A combined JVLA, GMRT and XMM study of Abell 795: a candidate radio phoenix?

In the galaxy cluster Abell 795 (z = 0.137), a previous study found extended radio emission surrounding the BCG, using an archival GMRT image at 150 MHz. New JVLA observations at 1.4 GHz (L band) and configuration C were obtained (PI: Ubertosi) to investigate the radio extended emission. In this study, the new dataset was calibrated, analyzed, and a spectral index measurement of the source was obtained by combining the fluxes at 1.4 GHz with those obtained from a GMRT observation at 325 MHz. To perform an accurate investigation of the system properties, a multi-wavelength study was conducted to reveal surface brightness discontinuities in the ICM, utilizing an archival XMM-Newton dataset. A previous work in A795 found signatures of sloshing motion using Chandra data, identifying two cold fronts at distances of approximately 67 kpc and 170 kpc from the center. From the XMM analysis in this study, an asymmetric excess reaching around 650 kpc from the center was identified, following the previously known sloshing spiral. However, no jump in the surface brightness profile was detected, confirming that the excess found cannot be classified as a discontinuity, but its identification supports the geometry of the sloshing. Analysis of JVLA at 1.4 GHz and GMRT at 325 MHz data revealed extended radio emission with dimensions about 170 kpc, along with a sub-component extending in the southwest direction (SW blob). The spectral index values obtained for the two components are: α_Ext. = -2.24 ± 0.13 and α_SWb = -2.10 ± 0.13. These ultra-steep spectral index values, coupled with the complex morphology and co-spatiality with the radio-loud AGN present in the BCG, suggest that this extended emission could be classified as a phoenix. The proposed re-acceleration mechanism involves adiabatic compression of the AGN radio bubble due to the presence of sloshing motion. The potential identification of a phoenix represents one of the few cases reported in the literature.