Abstract
ABSTRACT We introduce a new suite of simulations, ‘The Cloud Factory’, which self-consistently forms molecular cloud complexes at high enough resolution to resolve internal substructure (up to 0.25 M⊙ in mass) all while including galactic-scale forces. We use a version of the arepo code modified to include a detailed treatment of the physics of the cold molecular ISM, and an analytical galactic gravitational potential for computational efficiency. The simulations have nested levels of resolution, with the lowest layer tied to tracer particles injected into individual cloud complexes. These tracer refinement regions are embedded in the larger simulation so continue to experience forces from outside the cloud. This allows the simulations to act as a laboratory for testing the effect of galactic environment on star formation. Here we introduce our method and investigate the effect of galactic environment on filamentary clouds. We find that cloud complexes formed after a clustered burst of feedback have shorter lengths and are less likely to fragment compared to quiescent clouds (e.g. the Musca filament) or those dominated by the galactic potential (e.g. Nessie). Spiral arms and differential rotation preferentially align filaments, but strong feedback randomizes them. Long filaments formed within the cloud complexes are necessarily coherent with low internal velocity gradients, which has implications for the formation of filamentary star-clusters. Cloud complexes formed in regions dominated by supernova feedback have fewer star-forming cores, and these are more widely distributed. These differences show galactic-scale forces can have a significant impact on star formation within molecular clouds.
Highlights
Galactic dynamics and star formation are inextricably linked
In this paper we have set-out to generate filament networks within molecular cloud complexes self-consistently taking into account the following large-scale forces that act outside the clouds from the galactic environment: (1) the galactic potential and spiral arms
We have introduced a new suite of simulations, ‘The Cloud Factory’, which self-consistently forms molecular cloud complexes at high enough resolution to resolve internal substructure all while including galactic-scale forces
Summary
Galactic dynamics and star formation are inextricably linked. Galactic-scale structures, such as spiral arms or bars, aggregate cold molecular gas, differential rotation stretches it, and feedback from supernovae injects momentum into the interstellar medium (ISM), driving the gas apart again. C 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society distribution function (PDF) with a width related to the properties of the turbulence – in combination with a model for the onset of gravitational collapse to predict the efficiency with which gas is transformed into stars (e.g Padoan & Nordlund 2002; Krumholz & McKee 2005; Hennebelle & Chabrier 2008; Federrath & Klessen 2013; Burkhart 2018) Simulations of this process typically use a periodic box setup where turbulence is driven at large scales to generate turbulent scaling laws reminiscent of those observed in molecular clouds (Larson 1981; Heyer & Brunt 2004). There remains the question of how closely real molecular clouds resemble these idealized models
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