ISO spectroscopic observations of Carina region

The Carina Nebula region ( l ∼ 287° and b ∼ −0.6°) of about 20′ × 40′ has been observed by ISO/LWS with the spatial separation of 3′. Several emission lines, such as [OI] 63, 145 μ m, [OIII] 52, 88 μ m, [NIII] 57 μ m, [NII] 122 μ m and [CII] 157 μ m have been detected in the spectra of most observed positions. The LWS observations of the ionic lines indicate the presence of very low electron density gas ( n e −3 ) extended over the Galactic plane in a scale of kpc unambiguously for the first time.