Galaxy-Scale Jets with New Extragalactic Radio Surveys

Webster, Brendan (2022). Galaxy-Scale Jets with New Extragalactic Radio Surveys. PhD thesis The Open University.



The effects of feedback from high luminosity radio-loud AGN have been extensively researched, but feedback from physically small, low-luminosity radio-loud AGN is less well understood. The advent of high sensitivity, high angular resolution, large field of view telescopes such as LOFAR is now allowing wide-area studies of such faint sources for the first time. Within this thesis I use data from the first release of the LOFAR Two Metre Sky Survey (LoTSS) to report on my discovery of a population of 195 low luminosity radio galaxies where the total extent of the radio emission is no larger than 80 kpc. These objects, which I term galaxy-scale jets (GSJ), are small enough to be directly influencing the evolution of the host on galaxy scales. Combining the LoTSS data with new observations taken with the Karl G. Jansky Very Large Array and the XMM-Newton telescope I report upon the host and radio properties of the sample, finding that GSJ exhibit a mix of FRI and FRII morphologies with host properties that are typical of those found in larger radio galaxies showing that they are ordinary AGN observed at a stage in their life shortly after the radio emission has expanded beyond the central regions of the host. I find that GSJ generally inhabit sparse environments and are primarily young sources that are expanding fast enough to drive shocks. Even ignoring shocks, which I do not detect for any of my sample, I find that approximately half of my GSJ have internal radio lobe energy within an order of magnitude of the ISM energy. For one source studied at X-ray wavelengths I find the radio lobes have a significant proton content suggesting high levels of entrainment. I conclude that GSJ are energetically capable of affecting the evolution of the host.

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