The Milky Way in Molecular Clouds: A New Complete CO Survey

TLDR

The authors combine 32 CO surveys, including new large‑scale data, to create a comprehensive composite CO map of the entire Milky Way. The composite survey contains 488,000 spectra sampled at Nyquist or beamwidth resolution across a 4–10° latitude strip of the Galactic plane and higher‑latitude clouds, with each component survey integrated via clipping or moment masking to produce low‑noise spatial and longitude‑velocity maps. Compared with Dame et al.

Abstract

New large-scale CO surveys of the first and second Galactic quadrants and the nearby molecular cloud complexes in Orion and Taurus, obtained with the CfA 1.2 m telescope, have been combined with 31 other surveys obtained over the past two decades with that instrument and a similar telescope on Cerro Tololo in Chile, to produce a new composite CO survey of the entire Milky Way. The survey consists of 488,000 spectra that Nyquist or beamwidth ( °) sample the entire Galactic plane over a strip 4°-10° wide in latitude, and beamwidth or ° sample nearly all large local clouds at higher latitudes. Compared with the previous composite CO survey of Dame et al. (1987), the new survey has 16 times more spectra, up to 3.4 times higher angular resolution, and up to 10 times higher sensitivity per unit solid angle. Each of the component surveys was integrated individually using clipping or moment masking to produce composite spatial and longitude-velocity maps of the Galaxy that display nearly all of the statistically significant emission in each survey but little noise.