Uncovering extraplanar gas in UGCA 250 with the Ultra-deep MHONGOOSE Survey

Abstract

ABSTRACT We use the neutral atomic hydrogen (H i) observations of the edge-on galaxy UGCA 250, taken as part of the MeerKAT H i Observations of Nearby Galactic Objects-Observing Southern Emitters (MHONGOOSE) survey to investigate the amount, morphology, and kinematics of extraplanar gas. The combination of high column density sensitivity and high spatial resolution of the survey over a large field of view is ideal for studying the underlying physics governing the extraplanar gas. These data reveal nine additional detections within the field of view along with UGCA 250, with eight of them being within $\sim$200 km s$^{-1}$ of the galaxy’s systemic velocity. The galaxy seems to have a tail-like feature extending away from it in the southern direction up to $\sim$41 kpc (in projection). We also detect a cloud at anomalous velocities, but we did not find any optical counterpart. We construct a detailed tilted ring model for this edge-on galaxy to gain a deeper understanding of the vertical structure of its neutral hydrogen. The model that best matches the data features a thick disc with a scale height of $\sim$3$\pm$1 kpc and an H i mass of about 15 per cent of the total H i mass. This extraplanar gas is detected for the first time in UGCA 250. Our analysis favours a mixed origin for the extraplanar gas in UGCA 250, likely arising from a combination of internal stellar feedback and external tidal interactions.