Astronomy and Astrophysics – Astrophysics
Scientific paper
May 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...445..330n&link_type=abstract
The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 445, no. 1, p. 330-336
Astronomy and Astrophysics
Astrophysics
13
Accretion Disks, Molecular Clouds, Planetary Evolution, Pre-Main Sequence Stars, Protoplanets, Protostars, Star Formation, Angular Momentum, Gravitation, Mass Flow Rate, Mass Ratios, Stability, Stellar Models
Scientific paper
The growing process of protoplanetary disks around protostars is investigated using a numerical model. The disk growing process can be divided into two subprocesses: the infall (gravitational collapse) of a molecular cloud core and the disk accretion. The infall is characterized by the amount of the total angular momenta of initial molecular cloud cores J, and the disk accretion is done by a viscosity parameter alpha which represents the intensity of torque in the protoplanetary disks. We consider the parameter range 0.6 less than or equal to J less than or equal to 10 (in units of 1053 g/sq cm/s) and 10-5 less than or equal to alpha less than or equal to 0.1. We can obtain a constraint on alpha that log alpha greater than or equal to -2.0 + 4.5 log J - 3.9(log J)2 if we adopt the observational constraints (Beckwith et al. 1990; Ohashi et al. 1991, 1994) that the disk-to-star mass ratio should be lower than 0.1. Moreover, when we use the observational values of the total angular momenta of cloud cores (J = 1-20; Goldsmith & Arquilla 1985; Goodman et al. 1993), the parameter alpha has to be greater than 0.01. When the disk accretion works more efficiently than the infall (i.e., when the above constraints are satisfied), the final disk mass becomes small and the disk mass Md increases nonlinearly with time t as M9 proportional to t squared, i.e., the disk grows suddenly in the later stage of the infalling phase. The nonlinear growth of the disk mass seems to be consistent with the observation by Ohashi et al. (1994).
Nakagawa Yoshitsugu
Nakamoto Taishi
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