A Comprehensive Multiwavelength Study of the OH Megamaser galaxy IRAS 09320+6134

TL;DR

This study investigates the gas dynamics, excitation, and radio properties of the OH megamaser galaxy IRAS 09320+6134, revealing a late-stage merger with AGN-driven outflows and radio emission consistent with a quasar-like nucleus.

Contribution

It provides a detailed multiwavelength analysis of IRAS 09320+6134, linking AGN activity and outflows to the galaxy's late-stage merger status, expanding understanding of OH megamaser galaxy evolution.

Findings

Detection of a rotating gas disk with low velocity dispersion.

Identification of a high-velocity outflow driven by the AGN.

Radio observations reveal a core with quasar-like properties.

Abstract

We present a multiwavelength study of the gas distribution, kinematics and excitation of the OH megamaser galaxy IRAS 09320+6134 (UGC 5101) using Gemini Multi-Object Spectrograph Integral Field Unit, Hubble Space Telescope, and Very Large Array observations. The HST ACS F814W i-band and H$\alpha$ + [N II] $\lambda\lambda$ 6548,84 narrow-band images indicate that this galaxy is a late-stage merger. The ionized gas emission in the inner $\sim$ 2 kpc radius, traced by the GMOS data, is consistent with two kinematic components: (i) a rotating disk, observed as a narrow component in the emission-line profiles, with velocity dispersion of $\sigma$ $\leq$ 200 km s$^{-1}$, and (ii) an outflow, traced by a broad component in the emission-line profiles, with $\sigma\geq$ 500 km s$^{-1}$. The disk component is well reproduced by a model of rotation in a plane with similar orientation to that of the large-scale galaxy disk. The outflow component presents bulk velocities of up to -500 km s$^{-1}$ and corresponds to a mass outflow rate of $\dot{M}_o = 0.122 \pm 0.026 M_{\odot}$ yr$^{-1}$. Emission-line ratio diagrams indicate that the gas excitation is mainly due to an active galactic nucleus, likely the driver of the outflow. The VLA radio image reveals a dominant radio core with two-sided emission along the NE-SW direction. The radio core's spectral index and brightness temperature indicate AGN emission, with the extended emission resembling both in morphology and spectral index the emission observed in radio-quiet quasars. Combined with previous similar studies of other OHM galaxies, the present work supports that this phase is linked to the triggering of an AGN, that seems to occur in the final stages of a merger.