Sunyaev-Zeldovich Signals from L* Galaxies: Observations, Analytics, and Simulations

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 × 10¹¹ M _⊙ for a virial mass of 2.75 × 10¹² M _⊙. 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 × 10¹² M _⊙, the scaled Compton pressure integrals, E ( z ) − 2 / 3 Y 500 / M 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.