[2] arXiv:0911.1126 [ps, pdf, other] Title: The Build-Up of the Hubble Sequence in the COSMOS Field Authors: P. A. Oesch, C. M. Carollo, R. Feldmann, O. Hahn, S. J. Lilly, M. T. Sargent, C. Scarlata, M. C. Aller, H. Aussel, M. Bolzonella, T. Bschorr, K. Bundy, P. Capak, O. Ilbert, J.-P. Kneib, A. M. Koekemoer, K. Kovac, A. Leauthaud, E. Le Floc'h, R. Massey, H. J. McCracken, L. Pozzetti, A. Renzini, J. Rhodes, M. Salvato, D. B. Sanders, N. Scoville, K. Sheth, Y. Taniguchi, D. Thompson Comments: 5 pages, 3 figures, submitted to ApJL Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We use ~8,600 >5e10 Msol COSMOS galaxies to study how the morphological mix of massive ellipticals, bulge-dominated disks, intermediate-bulge disks, bulge-less disks and irregular galaxies evolves from z=0.2 to z=1. The morphological evolution depends strongly on mass. At M>3e11 Msol, no evolution is detected in the morphological mix: ellipticals dominate since z=1, and the Hubble sequence has quantitatively settled down by this epoch. At the 1e11 Msol mass scale, little evolution is detected, which can be entirely explained with major mergers. Most of the morphological evolution from z=1 to z=0.2 takes place at masses 5e10 - 1e11 Msol, where: (i) The fraction of spirals substantially drops and the contribution of early-types increases. This increase is mostly produced by the growth of bulge-dominated disks, which vary their contribution from ~10% at z=1 to >30% at z=0.2 (cf. the elliptical fraction grows from ~15% to ~20%). Thus, at these masses, transformations from late- to early-types result in disk-less elliptical morphologies with a statistical frequency of only 30% - 40%. Otherwise, the processes which are responsible for the transformations either retain or produce a non-negligible disk component. (ii) The bulge-less disk galaxies, which contribute ~15% to the intermediate-mass galaxy population at z=1, virtually disappear by z=0.2. The merger rate since z=1 is too low to account for the disappearance of these massive bulge-less disks, which most likely grow a bulge via secular evolution. arXiv:0911.1131 [ps, pdf, other] Title: Mergers, AGN, and 'Normal' Galaxies: Contributions to the Distribution of Star Formation Rates and Infrared Luminosity Functions Authors: Philip F. Hopkins (1), Joshua D. Younger (2), Christopher C. Hayward (3), Desika Narayanan (3), Lars Hernquist (3) ((1) Berkeley, (2) IAS, (3) CfA) Comments: 16 pages, 9 figures (+appendices), accepted to MNRAS. A routine to return the galaxy merger rates discussed here is available at this http URL Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR) We use a novel method to predict the contribution of normal star-forming galaxies, merger-induced bursts, and obscured AGN, to IR luminosity functions (LFs) and global SFR densities. We use empirical halo occupation constraints to populate halos with galaxies and determine the distribution of normal and merging galaxies. Each system can then be associated with high-resolution hydrodynamic simulations. We predict the distribution of observed luminosities and SFRs, from different galaxy classes, as a function of redshift from z=0-6. We provide fitting functions for the predicted LFs, quantify the uncertainties, and compare with observations. At all redshifts, 'normal' galaxies dominate the LF at moderate luminosities ~L* (the 'knee'). Merger-induced bursts increasingly dominate at L>>L*; at the most extreme luminosities, AGN are important. However, all populations increase in luminosity at higher redshifts, owing to increasing gas fractions. Thus the 'transition' between normal and merger-dominated sources increases from the LIRG-ULIRG threshold at z~0 to bright Hyper-LIRG thresholds at z~2. The transition to dominance by obscured AGN evolves similarly, at factor of several higher L_IR. At all redshifts, non-merging systems dominate the total luminosity/SFR density, with merger-induced bursts constituting ~5-10% and AGN ~1-5%. Bursts contribute little to scatter in the SFR-stellar mass relation. In fact, many systems identified as 'ongoing' mergers will be forming stars in their 'normal' (non-burst) mode. Counting this as 'merger-induced' star formation leads to a stronger apparent redshift evolution in the contribution of mergers to the SFR density. arXiv:0911.1158 [ps, pdf, other] Title: The Morphology of Passively Evolving Galaxies at z ~ 2 from HST/WFC3 Deep Imaging in the Hubble Ultradeep Field Authors: P. Cassata, M. Giavalisco, Yicheng Guo, H. Ferguson, A. Koekemoer, A. Renzini, A. Fontana, S. Salimbeni, M. Dickinson, S. Casertano, C. J. Conselice, N. Grogin, J. M. Lotz, C. Papovich, R. A. Lucas, A. Straughn, J. P. Gardner, L. Moustakas Comments: 6 pages, 4 figures, submitted to ApJ Letters Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We discuss near--IR images of six passive galaxies (SSFR<10^{-2} Gyr^{-1}) at redshift 1.32 galaxies. This leaves open the possibility that clumpy accretion and mergers remain important in driving the evolution of these starbursts, together with rapid gas accretion through other means. arXiv:0911.1356 [ps, pdf, other] Title: The evolution of z=7-8 galaxies from IRAC observations of the deep/wide-area WFC3/IR ERS and ultradeep WFC3/IR HUDF Authors: I. Labbe, V. Gonzalez, R. J. Bouwens, G. D. Illingworth, M. Franx, M. Trenti, P. A. Oesch, P. G. van Dokkum, M. Stiavelli, C. M. Carollo, M. Kriek, D. Magee Comments: 6 pages, 4 figures, emulateapj Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We investigate the Spitzer/IRAC properties of 36 z~7 z-dropout galaxies and 3 z~8 Y-dropout 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 SEDs to derive mean redshifts, stellar masses, and ages. The z~7 galaxies are best characterized by high ages (>300 Myr) and high M/L. The main trend with decreasing luminosity is that of bluing of the far-UV slope from beta~-2.0 to beta~-3.0. This can be explained by decreasing metallicity, except for the lowest luminosity galaxies (0.1~L^*_{z=3}) where low metallicity with smooth SFHs alone fail to match the blue far-UV and moderately red H-[3.6] color. This may require episodic SFHs with short periods of activity and quiescence ("on-off" cycles) or contribution from emission lines. The stellar mass of our sample of z~7 star forming galaxies correlates with SFR according to log M*= 8.70 (+-0.09) + 1.06 (+-0.10) log SFR. The small scatter ~0.25 dex suggest that the galaxies have similar SFH, on average consistent with CSF since z>10. No galaxies are found with SFRs much higher or lower than the past averaged SFR; strongly rising SFR \propto t^alpha (alpha>1) or exponentially declining tau2 proto-cluster. Both red galaxies in PKS1138-262 are massive, of the order of 4-6x10^11 M_Sol. They lie along a Colour-Magnitude relation which implies that they formed the bulk of their stellar population around z=4. In the MRC0943-242 field we find no red galaxies at the redshift of the radio galaxy but we do confirm the effectiveness of our JHK_s selection of galaxies at 2.3 20 AA) as Lya emitters (LAEs) and the latter group (EW < 20 AA) as non-LAEs. This controlled method of comparing objects from the same UV luminosity distribution represents an improvement over previous studies in which the stellar populations of LBGs and narrowband-selected LAEs were contrasted, where the latter were often intrinsically fainter in broadband filters by an order of magnitude simply due to different selection criteria. Using a variety of statistical tests, we find that Lya equivalent width and age, SFR, and dust extinction, respectively, are significantly correlated in the sense that objects with strong Lya emission also tend to be older, lower in star formation rate, and less dusty than objects with weak Lya emission, or the line in absorption. We accordingly conclude that, within the LBG sample, objects with strong Lya emission represent a later stage of galaxy evolution in which supernovae-induced outflows have reduced the dust covering fraction. We also examined the hypothesis that the attenuation of Lya photons is lower than that of the continuum, as proposed by some, but found no evidence to support this picture. arXiv:0911.2000 [ps, pdf, other] Title: The Relationship Between Stellar Populations and Lyman Alpha Emission in Lyman Break Galaxies Authors: Katherine A. Kornei, Alice E. Shapley, Dawn K. Erb, Charles C. Steidel, Naveen A. Reddy, Max Pettini, Milan Bogosavljevic Comments: 24 pages, 15 figures, submitted to ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We present the results of a photometric and spectroscopic survey of 321 Lyman break galaxies (LBGs) at z ~ 3 to investigate systematically the relationship between Lya emission and stellar populations. Lya equivalent widths (EW) were calculated from rest-frame UV spectroscopy and optical/near-infrared/Spitzer photometry was used in population synthesis modeling to derive the key properties of age, dust extinction, star formation rate (SFR), and stellar mass. We directly compare the stellar populations of LBGs with and without strong Lya emission, where we designate the former group (EW > 20 AA) as Lya emitters (LAEs) and the latter group (EW < 20 AA) as non-LAEs. This controlled method of comparing objects from the same UV luminosity distribution represents an improvement over previous studies in which the stellar populations of LBGs and narrowband-selected LAEs were contrasted, where the latter were often intrinsically fainter in broadband filters by an order of magnitude simply due to different selection criteria. Using a variety of statistical tests, we find that Lya equivalent width and age, SFR, and dust extinction, respectively, are significantly correlated in the sense that objects with strong Lya emission also tend to be older, lower in star formation rate, and less dusty than objects with weak Lya emission, or the line in absorption. We accordingly conclude that, within the LBG sample, objects with strong Lya emission represent a later stage of galaxy evolution in which supernovae-induced outflows have reduced the dust covering fraction. We also examined the hypothesis that the attenuation of Lya photons is lower than that of the continuum, as proposed by some, but found no evidence to support this picture. arXiv:0911.2230 [ps, pdf, other] Title: On the Baryon Fractions in Clusters and Groups of Galaxies Authors: Xinyu Dai (1,2), Joel N. Bregman (2), Christopher S. Kochanek (3), Elena Rasia (2) ((1) University of Oklahoma, (2) University of Michigan, (3) Ohio State University) Comments: 18 pages, 5 figures, submitted to ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We present the baryon fractions of 2MASS groups and clusters as a function of cluster richness using total and gas masses measured from stacked ROSAT X-ray data and stellar masses estimated from the infrared galaxy catalogs. We detect X-ray emission even in the outskirts of clusters, beyond r_200 for richness classes with X-ray temperatures above 1keV. This enables us to more accurately determine the total gas mass in these groups and clusters. We find that the optically selected groups and clusters have flatter temperature profiles and higher stellar-to-gas mass ratios than the individually studied, X-ray bright clusters. We also find that the stellar mass in poor groups with temperatures below 1keV is comparable to the gas mass in these systems. Combining these results with individual measurements for clusters and groups from the literature, we find a break in the baryon fraction at ~1keV. Above this temperature, the baryon fraction scales with temperature as f_b \propto T^0.20\pm0.03. We see significantly smaller baryon fractions below this temperature, and the baryon fraction of poor groups joins smoothly onto that of systems with still shallower potential wells such as normal and dwarf galaxies where the baryon fraction scales with the inferred velocity dispersion as f_b \propto \sigma^1.6. The small scatter in the baryon fraction as any given potential well depth favors a universal baryon loss mechanism and a preheating model for the baryon loss. The scatter is, however, larger for less massive systems. arXiv:0911.2236 [ps, pdf, other] Title: Cosmic Evolution of Virial and Stellar Mass in Early-Type Galaxies Authors: David J. Lagattuta (1), Christopher D. Fassnacht (1), Matthew W. Auger (1,2), Philip J. Marshall (2), Maruša Bradač (2), Tommaso Treu (2), Raphaël Gavazzi (3), Tim Schrabback (4), Cécile Faure (5), Timo Anguita (6) ((1) UC Davis, (2) UC Santa Barbara, (3) IAP, (4) Leiden, (5) EPFL, (6) ARI/ZfA Heidelberg) Comments: 14 pages, 8 figures, submitted to ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We measure the average mass properties of a sample of 41 strong gravitational lenses at moderate redshift (z ~ 0.4 - 0.9), and present the lens redshift for 6 of these galaxies for the first time. Using the techniques of strong and weak gravitational lensing on archival data obtained from the Hubble Space Telescope, we determine that the average mass overdensity profile of the lenses can be fit with a power-law profile (Delta_Sigma prop. to R^{-0.86 +/- 0.16}) that is consistent with an isothermal profile (Delta_Sigma prop. to R^{-1}) with velocity dispersion sigma_v = 260 +/- 20 km/s. Additionally, we use a two-component de Vaucouleurs+NFW model to disentangle the total mass profile into separate luminous and dark matter components, and determine the relative fraction of each component. We measure the average rest frame V-band stellar mass-to-light ratio (Upsilon_V = 4.0 +/- 0.6 h M_sol/L_sol) and virial mass-to-light ratio (tau_V = 300 +/- 90 h M_sol/L_sol) for our sample, resulting in a virial-to-stellar mass ratio of M_vir/M_* = 75 +/- 25. Finally, we compare our results to a previous study using low redshift lenses, to understand how galaxy mass profiles evolve over time. We investigate the evolution of M_vir/M_*(z) = alpha(1+z)^{beta}, and find best fit parameters of alpha = 51 +/- 36 and beta = 0.9 +/- 1.8, constraining the growth of virial to stellar mass ratio over the last ~7 Gigayears. We note that, by using a sample of strong lenses, we are able to constrain the growth of M_vir/M_*(z) without making any assumptions about the IMF of the stellar population. arXiv:0911.2252 [pdf, other] Title: The zCOSMOS-Bright survey: the clustering of galaxy morphological types since z~1 Authors: S. de la Torre, O. Le Fevre, C. Porciani, L. Guzzo, B. Meneux, U. Abbas, L. Tasca, C.M. Carollo, T. Contini, J.-P. Kneib, S.J. Lilly, V. Mainieri, A. Renzini, M. Scodeggio, G. Zamorani, S. Bardelli, M. Bolzonella, A. Bongiorno, K. Caputi, G. Coppa, O. Cucciati, L. de Ravel, P. Franzetti, B. Garilli, A. Iovino, P. Kampczyk, C. Knobel, A.M. Koekemoer, K. Kovac, F. Lamareille, J.-F. Le Borgne, V. Le Brun, C. Maier, M. Mignoli, R. Pello, Y. Peng, E. Perez-Montero, E. Ricciardelli, J. Silverman, M. Tanaka, L. Tresse, D. Vergani, E. Zucca, D. Bottini, A. Cappi, P. Cassata, A. Cimatti, A. Leauthaud, D. Maccagni, C. Marinoni, H.J. McCracken, P. Memeo, P. Oesch, L. Pozzetti, R. Scaramella Comments: 12 pages, 10 figures. Submitted to MNRAS Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We study the dependence of the clustering of galaxies on their morphological type, over the unprecedented redshift interval 0.2 < z < 0.9. This is made possible in the COSMOS field by the unique combination of high-resolution HST imaging with VLT spectroscopy for ~10,000 galaxies to I(AB) = 22.5 from the zCOSMOS-Bright redshift survey. We find that already at z=0.9 and all the way down to z=0.2, early-type galaxies exhibit a stronger clustering than late-type galaxies at any scale between 0.1 Mpc/h and 10 Mpc/h. The relative difference in clustering of the two classes of galaxies tends to increase with cosmic time, the most important effect occurring at separations below a few Mpc/h. The relative bias between early- and late-type galaxies is found to be scale-dependent at z<0.6, while no significant dependence is found at earlier epochs. This is simply understood in terms of non-linear evolution of clustering below z~0.6, involving the densest regions more likely to be populated by early-type galaxies. The observed shape evolution of the relative bias and its increase with cosmic time, suggest an environmental origin of the observed difference in clustering between spirals and ellipticals we observe nowadays, favouring a locally biased galaxy formation scenario. [16] arXiv:0911.2260 [pdf, other] Title: Testing adiabatic contraction with SDSS elliptical galaxies Authors: A.E. Schulz, Rachel Mandelbaum, Nikhil Padmanabhan Comments: 13 pages 9 figures for submission to MNRAS Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA) We study the profiles of 75 086 elliptical galaxies from the Sloan Digital Sky Survey (SDSS) at both large (50-500 kpc/h) and small (~3 kpc/h) scales. Weak lensing observations in the outskirts of the halo are combined with measurements of the stellar velocity dispersion in the interior regions of the galaxy for stacked galaxy samples. The weak lensing measurements are well characterized by a Navarro, Frenk and White (NFW) profile. The dynamical mass measurements exceed the extrapolated NFW profile even after the estimated stellar masses are subtracted, providing evidence for the modification of the dark matter profile by the baryons. This excess mass is quantitatively consistent with the predictions of the adiabatic contraction (AC) hypothesis. Our finding suggests that the effects of AC during galaxy formation are stable to subsequent bombardment from major and minor mergers. We explore several theoretical and observational systematics and conclude that they cannot account for the inferred mass excess. The most significant source of systematic error is in the IMF, which would have to increase the stellar mass estimates by a factor of two relative to masses from the Kroupa IMF to fully explain the mass excess without AC. Such an increase would create tension with results from SAURON (Cappellari et al. 2006). We demonstrate a connection between the level of contraction of the dark matter halo profile and scatter in the size-luminosity relation, which is a projection of the fundamental plane. Whether or not AC is the mechanism supplying the excess mass, models of galaxy formation and evolution must reconcile the observed halo masses from weak lensing with the comparatively large dynamical masses at the half light radii of the galaxies. [22] arXiv:0911.2316 [ps, pdf, other] Title: Dark matter response to galaxy formation Authors: Patricia B. Tissera (1,2), Simon D. M. White (3), Susana Pedrosa (1,2), Cecilia Scannapieco (4) ((1) Consejo Nacional de Investigaciones Cientificas y Tecnicas, CONICET, Argentina (2) Instituto de Astronomia y Fisica del Espacio, Argentina (3) Max-Planck Institute for Astrophysics, Germany (4) Astrophysikalisches Institut Potsdam, Germany) Comments: 14 pages, 9 figures. Submitted to MNRAS Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA) We have resimulated the six galaxy-sized haloes of the Aquarius Project including metal-dependent cooling, star formation and supernova feedback. This allows us to study not only how dark matter haloes respond to galaxy formation, but also how this response is affected by details of halo assembly history. In agreement with previous work, we find baryon condensation to lead to increased dark matter concentration. Dark matter density profiles differ substantially in shape from halo to halo when baryons are included, but in all cases the velocity dispersion decreases monotonically with radius. Some haloes show an approximately constant dark matter velocity anisotropy with $ \beta \approx 0.1-02$, while others retain the anisotropy structure of their baryon-free versions. Most of our haloes become approximately oblate in their inner regions, although a few retain the shape of their dissipationless counterparts. Pseudo-phase-space densities are described by a power law in radius of altered slope when baryons are included. The shape and concentration of the dark matter density profiles are not well reproduced by published adiabatic contraction models. The significant spread we find in the density and kinematic structure of our haloes appears related to differences in their formation histories. Such differences already affect the final structure in baryon-free simulations, but they are reinforced by the inclusion of baryons, and new features are produced. The details of galaxy formation need to be better understood before the inner dark matter structure of galaxies can be used to constrain cosmological models or the nature of dark matter. [46] arXiv:0911.2456 [ps, pdf, other] Title: Identifying Anomalies in Gravitational Lens Time Delays Authors: Arthur B. Congdon, Charles R. Keeton, C. Erik Nordgren Comments: 24 pages, 10 figures, 5 tables, accepted by ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We examine the ability of gravitational lens time delays to reveal complex structure in lens potentials. In Congdon, Keeton & Nordgren (2008), we predicted how the time delay between the bright pair of images in a "fold" lens scales with the image separation, for smooth lens potentials. Here we show that the proportionality constant increases with the quadrupole moment of the lens potential, and depends only weakly on the position of the source along the caustic. We use Monte Carlo simulations to determine the range of time delays that can be produced by realistic smooth lens models consisting of isothermal ellipsoid galaxies with tidal shear. We can then identify outliers as "time delay anomalies". We find evidence for anomalies in close image pairs in the cusp lenses RX J1131$-$1231 and B1422+231. The anomalies in RX J1131$-$1231 provide strong evidence for substructure in the lens potential, while at this point the apparent anomalies in B1422+231 mainly indicate that the time delay measurements need to be improved. We also find evidence for time delay anomalies in larger-separation image pairs in the fold lenses, B1608+656 and WFI 2033$-$4723, and the cusp lens RX J0911+0551. We suggest that these anomalies are caused by some combination of substructure and a complex lens environment. Finally, to assist future monitoring campaigns we use our smooth models with shear to predict the time delays for all known four-image lenses.