Combined emission--absorption studies constrain the spin temperature and phase structure of the neutral atomic hydrogen interstellar medium (ISM). However, these studies have largely been limited to the Milky Way and the Local Group. We extend this technique to galaxies at distances of 7--22,Mpc using deep data from the MeerKAT ̋I Observations of Nearby Galactic Objects -- Observing Southern Emitters (MHONGOOSE) survey and quantify the detection fraction and cold neutral medium (CNM) properties at these distances. We searched for absorption towards 56 background continuum sources in 21 out of the 30 MHONGOOSE galaxies (with nine galaxies lacking suitable background sources) and detected absorption associated with the ̋I discs of the galaxies in three cases: one sightline in NGC 289 and two in NGC 7424. This corresponds to detection rates of 5% (3/56) for the full sample and 10% (3/31) for a clean sub-sample of sightlines when considering only unresolved background sources behind 14 low-inclination galaxies. Detections occur only where both the continuum flux and the foreground ̋I column density are high, with optical-depth sensitivity as the primary limiting factor. For the detected sightlines, we modelled the absorption and emission spectra to derive spin temperatures and CNM fractions using the standard combined emission--absorption method. The CNM spin temperatures and line widths are comparable to Local Group measurements, but the inferred CNM fractions are systematically lower. We argue that this difference is primarily a resolution effect. At the distances of our galaxies, the emission spectra average over several hundred parsecs, diluting structured CNM relative to the smoother warm neutral medium. This demonstrates that emission--absorption analyses can be extended beyond the Local Group, provided that care is taken in constructing representative emission spectra.
Blok et al. (Wed,) studied this question.