# X-ray - cosmic shear cross-correlations: first detection and constraints on baryonic effects

**Authors:** Tassia Ferreira, David Alonso, Carlos Garcia-Garcia, Nora Elisa Chisari  
**arXiv:** [2309.11129](https://arxiv.org/abs/2309.11129)  
**Date:** 2023-09-20  
**Summary page:** https://www.summarizepaper.com/en/paper/2309.11129v1/

## Key points

- Researchers made a groundbreaking discovery by detecting the cross-correlation between cosmic shear and the diffuse X-ray background.
- The detection was achieved with an extremely high significance level of $25\sigma$ using data from the Dark Energy Survey and the ROSAT satellite.
- The cross-correlation signal observed in this study is sensitive to the distribution of gas surrounding dark matter haloes.
- Constraints on important physical parameters that determine the impact of baryonic effects in the matter power spectrum were placed through analysis of this signal.
- The researchers determined that half of the gas content on average is expelled from haloes with a mass of $\log_{10}(M_c/M_\odot)=13.643^{+0.081}_{-0.12}$.
- The polytropic index of the gas was also determined to be $\Gamma = 1.231^{+0.015}_{-0.011}$.
- This discovery represents a significant step forward in our understanding of cosmology and physics related to intergalactic gas.
- X-ray cross-correlations can be directly utilized to obtain improved constraints on fundamental aspects of our universe.
- Implications are far-reaching and have potential applications in various fields related to astrophysics and cosmology.
- Further studies building upon these findings could provide deeper insights into dark matter structures, baryonic effects, cosmic shear, and its connection to X-ray background radiation.

## Summary

In a recent study, researchers Tassia Ferreira, David Alonso, Carlos Garcia-Garcia and Nora Elisa Chisari have made a groundbreaking discovery by detecting the cross-correlation between cosmic shear and the diffuse X-ray background. This detection was achieved with an extremely high significance level of $25\sigma$, using data from the Dark Energy Survey and the ROSAT satellite. The cross-correlation signal observed in this study is particularly sensitive to the distribution of gas surrounding dark matter haloes. By analyzing this signal, the researchers were able to place constraints on important physical parameters that determine the impact of baryonic effects in the matter power spectrum. One of the key findings of this study is the determination of the mass of haloes in which feedback has expelled half of their gas content on average. The researchers found this mass to be $\log_{10}(M_c/M_\odot)=13.643^{+0.081}_{-0.12}$. Additionally, they also determined the polytropic index of the gas to be $\Gamma = 1.231^{+0.015}_{-0.011}$. This discovery represents a significant step forward in our understanding of cosmology and physics related to intergalactic gas. It demonstrates for the first time how X-ray cross-correlations can be directly utilized to obtain improved constraints on these fundamental aspects of our universe. The implications are far reaching and have potential applications in various fields related to astrophysics and cosmology. Further studies building upon these findings could provide even deeper insights into dark matter structures and baryonic effects in our universe as well as shed light on other unresolved questions regarding cosmic shear and its connection to X-ray background radiation. Overall, this study opens up new avenues for future investigations into cosmic shear and its correlation with other observable phenomena, paving way for advancements in our understanding of both dark matter structures and baryonic effects in our universe.