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Session 114 - Warner Prize Lecture.
Oral session, Thursday, January 16
The formation of stars and planets is one of the most fundamental problems in astrophysics. In recent years, a lot of progress in this area has been made and we now have a successful paradigm that provides the cornerstone of our current understanding of the star formation process. Within this paradigm, the agreement between observations and theory is quite good, especially for the case of low-mass stars. After reviewing the current theory, we present a class of models for the initial mass function (IMF) for stars forming within molecular clouds. This class of models uses the idea that stars determine their own masses through the action of powerful stellar outflows. This concept allows us to calculate a semi-empirical mass formula (SEMF), which provides the transformation between initial conditions in molecular clouds and the final masses of forming stars. For a particular SEMF, a given distribution of initial conditions predicts a corresponding IMF. We can consider several different descriptions for the distribution of initial conditions in star forming molecular clouds. In the limit in which many different independent physical variables play a role in determining stellar masses, the central limit theorem shows that the IMF approaches a log-normal form. These results show that this picture of star formation and the IMF naturally produces stellar mass distributions that are roughly consistent with observations. This work thus provides a calculational framework to construct theoretical models of the IMF.
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