The Impact of Galaxy Interactions on Active Galactic Nucleus Activity in zCOSMOS

none55Close 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 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.mixedSilverman J.D.; Kampczyk P.; Jahnke K.; Andrae R.; Lilly S.J.; Elvis M.; Civano F.; Mainieri V.; Vignali C.; Zamorani G.; Nair P.; Le Fevre O.; de Ravel L.; Bardelli S.; Bongiorno A.; Bolzonella M.; Cappi A.; Caputi K.; Carollo C.M.; Contini T.; Coppa G.; Cucciati O.; de la Torre S.; Franzetti P.; Garilli B.; Halliday C.; Hasinger G.; Iovino A.; Knobel C.; Koekemoer A.M.; Kovac K.; Lamareille F.; Le Borgne J.-F.; Le Brun V.; Maier C.; Mignoli M.; Pello R.; Perez-Montero E.; Ricciardelli E.; Peng Y.; Scodeggio M.; Tanaka M.; Tasca L.; Tresse L.; Vergani D.; Zucca E.; Brusa M.; Cappelluti N.; Comastri A.; Finoguenov A.; Fu H.; Gilli R.; Hao H.; Ho L.C.; Salvato M.Silverman J.D.; Kampczyk P.; Jahnke K.; Andrae R.; Lilly S.J.; Elvis M.; Civano F.; Mainieri V.; Vignali C.; Zamorani G.; Nair P.; Le Fevre O.; de Ravel L.; Bardelli S.; Bongiorno A.; Bolzonella M.; Cappi A.; Caputi K.; Carollo C.M.; Contini T.; Coppa G.; Cucciati O.; de la Torre S.; Franzetti P.; Garilli B.; Halliday C.; Hasinger G.; Iovino A.; Knobel C.; Koekemoer A.M.; Kovac K.; Lamareille F.; Le Borgne J.-F.; Le Brun V.; Maier C.; Mignoli M.; Pello R.; Perez-Montero E.; Ricciardelli E.; Peng Y.; Scodeggio M.; Tanaka M.; Tasca L.; Tresse L.; Vergani D.; Zucca E.; Brusa M.; Cappelluti N.; Comastri A.; Finoguenov A.; Fu H.; Gilli R.; Hao H.; Ho L.C.; Salvato M