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The coldest molecular gas in our galaxy

Published online by Cambridge University Press:  14 August 2015

B. Zuckerman*
Affiliation:
University of Maryland

Extract

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Galactic CO emission surveys such as those carried out by Gordon and Burton (Ap. J., 208, 346, 1976) and references cited therein are sensitive only to CO with J = 1 → 0 excitation temperature ≳ 5 k “Cold” molecular (H2) gas with CO excitation temperature ≳ 5 k would go undetected in such surveys. Low Tex could be due to either low kinetic temperature or low H2 density. Evidence for the possible existence of substantial amounts of cold gas (Tex ∼ 3 K) towards the galactic center is apparent in spectra of Liszt et al. (Ap. J. 213, 38, 1977 and 198, 537, 1975) in the form of narrow gaps, suggestive of self-absorption, at velocities of 0, −30 and −55 km/s with respect to the LSR.

Type
V. PHYSICAL PROPERTIES OF THE INTERSTELLAR MEDIUM
Copyright
Copyright © Reidel 1979