Far-infrared spectra of the NGC 2024 region

Giannini, T.; Nisini, B.; Lorenzotti, D.; Spinoglio, L.; di Giorgio, A. M.; Benedettini, M.; Saraceno, P.; Smith, H. A. and White, G. J. (2000). Far-infrared spectra of the NGC 2024 region. In: Star Formation From The Small To The Large Scale. ESLAB Symposium 33, 2-5 Nov 1999, Noordwijk, The Netherlands.

URL: http://adsabs.harvard.edu/full/2000ESASP.445..373G


We present the ISO-LWS spectra (45-200 μm) of the molecular cloud NGC2024 and its associated H II region. We observed the two class 0 FIR3 and FIR5 and the infrared source IRS2. All the spectra appear quite similar, all showing, at approximately the same intensity level, the high-J CO rotational lines (from Jup=17 to Jup=14), and several atomic and ionic lines from Oxygen, Carbon and Nitrogen. The molecular emission has been fitted with a Large Velocity Gradient model, and results originating in an extended and clumpy PDR with a temperature ~ 100 K and a density ~ 106 cm-3. Column densities in excess of 1018 cm-2 are derived from this molecular component. an [OI] 63 μm/[OI] 145 μm line ratio of about 5 is found across all the region, indicating that the 63 μm line is strongly absorbed by a cold foreground gas along the line of sight. From the intensity ratios of the ionic lines relevant physical properties of the ionized gas (N/O abundance, electron density) are derived and compared with those of other galactic H II regions.

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