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Astron. Astrophys. 315, L281-L284 (1996)

H2 infrared line emission from S140: a warm PDR*

R. Timmermann1, F. Bertoldi1, C.M. Wright1, S. Drapatz1, B.T. Draine2, L. Haser1, and A. Sternberg3

1 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, D-85740 Garching, Germany
2 Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA
3 School of Physics and Astronomy, Tel Aviv University, Ramat Aviv 69978, Israel

Received 15 July 1996 / Accepted 7 August 1996

Abstract. ISO SWS spectra of 2 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 S140 HII region. The gas density is img3.gif and the incident UV flux img4.gif 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.

Key words: ISM: individual: S140 - reflection nebulae - molecules - abundances - HII regions - infrared: ISM: lines and bands

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the United Kingdom) and with the participation of ISAS and NASA. The SWS is a joint project of SRON and MPE.

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Last change: December 16, 1996
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