[O I] 63 Micron Emission from High- and Low-Luminosity Active Galactic Nucleus Galaxies

April 2004 • 2004ApJ...604..565D

Authors • Dale, Daniel A. • Helou, George • Brauher, James R. • Cutri, Roc M. • Malhotra, Sangeeta • Beichman, Charles A.

Abstract • The Infrared Space Observatory (ISO) was used to search for a tracer of the warm and dense neutral interstellar medium, the [O I] 63.18 μm line, in four ultraluminous IRAS sources lying at redshifts between 0.6 and 1.4. While these sources are quasars, their infrared continuum emission suggests a substantial interstellar medium. No [O I] flux was detected after probing down to a 3 σ sensitivity level sufficient for detecting line emission in starbursts with similar continuum emission. However, if the detection threshold is slightly relaxed, one target is detected with 2.7 σ significance. For this radio-quiet quasar, there is likely a substantial dense and warm interstellar medium; the upper limits for the three radio-loud sources do not preclude the same conclusion. Using a new, uniformly processed database of the ISO extragalactic far-infrared spectroscopy observations, we show that nearby Seyfert galaxies typically have higher [O I]-to-far-infrared ratios than do normal star-forming galaxies, so the lack of strong [O I] 63 μm emission from these high-redshift ultraluminous sources cannot be attributed to their active cores.

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Roc Cutri

IPAC Deputy Director

George Helou

IPAC Executive Director