Molecular clouds in the extreme outer galaxy

Abstract

view Abstract Citations (83) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Molecular Clouds in the Extreme Outer Galaxy Digel, S. ; de Geus, E. ; Thaddeus, P. Abstract We present observation of 11 molecular clouds with kinematic Galactocentric distances of 18-28 kpc. The most distant is approximately 10 kpc farther from the Galactic center than any previously known and apparently lies beyond the edge of the optical disk. All are associated with much larger H I concentrations, with typical offsets of approximately 40 pc from the H I peaks. CO observations with the CfA 1.2 m and National Radio Astronomy Observatory (NRAO) 12 m telescopes indicate typical sizes of 20-40 pc, velocity widths of 1-3 km/s, and kinetic temperatures of 10-25 K. They apparently have lower CO luminosities than clouds near the solar circle with similar properties. Some may have associated infrared sources, but owing to the great distances of the clouds, the only general conclusion that can be made about star formation is that stars earlier than B1 are absent. The apparent scarcity of clouds like these indicates that their contribution to the mass of the ISM beyond R = 18 kpc is not significant. Publication: The Astrophysical Journal Pub Date: February 1994 DOI: 10.1086/173706 Bibcode: 1994ApJ...422...92D Keywords: Carbon Monoxide; Distance; H I Regions; Interstellar Matter; Light Emission; Molecular Clouds; Radio Astronomy; Star Formation; Stellar Temperature; Astronomical Maps; Astronomical Observatories; Radio Telescopes; Astrophysics; GALAXY: STRUCTURE; ISM: CLOUDS; ISM: MOLECULES full text sources ADS | data products SIMBAD (23)