Investigating the Evolution of the Dual AGN System ESO 509-IG066

Abstract

We analyze the evolution of the dual active galactic nucleus (AGN) in ESO 509-IG066, a galaxy pair located at z  = 0.034 whose nuclei are separated by 11 kpc. Previous observations with XMM-Newton on this dual AGN found evidence for two moderately obscured (  ∼ 10 22 cm −2 ) X-ray luminous (  ∼ 10 43 erg s −1 ) nuclear sources. We present an analysis of subsequent Chandra , NuSTAR , and Swift /XRT observations that show one source has dropped in flux by a factor of 10 between 2004 and 2011, which could be explained by either an increase in the absorbing column or an intrinsic fading of the central engine, possibly due to a decrease in mass accretion. Both of these scenarios are predicted by galaxy merger simulations. The source that has dropped in flux is not detected by NuSTAR , which argues against absorption, unless it is extreme. However, new Keck/LRIS optical spectroscopy reveals a previously unreported broad H α line that is highly unlikely to be visible under the extreme absorption scenario. We therefore conclude that the black hole in this nucleus has undergone a dramatic drop in its accretion rate. From AO-assisted near-infrared integral-field spectroscopy of the other nucleus, we find evidence that the galaxy merger is having a direct effect on the kinematics of the gas close to the nucleus of the galaxy, providing a direct observational link between the galaxy merger and the mass accretion rate onto the black hole.