Formation and Evolution of Protostellar Disks in Young Star Clusters: Implications for the Origin of Binary Stars and Substellar Objects

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Understanding the formation and evolution of protostellar disks is a key ingredient in star formation theory. The properties of such disks determine the probability of binary star formation. Furthermore, they define the environment where substellar-mass objects, the so called brown dwarfs, or planets and planetary systems build up. Detailed knowledge of protostellar disk evolution therefore is essential for understanding the properties of extrasolar planets, and bears great importance for understanding the origin of our own solar system. In the long run it may thus contribute to speculations about the origin of life on our planet and the possibility of life in ohter parts of the universe. These are fundamental questions with great appeal to the general public.The specific aim of this project is to study the formation of stars and substellar objects in turbulent interstellar gas clouds by means of numerical simulations. We will follow in great detail the evolution of protostars and their associated disks in nascent star clusters. As most stars form in a clustered environment, mutual interactions may drastically alter the evolutionary properties of protostellar disks and their ability to give birth to stars and substellar objects. This link has not yet been studied in sufficient detail and with sufficient numerical resolution.We will try to understand and predict the observed frequency of binary/multiple stellar systems, the overall efficiency of star formation, the boundedness of the resulting star clusters, the stellar and substellar mass spectrum, and the probability of forming substellar-mass objects in the disk. In particular, we will investigate in detail the efficiency of disk fragmentation as a possible mechanism for forming brown dwarfs and giant gas planets, and follow the long-term dynamical evolution of such systems as parts of dense clusters.