Evidence for Dynamically Important Magnetic Fields in Molecular Clouds

Abstract

Recent observational evidence that magnetic fields are dynamically important in molecular clouds, compared to self-gravity and turbulence, is reviewed and illustrated with data from the NGC 2024 region. One piece of evidence, turbulence anisotropy, was found in the diffuse envelope of a cloud (Av~1; Heyer et al. 2008); our data further suggests turbulence anisotropy in the cloud (Av >7) and even near the cloud core (Av~100). The data also shows that magnetic fields can channel gravitational contraction even for a region with super-critical N(H2)/2Blos ratio (the ratio between the observed column density and two times the line-of-sight observed field strength), a parameter which has been widely used by observers to estimate core mass-to-flux ratios. Although the mass-to-flux ratio is constant under the flux-freezing condition, we show that N(H2)/2Blos grows with time if gravitational contraction is anisotropic due to magnetic fields.

accepted by MNRAS

References in corpus (16)

• Theory of Star Formation
• Magnetic Fields in the Formation of Sun-Like Stars
• Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations
• Studies of regular and random magnetic fields in the ISM: statistics of polarization vectors and the Chandrasekhar-Fermi technique
• Magnetically Regulated Star Formation in 3D: The Case of Taurus Molecular Cloud Complex
• The effect of magnetic fields on star cluster formation
• Magnetically Aligned Velocity Anisotropy in the Taurus Molecular Cloud
• The Five College Radio Astronomy Observatory CO Mapping Survey of the Taurus Molecular Cloud
• Optical polarimetry toward the Pipe nebula: Revealing the importance of the magnetic field
• Detailed Interstellar Polarimetric Properties of the Pipe Nebula at Core Scales
• Probing the Turbulence Dissipation Range and Magnetic Field Strengths in Molecular Clouds
• Results of SPARO 2003: Mapping Magnetic Fields in Giant Molecular Clouds
• Molecular line mapping of the giant molecular cloud associated with RCW 106 - III. Multi-molecular line mapping
• Oscillations of starless cores
• Dichotomy in the Dynamical Status of Massive Cores in Orion
• Molecular Line Profiles from a Core Forming in a Turbulent Cloud

Cited by in corpus (15)

• Magnetic field amplification in turbulent astrophysical plasmas
• The Link between Magnetic Fields and Filamentary Clouds: Bimodal Cloud Orientations in the Gould Belt
• Magnetized Interstellar Molecular Clouds. I. Comparison Between Simulations and Zeeman Observations
• The alignment of molecular cloud magnetic fields with the spiral arms in M33
• Protostellar Outflow Heating in a Growing Massive Protocluster
• The Formation of Stellar Clusters in Magnetized, Filamentary Infrared Dark Clouds
• On the Initial Conditions for Star Formation and the IMF
• Magnetized interstellar molecular clouds: II. The Large-Scale Structure and Dynamics of Filamentary Molecular Clouds
• Compression of turbulent magnetized gas in Giant Molecular Clouds
• The relative orientation between local magnetic field and Galactic plane in low latitude dark clouds
• The Role of Magnetic Fields in the Stability and Fragmentation of Filamentary Molecular Clouds: Two Case Studies at OMC-3 and OMC-4
• Quantifying the interplay between gravity and magnetic field in molecular clouds - a possible multi-scale energy equipartition in NGC6334
• Core orientations and magnetic fields in isolated molecular clouds
• CN Zeeman observations of the NGC 2264-C protocluster
• Tracing the magnetic field morphology of the LDN 1172/1174 cloud complex