Star Formation and Quenching of Central Galaxies from Stacked Hi Measurements

We quantitatively investigate the dependence of central galaxy HI mass (M-HI) on the stellar mass (M-*), halo mass (M-h), star formation rate (SFR), and central stellar surface density within 1 kpc (Sigma(1)), taking advantage of the HI spectra stacking technique using both the Arecibo Fast Legacy ALFA Survey and the Sloan Digital Sky Survey. We find that the shapes of MHI-Mh and MHI-M* relations are remarkably similar for both star-forming and quenched galaxies, with massive quenched galaxies having constantly lower HI masses of around 0.6 dex. This similarity strongly suggests that neither halo mass nor stellar mass is the direct cause of quenching, but rather the depletion of the HI reservoir. While the HI reservoir for low-mass galaxies of M-* < 10(10.5) M-circle dot strongly increases with M-h, more massive galaxies show no significant dependence of M-HI with M-h, indicating that the main effect of halo is to determine the smooth cold gas accretion. We find that the star formation and quenching of central galaxies are directly regulated by the available HI reservoir, with an average relation of SFR proportional to M-HI(2.75)/M-*(0.40), implying a quasi-steady state of star formation. We further confirm that galaxies are depleted of their HI reservoir once they drop off the star formation main sequence and there is a very tight and consistent correlation between M-HI and Sigma(1) in this phase, with M-HI proportional to Sigma(-2)(1). This result is consistent with the compaction-triggered quenching scenario, with galaxies going through three evolutionary phases of cold gas accretion, compaction and postcompaction, and quenching.

Automated summary

The study reveals that the HI mass of central galaxies plays a direct role in regulating star formation and quenching, rather than halo mass or stellar mass. Low-mass galaxies show an increase in HI reservoir with increasing halo mass, while more massive galaxies do not show significant dependence on halo mass, with the main effect being the determination of smooth cold gas accretion. The relation between star formation rate and HI mass suggests a quasi-steady state of star formation, with galaxies depleting their HI reservoir once they move away from the star formation main sequence.