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Session 31 - Quasars.
Oral session, Wednesday, January 07
International Ballroom East,

[31.06] A Mid-IR QSO Survey with the WIRE Satellite

C. J. Lonsdale, C. Xu, D. Shupe, F. Fang, T. Barlow (IPAC, Caltech and JPL), P. Hacking (Vanguard Research), B. T. Soifer (Caltech)

The Wide Field Infrared Explorer (WIRE) will survey hundreds of square degrees of high latitude sky at 12 and 25 microns, with the primary goals of investigating the evolutionary history of starburst galaxies and to search for dusty protogalaxies. WIRE will also be extremely successful in detecting reddened/dust-obscured QSOs, since not only are optical depths much lower in the mid-infrared than at traditional UV QSO selection wavelengths, but also because the SEDs of local dusty QSOs peak strongly in the mid-IR, the emission usually being attributed to the dusty molecular torus hypothesized in AGN unification scenarios. We will present predictions of number counts of red QSOs from WIRE, using evolutionary models based on the known local space density of IRAS-detected AGNs and QSOs, which take account of the latest mid-IR SEDs available from ISO data. Making no additional assumptions about (currently controversial) hypothetical populations of heavily obscured (type 2?) QSO populations, we predict up to about 100 mid-IR-luminous AGNs per square degree at the limit of WIRE 12 micron detectability, for a luminosity evolution rate going as (1+z)^3.2, and over 6000 in the total WIRE survey. Depending on the level of the confusion noise, WIRE will detect the most luminous objects to redshifts of 2 to 3. Confirming the QSO population in the WIRE data and with follow-up spectroscopy will be difficult because their 12\mum-25\mum-optical colors may be similar to typical L starburst galaxies, although bluer than most ultraluminous IR galaxies. Heavy dust obscuration may hide the point-like nucleus and the broad line region. However, if these predictions are borne out by the WIRE survey, they will provide empirical proof for AGN models in which a large fraction of the AGN population has been missed by UV and radio selection techniques, due to heavy dust obscuration of the active nucleus.

Program listing for Wednesday