2023A&A...678A.122Z

Context. Past observations and simulations have predicted an increasingly inhomogeneous gas distribution towards the outskirts of galaxy clusters. However, the exact properties of such gas clumping are not yet well known. The outskirts of Abell 133 can benefit from deep X-ray observations, with a 2.4 Ms ultra-deep Chandra exposure, as well as eight archival Suzaku pointings, making it a unique laboratory for studying the clumping of the intracluster medium (ICM).
Aims. We searched for significant clump candidates with the specific aim of identifying ones that could represent genuine ICM inhomogeneity. To further understand how clumping biases the thermodynamic profiles, we compared the measurements including and excluding the clump candidates.
Methods. We jointly analyzed Chandra and Suzaku observations of Abell 133. We selected clump candidates with at least 2σ significance based on the Chandra image and we discussed their origins further, using information from the DESI Legacy Imaging Surveys cluster catalog as well as the CFHT r-band image. We performed multiple rounds of Suzaku spectral analysis with different corrections for the underlying point sources and clump distribution and we compared the resulting thermodynamic profiles.
Results. We detected 16 clump candidates using Chandra, most of which are identified as background clusters or galaxies - as opposed to intrinsic inhomogeneity. Even after the correction of the resolved clumps, the entropy profile approaching the outskirts still flattens, deviating from the power law model expected from self-similar evolution, which implies that unresolved clumping and other complex physics contribute to the entropy flattening in the outskirts.