Results of the summarizing process for the arXiv paper: 2305.07080v1

Using data from the SRG/eROSITA all-sky survey, a study was conducted to analyze the X-ray surface brightness and gas density profiles of galaxy clusters. The researchers stacked approximately 40 galaxy cluster images in the 0.3-2.3 keV band, covering a radial range of up to 10 times the critical radius ($R_{\rm 500c}$). The analysis revealed that there is excess emission detected beyond $3\times R_{\rm 500c}$, indicating the presence of gas in these regions. Furthermore, the reconstructed density profile obtained from the X-ray surface brightness profile showed good agreement (within about 30%) with the mean gas profile predicted by numerical simulations. These simulations suggest a local gas overdensity of around 20-30 at $3\times R_{\rm 500c}$ and a gas fraction close to $\frac{\Omega_b}{\Omega_m}\approx 0.15$ in the standard $\Lambda$CDM model. Comparing the derived gas density profile with electron pressure profiles based on Sunyaev-Zel'dovich (SZ) measurements, it was observed that beyond $3\times R_{\rm 500c}$, the gas temperature decreases by a factor of approximately 4-5 compared to typical cluster temperatures within $R_{\rm 500c}$. However, despite this decrease in temperature, entropy continues to increase up to this distance. To obtain more precise constraints on gas properties beyond $3\times R_{\rm 500c}$, a larger sample size than what was used in this pilot study is needed. Overall, this study provides valuable insights into the X-ray surface brightness and gas density profiles of galaxy clusters, shedding light on their properties and behavior at large radial distances.

• Study conducted using data from the SRG/eROSITA all-sky survey
• Analyzed X-ray surface brightness and gas density profiles of galaxy clusters
• Stacked approximately 40 galaxy cluster images in the 0.3-2.3 keV band
• Excess emission detected beyond 3 times R_500c, indicating presence of gas in these regions
• Reconstructed density profile showed good agreement with mean gas profile predicted by simulations (within about 30%)
• Simulations suggest local gas overdensity of around 20-30 at 3 times R_500c and gas fraction close to Omega_b/Omega_m ≈ 0.15 in standard ΛCDM model
• Gas temperature decreases by a factor of approximately 4-5 beyond 3 times R_500c compared to typical cluster temperatures within R_500c
• Entropy continues to increase up to this distance despite decrease in temperature
• Larger sample size needed for more precise constraints on gas properties beyond 3 times R_500c

Exploring the X-ray Surface Brightness and Gas Density Profiles of Galaxy Clusters

Galaxy clusters are some of the largest structures in the universe, composed of hundreds to thousands of galaxies bound together by gravity. To better understand their properties and behavior, researchers have conducted a study using data from the SRG/eROSITA all-sky survey to analyze their X-ray surface brightness and gas density profiles. In this article, we will discuss what they found out about these galaxy clusters.

Stacking Images for Analysis

The researchers stacked approximately 40 galaxy cluster images in the 0.3-2.3 keV band, covering a radial range up to 10 times the critical radius ($R_{\rm 500c}$). This allowed them to obtain an average profile that could be used for further analysis.

Excess Emission Detected Beyond $3\times R_{\rm 500c}$

The analysis revealed that there is excess emission detected beyond $3\times R_{\rm 500c}$, indicating the presence of gas in these regions. Furthermore, when comparing the reconstructed density profile obtained from the X-ray surface brightness profile with numerical simulations, it was observed that there is good agreement (within about 30%) between them. The simulations suggest a local gas overdensity of around 20-30 at $3\times R_{\rm 500c}$ and a gas fraction close to $\frac{\Omega_b}{\Omega_m}\approx 0.15$ in standard $\Lambda$CDM model cosmology.

Decrease in Temperature Beyond $R_{500c}$

Comparing electron pressure profiles based on Sunyaev–Zel'dovich (SZ) measurements with those derived from X-rays showed that beyond $ 3 \times R_{500c}$, there is a decrease in temperature by a factor of approximately 4–5 compared to typical cluster temperatures within $R_{500c}$. Despite this decrease in temperature however, entropy continues to increase up to this distance as well.