arXiv:0801.2764 [ps, pdf, other] Title: Clarifying the Nature of the Brightest Submillimetre Sources via SMA Interferometry Authors: J. D. Younger, J. S. Dunlop, A. B. Peck, R. J. Ivison, A. D. Biggs, E. L. Chapin, D. L. Clements, S. Dye, T. R. Greve, D. H. Hughes, D. Iono, I. Smail, M. Krips, G. R. Petitpas, D. Wilner, A. M. Schael, C. D. Wilson Comments: submitted to MNRAS Subjects: Astrophysics (astro-ph) We present high-resolution interferometric imaging of LH850.02, the brightest 850- and 1200-um submillimetre (submm) galaxy in the Lockman Hole, at 890um with the Submillimetre Array (SMA). Our high-resolution submm imaging detects LH850.02 at >6-sigma as a single compact (size <1 arcsec or <8 kpc) point source and yields its absolute position to ~0.2-arcsec accuracy. LH850.02 has two alternative radio counterparts within the SCUBA beam (LH850.02N & S), both of which are statistically very unlikely to be so close to the SCUBA source position by chance. However, the precise astrometry from the SMA shows that the submm emission arises entirely from LH850.02N, and is not associated with LH850.02S (by far the brighter of the two alternative identifications at 24-um). Fits to the optical-infrared multi-colour photometry of LH850.02N & S indicate that both lie at z~3.3, and are therefore likely to be physically associated. At these redshifts, the 24um-to-submm flux density ratios suggest that LH 850.02N has an Arp 220-type starburst-dominated far-IR SED, while LH 850.02S is more similar to Mrk 231, with less dust-enshrouded star-formation activity, but a significant contribution at 24-um (rest-frame ~5-6um) from an active nucleus. This complex mix of star-formation and AGN activity in multi-component sources may be common in the high redshift ultraluminous galaxy population, and highlights the need for precise astrometry from high resolution interferometric imaging for a more complete understanding. [2] arXiv:0801.2769 [ps, pdf, other] Title: The DEEP2 Galaxy Redshift Survey: The Red Sequence AGN Fraction and its Environment and Redshift Dependence Authors: Antonio D. Montero-Dorta, Darren J. Croton, Renbin Yan, Michael C. Cooper, Jeffery A. Newman, Antonis Georgakakis, Francisco Prada, Marc Davis, Kirpal Nandra, Alison Coil Comments: 11 pages, 7 figures, submitted to MNRAS Subjects: Astrophysics (astro-ph) We measure the dependence of the AGN fraction on local environment at z~1, using spectroscopic data taken from the DEEP2 Galaxy Redshift Survey, and Chandra X-ray data from the All-Wavelength Extended Groth Strip International Survey (AEGIS). To provide a clean sample of AGN we restrict our analysis to the red sequence population; this also reduces additional colour-environment correlations. We find evidence that high redshift LINERs in DEEP2 tend to favour higher density environments relative to the red population from which they are drawn. In contrast, Seyferts and X-ray selected AGN at z~1 show little (or no) environmental dependencies within the same underlying population. We compare these results with a sample of local AGN drawn from the SDSS. Contrary to the high redshift behaviour, we find that both LINERs and Seyferts in the SDSS show a slowly declining red sequence AGN fraction towards high density environments. Interestingly, at z~1 red sequence Seyferts and LINERs are approximately equally abundant. By z~0, however, the red Seyfert population has declined relative to the LINER population by over a factor of 7. We speculate on possible interpretations of our results. arXiv:0801.2770 [ps, pdf, other] Title: Simulating galactic outflows with kinetic supernova feedback Authors: Claudio Dalla Vecchia, Joop Schaye (Leiden Observatory) Comments: 14 pages, 7 figures, submitted to MNRAS. Simulations videos available at this http URL Subjects: Astrophysics (astro-ph) Feedback from star formation is thought to play a key role in the formation and evolution of galaxies, but its implementation in cosmological simulations is currently hampered by a lack of numerical resolution. We present and test a sub-grid recipe to model feedback from massive stars in cosmological smoothed particle hydrodynamics simulations. The energy is distributed in kinetic form among the gas particles surrounding recently formed stars. The impact of the feedback is studied using a suite of high-resolution simulations of isolated disc galaxies embedded in dark halos with total mass 10^{10} and 10^{12} M_sol/h. We focus in particular on the effect of pressure forces within the disc, which we turn off temporarily in some of our runs to mimic a recipe that has been widely used in the literature. We find that (ram) pressure forces on expanding superbubbles determine both the structure of the disc and the development of large-scale outflows. Pressure forces exerted by expanding superbubbles puff up the disc, giving the dwarf galaxy an irregular morphology and creating a galactic fountain in the massive galaxy. Hydrodynamic drag within the disc results in a strong increase of the effective mass loading of the wind for the dwarf galaxy, but quenches much of the outflow in the case of the high-mass galaxy. 8] arXiv:0801.2771 [ps, pdf, other] Title: Where do "red and dead" early-type void galaxies come from? Authors: Darren J. Croton, Glennys R. Farrar Comments: 6 pages, 3 figures, submitted to MNRAS Subjects: Astrophysics (astro-ph) Void regions of the Universe offer a special environment for studying cosmology and galaxy formation, which may expose weaknesses in our understanding of these phenomena. Although galaxies in voids are observed to be predominately gas rich, star forming and blue, a sub-population of bright red void galaxies can also be found, whose star formation was shut down long ago. Are the same processes that quench star formation in denser regions of the Universe also at work in voids? We compare the luminosity function of void galaxies in the 2dFGRS, to those from a galaxy formation model built on the Millennium Simulation. We show that a global star formation suppression mechanism in the form of low luminosity "radio mode" AGN heating is sufficient to reproduce the observed population of void early-types. Radio mode heating is environment independent other than its dependence on dark matter halo mass, where, above a critical mass threshold of approximately Mvir~10^12.5Msun, gas cooling onto the galaxy is suppressed and star formation subsequently fades. In the Millennium Simulation, the void halo mass function is shifted with respect to denser environments, but still maintains a high mass tail above this critical threshold. In such void halos, radio mode heating remains efficient and red galaxies are found; collectively these galaxies match the observed space density without any modification to the model. Consequently, galaxies living in vastly different large-scale environments but hosted by halos of similar mass are predicted to have similar properties, consistent with observations. arXiv:0801.2870 [ps, pdf, other] Title: Evolution of Gas in Galaxies Authors: Lister Staveley-Smith Comments: 5 pages, 2 figures. To appear in 'From Planets to Dark Energy: the Modern Radio Universe' (Manchester, October 2007), eds. R. Beswick et al., Proceedings of Science Subjects: Astrophysics (astro-ph) The SKA will be a unique instrument with which to study the evolution of the gas content of galaxies. A proposed deep (~8 Msec) 'pencil-beam' survey is simulated using recently updated specifications for SKA sensitivity and survey speed. Almost 10^7 galaxies could be detected in the redshifted 21cm line, most at redshifts in excess of two. This will enable confident statements to be made about the evolution of the cosmic HI density and the HI mass function to z=3, corresponding to a lookback time of 11 Gyr. However, galaxies or groups of galaxies with masses the same as the most HI-massive galaxies at z=0 will be detectable at redshifts of 6, if they exist. The ideal instrument for studying HI evolution would have an instantaneous sensitivity at least a factor of two higher than current specifications in the critical frequency range 200-500 MHz, or A/T > 2x10^4 m^2/K. The capabilities of the SKA will be highly complementary to ALMA which will be able to study the evolution of the molecular gas component over the same redshift range. arXiv:0801.2968 [ps, pdf, other] Title: Mapping the Cosmological Expansion Authors: Eric V. Linder Comments: 49 pages, 29 figures; Review invited for Reports on Progress in Physics Subjects: Astrophysics (astro-ph) The ability to map the cosmological expansion has developed enormously, spurred by the turning point one decade ago of the discovery of cosmic acceleration. The standard model of cosmology has shifted from a matter dominated, standard gravity, decelerating expansion to the present search for the origin of acceleration in the cosmic expansion. We present a wide ranging review of the tools, challenges, and physical interpretations. The tools include direct measures of cosmic scales through Type Ia supernova luminosity distances, and angular distance scales of baryon acoustic oscillation and cosmic microwave background density perturbations, as well as indirect probes such as the effect of cosmic expansion on the growth of matter density fluctuations. Accurate mapping of the expansion requires understanding of systematic uncertainties in both the measurements and the theoretical framework, but the result will give important clues to the nature of the physics behind accelerating expansion and to the fate of the universe. [3] arXiv:0801.2971 [ps, pdf, other] Title: H-alpha Kinematics of the SINGS Nearby Galaxies Survey. II Authors: I. Dicaire (1), C. Carignan (1), P. Amram (2), O. Hernandez (1), L. Chemin (3), O. Daigle (1, 2), M.-M. de Denus-Baillargeon (1, 4), C. Balkowski (3), A. Boselli (2), K. Fathi (5), R. C. Kennicutt (6) ((1) Université de Montréal, (2) LAM, (3) Observatoire de Paris-GEPI, (4) Institut Fresnel, (5) IAC, (6) IoA) Comments: 18 pages, 5 figures, 4 tables. Accepted for publication in MNRAS. All high-res. figures are available at this http URL Subjects: Astrophysics (astro-ph) This is the second part of an H-alpha kinematics follow-up survey of the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The aim of this program is to shed new light on the role of baryons and their kinematics and on the dark/luminous matter relation in the star forming regions of galaxies, in relation with studies at other wavelengths. The data for 37 galaxies are presented. The observations were made using Fabry-Perot interferometry with the photon-counting camera FaNTOmM on 4 different telescopes, namely the Canada-France-Hawaii 3.6m, the ESO La Silla 3.6m, the William Herschel 4.2m, and the Observatoire du mont Megantic 1.6m telescopes. The velocity fields are computed using custom IDL routines designed for an optimal use of the data. The kinematical parameters and rotation curves are derived using the GIPSY software. It is shown that non-circular motions associated with galactic bars affect the kinematical parameters fitting and the velocity gradient of the rotation curves. This leads to incorrect determinations of the baryonic and dark matter distributions in the mass models derived from those rotation curves. arXiv:0801.2975 [pdf, other] Title: A blind test of photometric redshifts on ground-based data Authors: H. Hildebrandt, C. Wolf, N. Benitez Comments: 14 pages, 9 figures, accepted by A&A Subjects: Astrophysics (astro-ph) Aims. We analyse the relative performance of different photo-z codes in blind applications to ground-based data. Methods. We tested the codes on imaging datasets with different depths and filter coverages and compared the results to large spectroscopic catalogues. The photo-z error behaviour was analysed to select cleaner subsamples with more secure photo-z estimates. We consider Hyperz, BPZ, and the code used in the CADIS, COMBO-17, and HIROCS surveys. Results. The photo-z error estimates of the three codes do not correlate tightly with the accuracy of the photo-z's. While very large errors sometimes indicate a true catastrophic photo-z failure, smaller errors are usually not meaningful. For any given dataset, we find significant differences in redshift accuracy and outlier rates between the different codes when compared to spectroscopic redshifts. However, different codes excel in different regimes. The agreement between different sets of photo-z's is better for the subsample with secure spectroscopic redshifts than for the whole catalogue. Conclusions. Running today's photo-z codes on well-calibrated ground-based data can lead to reasonable accuracy. The actual performance on a given dataset is largely dependent on the template choice and on realistic instrumental response curves. It would be desirable to improve the photo-z error estimation for future applications so as to get a better handle on rejecting objects with grossly inaccurate photo-z's. The secure spectroscopic subsamples commonly used for assessments of photo-z accuracy may be biased toward objects for which the photo-z's are easier to estimate than for a complete flux-limited sample, resulting in very optimistic estimates. (abridged) arXiv:0801.3273 [pdf, other] Title: Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-alpha, and Lyman-break Galaxies at z=3 Authors: Johan P. U. Fynbo (1), J. Xavier Prochaska (2), Jesper Sommer-Larsen (3,1), Miroslava Dessauges-Zavadsky (4), Palle Moller (5) ((1) Dark Cosmology Centre, NBI, Copenhagen, Denmark; (2) UCO/Lick Observatory, USA; (3) Excellence Cluster Universe, TUM, Munich, Germany; (4) Geneva Observatory, Switzerland; (5) European Southern Observatory, Garching, Germany) Comments: 19 pages, 6 figures. Submitted to ApJ. Comments very welcome Subjects: Astrophysics (astro-ph) We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-alpha (DLA) systems are drawn from the population of UV-selected star-forming, high-z galaxies (generally referred to as Lyman-break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations to simple models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star-formation rate and HI cross-section respectively. We find that it is possible to match both observational distributions assuming very simple and constrained relations between luminosity, metallicity and HI sizes. The simple model can be tested by observing the luminosity distribution of GRB host galaxies and by measuring the luminosity and impact parameters of DLA selected galaxies as a function of metallicity. Our results support the expectation that GRB and DLA samples, in contrast to magnitude limited surveys, provide an almost complete census of star-forming galaxies at z=3. arXiv:0801.3275 [pdf, other] Title: ZEBRA 1.0 -- User manual Authors: R. Feldmann Comments: 33 pages, 3 Figures, 7 Tables. ZEBRA is available at this http URL Subjects: Astrophysics (astro-ph) ZEBRA, the Zurich Extragalactic Bayesian Redshift Analyzer, is a tool for estimating redshifts and template types of galaxies using medium- and broad-band photometric data. ZEBRA employs novel techniques within the template-fitting approach to produce high-quality Maximum-Likelihood and Bayesian redshift estimates. This manuscript serves as a user guide to ZEBRA. It explains how to use ZEBRA, specifies input and output formats, and gives a short account of the available options. ZEBRA is a free and open-source software distributed under the GNU Public License 3 and available at this http URL . There are several upgrades being implemented in ZEBRA currently. An updated documentation will be provided at each new release. Any problems, comments and suggestions on the code and the manual should be sent via e-mail to zebra@phys.ethz.ch. arXiv:0801.3286 [ps, pdf, other] Title: The Intrinsic Properties of SDSS Galaxies Authors: Ariyeh H. Maller, Andreas A. Berlind, Michael R. Blanton, David W. Hogg Comments: 11 pages, 12 figures submitted to ApJ Subjects: Astrophysics (astro-ph) The observed properties of galaxies vary with inclination; for most applications we would rather have properties that are independent of inclination, intrinsic properties. One way to determine inclination corrections is to consider a large sample of galaxies, study how the observed properties of these galaxies depend on inclination and then remove this dependence to recover the intrinsic properties. We perform such an analysis for galaxies selected from the Sloan Digital Sky Survey which have been matched to galaxies from the Two-Micron All Sky Survey. We determine inclination corrections for these galaxies as a function of galaxy luminosity and Sersic index. In the g-band these corrections reach as as high as 1.2 mag and have a median value of 0.3 mag for all galaxies in our sample. We find that the corrections show little dependence on galaxy luminosity, except in the $u$ band, but are strongly dependent on galaxy Sersic index. We find that the ratio of red-to-blue galaxies changes from 1:1 to 1:2 when going from observed to intrinsic colors for galaxies in the range -22.75 < M_K < -17.75. We also discuss how survey completeness and photometric redshifts should be determined when taking into account that observed and intrinsic properties differ. Finally, we examine whether previous determinations of stellar mass give an intrinsic quantity or one that depends on galaxy inclination. arXiv:0801.3530 [ps, pdf, other] Title: Why are AGN found in High Mass Galaxies? Authors: Lan Wang, Guinevere Kauffmann Comments: 7 pages,7 figures, MNRAS submitted Subjects: Astrophysics (astro-ph) We use semi-analytic models implemented in the Millennium Simulation to analyze the merging histories of dark matter haloes and of the galaxies that reside in them. We assume that supermassive black holes only exist in galaxies that have experienced at least one major merger. Only a few percent of galaxies with stellar masses less than $M_* < 10^{10} M_{\odot}$ are predicted to have experienced a major merger and to contain a black hole. The fraction of galaxies with black holes increases very steeply at larger stellar masses. This agrees well with the observed strong mass dependence of the fraction of nearby galaxies that contain either low-luminosity (LINER-type) or higher-luminosity (Seyfert or composite-type) AGN. We then investigate when the major mergers that first create the black holes are predicted to occur. High mass galaxies are predicted to have formed their black holes at very early epochs. The majority of low mass galaxies never experience a major merger and hence do not contain a black hole, but a significant fraction of the supermassive black holes that do exist in low mass galaxies are predicted to have formed recently. arXiv:0801.3557 [ps, pdf, other] Title: Large Scale Structures at High Redshift in the GOODS Field Authors: M. Castellano, S. Salimbeni, D. Trevese, L. Pentericci, A. Grazian, A. Fontana, E. Giallongo, P. Santini, S. Cristiani, M. Nonino, E. Vanzella Comments: 4 pages, 2 figures. To appear in the proceedings of `A Century of Cosmology', S. Servolo, August 2007, to be published in Il Nuovo Cimento Subjects: Astrophysics (astro-ph) We present a catalogue of overdensities in the GOODS-South field. We find various high density peaks that are embedded in structures diffused on the entire field, up to z ~ 2.5. The slope of their colour-magnitude relation does not show significative evolution with z. We find evidence that galaxies forming these structures are more massive than galaxies located in low density regions. We also analyse the variation of galaxy properties with the associated environmental density and we find that the segregation of red galaxies with density is stronger at low redshift and at high luminosities while it gets much weaker for increasing z. arXiv:0801.3650 [pdf] Title: Submillimeter Galaxies at z~2: Evidence for Major Mergers & Constraints on Lifetimes, IMF and CO-H2 Conversion Factor Authors: L.J. Tacconi, R. Genzel, I. Smail, R. Neri, S.C. Chapman, R.J. Ivison, A. Blain, P.Cox, A. Omont, F. Bertoldi, T. Greve, N.M. Foerster Schreiber, S. Genel, D. Lutz, A.M. Swinbank, A.E. Shapley, D.K. Erb, A. Cimatti, E. Daddi, A.J. Baker Comments: 61 pages, 10 figures, Accepted for publication in ApJ Subjects: Astrophysics (astro-ph) We report sub-arcsecond resolution IRAM PdBI millimeter CO interferometry of four z~2 submillimeter galaxies (SMGs), and sensitive CO (3-2) flux limits toward three z~2 UV-/optically selected star forming galaxies. The new data reveal for the first time spatially resolved CO gas kinematics in the observed SMGs. Two of the SMGs show double or multiple morphologies, with complex, disturbed gas motions. The other two SMGs exhibit CO velocity gradients of ~500 km/s across 0.2 arcsec (1.6 kpc) diameter regions, suggesting that the star forming gas is in compact, rotating disks. Our data provide compelling evidence that these SMGs represent extreme, short-lived 'maximum' star forming events in highly dissipative mergers of gas rich galaxies. The resulting high mass surface and volume densities of SMGs are similar to those of compact quiescent galaxies in the same redshift range, and much higher than those in local spheroids. From the ratio of the comoving volume densities of SMGs and quiescent galaxies in the same mass and redshift ranges, and from the comparison of gas exhaustion time scales and stellar ages, we estimate that the SMG phase duration is about 100 Myrs. Our analysis of SMGs and optically/UV selected high redshift star forming galaxies supports a 'universal' Chabrier IMF as being valid over the star forming history of these galaxies. We find that the 12CO luminosity to total gas mass conversion factors at z~2-3 are probably similar to those assumed at z~0. The implied gas fractions in our sample galaxies range from 20 to 50%. arXiv:0801.3825 [ps, pdf, other] Title: NICMOS Measurements of the Near Infrared Background Authors: Rodger I. Thompson, Daniel Eisenstein, Xiaohui Fan, Marcia Rieke, Robert Kennicutt Comments: To appear in the proceedings of A Century of Cosmology - Past, present and future, San Servolo, Venice, Italy, 27-31 August 2007 Subjects: Astrophysics (astro-ph) This paper addresses the nature of the near infrared background. We investigate whether there is an excess background at 1.4 microns, what is the source of the near infrared background and whether that background after the subtraction of all known sources contains the signature of high redshift objects (Z > 10). Based on NICMOS observations in the Hubble Ultra Deep Field and the Northern Hubble Deep Field we find that there is no excess in the background at 1.4 microns and that the claimed excess is due to inaccurate models of the zodiacal background. We find that the near infrared background is now spatially resolved and is dominated by galaxies in the redshift range between 0.5 and 1.5. We find no signature than can be attributed to high redshift sources after subtraction of all known sources either in the residual background or in the fluctuations of the residual background. We show that the color of the fluctuations from both NICMOS and Spitzer observations are consistent with low redshift objects and inconsistent with objects at redshifts greater than 10. It is most likely that the residual fluctuation power after source subtraction is due to the outer regions of low redshift galaxies that are below the source detection limit and therefore not removed during the source subtraction. [34