The Super-Alfvénic Model of Molecular Clouds: Predictions for Zeeman Splitting Measurements

Abstract

We present synthetic OH Zeeman splitting measurements of a super-Alfvenic model of molecular clouds. We select dense cores from synthetic 13CO maps computed from the largest simulation to date of supersonic and super-Alfvenic turbulence. The synthetic Zeeman splitting measurements in the cores yield a relation between the magnetic field strength, B, and the column density, N, in good agreement with the observations. The large scatter in B at a fixed value of N is partly due to intrinsic variations in the magnetic field strength from core to core. We also compute the relative mass-to-flux ratio between the center of the cores and their envelopes, ${\mathcal{R}}_{\mu }$, and show that super-Alfvenic turbulence produces a significant scatter also in ${\mathcal{R}}_{\mu }$, including negative values (field reversal between core center and envelope). We find ${\mathcal{R}}_{\mu }<1$ for 70% of the cores, and ${\mathcal{R}}_{\mu }<0$ for 12%. Of the cores with $|B_{\mathrm{LOS}}|>10$ \muG, 81% have ${\mathcal{R}}_{\mu }<1$. These predictions of the super-Alfvenic model are in stark contrast to the ambipolar drift model of core formation, where only ${\mathcal{R}}_{\mu }>1$ is allowed.

4 pages, 6 figures, submitted to ApJL. Minor corrections and additions, updated references

References in corpus (2)

• Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations
• Two regimes of Turbulent Fragmentation and the stellar IMF from Primordial to Present Day Star Formation

Cited by in corpus (23)

• Comparing the statistics of interstellar turbulence in simulations and observations: Solenoidal versus compressive turbulence forcing
• The Star Formation Rate of Supersonic MHD Turbulence
• Supernova Driving. I. The Origin of Molecular Cloud Turbulence
• A Simple Law of Star Formation
• The Origin of Massive Stars: The Inertial-Inflow Model
• Comparing Numerical Methods for Isothermal Magnetized Supersonic Turbulence
• Self-similar Fragmentation Regulated by Magnetic Fields in a Massive Star Forming Filament
• Testing Magnetic Star Formation Theory
• Infall-Driven Protostellar Accretion and the Solution to the Luminosity Problem
• Accuracy of core mass estimates in simulated observations of dust emission
• Magnetized Interstellar Molecular Clouds. I. Comparison Between Simulations and Zeeman Observations
• Supernova Driving. IV. The Star Formation Rate of Molecular Clouds
• The stellar IMF from Isothermal MHD Turbulence
• Observational Diagnostics of Self-Gravitating MHD Turbulence in Giant Molecular Clouds
• Damping of Alfven waves by Turbulence and its Consequences: from Cosmic-Rays Streaming to Launching Winds
• Accretion and magnetic field morphology around Class 0 stage protostellar discs
• Hierarchical Structure of Magnetohydrodynamic Turbulence In Position-Position-Velocity Space
• Mass and Magnetic distributions in Self Gravitating Super Alfvenic Turbulence with AMR
• Testing Molecular-Cloud Fragmentation Theories: Self-Consistent Analysis of OH Zeeman Observations
• The Super-Alfvénic Model of Molecular Clouds: Predictions for Mass-to-Flux and Turbulent-to-Magnetic Energy Ratios
• A multi-shock model for the density variance of anisotropic, highly-magnetised, supersonic turbulence
• Radiative transfer on hierarchial grids
• Statistical analysis of the mass-to-flux ratio in turbulent cores: effects of magnetic field reversals and dynamo amplification