Mid-infrared selection of quasar-2s in Spitzer's First Look Survey

M. Lacy (1) , G. Canalizo (2) , S. Rawlings (3) , A. Sajina (4) , L. Storrie-Lombardi (1) , L. Armus (1) , F. Marleau (1) , A. Muzzin (1). ((1) Spitzer Science Center

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Caltech; (2) University of California Riverside; (3) Oxford University; (4) University of British Columbia)

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keywords obscuredfirstluminositycandidateevidencelookmid-infraredselection

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We present early results from the spectroscopic follow-up of a sample of candidate obscured AGN selected in the mid-infrared from the Spitzer First Look Survey. Our selection allows a direct comparison of the numbers of obscured and unobscured AGN at a given luminosity for the first time, and shows that the ratio of obscured to unobscured AGN at infrared luminosities corresponding to low luminosity quasars is ~1:1 at z~0.5. Most of our optically-faint candidate obscured AGN have the high-ionization, narrow-line spectra expected from type-2 AGN. A composite spectrum shows evidence for Balmer absorption lines, indicating recent star-formation activity in the host galaxies. There is tentative evidence for a decrease in the obscured AGN fraction with increasing AGN luminosity.

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Mid-infrared selection of quasar-2s in Spitzer's First Look Survey

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