Aperture synthesis observations of the 21 centimeter Zeeman effect toward Orion A

Journal Article · Wed Feb 01 04:00:00 EST 1989 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/167107· OSTI ID:6141864

Troland, T H; Heiles, C; Goss, W M

The VLA has been used to map the 21 cm Zeeman effect at 40 arcsec resolution in the absorbing H I gas in front of Orion A. Two such regions exist having typical velocities of 1 and 5 km/s; both almost certainly lie close to the H II region. Field strengths exceed 100 micro G in this H I gas. The field in the higher velocity component has been reliably detected across most of the continuum source. No field reversals exist. The distribution of line-of-sight field strengths derived for this component mimics that of tau(H I) for positions where the lines are not saturated, suggesting that the mass-to-flux ratio in this gas is approximately constant. The distribution of visual extinction across Orion A using existing radio and optical data is rederived. Maxima and minima of extinction are generally coincident with maxima and minima of magnetic field. This correspondence suggests that the observed association between field strength and tau(H I) is a real column density effect, that the effect encompasses all neutral gas in front of the source, and that the mass-to-flux ratio for this neutral gas is approximately constant. Results for Orion A lend weight to the conclusion that magnetic fields play a crucial role in the dynamics of interstellar material. 48 references.

• Research Organization: Kentucky Univ., Lexington (USA); California Univ., Berkeley (USA); National Radio Astronomy Observatory, Socorro, NM (USA); Groningen, Rijksuniversiteit (Netherlands)
• OSTI ID: 6141864
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 337; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
COSMIC GASES
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
FLUIDS
GASES
H1 REGIONS
H2 REGIONS
INTERSTELLAR MAGNETIC FIELDS
MAGNETIC FIELDS
MASS
NEBULAE
RADIATIONS
RADIOWAVE RADIATION
VELOCITY
ZEEMAN EFFECT