The nature of the molecular line wing emission in the Rosette Molecular Complex

We present (CO)-C-12 and (CO)-C-13 J = 3 --> 2 and J = 2 --> 1 observations of the Rosette Molecular Complex. The observations show that broad line wings, originally observed in CO J = 1 --> 0, also exist in the higher J lines in high signal-to-noise ratio spectra toward individual positions and in positionally averaged spectra. We show that the wing emission can be explained by the superposition of individual high- and low-velocity clumps, some of which are spatially resolved at high angular resolution, and at least two embedded outflow sources. Our results call in question an earlier interpretation of this weak line wing emission as originating from a low-density, ubiquitous, molecular interclump gas. A multiline analysis implies that the wing emission originates in gas with densities comparable to the density of the bulk emission, We note that the physical conditions derived from this relatively simple single-component excitation analysis do not give a fully consistent picture of these clumps, leaving any conclusion on their dynamical state and evolution rather speculative.