Research in Astrophysics at The University of Bristol

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This proposal is for a grant to researchers in astrophysics at the University of Bristol.Much recent cosmology has been based on investigations of galaxy clusters. The first project will make reliable measurements of cluster masses and other parameters. This involves statistically rigorous investigations of cluster samples drawn from X-ray sky surveys - the hot gas in the clusters shines in X-rays. The clusters span a wide mass range and are seen over half the age of the Universe, so we take into account their evolution over time.Massive galaxies within current-day clusters have very old stellar populations. They finished forming their stars in the first few billion years after the big bang, unlike most galaxies outside clusters. Understanding details of their formation is crucial to understanding their nature. Our second project will identify and study galaxies in proto-clusters (progenitors of today's clusters) as they form their stars, building a picture of the inter-related evolution of clusters and their galaxies.A third project explores the physics of matter falling into black holes. It will determine how X-ray observations can reliably measure the black hole mass, spin rate, and geometry of the environment close to the black hole. Galaxies and their central black holes grow together, so reliable measurements of black hole mass and spin rates can test models of galaxy evolution. Observing the close environment of super-massive black holes is both intrinsically interesting, and is a key goal for the next generation of X-ray satellites such as the ESA's Athena observatory.A fourth project looks at how tiny regions in the centres of individual galaxies, near central black holes, affect gas on the large scale - by stopping cooling of the atmospheres of galaxy clusters, and by making the atmospheres more magnetic over time. A feedback process, in which cluster gas is reheated by the ejection of very hot, fast, gas from the regions near black holes is involved, at least in one heating mode. Having identified the sources responsible for this heating, we now want to understand how the process works.The fifth project involves maintenance and improvement of the TOPCAT software, a catalogue and data manipulation tool used world-wide and of great importance to many astronomers in their interactions with data sets of increasing size and complexity and which is now finding creative uses well beyond astronomy. The project will also contribute to the critical international Virtual Observatory framework that enables remote data access for TOPCAT and other software and interoperability between them.A sixth project will use in-hand HST and guaranteed JWST observations of a transiting giant exoplanet to characterise the chemical makeup, dynamics, and evolution through measurements of its atmospheric transmission and emission in unprecedented detail. We will use these observations to develop new data analysis pipelines for JWST to produce the most complete dataset for a single exoplanet atmosphere. Two further projects explore exoplanets from a theoretical perspective. Project seven investigates the nature of the gas/dust disks around young stars in which planets form. As young pieces of planets collide and assemble into larger planets they can destroy one another. Some disks around young stars may show evidence of this destructive side of planet formation. We will carry out computer calculations to interpret extreme examples of dusty disks to see if they evolve through giant impacts between young planets.The final project is a theoretical study into polar vortices in the atmospheres of planets around other stars and how they may affect their habitability. When combined with JWST observations, it will result in a detailed model of the atmosphere of TRAPPIST-1e, an Earth-sized exoplanet orbiting in its star's habitable zone.