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 \times 10 ^ { 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 _ { 0.5 - 10 ~ { } { keV } } > 2 \times 10 ^ { 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 \sim 80 \% that may include late-stage mergers .