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Active Galactic Nuclei PhD Projects

Research projects on offer in our Active Galactic Nuclei group.

X-ray and infrared probes of black hole growth and obscuration

Dr James Aird

Accreting supermassive black holes, powering Active Galactic Nuclei (AGN), can produce radiation across the electromagnetic spectrum. However, obscuring dust often blocks the emission at many wavelengths. X-ray emission, particularly high-energy (i.e. hard) X-rays, can penetrate much of this obscuring material and the emergent X-ray spectrum is left with imprints of the structure and composition of the obscuring material. The obscuring dust is also heated by the incident radiation and re-radiates at mid-infrared wavelengths, providing another powerful tracer of the obscuring dust and the presence of a central, growing black hole. Thus, with deep and wide surveys, X-ray and infrared selection can be used to identify large samples of AGN stretching across cosmic time. However, these samples do not perfectly overlap, with each method appearing to identify distinct and unique AGN populations.

The aim of this PhD project will be to quantify the overlap and uniqueness of X-ray and infrared AGN samples, to determine how this depends on the depth of each of the available datasets, and to generate new tools to robustly quantify supermassive black hole growth across cosmic time. To this end, we will employ a broad range of datasets. This will include some of the new deep observations with the James Webb Space Telescope, which are revealing unexpectedly large populations of infrared-bright AGN that are not found in overlapping deep X-ray data from the Chandra telescope. The student will also have the opportunity to join the international SDSS-V collaboration, exploiting our programme of spectroscopic follow-up of hard X-ray selected AGN and quantifying their infrared properties.

Jet power: Understanding accretion and jet activity in AGN across cosmic history 

Dr Kenneth Duncan and Dr James Aird

One of the key predictions of modern simulations of galaxy evolution is that feedback from accreting black holes (or Active Galactic Nuclei; AGN) plays a crucial role in shaping the growth of galaxies. In particular, AGN that produce extended relativistic jets visible in the radio are believed to be key to shutting down star-formation in the most massive galaxies. However, the details of exactly how the jet activity observed in radio AGN (on kilo- to Megaparsec scales) is linked to the underlying accretion (on sub-parsec scales) has remained elusive, along with the details of how those radio jets impact their host galaxies. The aim of this project is to build a more complete observational picture of the link between AGN jet activity, as observed in the latest generation of radio continuum surveys (LOFAR and MeerKAT), and the underlying super-massive black hole accretion probed by X-rays (eROSITA, Chandra) in unprecedented samples of AGN across cosmic history. Crucially, we will also link this activity to the properties of the galaxies the AGN reside in through the detailed measurements enabled by optical spectroscopy from a new generation of spectroscopic surveys, including the WEAVE-LOFAR and 4MOST/ORCHIDSS spectroscopic surveys (Dr Duncan), and/or the SDSS-V Black Hole Mapper project (Dr Aird). The student will have the opportunity to get hands-on experience in analysis of large observational datasets, and in working in worldwide collaborations. Depending on the student’s interests and experience, there are a number of specific directions the project can take, with potential to focus on different observational regimes (radio/X-ray), or in linking the observations with predictions from the galaxy formation simulations led by the IfA.

 

Under the Galaxy Formation & Evolution projects, see also:

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