Institute for Astronomy

Active Galactic Nuclei PhD Projects

Research projects on offer in our Active Galactic Nuclei group

The role of radio-AGN in galaxy evolution across cosmic time

Philip Best & Kenneth Duncan

Video: The role of radio-AGN in galaxy evolution across cosmic time
The role of radio-AGN in galaxy evolution across cosmic time

In the nearby Universe, every massive galaxy hosts a supermassive black hole at its centre.  When these black holes accrete matter, they produce active galactic nuclei (AGN). It is now widely believed that the energetic output of AGN plays a critical role in controlling and quenching star formation in their surrounding galaxies. Of particular importance are the radio-AGN, which launch powerful relativistic jets of material. This Ph.D. project aims to address some of the most critical gaps in our knowledge of how these processes work: what processes drive radio-AGN activity?; how exactly does 'AGN feedback' work?; how do these physical processes evolve across cosmic time? These new insights will be possible thanks to the vast samples of radio-AGN being identified in deep radio surveys with LOFAR.

An all-northern-sky survey (LoTSS), reaching an order of magnitude deeper than any previous large-area radio survey, is producing sufficiently large samples of radio-AGN to allow us to separate the correlated effects of stellar mass, black hole mass and environment. Complementing this, the Edinburgh-led LoTSS Deep Fields (in the best-studied regions of the northern sky) provide samples of tens of thousands of radio-AGN out to the peak epoch of activity in the Universe (z~2). Over the next 5 years, dedicated optical spectroscopy will be obtained for all of these radio sources using the new WEAVE spectrograph, as part of the WEAVE-LOFAR survey. The PhD student will play a major role in WEAVE-LOFAR helping to deliver this important survey and leading the interpretation of the results for the radio-AGN samples, to address the critical questions above.

This project can be funded either as a normal UK PhD, or through the new Edinburgh-Leiden joint studentship scheme, where the student would spend 1-2 years of their PhD in Leiden, working under the joint supervision of Huub Rottgering.  Leiden is the lead institute in LOFAR Surveys, and a major partner in WEAVE-LOFAR.

Extreme variability in AGN

Andy Lawrence

Video: Extreme variables in AGN
Extreme variables in AGN

All Active Galactic Nuclei (AGN) are erratically variable to some extent. Light curves can give us information on size scales no other technique can reach. Recently however we have come to realise that a significant minority of AGN undergo dramatic changes - either long slow outbursts over many years, or appearing out of nowhere over days and then fading over months. Possible explanations include accretion instabilities, tidal disruption of stars, and microlensing caused by an intervening object. A new generation of telescopes - especially PanSTARRS, ZTF and soon LSST - are systematically scanning the sky trying to spot such outbursts, and projects such as PESSTO are aimed at getting their spectra  as rapidly as possible. Three projects are possible in this area:

  • Spectra: Joining the PESSTO consortium, collecting and analysing spectra of rapid transients - suspected total disruption events and “changing look” quasars.
  • Data Mining: Collating a database of tens of thousands of AGN, their properties, and their light curves; looking for correlations, and critically testing theoretical predictions.
  • Machine Learning and Forecasting (CDT project): Developing novel algorithms to test whether we can forecast which AGN are about to undergo outburst; using this to get critical pre-outburst spectra.