A comprehensive multiwavelength study of the OH megamaser galaxy IRAS 09320+6134

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 disc, observed as a narrow component in the emission-line profiles, with velocity dispersion of $\sigma \le 200$ km s$^{-1}$, and (ii) an outflow, traced by a broad component in the emission-line profiles, with $\sigma \ge 500$ km s$^{-1}$. The disc component is well reproduced by a model of rotation in a plane with similar orientation to that of the large-scale galaxy disc. The outflow component presents bulk velocities of up to $-500$ km s$^{-1}$ and corresponds to a mass outflow rate of $\dot{M}_o=0.122\pm 0.026 M_{\odot }\, \text{yr}^{-1}$. 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 OH megamaser galaxies, this work supports that this phase is linked to the triggering of an AGN, which seems to occur in the final stages of a merger.