A Survey of Magnetic Field Strengths in the Envelopes of Molecular Clouds via the 18 cm OH Zeeman Effect

Abstract

We present the results of an extensive Arecibo observational survey of magnetic field strengths in the inter-core regions of molecular clouds to determine their role in the evolution and collapse of molecular clouds as a whole. Sensitive 18 cm OH Zeeman observations of absorption lines from Galactic molecular gas in the direction of extragalactic continuum sources yielded 38 independent measurements of magnetic field strengths. Zeeman detections were achieved at the three sigma level toward 9 clouds, while the others revealed sensitive upper limits to the magnetic field strength. Our results suggest that total field strengths in the inter-core regions of GMCs are about 15 microgauss.

arXiv comment26 pages, 2 tables, 20 figures. Accepted for publication in ApJ. The complete set of figures will be published only electronically

References in corpus (11)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Control of star formation by supersonic turbulence
• The Millennium Arecibo 21-CM Absorption Line Survey. II. Properties of the Warm and Cold Neutral Media
• Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey
• The Millennium Arecibo 21-cm Absorption Line Survey. IV. Statistics of Magnetic Field, Column Density, and Turbulence
• Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations
• The Millennium Arecibo 21-cm Absorption Line Survey. I. Techniques and Gaussian Fits
• New OH Zeeman measurements of magnetic field strengths in molecular clouds
• The Dense Gas Mass Fraction of Molecular Clouds in the Milky Way
• Where is OH and Does It Trace the Dark Molecular Gas (DMG)?
• VLA OH Zeeman Observations of the star forming region S88B

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• Cloud Properties and Correlations with Star Formation in Numerical Simulations of the Three-Phase ISM
• HAWC+/SOFIA Polarimetry in L1688: Relative Orientation of Magnetic Field and Elongated Cloud Structure
• The sub-critical illusion: synthetic Zeeman effect observations from galactic zoom-in simulations
• Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457
• GNOMES II: Analysis of the Galactic diffuse molecular ISM in all four ground state hydroxyl transitions using Amoeba
• Fitting an Analytic Magnetic Field to a Prestellar Core
• Are Stellar Embryos in Perseus Radio-Synchrotron Emitters? Statistical data analysis with Herschel and LOFAR paving the way for the SKA