The first measurement of temperature standard deviation along the line-of-sight in galaxy clusters

TL;DR

This paper introduces the first method to measure temperature variations along the line-of-sight in galaxy clusters, revealing significant inhomogeneity in the Bullet Cluster through multifrequency SZ observations.

Contribution

It presents a novel approach for analyzing the line-of-sight temperature distribution in galaxy clusters using SZ measurements, filling a gap in existing methods.

Findings

Line-of-sight temperature standard deviation in the Bullet Cluster is approximately 10.6 keV.

The temperature distribution along the line-of-sight is highly inhomogeneous.

The method provides new insights into the internal structure of galaxy clusters.

Abstract

Clusters of galaxies are mainly formed by merging of smaller structures, according to the standard cosmological scenario. If the mass of a substructure is >10% of that of a galaxy cluster, the temperature distribution of the intracluster medium (ICM) in a merging cluster becomes inhomogeneous. Various methods have been used to derive the two-dimensional projected temperature distribution of the ICM. However, methods for studying temperature distribution along the line-of-sight through the cluster were absent. In this paper, we present the first measurement of the temperature standard deviation along the line-of-sight, using as a reference case the multifrequency SZ measurements of the Bullet Cluster. We find that the value of the temperature standard deviation is high and equals to (10.6+/-3.8) keV in the Bullet Cluster. This result shows that the temperature distribution in the Bullet Cluster is strongly inhomogeneous along the line-of-sight and provides a new method for studying galaxy clusters in depth.