Chandra survey of optically selected AGN pairs

Active galactic nucleus (AGN) pairs are an ideal laboratory to study the effects of galaxy merger in the standard paradigm of galaxy formation and evolution. We present a Chandra archival survey of AGN pairs at median redshift ~0.1, which were systematically identified from the Sloan Digital Sky Survey with projected separations rp < 100 kpc and velocity offsets <600 km s^-1. Out of the 1286 AGN pairs, we find 64 pairs with Chandra observations, making it currently the largest sample of AGN pairs studied in the X-ray band. The X-ray incidence rate, 67/128=52%+/-6%, is significantly higher than that (23/178=13%+/-3%) of a control sample of galaxy pairs which do not exhibit optical AGNs in their center, lending support to the optical AGN selection. The X-ray luminosity increases with decreasing projected separation in AGN pairs for rp > 10 kpc, suggesting an enhancement of central BH activity, while it decreases when rp < 10 kpc, which may be caused by obscuring, merger-induced gas inflows or gas depletion in the central region of AGNs.