MIGHTEE-HI: HI galaxy properties in the large scale structure environment at z~0.37 from a stacking experiment

Abstract

We present the first measurement of HI mass of star-forming galaxies in different large scale structure environments from a blind survey at $z\sim 0.37$. 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 $M_{\mathrm{HI}}=(8.12\pm 0.75)\times 10^9{\mathrm{M}}_{\odot }$ at $\sim 11.8\ddot{I}ƒ$. Next, we investigate the different subsamples finding a negligible difference in $M_{\mathrm{HI}}$ as a function of the galaxy overdensity. We report an HI excess compared to the full sample in satellite galaxies ($M_{\mathrm{HI}}=(11.31\pm 1.22)\times 10^9$, at $\sim 10.2\ddot{I}ƒ$) and in filaments ($M_{\mathrm{HI}}=(11.62\pm 0.90)\times 10^9$. 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 ($f_{\mathrm{HI}}$). We conclude that the HI amount in star-forming galaxies at the studied redshifts correlates with the large scale structure environment.

Accepted for publication in MNRAS. 15 figures, 3 tables