SIMBAD references

We present the discovery of three new quasars at z>6 in ∼ 1300 deg² of Sloan Digital Sky Survey imaging data, J114816.64+525150.3 (z=6.43), J104845.05+463718.3 (z=6.23), and J163033.90+401209.6 (z=6.05). The first two objects have weak Lyα emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to ∼0.05 and could be affected by the presence of broad absorption line systems. The last object has a Lyα strength more typical of lower redshift quasars. Based on a sample of six quasars at z>5.7 that cover 2870 deg² presented in this paper and in Paper I, we estimate the comoving density of luminous quasars at z∼6 and M₁₄₅₀←26.8 to be (8±3)x10^–10 Mpc^–3 (for H₀=50 km/s/Mpc, Ω=1). Hubble Space Telescope imaging of two z>5.7 quasars and high-resolution, ground-based images (seeing ∼0".4) of three additional z>5.7 quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshift quasar sample suggests the bright-end slope of the quasar luminosity function at z∼6 is shallower than Ψ∝L^–3.5 (2 σ), consistent with the absence of strongly lensed objects.