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

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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 $\Gamma = 1.231^{+0.015}_{-0.011}$.