Understanding the Stellar Initial Mass Function

TL;DR

This paper reviews the key features of the stellar Initial Mass Function, linking its shape to physical processes like fragmentation and accretion, and discusses variations observed in different environments such as the Galactic Center.

Contribution

It synthesizes recent theoretical and observational insights into the origins of the IMF's characteristic features and their physical explanations.

Findings

IMF peak linked to fragmentation scale at the transition to isothermal collapse

Salpeter power law possibly generated by scale-free accretion processes

High-mass stars in the Galactic Center may result from high opacity effects

Abstract

The essential features of the stellar Initial Mass Function are, rather generally, (1) a peak at a mass of a few tenths of a solar mass, and (2) a power-law tail toward higher masses that is similar to the original Salpeter function. Recent work suggests that the IMF peak reflects a preferred scale of fragmentation associated with the transition from a cooling phase of collapse at low densities to a nearly isothermal phase at higher densities, where the gas becomes thermally coupled to the dust. The Salpeter power law is plausibly produced, at least in part, by scale-free accretion processes that build up massive stars in dense environments. The young stars at the Galactic Center appear to have unusually high masses, possibly because of a high minimum mass resulting from the high opacity of the dense star-forming gas.