Sunyaev-Zeldovich Signals from \(L^\) Galaxies: Observations, Analytics, and Simulations

• Published in: arXiv.org 2024-08
• Main Authors: Oren, Yossi, Sternberg, Amiel, McKee, Christopher F, Faerman, Yakov, Shy Genel
• Format: Article
• Language: English
• Subjects: Electron pressure; Equations of state; Galactic halos; Galaxies; Gas temperature; Mathematical models; Parameters; Power law; Simulation; Sunyaev-Zeldovich effect
• ISSN: 2331-8422

We analyze measurements of the thermal Sunyaev-Zeldovich (tSZ) effect arising in the circumgalactic medium (CGM) of \(L^*\) galaxies, reported by Bregman et al. 2022 and Das et al. 2023. In our analysis we use the Faerman et al. 2017 and Faerman et al. 2020 CGM models, a new power-law model (PLM), and the TNG100 simulation. For a given \(M_{\rm vir}\), our PLM has four parameters; the fraction, \(f_{\rm hCGM}\), of the halo baryon mass in hot CGM gas, the ratio, \(\phi_T\), of the actual gas temperature at the virial radius to the virial temperature, and the power-law indicies, \(a_{P,{\rm th}}\) and \(a_n\) for the thermal electron pressure and the hydrogen nucleon density. The B+22 Compton-\(y\) profile implies steep electron pressure slopes (\(a_{P,{\rm th}}\simeq 2\)). For isothermal conditions the temperature is at least \(1.1\times 10^6\) K, with a hot CGM gas mass of up to \(3.5\times 10^{11}\) M\(_\odot\) for a virial mass of \(2.75\times 10^{12}\) M\(_\odot\). 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 by Zhang et al. 2024 of Milky Way mass systems. For \(M_{\rm vir}\simeq 3\times 10^{12}\) M\(_\odot\), the scaled Compton pressure integrals, \(E(z)^{-2/3}Y_{500}/M_{\rm vir,12}^{5/3}\), lie in the narrow range, \(2.5\times 10^{-4}\) to \(5.0\times 10^{-4}\) kpc\(^2\), for all three sets of observations. TNG100 underpredicts the tSZ parameters by factors \(\sim 0.5\) dex for the \(L^*\) galaxies, suggesting that the feedback strengths and CGM gas losses are overestimated in the simulated halos at these mass scales.