Master's Thesis Defense by Daniel Dalsgaard Jonsson

Title: Modelling Collapse and Accretion of Protostellar Systems

Abstract:  The process of star formation is a truly fascinating one. The attracting properties of self-gravity allows matter in a dense core, with an extent of up to 10.000 AU, to collapse into a star with an extent of 0.001 AU. This, along with the rest of the process, is a multi-scale physical problem extending over 10 orders of magnitude, thus making it difficult to simulate. In this thesis I have investigated the process of accretion with sink particles at varying resolutions and implemented new physics, in the simulation code, RAM- SES, to track the induced spin of the forming protostar. As such, we obtain a better understanding of the interplay and evolution of the star particle with its surroundings. This is done by adapting RAMSES to incorporate spin tracking and to handle accretion in binary systems with a recipe in- spired by literature on binary blacks holes. I successfully show that this is an improvement to previous versions of RAMSES through tests in isolated idealised scenarios, zooming in on a realistic large scale simulation, and in a large scale simulation with many binary systems. The overall conclusion is that these methods show promising potential, although rigorous testing is needed before it can be applied to the production version of the simulation code.

Supervisor: Troels Haugbølle 

Censor: James Emil Avery, Aarhus University