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Massive Galaxies over Cosmic Time
MGCT Posters

Name Poster
Dr. Santiago Arribas
Integral Field Spectroscopy of Low-z ULIRGs, and Implications in High-z Galaxy Observations
Mr. Adam Bolton
Massachusetts Institute of Technology
Strong Lensing in the SDSS Luminous Red Galaxy Sample
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Ms. Stephanie Juneau
University of Montreal
Star Formation History as a function of Mass in the GDDS Galaxies at 0.5< z < 2
Mr. Nicholas Konidaris
UC Santa Cruz
OII Emission in High-z Red Sequence Galaxies
Ms. Claudia Kretchmer
Johns Hopkins University
Tracing the Hubble Sequence among the most Luminous and Massive galaxies
Dr. Damien Le Borgne
University of Toronto
Constraints on the star formation history of local and distant (z~1) massive galaxies.
Jay Strader
UCO/Lick Observatory
Extragalactic globular clusters and galaxy formation
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MGCT Talks

Name Talk
Dr. Roberto Abraham
Dept. of Astronomy & Astrophysics, University of Toronto
The morphological mix of galaxies in the Gemini Deep Deep Survey
I present the morphological mix of galaxies in the Gemini Deep Deep Survey (GDDS), determined from deep HST ACS observations. This talk will explore how the morphological mix places constraints on formation scenarios consistent with the evolving stellar mass function determined spectroscopically from the GDDS.
Dr. Eric Bell
Max-Planck-Institut fuer Astronomie
Exploring 9 Gyr of massive galaxy evolution using GEMS, COMBO-17 and Spitzer
On behalf of the GEMS, COMBO-17 and MIPS Instrument teams --- The COMBO-17 photometric redshift survey, coupled with the GEMS 2-passband 30'x30' ACS mosaic and 24 micron data from Spitzer allow the exploration of the properties and evolution of massive galaxies since z~1 with unprecedented accuracy. Highlights from our ongoing studies are: i) a factor of 2 or 3 build-up in the stellar mass density in red-sequence and morphologically early-type galaxies between z~1 and the present day, in excellent agreement with the expectations of the Durham semi-analytic galaxy formation model; ii) the red sequence is built up later in the field than in cluster environments, in excellent agreement with model predictions, iii) at z~0.7, the majority of red-sequence galaxies are old, red and dead, and iv) at z~0.7, roughly 30% of galaxies with stellar masses > 10^10 M_sun are starbursting, while at z=0 the fraction is <2% --- the epoch of intense star formation in massive galaxies is essentially over.
Dr. Michael Brown
Princeton University
The Spatial Clustering of Red Galaxies and EROs
We have completed preliminary studies of the spatial clustering of 0.3 < z < 0.9 red galaxies and 0.8 < z < 1.6 Extremely Red Objects, using the initial 1.2 square degree data release of the NOAO Deep Wide-Field Survey (NDWFS). Using photometric redshifts verified with spectroscopy, we have measured the clustering of galaxies selected as a function of restframe color, luminosity and redshift. The spatial clustering (in comoving coordinates) of red galaxies is similar to the clustering of z < 0.3 red galaxies from the 2dF and SDSS. The clustering of red galaxies with redshift is consistent with hierarchical models of galaxy and structure formation, but the full survey area is required for robust tests of these models. Preliminary results using the entire NDWFS Bootes field will be presented.
Dr. Hsiao-Wen Chen
MIT Center for Space Research
Discovery of Massive Evolved Galaxies at z > 3 in the Hubble Ultra Deep Field
We have identified six early-type galaxies at z>2.8 in the central 5.76 arcmin^2 Hubble Ultra Deep Field NICMOS region based on a pronounced broad-band discontinuity between the NICMOS F110W and F160W bandpasses. These galaxies have red observed optical and near-infrared colors (AB_F775W - AB_F160W >= 2) that cannot be explained entirely by dust reddening (indicating advanced age), and their luminosities at rest-frame optical wavelengths suggest a substantial stellar mass. One of the galaxies is detected in X-ray and is likely to have an active nuclear region, while the rest are estimated to be at least 1 Gyr old at z ~ 3 and contain total stellar mass of (0.4 - 9.1) x 10^10 h^{-2} M_\odot. We calculate a cumulative comoving stellar mass density of \rho_star=0.7 - 1.2 x 10^7 h M_\odot Mpc^{-3} for massive evolved galaxies of M > 10^9 h^{-2} M_\odot at z>2.5. Comparison of the stellar mass density confined in galaxies of different types shows that massive evolved galaxies contribute ~ 16 - 28 % of total stellar mass density even at these early epochs. Finally, an analysis of their morphology observed in the ACS and NICMOS images shows that the active galaxy has compact structure, while the rest are less concentrated. The presence of massive evolved galaxies at z ~ 3, when the universe was only 2 Gyr old, suggests that early star formation may have been particularly efficient in massive halos.
Dr. James Colbert
Spitzer Science Center
Extremely Red NICMOS X-ray Sources from the Chandra Deep Fields
We measure the near-infrared properties of 42 X-ray detected sources from the Chandra Deep Fields North and South. We detect all 42 Chandra sources with NICMOS, with 95% brighter than H(AB) = 24.5. We find that X-ray sources are most often in the brightest and most massive galaxies. Neither the X-ray fluxes nor hardness ratios of the sample show any correlation with near-infrared flux, color or morphology. This lack of correlation indicates there is little connection between the two emission mechanisms and is consistent with the near-infrared emission being dominated by starlight rather than a Seyfert non-stellar continuum. Near-infrared X-ray sources make up roughly half of all extremely red (J-H > 1.4) objects. Using a combination of spectroscopic and photometric redshifts, we find the red J-H objects are at high redshifts (z>1.5), which we propose as the primary explanation for their extreme J-H color. Measurement of rest-wavelength absolute B magnitudes shows that X-ray sources are the brightest optical objects at all redshifts, which explains their dominance of the bright end of the red J-H population.
Dr. Romeel Dave
Univ. of Arizona
The Growth of Massive Galaxies in Cosmological Hydrodynamic Simulations
I will present results from the latest hydro simulations of galaxy formation, focusing on global galaxy evolution as traced by massive galaxies out to z~3. These simulations, like others, show that there is no "massive galaxies problem", in the sense that the predicted number density of objects around L* is consistent with available observations. I will then discuss the physics of massive galaxy formation seen in these models, including the physical basis for the high efficiency of star formation in early collapsing halos, the anti-correlation of halo vs. stellar mass formation times, and the overall (un)importance of mergers in galaxy growth. Finally, I will discuss how simulations fail to produce observed color-magnitude relations, and what new physics would be required to fix this discrepancy.
Dr. Carlos De Breuck
Radio Galaxies: The Most Massive Galaxies Known out to z>5?
Powerful radio galaxies are the most luminous galaxies known in K-band out to z=5.2. I will argue that the K-band light is dominated by stellar light rather than direct and scattered contributions from the AGN and from the narrow-line regions. This implies baryonic masses of ~10^12 M_Sun for radio galaxies out to z>4. I shall present the problems in obtaining an accurate estimate of the space density of these massive galaxies, due to the necessary radio selection biasses. On the positive side, the radio selection does not bias against the dust properties. At z>3, the detection rate of radio galaxies increases from <25% to >50%, indicating that they undergo massive bursts of star-formation (>1000 M_Sun/yr). High redshift radio galaxies may thus be the radio-loud counterparts of submm galaxies.
Dr. Arjun Dey
Tracing the Evolution of Early-type Galaxies in the NOAO Deep Wide-Field Survey
The population of early type galaxies contains the bulk of the stellar mass in the low-redshift universe. The NOAO Deep Wide-Field Survey provides the ability to trace the evolution of this population over a large volume and over a wide range in redshift. I will present evidence that suggests that a significant population of these early-type galaxies share a common evolutionary history, with a high formation redshifts and comparable (and declining) star formation histories, with few galaxies, if any, showing any evidence for passive evolution.
Dr. Mark Dickinson
High redshift galaxies from the GOODS Spitzer Legacy program
To Follow
Ms. Michelle Doherty
institute of astronomy, cambridge, uk
"Keck Spectroscopy of Extremely Red Objects: Massive, clustered galaxies at z>1" Andrew Bunker & Michelle Doherty
We present deep optical Keck spectroscopy of ~70 extremely red objects in three well-studied fields. We discuss the division between dusty starbursts and old ellipticals, average ages and the redshift distribution, including the discovery of redshift spikes in some fields.
Peter Eisenhardt
Spitzer/IRAC observations of galaxy clusters to z ~ 2
I will discuss Spitzer/IRAC observations of x-ray and radio selected clusters to z ~ 2. I will also discuss searches for galaxy clusters to z ~ 2 in the NDWFS Bootes field using the IRAC shallow survey.
Dr. Daniel Eisenstein
University of Arizona
Luminous Red Galaxies in the Sloan Digital Sky Survey
I will discuss results from spectroscopic samples of luminous early-type galaxies from the Sloan Digital Sky Survey. The SDSS offers a specially targeted spectroscopic sample of luminous early-type galaxies that extends to redshift 0.5. At present, there are over 60,000 redshifts covering 4000 square degrees. While designed to trace large-scale structure, the sample also provides the means to study the properties and environments of the most massive local galaxies in great detail. I will present work on the spectral properties of these galaxies and on the scale and luminosity dependences in their clustering.
Ms. Dawn Erb
Stellar Populations and Kinematics of Star-forming Galaxies at z~2
We have assembled a sample of several hundred star-forming galaxies at z~2, selected by their rest-frame UV colors and with spectroscopically confirmed redshifts. We use UGRJK photometry and (in one field) mid-IR data from the Spitzer Space Telescope to model their stellar populations, masses and star formation rates. We also use near-IR H-alpha spectra of ~100 of these galaxies to determine dynamical masses and star formation rates. I will compare the stellar masses derived from the photometric modeling with dynamical masses from the width of the H-alpha emission line. I will also discuss correlations between the rest-frame optical luminosity and H-alpha line widths and nebular chemistry. The sample shows considerable diversity in mass, age and metallicity, and intriguing differences with respect to the Lyman break galaxies at z~3, including a significantly larger average velocity dispersion at z~2.
Dr. Adriano Fontana
INAF - Rome Observatory
Galaxy evolution at high z from mass-selected samples
I summarize the recent results from K-selected surveys that allow to trace the evolution of massive galaxies up to $z\simeq 3$. I show that the evolution of the specific star--formation rate, of the stellar mass density and of the stellar mass functions suggest that, at $z>1$, we enter in the epoch This is associated with a change in the physical properties of massive galaxies, with star--forming objects that contribute to a substantial fraction of the observed mass density. I quantitatively show that these results do not pose challenges to current $\Lambda-CDM$ models, but represent valuable constraints to understand the complex physical mechanisms involved in the assembly of massive galaxies.
Dr. Raul Jimenez
University of Pennsylvania
The stellar assembly history of massive galaxies
Using the MOPED algorithm we have recover the baryonic star formation history of the most massive galaxies in the SDSS DR1 galaxy survey. We find that most of the stellar most was already formed at z > 2. We discuss how this can be acommodated within the current LCDM paradigm.
Dr. Patrick McCarthy
Carnegie Observatories
The Genesis and Star Formation Histories of Massive Galaxies
I will review the properties of massive galaxies at 1 < z < 2 with an emphasis on their star formation histories. Roughly half of the stellar mass density at z ~ 2 is in galaxies with spectra dominated by old stars. I will review constraints on the formation redshifts, star formation histories and likely progenitor populations for these objects. The remaining massive objects have star formation histories that appear to have peaked at z ~ 2 and declined very steeply since. The Gemini Deep Deep Survey sample allows us to explore the relationship between stellar mass and star formation. I will discuss the implications of strong Balmer absorption lines in high mass systems and the star formation histories of representative massive systems at z > 1. I will discuss recent ACS imaging that sheds light on the processes that drive star formation in the active objects and the connection between the passive systems and present day early type galaxies.
Dr. Daniel McIntosh
University of Massachusetts, Amherst
Red Early-type Galaxies in GEMS: Evolution of Luminosity and Stellar Mass at Fixed Size Since z=1
We combine HST/ACS imaging from GEMS with redshifts and rest-frame quantities from COMBO-17 to study the evolution of red early-type galaxies since z=1. We use a large sample of nearly 500 field galaxies with rest-frame (U-V) colors on the red-sequence and centrally-concentrated radial profiles (i.e. n>2.5 from Sersic fits). We explore how the rest-frame $V$-band luminosity and stellar mass correlations with intrinsic half-light size change over cosmic time. By direct comparison with the well-defined local relations from SDSS with a full accounting of our sample selection function, we find that the luminosity-size and stellar mass-size relations evolve in a manner that is largely consistent with the aging of an ancient stellar population -- at a given fixed size high-redshift galaxies were brighter and had the same mass within a factor of 2 as their present-day counterparts. We find that red early-type galaxies either evolve along the stellar mass-size relation or appear on the relation. Recent results find a factor of 2 buildup on the red sequence since z=1 with merging playing an important role. Therefore, we conclude that the sizes and the stellar populations of red early-type galaxies do not reflect the merging history of these stellar systems. Last, we find tentative evidence that the amount of luminosity evolution varies between galaxies of given fixed sizes in such a way that least massive galaxies show stronger luminosity evolution, and hence younger stellar populations, compared to more massive early types.
Dr. Bahram Mobasher
Space Telescope Science Institute
Evolution of the Rest-Frame Luminosity Density to z=2 in the GOODS-S field
To Follow
Dr. Kentaro Nagamine
University of California, San Diego
Massive galaxies at z=1-3 in cosmological hydrodynamic simulations
I discuss the properties of massive galaxies at z=1-3 in cosmological hydrodynamic simulations. In particular, I focus on the stellar masses of galaxies and star formation histories, and describe how the hydrodynamic simulations achieve the production of 10^11 Msun galaxies by z=2. Unlike the current semi-analytic models, our models predict the peak of the Madau plot to be at z>=5 and higher stellar mass density at z>1 than the current observational estimates.
Dr. Swara Ravindranath
Space Telescope Science Institute
Starbursts at high redshifts: Building blocks of present-day massive galaxies?
There is growing evidence that most of the stellar mass in galaxies were assembled at high redshifts and the most massive galaxies were already in place by z=1. Lyman Break Galaxies (LBGs) have been argued to be the progenitors of the local spheroid population based on the enhanced levels of star formation activity and high central concentration. However, there have also been quantitative analyses which claim a more extended disk-like configuration or merger morphology for LBGs which appear to be experiencing an intense starburst phase. According to the hierarchical models of galaxy formation these starbursting systems may not necessarily be the direct progenitors of present-day massive galaxies, but could play an important role in spheroid formation through mergers. This talk will focus on the new results on LBG morphology based on quantitative analysis of structural parameters using GOODS images. The sizes, luminosities, morphologies, and star formation rate densities will be discussed in the context of LBGs as possible building blocks of massive galaxies at later epochs.
Dr. Alvio Renzini
Massive Galaxies at z ~ 2 from K20+
Recent results on massive galaxies at z~2 from the K20 survey supplemented by GOODS and other data will be presented. This will include both actively star-forming as well as passively evolving galaxies. A new criterion for efficiently selecting these galaxies from photometric catalogs will also be presented.
Dr. R. Michael Rich
Luminous UV Galaxies: Lyman Break Galaxy Analogs in the Local Universe
Imaging by the Galaxy Evolution Explorer, and identifications in the SDSS DR1, reveals a population of actively star forming galaxies with L_UV >10^10 Lsun and 0.1 < z < 0.4. Many of these galaxies have R_eff<2kpc, thus making them analogs of Lyman Break Galaxies, but in the low redshift Universe. The discovery of this previously unknown class of galaxies is a strong indication that massive galaxy formation continues in the low redshift Universe.
Dr. Sandra Savaglio
Dep. Physics & Astronomy, Johns Hopkins Uni.
Mass-metallicity relation in 0.4<z<1 galaxies
We have investigated the metallicity as a function of stellar mass in galaxies at 0.4<z<1, obtained from the K-band selected Gemini Deep Deep Survey (GDDS). We observe a mass-metallicity relation similar to what seen in z~0.1 galaxies, but with an offset: on average GDDS galaxies at a given metallicity have larger masses. We have also measured masses for the Canada-France Redshift Survey (CFRS) 0.5<z<0.9 sample, for which metallicities are already known, and derived consistent results. Using these samples, and a small sample of z~2.3 LBGs, we propose a redshift dependent mass-metallicity relation. Finally, from the GDDS and CFRS samples together, we found a 0.4<z<1 metallicity-luminosity relation shifted towards higher luminosities, with respect to local galaxies. We interpret this result as due to the observed decrease of the stellar mass-to-light ratio M/L at higher redshift.
Dr. Rachel Somerville
How do the most massive galaxies constrain theories of galaxy formation?
To Follow
Dr. Adam Stanford
Institute for Astronomy, University of Hawaii
The Origin of Massive Galaxies in Proto-clusters of Galaxies
IRAC imaging of high-z proto galaxy clusters is used to constrain the amount of stellar mass in the constituent cluster galaxies. Estimates of the stellar mass content of the member galaxies places limits on their formation ages. By combining with size information derived from HST imaging, we can examine the growth of the galaxies which should become massive early-types in structures which should become massive clusters.
Dr. Tommaso Treu
Ultra-deep spectroscopy of z~1 E+S0 in GOODS-N
We have obtained high-signal to noise ratio and high resolution Keck spectra of 250 early-type galaxies in the GOODS-N field out to redshift 1.25. I will present the first results of this study on the star formation history and stellar mass assembly rate of early-type galaxies over cosmic time.
Dr. Ignacio Trujillo
Max-Planck-Institut fuer Astronomie
The luminosity-size and mass-size relations of galaxies out to z~3
The luminosity-size and stellar mass-size distributions of galaxies out to z~3 is presented. We use very deep near-infrared images of the HDF-S and MS1054 fields in the J, H, and K bands, taken as part FIRES at the VLT, to follow the evolution of the optical rest-frame sizes of galaxies. We find that the rest-frame V-band sizes r_{e,V} of luminous galaxies (L_V>10^{10}h_70^{-2}L_sun) at 2<z<3 are ~60% smaller than for equally luminous galaxies today. In contrast, the mass-size relation has not evolved (or evolved relatively little) since z~3. Both results can be reconciled by the fact that the stellar M/L ratio is lower in the luminous high z galaxies than in nearby ones because they have young stellar populations.
Dr. Lin Yan
Spitzer Science Center, Caltech
Optical/near-IR selected red galaxies at z~1-3.5 -- the mid-infrared view from Spitzer
I will present several results on the Spitzer 24um observations of red galaxies selected with optical or near-IR colors at z ~ 1 and z ~ 2. I will discuss the star formation rates, the spectral properties, masses and high resolution morphologies from the follow-up spectroscopic observations as well as HST imaging data. I will summarize the implications of our findings to our understanding of the assembly of massive galaxies at high redshifts.
Dr. Pieter van Dokkum
A substantial population of massive red galaxies at z~2.5
To Follow
Mr. Arjen van der Wel
Leiden Observatory
The Fundamental Plane at Redshift One
Measuring the evolution of the Fundamental Plane with redshift allows us to directly measure the change of the mass-to-light ratio of the most massive galaxies over time. Studies of cluster galaxies up to z=1.3 have shown that the bulk of the stellar mass in these objects has formed at very high redshifts. It is important to compare the field and cluster populations, because hierarchical formation theories predict that field galaxies are younger. We show that equally massive field and cluster galaxies evolve equally fast, and that previous contradictory results can at least partly be explained by selection effects. Furthermore, we confirm that the change of M/L with redshift and the scatter at a given redshift are due to differences in stellar populations, by showing a clear relation between color and M/L, and spectral age and M/L.