CGM$^2$ $+$ CASBaH: The Mass Dependence of H~I Ly$\alpha$-Galaxy Clustering and the Extent of the CGM

• Main Authors: Wilde, Matthew C, Tchernyshyov, Kirill, Werk, Jessica K, Tripp, Todd M, Burchett, Joseph N, Prochaska, J. Xavier, Tejos, Nicolas, Lehner, Nicolas, Bordoloi, Rongmon, O'Meara, John M, Tumlinson, Jason, Howk, J. Christopher
• Format: Journal Article
• Language: English
• Published: 06-01-2023
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2301.02718

We combine datasets from the CGM$^{2}$ and CASBaH surveys to model a
transition point, $R_{\rm cross}$, 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 Ly$\alpha$. Our best-fitting model is
an exclusionary 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 $R_{\rm cross}$
as a function of galaxy stellar mass, which can be interpreted as the boundary
between the CGM and IGM. For galaxies with $10^8 \leq M_{\star}/M_{\odot} \leq
10^{10.5}$, we find that $R_{\rm cross}(M_{\star}) \approx 2 \pm 0.6 R_{\rm
vir}$. Additionally, we find excellent agreement between $R_{\rm
cross}(M_{\star})$ 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 $T \approx 10^{4}$K gas to distances
beyond the virial radius.