CGM2 + CASBaH: The Mass Dependence of H I Lyα-Galaxy Clustering and the Extent of the CGM
Tripp, Todd M.; Prochaska, J. Xavier; Tejos, Nicolas; Lehner, Nicolas; Howk, J. Christopher; Tumlinson, Jason; Burchett, Joseph N.; Werk, Jessica K.; O'Meara, John M.; Tchernyshyov, Kirill; Bordoloi, Rongmon; Wilde, Matthew C.
United States, Japan, Chile
Abstract
We combine data sets from the CGM2 and CASBaH surveys to model a transition point, R cross, between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies at z < 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01-20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover H I Lyα. Our best-fitting model is a two-component model that combines a 3D absorber-galaxy cross-correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination of R cross as a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with 108 ≤ M ⋆/M ⊙ ≤ 1010.5, we find that R cross(M ⋆) ≈ 2.0 ± 0.6R vir. Additionally, we find excellent agreement between R cross(M ⋆) and the theoretically determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution at z < 0.5 that distribute T ≈ 104K gas to distances beyond the virial radius.