Radio emission is a powerful proxy to study the impact of active supermassive black holes residing in the centre of massive galaxies. The Fanaroff-Riley classification, established in 1974, separates radio-loud active galactic nuclei (AGN) in two categories: sources either presenting a flaring double-jet (FRI, see Figure, left) or a collimated double-jet ending with two clearly identified hot-spots (point of jet injection in the intergalactic medium, FRII, see Figure, right). The origin of these two morphologies is not yet fully understood (galaxy environment, black hole and/or accretion properties), but they present a dependence on luminosity, where FRI galaxies are on average weaker than their FRII counterparts. Yet this radio emission is thought to be an extremely efficient way to redistribute energy in the galaxy and its vicinity, a process which is essential in galaxy evolution simulations to reproduce observations.
We propose in this project to identify and classify radio sources of different sizes and luminosities, making use of newly available low-frequency surveys such as GLEAM and TGSS. These two new all-sky surveys present observations at a common frequency of 150MHz each with a unique, but complementary, advantage, the resolution aspect for TGSS (25′′ vs 3′ for GLEAM) and the frequency coverage for GLEAM (70-230MHz vs 150MHz for TGSS). While TGSS is essential to measure size of the source, GLEAM provides the unique spectral index information, enabling characterisation of the radio emission. By characterising the fraction, the nature and size of sources presenting multiple components at higher resolution, we aim to develop new criteria to characterise radio source in the size/spectral/luminosity plane.
This project is a part of a broader project looking to make use of radio morphology to look at radio sources in a cosmological context, making use of their size as a prior to estimate their redshift (in collaboration with researchers in France and Tasmania).
Dr Nick Seymour
Senior LecturerRead More