MIGHTEE-H i: H i galaxy properties in the large-scale structure environment at z ∼ 0.37 from a stacking experiment.

We present the first measurement of H i mass of star-forming galaxies in different large scale structure environments from a blind survey at z ∼ 0.37. In particular, we carry out a spectral line stacking analysis considering 2875 spectra of colour-selected star-forming galaxies undetected in H i at 0.23 < z < 0.49 in the COSMOS field, extracted from the MIGHTEE-H i Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies belonging to different subsamples depending on three different definitions of large-scale structure environment: local galaxy overdensity, position inside the host dark matter halo (central, satellite, or isolated), and cosmic web type (field, filament, or knot). We first stack the full star-forming galaxy sample and find a robust H i detection yielding an average galaxy H i mass of |$M_{\rm H \, {\small I}}=(8.12\pm 0.75)\times 10^9\, {\rm M}_\odot$| at ∼11.8σ. Next, we investigate the different subsamples finding a negligible difference in M _{H i} as a function of the galaxy overdensity. We report an H i excess compared to the full sample in satellite galaxies (M _{H i}  = (11.31 ± 1.22) × 10⁹, at ∼10.2σ) and in filaments (M _{H i}  = (11.62 ± 0.90) × 10⁹. Conversely, we report non-detections for the central and knot galaxies subsamples, which appear to be H i -deficient. We find the same qualitative results also when stacking in units of H i fraction (f _{H i} ). We conclude that the H i amount in star-forming galaxies at the studied redshifts correlates with the large-scale structure environment. [ABSTRACT FROM AUTHOR]