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, $⟨b_{\mathrm{h}}{P}_e⟩$. In this paper, we show that $⟨b_{\mathrm{h}}{P}_e⟩$ is sensitive to the amplitude of fluctuations in matter density, for example $⟨b_{\mathrm{h}}{P}_e⟩\propto {\left({\sigma }_8{\Omega }_{\mathrm{m}}^{0.81}{h}^{0.67}\right)}^{3.14}$ at redshift $z=0$. We find that at $z<0.5$ the observed $⟨b_{\mathrm{h}}{P}_e⟩$ 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 ${\Omega }_{\mathrm{m}}$, 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 $⟨b_{\mathrm{h}}{P}_e⟩$ at this redshift range. At higher $z$, we find that both simulations are in a modest tension with the existing upper bounds on $⟨b_{\mathrm{h}}{P}_e⟩$. 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 $⟨b_{\mathrm{h}}{P}_e⟩$ at all redshifts will provide a new test of our understanding of cosmology and galaxy formation.

16 pages, 10 figures