Virgo Filaments VII: MeerKAT HI-imaging of the VirgoIII filament

Abstract

We present MeerKAT HI observations of galaxies in the nearby Virgo III filament. At a median distance of $\sim30$ Mpc, the filament extends over $\approx16$ Mpc across $\sim56$ deg$^2$. Our survey comprises 15 targeted MeerKAT pointings centred on HI deficient galaxies. Multi-resolution HI imaging at 8-90 arcsec with an rms of $\sim0.3$ mJy beam$^{-1}$ reaches column densities of $\sim4\times10^{20}$ to $\sim4\times10^{18}$ atoms cm$^{-2}$. This probes HI in galaxy discs at $\sim1.2$ kpc resolution and their outskirts at $\sim13.5$ kpc. We detect HI emission from 80 sources within the 500-3000 km/s range; most are optically detected galaxies, while 10 per cent lack confirmed counterparts. We also identify three HI clouds without optical counterparts near an interacting system, possibly displaced during the interaction. Galaxies in the filament lie below the field HI gas-fraction scaling relations at fixed stellar mass. Crucially, $\sim40$ per cent of galaxies not selected for HI deficiency fall more than $1\sigma$ below these relations, with an even greater fraction lying under the mean relation itself, indicating that the low HI gas fractions are widespread in the filament rather than confined to the pre-selected deficient population. Quantifying HI morphologies using an asymmetry parameter, we find a wide range of disturbances without a clear trend with projected distance to the filament spine or local density, suggesting a combination of local interactions and the filament itself. This paper presents the survey description, catalogue, and HI atlas enabling investigations of gas removal mechanisms in Virgo III galaxies.