Radial Profile of the 3.55 keV line out to $R_{200}$ in the Perseus Cluster

TL;DR

This study analyzes the spatial distribution of the 3.55 keV emission line in the Perseus cluster using Suzaku data, providing insights into its potential origin from dark matter decay or astrophysical processes.

Contribution

It offers a detailed radial profile of the 3.55 keV line out to the cluster's $R_{200}$, comparing observations with models for dark matter decay and astrophysical sources.

Findings

Detection of the line in the cluster core but not in outskirts.

Results are consistent with a dark matter decay origin.

Non-detections in outskirts could also suggest astrophysical origins or steeper dark matter profiles.

Abstract

The recent discovery of the unidentified emission line at 3.55 keV in galaxies and clusters has attracted great interest from the community. As the origin of the line remains uncertain, we study the surface brightness distribution of the line in the Perseus cluster since that information can be used to identify its origin. We examine the flux distribution of the 3.55 keV line in the deep Suzaku observations of the Perseus cluster in detail. The 3.55 keV line is observed in three concentric annuli in the central observations, although the observations of the outskirts of the cluster did not reveal such a signal. We establish that these detections and the upper limits from the non-detections are consistent with a dark matter decay origin. However, absence of positive detection in the outskirts is also consistent with some unknown astrophysical origin of the line in the dense gas of the Perseus core, as well as with a dark matter origin with a steeper dependence on mass than the dark matter decay. We also comment on several recently published analyses of the 3.55 keV line.