FQS. Galactic Plane CO survey

The clouds are grouped in three main structures corresponding to the Local, Perseus, and Outer arms up to a distance of ~8.6kpc from the Sun. This is the first self-consistent statistical catalogue of molecular clouds of the outer Galaxy obtained with a subarcminute spatial resolution and therefore able to detect not only the classical giant molecular clouds, but also the small clouds and to resolve the cloud structure at the sub-parsec scale up to a distance of a few kiloparsec.

We found two classes of objects: structures with sizes above a few parsecs that are typical molecular clouds and may be self-gravitating, and subparsec structures that cannot be in gravitational equilibrium and are likely transient or confined by external pressure. We used the ratio between the Herschel H2 column density and the integrated intensity of the CO lines to calculate the CO conversion factor and we found mean values of (3.3+/-1.4)x10^20^cm^-2^/(K.km/s) and (1.2+/-0.4)x10^21^cm^-2^/(K.km/s), for ^12^CO (1-0) and ^13^CO (1-0), respectively.

FQS contributes to the general effort in producing a new generation of high-quality spectroscopic data for the Galactic Plane in the less studied third Galactic Quadrant, toward the outer Galaxy. FQS has produced a data-set of great legacy value, largely improving the data quality both in terms of sensitivity and spatial resolution over previous data sets.