Evidence for a merger-revived radio phoenix in MaxBCG J217.95869+13.53470

Abstract

We use XMM-Newton observations of the galaxy cluster MaxBCG J217.95869+13.53470 to analyse its physical properties and dynamical state. MaxBCG J217.95869+13.53470 is found at a redshift of 0.16, has a mass of ∼1 × 10¹⁴ M_⊙ and a luminosity of 7.9 × 10⁴³ erg s^-1. The temperature map shows the presence of hot regions towards the north and west of the brightest cluster galaxy (BCG). From the entropy distribution, regions of high entropy match the location of the hot regions; more high-entropy regions are found to the west, and ∼165 kpc to the southwest of the central active galactic nucleus. A second X-ray bright galaxy is visible ∼90 kpc to the north-east of the BCG, at a redshift of 0.162. This galaxy is likely to be the BCG of a smaller, infalling galaxy cluster. The mass of the smaller cluster is ∼10 per cent the mass of MaxBCG J217.95869+13.53470, yielding an impact parameter of ∼30-100 kpc. We compare the results of our X-ray observations with Giant Metrewave Radio Telescope (GMRT) observations of the radio source VLSS J1431.8+1331, located at the centre of the cluster. Two sources are visible in the radio: a central elongated source that bends at its northern and southern ends, and a south-western source that coincides with a region of high entropy. The radio sources are connected by a bridge of faint radio emission. We speculate that the south-western radio source is a radio relic produced by compression of old radio plasma by a merger shock.