Gas clumping in the outskirts of galaxy clusters, an assessment of the sensitivity of STAR-X

TL;DR

This paper assesses STAR-X's potential to detect gas clumping in galaxy cluster outskirts through simulations, aiming to clarify the role of clumps in entropy profile anomalies.

Contribution

It demonstrates that STAR-X can effectively detect and characterize gas clumps in cluster outskirts via simulated observations, advancing understanding of ICM substructure.

Findings

STAR-X can detect gas clumps within certain property ranges.

Simulations show successful recovery of true cluster profiles after masking clumps.

STAR-X has the potential to reveal properties of both the ICM outskirts and clumps.

Abstract

In the outskirts of galaxy clusters, entropy profiles measured from X-ray observations of the hot intracluster medium (ICM) drops off unexpectedly. One possible explanation for this effect is gas clumping, where pockets of cooler and denser structures within the ICM are present. Current observatories are unable to directly detect these hypothetical gas clumps. One of the science drivers of the proposed STAR-X observatory is to resolve these or similar structures. Its high spatial resolution, large effective area, and low instrumental background make STAR-X ideal for directly detecting and characterizing clumps and diffuse emission in cluster outskirts. 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. This is achieved by using yt, pyXSIM, SOXS, and other tools to inject ideally modeled clumps into three-dimensional models derived from actual clusters using their observed 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, a parameter space of clump properties exists where gas clumps can be successfully identified using wavdetect and masked, and are able to recover the true cluster profiles. This demonstrates that STAR-X could 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.