Astronomy and Astrophysics Letters dedicated to ISO

H2 infrared line emission from S 140: a warm PDR.

Timmermann R., Bertoldi F., Wright C.M., Drapatz S., Draine B.T., Haser L., Sternberg A.


SO SWS spectra of H2 pure rotational and ro-vibrational transitions, as well as [FeII], and [SiII] fine structure lines were obtained for one position on the photodissociation region (PDR) adjacent to the bright rim of the S 140 HII region. The gas density is =~104cm-3 and the incident UV flux {chi}=~400 at the location of the ionization front. Our PDR model analysis shows that the relative H2 line intensities are characteristic of low-density fluorescent emission and that the gas temperature is T>500K in the partially dissociated gas. A comparison of predicted and observed fine structure line intensities permits an estimate of the abundances of Fe and Si.

ISM: individual: S 140 (SH 2-140) - reflection nebulae - molecules - abundances - HII regions - infrared: ISM: lines and bands

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