The large-scale radio continuum environment of the prototypical binary active galactic nucleus system, NGC 6240

Dissertation (MSc (Physics))--University of Pretoria, 2022.

Diffuse radio sources are best studied at low radio frequencies (<~ 1 GHz) as they typically have steep radio spectra, resulting in higher flux densities at lower frequencies. However, this requires high surface brightness sensitivity, which is challenging at low frequencies due to a variety of instrumental and propagation effects. Two diffuse radio sources of interest are radio halos and relics, which are typically found in the vicinity of galaxy clusters. The origin of radio halos have been historically debated between the following models: hadronic (secondary electron) and turbulent re-acceleration models, whereas that of radio relics is believed to arise from outgoing merger shocks. Due to the exceptional sensitivity of MeerKAT, we are able to explore diffuse radio sources with high fidelity. In this thesis we report the discovery of the extended diffuse radio continuum around NGC 6240 at redshift of z = 0.0245 using MeerKAT data at 1.28 GHz. We discuss the morphology, location, and linear size of the extended diffuse continuum, however, due to technical issues, we could not classify the nature of the extended diffuse emission. We detect what we argue to be a radio shock with an arc-like morphology with a radio power of 6.3 * 10^22 W/Hz at 1.28 GHz. Our results show that even in low mass systems, MeerKAT is capable of detecting radio relic-like components. The combined analysis of this extended radio continuum halo together with that of the HI, cold molecular gas, and ionized gas will lead to a more holistic understanding of NGC 6240.

SARAO Postgraduate bursary

Physics

MSc (Physics)

Unrestricted