[CII] gas in IC 342
Abstract
We used the dual-band receiver GREAT on board the SOFIA airborne telescope to perform observations of the [C II] 158 μm 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 [C I]. 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 [C II] 158 μm 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 103 cm-3 and a strongly excited starburst/PDR region with higher densities of 104 cm-3 and FUV intensities of 250-300 Draine fields. The emission from GMC C is consistent with gas densities of 5000 cm-3, FUV intensities of a few Draine fields and total gas masses of 20 × 106 M⊙. The high spectral resolution of the GREAT receiver allowed us to decompose the [C II] 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2012
- DOI:
- 10.1051/0004-6361/201218935
- arXiv:
- arXiv:1204.2099
- Bibcode:
- 2012A&A...542L..22R
- Keywords:
-
- galaxies: ISM;
- galaxies: individual: IC 342;
- radio lines: galaxies;
- radio lines: ISM;
- ISM: atoms;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 4 pages, 2 figures, accepted by A&