Constraints on circum-galactic media from Sunyaev-Zel'dovich effects and X-ray data

TL;DR

This study combines Sunyaev-Zel'dovich effects and X-ray data to model the circumgalactic medium, revealing a two-phase gas structure with a significant non-thermalized component across different halo masses.

Contribution

It introduces a Bayesian approach to constrain CGM properties, demonstrating that a two-phase model better fits observational data than a single-temperature model.

Findings

A two-phase hot and warm gas model fits the data well.

The hot gas fraction increases with halo mass.

A significant non-thermalized gas component exists in halos.

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 (CGM) for dark matter halos with masses above $10^{12.5}M_{\odot}$. 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 the 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 $10^{12.5}{M}_\odot$ halos to $(40-60)\%$ for $10^{14.5}{M}_\odot$ 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 non-thermalized component with temperature much lower than the virial temperature.