A composite large-scale CO survey at high galactic latitudes in the second quadrant

• Published in: Astronomy and astrophysics (Berlin) 1993-02, Vol.268 (1), p.265-275
• Main Authors: Heithausen, A., Stacy, J. G., De Vries, H. W., Mebold, U., Thaddeus, P.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Interstellar medium (ism) and nebulae in milky way; Molecular clouds, h2 clouds, dense clouds, and dark clouds; Stellar systems. Galactic and extragalactic objects and systems. The universe
• ISSN: 0004-6361; 1432-0746

Surveys undertaken in the 2nd quadrant of the Galaxy with the CfA 1.2 m telescope have been combined to produce a map covering about 620 sq deg in the 2.6 mm CO(J = 1 - 0) line at high galactic latitudes. There is CO emission from molecular 'cirrus' clouds in about 13 percent of the region surveyed. The CO clouds are grouped together into three major cloud complexes with 29 individual members. All clouds are associated with infrared emission at 100 micron, although there is no one-to-one correlation between the corresponding intensities. CO emission is detected in all bright and dark Lynds' nebulae cataloged in that region; however not all CO clouds are visible on optical photographs as reflection or absorption features. The clouds are probably local. At an adopted distance of 240 pc cloud sizes range from O.1 to 30 pc and cloud masses from 1 to 1600 solar masses. The molecular cirrus clouds contribute between 0.4 and 0.8 M solar mass/sq pc to the surface density of molecular gas in the galactic plane. Only 26 percent of the 'infrared-excess clouds' in the area surveyed actually show CO and about 2/3 of the clouds detected in CO do not show an infrared excess.