Constraining the H I-Halo Mass Relation from Galaxy Clustering

We study the dependence of galaxy clustering on H I mass using similar to 16,000 galaxies with redshift in the range of 0.0025 < z < 0.05 and H I mass of M-H I > 10(8) M-circle dot, drawn from the 70% complete sample of the Arecibo Legacy Fast ALFA survey. We construct subsamples of galaxies with M-H I above different thresholds and make volume-limited clustering measurements in terms of three statistics: the projected two-point correlation function, the projected cross-correlation function with respect to a reference sample, and the redshift-space monopole moment. In contrast to previous studies, which found no/weak H I mass dependence, we find both the clustering amplitudes on scales above a few megaparsecs and the bias factors to increase significantly with increasing H I mass for M-HI > 10(9) M-circle dot. For H I mass thresholds below similar to 10(9) M-circle dot, the inferred galaxy bias factors are systematically lower than the minimum halo bias from mass-selected halo samples. We extend the simple halo model, in which the galaxy content is only determined by halo mass, by including the halo formation time as an additional parameter. A model that puts H I-rich galaxies into halos that formed late can reproduce the clustering measurements reasonably well. We present the implications of our best-fitting model on the correlation of H I mass with halo mass and formation time, as well as the halo occupation distributions and H I mass functions for central and satellite galaxies. These results are compared with the predictions from semianalytic galaxy formation models and hydrodynamic galaxy formation simulations.