Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...442..208r&link_type=abstract
The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 442, no. 1, p. 208-227
Astronomy and Astrophysics
Astrophysics
33
H Ii Regions, Hydrogen Atoms, Hydroxyl Radicals, Interstellar Magnetic Fields, Molecular Clouds, Neutral Gases, Radio Observation, Shock Fronts, Absorption Spectra, Abundance, Magnetic Field Configurations, Magnetic Flux, Velocity Distribution, Zeeman Effect
Scientific paper
VLA Zeeman observations of absorption lines of neutral hydrogen (H I) and the hydroxyl radial (OH) have been carried out toward the bipolar outflow H II region S106 at a resolution of approximately 20 arcsec with an rms noise of approximately 3 mJy/beam. The results of the observations are interpreted in terms of a model for the absorption-line gas in which some of the OH and H I gas has been accelerated by the passage of a shock front and sone of the gas lies outside the shock front at the undisturbed velocity of the molecular cloud. Two distinct OH absorption features are due to gas associated with S106. One component, which is identified with the unshocked gas, is narrow (Delta nuFWHM = 1.2-2.9 km/s) and is observed at small negative velocities (nuLSR = -2.4 to -1.0 km/s). This component shows a large peak in opacity at the eastern edge of the H II region near a previously observed molecular cloud core; the H2 mass of this component is estimated to be approximately 13 solar mass. In addition, there is a wide (Delta nuFWHM = 3.7-8.2 km/s) OH velocity component at a higher negative velocity (nuLSR = -4.8 to -3.3 km/s) that is identified as shocked gas; the OH abundnace in both velocity components by a factor of approximately 5 relative to dark clouds; the ratio NOH/NH2 approximately = 4 x 10-7 and NOH/Anu approximately = 5 x 1014. This increase abundance is likely due to the penetration of UV photons into the molecular cloud resulting in enhanced OH formation. A line-of-sight magnetic field (Blos) has been determined for the two OH velocity components between +150 and +400 micro-G over the inner arcminute (0.18 pc) of the H II region. The most significant detection of Blos in OH was +400 +/- 23 micro-G about 0.5 arcmin (0.09 pc) northeast of the exciting source, IRS 4. Given simple assumptions about the geometry of the magnetic field and the mass distribution, the observed magnetic field appears to be near the critical value for magnetic support. Together with far-IR and submillimeter measurements of the direction of magnetic field in the plane of the sky, our Zeeman map suggests that the field may lie along the long axis of S106 at large scales and be twisted into a toroidal morphology near the central; star, IRS 4. One of the H I velocity components appears to originate in shocked gas near the ionization front. This H I gas has a high negative radial velocity nu(LSR) = -9.8 to -5.8 km/s). has a large line width Delta nuFWHM = 3.9 to 11.6 km/s), and is believed to be from socked gas associated with the outflow. Blos approximately = +70 +/- 12 micro-G for this velocity component near the center of the H II region. The small value of Blos determined for H I relative to OH may be due to a tangling of strong field near the ionization front on scales smaller than our synthesized beam size. A weak, narrow component with a velocity approximately -2 km/s is observed in the eastern portion of the source; this is probably unshocked H I in the molecular cloud. Blos in this unshocked component is estimated to be between +200 and +300 micro-G. The ratio NHI/NH2 approximately = 2 x 10-2 and 4 x 10-2 for the unshocked and shocked components, respectively.
Crutcher Richard M.
Roberts Daniel A.
Troland Thomas H.
No associations
LandOfFree
The distribution of molecular and neutral gas and magnetic fields near the bipolar H II region S106 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The distribution of molecular and neutral gas and magnetic fields near the bipolar H II region S106, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The distribution of molecular and neutral gas and magnetic fields near the bipolar H II region S106 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-884958