arXiv:0911.3897 [ps, pdf, other]
    Title: Neutral Gas Outflows and Inflows in Infrared-Faint Seyfert Galaxies
    Authors: Hannah B. Krug, David S. N. Rupke, Sylvain Veilleux
    Comments: 50 pages, 12 figures, accepted for publication in ApJ
    Subjects: Galaxy Astrophysics (astro-ph.GA)

    Previous studies of the Na I D interstellar absorption line doublet have shown that galactic winds occur in most galaxies with high infrared luminosities. However, in infrared-bright composite systems where a starburst coexists with an active galactic nucleus (AGN), it is unclear whether the starburst, the AGN, or both are driving the outflows. The present paper describes the results from a search for outflows in 35 infrared-faint Seyferts with 10^9.9 < L_IR/L_sun < 10^11, or, equivalently, star formation rates (SFR) of ~0.4 -- 9 solar masses per year, to attempt to isolate the source of the outflow. We find that the outflow detection rates for the infrared-faint Seyfert 1s (6%) and Seyfert 2s (18%) are lower than previously reported for infrared-luminous Seyfert 1s (50%) and Seyfert 2s (45%). The outflow kinematics of infrared-faint and infrared-bright Seyfert 2 galaxies resemble those of starburst galaxies, while the outflow velocities in Seyfert 1 galaxies are significantly larger. Taken together, these results suggest that the AGN does not play a significant role in driving the outflows in most infrared-faint and infrared-bright systems, except the high-velocity outflows seen in Seyfert 1 galaxies. Another striking result of this study is the high rate of detection of inflows in infrared-faint galaxies (39% of Seyfert 1s, 35% of Seyfert 2s), significantly larger than in infrared-luminous Seyferts (15%). This inflow may be contributing to the feeding of the AGN in these galaxies, and potentially provides more than enough material to power the observed nuclear activity over typical AGN lifetimes.

 arXiv:0911.3900 [ps, pdf, other]
    Title: Mapping the stellar structure of the Milky Way
    Authors: Jelte T. A. de Jong (1), Brian Yanny (2), Hans-Walter Rix (1), Andrew E. Dolphin (3), Nicolas F. Martin (1), Timothy C. Beers (4) ((1) Max-Planck-Institut fuer Astronomie, (2) Fermi National Accelerator Laboratory, (3) Raytheon Company, (4) Michigan State University)
    Comments: 12 pages, 10 figures, submitted to Astrophysical Journal
    Subjects: Galaxy Astrophysics (astro-ph.GA)

    We map the stellar structure of the Galaxy by applying color-magnitude diagram (CMD) fitting to photometric data from the SEGUE survey allowing, for the first time, a comprehensive analysis of Milky Way structure at both high and low latitudes using uniform SDSS photometry. The advantage of CMD fitting is that it incorporates photometry of all relevant stars simultaneously, bypassing the need to choose single tracer populations. Using three template stellar populations we obtain a sparse 3-D map of the stellar mass distribution. Fitting a smooth Milky Way model, comprised of exponential thin and thick disks and an axisymmetric power-law halo, allows us to constrain the structural parameters of the thick disk and halo. The thick disk scale height and length of such models are well constrained at 0.75+-0.07 kpc and 4.1+-0.4 kpc, respectively. We find a stellar halo flattening within ~25 kpc of c/a=0.88+-0.03 and a power-law index of 2.75+-0.07. The model fits yield densities at the solar location of rho_{thick,0}=10^{-2.3+-0.1} M_\sun pc^{-3} and rho_{halo,0}=10^{-4.20+-0.05} M_\sun pc^{-3}. We detect in-situ evidence for a metallicity gradient in the stellar halo: within R<~15 kpc the stellar halo has a mean metallicity of [Fe/H]=-1.6, which shifts to [Fe/H]=-2.2 at larger radii. Subtraction of the best-fit smooth and symmetric model from the density maps reveals a wealth of substructures at all latitudes, some attributable to known streams and overdensities, and some new. A simple warp cannot account for the low latitude substructure, as overdensities occur simultaneously above and below the Galactic plane. (abridged)

 arXiv:0911.3914 [ps, pdf, other]
    Title: The [OIII] emission line luminosity function of optically selected type-2 AGN from zCOSMOS
    Authors: A. Bongiorno, M. Mignoli, G. Zamorani, F. Lamareille, G. Lanzuisi, T. Miyaji, M. Bolzonella, C. M. Carollo, T. Contini, J. P. Kneib, O. Le Fevre, S. J. Lilly, V. Mainieri, A. Renzini, M. Scodeggio, S. Bardelli, M. Brusa, K. Caputi, F. Civano, G. Coppa, O. Cucciati, S. de la Torre, L. de Ravel, P. Franzetti, B. Garilli, C. Halliday, G. Hasinger, A. M. Koekemoer, A. Iovino, P. Kampczyk, C. Knobel, K. Kovac, J.-F. Le Borgne, V. Le Brun, C. Maier, A. Merloni, P. Nair, R. Pello, Y. Peng, E. Perez Montero, E. Ricciardelli, M. Salvato, J. Silverman, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, E. Zucca, 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, L. Pozzetti, R. Scaramella
    Comments: 20 pages, 11 figures, accepted for publication in Astronomy and Astrophysics
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    We present a catalog of 213 type-2 AGN selected from the zCOSMOS survey. The selected sample covers a wide redshift range (0.15<z<0.92) and is deeper than any other previous study, encompassing the luminosity range 10^{5.5} < Lsun< L[OIII] < 10^{9.1} Lsun. We explore the intrinsic properties of these AGN and the relation to their X-ray emission (derived from the XMM-COSMOS observations). We study their evolution by computing the [OIII]5007A line luminosity function (LF) and we constrain the fraction of obscured AGN as a function of luminosity and redshift. The sample was selected on the basis of the optical emission line ratios, after applying a cut to the signal-to-noise ratio (S/N) of the relevant lines. We used the standard diagnostic diagrams [OIII]/Hbeta versus [NII]/Halpha and ([OIII]/Hbeta versus [SII]/Halpha) to isolate AGN in the redshift range 0.15<z<0.45 and the diagnostic diagram [OIII]/Hbeta versus [OII]/Hbeta to extend the selection to higher redshift (0.5<z<0.92). Combining our sample with one drawn from SDSS, we found that the best description of the evolution of type-2 AGN is a luminosity-dependent density evolution model. Moreover, using the type-1 AGN LF we were able to constrain the fraction of type-2 AGN to the total (type-1 + type-2) AGN population. We found that the type-2 fraction decreases with luminosity, in agreement with the most recent results, and shows signs of a slight increase with redshift. However, the trend with luminosity is visible only after combining the SDSS+zCOSMOS samples. From the COSMOS data points alone, the type-2 fraction seems to be quite constant with luminosity.

(end of monday)


 arXiv:0911.4297 [ps, pdf, other]
    Title: Environment of MAMBO galaxies in the COSMOS field
    Authors: Manuel Aravena, Frank Bertoldi, Chris L. Carilli, Eva Schinnerer, Henry J. McCracken, Mara Salvato, Dominik Riechers, Kartik Sheth, Vernesa Smolcic, Peter Capak, Anton Koekemoer, Karl M. Menten
    Comments: Accepted for publication in ApJ Letters
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    Submillimeter galaxies (SMG) represent a dust-obscured high-redshift population undergoing massive star formation activity. Their properties and space density have suggested that they may evolve into spheroidal galaxies residing in galaxy clusters. In this paper, we report the discovery of compact (~10"-20") galaxy overdensities centered at the position of three SMGs detected with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field. These associations are statistically significant. The photometric redshifts of galaxies in these structures are consistent with their associated SMGs; all of them are between z=1.4-2.5, implying projected physical sizes of ~170 kpc for the overdensities. Our results suggest that about 30% of the radio-identified bright SMGs in that redshift range form in galaxy density peaks in the crucial epoch when most stars formed.


 arXiv:0911.4297 [ps, pdf, other]
    Title: Environment of MAMBO galaxies in the COSMOS field
    Authors: Manuel Aravena, Frank Bertoldi, Chris L. Carilli, Eva Schinnerer, Henry J. McCracken, Mara Salvato, Dominik Riechers, Kartik Sheth, Vernesa Smolcic, Peter Capak, Anton Koekemoer, Karl M. Menten
    Comments: Accepted for publication in ApJ Letters
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    Submillimeter galaxies (SMG) represent a dust-obscured high-redshift population undergoing massive star formation activity. Their properties and space density have suggested that they may evolve into spheroidal galaxies residing in galaxy clusters. In this paper, we report the discovery of compact (~10"-20") galaxy overdensities centered at the position of three SMGs detected with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field. These associations are statistically significant. The photometric redshifts of galaxies in these structures are consistent with their associated SMGs; all of them are between z=1.4-2.5, implying projected physical sizes of ~170 kpc for the overdensities. Our results suggest that about 30% of the radio-identified bright SMGs in that redshift range form in galaxy density peaks in the crucial epoch when most stars formed.

 arXiv:0911.4297 [ps, pdf, other]
    Title: Environment of MAMBO galaxies in the COSMOS field
    Authors: Manuel Aravena, Frank Bertoldi, Chris L. Carilli, Eva Schinnerer, Henry J. McCracken, Mara Salvato, Dominik Riechers, Kartik Sheth, Vernesa Smolcic, Peter Capak, Anton Koekemoer, Karl M. Menten
    Comments: Accepted for publication in ApJ Letters
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    Submillimeter galaxies (SMG) represent a dust-obscured high-redshift population undergoing massive star formation activity. Their properties and space density have suggested that they may evolve into spheroidal galaxies residing in galaxy clusters. In this paper, we report the discovery of compact (~10"-20") galaxy overdensities centered at the position of three SMGs detected with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field. These associations are statistically significant. The photometric redshifts of galaxies in these structures are consistent with their associated SMGs; all of them are between z=1.4-2.5, implying projected physical sizes of ~170 kpc for the overdensities. Our results suggest that about 30% of the radio-identified bright SMGs in that redshift range form in galaxy density peaks in the crucial epoch when most stars formed.


 arXiv:0911.4480 [pdf, other]
    Title: The Origin of the Hubble Sequence in Lambda-CDM Cosmology
    Authors: Andrew J. Benson (1), Nick Devereux (2) ((1) California Institute of Technology, (2) Embry-Riddle Aeronautical University)
    Comments: Accepted for publication in MNRAS
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    The Galform semi-analytic model of galaxy formation is used to explore the mechanisms primarily responsible for the three types of galaxies seen in the local universe: bulge, bulge+disk and disk, identified with the visual morphological types E, S0/a-Sbc, and Sc-Scd, respectively. With a suitable choice of parameters the Galform model can accurately reproduce the observed local K_s-band luminosity function (LF) for galaxies split by visual morphological type. The successful set of model parameters is used to populate the Millennium Simulation with 9.4 million galaxies and their dark matter halos. The resulting catalogue is then used to explore the evolution of galaxies through cosmic history. The model predictions concur with recent observational results including the galaxy merger rate, the star formation rate and the seemingly anti-hierarchical evolution of ellipticals. However, the model also predicts significant evolution of the elliptical galaxy LF that is not observed. The discrepancy raises the possibility that samples of z~1 galaxies which have been selected using colour and morphological criteria may be contaminated with galaxies that are not actually ellipticals.

 arXiv:0911.4484 [pdf, other]
    Title: There's no place like home? Statistics of Milky Way-mass dark matter halos
    Authors: Michael Boylan-Kolchin, Volker Springel, Simon D. M. White, Adrian Jenkins
    Comments: 18 pages, 15 figures; submitted to MNRAS
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    We present an analysis of the distribution of structural properties for Milky Way-mass halos in the Millennium-II Simulation (MS-II). This simulation of structure formation within the standard LCDM cosmology contains thousands of Milky Way-mass halos and has sufficient resolution to properly resolve many subhalos per host. It thus provides a major improvement in the statistical power available to explore the distribution of internal structure for halos of this mass. In addition, the MS-II contains lower resolution versions of the Aquarius Project halos, allowing us to compare our results to simulations of six halos at a much higher resolution. We study the distributions of mass assembly histories, of subhalo mass functions and accretion times, and of merger and stripping histories for subhalos capable of impacting disks at the centers of halos. We show that subhalo abundances are not well-described by Poisson statistics at low mass, but rather are dominated by intrinsic scatter. Using the masses of subhalos at infall and the abundance-matching assumption, there is less than a 10% chance that a Milky Way halo with M_vir =10^12 M_sun will host two galaxies as bright as the Magellanic Clouds. This probability rises to ~25% for a halo with M_vir=2.5 x 10^12 M_sun. The statistics relevant for disk heating are very sensitive to the mass range that is considered relevant. Mergers with mass ratio at accretion greater than 1:30 could well impact a central galactic disk and are a near inevitability since z=2, whereas only half of all halos have had a merger with mass ratio at accretion greater than 1:10 over this same period.

 arXiv:0911.4515 [pdf, other]
    Title: A Multiwavelength Study of a Sample of 70 micron Selected Galaxies in the COSMOS Field I: Spectral Energy Distributions and Luminosities
    Authors: Jeyhan S. Kartaltepe, D. B. Sanders, E. Le Floc'h, D. T. Frayer, H. Aussel, S. Arnouts, O. Ilbert, M. Salvato, N. Z. Scoville, J. Surace, L. Yan, M. Brusa, P. Capak, K. Caputi, C. M. Carollo, F. Civano, M. Elvis, C. Faure, G. Hasinger, A. M. Koekemoer, N. Lee, S. Lilly, C. T. Liu, H. J. McCracken, E. Schinnerer, V. Smolcic, Y. Taniguchi, D. J. Thompson, J. Trump
    Comments: 31 pages including 31 figures and 6 tables. Accepted for publication in ApJ. The full resolution version is available here: this http URL
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    We present a large robust sample of 1503 reliable and unconfused 70microm selected sources from the multiwavelength data set of the Cosmic Evolution Survey (COSMOS). Using the Spitzer IRAC and MIPS photometry, we estimate the total infrared luminosity, L_IR (8--1000 microns), by finding the best fit template from several different template libraries. The long wavelength 70 and 160 micron data allow us to obtain a reliable estimate of L_IR, accurate to within 0.2 and 0.05 dex, respectively. The 70 micron data point enables a significant improvement over the luminosity estimates possible with only a 24 micron detection. The full sample spans a wide range in L_IR, L_IR ~ 10^8-10^14 L_sun, with a median luminosity of 10^11.4 L_sun. We identify a total of 687 luminous, 303 ultraluminous, and 31 hyperluminous infrared galaxies (LIRGs, ULIRGs, and HyLIRGs) over the redshift range 0.01<z<3.5 with a median redshift of 0.5. Presented here are the full spectral energy distributions for each of the sources compiled from the extensive multiwavelength data set from the ultraviolet (UV) to the far-infrared (FIR). Using SED fits we find possible evidence for a subset of cooler ultraluminous objects than observed locally. However, until direct observations at longer wavelengths are obtained, the peak of emission and the dust temperature cannot be well constrained. We use these SEDs, along with the deep radio and X-ray coverage of the field, to identify a large sample of candidate active galactic nuclei (AGN). We find that the fraction of AGN increases strongly with L_IR, as it does in the local universe, and that nearly 70% of ULIRGs and all HyLIRGs likely host a powerful AGN.


New submissions for Thu, 26 Nov 09

[1]  arXiv:0911.4718 [ps, pdf, other]
    Title: Testing Properties of the Galactic Center Black Hole Using Stellar Orbits
    Authors: David Merritt, Tal Alexander, Seppo Mikkola, Clifford M. Will
    Comments: 18 pages, 9 figures
    Subjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    The spin and quadrupole moment of the supermassive black hole at the Galactic center can in principle be measured via astrometric monitoring of stars orbiting at milliparsec (mpc) distances, allowing tests of general relativistic "no-hair" theorems (Will 2008). One complicating factor is the presence of perturbations from other stars, which may induce orbital precession of the same order of magnitude as that due to general relativistic effects. The expected number of stars in this region is small enough that full N-body simulations can be carried out. We present the results of a comprehensive set of such simulations, which include a post-Newtonian treatment of spin-orbit effects. A number of possible models for the distribution of stars and stellar remnants are considered. We find that stellar perturbations are likely to obscure the signal due to frame-dragging for stars beyond ~0.5 mpc from the black hole, while measurement of the quadrupole moment is likely to require observation of stars inside ~0.2 mpc. A high fraction of stellar remnants, e.g. 10-Solar-mass black holes, in this region would make tests of GR problematic at all radii. We discuss the possibility of separating the effects of stellar perturbations from those due to GR.


[8]  arXiv:0911.4753 [pdf, other]
    Title: Maximum likelihood method for fitting the Fundamental Plane of the 6dF Galaxy Survey
    Authors: Christina Magoulas, Matthew Colless, D. Heath Jones, Christopher M. Springob, Jeremy R. Mould
    Comments: 3 pages, 1 figure, to appear in the proceedings of the IAU Symposium 262 "Stellar Populations: Planning for the Next Decade", Charlot and Bruzual eds
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    We have used over 10,000 early-type galaxies from the 6dF Galaxy Survey (6dFGS) to construct the Fundamental Plane across the optical and near-infrared passbands. We demonstrate that a maximum likelihood fit to a multivariate Gaussian model for the distribution of galaxies in size, surface brightness and velocity dispersion can properly account for selection effects, censoring and observational errors, leading to precise and unbiased parameters for the Fundamental Plane and its intrinsic scatter. This method allows an accurate and robust determination of the dependencies of the Fundamental Plane on variations in the stellar populations and environment of early-type galaxies.


  arXiv:0911.4925 [ps, pdf, other]
    Title: The Linearity of the Cosmic Expansion Field from 300 to 30,000 km/s and the Bulk Motion of the Local Supercluster with Respect to the CMB
    Authors: A. Sandage (1), B. Reindl (2), G.A. Tammann (2) ((1) Observatories Carnegie Inst. Washington, (2) Department of Physics and Astronomy, Univ. of Basel)
    Comments: 54 pages, 12 figures, 6 tables; submitted to The Astrophysical Journal
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    The meaning of "linear expansion" is explained. Particularly accurate relative distances are compiled and homogenized a) for 246 SNe Ia and 35 clusters with v<30,000 km/s, and b) for relatively near galaxies with 176 TRGB and 30 Cepheid distances. The 487 objects define a tight Hubble diagram from 300-30,000 km/s implying individual distance errors of <7.5%. Here the velocities are corrected for Virgocentric steaming (locally 220 km/s) and - if v_220>3500 km/s - for a 495 km/s motion of the Local Supercluster towards the warm CMB pole at l=275, b=12; local peculiar motions are averaged out by large numbers. A test for linear expansion shows that the corrected velocities increase with distance as predicted by a standard model with q_0=-0.55 [corresponding to (Omega_M, Omega_Lambda)=(0.3,0.7)], but the same holds - due to the distance limitation of the present sample - for a range of models with q_0 between ~0.00 and -1.00. For these models H_0 does not vary systematically by more than +/-2.3% over the entire range. Local, distance-dependent variations are equally limited to 2.3% on average. In particular the proposed Hubble Bubble of Zehavi et al. and Jha et al. is rejected at the 4sigma level. - Velocity residuals in function of the angle from the CMB pole yield a coherence radius of the Local Supercluster of ~3500 km/s (~56 Mpc), beyond which galaxies are at rest in co-moving coordinates with respect to the CMB. Since no obvious single accelerator of the Local Supercluster exists in the direction of the CMB dipole its motion must be due to the integral gravitational force of all surrounding structures.
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