Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 409, Issue 2, Pages 491-499Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2966.2010.17337.x
Keywords
galaxies: evolution; galaxies: haloes; galaxies: star formation; galaxies: statistics; galaxies: stellar content; galaxies: structure
Categories
Funding
- Alfred P. Sloan Foundation
- National Aeronautics and Space Administration
- National Science Foundation
- US Department of Energy
- Japanese Monbukagakusho
- Max Planck Society
- University of Chicago
- Fermilab
- Institute for Advanced Study
- Japan Participation Group
- Johns Hopkins University
- Korean Scientist Group
- Los Alamos National Laboratory
- Max-Planck-Institute for Astronomy (MPIA)
- Max-Planck-Institute for Astrophysics (MPA)
- New Mexico State University
- University of Pittsburgh
- University of Portsmouth
- Princeton University
- United States Naval Observatory
- University of Washington
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We have compiled a large sample of isolated central galaxies from the Sloan Digital Sky Survey, which do not have a neighbour of comparable brightness within a projected distance of 1 Mpc. We use the colours, luminosities and surface brightnesses of satellite galaxies in the vicinity of these objects to estimate their neutral gas content and to derive the average total mass of HI gas contained in the satellites as a function of the projected radius from the primary. Recent calibrations of merging time-scales from N-body simulations are used to estimate the rate at which this gas will accrete on to the primary galaxies. Our estimated accretion rate falls short of that needed to maintain the observed level of star formation in the primaries by nearly two orders of magnitude. Nevertheless, there are strong correlations between the total mass of gas in satellites and the colours and specific star formation rates of primary galaxies of all stellar masses. The correlations are much weaker, if we consider the total stellar mass in satellites, rather than their total gas mass. We ask why star formation in the primaries should be correlated with gas contained in satellites at projected separations of an Mpc or more, well outside the virial radius of the dark matter haloes of these systems. We suggest that gas-rich satellites trace an underlying reservoir of ionized gas that is accreted continuously and that provides fuel for the ongoing star formation in galaxies in the local Universe.
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