Walker, Lisa May and Johnson, Kelsey E. and Gallagher, Sarah C. and Hibbard, John E. and Hornschemeier, Ann E. and Tzanavaris, Panayiotis and Charlton, Jane C. and Jarrett, Thomas H. (2010) Mid-infrared Evidence for Accelerated Evolution in Compact Group Galaxies. Astronomical Journal, 140 (5). pp. 1254-1267. ISSN 0004-6256 http://resolver.caltech.edu/CaltechAUTHORS:20101110-110618516
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Compact galaxy groups are at the extremes of the group environment, with high number densities and low velocity dispersions that likely affect member galaxy evolution. To explore the impact of this environment in detail, we examine the distribution in the mid-infrared (MIR) 3.6-8.0 μm color space of 42 galaxies from 12 Hickson compact groups (HCGs) in comparison with several control samples, including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are strongly bimodal, with statistically significant evidence for a gap in their distribution. In contrast, none of the other samples show such a marked gap, and only galaxies in the Coma infall region have a distribution that is statistically consistent with the HCGs in this parameter space. To further investigate the cause of the HCG gap, we compare the galaxy morphologies of the HCG and LVL+SINGS galaxies, and also probe the specific star formation rate (SSFR) of the HCG galaxies. While galaxy morphology in HCG galaxies is strongly linked to position with MIR color space, the more fundamental property appears to be the SSFR, or star formation rate normalized by stellar mass. We conclude that the unusual MIR color distribution of HCG galaxies is a direct product of their environment, which is most similar to that of the Coma infall region. In both cases, galaxy densities are high, but gas has not been fully processed or stripped. We speculate that the compact group environment fosters accelerated evolution of galaxies from star-forming and neutral gas-rich to quiescent and neutral gas-poor, leaving few members in the MIR gap at any time.
|Additional Information:||© 2010 American Astronomical Society. Received 2009 August 14; accepted 2010 August 24; published 2010 October 11. J.C.C. thanks the NSF for funding under award 0908984. K.E.J. gratefully acknowledges support for this paper provided by NSF through CAREER award 0548103 and the David and Lucile Packard Foundation through a Packard Fellowship. S.C.G. thanks the National Science and Engineering Research Council of Canada for support. For helpful discussions on statistical tests, L.M.W. thanks statistics professor Tao Huang. We also thank the anonymous referee for their constructive comments. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.|
|Subject Keywords:||galaxies: clusters: general; galaxies: evolution; galaxies: interactions; galaxies: statistics; infrared: galaxies|
|Classification Code:||PACS: 98.65.Bv; 98.62.Ve; 98.62.Mw; 98.62.Ai|
|Official Citation:||Lisa May Walker et al 2010 The Astronomical Journal 140 1254 doi: 10.1088/0004-6256/140/5/1254|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||11 Nov 2010 16:24|
|Last Modified:||26 Dec 2012 12:37|
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