FORMATION PROCESS OF THE CIRCUMSTELLAR DISK: LONG-TERM SIMULATIONS IN THE MAIN ACCRETION PHASE OF STAR FORMATION

Journal Article · Wed Dec 01 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/724/2/1006· OSTI ID:21474497

Machida, Masahiro N ^[1]; Inutsuka, Shu-ichiro ^[2]; Matsumoto, Tomoaki ^[3]

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1. National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
2. Department of Physics Nagoya University Furo-cho, Chikusa-ku Nagoya, Aichi 464-8602 (Japan)
3. Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan)

The formation and evolution of the circumstellar disk in unmagnetized molecular clouds is investigated using three-dimensional hydrodynamic simulations from the prestellar core until the end of the main accretion phase. In collapsing cloud cores, the first (adiabatic) core with a size of {approx}>3 AU forms prior to the formation of the protostar. At its formation, the first core has a thick disk-like structure and is mainly supported by the thermal pressure. After the protostar formation, it decreases the thickness gradually and becomes supported by the centrifugal force. We found that the first core is a precursor of the circumstellar disk with a size of >3 AU. This means that unmagnetized protoplanetary disk smaller than <3 AU does not exist. Reflecting the thermodynamics of the collapsing gas, at the protostar formation epoch, the first core (or the circumstellar disk) has a mass of {approx}0.005-0.1 M{sub sun}, while the protostar has a mass of {approx}10{sup -3} M{sub sun}. Thus, just after the protostar formation, the circumstellar disk is about 10-100 times more massive than the protostar. In the main accretion phase that lasts for {approx}10{sup 5} yr, the circumstellar disk mass initially tends to dominate the protostellar mass. Such a massive disk is unstable to gravitational instability and tends to show fragmentation. Our calculations indicate that the low-mass companions may form in the circumstellar disk in the main accretion phase. In addition, the mass accretion rate onto the protostar shows a strong time variability that is caused by the torque from the low-mass companions and/or the spiral arms in the circumstellar disk. Such variability provides an important signature for detecting the substellar mass companion in the circumstellar disk around very young protostars.

• OSTI ID: 21474497
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 724; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
EVOLUTION
GRAVITATIONAL INSTABILITY
INSTABILITY
MASS
PLASMA INSTABILITY
PROTOPLANETS
PROTOSTARS
SIMULATION
STAR EVOLUTION
STARS
THERMODYNAMICS
THREE-DIMENSIONAL CALCULATIONS