Merger remnant in TXS 1033+026 - I: H alpha and HI 21-cm observations suggest counter-rotating gas

We have conducted eMERLIN and GEMINI IFU observations towards TXS 1033+026, a post-merger ultraluminous infrared galaxy, to study the radio continuum, Hα and HI 21-cm lines at sub-kpc scales. We find a symmetric, two-sided core-jet structure in both L (about 1.4 GHz)- and C (about 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 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 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 90 plus or minus 3 km s-1. We note that these are the first results to probe Hα and cold neutral hydrogen gas in TXS 1033+026 at sub-kpc scales.