The effect of non-isothermality on the gravitational collapse of spherical clouds and the evolution of protostellar accretion

Author(s): E. I. Vorobyov, Shantanu Basu
Abstract: We investigate the role of non-isothermality in gravitational collapse and protostellar accretion by explicitly including the effects of molecular radiative cooling, gas-dust energy transfer and cosmic ray heating in models of spherical hydrodynamic collapse. Isothermal models have previously shown an initial decline in the mass accretion rate Ṁ during the accretion phase of protostellar evolution, as a result of the gradient of the infall speed that develops in the prestellar phase. Our results show that: (1) in the idealized limit of optically thin cooling, a positive temperature gradient is present in the prestellar phase which effectively cancels out the effect of the velocity gradient, producing a near-constant (weakly increasing with time) Ṁ in the early accretion phase; and (2) in the more realistic case including cooling saturation at higher densities, Ṁ may initially be either weakly increasing or weakly decreasing with time, for the low dust temperature (T_d ∼ 6 K) and high dust temperature (T_d ∼ 10 K) cases, respectively. Hence, our results show that the initial decline in Ṁ seen in isothermal models is definitely not enhanced by non-isothermal effects, and is often suppressed by them. In all our models, Ṁ does eventually decline rapidly due to the finite mass condition on our cores and a resulting inward-propagating rarefaction wave. Thus, any explanation for a rapid decline of Ṁ in the accretion phase probably needs to appeal to the global molecular cloud structure and possible envelope support, which results in a finite mass reservoir for cores.
Organisation(s): Research Platform Erwin Schrödinger International Institute for Mathematics and Physics, Department of Astrophysics
External organisation(s): University of Toronto, University of Western Ontario
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 363
Pages: 1361-1368
No. of pages: 8
ISSN: 0035-8711
DOI: https://doi.org/10.1111/j.1365-2966.2005.09528.x
Publication date: 11-2005
Peer reviewed: Yes
Austrian Fields of Science 2012: 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Space and Planetary Science, Astronomy and Astrophysics
Portal url: https://ucrisportal.univie.ac.at/en/publications/1f025db4-2c37-4238-bc85-a47d4a69cb38

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