Far-infrared spectra of the NGC 2024 region

We present the ISO-LWS spectra (45-200 mum) of the molecular cloud NGC2024 and its associated HII region. We observed the two class 0 FIR3 and FIRE 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 J(up)=17 to J(up)=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 similar to 100 K and a density similar to 10(6) cm(-3). Column densities in excess of 10(18) cm(-2) are derived from this molecular component. An [OI] 63 mum/[OI] 145 mum line ratio of about 5 is found across all the region, indicating that the 63 pm 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.