Exploring the conditions required to form planets in realistically modelled self-gravitating discs
We present new results on giant planet formation by fragmentation of large self-gravitating discs. The early evolution of such massive discs has been considered using cooling parameters to describe the thermodynamics (e.g. Lodato & Rice 2004) and using grid-based (e.g. Cai et al. 2008; Boss 2004) and hydrodynamical (e.g. Stamatellos & Whitworth 2008) radiative transfer calculations. We present new results from simulations using a Smoothed Particle Hydrodynamics code with flux-limited diffusion to follow disc evolutions in order to simulate more realistically the physical processes of energy transfer that may occur in such massive and extended discs, as well as the effects of stellar irradiation and differing disc opacities. We discuss the possibility of fragmentation at radii of O(100) AU, particularly focussing on the cooling rates in such discs by comparing them with the fragmentation criterion of Gammie (2001) and Rice et al (2005). Moreover, we also discuss the applicability of these criterion as well as those of Rafikov (2005) and Clarke (2009) in such discs. Furthermore, we consider the likelihood of fragmentation if the disc photosphere is cooled (which may occur if for example, shadowing were to take place).