Properties of the ionized CGM and IGM: a comparison of galaxy formation models via the Sunyaev-Zel'dovich effect

TL;DR

This study compares the physical properties of ionized gas in the CGM and IGM at z~0 between observations from the Sunyaev-Zel'dovich effect and four cosmological simulations, revealing discrepancies and proposing a new profile model.

Contribution

It introduces a new mass-dependent model for gas pressure and electron density profiles that better fit simulation data compared to the generalized NFW profile.

Findings

Simulations predict over half the baryons are displaced from haloes.

Observed gas fraction aligns with cosmic baryon fraction across halo masses.

Gas temperature from SZE is lower than simulation and X-ray estimates.

Abstract

We present a comparison of the physical properties of the ionized gas in the circumgalactic (CGM) and intergalactic (IGM) media at $z\sim0$ between observations and four cosmological hydrodynamical simulations: Illustris, TNG300 of the IllustrisTNG project, EAGLE, and one of the Magneticum simulations. For the observational data, we use the gas properties that are inferred from cross-correlating the Sunyaev-Zel'dovich effect (SZE) from the {\it Planck} CMB maps with the haloes and the large-scale structure reconstructed from Sloan Digital Sky Survey data. Both the observational and simulation results indicate that the integrated gas pressure in haloes deviates from the self-similar case, showing that feedback impacts haloes with $M_{500}\sim 10^{12-13}\,{\rm M_\odot}$. The simulations predict that more than half the baryons are displaced from haloes, while the gas fraction inferred from our observational data roughly equals the cosmic baryon fraction throughout the $M_{500}\sim 10^{12-14.5}\,{\rm M_\odot}$ halo mass range. All simulations tested here predict that the mean gas temperature in haloes is about the virial temperature, while that inferred from the SZE is up to one order of magnitude lower than that from the simulations (and also from X-ray observations). While a remarkable agreement is found for the average properties of the IGM between the observation and some simulations, we show that their dependence on the large-scale tidal field can break the degeneracy between models that show similar predictions otherwise. Finally, we show that the gas pressure and the electron density profiles from simulations are not well described by a generalized NFW (GNFW) profile. Instead, we present a new model with a mass-dependent shape that fits the profiles accurately.