Thermal structure of a protostellar envelope

TL;DR

This paper presents a numerical hydrodynamical model for the thermal evolution of collapsing star-forming clouds, incorporating independent gas and dust temperatures and protostellar radiation, validated against Herschel observations.

Contribution

It introduces a novel model that separately describes gas and dust temperatures and accounts for protostellar radiation, improving understanding of thermal structures in star-forming regions.

Findings

Diffusion approximation with flux limiter fits observed density and temperature profiles.

Discrepancies found between model and observations in prestellar stages.

The $ au$-approximation agrees well in prestellar phase but less so in protostellar phase.

Abstract

A numerical hydrodynamical model for the evolution of spherically symmetric collapsing clouds, designed for the calculation of the thermal structure of these objects in both the prestellar and protostellar stages of their evolution, is presented. Distinctive features of the model include the possibility of independently describing the temperatures of the gas and dust, which is extremely important when calculating the thermal structure of prestellar and protostellar clouds, and the account of the radiation flux from the central protostar. This model is used to compare the theoretical density and temperature distributions with observations for nearby sites of star formation obtained with the Herschel Space Observatory. Application of the diffusion approximation with a flux limiter describes well the radial density and temperature distributions in protostellar clouds. However, significant differences between the model and observational density profiles were found for prestellar stages, suggesting the presence of appreciable deviations from equilibrium in the prestellar clouds. An approximate method for calculating the thermal structure of a cloud based on the adaptive $\tau$-approximation is presented. Application of the $\tau$-approximation yields good agreement with the diffusion approximation for the prestellar phase, but produces appreciable discrepancies for the protostellar phase, when the thermal structure of the accreting envelope is determined by the radiation of the protostar.