The first ISO workshop on analytical spectroscopy with SWS, LWS, PHT-S and CAM-CVF

(Oct 6-8, 1997, Madrid, Spain)

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PDR Modeling of the LWS Fine Structure Lines in Ultraluminous Galaxies

M.L. Luhman 1 - S. Satyapal 2 - J. Fischer1 - M.G. Wolfire 3


1 Naval Research Laboratory, Washington, DC, USA -
2 Goddard Space Flight Center, Greenbelt, MD, USA -
3 University of Maryland, College Park, MD, USA

We compare ISO LWS observations of the [CII] 158 $\mu$m and, where observed, the [OI] 63 and 146 $\mu$m fine-structure lines in a sample of ultraluminous infrared galaxies (ULIGs) to the results of recent theoretical models of extragalactic photodissociation regions (PDRs). The PDR models are up-to-date versions of those of Wolfire, Tielens, & Hollenbach (1990), which include, among other things, the photoelectric heating effects of small grains/PAHs. Applying the models to Arp 299, we address the PDR origin of the fine-structure lines and the physical properties of the PDR component. In our sample of ULIGs, the [CII] line flux is ~ 10% of that found in normal and starburst galaxies in the local universe. We use the PDR models, along with the results of photoionization models, to address possible origins for the [CII] deficit.



 
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