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Astro Seminar

Massive discs around low and high mass stars

Speaker: Dr John Ilee (Leeds)
Date: Wednesday 9 October 2019
Time: 14:00
Venue: Queens Buildings N/3.28

Protoplanetary discs are one of the most extreme environments in astrophysics, spanning a huge range of temperatures and densities. As such, modelling their chemical evolution is challenging, and has often been reduced to the study of 2-dimensional, axisymmetric discs. However, the advent of ALMA has shown that many protoplanetary discs do not conform to this axisymmetry. Dust traps, warps, embedded planets and spiral arms have all recently been observed in discs, complicating matters further. In particular, the influence of the dynamic evolution of the disc on the chemical evolution has not been well studied. In this talk I will discuss some of the first calculations of chemical evolution in protoplanetary discs in three-dimensions. In discs which a sufficiently massive, the spiral shocks induced by the self gravity of the disc can have a large effect on the chemistry. Species are desorbed from dust grains at much further radial locations than they would otherwise exist. In addition, the increased temperatures and densities caused by the shocks leads to gas phase reactions in warm, shocked regions that would not otherwise occur. Additionally, if these discs are massive enough to fragment into protoplanets, then our results suggest that these fragments should possess unique chemical signatures. From an observational perspective, we have shown that the Atacama Large Millimetre/submillimetre Array (ALMA) will be an essential tool in catching these phenomena ‘in the wild’, and I will discuss our recent observational campaigns designed characterise the properties of these interesting objects.