We present discovery imaging and spectroscopy for nine new z ~ 6 quasars
found in the Canada-France High-z Quasar Survey (CFHQS) bringing the total
number of CFHQS quasars to 19. By combining the CFHQS with the more luminous
SDSS sample we are able to derive the quasar luminosity function from a sample
of 40 quasars at redshifts 5.74 < z < 6.42. Our binned luminosity function
shows a slightly lower normalisation and flatter slope than found in previous
work. The binned data also suggest a break in the luminosity function at M_1450
approx -25. A double power law maximum likelihood fit to the data is consistent
with the binned results. The luminosity function is strongly constrained (1
sigma uncertainty < 0.1 dex) over the range -27.5 < M_1450 < -24.7. The
best-fit parameters are Phi(M_1450^*) = 1.14 x 10^-8 Mpc^-3 mag^-1, break
magnitude M_1450^* = -25.13 and bright end slope beta = -2.81. However the
covariance between beta and M_1450^* prevents strong constraints being placed
on either parameter. For a break magnitude in the range -26 < M_1450^* < -24 we
find -3.8 < beta < -2.3 at 95% confidence. We calculate the z = 6 quasar
intergalactic ionizing flux and show it is between 20 and 100 times lower than
that necessary for reionization. Finally, we use the luminosity function to
predict how many higher redshift quasars may be discovered in future near-IR
imaging surveys.

在该研究中，我们发现了九个新的红移为～6 的类星体，进一步提出了一个由 40 个类星体组成的亮度函数，结果显示该类星体的亮度函数比以前认为的更为平坦，同时预测了在未来的近红外成像调查中可能会发现多少更高红移的类星体。