Radio emission at the centre of the galaxy cluster Abell 3560: evidence for core sloshing?

Abstract

Context. We study the interplay between the radio emission associated with the dominant galaxy in clusters and the properties of the surrounding intracluster medium on the basis of its X-ray emission. Aims. Previous radio observations of the galaxy cluster A 3560, located in the Shapley Concentration core, revealed complex radio emission associated with the brightest cluster member. To understand the origin of this radio emission we performed a detailed multiwavelength study with high-quality proprietary data in the radio and X-ray bands and by means of optical data available in the literature. Methods. We observed the cluster with the Giant Metrewave Radio Telescope, the Very Large Array, and the Australia Telescope Compact array at 240 and 610 MHz, 1.28, 1.4, 2.3, 4.8, and 8.4 GHz, and performed a detailed morphological and spectral study of the radio emission associated with the brightest cluster galaxy (BCG). Furthermore, we observed the cluster with the XMM-Newton and Chandra observatories to derive the properties of the intracluster gas. Finally, we made use of literature data to obtain the bidimensional distribution of the galaxies in the cluster. Results. The radio emission, associated with the north-eastern nucleus of the dumb-bell BCG, is the result of two components: an active radio galaxy, with jets and lobes, plus aged diffuse emission, which is not refurbished with new electrons at present. Our Chandra data show that the radio active nucleus of the BCG has extended X-ray emission, which we classify as a low-luminosity corona. A residual image of the XMM-Newton brightness distribution shows a spiral-like feature, which we interpret as the signature of gas sloshing. A sub-group is clearly visible in the surface brightness residual map, and this is also supported by the XMM-Newton temperature analysis. The optical bidimensional analysis shows substructure in A 3560. A galaxy clump was detected at the location of the X-ray sub-group, and another group is present south of the cluster core, in the region where the spiral-like feature was detected. The aged part of the radio emission closely follows the spiral pattern of the X-ray residual brightness distribution, while the two active radio lobes are bent in a completely different direction. We conclude that the complex radio emission associated with the cluster BCG is the result of a minor merger event in A 3560. The aged diffuse emission is strongly affected by the sloshing motion in the intracluster gas and most likely bears information on the trajectory of the cluster BCG during the dynamical evolution of the cluster. On the other hand, the bent jets and lobes of the current radio AGN activity may reflect a complex gas velocity field in the innermost cluster regions and/or sloshing-induced oscillations in the motion of the cD galaxy.

Shapley Supercluster Survey: Galaxy evolution from filaments to cluster cores

“…Some new substructures with respect to previous works have been identified in the ShaSS density map such as those associated with A 3560 N from the cluster centre in the direction of A 3558, towards which also the X-ray emission is elongated (Venturi et al 2013). The most important new feature is however the filament connecting the SSCC and the cluster A 3559 as well as the less pronounced overdensity extending from the SSCC towards A 3560.…”

Shapley Supercluster Survey: mapping the filamentary network connecting the clusters

“…9 reveals clear substructure in Abell 3560, with secondary peaks 18 arcmin to the North and 25 arcmin to the West of the cluster centre, which we refer to as A 3560-N and A 3560-W, respectively. The analysis of XMM X-ray imaging of A 3560 by Venturi et al (2013) indicated it to be undergoing a minor merger, with asymmetric emission, a positional shift between the inner and outer isophotes, a spiral-like structure suggestive of gas sloshing, and a sub-group ∼8 NW from the cluster centre, mid-way towards our group A 3560-N. A 3560-N appears centred on a close pair of early-type galaxies (13:32:14.1, -32:49:56). A 3560-W is centred on a bright elliptical (ShaSS 406059814; 13:30:32.8, -33:03:52, cz = 13 976 km s −1 ).…”

Probing the Physics of Mechanical AGN Feedback with Radial Elongations of X-ray Cavities

“…It also implies that the observed difference between type I and II cavities in the cavity elongation with respect to the jet direction is not due to rotation in the ICM. Gas motions in the ICM may shift or bend X-ray cavities (e.g., Fabian et al 2000;Venturi et al 2013;Paterno-Mahler et al 2013), but our result suggests that the kpc-scale rotation in the ICM velocity field is not significant. In other words, the level of turbulence in the inner regions of galaxy clusters may be relatively low, consistent with recent HITOMI observations of the Perseus cluster (Hitomi Collaboration et al 2016).…”