Statistics of thermal gas pressure as a probe of cosmology and galaxy formation

Abstract

The statistics of thermal gas pressure are a new and promising probe of cosmology and astrophysics. The large-scale cross-correlation between galaxies and the thermal Sunyaev-Zeldovich effect gives the bias-weighted mean electron pressure, ⟨bhPe⟩. In this paper, we show that ⟨bhPe⟩ is sensitive to the amplitude of fluctuations in matter density, for example ⟨bhPe⟩∝(σ8Ωm0.81h0.67)3.14 at redshift z=0. We find that at z<0.5 the observed ⟨bhPe⟩ is smaller than that predicted by the state-of-the-art hydrodynamical simulations of galaxy formation, MillenniumTNG, by a factor of 0.93. This can be explained by a lower value of σ8 and Ωm, similar to the so-called “S8 tension” seen in the gravitational lensing effect, although the influence of astrophysics cannot be completely excluded. The difference between and MillenniumTNG at z<2 is small, indicating that the difference in the galaxy formation models used by these simulations has little impact on ⟨bhPe⟩ at this redshift range. At higher z, we find that both simulations are in a modest tension with the existing upper bounds on ⟨bhPe⟩. We also find a significant difference between these simulations there, which we attribute to a larger sensitivity to the galaxy formation models in the high redshift regime. Therefore, more precise measurements of ⟨bhPe⟩ at all redshifts will provide a new test of our understanding of cosmology and galaxy formation. Published by the American Physical Society 2024