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We present the first measurement of HI 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 HI at 0. 23 < z < 0. 49 in the COSMOS field, extracted from the MIGHTEE-HI Early Science datacubes, 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 HI detection yielding an average galaxy HI mass of M ₇₈= (8. 12 0. 75) 10⁹\, M_ at 11. 8. Next, we investigate the different subsamples finding a negligible difference in M ₇₈ as a function of the galaxy overdensity. We report an HI excess compared to the full sample in satellite galaxies (M ₇₈= (11. 311. 22) 10⁹, at 10. 2) and in filaments (M ₇₈= (11. 62 0. 90) 10⁹. Conversely, we report non-detections for the central and knot galaxies subsamples, which appear to be HI-deficient. We find the same qualitative results also when stacking in units of HI fraction (f ₇₈). We conclude that the HI amount in star-forming galaxies at the studied redshifts correlates with the large scale structure environment.
Sinigaglia et al. (Fri,) studied this question.