Testing the SZ-based tomographic approach to the thermal history of the universe with pressure-density cross-correlations: Insights from the Magneticum simulation

TL;DR

This study tests a tomographic method using pressure-density cross-correlations to reconstruct the universe's thermal history, validating it at low redshifts with simulation data and identifying discrepancies at higher redshifts.

Contribution

It validates the SZ-based tomographic approach for probing the universe's thermal history using the Magneticum simulation, confirming its accuracy at low redshifts.

Findings

Method accurately reproduces mean thermal pressure at low redshifts.

Discrepancies observed between halo model and simulation at redshifts above 2.5.

Supports previous findings on the effectiveness of tomographic cross-correlation techniques.

Abstract

The thermal Sunyaev-Zeldovich effect contains information about the thermal history of the universe, observable in maps of the Compton $y$ parameter; however, it does not contain information about the redshift of the sources. Recent papers have utilized a tomographic approach, cross-correlating the Compton $y$ map with the locations of galaxies with known redshift, in order to deproject the signal along the line of sight. In this paper, we test the validity and accuracy of this tomographic approach to probe the thermal history of the universe. We use the state-of-the-art cosmological hydrodynamical simulation, Magneticum, for which the thermal history of the universe is a known quantity. The key ingredient is the Compton-$y$-weighted halo bias, $b_y$, computed from the halo model. We find that, at redshifts currently available, the method reproduces the correct mean thermal pressure (or the density-weighted mean temperature) to high accuracy, validating and confirming the results of previous papers. At higher redshifts ($z\gtrsim 2.5$), there is significant disagreement between $b_y$ from the halo model and the simulation.