[Oi] 63 Micron Emission from High‐ and Low‐Luminosity Active Galactic Nucleus Galaxies

The Infrared Space Observatory was used to search for a tracer of the warmand dense neutral interstellar medium, the [O I] 63.18 micron line, in fourultraluminous IRAS sources lying at redshifts between 0.6 and 1.4. While thesesources are quasars, their infrared continuum emission suggests a substantialinterstellar medium. No [O I] flux was securely detected after probing down toa 3 sigma sensitivity level sufficient for detecting line emission instarbursts with similar continuum emission. However, if the detection thresholdis slightly relaxed, one target is detected with 2.7 sigma significance. Forthis radio-quiet quasar there is likely a substantial dense and warminterstellar medium; the upper limits for the three radio-loud sources do notpreclude the same conclusion. Using a new, uniformly-processed database of theISO extragalactic far-infrared spectroscopy observations, it is shown thatnearby Seyfert galaxies typically have higher [O I]-to-far-infrared ratios thando normal star-forming galaxies, so the lack of strong [O I] 63 micron emissionfrom these high-redshift ultraluminous sources cannot be attributed to theiractive cores.Comment: 18 pages including 4 figures; accepted for publication in the Astrophysical Journa