The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey
The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey
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DOI：
10.1093/pasj/psx091
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发表时间：
2017-04
影响因子：
2.3
通讯作者：
M. Akiyama;W. He;H. Ikeda;M. Niida;T. Nagao;J. Bosch;J. Coupon;M. Enoki;M. Imanishi;N. Kashikawa;T. Kawaguchi;Y. Komiyama;Chien-Hsiu Lee;Y. Matsuoka;S. Miyazaki;A. Nishizawa;M. Oguri;Y. Ono;M. Onoue;M. Ouchi;A. Schulze;J. Silverman;Manobu M. Tanaka;Masayuki Tanaka;Y. Terashima;Y. Toba;Y. Ueda
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文献类型：
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作者：
M. Akiyama;W. He;H. Ikeda;M. Niida;T. Nagao;J. Bosch;J. Coupon;M. Enoki;M. Imanishi;N. Kashikawa;T. Kawaguchi;Y. Komiyama;Chien-Hsiu Lee;Y. Matsuoka;S. Miyazaki;A. Nishizawa;M. Oguri;Y. Ono;M. Onoue;M. Ouchi;A. Schulze;J. Silverman;Manobu M. Tanaka;Masayuki Tanaka;Y. Terashima;Y. Toba;Y. Ueda
我们给出了基于超超素数-凸轮-斯巴鲁战略计划宽层成像数据的z=4类星体在339.8°2的g、r、i、z和y波段的光度函数。从恒星物体中，通过g-Drobled选择选择到i=24.0mag，选择了1666z~4类星体。它们的光度学红移覆盖了3.6到4.3之间的红移范围，平均为3.9。结合斯隆数字巡天的类星体样本，在相同的红移范围内，构造了覆盖M1450=-22~-29mag的宽光度范围的类星体光度函数。在M1450=-25.36+-0.13mag处的拐点为双幂规律模型，其指数为-1.30+-0.05的平坦弱端斜率可以很好地描述。类星体的膝部和暗端斜率没有明显的红移演化证据。平坦的斜率意味着类星体群体的UV光度密度是由膝部周围的类星体主导的，并不支持z>；5报告的较高红移时较陡峭的微弱端斜率。如果我们利用类星体的UV和X射线光度及其散射之间的关系将M1450光度函数转换为硬X射线2-10keV光度函数，则UV选择类星体的数密度与光度函数膝盖以上X射线选择AGN的数密度匹配得很好。在膝盖以下，紫外线选择的类星体显示出与硬X射线光度功能相比的不足。这一缺陷可以用紫外线选择类星体中缺少被遮挡的活动星系核来解释。
We present the luminosity function of z=4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg^2. From stellar objects, 1666 z~4 quasar candidates are selected by the g-dropout selection down to i=24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3 with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, the quasar luminosity function covering the wide luminosity range of M1450=-22 to -29 mag is constructed. It is well described by a double power-law model with a knee at M1450=-25.36+-0.13 mag and a flat faint-end slope with a power-law index of -1.30+-0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those at z~2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z>5. If we convert the M1450 luminosity function to the hard X-ray 2-10keV luminosity function using the relation between UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected AGNs above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.