Different Modes of Star Formation: Gravitational Collapse of Magnetically Subcritical Cloud

Abstract

Star formation in magnetically subcritical clouds is investigated using a three-dimensional non-ideal magneto-hydrodynamics simulation. Since rapid cloud collapse is suppressed until the magnetic flux is sufficiently removed from the initially magnetically subcritical cloud by ambipolar diffusion, it takes > 5-10t_ff to form a protostar, where t_ff is the freefall timescale of the initial cloud. The angular momentum of the star forming cloud is efficiently transferred to the interstellar medium before the rapid collapse begins, and the collapsing cloud has a very low angular momentum. Unlike the magnetically supercritical case, no large-scale low-velocity outflow appears in such a collapsing cloud due to the short lifetime of the first core. Following protostar formation, a very weak high-velocity jet, which has a small momentum and might disappear at a later time, is driven near the protostar, while the circumstellar disc does not grow during the early mass accretion phase. The results show that the star formation process in magnetically subcritical clouds is qualitatively different from that in magnetically supercritical clouds.

49 pages, 17 figures, accepted for publication in MNRAS

References in corpus (12)

• Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations
• Formation of a Keplerian disk in the infalling envelope around L1527 IRS: transformation from infalling motions to Kepler motions
• Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Non-Ideal Magnetohydrodynamic Effects and Early Formation of Circumstellar Disks
• Signs of Early-Stage Disk Growth Revealed with ALMA
• Magnetic Fields and Rotations of Protostars
• Effects of Ohmic and ambipolar diffusion on the formation and evolution of the first cores, protostars and circumstellar discs
• The ALMA view of the protostellar system HH212 - The wind, the cavity, and the disk
• ALMA Results of the Pseudodisk, Rotating disk, and Jet in Continuum and HCO+ in the Protostellar System HH 212
• Evolution of Rotating Molecular Cloud Core with Oblique Magnetic Field
• Exposed Long-lifetime First-core: A New Model of First Cores Based on Radiation Hydrodynamics
• Observations of Infalling and Rotational Motions on a 1,000-AU Scale around 17 Class 0 and 0/I Protostars: Hints of Disk Growth and Magnetic Braking?
• Protostellar Jets Enclosed by Low-velocity Outflows

Cited by in corpus (11)

• The First Two Thousand Years of Star Formation
• Formation and evolution of protostellar accretion discs. II. From 3D simulation to a simple semi-analytic model of Class 0/I discs
• Misalignment of Magnetic Fields, Outflows and Discs in Star-forming Clouds
• The impact of non-ideal magnetohydrodynamic processes on discs, outflows, counter-rotation and magnetic walls during the early stages of star formation
• On the origin of magnetic fields in stars II: The effect of numerical resolution
• Dust coagulation and fragmentation in a collapsing cloud core and their influence on non-ideal magnetohydrodynamic effects
• Investigating the role of magnetic fields in star formation using molecular line profiles
• The initial magnetic criticality of prestellar cores
• Driving Conditions of Protostellar Outflows in Different Star-Forming Environments
• Complex structure of a proto-brown dwarf
• Discovery of Asymmetric Spike-like Structures of the 10 au Disk around the Very Low-luminosity Protostar Embedded in the Taurus Dense Core MC 27/L1521F with ALMA