High-accuracy estimation of magnetic field strength in the interstellar medium from dust polarization

Abstract

Dust polarization is a powerful tool for studying the magnetic field properties in the interstellar medium (ISM). However, it does not provide a direct measurement of its strength. Different methods havebeen developed which employ both polarization and spectroscopic data in order to infer the field strength. The most widely applied methods have been developed by Davis (1951), Chandrasekhar & Fermi (1953) (DCF), Hildebrand et al. (2009) and Houde et al.(2009) (HH09). They rely on the assumption that isotropic turbulent motions initiate the propagation of Alvfén waves. Observations,however, indicate that turbulence in the ISM is anisotropic and non-Alfvénic (compressible) modes may be important. Our goal is to develop a new method for estimating the field strength in the ISM, which includes the compressible modes and does not contradict the anisotropic properties of turbulence. We use simple energetics arguments that take into account the compressible modes to estimate the strength of the magnetic field. We derive the following equation: $B_0=\sqrt{2\pi \rho }\delta v/\sqrt{\delta \theta }$, where $\rho$ is the gas density, $\delta v$ is the rms velocity as derived from the spread of emission lines, and $\delta \theta$ is the dispersion of polarization angles. We produce synthetic observations from 3D MHD simulationsand we assess the accuracy of our method by comparing the true field strength with the estimates derived from our equation. We find a mean relative deviation of $17\%$. The accuracy of our method does not depend on the turbulence properties of the simulated model. In contrast DCF and HH09 systematically overestimate the field strength. HH09 produces accurate results only for simulations with high sonic Mach numbers.

arXiv commentAccepted for publication to Astronomy & Astrophysics

References in corpus (54)

• Density, Velocity, and Magnetic Field Structure in Turbulent Molecular Cloud Models
• Simulations of Incompressible MHD Turbulence
• Compressible Magnetohydrodynamic Turbulence: mode coupling, scaling relations, anisotropy, new regime and astrophysical implications
• MHD Turbulence Revisited
• Large-Scale Structure of the Molecular Gas in Taurus Revealed by High Linear Dynamic Range Spectral Line Mapping
• Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds
• Magnetic Fields in the Formation of Sun-Like Stars
• Compressible Sub-Alfvenic MHD turbulence in Low-beta Plasmas
• Compressible MHD Turbulence in Interstellar Plasmas
• Dispersion of Magnetic Fields in Molecular Clouds. I
• An Imprint of Molecular Cloud Magnetization in the Morphology of the Dust Polarized Emission
• On the Spectrum of Magnetohydrodynamic Turbulence
• Dispersion of Magnetic Fields in Molecular Clouds. II
• Magnetically Aligned HI Fibers and the Rolling Hough Transform
• Magnetic Fields in High-Mass Infrared Dark Clouds
• Studies of regular and random magnetic fields in the ISM: statistics of polarization vectors and the Chandrasekhar-Fermi technique
• Density Studies of MHD Interstellar Turbulence: Statistical Moments, Correlations and Bispectrum
• Dynamic Alignment in Driven Magnetohydrodynamic Turbulence
• Magnetic Field Diagnostics Based on Far-Infrared Polarimetry: Tests Using Numerical Simulations
• The Millennium Arecibo 21-cm Absorption Line Survey. I. Techniques and Gaussian Fits
• Theoretical Models of Polarized Dust Emission from Protostellar Cores
• Magnetic field amplification in turbulent astrophysical plasmas
• The JCMT BISTRO Survey: The magnetic field strength in the Orion A filament
• Observational Constraints on the Ages of Molecular Clouds and the Star-Formation Timescale: Ambipolar-Diffusion--Controlled or Turbulence-Induced Star Formation?
• Magnetically Aligned Velocity Anisotropy in the Taurus Molecular Cloud
• The Turbulent Warm Ionized Medium: Emission Measure Distribution and MHD Simulations
• Interferometric observations of magnetic fields in forming stars
• The Generation of Magnetic Fields Through Driven Turbulence
• HAWC+/SOFIA Multiwavelength Polarimetric Observations of OMC-1
• Detailed Interstellar Polarimetric Properties of the Pipe Nebula at Core Scales
• Submillimeter and Far-Infrared Polarimetric Observations of Magnetic Fields in Star-Forming Regions
• On the use of fractional Brownian motion simulations to determine the 3D statistical properties of interstellar gas
• Gravity, Magnetic Field, and Turbulence: Relative Importance and Impact on Fragmentation in the Infrared Dark Cloud G34.43+00.24
• The structure and statistics of interstellar turbulence
• Critical Balance and the Physics of MHD Turbulence
• The magnetic field and dust filaments in the Polaris Flare
• A technique for constraining the driving scale of turbulence and a modified Chandrasekhar-Fermi method
• Magnetic field morphology in nearby molecular clouds as revealed by starlight and submillimetre polarization
• Nonlinear Hydromagnetic Wave Support of a Stratified Molecular Cloud
• Characterizing Magnetized Turbulence in M51
• Optical polarization map of the Polaris Flare with RoboPol
• Magnetic Seismology of Interstellar Gas Clouds: Unveiling a Hidden Dimension
• Striations in molecular clouds: Streamers or MHD waves?
• Magnetic field fluctuations in anisotropic, supersonic turbulence
• Evaluating the Magnetic Field Strength in Molecular Clouds
• Filaments and striations: anisotropies in observed, supersonic, highly-magnetised turbulent clouds
• Developing the 3-Point Correlation Function For the Turbulent Interstellar Medium
• The Galactic Magnetic Field's Effect in Star-Forming Region
• An Imprint of the Galactic Magnetic Field in the Diffuse Unpolarized Dust Emission
• The driving scale -- density decorrelation scale relation in a turbulent medium
• Tracing the Magnetic Field of IRDC G028.23$-$00.19 Using NIR Polarimetry
• The Catalogue for Astrophysical Turbulence Simulations (CATS)
• Irregular Magnetic Fields and the Far-Infrared Polarimetry of Dust Emission from Interstellar Clouds
• Characterization of Turbulence from Submillimeter Dust Emission

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• Magnetic Fields in Massive Star-Forming Regions (MagMaR) II. Tomography Through Dust and Molecular Line Polarization in NGC 6334I(N)
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• Multi-scale physical properties of NGC 6334 as revealed by local relative orientations between magnetic fields, density gradients, velocity gradients, and gravity
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• Formation of the SDC13 Hub-Filament System: A Cloud-Cloud Collision Imprinted on The Multiscale Magnetic Field
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• Aspect ratios of far-infrared and H i filaments in the diffuse interstellar medium at high Galactic latitudes
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• Analytic characterization of sub-Alfvénic turbulence energetics
• A multi-scale view of the magnetic field morphology in the hot molecular core G31.41+0.31
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• Non-parametric Bayesian reconstruction of Galactic magnetic fields using Information Field Theory: The inclusion of line-of-sight information in ultra-high energy cosmic ray backtracking
• Why take the square root? An assessment of interstellar magnetic field strength estimation methods
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• What does it mean to take the mean? The effect of the averaging scale on the characterization of interstellar turbulence
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• Probing Polarization and the Role of Magnetic Fields in Cloud Destruction in the Keyhole Nebula
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