Are turbulent spheres suitable initial conditions for star-forming clouds?

TL;DR

This study compares realistic galactic molecular cloud initial conditions with idealized turbulent spheres, revealing that initial velocity structures significantly influence star formation rates and cloud evolution.

Contribution

It introduces a method to use galactic simulation-derived clouds as initial conditions, providing more realistic setups for star formation modeling.

Findings

Galactic clouds have more complex structures than turbulent spheres.

Inherited velocity structures affect star formation rates.

Turbulent spheres do not fully replicate galactic cloud complexity.

Abstract

To date, most numerical simulations of molecular clouds, and star formation within them, assume a uniform density sphere or box with an imposed turbulent velocity field. In this work, we select molecular clouds from galactic scale simulations as initial conditions, increase their resolution, and re-simulate them using the SPH code Gadget2. Our approach provides clouds with morphologies, internal structures, and kinematics that constitute more consistent and realistic initial conditions for simulations of star formation. We perform comparisons between molecular clouds derived from a galactic simulation, and spheres of turbulent gas of similar dimensions, mass and velocity dispersion. We focus on properties of the clouds such as their density, velocity structure and star formation rate. We find that the inherited velocity structure of the galactic clouds has a significant impact on the star formation rate and evolution of the cloud. Our results indicate that, although we can follow the time evolution of star formation in any simulated cloud, capturing the entire history is difficult as we ignore any star formation that might have occurred before initialisation. Overall, the turbulent spheres do not match the complexity of the galactic clouds.