Suzaku Observation of Abell 1555 and Abell 1558: Searching for Non-thermal Emission from Large Scale Structure Formation

TL;DR

This study uses Suzaku X-ray observations to detect and analyze potential non-thermal emission in galaxy clusters Abell 1555 and Abell 1558, providing insights into structure formation shocks and non-thermal electron populations.

Contribution

First detection of X-ray emission from Abell 1555 and Abell 1558 in the 0.5-7 keV band, with analysis suggesting possible non-thermal components related to structure formation.

Findings

A1555 spectrum fits a thermal plus power-law model.

No significant flux detected in 13-40 keV band.

Non-thermal electron energy fraction consistent with other clusters.

Abstract

We report X-ray observations of two galaxy clusters Abell 1555 and Abell 1558 with Suzaku, which are included in a large scale filamentary structure and a supercluster, to search for non-thermal emission driven by shocks produced in structure formation. These two clusters are detected by Suzaku/XIS for the first time in the X-ray band of 0.5-7 keV. No significant flux is detected by HXD in the energy band of 13-40 keV, and upper limits are reported. From the analysis of the XIS data, we find that the spectrum of A1555 is fit by a thermal plus power-law model, significantly better than a single-temperature pure thermal spectrum. If this power-law component is due to inverse-Compton scattering, the fraction of total baryon energy imparted to non-thermal electrons is consistent with the typical value inferred from the observation of other clusters. However, other scenarios (e.g., under lying AGNs, multi-temperature thermal models) cannot be excluded and further investigation of this system is desired. Basic physical properties of A1555 (e.g., total mass) are also reported.