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Session 105 - Galaxies: Counts & Kinematics.
Display session, Saturday, January 10
Exhibit Hall,
We present Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) spectra of the [CII] 158 \mum fine structure line in a sample of ultraluminous infrared galaxies (L_IR > 10^12 L_ødot; ULIGs). The observed [CII] 158 \mum line radiation represents some of the weakest extragalactic [CII] emission yet observed. Relative to the far-infrared continuum, the [CII] line flux in the observed ULIGs is \sim10% of that seen in nearby normal and starburst galaxies. We use recent theoretical models of photodissociation and photoionization regions, along with ISO LWS spectra of other fine structure lines, to address possible origins of the [CII] deficit. We discuss the implications of this study on the use of [CII] as a future probe of high redshift protogalaxies.