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Published online by Cambridge University Press: 25 September 2002
The results of FIR spectroscopic mapping observations of the Carina and Sharpless 171 regions with ISO/LWS and SWS are presented. Quite strong [SiII]35 μm emission has been detected in both regions. It is well correlated with [NII]122 μm emission, indicating that it originates mostly from low-density ionized gas. The ratio of the lines shows that S+ gasmust be more than 35% of the solar abundance in the ionized medium, suggesting clear observational evidence for the dust destruction in the interstellar medium. We have also found a small line ratio of [OI]63 μm to 145 μmlines (<10) in both regions. The observed large ratio as well as their spatial distribution cannot be accounted for by standard PDR models, even iftaking account of the pumping by ultraviolet radiation. We propose that [OI]63 μm line is absorbedin the cold gas between the line emitting region and us.