2012A&A...542L..22R

We used the dual-band receiver GREAT on board the SOFIA airborne telescope to perform observations of the [CII] 158µm fine-structure line at the postitions of two giant molecular clouds (GMC) in the center of IC 342 (GMCs C and E) and compared the spectra with corresponding ground-based data for low- and mid-J CO and [CI]. We performed model calculations assuming a clumpy photo-dissociation region (PDR) environment using the KOSMA-τ PDR model code to derive physical parameters of the local medium. The [CII] 158µm emission resembles the spectral signature of ground-based atomic and molecular lines, which indicates a common origin. The emission from GMC E can be decomposed into a cool, molecular component with weak far-ultraviolet (FUV) fields and low, mean densities of 10³cm^–3 and a strongly excited starburst/PDR region with higher densities of 10⁴cm^–3 and FUV intensities of 250-300 Draine fields. The emission from GMC C is consistent with gas densities of 5000cm^–3, FUV intensities of a few Draine fields and total gas masses of 20x10⁶M_☉. The high spectral resolution of the GREAT receiver allowed us to decompose the [CII] emission of the GMC E into a strongly excited gas component resembling a PDR/starburst environment and a quieter, less excited gas component and to analyze the different components within a single beam individually.