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B.J. Wilkes, E.J. Hooper (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 ISOPHOT instrument in 8 bands spanning 3 - 200 microns supplemented by ground-based near-IR, optical, and sub-mm photometry, and fluxes from radio to X-rays culled from the literature. Our sample includes a variety of properties, luminosities, and redshifts, to take full advantage of ISO's major improvements in infrared astronomy: much better spatial resolution and wider wavelength coverage than earlier missions.
A key question to be addressed with this dataset is the relative importance of thermal (reprocessed by dust with a range of temperatures) and non-thermal emission in the infrared. SED shapes, particularly far-IR slopes, provide a crucial discriminant between these fundamentally different emission mechanisms. IR-bright sources typically show strong signatures of thermal emission in the far-IR while radio-loud AGN favor non-thermal processes. A strong relation between X-ray and near-IR fluxes in X-ray selected AGN and near-IR correlated variability in optically selected quasars argue for significant non-thermal emission in these sources.
Hard X-ray selection avoids the biases towards unabsorbed and IR-bright AGNs present in optical and IR-selected samples. Of our sample, 21 are bright, hard X-ray emitters. We compare the IR SEDs with other AGN samples and explore the previously reported near-IR vs X-ray relation to investigate the relative importance of dust emission in both far- and near-IR. We study the range of IR--X-ray SEDs and look for absorbed sources which are bright in IR and X-ray regions but faint in optical-UV.
Another Key Project subsample is discussed by Hooper et al.~(this meeting). This project is funded by NASA grant: NAG5-3363.