Inverse Dynamical Population Synthesis and Star Formation

Abstract

We investigate the hypothesis that stars form in aggregates of binary systems and that the dynamical evolution of these aggregates leads to the observed properties of binary stars in the Galactic field. We assume that the initial distribution of periods is flat in logP, where P is the orbital period in days, and 3 7.5. After the cluster with R=0.8pc disintegrates we obtain a population which consists of about 60 per cent binary systems with a period distribution for logP>4 as is observed and in which the G-dwarf binaries have a mass ratio distribution which agrees with the observed distribution. This result indicates that the majority of Galactic field stars may originate from a clustered star formation mode. We invert the orbit depletion function and obtain an approximation to the initial binary star period distribution for star formation in the dominant mode cluster. Comparison with the measured distribution of orbits for pre-main sequence stars suggests that the initial distribution may not depend on the star formation environment. Inverse dynamical population synthesis suggests that the Galactic field stellar mass function may be related to the stellar density at birth in the most common, or dominant, mode of star formation.