Raining in MKW 3s: a Chandra-MUSE analysis of X-ray cold filaments around 3CR 318.1

TL;DR

This study combines X-ray and optical observations to analyze cold filaments in a galaxy cluster, revealing their excitation mechanisms and origin, and providing insights into the interplay between different gas phases and AGN activity.

Contribution

First combined X-ray and optical analysis of filaments in a cool core cluster using MUSE and Chandra, identifying excitation processes and filament origins.

Findings

Filaments are colder and less metal-rich than surrounding ICM.

Excitation likely due to star formation, shocks, and cooling ICM.

Filaments probably formed from AGN-driven outflows.

Abstract

We present the analysis of X-ray and optical observations of gas filaments observed in the radio source 3CR 318.1, associated with NGC 5920, the Brightest Cluster Galaxy (BCG) of MKW 3s, a nearby cool core galaxy cluster. This work is one of the first X-ray and optical analyses of filaments in cool core clusters carried out using MUSE observations. We aim at identifying the main excitation processes responsible for the emission arising from these filaments. We complemented the optical VLT/MUSE observations, tracing the colder gas phase, with X-ray $\textit{Chandra}$ observations of the hotter highly ionized gas phase. Using the MUSE observations, we studied the emission line intensity ratios along the filaments to constrain the physical processes driving the excitation, and, using the $\textit{Chandra}$ observations, we carried out a spectral analysis of the gas along these filaments. We found a spatial association between the X-ray and optical morphology of these filaments, which are colder and have lower metal abundance than the surrounding intra-cluster medium (ICM), as already seen in other BCGs. Comparing with previous results from the literature for other BCGs, we propose that the excitation process that is most likely responsible for these filaments emission is a combination of star formation and shocks, with a likely contribution from self-ionizing, cooling ICM. Additionally, we conclude that the filaments most likely originated from AGN-driven outflows in the direction of the radio jet.