L204 - A gravitationally confined dark cloud in a strong magnetic environment

Abstract

view Abstract Citations (55) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS L204: A Gravitationally Confined Dark Cloud in a Strong Magnetic Environment Heiles, Carl Abstract L204 is a filamentary dark cloud located in the H I expanding shell associated with the North Polar Spur. The magnetic field strength in the surrounding H I has beem measured from Zeeman splitting of the 21 cm line. The average line-of-sight component of magnetic field, B(parallel), in the H I is 4.2 micro-G. Using the observed tendency for B(parallel) and the H I velocity to correlate, it is argued that variations in B(parallel) result primarily from projection effects, that the total field strength in the H I is about 12 micro-G, and that magnetic pressure dominates gas pressure. It is argued that Alfven waves might be responsible for the observed tendency for B(parallel) and the H I line width to be anticorrelated. The field strength in the molecular portion of L204 itself is estimated, and it is argued that the small enhancement found within the dense filament is consistent with theoretical expectation. Magnetic braking should have occurred for the component of rotation perpendicular to the magnetic field. Publication: The Astrophysical Journal Pub Date: January 1988 DOI: 10.1086/165897 Bibcode: 1988ApJ...324..321H Keywords: Astronomical Spectroscopy; Dark Matter; Gravitational Effects; Hydrogen Clouds; Interstellar Magnetic Fields; Nebulae; Centimeter Waves; Radio Sources (Astronomy); Spectral Line Width; Spectrum Analysis; Zeeman Effect; Astrophysics; INTERSTELLAR: MAGNETIC FIELDS; NEBULAE: INDIVIDUAL ALPHANUMERIC: L204 (LYNDS 204); RADIO SOURCES: 21 CM RADIATION; ZEEMAN EFFECT full text sources ADS | data products SIMBAD (1)