Farrah, D. and Connolly, B. and Connolly, N. and Spoon, H. W. W. and Oliver, S. and Prosper, H. B. and Armus, L. and Houck, J. R. and Liddle, A. R. and Desai, V. (2009) An Evolutionary Paradigm for Dusty Active Galaxies at Low Redshift. Astrophysical Journal, 700 (1). pp. 395-416. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090821-113423145
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We apply methods from Bayesian inferencing and graph theory to a data set of 102 mid-infrared spectra, and archival data from the optical to the millimeter, to construct an evolutionary paradigm for z < 0.4 infrared-luminous galaxies. We propose that the ultraluminous infrared galaxies (ULIRG) lifecycle consists of three phases. The first phase lasts from the initial encounter until approximately coalescence. It is characterized by homogeneous mid-IR spectral shapes, and IR emission mainly from star formation, with a contribution from an active galactic nucleus (AGN) in some cases. At the end of this phase, a ULIRG enters one of two evolutionary paths depending on the dynamics of the merger, the available quantities of gas, and the masses of the black holes in the progenitors. On one branch, the contributions from the starburst and the AGN to the total IR luminosity decline and increase, respectively. The IR spectral shapes are heterogeneous, likely due to feedback from AGN-driven winds. Some objects go through a brief QSO phase at the end. On the other branch, the decline of the starburst relative to the AGN is less pronounced, and few or no objects go through a QSO phase. We show that the 11.2 μm polycyclic aromatic hydrocarbon feature is a remarkably good diagnostic of evolutionary phase, and identify six ULIRGs that may be archetypes of key stages in this lifecycle.
|Additional Information:||©2009. The American Astronomical Society. Received 2008 December 1; accepted 2009 May 13; published 2009 July 2. We thank the referees for very helpful reports that greatly improved the clarity of the paper, and Steve Young at Hamilton College for computer technical support. This work is based on observations made with the Spitzer Space Telescope, and has made extensive use of the NASA/IPAC Extragalactic Database, both of which are operated by the Jet Propulsion Laboratory, California Institute of Technology under contracts with NASA. This project was supported in part by NSF grant CHE-0116435 as part of the MERCURY supercomputer consortium.21 Support for the IRS GTO team at Cornell University was provided by NASA through Contract Number 1257184 issued by JPL/Caltech. D.F. and S.O. thank the Science and Technologies Facilities Council for support. N.C. gratefully acknowledges support from a Cottrell College Science Award from the Research Corporation. Funding for Cytoscape is provided by a federal grant from the U.S. National Institute of General Medical Sciences (NIGMS) of the National Institutes of Health (NIH) under award number GM070743−01 and the U.S. National Science Foundation (NSF). Corporate funding is provided through a contract from Unilever PLC. Network Workbench was supported in part by the NSF IIS-0513650 award.|
|Subject Keywords:||galaxies: active; galaxies: evolution; galaxies: interactions; infrared: galaxies; methods: data analysis; methods: statistical|
|Official Citation:||An Evolutionary Paradigm for Dusty Active Galaxies at Low Redshift D. Farrah, B. Connolly, N. Connolly, H. W. W. Spoon, S. Oliver, H. B. Prosper, L. Armus, J. R. Houck, A. R. Liddle, and V. Desai 2009 ApJ 700 395-416 doi: 10.1088/0004-637X/700/1/395|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Marie Noren|
|Deposited On:||10 Sep 2009 19:37|
|Last Modified:||26 Dec 2012 11:14|
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