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

The thermal Sunyaev-Zeldovich effect contains information about the thermal history of the Universe, which is 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, by 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, and 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), which is 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) with high accuracy, validating and confirming the results of previous papers. At higher redshifts (z greater than or similar to 2), there is significant disagreement between by from the halo model and the simulation.