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Infrared Properties of High Redshift and X-ray Selected AGN Samples

Belinda J. Wilkes·Eric J. Hooper·Kim K. McLeod·Martin S. Elvis·David H. Hughes·Chris D. Impey·Joanna K. Kuraszkiewicz·Carol S. Lonsdale·Matt A. Malkan·Jonathan C. McDowell
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Abstract

The NASA/ISO Key Project on active galactic nuclei (AGN) seeks to better understand the broad-band spectral energy distributions (SEDs) of these sources from radio to X-rays, with particular emphasis on infrared properties. The ISO sample includes a wide variety of AGN types and spans a large redshift range. Two subsamples are considered herein: 8 high-redshift (1 < z < 4.7) quasars; and 22 hard X-ray selected sources. The X-ray selected AGN show a wide range of IR continuum shapes, extending to cooler colors than the optical/radio sample of Elvis et al. (1994). Where a far-IR turnover is clearly observed, the slopes are < 2.5 in all but one case so that non-thermal emission remains a possibility. The highest redshift quasars show extremely strong, hot IR continua requiring ~ 100 solar masses of 500 - 1000 Kelvin dust with ~ 100 times weaker optical emission. Possible explanations for these unusual properties include: reflection of the optical light from material above/below a torus; strong obscuration of the optical continuum; or an intrinsic deficit of optical emission.

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Belinda J. Wilkes, Eric J. Hooper, Kim K. McLeod, Martin S. Elvis, David H. Hughes, Chris D. Impey, Joanna K. Kuraszkiewicz, Carol S. Lonsdale, Matt A. Malkan, Jonathan C. McDowell. 2000-01-27. Infrared Properties of High Redshift and X-ray Selected AGN Samples. https://arxiv.org/abs/astro-ph/0001488

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