Galaxy And Mass Assembly (GAMA): The group H I mass as a function of halo mass

We determine the atomic hydrogen (H I) to halo mass relation (HIHM) using Arecibo Legacy Fast ALFA survey H I data at the location of optically selected groups from the Galaxy And Mass Assembly (GAMA) survey. We make direct H I detections for 37 GAMA groups. Using H I group spectral stacking of 345 groups, we study the group H I content as a function of halo mass across a halo mass range of 10¹¹-10^14.7 M_⊙. We also correct our results for Eddington bias. We find that the group H I mass generally rises as a function of halo mass from 1.3% of the halo mass at $10^{11.6} \, \text{M}_\odot$ to 0.4% at $10^{13.7} \, \text{M}_\odot$ with some indication of flattening towards the high-mass end. Despite the differences in optical survey limits, group catalogues, and halo mass estimation methods, our results are consistent with previous group H I-stacking studies. Our results are also consistent with mock observations from SHARK and IllustrisTNG.