A survey of z>5.7 quasars in the Sloan Digital Sky Survey.: II.: Discovery of three additional quasars at z>6

We present the discovery of three new quasars at z > 6 in similar to 1300 deg(2) 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 Lyalpha emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to similar to0.05 and could be affected by the presence of broad absorption line systems. The last object has a Lyalpha strength more typical of lower redshift quasars. Based on a sample of six quasars at z > 5.7 that cover 2870 deg(2) presented in this paper and in Paper I, we estimate the comoving density of luminous quasars at z similar to 6 and M(1450) < -26.8 to be ( 8 +/- 3) x 10(-10) Mpc(-3) (for H(0) = 50 km s(-1) Mpc(-1), Omega = 1). Hubble Space Telescope imaging of two z > 5.7 quasars and high-resolution, ground-based images ( seeing similar to0."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 similar to 6 is shallower than Psi proportional to L(-3.5) (2 sigma), consistent with the absence of strongly lensed objects.