AAS 207th Meeting, 8-12 January 2006
Session 63 From Here to Eternity: The Spitzer Legacy Programs
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[63.02] Statistical and physical infrared properties of AGN as measured by SWIRE

E. Hatziminaoglou, I. Perez-Fournon (IAC Tenerife), M. Rowan-Robinson, T. Babbedge (Imperial College London), C.J. Lonsdale (IPAC Caltech), J. Fritz (University of Padova), A. Afonso-Luis, A. Hernan-Caballero (IAC Tenerife), SWIRE Team

SWIRE's wide-area multi-band coverage offers unprecedented opportunities for constructing large, unbiased AGN samples and for studying their cosmological evolution and physical properties. Here we present a collection of SWIRE results, namely on the infrared (IR) luminosity functions and on the tori characteristics of type-1 AGN. Type-1 AGN show clear signs of luminosity evolution out to z ~3 but also indicate some density evolution. This trend stops at higher redshifts suggesting that the epoch of peak formation and/or fueling has been reached. The 24 micron luminosity function shows stronger evolution than the IRAC bands. Results from a simple template fitting of the entire SWIRE sample indicate a high proportion of galaxies whose mid-IR SEDs are fitted by an AGN dust torus template (around one third). Of these only a small fraction are type-1 AGN according to the optical-near-IR template fitting, whereas the remaining are either type-2 AGN or Seyfert galaxies. The implied dust covering factor of more than 75% is much higher than that inferred for bright optically selected quasars. More detailed modeling of the torus surrounding the AGN can greatly benefit from SWIRE data. The IRAC and MIPS 24 micron data points impose strong constraints on the torus model parameters, such as the torus size, density law, and optical depth. Models with intermediate outer radii and density decreasing with increasing distance from the center are favored, while low optical depths are not ruled out.

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