Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?

Abstract

Abridged. A large fraction of stars are found in binary systems. It is therefore important for our understanding of the star formation process, to investigate the fragmentation of dense molecular cores. We study the influence of the magnetic field, ideally coupled to the gas, on the fragmentation in multiple systems of collapsing cores. We present high resolution numerical simulations performed with the RAMSES MHD code starting with a uniform sphere in solid body rotation and a uniform magnetic field parallel to the rotation axis. We pay particular attention to the strength of the magnetic field and interpret the results using the analysis presented in a companion paper. The results depend much on the amplitude, $A$, of the perturbations seeded initially. For a low amplitude, $A=0.1$, we find that for values of the mass-to-flux over critical mass-to-flux ratio, $\mu$, as high as $\mu =20$, the centrifugally supported disk which fragments in the hydrodynamical case, is stabilized and remains axisymmetric. Detailed investigations reveals that this is due to the rapid growth of the toroidal magnetic field induced by the differential motions within the disk. For values of $\mu$ smaller $\simeq 5$, corresponding to larger magnetic intensities, there is no centrifugally supported disk because of magnetic braking. When the amplitude of the perturbation is equal to $A=0.5$, each initial peak develops independently and the core fragments for a large range of $\mu$. Only for values of $\mu$ close to 1 is the magnetic field able to prevent the fragmentation. Since a large fraction of stars are binaries, the results of low magnetic intensities preventing the fragmentation in case of weak perturbations, is problematic. We discuss three possible mechanisms...

Accepted for publication in A&A

References in corpus (4)

• A High Order Godunov Scheme with Constrained Transport and Adaptive Mesh Refinement for Astrophysical MHD
• Magnetic processes in a collapsing dense core. I Accretion and Ejection
• The impact of magnetic fields on single and binary star formation
• Probing the formation of intermediate- to high-mass stars in protoclusters II. Comparison between millimeter interferometric observations of NGC 2264-C and SPH simulations of a collapsing clump

Cited by in corpus (9)

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• Magnetic processes in a collapsing dense core. I Accretion and Ejection
• The Importance of Radiative Feedback for the Stellar Initial Mass Function
• Magnetic Braking and Protostellar Disk Formation: The Ideal MHD Limit
• Numerical simulations of compressively driven interstellar turbulence: I. Isothermal gas
• The effect of magnetic fields on star cluster formation
• Formation Scenario for Wide and Close Binary Systems
• Magneto-Hydrodynamics of Population III Star Formation
• The influence of magnetic fields on the thermodynamics of primordial star formation