arXiv:0808.2129 [ps, pdf, other] Title: Is there a redshift cutoff for submillimetre galaxies? Authors: G. Raymond, S. A. Eales, S. Dye, R. Carlberg, M. Sullivan Comments: 9 pages, 4 figures, submitted to MNRAS Subjects: Astrophysics (astro-ph) We present new optical and infrared photometry for a statistically complete sample of seven 1.1 mm selected sources with accurate Submillimetre Array coordinates. We determine photometric redshifts for four of the seven sources of 4.47, 4.50, 1.49 and 0.64. Of the other three sources two are undetected at optical wavelengths down to the limits of very deep Subaru and Canada-France-Hawaii Telescope images ($\sim$27 mag AB, i band) and the photometry of the remaining source is corrupted by a bright nearby galaxy. The sources with the highest redshifts are at higher redshifts than all but one of the $\sim$200 sources taken from the largest recent 850 $\mu$m surveys, which may indicate that 1.1 mm surveys are more efficient at finding sources at very high redshifts than 850 $\mu$m surveys. We investigate the evolution of the number density with redshift of our sample using a banded $V_{e}/V_{a}$ analysis and find no evidence for a redshift cutoff, although the number of sources is very small. We also perform the same analysis on a statistically complete sample of 38 galaxies selected at 850$\mu$m from the GOODS-N field and find evidence for a drop-off in the number density beyond $z\sim1$ and 2 for hot and cold dust dominated SMGs respectively, confirming the earlier conclusion of Wall, Pope & Scott. We also find strong evidence for the existence of two differently evolving sub-populations separated in luminosity, with a higher relative density of the high luminosity galaxies at higher redshifts. [good north smb reference] arXiv:0808.2391 [ps, pdf, other] Title: Star formation rates in Lyman break galaxies: radio stacking of LBGs in the COSMOS field and the sub-$\mu$Jy radio source population Authors: C.L. Carilli (NRAO), Nicholas Lee (NRAO), P. Capak (CIT), E. Schinnerer (MPIA), K.-S. Lee (Yale), H. McCraken (IAP), M.S. Yun (UMass), N. Scoville (CIT), V. Smolcic (CIT), M. Giavalisco (UMass), A. Datta (NRAO), Y. Taniguchi (Ehime Univ) C. Megan Urry (Yale) Comments: 15 pages, 2 figures AASTEX, to appear in ApJ Subjects: Astrophysics (astro-ph) We present an analysis of the radio properties of large samples of Lyman Break Galaxies (LBGs) at $z \sim 3$, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the $z \sim 3$ LBGs (U-band drop-outs), with a 1.4 GHz flux density of $0.90 \pm 0.21 \mu$Jy. The stacked emission is unresolved, with a size $< 1"$, or a physical size $< 8$kpc. The total star formation rate implied by this radio luminosity is $31\pm 7$ $M_\odot$ year$^{-1}$, based on the radio-FIR correlation in low redshift star forming galaxies. The star formation rate derived from a similar analysis of the UV luminosities is 17 $M_\odot$ year$^{-1}$, without any correction for UV dust attenuation. The simplest conclusion is that the dust attenuation factor is 1.8 at UV wavelengths. However, this factor is considerably smaller than the standard attenuation factor $\sim 5$, normally assumed for LBGs. We discuss potential reasons for this discrepancy, including the possibility that the dust attenuation factor at $z \ge 3$ is smaller than at lower redshifts. Conversely, the radio luminosity for a given star formation rate may be systematically lower at very high redshift. Two possible causes for a suppressed radio luminosity are: (i) increased inverse Compton cooling of the relativistic electron population due to scattering off the increasing CMB at high redshift, or (ii) cosmic ray diffusion from systematically smaller galaxies. The radio detections of individual sources are consistent with a radio-loud AGN fraction of 0.3%. One source is identified as a very dusty, extreme starburst galaxy (a 'submm galaxy'). arXiv:0808.2493 [ps, pdf, other] Title: Galaxy density profiles and shapes -- I. simulation pipeline for lensing by realistic galaxy models Authors: Glenn van de Ven (IAS, Princeton), Rachel Mandelbaum (IAS, Princeton), Charles R. Keeton (Rutgers Univ.) Comments: 31 pages, 15 figures; paper II at arXiv:0808.2497; submitted for publication in MNRAS; PDF file with full resolution figures at this http URL Subjects: Astrophysics (astro-ph) Studies of strong gravitational lensing in current and upcoming wide and deep photometric surveys, and of stellar kinematics from (integral-field) spectroscopy at increasing redshifts, promise to provide valuable constraints on galaxy density profiles and shapes, but only if we understand selection and modelling biases that affect both methods. To investigate the many different biases in a consistent way, we develop a flexible but efficient pipeline to simulate lensing by realistic galaxy models. We construct a variety of galaxy models with separate stellar and dark matter components that have a range of density profiles and shapes representative of early-type, central (non-satellite) galaxies. We use Fourier methods to calculate the lensing properties of galaxies with arbitrary surface density distributions, and Monte Carlo methods to compute lensing statistics such as point-source lensing cross-sections. Incorporating a variety of magnification bias modes lets us examine different survey strategies. We rigorously test the numerical methods for systematic errors and sensitivity to basic assumptions. We also determine the minimum number of viewing angles that must be sampled in order to recover accurate orientation-averaged lensing quantities. We find that for a range of non-isothermal stellar and dark matter density profiles typical of elliptical galaxies, the combined density profile and corresponding lensing properties are surprisingly close to isothermal around the Einstein radius. The converse implication is that constraints from strong lensing and/or stellar kinematics, which are indeed consistent with isothermal models near the Einstein radius, cannot trivially be extrapolated to smaller and larger radii. arXiv:0808.2497 [ps, pdf, other] Title: Galaxy density profiles and shapes -- II. selection biases in strong lensing surveys Authors: Rachel Mandelbaum (IAS, Princeton), Glenn van de Ven (IAS, Princeton), Charles R. Keeton (Rutgers Univ.) Comments: 25 pages, 16 figures; paper I at arXiv:0808.2493; submitted for publication in MNRAS; PDF file with full resolution figures at this http URL Subjects: Astrophysics (astro-ph) [Abridged] Many current and future astronomical surveys will rely on samples of strong gravitational lens systems to draw conclusions about galaxy mass distributions. We use a new strong lensing pipeline (presented in Paper I of this series) to explore selection biases that may cause the population of strong lensing systems to differ from the general galaxy population. Our focus is on point-source lensing by early-type galaxies with two mass components (stellar and dark matter) that have a variety of density profiles and shapes motivated by observational and theoretical studies of galaxy properties. We seek not only to quantify but also to understand the physics behind selection biases related to: galaxy mass, orientation and shape; dark matter profile parameters such as inner slope and concentration; and adiabatic contraction. We study how all of these properties affect the lensing Einstein radius, total cross-section, quad/double ratio, and image separation distribution. We find significant (factors of several) selection biases with mass; orientation, for a given galaxy shape at fixed mass; cusped dark matter profile inner slope and concentration; concentration of the stellar and dark matter deprojected Sersic models. Interestingly, the intrinsic shape of a galaxy does not strongly influence its lensing cross-section when we average over viewing angles. Our results will enable users of lensing surveys to understand how their strong lens systems relate to the general galaxy population, and thus to obtain meaningful constraints on galaxy properties. arXiv:0808.2526 [ps, pdf, other] Title: The subhalo - satellite connection and the fate of disrupted satellite galaxies Authors: Xiaohu Yang (SHAO), H.J. Mo (UMass), Frank C. van den Bosch (MPIA) Comments: 9 pages, 7 figures. Submitted for publication in ApJ Subjects: Astrophysics (astro-ph) In the standard paradigm, satellite galaxies are believed to be associated with the population of dark matter subhalos. In this paper, we use the conditional stellar mass functions of {\it satellite galaxies} obtained from a large galaxy group catalogue together with models of the subhalo mass functions to explore the fraction and fate of stripped stars from satellites in galaxy groups and clusters of different masses. The majority of the stripped stars in massive halos are predicted to end up as intra-cluster stars, and the predicted amounts of the intra-cluster component as a function of the velocity dispersion of galaxy system match well the observational results obtained by Gonzalez et al. (2007). The fraction of the mass in the stripped stars to that remain bound in the central and satellite galaxies is the highest ($\sim 40%$ of the total stellar mass) in halos with masses $M_h\sim 10^{14}\msunh$. If all these stars end up in the intra-cluster component (Max), or maximum of them are accreted into the central galaxy (Min), then we can predict that a maximum $\sim 19%$ and a minimum $\sim 5%$ of the total stars in the whole universe are in terms of the diffused intra-cluster component. In the former case, in massive halos with $M_h \sim 10^{15} \msunh$, the stellar mass of the intra-cluster component is roughly 6 times as large as that of the central galaxy. This factor decreases to $\sim 2$, 1 and 0.1 in halos with $M_h \sim 10^{14}$, $10^{13}$, and $10^{12} \msunh$, respectively. The total amount of stars stripped from satellite galaxies is insufficient to build up the central galaxies in halos with masses $\la 10^{12.5}\msunh$, and so the quenching of star formation must occur in halos with higher masses. Abridged. arXiv:0808.2642 [ps, pdf, other] Title: Structure and star formation in galaxies out to z=3: evidence for surface density dependent evolution and upsizing Authors: Marijn Franx, Pieter G. van Dokkum, Natascha M. Foerster Schreiber, Stijn Wuyts, Ivo Labbe, Sune Toft Comments: 20 pages, accepted for publication in ApJ, 2008, 689 Subjects: Astrophysics (astro-ph) We present an analysis of galaxies in the CDF-South. We find a tight relation to z=3 between color and size at a given mass, with red galaxies being small, and blue galaxies being large. We show that the relation is driven by stellar surface density or inferred velocity dispersion: galaxies with high surface density are red and have low specific star formation rates, and galaxies with low surface density are blue and have high specific star formation rates. Surface density and inferred velocity dispersion are better correlated with specific star formation rate and color than stellar mass. Hence stellar mass by itself is not a good predictor of the star formation history of galaxies. In general, galaxies at a given surface density have higher specific star formation rates at higher redshift. Specifically, galaxies with a surface density of 1-3 10^9 Msun/kpc^2 are "red and dead" at low redshift, approximately 50% are forming stars at z=1, and almost all are forming stars by z=2. This provides direct additional evidence for the late evolution of galaxies onto the red sequence. The sizes of galaxies at a given mass evolve like 1/(1+z)^(0.59 +- 0.10). Hence galaxies undergo significant upsizing in their history. The size evolution is fastest for the highest mass galaxies, and quiescent galaxies. The persistence of the structural relations from z=0 to z=2.5, and the upsizing of galaxies imply that a relation analogous to the Hubble sequence exists out to z=2.5, and possibly beyond. The star forming galaxies at z >= 1.5 are quite different from star forming galaxies at z=0, as they have likely very high gas fractions, and star formation time scales comparable to the orbital time. arXiv:0808.2645 [ps, pdf, other] Title: DLA kinematics and outflows from starburst galaxies Authors: Alexei O. Razoumov (Saint Mary's University, Halifax) Comments: ApJ submitted, 10 figures, printing in colour recommended, comments welcome Subjects: Astrophysics (astro-ph) We present results from a numerical study of the multiphase interstellar medium in sub-Lyman-break galaxy protogalactic clumps. Such clumps are abundant at z=3 and are thought to be a major contributor to damped Ly-alpha absorption. We model the formation of winds from these clumps and show that during star formation episodes they feature outflows with neutral gas velocity widths up to several hundred km/s. Such outflows are consistent with the observed high-velocity dispersion in DLAs. In our models thermal energy feedback from winds and supernovae results in efficient outflows only when cold (~ 300 K), dense (> 100 msun/pc^3) clouds are resolved at grid resolution of 12 pc. At lower 24 pc resolution the first signs of the multiphase medium are spotted; however, at this low resolution thermal injection of feedback energy cannot yet create hot expanding bubbles around star-forming regions -- instead feedback tends to erase high-density peaks and suppress star formation. At 12 pc resolution feedback compresses cold clouds, often without disrupting the ongoing star formation; at the same time a larger fraction of feedback energy is channeled into low-density bubbles and winds. These winds often entrain compact neutral clumps which produce multi-component metal absorption lines. arXiv:0808.2746 [ps, pdf, other] Title: Relation Between Stellar Mass and Star Formation Activity in Galaxies Authors: Bahram Mobasher (1), T. Dahlen (2), A. Hopkins (3), N. Z. Scoville (4), P. Capak (5), R. M. Rich (6), D. B. Sanders (7), Eva Schinnerer (8), Olivier Ilbert (7), Mara Salvato (4), Kartik Sheth (5) ((1)University of California, Riverside; (2)STScI; (3)University of Sydney; (4)Caltech; (5)Spitzer Science Center; (6)University of California, Los Angles; (7)University of Hawaii; (8)Max Planck Institute for Astronomy, Heidelberg) Comments: 34 pages; 8 figures; Accepted for publication in ApJ Subjects: Astrophysics (astro-ph) For a mass-selected sample of 66544 galaxies with photometric redshifts from the Cosmic Evolution Survey (COSMOS), we examine the evolution of star formation activity as a function of stellar mass in galaxies. We estimate the cosmic star formation rates (SFR) over the range 0.2 < z < 1.2, using the rest-frame 2800 A flux (corrected for extinction). We find the mean SFR to be a strong function of the galactic stellar mass at any given redshift, with massive systems (log (M/M(Sun)) > 10.5) contributing less (by a factor of ~ 5) to the total star formation rate density (SFRD). Combining data from the COSMOS and Gemini Deep Deep Survey (GDDS), we extend the SFRD-z relation as a function of stellar mass to z~2. For massive galaxies, we find a steep increase in the SFRD-z relation to z~2; for the less massive systems, the SFRD which also increases from z=0 to 1, levels off at z~1. This implies that the massive systems have had their major star formation activity at earlier epochs (z > 2) than the lower mass galaxies. We study changes in the SFRDs as a function of both redshift and stellar mass for galaxies of different spectral types. We find that the slope of the SFRD-z relation for different spectral type of galaxies is a strong function of their stellar mass. For low and intermediate mass systems, the main contribution to the cosmic SFRD comes from the star-forming galaxies while, for more massive systems, the evolved galaxies are the most dominant population. arXiv:0808.2824 [ps, pdf, other] Title: HAWK-I imaging of the X-ray luminous galaxy cluster XMMU J2235.3-2557: The red sequence at z=1.39 Authors: C. Lidman, P. Rosati, M. Tanaka, V. Strazzullo, R. Demarco, C. Mullis, N. Ageorges, M. Kissler-Patig, M. G. Petr-Gotzens, F. Selman Comments: 9 pages, 2 figures. To appear in A&A Subjects: Astrophysics (astro-ph) We use HAWK-I, the recently-commissioned near-IR imager on Yepun (VLT-UT4), to obtain wide-field, high-resolution images of the X-ray luminous galaxy cluster XMMU J2235.3-2557 in the J and Ks bands, and we use these images to build a colour-magnitude diagram of cluster galaxies. Galaxies in the core of the cluster form a tight red sequence with a mean J-Ks colour of 1.9 (Vega system). The intrinsic scatter in the colour of galaxies that lie on the red sequence is similar to that measured for galaxies on the red sequence of the Coma cluster. The slope and location of the red sequence can be modelled by passively evolving the red sequence of the Coma cluster backwards in time. Using simple stellar population (SSP) models, we find that galaxies in the core of XMMU J2235.3-2557 are, even at z=1.39, already 3 Gyr old, corresponding to a formation redshift of z ~ 4. Outside the core, the intrinsic scatter and the fraction of galaxies actively forming stars increase substantially. Using SSP models, we find that most of these galaxies will join the red sequence within 1.5 Gyr. The contrast between galaxies in the cluster core and galaxies in the cluster outskirts indicates that the red sequence of XMMU J2235.3-2557 is being built from the dense cluster core outwards.