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Paper: HI and OH Zeeman Observations toward Orion's Veil
Volume: 343, Astronomical Polarimetry: Current Status and Future Directions
Page: 183
Authors: Brogan, C.L.; Troland, T.H.; Abel, N.P.; Goss, W.M.; Crutcher, R.M.
Abstract: We present new Very Large Array Hi and OH Zeeman observations toward Orion A with 2500 and 4500 resolution, respectively. Significant Zeeman line of sight magnetic fields are detected toward much of the Orion A continuum in two distinct velocity components. The measured field strengths range from ∼ −50 μG near the Trapezium region to ∼ −300 μG toward the ‘Dark Bay’. Line of sight field strengths of ∼ −250 βG are also measured from OH absorption lines toward the ‘Dark Bay’ region. From optical extinction and UV absorption lines it is clear that the Hi and OH absorption arises from a “veil” of primarily neutral gas that covers much of the Orion A source. Photoionization models suggest that the Veil is located 1-3 pc in front of the Trapezium and has an average density of 103.1 cm−3. At this density the magnetic field energy dominates the energy of nonthermal motions or gravity. Therefore, Orion's Veil is the first interstellar environment where magnetic dominance appears to exist.
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