The Stellar Initial Mass Function and Beyond

TL;DR

This paper reviews the observed features of the stellar initial mass function (IMF), explores theoretical explanations for its shape, and discusses the implications of star cluster mass on the formation of massive stars and black holes.

Contribution

It synthesizes observational data and theoretical models to explain the characteristic stellar mass and the high-mass end of the IMF, highlighting the role of clump mass, Jeans mass, and cluster dynamics.

Findings

Characteristic stellar mass linked to molecular cloud clumps

Salpeter power law possibly due to accretion and mergers

Maximum stellar mass increases with cluster mass

Abstract

A brief review is given of the basic observed features of the stellar IMF, and also of some of the theoretical ideas and simulations that may help to explain these features. The characteristic stellar mass of order one solar mass may derive from the typical masses of the observed star-forming clumps in molecular clouds, and the typical clump mass may in turn be determined mainly by the Jeans mass, as is true in many numerical simulations of cloud collapse and fragmentation. The Salpeter power law that approximates the IMF at higher masses is less well understood, but it may result from the effects of continuing gas accretion by the more massive forming stars together with the effects of interactions and mergers in dense forming stellar systems. The mass of the most massive star that forms in a cluster is observed to increase systematically with the mass of the cluster, and the most massive clusters may form stars that are massive enough to collapse completely to black holes.