# Possible non-thermal nature of the soft-excess emission in the cluster of galaxies Sersic 159-03

## TL;DR

This study analyzes Suzaku and XMM-Newton data of galaxy cluster Sersic 159-03, revealing a soft X-ray excess likely of non-thermal origin, with spatial distribution inconsistent with thermal models or intercluster filaments.

## Contribution

It provides evidence supporting a non-thermal explanation for the soft excess emission in Sersic 159-03, challenging thermal models and previous assumptions.

## Key findings

- Soft excess confirmed by Suzaku but no redshifted OVII lines detected.
- Spatial distribution peaks at the central galaxy, inconsistent with filament models.
- Data favor a non-thermal origin, possibly from relativistic electrons accelerated by shocks.

## Abstract

We present an analysis of new Suzaku data and archival data from XMM-Newton of the cluster of galaxies Sersic 159-03, which has a strong soft X-ray excess emission component. The Suzaku observation confirms the presence of the soft excess emission, but it does not confirm the presence of redshifted OVII lines in the cluster. Radial profiles and 2D maps derived from XMM-Newton observations show that the soft excess emission has a strong peak at the position of the central cD galaxy and the maps do not show any significant azimuthal variations. Although the soft excess emission can be fitted equally well with both thermal and non-thermal models, its spatial distribution is neither consistent with the models of intercluster warm-hot filaments, nor with models of clumpy warm intracluster gas associated with infalling groups. Using the data obtained by the XMM-Newton Reflection Grating Spectrometers we do not confirm the presence of the warm gas in the cluster centre with the expected properties assuming the soft excess is of thermal origin. The observed properties of the soft excess emission are consistent with the non-thermal interpretation. While the high density of relativistic electrons associated with the peak of the soft emission in the cluster centre might have been provided by an active galactic nucleus in the central cD galaxy, the underlying population might have been accelerated in diffuse shocks.