2024ApJ...974..291O

We analyze measurements of the thermal Sunyaev-Zeldovich (tSZ) effect arising in the circumgalactic medium (CGM) of L* galaxies, reported by J. N. Bregman et al. (B+22) and S. Das et al. (D+23). In our analysis, we use the Y. Faerman et al. CGM models, a new power-law model (PLM), and the TNG100 simulation. For a given M_vir, our PLM has four parameters: the fraction, f_hCGM, of the halo baryon mass in hot CGM gas, the ratio, ϕ_T, of the actual gas temperature at the virial radius to the virial temperature, and the power-law indices, a_P,th and a_n for the thermal electron pressure and the hydrogen nucleon density. The B+22 Compton-y profile implies steep electron pressure slopes (a_P,th ≃ 2). For isothermal conditions, the temperature is at least 1.1 × 10⁶ K, with a hot CGM gas mass of up to 3.5 × 10¹¹M_⊙ for a virial mass of 2.75 × 10¹²M_⊙. However, if isothermal, the gas must be expanding out of the halos. An isentropic equation of state is favored for which hydrostatic equilibrium is possible. The B+22 and D+23 results are consistent with each other and with recent (0.5-2 keV) CGM X-ray observations of Milky Way mass systems. For M_vir ≃ 3 × 10¹²M_⊙, the scaled Compton pressure integrals, $E{(z)}^{-2/3}{Y}_{500}/{M}_{\mathrm{vir},12}^{5/3}$, lie in the narrow range, 2.5 × 10^–4-5.0 × 10^–4 kpc², for all three sets of observations. TNG100 underpredicts the tSZ parameters by factors ∼0.5 dex for the L* galaxies, suggesting that the feedback strengths and CGM gas losses are overestimated in the simulated halos at these mass scales.