AAS 195th Meeting, January 2000
Session 98. Quasars and Their Cousins
Oral, Friday, January 14, 2000, 2:00-3:30pm, Centennial III

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[98.03] Infrared Excesses in Luminous High-z Quasars from the U.S. ISO Key Project on AGN

E.J. Hooper, B.J. Wilkes (Harvard-Smithsonian CfA), K.K. McLeod (Wellesley), M.S. Elvis (CfA), C.D. Impey (Steward Obs.), C.J. Lonsdale (IPAC), M.A. Malkan (UCLA), J.C. McDowell (CfA)

The NASA/ISO Key Project on AGN seeks to better understand the spectral energy distributions, particularly in the infrared, of a wide variety of AGN spanning a large range in redshift. The cornerstone of the project is a set observations of 72 AGN with the Infrared Space Observatory (ISO). Photometry with the ISOPHOT instrument spanning 3 - 200 \micron is supplemented by ground-based near-IR, optical, and sub-mm photometry, as well as literature data from radio to X-rays. Our sources include radio-loud and quiet quasars, strong X-ray and UV emitters, PG quasars, BALQSOs and red quasars, among other subclasses.

While the majority of sources in the sample are at relatively low redshifts, 9 have z > 0.9, with the most distant, 1202-0727, at z = 4.7. This radio-quiet quasar is an unusual object (Wilkes et al. 1999, in ``The Universe as Seen by ISO,'' ESA SP-427, 845), with an IR luminosity ~1016 L\sun, high even if gravitationally lensed (Omont et al. 1996, Nat, 382, 428). Much of the luminosity is emitted in the rest-frame near and mid-IR, which if thermal, represents a large mass of hot (1000K) dust.

New sub-mm observations with the JCMT, coupled with ISO data, indicate that the two next-highest redshift AGN in the sample (z = 3.9 and z = 4.3) have similar features. The sub-mm fluxes are up to a factor 5 lower than expected based on scaling a median AGN SED (Elvis et al. 1994, ApJS, 95, 1) to near/mid-IR fluxes. While this is not as extreme as for 1202-0727, it is suggestive of similar rest-frame near-IR excesses. Additionally, the sub-mm slopes are flatter than expected (\alpha \lesssim 1 for f\nu \propto \nu\alpha). If thermal emission dominates in all of these sources, the temperature range of the dust is broad, similar to inferred range of 50-1000K in 1202-0727. See also Wilkes et al. (this meeting) for another Key Project subsample. NASA grant NAG5-3363 is acknowledged.

The author(s) of this abstract have provided an email address for comments about the abstract: ehooper@cfa.harvard.edu

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