Baryon content and dynamic state of galaxy clusters: XMM-Newton observations of A1095 and A1926

TL;DR

This study uses XMM-Newton observations to analyze the baryon content and dynamic states of galaxy clusters A1095 and A1926, revealing they are young, merging clusters with complex substructures and large-scale environmental influences.

Contribution

First detailed X-ray analysis of the dynamic state and baryon content of optically-selected galaxy clusters A1095 and A1926, identifying them as merging systems with rich substructures.

Findings

Both clusters are dynamically young and undergoing major mergers.

Mass estimates suggest they are gravitationally bound systems.

Additional clusters discovered in the field of A1926.

Abstract

We have initiated a program to study the baryon content and dynamic state of galaxy clusters. Here we present results primarily from XMM-Newton observations of two optically-selected galaxy clusters, A1095 ($z \simeq 0.210$) and A1926 ($z \simeq 0.136$). We find that both of them are actually cluster pairs at similar redshifts. We characterize the temperatures of these individual clusters through X-ray spectral fits and then estimate their gravitational masses. We show a rich set of substructures, including large position offsets between the diffuse X-ray centroids and the brightest galaxies of the clusters, which suggests that they are dynamically young. For both A1095 and A1926, we find that the mass required for the cluster pairs to be bound is smaller than the total gravitational mass. Thus both cluster pairs appear to be ongoing major mergers. Incorporating SDSS and NVSS/FIRST data, we further examine the large-scale structure environment and radio emission of the clusters to probe their origins, which also leads to the discovery of two additional X-ray-emitting clusters ($z \simeq 0.097$ and $z \simeq 0.147$) in the field of A1926. We estimate the hot gas and stellar masses of each cluster, which compared with the expected cosmological baryonic mass fraction, leave ample room for warm gas.