OMC-1: a cool arching filament in a hot gaseous cavity: geometry, kinematics, magnetic vectors, and pressure balance.
VALLEE J.P. and FIEGE J.D.
Abstract (from CDS):
We have assembled data on large (Galactic shell), middle (filament), and small (protostar) scales. OMC-1 is embedded in a hot cavity. Here we have made multiconstituent (gas/dust/field) homogeneous maps of the central part of the OMC-1 filament, covering an area of 2'x2'. We find here that the vertical filament has a turbulent pressure about equal to the magnetic pressure; its total pressure roughly equals that in the surrounding medium. The magnetic field crosses the filament with an estimated strength of 300-350 µG in the sky plane. It could be an ``externally wrapped'' U-shaped magnetic field going around the filament (due to a large shock front traveling in the cavity), or else an internally generated ``helical'' field (of unknown origin). Near the OMC-1 map center, we map the low-velocity outflow near IRc2-source I, with a pattern of blue south-southwest gas and red north-northeast gas. Our James Clerk Maxwell Telescope data yield a plane-of-sky field of 2.4-2.6 mG across the outflow; this strength nearly equals the published Zeeman line-of-sight data. Farther out, the Zeeman data show a negative magnetic field, possibly suggesting a pole-on dipolar field.
ISM: Dust, Extinction - Infrared: ISM - ISM: Magnetic Fields - Polarization - Stars: Formation