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Tracing the Magnetic Field in Orion AWe use extensive 350 micron polarimetry and continuum maps obtained with Hertz and SHARC II along with HCN and HCO(sup +) spectroscopic data to trace the orientation of the magnetic field in the Orion A star-forming region. Using the polarimetry data, we find that the direction of the projection of the magnetic field in the plane of the sky relative to the orientation of the integral-shaped filament varies considerably as one moves from north to south. While in IRAS 05327-0457 and OMC-3 MMS 1-6 the projection of the field is primarily perpendicular to the filament it becomes better aligned with it at OMC-3 MMS 8-9 and well aligned with it at OMC-2 FIR 6. The OMC-2 FIR 4 cloud, located between the last two, is a peculiar object where we find almost no polarization. There is a relatively sharp boundary within its core where two adjacent regions exhibiting differing polarization angles merge. The projected angle of the field is more complicated in OMC-1 where it exhibits smooth variations in its orientation across the face of this massive complex. We also note that while the relative orientation of the projected angle of the magnetic field to the filament varies significantly in the OMC-3 and OMC-2 regions, its orientation relative to a fixed position on the sky shows much more stability. This suggests that, perhaps, the orientation of the field is relatively unaffected by the mass condensations present in these parts of the molecular cloud. By combining the polarimetry and spectroscopic data we were able to measure a set of average d u e s for the inclination angle of the magnetic field relative to the line of sight. We find that the field is oriented quite close to the plane of the sky in most places. More precisely, the inclination of the magnetic field is approx. = 73 deg around OMC-3 MMS 6, approx. = 74 deg at OMC-3 MMS 8-9, approx. = 80 deg at OMC-2 FIR 4, approx. = 65 deg in the northeastern part of OMC-1, and approx. = 49 deg in the Bas. The small difference in the inclination of the field between OMC-3 and OMC-2 seems to strengthen the idea that the orientation of the magnetic field is relatively unaffected by the agglomeration of matter located in these regions. We also present polarimetry data for the OMC-4 region located some 13 min. south of OMC-1.
Document ID
20040030554
Acquisition Source
Headquarters
Document Type
Preprint (Draft being sent to journal)
Authors
Dowell, C. Darren
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Hildebrand, Roger H.
(Chicago Univ. Chicago, IL, United States)
Dotson, Jessie L.
(NASA Ames Research Center Moffett Field, CA, United States)
Vaillancourt, John E.
(Wisconsin Univ. Madison, WI, United States)
Phillips, Thomas G.
(California Inst. of Tech. Pasadena, CA, United States)
Peng, Rui-Sheng
(Submillimeter Observatory Hilo, HI, United States)
Bastien, Pierre
(Montreal Univ. Quebec, Canada)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Astrophysics
Report/Patent Number
Rept-2003-4
Funding Number(s)
CONTRACT_GRANT: NSF AST-02-04886
CONTRACT_GRANT: NSF AST-99-87441
CONTRACT_GRANT: NSF AST-99-80846
Distribution Limits
Public
Copyright
Public Use Permitted.
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