The JCMT 12CO(3\u20132) survey of the Cygnus X region I. A pathfinder

Context. Cygnus X is one of the most complex areas in the sky, rich in massive stars; Cyg OB2 (2600 stars, 120 O stars) and other OB associations lie within its boundaries. This complicates interpretation, but also creates the opportunity to investigate accretion into molecular clouds and many subsequent stages of star formation, all within one small field of view. Understanding large complexes like Cygnus X is the key to understanding the dominant role that massive star complexes play in galaxies across the Universe. Aims. The main goal of this study is to establish feasibility of a high-resolution CO survey of the entire Cygnus X region by observing part of it as a pathfinder, and to evaluate the survey as a tool for investigating the star-formation process. We can investigate the mass accretion history of outflows, study interaction between star-forming regions and their cold environment, and examine triggered star formation around massive stars. Methods. A 2\ub0 7 4\ub0 area of the Cygnus X region has been mapped in the 12CO(3\u20132) line at an angular resolution of 15\u2032\u2032 and a velocity resolution of ~0.4 km s-\ub9 using HARP-B and ACSIS on the James Clerk Maxwell Telescope. The star formation process is heavily connected to the life-cycle of the molecular material in the interstellar medium. The high critical density of the 12CO(3\u20132) transition reveals clouds in key stages of molecule formation, and shows processes that turn a molecular cloud into a star. Results. We observed ~15% of Cygnus X, and demonstrated that a full survey would be feasible and rewarding. We detected three distinct layers of 12CO(3\u20132) emission, related to the Cygnus Rift (500\u2013800 pc), to W75N (1\u20131.8 kpc), and to DR 21 (1.5\u20132.5 kpc). Within the Cygnus Rift, H\u2009i self-absorption features are tightly correlated with faint diffuse CO emission, while HISA features in the DR 21 layer are mostly unrelated to any CO emission. 47 molecular outflows were detected in the pathfinder, 27 of them previously unknown. Sequentially triggered star formation is a widespread phenomenon.Peer reviewed: YesNRC publication: Ye