加拿大-法国高z类星体巡天：九个新类星体和红移6的光度函数
The Canada-France High-z Quasar Survey: nine new quasars and the luminosity function at redshift 6
摘要：
本文介绍了加拿大-法国高z类星体巡天（CFHQS）中发现的9个新的z ~ 6类星体的成像和光谱，使CFHQS类星体的总数达到19个。通过将CFHQS与更明亮的SDSS样本相结合，我们能够从40个红移为5.74 < z < 6.42的类星体样本中导出类星体光度函数。我们的分箱光度函数显示出比以前的工作中发现的略低的归一化和平坦的斜率。合并的数据也表明在M_1450的光度函数中有一个大约-25的中断。数据的双幂律极大似然拟合与分组结果一致。光度函数在-27.5 < M_1450 <-24.7的范围内受到强约束（1 sigma不确定性< 0.1 dex）。最佳拟合参数为Phi（M_1450^*）= 1.14 x 10^-8 Mpc^-3 mag^-1，突变星等M_1450^* = -25.13，亮端斜率β =-2.81。然而，β和M_1450^* 之间的协方差阻止了对任一参数施加强约束。对于在-26 < M_1450^* < -24范围内的突变幅度，我们在95%置信度下发现-3.8 < beta < -2.3。我们计算的z = 6类星体星系际电离通量，并显示它是20和100倍之间的低，比所需的再电离。最后，我们使用光度函数来预测在未来的近红外成像调查中可能会发现多少高红移类星体。
英文摘要：
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.
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