Merger remnant in TXS 1033+026 - I: $\rm Hα$ and HI 21-cm observations suggest counter-rotating gas

Abstract

We have conducted eMERLIN and GEMINI IFU observations towards TXS 1033+026, a post-merger ultraluminous infrared galaxy, to study the radio continuum, $\rm Hα$ and HI 21-cm lines at sub-kpc scales. We find a symmetric, two-sided core-jet structure in both L ($\approx 1.4$ GHz)- and C ($\approx 4.8$ GHz)-band continuum images. The AGN likely has a double-double radio morphology, indicating possible multiple episodes of activity. The GEMINI IFU observations provided sub-arcsecond resolution. Results from these observations suggest the presence of a kiloparsec-scale circumnuclear $\rm Hα$ disk that rotates around the core and shows signs of a warp. The HI 21-cm maps reveal a complex kinematic structure, with indications of two counter-rotating gas components orbiting the core-jet axis; one of these components counter-rotates relative to the kiloparsec-scale $\rm Hα$ disk. However, the true morphology of this structure may be more complex than our interpretation suggests. We estimate a HI 21-cm velocity-integrated optical depth of $\rm 90 \pm 3 \ km \ s^{-1}$. We note that these are the first results to probe $\rm Hα$ and cold neutral hydrogen gas in TXS 1033+026 at sub-kpc scales.