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arXiv · 2504.16178

A JVLA, GMRT, and XMM study of Abell 795: Large-scale sloshing and a candidate radio phoenix

N. Rotella·F. Ubertosi·M. Gitti·M. Rossetti·F. Gastaldello·G. W. Pratt·F. Brighenti·E. Torresi·P. Grandi
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Abstract

We present a multiwavelength analysis of the galaxy cluster Abell 795 (z=0.1374), known for its extended (200 kpc) radio emission with a steep spectral index of unclear origin surrounding the brightest cluster galaxy (BCG), and for sloshing features observed by Chandra. We used new JVLA 1.5 GHz, archival GMRT 325 MHz, and XMM-Newton data to investigate the nature of the radio emission and the dynamical state of the intracluster medium. Our X-ray surface brightness analysis revealed an azimuthally asymmetric excess extending to 650 kpc from the center, possibly related to the sloshing spiral, although the existing data did not allow us to confirm the presence of a cold front. We also detected a previously unknown galaxy group located 1 Mpc northwest of the cluster. Its X-ray emission was well fitted by a $β$-model ($β$=0.52$\pm$0.17), and the spectral analysis revealed a thermal plasma temperature kT=1.08$\pm$0.08 keV and metallicity Z=0.13$\pm$0.06 Z$_{\odot}$. We investigated the possibility that this group acted as the perturber that triggered the sloshing in Abell 795, and we showed that the velocity distribution of member galaxies supports the dynamically unrelaxed nature of Abell 795. The analysis of JVLA 1.5 GHz and GMRT 325 MHz images confirmed the presence of extended radio emission with largest linear size 200 kpc, preferentially extended toward southwest and terminating in a sub-component ("SW blob"). We measured the spectral indices, finding $α_{Ext}$=-2.24$\pm$0.13 for the diffuse extended emission, and $α_{SWb}$=-2.10$\pm$0.13 for the SW blob. These ultra-steep spectral index values, coupled with the complex morphology and cospatiality with the radio-loud AGN present in the BCG, suggest that this emission could be classified as a radio phoenix, possibly arising from adiabatic compression of an ancient AGN radio lobe due to the presence of sloshing motions.

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N. Rotella, F. Ubertosi, M. Gitti, M. Rossetti, F. Gastaldello, G. W. Pratt, F. Brighenti, E. Torresi, P. Grandi. 2025-04-22. A JVLA, GMRT, and XMM study of Abell 795: Large-scale sloshing and a candidate radio phoenix. https://arxiv.org/abs/2504.16178

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