The FLAMINGO Project: Exploring the X-ray–cosmic-shear cross-correlation as a probe of large-scale structure

Abstract Baryonic feedback processes associated with galaxy formation directly influence the large-scale structure by redistributing gas. Recent measurements of the kinetic Sunyaev-Zel’dovich (kSZ) effect and eROSITA stacks of X-ray emission from optically-selected galaxy clusters suggest that feedback from Active Galactic Nuclei (AGN) is more efficient at expelling gas from low-mass clusters than previously thought. The measurement of the cross-correlation between cosmic shear and diffuse X-ray emission provides a new probe of the distribution of gas in groups and clusters. We use the FLAMINGO cosmological, hydrodynamical simulations to examine the X-ray–cosmic-shear cross-correlation. The cross-correlation is most sensitive to the distribution of gas in haloes with masses 1014 ≤ M200c/M⊙ ≤ 1015. It is sensitive to the strength of feedback, but the effects of variations in cosmology and baryonic physics are largely degenerate. We compare the FLAMINGO predictions with the cross-correlation between cosmic shear from the Dark Energy Survey and the ROSAT all-sky X-ray map. We account for AGN that would remain unresolved by ROSAT using either the direct FLAMINGO predictions or by abundance matching to the observed (extrapolated) AGN luminosity function. We find that the fiducial FLAMINGO model is in excellent agreement with the ROSAT–DES-Y3 cross-correlation, while models assuming weaker feedback and models with the significantly stronger feedback suggested by kSZ and eROSITA stacks are both incompatible with the observed X-ray–cosmic-shear cross-correlation.