Simulated observations of and flow interactions with discs

This thesis presents simulations of the dynamics and radiation processes in accretion discs around young protostars. Firstly the dust continuum and molecular line emission from a graviationally unstable, 0.4M_sol disc around a young 1M_sol mass protostar are calculated. Such massive, unstable discs are thought to be an early stage in the evolution of low mass protostars and the gravitational instabilities in them provide a method of transferring angular momentum outwards and mass inward when there is insufficient ionised material for magnetic instabilities to provide such torques. The potential for observations of such a disc in continuum and line emission with ALMA is explored using radiative transfer and synthetic observations and four molecular traces of spiral structure are identified.
Secondly, radiation-hydrodynamic models of accretion discs around 10M_sol protostars of varying radii are presented. The effects of different driving parameters and accretion luminosity are explored. The resulting density distribution is analysed in order to distinguish between ionised and neutral material. The amount of mass lost, the linear and rotational velocity of the winds and the division of the mass between the slow, dense disc wind and the fast rarefied polar wind is analysed for each of the models. The amount of visible mass lost through the disc is found to be strongly related to the luminosity of the disc and most of the disc mass is launched from the inner regions rather than mass loading further out.
Finally radiative transfer modeling and synthetic observations are performed for the hydrodynamic models from the previous chapter. These include radio free-free emission, ionised carbon forbidden lines and hydrogen recombination lines. These are compared to observations of discs around MYSOs. The radio free-free emission is used as the input to a telescope simulation in order to provide synthetic interferometer observations with the e-Merlin radio telescope network.