The Rosette Molecular Complex I. CO observations

We present 12CO,13CO and C18O J=1→0, and 12CO and 13CO 2→1 and 3→2 observations of the Rosette Molecular Complex (RMC), obtained with the KOSMA 3m and IRAM 30m telescopes. We introduce a method for correcting error beam pick-up of single-dish telescopes in spectral line radio maps by using observations of a smaller telescope and apply it to correct the IRAM 30m data presented in this paper by the large scale KOSMA 3m data. The observations indicate that the RMC is clumpy on a size scale of down to at least 0.1 pc. The molecular density structure is well correlated with the optical picture in the Hα line emission. From a CO multiline analysis, incorporating the incident UV field, we derive a density of lower than 105 cm−3 for the emitting gas at a beam filling factor of unity. In direction to the molecular outflow source AFGL 961, we find that the 12CO lines up to J=3→2 have broad wings. They show, as well as the 13CO J=2→1 and 1→0 lines, self-absorption features due to colder forground material. A second outflow is firstly detected close to the embedded IR source IR06314+0427. The KOSMA and IRAM 13CO J=2→1 data were analyzed with the clump finding algorithm ’Gaussclumps’. Appropriate scaling shows that the small scale clump mass distribution overlaps and continues the low mass end of the large scale distribution. The observed structures are therefore self-similar over a length scale covering at least 0.1 to a few parsec. The clump mass spectral index α for both individual data sets and the combined distribution equals 1.6, in good agreement with typical values for other molecular clouds. The molecular clumps were classified using the ’Initial Cloud Parameter Space’ of Bertoldi & McKee (1989). All clumps belong to the regime of ’Post Implosion Clouds’ and possibly form stars.