Astrophysics at the University of Bath 2020-2023

Bath astrophysicists study exploding stars, growing galaxies and feeding black holes in an expanding Universe. We propose to combine observations, theory and simulations to tackle a diverse array of problems from high energy and time domain astronomy to the formation of galaxies, their co-evolution with supermassive black holes and cosmology. Advanced statistical methods will aid the interpretation of our observational and computational results. Jointly, our research questions will illuminate the 'dynamic Universe' we live in on the widest range of scales.

On the smallest scales, the high energy phenomena associated with the death of massive stars and the compact remnants they leave behind can be monitored real-time. The emission coming from the immediate surroundings of stellar black holes and neutron stars, and from interactions between them, opens a window on extreme physics that cannot be replicated on Earth. Our group pioneered measurements of polarised light, revealing the importance of magnetic fields in shaping the relativistic jets emerging from these violent events. Physical interpretation of the rich phenomenology observed across the electromagnetic spectrum will be enabled by state-of-the-art simulations capable of predicting so-called light curves, describing the rapid temporal variations as seen at X-ray, optical and radio wavelengths. New compared to previous modelling efforts is that important lessons on jet structure and dynamics will be incorporated, and information from an entirely different probe than light will be tied in, namely gravitational waves. This recent breakthrough in multi-messenger astronomy further allows tests of a scenario in which the incredibly dense crust of neutron stars can violently shatter due to resonances induced by an inspiraling companion. We will devise rigorous predictions of the multi-messenger signatures of such events and the rates at which they are anticipated to be observed, allowing inferences on the extreme nuclear physics at play in these ultradense objects.

Zooming out to galaxy scales, the relevant timescales increase in lockstep. Here too, gamma-ray bursts happening during the final death throes of massive stars play a key role. Since by their sheer brightness they are observable out to large cosmological distances, we can use them as a unique background probe against which to study the cycle between gas, star formation and dust that governs the build up of stars in galaxies. New spatially resolved spectroscopic observations will allow us to meaningfully pair this information with complementary observations of their host galaxies. Similar techniques will underpin a study that pairs observations of the dynamics and morphologies of galaxies to settle a long-standing debate on the connection between fuelling of supermassive black holes at the centres of galaxies and the disruptions induced by the collision between galaxies. Selection biases will be accounted for by jointly analysing observations and advanced cosmological simulations. Similarly pairing brand-new observations with cosmological simulations, we will turn our eyes to the cosmic frontier, mapping the emergence of galaxies in the most overdense structures known in the early Universe during the first 3 billion years of its evolution. Our census of the progenitors to today's galaxy clusters will reveal their importance to early star formation and the impact of environment on galaxy evolution. It will further allow a test of cosmological structure formation theory.

Arriving at the largest possible spatial and temporal scales, the entire cosmos, with its accelerated expansion, is a dynamic system. The precise rate of expansion is a matter of intense debate with different measurement methodologies in apparent contradiction. Our real-time monitoring of variable stars has the potential to resolve this debate or, alternatively, reveal fundamental new physics challenging our standard cosmology.

The University of Bath is one of the leading research-intensive universities in the United Kingdom. The University's institutional research grant portfolio is approximately £130M. Its strong track record of innovation and entrepreneurship has contributed to its ranking as the fifth best university in the UK in the 2018 edition of The Guardian University Guide. Extremely successful for a university of its age, it ranked 7th in the 2016 QS World University Rankings list "Top 50 Under 50". It achieved the Gold TEF award in 2017, and the National Student Survey showed the average overall student satisfaction rate was 88.2% (above the national average of 85%), with the BSc (Hons) Physics with Placement course achieving a 100% score. The University boasts a robust infrastructure to support the development of research and maximise its value and impact.

Within the University, the Astrophysics group is actively engaging with colleagues in physics, mathematics, engineering and computer science to develop interdisciplinary projects enabled by cutting-edge problems in astrophysics. The role of STEM in government and education policy is also of interest.

Impact of Research Outputs on the Scientific Community - The goal of this proposal is to perform fundamental research in astrophysics to address open questions in galaxy evolution, black hole astrophysics and relativistic dynamics. The proposed projects combine a range of novel techniques, world-leading datasets and state-of-the-art computational methods.

Impact of Research Outputs on the Wider Community - More broadly, the proposed research will be used in a range of engagement activities across the University and involving local schools, the local general public and out to wider audiences online and via the national media. Three main avenues for public engagement have been identified and are detailed in the associated Pathways to Impact document. In brief, these will involve a wider engagement initive in the Department of Physics to work with schools in the Bath area, active online and media engagement, and engagement with industrial partners.