A Second Look at 12 Candidate Dual AGNs Using BAYMAX

Abstract

We present an analysis of 12 optically selected dual active galactic nucleus (AGN) candidates at z  < 0.34. Each candidate was originally identified via double-peaked [O iii ] λ 5007 emission lines and received follow-up Chandra and Hubble Space Telescope ( HST ) observations. Because the X-ray data are low-count (<100 counts) with small separations (<1″), a robust analysis is necessary for classifying each source. Pairing long-slit [O iii ] observations with existing Chandra observations, we re-analyze the X-ray observations with Bayesian AnalYsis of AGNs in X-rays to determine whether the X-ray emission from each system is more likely a single or dual point source. We find that 4 of the 12 sources are likely dual X-ray point-source systems. We examine each point source’s spectra via a Monte Carlo method that probabilistically identifies the likely origin of each photon. When doing so, we find that (i) the secondary X-ray point sources in two of the systems have L X  < 10 40 erg s −1 , such that we cannot rule out a non-AGN origin, (ii) one source has a secondary with L X  > 10 40 erg s −1 but a spectrum that is too soft to definitively preclude being X-ray emitting diffuse gas that was photoionized by the primary AGN, and (iii) one system (SDSS J1126+2944) is a dual AGN. Additionally, using complementary HST observations, we analyze a subsample of systems that are visually identified as merging. Our results suggest that dual AGNs may preferentially reside in mergers with small separations, consistent with both simulations and observations.