SCYON Abstract

Received on May 14 2001

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

Authors	R.H. Durisen¹, M.F. Sterzik², and B.K. Pickett³
Affiliation	¹ 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.
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Contact	durisen@astro.indiana.edu
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Abstract

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.