SCYON Abstract

Received on May 14 2001

A Two-Step Initial Mass Function: Consequences of Clustered Star Formation for Binary Properties

AuthorsR.H. Durisen1, M.F. Sterzik2, and B.K. Pickett3
Affiliation1 Department of Astronomy, SW319, Indiana University, Bloomington, Indiana 47405, U.S.A.,
2 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile,
3 Department of Chemistry and Physics, Purdue University Calumet, 2200 169th Street, Hammond, Indiana 46323, U.S.A.
Accepted by


If stars originate in transient bound clusters of moderate size, these clusters will decay due to dynamic interactions in which a hard binary forms and ejects most or all the other stars. When the cluster members are chosen at random from a reasonable initial mass function (IMF), the resulting binary characteristics do not match current observations. We find a significant improvement in the trends of binary properties from this scenario when an additional constraint is taken into account, namely that there is a distribution of total cluster masses set by the masses of the cloud cores from which the clusters form. Two distinct steps then determine final stellar masses -- the choice of a cluster mass and the formation of the individual stars. We refer to this as a ``two-step'' IMF. Simple statistical arguments are used in this Paper to show that a two-step IMF, combined with typical results from dynamic few-body system decay, tends to give better agreement between computed binary characteristics and observations than a one-step mass selection process.