VLT/MUSE Study of Close Active Galactic Nucleus Pairs and Host Galaxies in the Local Universe. I. Overview of the Ionized Gas

Abstract

Studying active galactic nucleus (AGN) pairs and their host galaxies is essential for understanding the interplay between galaxy mergers and key internal processes such as supermassive black hole fueling and feedback. We crossmatch between the Big Multi-AGN Catalog and the public data archive of the Very Large Telescope (VLT)/MUSE, and obtain 12 AGN pair candidates in the local Universe (z ≲ 0.1) with a projected distance of rp ≤ 20 kpc. Using archival VLT/MUSE data, we present a spatially resolved study of the ionized gas kinematics and ionization properties of these 12 AGN pair candidates. By decomposing the optical emission lines into two Gaussian components, we try to separate gas associated with disk rotation from noncircular motions. We further identify dominant ionization mechanisms using spatially resolved Baldwin–Phillips–Terlevich diagnostics. We find that both nuclei in four of the 12 systems are classified as a Seyfert or LINER. In addition, three nuclei are classified as star-forming or composite in the optical diagnostics, but are identified as AGNs at other wavelengths. Kinematically, regularly rotating ionized gas disks are detected in 16 of 24 nuclei. Prominent tidal features traced by ionized gas are also detected in nine systems. Ionized gas outflows are widespread and are detected in 18 nuclei. Finally, for three nuclei (Mrk 739A, NGC 7592B, and J1544+0446A), we find evidence for fading AGN activity over the past several tens of thousands of years, based on optical emission-line ratios and an assumed AGN photoionization model.