# Direct Measurement of the H I-halo Mass Relation through Stacking

DOI:
10.3847/1538-4357/ab886f
Publication date:
01/05/2020
Main author:
Guo, Hong
IAA authors:
Jones, Michael G.
Authors:
Guo, Hong;Jones, Michael G.;Haynes, Martha P.;Fu, Jian
Journal:
The Astrophysical Journal
Refereed:
Yes
Publication type:
Article
Volume:
894
Pages:
92
Abstract:
We present accurate measurements of the total H I mass in dark matter halos of different masses at z ∼ 0, by stacking the H I spectra of entire groups from the Arecibo Fast Legacy ALFA Survey. The halos are selected from the optical galaxy group catalog constructed from the Sloan Digital Sky Survey DR7 Main Galaxy sample, with reliable measurements of halo mass and halo membership. We find that the H I-halo mass relation is not a simple monotonic function, as assumed in several theoretical models. In addition to the dependence of halo mass, the total H I gas mass shows a strong dependence on the halo richness, with larger H I masses in groups with more members at fixed halo masses. Moreover, halos with at least three member galaxies in the group catalog have a sharp decrease of the H I mass, potentially caused by the virial halo shock-heating and the active galactic nucleus (AGN) feedback. The dominant contribution of the H I gas comes from the central galaxies for halos of ${M}_{{\rm{h}}}\lt {10}^{12.5}{h}^{-1}{M}_{\odot }$ , while the satellite galaxies dominate over more massive halos. Our measurements are consistent with a three-phase formation scenario of the H I-rich galaxies. The smooth cold gas accretion is driving the H I mass growth in halos of ${M}_{{\rm{h}}}\lt {10}^{11.8}{h}^{-1}{M}_{\odot }$ , with late-forming halos having more H I accreted. The virial halo shock-heating and AGN feedback will take effect to reduce the H I supply in halos of ${10}^{11.8}{h}^{-1}{M}_{\odot }\lt {M}_{{\rm{h}}}\lt {10}^{13}{h}^{-1}{M}_{\odot }$ . The H I mass in halos more massive than ${10}^{13}{h}^{-1}{M}_{\odot }$ generally grows by mergers, with the dependence on halo richness becoming much weaker.
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