Unveiling the interplay between the GASP jellyfish galaxy JO194 and its environment with Chandra

TL;DR

This study analyzes Chandra X-ray observations of the jellyfish galaxy JO194, revealing extended X-ray emission likely caused by the interaction between the galaxy's interstellar medium and the surrounding intracluster medium, independent of star formation.

Contribution

First detailed X-ray analysis of JO194 showing the X-ray emission's origin from ICM-ISM interplay rather than star formation, highlighting persistent conditions for X-ray emission in jellyfish galaxies.

Findings

X-ray emission extends from the stellar disk to spiral arms.

X-ray luminosity exceeds that expected from star formation by a factor of 2-4.

X-ray properties are consistent across different jellyfish galaxies.

Abstract

X-ray studies of jellyfish galaxies opened a window in the physics of the interplay between intracluster medium (ICM) and interstellar medium (ISM). In this paper, we present the study of an archival \textit{Chandra} observation of the GASP jellyfish galaxy JO194. We observe X-ray emission extending from the stellar disk to the unwinding spiral arms with an average temperature of $kT=0.79\pm0.03$ keV. To investigate the origin of the X-ray emission, we compare the observed X-ray luminosities with those expected from the star formation rates (SFR) obtained from H$\alpha$ emission. We estimate an X-ray luminosity excess of a factor $\sim2-4$ with respect to the SF, therefore we conclude that SF is not the main responsible for the extended X-ray emission of JO194. The metallicity in the spiral arms ($Z=0.24^{+0.19}_{-0.12} Z_{\odot}$) is consistent with that of the ICM around JO194 ($Z=0.35\pm0.07$), thus we suggest that the ICM radiative cooling dominates the X-ray emission of the arms. We speculate that the X-ray plasma results from the ISM-ICM interplay, although the nature of this interplay is still mostly unknown. Finally, we observe that the X-ray properties of JO194 are consistent with those of two other GASP galaxies with different stellar mass, phase-space conditions in their hosting clusters, and local ICM conditions. We suggest that the conditions required to induce extended X-ray emission in jellyfish galaxies are established at the beginning of the stripping, and they can persist on long time scales so that galaxies in different clusters and evolutionary stages can present similar extended X-ray emission.