An investigation of the diffuse radio emission in the galaxy cluster Abell S1136

Abstract

In this thesis, I have presented my observations of the diffuse radio emission from the galaxy cluster Abell S1136, first observed by Olowin (1988 ) in the Southern Extension to the Abell et al. (1989 ) All-Sky Catalog. These observations were made with the Australian Square Kilometre Array Pathfinder (ASKAP ) telescope, as part of the Early Science program of the Evolutionary Map of the Universe (EMU ) (Norris et al. , 2011 ); a wide-field, radio continuum survey, planned for the Australian Square Kilometre Array Pathfinder (ASKAP ) (Norris et al. , 2011 ). The diffuse emission in the Abell S1136 galaxy cluster, previously identified as a radio halo in surveys with Murchison Wide Field Array (MWA ), appears to extend in a reverse S shape from the Active Galactic Nucleis (AGN s) in the core of the cluster, shown in Figure 4.1 . This emission appears consistent with a Fanaroff-Riley Type I (FRI ) type radio galaxy with a Wide Angle Tail (WAT ). The diffuse emission breaks up into several filamentary structures, which is interpreted as synchrotron emission from shock-excited electrons. I found there is evidence of filamentary structure in three distinct areas of the cluster centre, which I have labelled as: 1. The Northern Filament. 2. The BCG Filament. 3. The Southern Filament. Analysis of radio and X-ray data shows Abell S1136 to be a relaxed cluster that is likely in equilibrium. The X-ray and radio emission was found to be coincident with the centre of the galaxy cluster, located on the BCG ESO 470-20 (Lauberts and Valentijn , 1989 ). The 'northern filament' showed as being a possible radio channel , either punching its way through the hot gas of the Intra-Cluster Medium (ICM ) or being constrained in some way by the ICM . In the analysis presented here, Abell S1136 does not have a cool core. There is a small centroid shift, which indicates the possibility of a slightly disturbed system, and possible interaction between Abell S1136 and PKS 2333-318. The filamentary sub-structure in Abell S1136 is quite unusual, and difficult to interpret in the framework of currently proposed models.

Date of Award	2020
Original language	English