Aaron A.; Marshall, Philip J.; Auger, Matthew W.; Brewer, Brendon J.; Treu, Tommaso; Bolton, Adam S.; Koo, David C.; Koopmans, Léon V. E.

We construct a fully self-consistent mass model for the lens galaxy SDSS J2141 at redshift 0.14, and use it to improve on previous studies by modelling its gravitational lensing effect, gas rotation curve and stellar kinematics simultaneously. We adopt a very flexible axisymmetric mass model

EXPLORING THE LOW-MASS END OF THE MBH-σ* RELATION WITH ACTIVE GALAXIES

International Nuclear Information System (INIS)

Xiao Ting; Barth, Aaron J.; Greene, Jenny E.; Ludwig, Randi R.; Ho, Luis C.; Bentz, Misty C.; Jiang Yanfei

2011-01-01

We present new measurements of stellar velocity dispersions, using spectra obtained with the Keck Echellette Spectrograph and Imager (ESI) and the Magellan Echellette (MagE), for 76 Seyfert 1 galaxies from the recent catalog of Greene and Ho. These objects were selected from the Sloan Digital Sky Survey (SDSS) to have estimated black hole (BH) masses below 2 x 10 6 M sun . Combining our results with previous ESI observations of similar objects, we obtain an expanded sample of 93 galaxies and examine the relation between BH mass and velocity dispersion (the M BH -σ * relation) for active galaxies with low BH masses. The low-mass active galaxies tend to follow the extrapolation of the M BH -σ * relation of inactive galaxies. Including results for active galaxies of higher BH mass from the literature, we find a zero point α = 7.68 ± 0.08 and slope of β = 3.32 ± 0.22 for the M BH -σ * relation (in the form log M BH = α + βlog (σ * /200 km s -1 )), with intrinsic scatter of 0.46 ± 0.03 dex. This result is consistent, within the uncertainties, with the slope of the M BH -σ * relation for reverberation-mapped active galaxies with BH masses from 10 6 to 10 9 M sun . For the subset of our sample having morphological information from Hubble Space Telescope images, we examine the slope of the M BH -σ * relation separately for subsamples of barred and unbarred host galaxies, and find no significant evidence for a difference in slope. We do find a mild offset between low-inclination and high-inclination disk galaxies, such that more highly inclined galaxies tend to have larger σ * at a given value of BH mass, presumably due to the contribution of disk rotation within the spectroscopic aperture. We also find that the velocity dispersion of the ionized gas, measured from narrow emission lines including [N II] λ6583, [S II] λλ6716, 6731, and the core of [O III] λ5007 (with the blueshifted wing removed), trace the stellar velocity dispersion well for this large

A CHANDRA PERSPECTIVE ON GALAXY-WIDE X-RAY BINARY EMISSION AND ITS CORRELATION WITH STAR FORMATION RATE AND STELLAR MASS: NEW RESULTS FROM LUMINOUS INFRARED GALAXIES

International Nuclear Information System (INIS)

Lehmer, B. D.; Jenkins, L. P.; Alexander, D. M.; Goulding, A. D.; Roberts, T. P.; Bauer, F. E.; Brandt, W. N.; Ptak, A.

2010-01-01

We present new Chandra observations that complete a sample of seventeen (17) luminous infrared galaxies (LIRGs) with D H ∼ 20 cm -2 . The LIRGs in our sample have total infrared (8-1000 μm) luminosities in the range of L IR ∼ (1-8) x 10 11 L sun . The high-resolution imaging and X-ray spectral information from our Chandra observations allow us to measure separately X-ray contributions from active galactic nuclei and normal galaxy processes (e.g., X-ray binaries and hot gas). We utilized total infrared plus UV luminosities to estimate star formation rates (SFRs) and K-band luminosities and optical colors to estimate stellar masses (M * ) for the sample. Under the assumption that the galaxy-wide 2-10 keV luminosity (L gal HX ) traces the combined emission from high-mass X-ray binaries (HMXBs) and low-mass X-ray binaries, and that the power output from these components is linearly correlated with SFR and M * , respectively, we constrain the relation L gal HX = αM * + βSFR. To achieve this, we construct a Chandra-based data set composed of our new LIRG sample combined with additional samples of less actively star-forming normal galaxies and more powerful LIRGs and ultraluminous infrared galaxies (ULIRGs) from the literature. Using these data, we measure best-fit values of α = (9.05 ± 0.37) x 10 28 erg s -1 M -1 sun and β = (1.62 ± 0.22) x 10 39 erg s -1 (M sun yr -1 ) -1 . This scaling provides a more physically meaningful estimate of L gal HX , with ∼0.1-0.2 dex less scatter, than a direct linear scaling with SFR. Our results suggest that HMXBs dominate the galaxy-wide X-ray emission for galaxies with SFR/M * ∼>5.9 x 10 -11 yr -1 , a factor of ∼2.9 times lower than previous estimates. We find that several of the most powerful LIRGs and ULIRGs, with SFR/M * ∼> 10 -9 yr -1 , appear to be X-ray underluminous with respect to our best-fit relation. We argue that these galaxies are likely to contain X-ray binaries residing in compact star-forming regions

Growth problems of stellar black holes in early galaxies

Science.gov (United States)

Orofino, M. C.; Ferrara, A.; Gallerani, S.

2018-06-01

The nature of the seeds of the observed high-z super-massive black holes (SMBH) is unknown. Although different options have been proposed, involving e.g. intermediate mass direct collapse black holes, BH remnants of massive stars remain the most natural explanation. To identify the most favorable conditions (if any) for their rapid growth, we study the accretion rate of a M• = 100M⊙ BH formed in a typical z = 10 galaxy under different conditions (e.g. galaxy structure, BH initial position and velocity). We model the galaxy baryonic content and follow the BH orbit and accretion history for 300 Myr (the time span in 10 > z > 7), assuming the radiation-regulated accretion model by Park & Ricotti (2013). We find that, within the limits of our model, BH seeds cannot grow by more than 30%, suggesting that accretion on light-seed models are inadequate to explain high-z SMBH. We also compute the X-ray emission from such accreting stellar BH population in the [0.5 - 8] keV band and find it comparable to the one produced by high-mass X-ray binaries. This study suggests that early BHs, by X-ray pre-heating of the intergalactic medium at cosmic dawn, might leave a specific signature on the HI 21 cm line power spectrum potentially detectable with SKA.