The impact of galaxy interactions on AGN activity in zCOSMOS
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*>2.5x10^10 M_sun) 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_x>2x10^42 erg s^-1) detected by Chandra. We find a higher fraction of 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 to estimate 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_{-7.4}^{+8.4}% 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.
Keywords
Cite
@article{arxiv.1109.1292,
title = {The impact of galaxy interactions on AGN activity in zCOSMOS},
author = {J. D. Silverman and P. Kampczyk and K. Jahnke and R. Andrae and S. Lilly and M. Elvis and F. Civano and V. Mainieri and C. Vignali and G. Zamorani and P. Nair and O. Le Fevre and L. de Ravel and S. Bardelli and A. Bongiorno and M. Bolzonella and M. Brusa and N. Cappelluti and A. Cappi and K. Caputi and C. M. Carollo and T. Contini and G. Coppa and O. Cucciati and S. de la Torre and P. Franzetti and B. Garilli and C. Halliday and G. Hasinger and A. Iovino and C. Knobel and A. koekemoer and K. Kovac and F. Lamareille and J. -F. Le Borgne and V. Le Brun and C. Maier and M. Mignoli and R. Pello and E. Perez Montero and E. Ricciardelli and Y. Peng and M. Scodeggio and M. Tanaka and L. Tasca and L. Tresse and D. Vergani and E. Zucca and A. Comastri and A. Finoguenov and H. Fu and R. Gilli and H. Hao and L. Ho and M. Salvato},
journal= {arXiv preprint arXiv:1109.1292},
year = {2015}
}
Comments
11 pages, 8 figures, Accepted by The Astrophysical Journal