Characteristics of Collapse of Rotating Isothermal Clouds

Narita, Shinji; Hayashi, Chûshirô; Miyama, Shoken M.

doi:10.1143/ptp.72.1118

Cited by 42 publications

(37 citation statements)

References 10 publications

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“…The polar cap of the Ðrst shock is convex while that of the second shock is concave at the stage shown in Figure 1c. These shock fronts are also seen in the collapse of a rotating isothermal cloud (see, e.g., Norman, Wilson, & Barton 1980 ;Narita et al 1984 ;Matsumoto et al 1997).…”

Section: Resultsmentioning

confidence: 93%

“…Hunter (1977) extended the Larson-Penston similarity solution to describe the subsequent accretion phase. Narita et al (1984) found a similarity solution describing a dynamically collapsing rotating isothermal gas cloud. Saigo & Hanawa (1998) extended their similarity solution to describe the subsequent accretion phase.…”

mentioning

confidence: 99%

“…A gravitationally stable, magnetically supported (subcritical) cloud undergoes quasi-static contraction by ambipolar diffusion (see, e.g., Nakano 1979), while a gravitationally unstable (supercritical) cloud undergoes dynamical collapse (see, e.g., Shu, Adams, & Lizano 1987). In both cases the density as a function of radius, r, approaches o P r~2, and a protostar with very small mass forms (see Larson 1969 ;Narita, Hayashi, & Miyama 1984 ;Fiedler & Mouschovias 1993 ;Ciolek & Mouschovias 1994 ;Basu & Mouschovias 1994). Subsequently, the protostar grows in mass through accretion.…”

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confidence: 99%

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Collapse of Rotating Gas Clouds and Formation of Protostellar Disks: Effects of Temperature Change during Collapse

Saigo

Matsumoto

Hanawa

2000

ApJ

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We show two-dimensional numerical simulations of the gravitational collapse of rotating gas clouds. We assume the polytropic equation of state, P \ Koc, to take account of the temperature change during the collapse. Our numerical simulations have two model parameters, b and c, which specify the initial rotation velocity and polytropic index, respectively. We show three models, b \ 1.0, 0.5, and 0.2, for each c, which is taken to be 0.8, 0.9, 0.95, 1.05, 1.1, or 1.2. These 18 models are compared with previously reported isothermal models (c \ 1). In each model a rotating cylindrical cloud initially in equilibrium fragments periodically because of the growth of a velocity perturbation and forms cloud cores. The cloud core becomes a dynamically collapsing gaseous disk whose central density increases with time (t) inThis collapse is qualitatively similar in density and velocity distributions o c P (t [ t 0 )~2. to the runaway collapse of a rotating isothermal cloud. The surface density of the disk, &, is proportional to the power of the radial distance, &(r) P r1~2c, in the envelope. Models with c [ 1 have geometrically thick disks (aspect ratio while those with c \ 1 have very thin disks While. the former disks are stable, the latter disks are unstable against fragmentation if we adopt the Toomre stability criterion for a thin gaseous disk. Our numerical simulations also show the growth of a rotationally supported disk by radial accretion in a period for models with c [ 1. The accretion phase t [ t 0 starts at a stage in which the central density is still Ðnite. The central density at the beginning of the accretion phase is lower when b and c are larger. Our models with c \ 1 are applicable to star formation in turbulent gas clouds in which the e †ective sound speed decreases with increase in the density. Our models with c [ 1 are applicable to star formation in primordial clouds in which the temperature increase during the collapse is due to less efficient cooling.

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Section: Resultsmentioning

confidence: 93%

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confidence: 99%

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confidence: 99%

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Collapse of Rotating Gas Clouds and Formation of Protostellar Disks: Effects of Temperature Change during Collapse

Saigo

Matsumoto

Hanawa

2000

ApJ

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“…The disk structure is almost the same as that of two-dimensional numerical simulations (e.g., Matsumoto et al 1997) ; the disk collapses while oscillating. Although the amplitude of the oscillation is appreciable, the average disk structure is well reproduced by a similarity solution of Narita, Miyama, & Hayashi (1984) and Saigo & Hanawa (1998). The angular velocity, ), is nearly constant near the center, and the rotation velocity, is nearly constant in the outer disk.…”

Section: Nonaxisymmetric Rotationmentioning

confidence: 84%

Bar and Disk Formation in Gravitationally Collapsing Clouds: Implications for Binary Formation

Matsumoto

Hanawa

1999

ApJ

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We investigated the dynamical collapse of a molecular cloud core with three-dimensional numerical simulations. Our simulations show that an initially spherical core produces a bar or disk during its dynamical collapse. The disk and bar formation is due to instability. Velocity perturbations grow in proportion to where denotes the central density. The growing velocity perturbations are due to two o c 1@6, o c e †ects, rotation and shear. Rotation makes the core spin faster to produce a disk at the center. On the other hand, velocity shear elongates or shortens the core in one direction to form a bar or nonrotating disk. When the core rotates nonuniformly, the collapse produces a disk containing a bar at its center by the growth of rotation and shear. This bar is much longer than the Jeans length and is likely to be unstable against fragmentation. We expect that the bar will evolve into a binary or multiple stars. The binary or multiple stars will be surrounded by a common disk. We also demonstrate the growth of an eigenmode that leads to bar and disk formation. On the basis of our numerical simulations, we give a condition for formation of a disk and bar during the isothermal collapse phase of a molecular cloud core. If the core has an oblateness of 10% or an equivalent velocity shear at cm~3, the core n H2^1 04 produces a bar by the end of its isothermal collapse phase.

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“…Calculations of axisymmetric collapse with rotation show that a central density singularity develops even if the angular momentum of each fluid element is conserved (Norman et al 1980;Narita et al 1984;Matsumoto et al 1997). However, this central density singularity can develop into a star only if most of the angular momentum of the gas orbiting around it is removed.…”

Section: Transport Processes In Collapsing Cloudsmentioning

confidence: 99%

Angular momentum and the formation of stars and black holes

Larson

2009

Rep. Prog. Phys.

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Abstract.The formation of compact objects like stars and black holes is strongly constrained by the requirement that nearly all of the initial angular momentum of the diffuse material from which they form must be removed or redistributed during the formation process. The mechanisms that may be involved and their implications are discussed for (1) low-mass stars, most of which probably form in binary or multiple systems; (2) massive stars, which typically form in clusters; and (3) supermassive black holes that form in galactic nuclei. It is suggested that in all cases, gravitational interactions with other stars or mass concentrations in a forming system play an important role in redistributing angular momentum and thereby enabling the formation of a compact object. If this is true, the formation of stars and black holes must be a more complex, dynamic, and chaotic process than in standard models. The gravitational interactions that redistribute angular momentum tend to couple the mass of a forming object to the mass of the system, and this may have important implications for mass ratios in binaries, the upper stellar IMF in clusters, and the masses of supermassive black holes in galaxies.

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Characteristics of Collapse of Rotating Isothermal Clouds

Cited by 42 publications

References 10 publications

Collapse of Rotating Gas Clouds and Formation of Protostellar Disks: Effects of Temperature Change during Collapse

Collapse of Rotating Gas Clouds and Formation of Protostellar Disks: Effects of Temperature Change during Collapse

Bar and Disk Formation in Gravitationally Collapsing Clouds: Implications for Binary Formation

Angular momentum and the formation of stars and black holes

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