Ionisation-induced star formation III: Effects of external triggering on the IMF in clusters

TL;DR

This study uses SPH simulations to examine how external ionizing radiation influences star formation in a turbulent molecular cloud, finding that turbulence dominates star formation processes and feedback has minimal impact on the initial mass function.

Contribution

It provides new insights into the limited role of ionization feedback in star formation and the dominant influence of turbulence on the initial mass function in molecular clouds.

Findings

Ionization significantly alters gas morphology but minimally affects star formation rate.

Star formation is primarily governed by turbulence-induced gas structure.

Feedback does not significantly change the stellar initial mass function.

Abstract

We report on Smoothed Particle Hydrodynamics (SPH) simulations of the impact on a turbulent $\sim2\times10^{3}$ M$_{\odot}$ star--forming molecular cloud of irradiation by an external source of ionizing photons. We find that the ionizing radiation has a significant effect on the gas morphology, but a less important role in triggering stars. The rate and morphology of star formation are largely governed by the structure in the gas generated by the turbulent velocity field, and feedback has no discernible effect on the stellar initial mass function. Although many young stars are to be found in dense gas located near an ionization front, most of these objects also form when feedback is absent. Ionization has a stronger effect in diffuse regions of the cloud by sweeping up low--density gas that would not otherwise form stars into gravitationally--unstable clumps. However, even in these regions, dynamical interactions between the stars rapidly erase the correlations between their positions and velocities and that of the ionization front.