Abstract
Low frequency radio observations of galaxy clusters are a useful probe of the non-thermal intracluster medium (ICM), through observations of diffuse radio emission such as radio halos and relics. Current formation theories cannot fully account for some of the observed properties of this emission. In this study, we focus on the development of interferometric techniques for extracting extended, faint diffuse emissions in the presence of bright, compact sources in wide-field and broadband continuum imaging data. We aim to apply these techniques to the study of radio halos, relics and radio mini-halos using a uniformly selected and complete sample of galaxy clusters selected via the Sunyaev-Zel’dovich (SZ) effect by the Atacama Cosmology Telescope (ACT) project, and its polarimetric extension (ACTPol). We use the upgraded Giant Metrewave Radio Telescope (uGMRT) for targeted radio observations of a sample of 40 clusters. We present an overview of our sample, confirm the detection of a radio halo in ACT−CL J0034.4+0225, and compare the narrowband and wideband analysis results for this cluster. Due to the complexity of the ACT−CL J0034.4+0225 field, we use three pipelines to process the wideband data. We conclude that the experimental spam wideband pipeline produces the best results for this particular field. However, due to the severe artefacts in the field, further analysis is required to improve the image quality.
Highlights
Non-thermal diffuse emission in galaxy clusters was first discovered in the Coma cluster [1,2,3]
The sensitivity of new generation telescopes has allowed for the study of diffuse emission in previously unexplored parameter spaces
We presented an overview of an SZ-selected ACT’s Polarimetric extension (ACTPol) sample of 40 clusters that spans a wide mass (4.5 < 1014 M < 10.5) and redshift range (0.15 < z < 1.0)
Summary
Non-thermal diffuse emission in galaxy clusters was first discovered in the Coma cluster [1,2,3]. In the mechanism of first-order diffusive shock acceleration (DSA; [36,37]), cosmic-ray protons and electrons are assumed to be accelerated from the thermal pool up to relativistic energies at the cluster merger shocks. This mechanism can explain the general properties of relic emission, several observational features remain unexplained [35], such as the nondetection of gamma rays in clusters that host RRs [11] and the low Mach numbers observed in shocks [22]. For our radio spectral index calculations, we assume Sν ∝ ν−α, where Sν is the flux density at frequency ν and α is the spectral index
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