Astron. J., 135, 1057-1066 (2008/March-0)
A survey of z ∼ 6 quasars in the sloan digital sky survey deep stripe. I. A flux-limited sample at zAB< 21.
JIANG L., FAN X., ANNIS J., BECKER R.H., WHITE R.L., CHIU K., LIN H., LUPTON R.H., RICHARDS G.T., STRAUSS M.A., JESTER S. and SCHNEIDER D.P.
Abstract (from CDS):
We present the discovery of five quasars at z ∼ 6 selected from 260deg2 of the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the celestial equator. The five quasars with 20<zAB<21 are 1-2 magnitudes fainter than the luminous z ∼ 6 quasars discovered in the SDSS main survey. One of them was independently discovered by the UKIRT Infrared Deep Sky Survey. These quasars, combined with another z ∼ 6 quasar known in this region, make a complete flux-limited quasar sample at zAB<21. The sample spans the redshift range 5.85 ≤ z ≤ 6.12 and the luminosity range -26.5≤M1450≤-25.4 (H0=70km.s–1.Mpc–1, Ωm=0.3, and ΩΛ=0.7). We use the 1/Va method to determine that the comoving quasar spatial density at <z≥6.0 and <M1450≥-25.8 is (5.0±2.1)x10–9.Mpc–3.mag–1. We model the bright-end quasar luminosity function (QLF) at z ∼ 6 as a power law Φ(L1450) ∝ Lβ1450. The slope β calculated from a combination of our sample and the luminous SDSS quasar sample is -3.1±0.4, significantly steeper than the slope of the QLF at z ∼ 4. Based on the derived QLF, we find that the quasar/active galactic nucleus (AGN) population cannot provide enough photons to ionize the intergalactic medium (IGM) at z ∼ 6 unless the IGM is very homogeneous and the luminosity (L*1450) at which the QLF power law breaks is very low.
galaxies: active - quasars: emission lines - quasars: general
Table 1: [JFA2008] JHHMMSS.ss+DDMMSS.s N=6.
Table 1: Except for the first object, the QSOs are not in the SDSS DR5 catalogue.
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