X-Ray-Cosmic-Shear Cross-Correlations: First Detection and Constraints on Baryonic Effects

TL;DR

This paper reports the first high-significance detection of the cross-correlation between cosmic shear and the diffuse X-ray background, providing new constraints on baryonic effects in dark matter haloes.

Contribution

It presents the first measurement of X-ray cosmic shear cross-correlation and constrains baryonic physics parameters affecting the matter power spectrum.

Findings

Halo mass where feedback expels half of the gas: log10(M_c/M_sun)=13.643+/-0.12

Polytropic index of gas: Gamma=1.231+/-0.011

Detection significance: 25 sigma

Abstract

We report a first detection, at very high significance ($25\sigma$), of the cross-correlation between cosmic shear and the diffuse X-ray background, using data from the Dark Energy Survey and the ROSAT satellite. The X-ray cross-correlation signal is sensitive to the distribution of the surrounding gas in dark matter haloes. This allows us to use our measurements to place constraints on key physical parameters that determine the impact of baryonic effects in the matter power spectrum. In particular, we determine the mass of haloes in which feedback has expelled half of their gas content on average to be $\log_{10}(M_c/M_\odot)=13.643^{+0.081}_{-0.12}$, and the polytropic index of the gas to be $\Gamma = 1.231^{+0.015}_{-0.011}$. This represents a first step in the direct use of X-ray cross-correlations to obtain improved constraints on cosmology and the physics of the intergalactic gas.