Taking galactic archaeology beyond the near field

My proposed research programme will address two fundamental questions in astrophysics: how do galaxies evolve and what is the nature of the ubiquitous yet invisible substance known as dark matter? We know that galaxies began as tiny quantum fluctuations in the early Universe, which then expanded with inflation to produce local overdensities in dark matter. These clumps attracted gas, which condensed to form the first stars. As these stars clustered they formed galaxies. What we do not yet know, however, is how these early featureless groups metamorphosed into the diverse range of morphologies that can be observed today. Galaxies in our night sky contain anything from a hundred million to a hundred trillion stars and whilst many are elliptical, or spheroidal in shape, others like our Milky Way resemble a pancake with spiral arms.
The evolution of galaxies has a number of drivers acting on different scales. The interstellar scale includes processes such as star formation, explosions of massive stars, and interactions between stars. On a larger scale, mergers between nearby galaxies serve to reshape the distribution of stars as well as deposit alien stars from satellite galaxies in the outer haloes. The haloes of dark matter that enshroud all galaxies modulate the rate of star formation and merger events. We need to reveal the detailed balance between these drivers of galactic evolution to explain the origin of the present diversity. We also need to examine how dark matter interacts with visible matter in galaxies to place constraints on its origin.
The emerging field of 'galactic archaeology' offers an extremely promising path to answering these questions. It relies on the concept of 'descent with modification' in evolutionary biology, which describes the passing down of traits between generations. All stars fuse new elements in their cores. The most massive stars live short lives, perishing in cataclysmic explosions that expel these elements into the surrounding gas. The gas condenses to form the next generation of stars. Thus, the chemical patterns of stars function as 'stellar DNA', betraying the state of chemical enrichment of the gas at the time and place of birth. Furthermore, the positions and velocities of stars indicate their orbits, which in turn reflect the distribution of dark matter in the galaxy. In the outer haloes of galaxies, the orbits do not change significantly with time, and therefore further fossilize the dynamical properties of the satellite galaxies from which the stars originated.
Thanks to the unprecedented success of recent surveys there has been a revolution in the stellar data available for the Milky Way and other nearby galaxies. I will establish a new research field, carrying out detailed galactic archaeology studies of the Milky Way and extending these to a large number of nearby galaxies. My interdisciplinary background in astrophysics and engineering will uniquely enable me to integrate advanced statistical tools with new state-of-the-art galaxy models, thus enabling me to fit a plethora of data, whilst tackling calibration issues. These tools will have far-reaching implications throughout a number of fields, including astrophysics, engineering, and health sciences, where I have already generated notable impact. My models will describe the distribution of dark matter throughout these galaxies and unlock the role played by star formation, chemical enrichment, interactions between stars, and mergers with nearby galaxies. They will also reveal how these drivers of evolution depends on galaxy morphology, the surrounding dark matter halo, and the distribution of galaxies in the local environment. This will place new and exciting limits on our field's remaining unknowns such as the size of the Universe's smallest galaxies. The project will thus address central questions of astrophysics, whilst in parallel feeding back into the Big Data revolution back on Earth.

The key impact goals of the proposed research programme are:
(1) To develop a new picture of galaxy evolution, revealing the balance between the different multi-scale drivers that have given us the diverse galactic morphologies currently observable.
(2) To reveal the detailed distribution of dark matter throughout the local Universe.
(3) To construct new statistical tools for calibrating datasets and efficient parameter estimation.
(4) To invoke a cultural shift in how Science, Technology, Engineering and Mathematics (STEM) subjects are viewed by students at school and the media, and in particular promote the role of women in these subjects.

The stakeholders that will directly benefit from the knowledge generated by (1) and (2) over the first five years of the Fellowship can be broadly grouped as third/public-sector organizations that include professional bodies such as the Institute of Physics, local astronomical societies, and members of the general public (e.g. school students, amateur astronomers). Educators interested in enriching school/university classes with the most up-to-date research will also benefit from the knowledge generated. (1) and (2) will strengthen the UK's position as a leader in cutting-edge research. Success in (1) and (2) should initiate a positive feedback loop, warranting additional astrophysics funding in the future, indirectly strengthening the UK's research position over the next 10 to 20 years.

UK government departments and private sector companies with a low uptake in sophisticated statistical tools, in particular machine learning technology, should be encouraged to use the tools developed in (3) to make processes more efficient. This could potentially lead to a substantial increase in the effectiveness of public services and policy, and in the economic competitiveness of the private sector over the next 10 to 20 years. Commercial enterprises already using machine learning technology could benefit from embracing new tools and methodologies developed in (3) over the next five to 10 years. These impacts will also increase awareness of the benefit of astrophysical methods in the wider community. This will in turn contribute to the strength of future funding in astrophysics. (4) will improve the uptake of STEM subjects at school and university, in particular by female students, which will indirectly improve the economic competitiveness of the UK and its private sector firms over the next 20 to 30 years. Improving the female uptake of STEM subjects is also an important long-term goal for societal progress, with benefits over a similar timescale.