Self-Similar Collapse Solutions for Cylindrical Cloud Geometries and Dynamic Equations of State

TL;DR

This paper develops a self-similar model for cylindrical molecular cloud collapse, incorporating dynamic equations of state to better understand star formation in elongated structures, and analyzes mass infall rates across various parameters.

Contribution

It extends previous models by including dynamic equations of state and analyzing their effects on collapse solutions and mass infall rates in filamentary molecular clouds.

Findings

Most parameter choices lead to non-singular solutions.

Mass infall rates depend on overdensity and equations of state.

Special solutions are identified for the case b5 = 1.

Abstract

A self-similar formalism for the study of the gravitational collapse of molecular gas provides an important theoretical framework from which to explore the dynamics of star formation. Motivated by the presence of elongated and filamentary structures observed in giant molecular clouds, we build upon the existing body of work on cylindrical self-similar collapse flows by including dynamic equations of state that are different from the effective equation of state that produces the initial density distribution. We focus primarily on the collapse of initial states for which the gas is at rest and everywhere overdense from its corresponding hydrostatic equilibrium profile by a factor $\Lambda$, and apply our results toward the analysis of star formation within dense, elongated molecular cores. An important aspect of this work is the determination of the mass infall rates over a range of the parameters which define the overall state of the gas -- the overdensity parameter $\Lambda$, the index $\Gamma$ of the static equation of state, and the index $\gamma$ of the dynamic equation of state. While most of the parameter space explored in this work leads to solutions for which the underlying equations do not become singular, we do include a discussion on how to treat cases for which solutions pass smoothly through the singular surface. In addition, we also present a different class of collapse solutions for the special case $\gamma = 1$.