Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aas...185.9701l&link_type=abstract
American Astronomical Society, 185th AAS Meeting, #97.01; Bulletin of the American Astronomical Society, Vol. 26, p.1477
Astronomy and Astrophysics
Astronomy
Scientific paper
We have detected extremely extended (>1.5deg , or 12 pc) near-infrared H_2 line emission from the Orion A giant molecular cloud. We have used a new instrument, the University of Texas Near-Infrared Fabry-Perot spectrometer, which is optimized for the detection of low surface brightness line emission from 1.4 microns to 2.4 microns (Luhman et al. 1995, PASP, in press). Our Orion observations show that we can directly trace H_2 along the outlying surfaces of interstellar molecular clouds, well away from the star-forming cores. The diffuse, extended H_2 emission provides a unique new view of molecular clouds to complement conventional large-scale tracers such as CO and is an excellent probe of cloud energetics. In Orion, we have mapped the emission in the 1.601 microns v=6--4 Q(1), 2.121 microns v=1--0 S(1), and 2.247 microns v=2--1 S(1) lines of H_2. The surface brightness of the extended H_2 line emission is 10(-6) to 10(-5) ergs s(-1) cm(-2) sr(-1) . Based on the distribution and relative strengths of the H_2 emission lines, we conclude that H_2 excited by ultraviolet radiation dominates the global H_2 line emission from the Orion molecular cloud, even though this cloud has a powerful shock-excited H_2 source in its core. We are comparing our H_2 data and observations of the 63 microns [O I] and 158 microns [C II] emission to the predictions of theoretical models of photodissociation or photon dominated regions to examine the physical conditions throughout the Orion A cloud. This work was supported by the David and Lucile Packard Foundation through a fellowship to D.T.J. and by a NASA Graduate Traineeship grant NGT-50998 held by M.L.L.
Jaffe Daniel T.
Luhman Michael L.
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