Cooling, Gravity and Geometry: Flow-driven Massive Core Formation

TL;DR

This study uses numerical simulations to explore how molecular clouds form and evolve under the influence of gravity, thermal, and dynamical instabilities, revealing the early determination of core mass distributions.

Contribution

It demonstrates that core mass distributions are primarily shaped by thermal and dynamical instabilities early in cloud formation, with gravity influencing large-scale structures.

Findings

Large-scale filaments formed by global gravity.

Massive protostellar cores of a few hundred solar masses form rapidly.

Core mass distribution set early by instabilities, not gravity.

Abstract

We study numerically the formation of molecular clouds in large-scale colliding flows including self-gravity. The models emphasize the competition between the effects of gravity on global and local scales in an isolated cloud. Global gravity builds up large-scale filaments, while local gravity -- triggered by a combination of strong thermal and dynamical instabilities -- causes cores to form. The dynamical instabilities give rise to a local focusing of the colliding flows, facilitating the rapid formation of massive protostellar cores of a few 100 M$_\odot$. The forming clouds do not reach an equilibrium state, though the motions within the clouds appear comparable to ``virial''. The self-similar core mass distributions derived from models with and without self-gravity indicate that the core mass distribution is set very early on during the cloud formation process, predominantly by a combination of thermal and dynamical instabilities rather than by self-gravity.