What are the underlying physical mechansism driving the ejection of matter at nearly the speed of light from the hearts of black holes? Researchers within the extragalactic astrophysics group are leading the charge to understand these mysterious objects.
The galaxy dynamics group at the Jeremiah Horrocks Institute studies the dynamics of galaxies, including the Milky Way, to understand their formation and evolution. Our main approach is using supercomputer simulations to model the cooling of gas inside dark matter halos leading to star formation, and supernovae explosions. One of the key issues we are currently working on is the formation of nuclear star clusters that are often present at the centres of galaxies and their relation to supermassive black holes millions of times more massive than the Sun.
Galaxy evolution and Stellar Populations
The ages and chemical compositions of different populations of stars in galaxies can tell us a great deal about the formation and evolution of galaxies and their various structural components. Spiral galaxies are complex systems with both actively star forming and passive components, including disks, bulges, halos, bars and spiral arms, whereas early-type galaxies [elliptical and lenticular galaxies] generally have lower levels of star formation and are dominated by a single structural component. However, exactly when, and sometimes where, their stars were made is hard to uncover. In most external galaxies we cannot resolve individual stars, but instead we observe the integrated light from various populations of stars. The stellar populations group works to make sense of the information provided by these jumbled stellar populations and to constrain the method of formation of the various galactic components. Stellar databases such as MILES are being developed to increase our understanding of stellar populations in galaxies. Anne Sansom leads the UK membership of the MILES international consortium.
Our collaborations studying large surveys of galaxies (such as the GAMA and H-ATLASconsortia, of which Anne Sansom and Cristina Popescu are members) allow us to probe the conditions of galaxies of different masses, environment, structure and inter-stellar medium properties. These surveys are revealing more diversity of galaxy morphologies and new methods allow us to study their histories.
Observational Cosmology and Quasars
Dr Roger Clowes leads an international team investigating quasars. More specifically the grouping of quasars together to form a large scale structure but also the enviroment surrounding these quasars and the quasar emission
Quasars are the nuclei of galaxies from the early years of the universe. Quasars undergo brief periods of extremely high brightness that make them visible across huge distances. These periods are ‘brief’ in astrophysics terms but actually last 10-100 million years.
One such structure discovered by Dr Clowes is the Huge-LQG. With a characteristic size (volume1/3) ∼ 500 Mpc (present epoch). Whole clusters of galaxies can be 2-3 Mpc across, but LQGs can be 200 Mpc or more across.
The Interstellar Medium Group led by Prof. Cristina Popescu investigates the formation and evolution of galaxies by studying the detailed physical processes that take place in these complex systems related to the interaction of radiation with dust, gas and cosmic rays