Environmental variation of the low-mass IMF

TL;DR

This study uses magnetohydrodynamic simulations with feedback mechanisms to explore how environmental factors influence the initial mass function, revealing that higher surface densities lead to a lower characteristic stellar mass.

Contribution

It demonstrates how radiative and protostellar feedback effects vary with environment, affecting the shape and characteristic mass of the IMF in dense regions.

Findings

Radiation feedback suppresses low-mass star formation more at higher surface densities.

Protostellar outflows reduce massive star formation in dense environments.

IMF becomes narrower with a lower characteristic mass in high surface density regions.

Abstract

We use a series of magnetohydrodynamic simulations including both radiative and protostellar outflow feedback to study the environmental variation of the initial mass function. The simulations represent a carefully-controlled experiment whereby we keep all dimensionless parameters of the flow constant except for those related to feedback. We show that radiation feedback suppresses the formation of lower mass objects more effectively as the surface density increases, but this only partially compensates for the decreasing Jeans mass in denser environments. Similarly, we find that protostellar outflows are more effective at suppressing the formation of massive stars in higher surface density environments. The combined effect of these two trends is towards an IMF with a lower characteristic mass and a narrower overall mass range in high surface density environments. We discuss the implications of these findings for the interpretation of observational evidence of IMF variation in early-type galaxies.