Silverman, J. D. and Fu, H. (2011) The Impact of Galaxy Interactions on Active Galactic Nucleus Activity in zCosmos. Astrophysical Journal, 743 (1). Art. No. 2. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20120201-153641202
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Close encounters between galaxies are expected to be a viable mechanism, as predicted by numerical simulations, by which accretion onto supermassive black holes can be initiated. To test this scenario, we construct a sample of 562 galaxies (M_* > 2.5 × 10^(10) M_☉) in kinematic pairs over the redshift range 0.25 < z < 1.05 that are more likely to be interacting than a well-matched control sample of 2726 galaxies not identified as being in a pair, both from the zCOSMOS 20k spectroscopic catalog. Galaxies that harbor an active galactic nucleus (AGN) are identified on the basis of their X-ray emission (L_(0.5-10keV) > 2 × 10^(42) erg s^(–1)) detected by Chandra. We find a higher fraction of an AGN in galaxies in pairs relative to isolated galaxies of similar stellar mass. Our result is primarily due to an enhancement of AGN activity, by a factor of 1.9 (observed) and 2.6 (intrinsic), for galaxies in pairs of projected separation less than 75 kpc and line-of-sight velocity offset less than 500 km s^(–1). This study demonstrates that close kinematic pairs are conducive environments for black hole growth, either indicating a causal physical connection or an inherent relation, such as, to enhanced star formation. In the Appendix, we describe a method for estimating the intrinsic fractions of galaxies (either in pairs or the field) hosting an AGN with confidence intervals, and an excess fraction in pairs. We estimate that 17.8^(+8.4)_(–7.4)% of all moderate-luminosity AGN activity takes place within galaxies undergoing early stages of interaction that leaves open the question as to what physical processes are responsible for fueling the remaining ~80% that may include late-stage mergers.
|Additional Information:||© 2011 The American Astronomical Society. Received 2011 July 15; accepted 2011 August 29; published 2011 November 17. The authors appreciate the useful discussions with Charles Steinhardt, Yen-Ting Lin, and Ed Turner. This work was supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. K.J. is supported by the Emmy Noether Programme by the German Science Foundation (DFG). R.A. is funded by the Klaus Tschira Foundation via the Heidelberg Graduate School of Fundamental Physics (HGSFP). Facilities: CXO(ACIS), VLT:Melipal (VIMOS).|
|Subject Keywords:||galaxies: active; galaxies: interactions; quasars: general; X-rays: galaxies|
|Official Citation:||The Impact of Galaxy Interactions on Active Galactic Nucleus Activity in zCOSMOS J. D. Silverman et al. 2011 ApJ 743 2|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||02 Feb 2012 15:32|
|Last Modified:||08 Jul 2015 15:18|
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