LAUSR

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 function of halo mass across a halo mass range of 1011–1014.7M⊙. 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 1011.6 M⊙ to 0.4 % at 1013.7 M⊙ 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.