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

Abstract

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 Mvir, our PLM has four parameters: the fraction, fhCGM, of the halo baryon mass in hot CGM gas, the ratio, ϕT, of the actual gas temperature at the virial radius to the virial temperature, and the power-law indices, aP,th and an for the thermal electron pressure and the hydrogen nucleon density. The B+22 Compton-y profile implies steep electron pressure slopes (aP,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 Mvir ≃ 3 × 1012M⊙, the scaled Compton pressure integrals, , 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.