AAS 195th Meeting, January 2000
Session 72. ISM: Neutral Gas
Display, Friday, January 14, 2000, 9:20am-6:30pm, Grand Hall

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[72.05] The FIR emission lines in NGC6946 and NGC1313

A. Contursi, J. Brauher, G. Helou, N. Silbermann, S. Malhotra, D. Dale (IPAC)

We present ISO--LWS FIR observations in the CII (158 \mum) and OI (63 \mum) emission lines of the starbusrt galaxy NGC6946 and the irregular galaxy NGC1313. For both galaxies full maps at 158\mum are available. The CII emission peaks on the central regions and the spiral arms, traced also by the MIR emission at 7 and 15 \mum, but a diffuse extended emission, probably associated with the atomic gas, is also present. The CII/FIR, CII/(7\mum) and CII/(15\mum) ratios as a function of the IRAS (60/100\mum) ratio, tracer of heating intensity, are presented and compared to the same ratios derived from the integrated emission of 60 more distant normal galaxies (Malhotra et al. 1998, 1999). The trends in the integrated emission plots and in the spatially resolved plots are quite similar. The CII/FIR and the CII/(15\mum) ratios decrease as the systems become more active whereas the CII/(7\mum) stays quite constant. This is interpreted in terms of differences in the coupling of the gas with different grains populations. The relation between FIR emission lines and other gas components (CO and HI) is also investigated and compared to the PDRs models. We thus derive the ISM main parameters (n,G0) for nuclear, spiral arms and diffuse emission in both galaxies and we establish that no more than the 30% of the CII emission comes from the diffuse atomic medium. This work was supported by ISO data analysis funding from the National Aeronautics and Space Administration and carried out at the Infrared Processing and Analysis Center and the Jet Propulsion Laboratory of the California Institute of Technology. ISO is an ESA project with instruments funded by ESA member states (specially the PI countries: France, Germany, the Netherlands, and the UK) with the partecipation of ISAS and NASA.

The author(s) of this abstract have provided an email address for comments about the abstract: contursi@ipac.caltech.edu

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