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

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.

13 pages, 12 figures, accepted by ApJ

References in corpus (4)

• Theory of Star Formation
• On the Rapid Collapse and Evolution of Molecular Clouds
• On the Structure of the Orion A Cloud and the Formation of the Orion Nebula Cluster
• Nonlinear Evolution of the Magnetohydrodynamic Rayleigh-Taylor Instability

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• Rapid Molecular Cloud and Star Formation: Mechanisms and Movies
• GMC formation by agglomeration and self gravity
• The ISM in spiral galaxies: can cooling in spiral shocks produce molecular clouds?
• Fragmentation of Shocked Flows: Gravity, Turbulence and Cooling
• Core Mass Function: The Role of Gravity
• Nonlinear Evolution of Gravitational Fragmentation Regulated by Magnetic Fields and Ambipolar Diffusion
• A complete 12CO 2--1 map of M51 with HERA: II. Total gas surface densities and gravitational stability
• Tidal Disruption of Protoclusters in Giant Molecular Clouds