Triggered star formation by shocks

TL;DR

This study uses 3D hydrodynamical simulations to explore how shock waves can trigger star formation by compressing clouds, revealing dependencies on shock strength, cloud properties, and turbulence, with implications for star mass and cloud evolution.

Contribution

It provides a detailed analysis of shock-cloud interactions, deriving conditions for triggered collapse and examining effects of turbulence on star formation, which advances understanding of star formation processes.

Findings

Stronger shocks more efficiently trigger cloud collapse.

Excessively strong shocks destroy clouds, reducing star masses.

Turbulence prevents rapid cloud contraction, leading to smaller stars.

Abstract

Star formation can be triggered by compression from shock waves. In this study, we investigated the interaction of hydrodynamic shocks with Bonnor-Ebert spheres using 3D hydrodynamical simulations with self-gravity. Our simulations indicated that the cloud evolution primarily depends on two parameters: the shock speed and initial cloud radius. The stronger shock can compress the cloud more efficiently, and when the central region becomes gravitationally unstable, a shock triggers the cloud contraction. However, if it is excessively strong, it shreds the cloud more violently and the cloud is destroyed. From simple theoretical considerations, we derived the condition of triggered gravitational collapse, which agreed with the simulation results. Introducing sink particles, we followed the further evolution after star formation. Since stronger shocks tend to shred the cloud material more efficiently, the stronger the shock is, the smaller the final (asymptotic) masses of the stars formed (i.e., sink particles) become. In addition, the shock accelerates the cloud, promoting mixing of shock-accelerated interstellar medium gas. As a result, the separation between the sink particles and the shocked cloud center and their relative speed increase over time. We also investigated the effect of cloud turbulence on shock-cloud interaction. We observed that the cloud turbulence prevents rapid cloud contraction; thus, the turbulent cloud is destroyed more rapidly than the thermally-supported cloud. Therefore, the masses of stars formed become smaller. Our simulations can provide a general guide to the evolutionary process of dense cores and Bok globules impacted by shocks.