Orion B - anatomy of a star-forming region
The compact HII region/molecular cloud Orion B was observed with the VLA in the radio continuum and OH absorption line at a frequency of 1667 MHz, in the near-infrared continuum and H{sub 2} emission line at a wavelength of 2 {mu}m, and in several millimeter-wavelength molecular transitions (of HCO{sup +}, SO, H{sup 13}CN, and HC{sup 15}N) with the Hat Creek Array. The VLA continuum map has an integrated flux density of 59 {+-} 2 Jy, and the author estimates that the total flux density is 63 {+-} 4 Jy at this frequency. This map reveals two spectacular filamentary loops just north of a very sharp, although resolved, ionization front (IF). In OH absorption maps, the eastern loop (EL) shows up near the velocity of the Zeeman-split OH in such a way as to suggest expansion, and a high optical depth cloud appears in the north Central part of the nebula at the velocity of the main OH absorption. The infrared source IRS 2, with a strong stellar wind and a location within the EL, is deduced to be the cause of this loop. The IR observations reveal many new sources which together may supply the missing ionizing flux for the nebula. The IF is traced by the H{sub 2} line emission. In the dense molecular core the HCO{sup +} line maps show a centrally located broad line region with an elliptical velocity distribution, a long, quiescent, NS-oriented ridge, an EW ridge which exactly abuts the IF of the adjacent HII region, and a possible one-sided high density outflow to the south with an origin apparently not near any of the IR sources mentioned above. An improved model and a suggested history for the HII region and the first detailed model for the molecular core are presented.
- Research Organization:
- Illinois Univ., Urbana, IL (USA)
- OSTI ID:
- 6597176
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
COSMIC GASES
COSMIC RADIO SOURCES
DENSITY
ELECTROMAGNETIC RADIATION
FLUIDS
FLUX DENSITY
GASES
H2 REGIONS
INFRARED RADIATION
INTERSTELLAR SPACE
MAPS
MATHEMATICAL MODELS
MOLECULES
MORPHOLOGY
NEAR INFRARED RADIATION
NEBULAE
ORIGIN
PHYSICAL PROPERTIES
RADIATIONS
RADIOWAVE RADIATION
SPACE
SPECTRA
VELOCITY