Abstracts Physics

The imaging and discovery of M-dwarf debris discs with ALMA

by Patrick Cronin-Coltsmann

Debris discs are an essential piece of planetary system architecture. These exo-asteroid belts and exo-Kuiper belts of stellar systems both comprise that which did not form into planets and are often indelibly marked by that which did. Observing and understanding them is necessary to understanding planetary systems as a whole. M-dwarf debris discs are one of the largest current unknowns within debris disc science. Past surveys have found vanishingly small, if not empty, detection rates among field populations. Only eight discs are currently published in the literature, only four have been resolved, and only the disc of AU Mic has been resolved both thermally and in scattered light. Whether or not M-dwarf discs are significantly less common than the discs of earlier types, or are significantly different in dust properties and planetesimal belt morphology to the discs of earlier types, are unresolved questions. In this thesis I present new resolved ALMA images of two M-dwarf debris discs never before observed at mm-wavelengths or thermally resolved. I also present the first ALMA survey searching for M-dwarf debris discs, identifying two new M-dwarf debris discs and presenting excellent opportunities for follow-up observation. I analyse the newly mm-resolved Fomalhaut C debris disc, now the latest type star to have a resolved debris disc, and find the ring to have a 880