# Probing hot gas around luminous red galaxies through the Sunyaev-Zel'dovich effect

## TL;DR

This study measures the thermal Sunyaev-Zel'dovich effect around luminous red galaxies using Planck data, revealing the necessity of AGN feedback in models to match observations and emphasizing the role of halo clustering and stellar-to-halo mass relations.

## Contribution

First measurement of tSZ profile around LRGs at these redshifts, comparing observations with hydrodynamical simulations and halo model predictions, highlighting the importance of AGN feedback and halo clustering.

## Key findings

- tSZ emission detected out to ~30 arcmin beyond virial radii
- Models with AGN feedback match the data well
- Halo clustering and stellar-to-halo mass relations are crucial for accurate predictions

## Abstract

We construct the mean thermal Sunyaev-Zel'dovich (tSZ) Comptonization y profile around Luminous Red Galaxies (LRGs) in the redshift range 0.16 < z < 0.47 from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) using the Planck y map. The mean central tSZ signal for the full sample is y ~ 1.8 * 10^(-7) and we detect tSZ emission out to ~30 arcmin, which is well beyond the 10 arcmin angular resolution of the y map and well beyond the virial radii of the LRGs. We compare the measured profile with predictions from the cosmo-OWLS suite of cosmological hydrodynamical simulations. This comparison agrees well for models that include feedback from active galactic nuclei (AGN), but not with hydrodynamic models without this energetic feedback mechanism. This suggests that an additional heating mechanism is required over SNe feedback and star formation to explain the y data profile. We also compare our results with predictions based on the halo model with a universal pressure profile (UPP) giving the y signal. The predicted profile is consistent with the data, but only if we account for the clustering of haloes via a two-halo term and if halo masses are estimated using the mean stellar-to-halo mass (SHM) relation of Coupon et al. (2015) or Wang et al.(2016) estimated from gravitational lensing measurements. We also discuss the importance of scatter in the SHM relation on the model predictions.