A composite CO survey of the entire Milky Way

Abstract

Large-scale CO surveys of the entire Galactic plane and specific nearby clouds have been combined to produce a panorama of the entire Milky Way in molecular clouds at an angular resolution of 1/2°. Covering 10° - 20° in latitude at all longitudes and all or nearly all large, nearby clouds at higher latitude, the composite survey is the only molecular line survey to date with sky coverage and resolution comparable to that of the early 21 cm surveys. The inner Galaxy spiral arms produce, as expected, a thin, intense ridge of emission along the Galactic plane within ≡60° of the Galactic center. The local emission shows the same large-scale features as the distribution of dark clouds. The survey provides a thorough inventory of large molecular clouds near the Sun. The overall distribution of clouds within 1 kpc is consistent with the Sun lying near the inner edge of a local spiral arm or spur. The half-thickness at half-intensity of the local molecular cloud layer is 87 pc.