2007A&A...474..873S

The distance to the wellknown bipolar nebula S106 and its associated molecular cloud is highly uncertain. Values between 0.5 and 2kpc are given in the literature, favoring a view of S106 as an isolated object at a distance of 600pc as part of the ``Great Cygnus Rift''. However, there is evidence that S106 is physically associated with the Cygnus X complex at a distance of ∼1.7kpc (Schneider et al., 2006A&A...458..855). In this case, S106 is a more massive and more luminous star forming site than previously thought. We aim to understand the large-scale distribution of molecular gas in the S106 region, its possible association with other clouds in the Cygnus X south region, and the impact of UV radiation on the gas. This will constrain the distance to S106. We employ a part of an extended ¹³CO and C¹⁸O 1-0 survey, performed with the FCRAO, and data from the MSX and Spitzer satellites to study the spatial distribution and correlation of molecular cloud/PDR interfaces in Cygnus X south. The 2MASS survey is used to obtain a stellar density map of the region. We find evidence that several molecular clouds including S106 are directly shaped by the UV radiation from members of several Cygnus OB clusters, mainly NGC 6913, and are thus located at a distance of ∼1.7kpc in the Cygnus X complex. The definition of OB associations in terms of spatial extent and stellar content in the Cygnus X south region is revised.