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Gas Clumping in the Outskirts of Galaxy Clusters as seen by STAR-X

Presentation #112.02 in the session STAR-X.

Published onJul 01, 2023
Gas Clumping in the Outskirts of Galaxy Clusters as seen by STAR-X

In the outskirts of galaxy clusters, entropy profiles measured from X-ray observations of the hot intracluster medium (ICM) drop off unexpectedly. One possible explanation for this effect is gas clumping, where pockets of cooler and denser structures within the ICM could bias temperature and density estimates. Currently, sufficiently sensitive observatories are unable to directly detect these hypothetical gas clumps. In part to address this possibility, the STAR-X observatory was proposed to the 2021 Mid-Sized Explorer Class Mission (MIDEX) call by NASA. Due to its low altitude orbit, resulting in a low and stable instrumental background, and its high spatial resolution, STAR-X should be sensitive enough to directly detect and characterize these gas clumps if they do exist. The aim of this work is to simulate observations of clumping in clusters to determine how well STAR-X will be able to detect clumps, as well as what clumping properties reproduce observed entropy profiles. We use yt, pyXSIM, SOXS, and other tools to inject clumps into three-dimensional models derived from actual clusters using their observed thermodynamical profiles from other X-ray missions. Radial temperature and surface brightness profiles are then extracted from mock observations using concentric annuli. We find that in simulated observations for STAR-X, gas clumps with reasonable properties can be successfully identified using wavdetect and masked, eliminating the observed drop in entropy. This demonstrates that STAR-X will be capable of detecting substructure in the outskirts of nearby clusters and that the properties of both the outskirts and the clumps will be revealed.

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