Triggered Star Formation and Its Consequences

TL;DR

This study uses advanced simulations to explore how shock waves trigger star formation, influence disk formation, and affect material mixing, providing insights into planetary system development and isotopic enrichment in the Solar System.

Contribution

It presents the first comprehensive AMR simulation of full collapse and evolution of Bonnor-Ebert spheres under shock influence, including disk formation and material mixing.

Findings

Triggered collapse occurs robustly in non-rotating clouds.

Massive, long-lived circumstellar disks can form despite shock ablation.

Higher Mach numbers increase mixing of wind and cloud material.

Abstract

Star formation can be triggered by compression from wind or supernova driven shock waves that sweep over molecular clouds. Because these shocks will likely contain processed elements, triggered star formation has been proposed as an explanation for short lived radioactive isotopes (SLRI) in the Solar System. Previous studies have tracked the triggering event to the earliest phases of collapse and have focused on the shock properties required for both successful star formation and mixing of SLRI's. In this paper, we use Adaptive Mesh Refinement (AMR) simulation methods, including sink particles, to simulate the full collapse and subsequent evolution of a stable Bonnor-Ebert sphere subjected to a shock and post-shock wind. We track the flow of the cloud material after a star (a sink particle) has formed. For non-rotating clouds we find robust triggered collapse and little bound circumstellar material remaining around the post-shock collapsed core. When we add initial cloud rotation we observe the formation of disks around the collapsed core which then interact with the post-shock flow. Our results indicate that these circumstellar disks are massive enough to form planets and are long-lived, in spite of the ablation driven by post-shock flow ram pressure. As a function of the initial conditions, we also track the time evolution of the accretion rates and particle mixing between between the ambient wind and cloud material. The latter is maximized for cases of highest mach number.