Intense star cluster formation: stellar masses, the mass function, and the fundamental mass scale

TL;DR

This paper explores how thermal feedback, radiation pressure, and optical depth influence stellar mass formation and the initial mass function in dense, massive star-forming regions, proposing a fundamental mass scale linked to the Planck mass.

Contribution

It introduces a model connecting thermal stabilization and radiation effects to the stellar mass function and suggests a fundamental mass scale governing star formation in dense environments.

Findings

Thermal feedback can flatten the high-mass slope of the initial mass function.

Optically thick regions tend to produce more top-heavy stellar populations at higher densities.

Radiation pressure can disperse gas before complete star formation occurs.

Abstract

Within the birth environment of a massive globular cluster, the combination of a luminous young stellar population and a high column density induces a state in which the thermal optical depth and radiation pressure are both appreciable. In this state, the sonic mass scale, which influences the peak of the stellar mass function, is tied to a fundamental scale composed of the Planck mass and the mass per particle. Thermal feedback also affects the opacity-limited minimum mass and affects how protostellar outflows and binary fragmentation modify stellar masses. Considering the regions that collapse to form massive stars, we argue that thermal stabilization is likely to flatten the high-mass slope of the initial mass function. Among regions that are optically thick to thermal radiation, we expect the stellar population to become increasingly top-heavy at higher column densities, although this effect can be offset by lowering the metallicity. A toy model is presented that demonstrates these effects, and in which radiation pressure leads to gas dispersal before all of the mass is converted into stars.