Statistics – Computation
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21360407z&link_type=abstract
American Astronomical Society, AAS Meeting #213, #604.07
Statistics
Computation
Scientific paper
We have recently observed ubiquitous weak OH 1667 MHz line emission which appears to be coming from cold low-density molecular clouds in the ISM far from discrete IR sources. We examined both collisional and radiative excitation mechanisms as possible explanations for the appearance of this emission. Excitation computations were carried out using the MOLPOP program developed by Elitzur (Lockett & Elitzur, private comm.). The results show that the source of the excitation is not likely to be collisions, which produce too little emission if the densities really are as low as we suspect. The diffuse IR radiation which permeates our Galaxy is a likely alternative, leading to mild pumping of the OH molecule. This radiation would also pump molecules into higher rotational states, resulting in large enhancements of the 5 cm OH lines when compared to collisional excitation. Although still weak, detection of these lines may be possible, and would confirm our suggestion that IR pumping is the source of the ubiquitous 1667 emission we have observed earlier. We are planning a search for these 5 cm lines.
Allen Reeshemah
Rogers Alice
Weinreb Sander
Zheng Zheng
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