A uniform CO survey of the molecular clouds in Orion and Monoceros

We report the results of a new large scale survey of the Orion-Monoceros complex of molecular clouds made in the J = 1 -> 0 line of ¹²CO with the Harvard-Smithsonian 1.2 m millimetre-wave telescope. The survey consists of 52 288 uniformly spaced spectra that cover an area of 432 deg² on the sky and represent the most sensitive large-scale survey of the region to date. Distances to the constituent molecular clouds of the complex, estimated from an analysis of foreground and background stars, have provided information on the three dimensional structure of the entire complex.