My name is Peter Boorman, and I'm a postdoc in the NuSTAR group at Caltech in Pasadena, California.
I have a broad range of research interests that mainly revolve around the process of accretion onto compact objects. I dedicate a lot of my time to the growth of supermassive black holes billions of times more massive than our Sun. These black holes reside at the centres of every large galaxy, and I want to know how they grew to the extreme masses we see today.
Key science questions
See the projects below for more information about how I'm trying to solve these questions.
- How many supermassive black holes are actively accreting at different cosmic epochs?
- Are supermassive black holes scaled-up versions of smaller black holes?
- Do supermassive black holes grow by eating material from other galaxies, or themselves?
- How similar are the environments close to accreting supermassive black holes?
Most mass is accreted onto supermassive black holes behind thick veils of obscuring matter, making it difficult to construct a census of supermassive black hole activity. The NuSTAR Local AGN NH Distribution Survey (NuLANDS) is dedicated to finding out how many galaxies in our local cosmic neighbourhood host actively accreting supermassive black holes, on average. Click here to see a poster all about NuLANDS that I presented at the 2021 EAS meeting.
Astrophysical black holes are described by two main parameters, mass and spin. Though many black hole masses have been estimated in a variety of different ways, comparatively fewer black hole spins have been measured to date. We are investigating ways with current and future instrumentation to construct a census of supermassive black hole spin.
Green Pea galaxies are compact starburst dwarf galaxies, analogous to the earliest galaxies that reionised the Universe. The light detected from Green Pea galaxies was thought to be powered by star formation, yet X-ray detectors have found some to be "over-luminous" in X-rays to what is expected from purely star formation. What could be powering such extreme X-ray emission in these sources?
Stellar mass accreting black holes are known to go through cyclic outbursts described by changes in luminosity and spectral hardness, aka accretion states. We are investigating whether or not supermassive black holes exhibit similar accretion states, and what analogies can be made with accreting stellar mass black holes.