Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...430..786p&link_type=abstract
The Astrophysical Journal, vol. 430, no. 2, pt. 1, p. 786-799
Astronomy and Astrophysics
Astrophysics
18
Emission Spectra, Hydrogen, Infrared Spectra, Interstellar Matter, Line Spectra, Orion Nebula, Shock Waves, Astronomical Models, Astrophysics, Cosmology, Magnetohydrodynamics, Spectrum Analysis
Scientific paper
We present the results of observations of upsilon = 0 J = 3-1, 4-2, 5-3, 9-7, and 11-9 mid-infrared emission lines of H2 originating in the shock-excited region that surrounds BN-KL in Orion. Our data consist of velocity-resolved spectra and line intensities obtained at the positions of the two strongest H2 vibrational emission peaks. The profiles are single peaked, have line-center velocities very near that of the ambient molecular cloud (and consistent with emission from two lobes of a bipolar outflow whose axis is very nearly in the plane of the sky), and have widths of approximately 30 and approximately 50 km/s (FWHM), respectively, at the two locations. The emission in the line wings extends 50-100 km/s from line center. Our comparison of the wing emission of several lines argues against its originating from gas embedded within the outflow lobes. A persuasive explanation of the high-velocity wing emission remains elusive, however. We discuss our results in light of several shock models in the literature. The line intensities range from 10-3 to 10-2 ergs/s cm-2/sr, consistent with a two-shock model in which the low-J H2 emission originates from molecules (with T approximately 500 K and N(H2) approximately 4 x 1021/sq cm) reformed after passage of a hydrodynamic shock and the high-J H2 emission originates from molecules (with T approximately 2000 and N(H2) approximately 6 x 1019/sq cm in a magnetohydrodynamic shock. The thin dense shell of swept-up material separating the two shocks may be moving into a clumpy medium whose density contrast is approximately 100 and whose area-filling factor is approximately 0.2.
Aehtermann Jeffrey M.
Lacy John H.
Parma Parvinder S.
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