AAS 206th Meeting, 29 May - 2 June 2005
Session 7 Star Formation
Poster, Monday, 9:20am-6:30pm, Tuesday, 10:00am-7:00pm, May 30, 2005, Ballroom A

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[7.09] Generalized Collapse Solutions with Initial Velocities for Star Formation in Molecular Cloud Cores

M. Fatuzzo (Xavier University), F. C. Adams (University of Michigan), P. C. Myers (Harvard Smithsonian CfA)

Motivated by recent observations that show starless molecular cloud cores exhibit subsonic inward velocities, we revisit the collapse problem for polytropic gaseous spheres. In particular, we provide a generalized treatment of protostellar collapse in the spherical limit and find semi-analytic (self-similar) solutions, corresponding numerical solutions, and purely analytic calculations of the mass infall rates (the three approaches are in good agreement). This study focuses on collapse solutions that exhibit nonzero inward velocities at large radii, as observed in molecular cloud cores, and extends previous work in four ways: (1) The initial conditions allow nonzero initial inward velocity. (2) The starting states can exceed the density of hydrostatic equilibrium so that the collapse itself can provide the observed inward motions. (3) We consider different equations of state, especially those that are softer than isothermal. (4) We consider dynamic equations of state that are different from the effective equation of state that produces the initial density distribution. This work determines the infall rates over a wide range of parameter space, as characterized by four variables: the initial inward velocity, the overdensity of the initial state, the index of the static equation of state, and the index of the dynamic equation of state. For the range of parameter space applicable to observed cores, the resulting infall rate is about a factor of two larger than found in previous theoretical studies (those with hydrostatic initial conditions and no initial inward velocity).

The author(s) of this abstract have provided an email address for comments about the abstract: fatuzzo@xavier.edu

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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.