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The effect of a finite mass reservoir on the collapse of spherical isothermal clouds and the evolution of protostellar accretion | | E. I. Vorobyov
; Shantanu Basu
; | | Date: |
3 Apr 2005 | | Journal: | Mon.Not.Roy.Astron.Soc. 360 (2005) 675-684 | | Subject: | astro-ph | | Affiliation: | 1 and 2) and Shantanu Basu ( Department of Physics and Astronomy, University of Western Ontario, London, Canada, Institute of Physics, Rostov-on-Don, Russia | | Abstract: | Motivated by recent observations which detect an outer boundary for starless cores, and evidence for time-dependent mass accretion in the Class 0 and Class I protostellar phases, we reexamine the case of spherical isothermal collapse in the case of a finite mass reservoir. The presence of a core boundary results in the generation of an inward propagating rarefaction wave. This steepens the gas density profile from r^{-2} to r^{-3} or steeper. After a protostar forms, the mass accretion rate dot{M} evolves through three distinct phases: (1) an early phase of decline in dot{M}, which is a non-self-similar effect due to spatially nonuniform infall in the prestellar phase; (2) for large cores, an intermediate phase of near-constant dot{M} from the infall of the outer part of the self-similar density profile; (3) a late phase of rapid decline in dot{M} when accretion occurs from the region affected by the inward propagating rarefaction wave. Our model clouds of small to intermediate size make a direct transition from phase (1) to phase (3) above. Both the first and second phase are characterized by a temporally increasing bolometric luminosity L_bol, while L_bol is decreasing in the third (final) phase. We identify the period of temporally increasing L_bol with the Class 0 phase, and the later period of terminal accretion and decreasing L_bol with the Class I phase. The peak in L_bol corresponds to the evolutionary time when 50% pm 10% of the cloud mass has been accreted by the protostar. This is in agreement with the classification scheme proposed by Andre et al. (1993). We show how our results can be used to explain tracks of envelope mass M_env versus L_bol for protostars in Taurus and Ophiuchus. We also develop an analytic formalism which reproduces the protostellar accretion rate. | | Source: | arXiv, astro-ph/0504055 | | Services: | Forum | Review | PDF | Favorites | |
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