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The sub-mm J=5-6 line of 13CO in Orion

Wednesday, November 10th, 2010- 4:00pm

CCU Lecture Series, National Radio Astronomy Observatory, Charlottesville

 

Thomas L. Wilson

Naval Research Laboratory

E-mail: tom.wilson@nrl.navy.mil

 

Biography

 

Thomas Wilson graduated with a BS in Physics from St. Joseph’s College in Philadelphia and went on to study under B. F. Burke at MIT for his doctoral work in physics, which focused on ‘Radio Studies of HII Regions.’ After graduating from MIT, Wilson was a post-doctoral fellow at the NRAO in Charlottesville. Afterward Wilson was on staff at Max-Planck-Inst. f. Radioastronomy from 1969-2004, then Project Scientist (2004-6), Associate Director (2006-8) and at European Southern Observatory, Director of the Sub-mm Telescope Observatory (1997-2002), and subsequently Senior Scientist at ALMA (Atacama Large Mm/sub-mm Array) (Feb 2009 to March 2010). As of April 2010, he is the Branch Head at the Naval Research Laboratory. His publications include 300+ papers and a book entitled the "Tools of Radio Astronomy."

Abstract

 

A fully sampled map covering the Orion Hot Core and dense molecular ridge, in the sub-millimeter J=6-5 rotational transition of 13CO, at 0.45 mm with a resolution of 13” is presented. The map covers 3’ by 2’. The profile centered on the Hot Core peaks at 8.5 km s-1 and has a peak intensity of 40 K, corrected antenna temperature.  It shows line wings from 30 km s-1 to -20 km s-1. The map of intensity, integrated from 0 to +18 km s-1, shows a maximum <5” from the center of the Orion Hot Core. The FWHP is 37”, larger than the 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. Correcting for t=1.5 in the J=6-5 line of  13CO, and assuming that  the  level populations are thermalized at 150 K, the beam averaged column density between 0 to +18 km s-1 is N(13CO )=3.8 · 1017 cm-2 and N(CO)=2.9 · 1019 cm-2. When combined with published dust emission data, the CO/H2 number ratio is 10-5, a factor of 10 lower than the canonical value, 10-4.  For the Orion South and Orion Ridge region, the CO/H2 ratios are similar.