scholarly journals Measurement of Magnetic-Field Strengths in Molecular Clouds: Detection of OH Line Zeeman Splitting

1987 ◽  
Vol 115 ◽  
pp. 55-57
Author(s):  
I. Kazès ◽  
R. M. Crutcher ◽  
T. H. Troland
Keyword(s):  
Magnetic Field ◽  
Radio Telescope ◽  
Molecular Clouds ◽  
Stokes Parameter ◽  
Zeeman Splitting ◽  
Spectral Lines ◽  
First Results ◽  
Extended Program ◽  
Interstellar Molecular Clouds ◽  
Field Strengths

We report here the first results of an extended program to measure magnetic-field strengths in interstellar molecular clouds. The very large radio telescope located near Nancay, France, has been used to measure the Stokes-parameter I and V spectra of the 1665 and 1667 MHz lines of OH in emission and in absorption from extended (non-masing) molecular clouds. Signals in the V spectra are produced by Zeeman splitting of the spectral lines; we derive magnetic-field strengths or limits from these data.

scholarly journals Kinematics and Dynamics of Dense Clouds

1977 ◽  
Vol 75 ◽  
pp. 69-94
Author(s):  
James Lequeux
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Molecular Clouds ◽  
Kinematics And Dynamics ◽  
Interstellar Molecular Clouds ◽  
Maser Sources

Star formation is widely considered as resulting from the collapse of interstellar molecular clouds. The purpose of this paper is to review the observational evidences for collapse in dense clouds, and also for the factors which can play against collapse (turbulence, rotation, magnetic field). We shall also examine to which extent the maser sources (OH, H2O, SiO) can be related to star formation. An overlap with the review papers given by P. Thaddeus, P.G. Mezger, and to some extent by C.G. Wynn-Williams and L. Mestel appears unavoidable.

scholarly journals Hierarchical structure of the interstellar molecular clouds and star formation

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Alexander E. Dudorov ◽  
Sergey A. Khaibrakhmanov
Keyword(s):  
Magnetic Field ◽  
Molecular Clouds ◽  
Hierarchical Structures ◽  
Mhd Turbulence ◽  
Parallel Magnetic Field ◽  
Density Profiles ◽  
Statistical Correlations ◽  
Cloud Cores ◽  
Interstellar Molecular Clouds ◽  
The Magnetic Field

AbstractProperties of the hierarchical structures of interstellar molecular clouds are discussed. Particular attention is paid to the statistical correlations between velocity dispersion and size, and between the magnetic field strength and gas density. We investigate the formation of some hierarchical structures with the help of numerical MHD simulations using the ENLIL code. The simulations show that the interstellar molecular filaments with parallel magnetic field and molecular cores can form via the collapse and fragmentation of cylindrical molecular clouds. The parallelmagnetic field halts the radial collapse of the cylindrical cloud maintaining its nearly constant radius ~0.1 pc. The observed filaments with perpendicularmagnetic field can form as a result of themagnetostatic contraction of oblate molecular clouds under the action of Alfvén and MHD turbulence. The theoretical density profiles are fitted with the Plummer-like function and agree with observed profiles of the filaments in Gould’s Belt. The characteristics of molecular cloud cores found in our simulations are in agreement with observations.

scholarly journals New OH Zeeman Measurements of Magnetic Field Strengths in Molecular Clouds

2001 ◽  
Vol 554 (2) ◽  
pp. 916-932 ◽  
Author(s):  
Tyler L. Bourke ◽  
Philip C. Myers ◽  
Garry Robinson ◽  
A. R. Hyland
Keyword(s):  
Magnetic Field ◽  
Molecular Clouds ◽  
Field Strengths

scholarly journals A MERLIN study of 6 GHz excited OH & 6.7 GHz methanol masers in ON1

2007 ◽  
Vol 3 (S242) ◽  
pp. 188-189
Author(s):  
James A. Green ◽  
A. M. S. Richards ◽  
H. Flood ◽  
W. H. T. Vlemmings ◽  
R. J. Cohen
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Cross Correlation ◽  
Massive Star ◽  
Zeeman Splitting ◽  
Massive Star Formation ◽  
Star Formation Region ◽  
Formation Region ◽  
Methanol Masers ◽  
Field Strengths

AbstractMERLIN observations of 6.668-GHz Methanol and 6.035-GHz OH emission from the known massive star-formation region ON1 are presented. Maser components are found to lie at the southern edge of the UCHII with consistent polarization angles across the strongest features. Zeeman splitting of OH shows magnetic field strengths between +0.4 to −5.3 mG and from cross-correlation a tentative methanol magnetic field of −18mG is detected.

Fossil magnetic fields and rotation of early-type stars

1994 ◽  
Vol 162 ◽  
pp. 184-185
Author(s):  
A.E. Dudorov
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Main Sequence ◽  
Early Type ◽  
Main Sequence Stars ◽  
Early Type Stars ◽  
Quadrupole Magnetic Field ◽  
Interstellar Molecular Clouds

Observational data of the last 10 years allow two main conclusions:a) Main sequence stars can be separated in two classes: - magnetic (Bp) stars with surface strengths of a dipole or quadrupole magnetic field of Bs ≈ n · (102 − 103) G, n = 2,3,4…7, and - normal main sequence stars (F-O) with magnetic fields Bs ≈ 1 − 100 G (< 300 G);b) Typical star formation takes place in interstellar molecular clouds with magnetic field strengths B ≈ 10-5 G (See Dudorov 1990).

scholarly journals Observational Aspects of Magnetic Fields in Molecular Clouds

1990 ◽  
Vol 140 ◽  
pp. 293-300
Author(s):  
T. H. Troland
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Zeeman Effect ◽  
Growing Body ◽  
Field Strengths

A small but growing body of observational information now exists regarding magnetic field strengths in molecular regions. Most of these data come from study of the Zeeman effect in 18 cm OH lines. The field is strong enough in many such regions to be dynamically important.

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