[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. arXiv:0910.5720 [ps, pdf, other] Title: The Bimodal Galaxy Stellar Mass Function in the COSMOS Survey to z~1: A Steep Faint End and a New Galaxy Dichotomy Authors: N. Drory (1), K. Bundy (2), A. Leauthaud (3,4), N. Scoville (5), P. Capak (5,6), O. Ilbert (7), J.S. Kartaltepe (8), J.P. Kneib (7), H.J. McCracken (9), M. Salvato (5,10), D.B. Sanders (11), D. Thompson (12), C.J. Willott (13) ((1) MPE, (2) Berkeley, (3) LBNL, (4) BCCP, (5) Caltech, (6) Spitzer Science Center, (7) Marseille, (8) NOAO, (9) Paris, (10) IPP, (11) Hawaii, (12) LBT Observatory, (13) Herzberg) Comments: 16 pages, 10 figures, accepted for publication in ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We present a new analysis of stellar mass functions (MF) in the COSMOS field to fainter limits than has been previously probed to z~1. Neither the total nor the passive or star-forming MF can be well fit with a single Schechter function once one probes below 3e9 Msun. We observe a dip or plateau at masses ~1e10 Msun, and an upturn towards a steep faint-end slope of -1.7 at lower mass at any z<1. This bimodal nature of the MF is not solely a result of the blue/red dichotomy. The blue MF is by itself bimodal at z~1. This suggests a new dichotomy in galaxy formation that predates the appearance of the red sequence. We propose two interpretations for this bimodality. If the gas fraction increases towards lower mass, galaxies with M_baryon~1e10 Msun would shift to lower stellar masses, creating the observed dip. This would indicate a change in star formation efficiency, perhaps linked to supernovae feedback becoming much more efficient. Therefore, we investigate whether the dip is present in the baryonic (stars+gas) MF. Alternatively, the dip could be created by an enhancement of the galaxy assembly rate at ~1e11 Msun, a phenomenon that naturally arises if the baryon fraction peaks at M_halo ~1e12 Msun. In this scenario, galaxies occupying the bump around M* would be identified with central galaxies and the second fainter component having a steep faint-end slope with satellites. While the dip is apparent in the total MF at any z, it appears to shift from the blue to red population, likely as a result of transforming high-mass blue galaxies into red ones. At the same time, we detect a drastic upturn in the number of low-mass red galaxies. Their increase with time reflects a decrease in the number of blue systems and so we tentatively associate them with satellite dwarf galaxies that have undergone quenching. arXiv:0910.5824 [ps, pdf, other] Title: The optical spectra of Spitzer 24 micron galaxies in the COSMOS field: II. Faint infrared sources in the zCOSMOS-bright 10k catalogue Authors: K. I. Caputi, S. J. Lilly, H. Aussel, E. Le Floc'h, D. Sanders, C. Maier, D. Frayer, C. M. Carollo, T. Contini, J.-P. Kneib, O. Le Fevre, V. Mainieri, A. Renzini, M. Scodeggio, N. Scoville, G. Zamorani, S. Bardelli, M. Bolzonella, A. Bongiorno, G. Coppa, O. Cucciati, S. de la Torre, L. de Ravel, P. Franzetti, B. Garilli, O. Ilbert, A. Iovino, P. Kampczyk, J. Kartaltepe, C. Knobel, K. Kovac, F. Lamareille, J.-F. Le Borgne, V. Le Brun, M. Mignoli, Y. Peng, E. Perez-Montero, E. Ricciardelli, M. Salvato, J. Silverman, J. Surace, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, E. Zucca, U. Abbas, D. Bottini, P. Capak, A. Cappi, P. Cassata, A. Cimatti, M. Elvis, G. Hasinger, A. M. Koekemoer, A. Leauthaud, D. Maccagni, C. Marinoni, H. McCracken, P. Memeo, B. Meneux, P. Oesch, R. Pello, C. Porciani, et al. (6 additional authors not shown) Comments: 25 pages, 16 figures. Accepted for publication in the ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We have used the zCOSMOS-bright 10k sample to identify 3244 Spitzer/MIPS 24-micron-selected galaxies with 0.06< S(24um)< 0.50 mJy and I(AB)<22.5, over 1.5 deg^2 of the COSMOS field, and studied different spectral properties, depending on redshift. At 0.21000 and R-K>4.5. Of these, 18 were detected in X-rays and found to be obscured AGN with neutral hydrogen column densities of ~10^23 cm^-2. In the X-ray undetected sample, the following evidence suggests a large fraction of heavily-obscured (Compton Thick) AGN: (i) The stacked X-ray signal of the sample is strong, with an observed ratio of soft to hard X-ray counts consistent with a population of ~90% heavily obscured AGN combined with 10% star-forming galaxies. (ii) The X-ray to mid-IR ratios for these sources are significantly larger than that of star-forming galaxies and ~2 orders of magnitude smaller than for the general AGN population, suggesting column densities of N_H>5x10^24 cm^-2. (iii) The Spitzer near- and mid-IR colors of these sources are consistent with those of the X-ray-detected sample if the effects of dust self-absorption are considered. Spectral fitting to the rest-frame UV/optical light (dominated by the host galaxy) returns stellar masses of ~10^11 M_sun and =0.5, and reveals evidence for a significant young stellar population, indicating that these sources are experiencing considerable star-formation. This sample of heavily-obscured AGN candidates implies a space density at z~2 of ~10^-5 Mpc^-3, finding a strong evolution in the number of L_X>10^44 erg/s sources from z=1.5 to 2.5, possibly consistent with a short-lived heavily-obscured phase before an unobscured quasar is visible. arXiv:0911.0005 [ps, pdf, other] Title: Observational constraints on the co-evolution of supermassive black holes and galaxies Authors: X. Z. Zheng (1), E. F. Bell (2,3), R. S. Somerville (2,4), H.-W. Rix (2), K. Jahnke (2), F. Fontanot (2,5), G. H. Rieke (6), D. Schiminovich (7), K. Meisenheimer (2) ((1) Purple Mountain Observatory, (2) Max-Planck Institue for Astronomy, (3) University of Michigan, (4) Space Telescope Science Institute, (5) INAF-Osservatorio Astronomico, (6) Steward Observatory, (7) Columbia University) Comments: 14 pages, 5 figures, accepted for publication in ApJ Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) The star formation rate (SFR) and black hole accretion rate (BHAR) functions are measured to be proportional to each other at z < ~3. This close correspondence between SF and BHA would naturally yield a BH mass-galaxy mass correlation, whereas a BH mass-bulge mass correlation is observed. To explore this apparent contradiction we study the SF in spheroid-dominated galaxies between z=1 and the present day. We use 903 galaxies from the COMBO-17 survey with M* >2x10^10M_sun, ultraviolet and infrared-derived SFRs from Spitzer and GALEX, and morphologies from GEMS HST/ACS imaging. Using stacking techniques, we find that <25% of all SF occurs in spheroid-dominated galaxies (Sersic index n>2.5), while the BHAR that we would expect if the global scalings held is three times higher. This rules out the simplest picture of co-evolution, in which SF and BHA trace each other at all times. These results could be explained if SF and BHA occur in the same events, but offset in time, for example at different stages of a merger event. However, one would then expect to see the corresponding star formation activity in early-stage mergers, in conflict with observations. We conclude that the major episodes of SF and BHA occur in different events, with the bulk of SF happening in isolated disks and most BHA occurring in major mergers. The apparent global co-evolution results from the regulation of the BH growth by the potential well of the galactic spheroid, which includes a major contribution from disrupted disk stars. arXiv:0911.0014 [ps, pdf, other] Title: Searching for Evidence of Energetic Feedback in Distant Galaxies: A Galaxy Wide Outflow in a z~2 Ultraluminous Infrared Galaxy Authors: D.M. Alexander (Durham), A.M. Swinbank, I. Smail, R. McDermid, N. Nesvadba Comments: 10 pages, 5 figures, 1 table. Resubmitted to MNRAS after taking account of referees feedback Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE) Leading models of galaxy formation require large-scale energetic outflows to regulate the growth of distant galaxies and their central black holes. However, current observational support for this hypothesis at high redshift is mostly limited to rare z>2 radio galaxies. Here we present Gemini-North NIFS Intregral Field Unit (IFU) observations of the [OIII] emission from a z~2 ultraluminous infrared galaxy (L_IR>10^12 solar luminosities) with an optically identified Active Galactic Nucleus (AGN). The spatial extent (~4-8 kpc) of the high velocity and broad [OIII] emission are consistent with that found in z>2 radio galaxies, indicating the presence of a large-scale energetic outflow in a galaxy population potentially orders of magnitude more common than distant radio galaxies. The low radio luminosity of this system indicates that radio-bright jets are unlikely to be responsible for driving the outflow. However, the estimated energy input required to produce the large-scale outflow signatures (of order ~10^59 ergs over ~30 Myrs) could be delivered by a wind radiatively driven by the AGN and/or supernovae winds from intense star formation. The energy injection required to drive the outflow is comparable to the estimated binding energy of the galaxy spheroid, suggesting that it can have a significant impact on the evolution of the galaxy. We argue that the outflow observed in this system is likely to be comparatively typical of the high-redshift ULIRG population and discuss the implications of these observations for galaxy formation models. arXiv:0911.0417 [ps, pdf, other] Title: Evolution of the Halpha luminosity function Authors: Eduard Westra (1), Margaret J. Geller (1), Michael J. Kurtz (1), Daniel G. Fabricant (1), Ian Dell'Antonio (2) ((1) Smithsonian Astrophysical Observatory, (2) Brown University) Comments: 26 pages, 23 figures, submitted to ApJ; version with high resolution figures available at this http URL Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) The Smithsonian Hectospec Lensing Survey (SHELS) is a window on the star formation history over the last 4 Gyr. SHELS is a spectroscopically complete survey for Rtot < 20.3 over 4 square degrees. We use the 10k spectra to select a sample of pure star forming galaxies based on their Halpha emission line. We use the spectroscopy to determine extinction corrections for individual galaxies and to remove active galaxies in order to reduce systematic uncertainties. We use the large volume of SHELS with the depth of a narrowband survey for Halpha galaxies at z ~ 0.24 to make a combined determination of the Halpha luminosity function at z ~ 0.24. The large area covered by SHELS yields a survey volume big enough to determine the bright end of the Halpha luminosity function from redshift 0.100 to 0.377 for an assumed fixed faint-end slope alpha = -1.20. The bright end evolves: the characteristic luminosity L* increases by 0.84 dex over this redshift range. Similarly, the star formation density increases by 0.11 dex. The fraction of galaxies with a close neighbor increases by a factor of 2-5 for L(Halpha) >~ L* in each of the redshift bins. We conclude that triggered star formation is an important influence for star forming galaxies with Halpha emission. arXiv:0911.0420 [ps, pdf, other] Title: The globular cluster system of NGC 1399 V. dynamics of the cluster system out to 80 kpc Authors: Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. P. Bassino, A. J. Romanowsky, L. Infante Comments: 31 pages, accepted for publication in A&A. Online material will be available from the CDS Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA) (Abridged) We use the largest set of globular cluster velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. Our sample now comprises velocities for almost 700 GCs with projected galactocentric radii between 6 and 100 kpc. In addition, we use velocities published by Bergond et al. (2007). We study the kinematics of the metal-poor and metal-rich subpopulations and perform spherical Jeans modelling. The most important results are: The metal-rich (red) GCs resemble the stellar field population of NGC 1399 in the region of overlap. Both subpopulations are kinematically distinct and do not show a smooth transition. It is not possible to find a common dark halo which reproduces simultaneously the properties of both subpopulations. Some velocities of blue GCs are only to be explained by orbits with very large apogalactic distances, thus indicating a contamination with GCs which belong to the entire Fornax cluster rather than to NGC 1399. Stripped GCs from nearby elliptical galaxies, particularly NGC 1404, may also contaminate the metal-poor sample. We argue in favour of a scenario in which the majority of the blue cluster population has been accreted during the assembly of the Fornax cluster. The red cluster population shares the dynamical history of the galaxy itself. Therefore we recommend to use a dark halo based on the red GCs alone. The dark halo which fits best is marginally less massive than the halo quoted by Richtler et al. (2004). The comparison with X-ray analyses is satisfactory in the inner regions, but without showing evidence for a transition from a galaxy to a cluster halo, as suggested by X-ray work. arXiv:0911.0523 [ps, pdf, other] Title: Properties and environment of Radio Emitting Galaxies in the VLA-zCOSMOS survey Authors: S.Bardelli, E.Schinnerer, V.Smolcic, G.Zamorani, E.Zucca, M.Mignoli, C.Halliday, K.Kovac, P.Ciliegi, K.Caputi, A.M.Koekemoer, A.Bongiorno, M.Bondi, M.Bolzonella, D.Vergani, L.Pozzetti, C.M.Carollo, T.Contini, J.-P.Kneib, O.LeFevre, S.Lilly, V.Mainieri, A.Renzini, M.Scodeggio, G.Coppa, O.Cucciati, S.delaTorre, L.deRavel, P.Franzetti, B.Garilli, A.Iovino, P.Kampczyk, C.Knobel, F.Lamareille, J.-F.LeBorgne, V.LeBrun, C.Maier, R.Pello`, Y.Peng, E.Perez-Montero, E.Ricciardelli, J.D.Silverman, M.Tanaka, L.Tasca, L.Tresse, U.Abbas, D.Bottini, A.Cappi, P.Cassata, A.Cimatti, L.Guzzo, A.Leauthaud, D.Maccagni, C.Marinoni, H.J.McCracken, P.Memeo, B.Meneux, P.Oesch, C.Porciani, R.Scaramella, P.Capak, D.Sanders, N.Scoville, Y.Taniguchi, K.Jahnke Comments: 17 pages, 17 figures, A&A in press Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO) We investigate the properties and the environment of radio sources with optical counterpart from the combined VLA-COSMOS and zCOSMOS samples. The advantage of this sample is the availability of optical spectroscopic information, high quality redshifts, and accurate density determination. By comparing the star formation rates estimated from the optical spectral energy distribution with those based on the radio luminosity, we divide the radio sources in three families, passive AGN, non-passive AGN and star forming galaxies. These families occupy specific regions of the 8.0-4.5 $\mu$m infrared color--specific star formation plane, from which we extract the corresponding control samples. Only the passive AGN have a significantly different environment distribution from their control sample. The fraction of radio-loud passive AGN increases from ~2% in underdense regions to ~15% for overdensities (1+delta) greater than 10. This trend is also present as a function of richness of the groups hosting the radio sources. Passive AGN in overdensities tend to have higher radio luminosities than those in lower density environments. Since the black hole mass distribution is similar in both environments, we speculate that, for low radio luminosities, the radio emission is controlled (through fuel disponibility or confinement of radio jet by local gas pressure) by the interstellar medium of the host galaxy, while in other cases it is determined by the structure (group or cluster) in which the galaxy resides.