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Date and Time of the Query: 2018-12-15 T01:46:42 PST
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For refcode 2004AJ....127..646F:
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Copyright by American Astronomical Society. Reproduced by permission
2004AJ....127..646F An Unbiased Census of Active Galactic Nuclei in the Two Micron All Sky Survey Paul J. Francis, Brant O. Nelson, and Roc M. Cutri Abstract. We present an unbiased near-IR - selected AGN sample, covering 12.56 deg^2^ down to K_s_~15.5, selected from the Two Micron All Sky Survey (2MASS). Our only selection effect is a moderate color cut (JK_s_>1.2) designed to reduce contamination from Galactic stars. We observed both pointlike and extended sources. Using the brute-force capabilities of the Two Degree Field multifiber spectrograph on the Anglo-Australian Telescope, we obtained spectra of 65% of the target list: an unbiased subsample of 1526 sources. Eighty percent of the 2MASS sources in our fields are galaxies, with a median redshift of 0.15. The remainder are K and M dwarf stars. We find tentative evidence that Seyfert 2 nuclei are more common in our IR-selected survey than in blue-selected galaxy surveys. We estimate that 5.1+/-0.7% of the galaxies have Seyfert 2 nuclei with H{alpha} equivalent widths greater than 0.4 nm, measured over a spectroscopic aperture of radius ~2.5 kpc. Blue-selected galaxy samples only find Seyfert 2 nuclei meeting these criteria in ~1.5% of galaxies. We find that 1.2+/-0.3% of our sources are broadline (type 1) AGNs, giving a surface density of 1.0+/-0.3 deg^2^, down to K_s_<15.0. This is the same surface density of type 1 AGNs as optical samples down to B<18.5. Our type 1 AGNs, however, mostly lie at low redshifts, and host galaxy light contamination would make ~50% of them hard to find in optical QSO samples. We conclude that the type 1 AGN population found in the near-IR is not dramatically different from that found in optical samples. There is no evidence for a large population of AGNs that could not be found at optical wavelengths, although we can only place very weak constraints on any population of dusty high-redshift QSOs. In contrast, the incidence of type 2 (narrow-line) AGNs in a near-IR - selected galaxy sample seems to be higher than in a blue-selected galaxy sample. Keywords: Galaxies: Active, Galaxies: Quasars: General, Surveys
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