Combining radiative transfer and diffuse interstellar medium physics to model star formation

TL;DR

This paper introduces a novel method that combines models of the diffuse interstellar medium and flux-limited diffusion to accurately simulate the thermal evolution of star-forming clouds across different density regimes, enhancing understanding of star formation.

Contribution

The new approach integrates low-density and high-density thermal models, capturing the separate evolution of gas, dust, and radiation, which was not addressed in previous methods.

Findings

The method effectively models the ISM across a wide density range.

It captures the thermal evolution of gas, dust, and radiation separately.

Comparison shows improved accuracy over existing models.

Abstract

We present a method for modelling star-forming clouds that combines two different models of the thermal evolution of the interstellar medium (ISM). In the combined model, where the densities are low enough that at least some part of the spectrum is optically thin, a model of the thermodynamics of the diffuse ISM is more significant in setting the temperatures. Where the densities are high enough to be optically thick across the spectrum, a model of flux limited diffusion is more appropriate. Previous methods either model the low-density interstellar medium and ignore the thermal behaviour at high densities (e.g. inside collapsing molecular cloud cores), or model the thermal behaviour near protostars but assume a fixed background temperature (e.g. approximately 10 K) on large-scales. Our new method treats both regimes. It also captures the different thermal evolution of the gas, dust, and radiation separately. We compare our results with those from the literature, and investigate the dependence of the thermal behaviour of the gas on the various model parameters. This new method should allow us to model the ISM across a wide range of densities and, thus, develop a more complete and consistent understanding of the role of thermodynamics in the star formation process.