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Dame, T.M., and P. Thaddeus, 1985: A wide-latitude CO survey of molecular clouds in the northern Milky Way. Astrophys. J., 297, 751-765, doi:10.1086/163573.
Molecular clouds in the galactic quadrant from l = 12°-100° were surveyed in the 115.271 GHz line of CO at an angular resolution of 1°. In galactic longitude the survey extends from b = -5° to +6°, with extensions to higher latitude between l = 20° and 60°. CO line emission, detected from 50% of the region surveyed, comes nearly equally from local clouds associated with the Great Rift in the Milky Way and from distant clouds in the inner arms of the Galaxy 4-7 kpc from the galactic center. Using the CO radial velocities, it was possible to resolve the Rift into 10 molecular clouds 200-2300 pc away, to associate many of these with optical objects (dark nebulae, OB associations, etc.), and to determine distances and masses. The nearby clouds of the Rift system have masses between a few times 104 and a few times 105 M☉, not large with respect to the largest clouds or cloud complexes found elsewhere in the galaxy; they are conspicuous mainly because they are close. The mean half-thickness at half-intensity of local molecular gas is estimated to be 75±25 pc, in agreement with that obtained at the solar circle by other CO surveys, and the mean molecular density at midplane is 0.013 M☉/pc3. The correlation between the integrated CO line intensity and optical onscuration throughout the region of the survey is close, demonstrating that nearly all dark nebulae are molecular clouds, and vice versa.
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