Investigating active galactic nuclei with low frequency radio observations

Lazell, Matthew (2015). Investigating active galactic nuclei with low frequency radio observations. University of Birmingham. Ph.D.

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Abstract

Low frequency radio astronomy allows us to observe the fainter and older synchrotron emission from the relativistic plasma associated with active galactic nuclei (AGN) in galaxies and clusters. In this thesis, we use the Giant Metrewave Radio Telescope to explore the impact that AGN have on their surroundings. We present deep, high quality, 150-610 MHz radio observations for a sample of fifteen predominantly cool-core galaxy clusters. For well-known clusters such as MS0735, our low noise images and multi-frequency data enable us to see in improved detail the radio lobes working against the intracluster medium, whilst deriving the energies and timescales of this event.

Our excellent field of view allowed us to explore the point-source like radio AGN for a subsample of our clusters. We used additional optical and infra-red data to identify cluster members, remove radio contamination and investigate the energetics of the many cluster galaxies. We find that low mass radio-loud AGN can easily quench the star formation at their core and compare our observations with the results of cosmological hydrodynamical simulations, to explore the mechanical and binding energy levels over a large range of galaxy masses.

Comparing our sample to published X-ray cavity powers, we find an improved relation from our integrated radio luminosities, allowing a more accurate estimation of jet powers when X-ray or radio observations are unavailable. Our deepest low-frequency radio observations of these well-known clusters will yield valuable information about the nature of feedback when combined with X-ray observations of comparable depth.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):