Constraints on Circumgalactic Media from Sunyaev–Zel’dovich Effects and X-Ray Data

Abstract

Abstract We use observational measurements of thermal and kinetic Sunyaev–Zel’dovich effects, as well as soft X-ray emission associated with galaxy groups, to constrain the gas density and temperature in the circumgalactic medium for dark matter halos with masses above 1012.5 M ⊙. A number of generic models are used together with a Bayesian scheme to make model inferences. We find that gas with a single temperature component cannot provide a consistent model to match the observational data. A simple two-phase model assuming a hot component and an ionized warm component can accommodate all three observations. The total amount of the gas in individual halos is inferred to be comparable to the universal baryon fraction corresponding to the halo mass. The inferred temperature of the hot component is comparable to the halo virial temperature. The fraction of the hot component increases from (15–40)% for 1012.5 M ⊙ halos to (40–60)% for 1014.5 M ⊙ halos, where the ranges reflect uncertainties in the assumed gas density profile. Our results suggest that a significant fraction of the halo gas is in a nonthermalized component with the temperature much lower than the virial temperature.