dc.contributor.author Boneberg, Dominika Maria Rita dc.date.accessioned 2018-06-29T11:32:49Z dc.date.available 2018-06-29T11:32:49Z dc.date.issued 2018-07-21 dc.date.submitted 2018-03-29 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/277655 dc.description.abstract In this thesis, I discuss two studies concerned with modelling protoplanetary discs around stars from different ends of the stellar mass range. In Chapters 1 and 2, I give an introduction to the field of protoplanetary discs, both from an observational and a modelling point of view, and describe the radiative transfer methods I have employed. In Chapter 3, I present my work regarding the disc around the Herbig Ae star HD 163296. I show the results of applying a new modelling technique to this disc: I combine SED modelling with fits to the CO snowline location and C$^{18}$O $J=2-1$ line profile from ALMA. I find that all of the modelling steps are crucial to break degeneracies in the disc parameter space. The use of all of these constraints favours a solution with a notably low gas-to-dust ratio ($g/d<20$). The only models with a more interstellar medium (ISM)-like $g/d$ require C$^{18}$O to be underabundant with respect to the ISM abundances and a significant depletion of sub-micron grains, which is not supported by scattered light observations. I propose that the technique can be applied to a range of discs and opens up the prospect of being able to measure disc dust and gas budgets without making assumptions about the $g/d$ ratio. In Chapter 4, I present my work on characterising the disc around the very low mass star V410 X-ray 1. Protoplanetary discs around such low mass stars offer some of the best prospects for forming Earth-sized planets in their habitable zones. The SED of V410 X-ray 1 is indicative of an optically thick and very truncated dust disc, with my modelling suggesting an outer radius of only 0.6 au. I investigate two scenarios that could lead to such a truncation, and find that the observed SED is compatible with both. The first scenario involves the truncation of both the dust and gas in the disc, perhaps due to a previous dynamical interaction or the presence of an undetected companion. The second scenario involves the fact that a radial location of 0.6 au is close to the expected location of the H$_2$O snowline in the disc. As such, a combination of efficient dust growth, radial migration, and subsequent fragmentation within the snowline leads to an optically thick inner dust disc and larger, optically thin outer dust disc. I find that a firm measurement of the CO $J=2-1$ line flux would distinguish between these two scenarios by enabling a measurement of the radial extent of gas in the disc. Many models I consider contain at least several Earth-masses of dust interior to 0.6 au, suggesting that V410 X-ray 1 could be a precursor to a system of tightly-packed inner planets, such as TRAPPIST-1. In Chapter 5, I summarise the work presented in this thesis, give an overview of future applications of the methods outlined in this dissertation, and an outlook on potential future projects. dc.description.sponsorship STFC dc.language.iso en dc.rights All rights reserved dc.rights All Rights Reserved en dc.rights.uri https://www.rioxx.net/licenses/all-rights-reserved/ en dc.subject astronomy dc.subject planet formation dc.subject protoplanetary discs dc.subject ALMA dc.title Protoplanetary discs across the stellar mass range dc.type Thesis dc.type.qualificationlevel Doctoral dc.type.qualificationname Doctor of Philosophy (PhD) dc.publisher.institution University of Cambridge dc.publisher.department Institute of Astronomy dc.date.updated 2018-06-29T10:07:31Z dc.identifier.doi 10.17863/CAM.24991 dc.publisher.college Murray Edwards College dc.type.qualificationtitle PhD in Astronomy cam.supervisor Clarke, Cathie J. cam.supervisor Ilee, John D. cam.thesis.funding true rioxxterms.freetoread.startdate 2019-06-29
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