On the Role of Disks in the Formation of Stellar Systems: A Numerical Parameter Study of Rapid Accretion

• Published in: The Astrophysical journal Vol. 708; no. 2; pp. 1585 - 1597
• Main Authors: Kratter, Kaitlin M, Matzner, Christopher D, Krumholz, Mark R, Klein, Richard I
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 10.01.2010; IOP
• Subjects: ACCRETION DISKS; Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Earth, ocean, space; EVOLUTION; Exact sciences and technology; GRAVITATIONAL INSTABILITY; INSTABILITY; MASS; MULTIPLICITY; PLASMA INSTABILITY; STAR ACCRETION; STAR EVOLUTION; STARS; TORQUE; stars: formation; Accretion; Star formation; Low-mass stars; Brown dwarf stars; accretion, accretion disks; Digital simulation; binaries: general; Accretion disks; stars: low-mass, brown dwarfs; Stellar systems
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/708/2/1585

We study rapidly accreting, gravitationally unstable disks with a series of idealized global, numerical experiments using the code ORION. Our numerical parameter study focuses on protostellar disks, showing that one can predict disk behavior and the multiplicity of the accreting star system as a function of two dimensionless parameters which compare the infall rate to the disk sound speed and orbital period. Although gravitational instabilities become strong, we find that fragmentation into binary or multiple systems occurs only when material falls in several times more rapidly than the canonical isothermal limit. The disk-to-star accretion rate is proportional to the infall rate and governed by gravitational torques generated by low-m spiral modes. We also confirm the existence of a maximum stable disk mass: disks that exceed ~50% of the total system mass are subject to fragmentation and the subsequent formation of binary companions.