The Impact of Galaxy Interactions on Active Galactic Nucleus Activity in zCOSMOS
Finoguenov, A.; Jahnke, K.; Silverman, J. D.; Salvato, M.; Bolzonella, M.; Andrae, R.; Vignali, C.; Gilli, R.; Comastri, A.; Cappelluti, N.; Brusa, M.; Halliday, C.; Tanaka, M.; Hasinger, G.; Mainieri, V.; Koekemoer, A. M.; Ho, L. C.; Caputi, K.; Carollo, C. M.; Civano, F.; Elvis, M.; Mignoli, M.; Zamorani, G.; Tasca, L.; Le Fèvre, O.; Peng, Y.; Garilli, B.; Bardelli, S.; Zucca, E.; Cappi, A.; Cucciati, O.; Scodeggio, M.; Hao, H.; Bongiorno, A.; Lilly, S. J.; Pérez-Montero, E.; Pello, R.; Contini, T.; Tresse, L.; Kampczyk, P.; Fu, H.; Coppa, G.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Iovino, A.; Knobel, C.; Kovač, K.; Lamareille, F.; Le Borgne, J. -F.; Le Brun, V.; Maier, C.; Ricciardelli, E.; Vergani, D.; Nair, P.
Japan, Switzerland, Germany, United States, Italy, France, United Kingdom
Abstract
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 × 1010 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 0.5-10 keV > 2 × 1042 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.