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.