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

• Published in: Publications of the Astronomical Society of the Pacific Vol. 121; no. 879; pp. 485 - 497
• Main Authors: Holden, Lisa, Hoppins, Kevin, Baxter, Benjamin, Fatuzzo, Marco
• Format: Journal Article
• Language: English
• Published: Chicago, IL University of Chicago Press 01.05.2009
• Subjects: Astronomy; Average linear density; Density; Earth, ocean, space; Equations of motion; Equations of state; Exact sciences and technology; Gas density; Hematocrit; Hydrostatics; Mass; Molecular clouds; Velocity distribution; Collapse; Equations of state; Similarity solution; Dynamics; Selfsimilarity
• ISSN: 0004-6280; 1538-3873
• DOI: 10.1086/599382

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 factorΛ Λ 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 that define the overall state of the gas—the overdensity parameterΛ Λ , the indexΓ Γ of the static equation of state, and the indexγ γ 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 caseγ = 1 γ = 1 .