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

We present MeerKAT HI observations of galaxies in the nearby Virgo III filament. At a median distance of about30 Mpc, the filament extends over about16 Mpc across about56 deg squared. Our survey comprises 15 targeted MeerKAT pointings centred on HI deficient galaxies. Multi-resolution HI imaging at 8-90 arcsec with an rms of about0.3 mJy beam-1 reaches column densities of about4 times10 20 to about4 times10 18 atoms cm-2. This probes HI in galaxy discs at about1.2 kpc resolution and their outskirts at about13.5 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, about40 per cent of galaxies not selected for HI deficiency fall more than 1σ 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.