Radiation driven implosion and triggered star formation

TL;DR

This study uses simulations to explore how ionising radiation influences the collapse of stable clouds and triggers star formation, revealing the critical role of radiation flux in determining cloud evolution and star formation outcomes.

Contribution

The paper introduces a simulation framework combining SPH and photo-ionisation algorithms to analyze radiation-driven implosion and star formation in stable clouds, highlighting the impact of ionising flux.

Findings

Ionising flux is the key parameter controlling cloud evolution.

Higher fluxes lead to less star formation and smaller stellar masses.

Star formation occurs along the central axis of the cloud.

Abstract

We present simulations of initially stable isothermal clouds exposed to ionising radiation from a discrete external source, and identify the conditions that lead to radiatively driven implosion and star formation. We use the Smoothed Particle Hydrodynamics code SEREN and an HEALPix-based photo-ionisation algorithm to simulate the propagation of the ionising radiation and the resulting dynamical evolution of the cloud. We find that the incident ionising flux, $\Phi_{_{\rm LyC}}$, is the critical parameter determining the cloud evolution. At moderate fluxes, a large fraction of the cloud mass is converted into stars. As the flux is increased, the fraction of the cloud mass that is converted into stars and the mean masses of the individual stars both decrease. Very high fluxes simply disperse the cloud. Newly-formed stars tend to be concentrated along the central axis of the cloud (i.e. the axis pointing in the direction of the incident flux). For given cloud parameters, the time, $t_{_\star}$, at which star formation starts is proportional to $\Phi_{_{\rm LyC}}^{-1/3}$. The pattern of star formation found in the simulations is similar to that observed in bright-rimmed clouds.