Investigating the scatter origin in CHEX-MATE galaxy cluster X-ray surface brightness profiles

¹ INAF, IASF-Milano, via A. Corti 12, I-20133 Milano, Italy

^* e-mail: iacopo.bartalucci@inaf.it

Published online: 28 March 2024

Abstract

We present the statistical properties and the investigation on the origin of the scatter within the spatially resolved emission measure profiles of the CHEX–MATE sample, formed by 118 galaxy clusters selected via the SZ effect. These objects cover a wide mass, M^YSZ₅₀₀ = [2-15]×10¹⁴M_⊙, and redshift, z=[0.02, 0.6], range. They have been observed by XMM-Newton with a dedicated program that ensures an unprecedented homogeneous and high quality data. We leveraged this exceptional data set by studying the statistical properties of the surface brightness and emission measure radial profiles. We found that there is a critical scale, R~ 0.4R^YSZ₅₀₀, within which the most morphologically relaxed and disturbed object profiles diverge. Above that radius these differences tend to be within 20%.

We complemented the CHEX–MATE clusters with a twin sample drawn from the The Three Hundred suite of cosmological simulations. Leveraging this sample, we were able for the first time to investigate separately the scatter due to projection effects and the one due to cluster-to-cluster differences. We found that projection effects have a smaller impact on the scatter compared to object-to-object differences across all scales. Building on this, we found that below 0.4R^YSZ₅₀₀, the scatter is of the order of 110% reflecting the wide plethora of gas distribution in cluster cores. The scatter is at its minimum, 0.56, in the intermediate range, [0.4-0.8]R^YSZ₅₀₀, despite their morphological status suggesting that clusters are close to the self-similar scenario within this radial range.