Talk abstract

Understanding how dense prestellar cores form within Giant Molecular Clouds (GMCs) is of vital importance for a proper understanding of the earliest phases of star formation. Many observed cores have masses comparable to the mean Jeans mass of the gas in a GMC, leading one to expect that they will be highly sensitive to the thermodynamical behaviour of the gas. Despite this, most hydrodynamical or MHD models of core formation rely on very simplified prescriptions for treating the thermal evolution of the gas. We have attempted to address this weakness in previous models by performing high resolution hydrodynamical simulations of core formation that properly treat the effects of radiative heating and cooling, using a novel tree-based approach to account for dust shielding. Our simulations also follow the chemical evolution of the major gas coolants: for instance, we are able to follow the transition from C$^{+}$ in the diffuse interclump regions in the GMC to C and then CO in the denser gas in the cores. We have used our simulations to explore the effects of the external environment -- specifically, the strength of the ambient interstellar radiation field (ISRF) -- on the formation of prestellar cores within the cloud, and will show that although large changes in the ISRF can lead to large changes in the observational appearance of the GMCs, they have a surprisingly small impact on core formation.