A Sample of 459 Galaxy Groups Identified from the FAST All Sky HI Survey DR2

Groups of HI-rich galaxies are key laboratories for understanding galaxy evolution and environmental effects, constructing samples of such groups is fundamental for relevant studies. Using the FAST All Sky HI Survey (FASHI) Data Release 2 (DR2), currently the largest and deepest HI catalog available, we identify galaxy groups directly from HI signals, without relying on optical pre-selection. A group-finding algorithm with a density contrast criterion and a minimum membership of five yields a catalog of 459 galaxy groups containing 3015 HI sources. Using archival spectroscopic data, we identify optical counterparts and derive total stellar masses of member galaxies as a proxy for the group total mass. The group redshift distribution peaks at z 0.02, and the total HI mass peaks at 10 10 M. We find a significant positive correlation between total HI mass and total stellar mass, consistent with the increase in HI mass with halo mass reported in previous stacking studies. The ratio of total HI mass to total stellar mass decreases significantly with increasing total stellar mass, indicating gradual HI depletion in groups. Our sample provides rich targets for future studies of galaxy evolution and large-scale structure in the local Universe.