Host galaxies of double-peaked [OIII] emitting AGN: binary AGN or mergers?

TL;DR

This study investigates the nature of double-peaked [OIII] emitting AGN, providing evidence that they are often associated with galaxy mergers and binary AGN, with diverse merger stages and complex kinematics.

Contribution

The paper presents deep imaging and spectroscopy data of four double-peaked [OIII] AGN, demonstrating their association with mergers and binary AGN, and highlighting the varied merger stages and kinematic features.

Findings

Most sources show signs of recent mergers with tidal tails or complex morphologies.

Spectroscopy reveals disturbed kinematics and counter-rotating gas disks.

Some sources are quiescent in morphology but still show signs of merger activity.

Abstract

Mergers are suspected to be reliable triggers of both starformation and AGN activity. However, the exact timing of this process remains poorly understood. Here, we present deep imaging and long slit spectroscopy data of a sample of four double-peaked [OIII] emitting AGN. These sources are often believed to host binary AGN, or at least be currently undergoing major mergers. The sample presented here either have previous IFU and high resolution imaging data that show double-nuclei in the IR as well as kinematicly and spatially distinct line emitting regions. Two sources have detections of double point sources in either the X-ray or radio. The sources studied are therefore likely binary AGN. The AGN in this sample are luminous, radio-quiet and at low redshift. The $u/r/z$ imaging data show host galaxies in a wide range of merger stages, with the majority (3/4) showing tidal tails or complex kinematics and morphologies clearly indicating a recent merger. One source however -hosting a double X-ray source- shows quiescent morphologies with no clear signs of interaction from imaging data. The spectroscopy in this case reveals a gas disk counter-rotating with respect to the stellar component. Spectroscopy of the other sources reveal disturbed kinematics further confirming their status as ongoing mergers. Our data show that AGN triggering in mergers may happen over a wide time span and that sinking of black holes to the center of a merged system might take considerable time in some cases. A detailed analysis will be published in an upcoming paper. Further studies of AGN in merging galaxies will show how the hosts of those AGN differ from normal mergers without AGN activity.