Wednesday 25 Nov 2015: Seminar: ***CHANGE OF TIME 4pm*** The Role of Discs in the Collapse and Fragmentation of Prestellar Cores
Dr Oliver Lomax - Cardiff University
Physics, 4th floor 16:00-17:00
Disc fragmentation provides an important mechanism for producing low mass stars in prestellar cores. Here, we describe Smoothed Particle Hydrodynamics simulations which show how populations of prestellar cores evolve into stars. We find the observed masses and multiplicities of stars can be recovered under certain conditions.
First, protostellar feedback from a star must be episodic. The continuous accretion of disc material on to a central protostar results in local temperatures which are too high for disc fragmentation. If, however, the accretion occurs in intense outbursts, separated by a downtime of ~10^4 years, gravitational instabilities can develop and the disc can fragment.
Second, a significant amount of the cores' internal kinetic energy should be in solenoidal turbulent modes. Cores with less than a third of their kinetic energy in solenoidal modes have insufficient angular momentum to form fragmenting discs. In the absence of discs, cores can fragment but results in a top heavy distribution of masses with very few low mass objects.