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

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, < b(h)P(e)>. In this paper, we show that < b(h)P(e)> is sensitive to the amplitude of fluctuations in matter density, for example < b(h)P(e)> proportional to (sigma(8)Omega(0.81)(m)h(0.67))(3.14) at redshift z=0. We find that at z < 0.5 the observed < b(h)P(e)> 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 sigma(8) and Omega(m), similar to the so-called "S-8 tension" seen in the gravitational lensing effect, although the influence of astrophysics cannot be completely excluded. The difference between Magneticum and MillenniumTNG at z < 2 is small, indicating that the difference in the galaxy formation models used by these simulations has little impact on < b(h)P(e)> at this redshift range. At higher z, we find that both simulations are in a modest tension with the existing upper bounds on < b(h)P(e)>. 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 < b(h)P(e)> at all redshifts will provide a new test of our understanding of cosmology and galaxy formation.