Spitzer spectroscopy of 3C radio galaxies and quasars

We are conducting a large survey of Fanaroff‐Riley class II radio galaxies and quasars at redshift z < 1 with the Spitzer Infrared Spectrograph. The goal is to determine which radio galaxies contain hidden active nuclei with luminosities comparable to quasars. We find that 40% of the radio galaxi...

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Bibliographic Details
Published in:Astronomische Nachrichten 2006-03, Vol.327 (2-3), p.241-244
Main Authors: Ogle, P. M., Whysong, D., Antonucci, R.
Format: Article
Language:English
Subjects:
quasars: general
radio continuum: galaxies
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Summary:We are conducting a large survey of Fanaroff‐Riley class II radio galaxies and quasars at redshift z < 1 with the Spitzer Infrared Spectrograph. The goal is to determine which radio galaxies contain hidden active nuclei with luminosities comparable to quasars. We find that 40% of the radio galaxies have mid‐IR power comparable to quasars of matched radio luminosity. These sources show thermal emission spectra from hot dust and silicate absorption from the dusty torus which blocks the optical nucleus from view. The mid‐IR bright radio galaxies also show emission lines, such as [SIV], [NeV], and [NeVI], from gas that is highly ionized by the hidden nucleus. However, 60% of the radio galaxies are relatively weak mid‐IR emitters, indicating that they do not contain a hidden, powerful accretion disk. Instead, their jets may be powered by a radiatively inefficient accretion flow or black hole spin. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ISSN:0004-6337
1521-3994
DOI:10.1002/asna.200510515