Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21721606w&link_type=abstract
American Astronomical Society, AAS Meeting #217, #216.06; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We present a fully sampled map covering the Orion Hot Core and dense molecular ridge, in the sub-millimeter J=6-5 rotational transition of 13CO, made at 0.45 mm with an angular resolution of 13” and velocity resolution of 0.5 km s-1. The map covers 3’ (north-south) by 2’ (east-west). The profile centered on the Hot Core peaks at 8.5 km s-1, with a peak intensity of 40 K, corrected antenna temperature. This profile shows line wings extending to 30 km s-1, and to -20 km s-1. From a map of the intensity integrated from 0 to +18 km s-1, there is a prominent maximum within 5” of the center of the Orion Hot Core. The Full Width to Half Power (FWHP) of this maximum is 37", considerably larger than regions containing complex molecules. Single dish measurements of lines from the J=2-1 or J=1-0 transitions of CO isotopes show no such distinct maximum. If the 13CO line is optically thin and the level populations are thermalized at 150 K, the column density for velocities between 0 to +18 km s-1 is N(13CO )=3.3 1017 cm-2. Using the local 12C to 13C ratio, 76, the column density of CO is N(CO)=2.6 1019 cm-2. When combined with published dust emission data, the CO/ H2 ratio is 9 10-6. This is more than a factor of 10 lower than the canonical value of 10-4. For the Orion South source and Orion Ridge region, the column density of CO is <25% of that found for the Hot Core but the CO/ H2 ratios are similar. Models of Photodissociation Regions, PDR's, predict that CO lines from PDR's are only marginally optically thick. Thus the intensities of such 13CO lines would be below our sensitivity, so our map traces warm and dense molecular gas rather than PDR's.
Dumke Michael
Henkel Carsten
Kawamura Jonathan
Muders Dirk
Wilson Thomas L.
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