Collapse and Fragmentation Models of Tidally Interacting Molecular Cloud Cores. IV. Initial Slow Rotation and Magnetic Field Support

Sigalotti, Leonardo Di G.; Klapp, Jaime

doi:10.1086/308480

Cited by 9 publications

(9 citation statements)

References 53 publications

(65 reference statements)

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“…Thus, in a more complete theoretical calculation, magnetic fields must be taken into account. As shown by Sigalotti & Klapp (2005), it is expected that one of the main effects of magnetic fields would be to slow down the collapse of the dense core.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

The gravitational collapse of Plummer protostellar clouds

Arreaga‐García¹,

Klapp-Escribano²,

Gómez-Ramírez³

2010

A&A

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The growing observational evidence that main-sequence and pre-main-sequence protostars are found in binary and multiple systems suggests that they are formed by a fragmentation of collapsing molecular cloud cores. In this paper we present the results of a set of numerical simulations aimed to study the gravitational collapse and fragmentation of a centrally condensed cloud with a nearly flat central density region and a surrounding gas envelope. In order to describe this cloud structure, we use the Plummer radial density profile which satisfies the observed fact that protostellar clouds have a flat central density profile in their innermost region. We consider the cloud to be made of molecular hydrogen and describe the thermodynamics with a single barotropic equation of state, which includes a critical density ρ crit as a unique free parameter that determines a thermodynamical change on the collapsing gas: from an isothermal to an adiabatic regime. In this paper we consider four different values for the initial radius R c of the cloud, ranging from 2675 to 19 913 AU. In the models, for each ratio R c /R 0 of the cloud to core radius, we use two critical density values: ρ crit = 5.0 × 10 −14 and 5.0 × 10 −12 gr cm −3 . When the adiabatic change regime starts earlier, we find interesting gas structures as a result of the collapse, although these structures are different according to the initial mass content of the envelope and the initial angular velocity of the cloud. When the thermodynamical change occurs later, i.e., for ρ crit = 5.0 × 10 −12 gr cm −3 , we observe that the previously found structure is almost erased to give place instead to a single clump of gas without any adorning spiral arms. In general, we find that as the extension of the envelope mass increases, the possibility of a model to produce a multiple system decreases. This is a result of the initial configuration of our models, namely that with bigger envelopes their cores have a lower ratio of rotational to gravitational energy β 0 , a lower ratio of thermal plus rotational to gravitational energy α 0 + β 0 , and a lower angular velocity Ω 0 , which induces a stronger collapse which in turn contributes to the destruction of the structure that is formed during the initial phases of the collapse. Thus in a sufficient quantity rotational energy is crucial for the fragmentation to occur and survive.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

The gravitational collapse of Plummer protostellar clouds

Arreaga‐García¹,

Klapp-Escribano²,

Gómez-Ramírez³

2010

A&A

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“…In the protostellar context, such strong fields may also be relevant for the problem of binary formation (cf. Sigalotti & Klapp 2000).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Stability of accretion discs threaded by a strong magnetic field

Stehle

Spruit

2001

Monthly Notices of the Royal Astronomical Society

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We study the stability of poloidal magnetic fields anchored in a thin accretion disc. The two-dimensional hydrodynamics in the disc plane is followed by a grid-based numerical simulation including the vertically integrated magnetic forces. The 3--dimensional magnetic field outside the disc is calculated in a potential field approximation from the magnetic flux density distribution in the disc. For uniformly rotating discs we confirm numerically the existence of the interchange instability as predicted by Spruit, Stehle & Papaloizou (1995). In agreement with predictions from the shearing sheet model, discs with Keplerian rotation are found to be stabilized by the shear, as long as the contribution of magnetic forces to support against gravity is small. When this support becomes significant, we find a global instability which transports angular momentum outward and allows mass to accrete inward. The instability takes the form of a $m=1$ rotating `crescent', reminiscent of the purely hydrodynamic nonlinear instability previously found in pressure-supported discs. A model where the initial surface mass density $\Sigma(r)$ and $B_{\mathrm{z}}(r)$ decrease with radius as power laws shows transient mass accretion during about 6 orbital periods, and settles into a state with surface density and field strength decreasing approximately exponentially with radius. We argue that this instability is likely to be the main angular momentum transport mechanism in discs with a poloidal magnetic field sufficiently strong to suppress magnetic turbulence. It may be especially relevant in jet-producing discs.Comment: MNRAS in press. 9 postscript figures included in text, 4 jpeg images included separatel

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“…(83)-(89) have only been performed in axisymmetry. However, some 3D fragmentation simulations [309][310][311] have begun to appear recently, which include the effects of magnetic support and ambipolar diffusion in an approximate fashion. In these calculations, the starting point of the evolution is provided by a magnetically stable (subcritical) condensation that results from adding a magnetic field pressure, B 2 /8π, to a reference state consisting of a thermally supercritical, rigidly rotating, Gaussian cloud core of prolate shape and central density ρ 0 .…”

Section: Fragmentation Models With Magnetic Fieldsmentioning

confidence: 99%

“…These models were subsequently extended to include the collapse of slowly rotating clouds by Boss 310 and Sigalotti and Klapp. 311 Boss 310 performed a set of calculations with either solid-body or differential rotation and varied β(1.2 × 10 −4 ≤ β ≤ 0.012). He found that such clouds can fragment into a binary protostar, provided that β > 0.01.…”

Section: Fragmentation Models With Magnetic Fieldsmentioning

confidence: 99%

Gravitational Collapse and Fragmentation of Molecular Cloud Cores

Sigalotti

Klapp

2001

Int. J. Mod. Phys. D

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The detected multiplicity of main-sequence and pre-main-sequence stars along with the emerging evidence for binary and multiple protostars, imply that stars may ultimately form by fragmentation of collapsing molecular cloud cores. These discoveries, coupled with recent observational knowledge of the structure of dense cloud cores and of the properties of young binary stars, provide serious constraints to the theory of star formation. Most theoretical progress in the field of star formation is largely based on numerical calculations of the early collapse and fragmentation of protostellar clouds. Although these models have been quite successful at predicting the formation of binary protostars, a direct comparison between theory and observations has not yet been established. The results of recent observations as well as of early and recent analytic and numerical models, on which the present theory of star formation is based, are reviewed here in a self-consistent manner. 115 Int. J. Mod. Phys. D 2001.10:115-211. Downloaded from www.worldscientific.com by CAMBRIDGE UNIVERSITY on 02/03/15. For personal use only. Int. J. Mod. Phys. D 2001.10:115-211. Downloaded from www.worldscientific.com by CAMBRIDGE UNIVERSITY on 02/03/15. For personal use only. a A typographical error occurs in Eq. (3.26) of Tohline, 99 where the numerical factor 3/4π in his expression for A(r i ) should be 3π/16 as correctly printed in Eq. (28) here. Int. J. Mod. Phys. D 2001.10:115-211. Downloaded from www.worldscientific.com by CAMBRIDGE UNIVERSITY on 02/03/15. For personal use only.

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Collapse and Fragmentation Models of Tidally Interacting Molecular Cloud Cores. IV. Initial Slow Rotation and Magnetic Field Support

Cited by 9 publications

References 53 publications

The gravitational collapse of Plummer protostellar clouds

The gravitational collapse of Plummer protostellar clouds

Stability of accretion discs threaded by a strong magnetic field

Gravitational Collapse and Fragmentation of Molecular Cloud Cores

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