论文标题
通过深度学习和贝叶斯信息标准在$ z \ sim5 $处的类星体光度功能
The quasar luminosity function at $z\sim5$ via deep learning and Bayesian information criterion
论文作者
论文摘要
了解高红移处的类星体光度函数的微弱末端很重要，因为微弱的类星体的数量密度是限制紫外线（UV）光子预算的关键元素，用于电离早期宇宙中的乳半型介质（IgM）。在这里，我们提出了$ m_ {1450} \ sim -22.0 $ ab mag $ z \ sim5 $的$ m_ {1450} \ sim 5 $，比以前的UV LFS深约1级。我们从Hyper Soprime-CAM Subaru战略计划（HSC-SSP）获取的深度数据中选择了$ z \ sim5 $的类星体，并使用深度学习技术，涵盖了15.5度$^2 $区域。除了传统的颜色选择方法之外，我们还通过训练人工神经网络来改善了类星体的选择，该网络可以根据其颜色区分$ z \ sim5 $ quasars和非Quasar来源，并采用贝叶斯信息标准，该标准可以进一步删除高红色的星系和Quasar样品。当应用于一小部分光谱识别的类星体和星系时，我们的方法成功地以$ \ sim83 \％$效率（$ 5/6 $）选择了类星体，而与单独选择的选择相比，与选择使用颜色相比，高红速度星系（$ 1/8 $）的污染速率最小化了3次。我们的最终Quasar候选人数量为$ M_ {1450} <-22.0 $ mag是35。我们的Quasar UV lf降至$ M_ {1450} = -22 $ mag，甚至是fainter（$ M_ {1450} = -21 $ MAG），暗示着相当低的微弱的Quasars and Quasars and sloppe of。 $ -1.6^{+0.21} _ { - 0.19} $，有利于一种场景，即类Quasars在高红移时将IGM发挥作用。
Understanding the faint end of quasar luminosity function at a high redshift is important since the number density of faint quasars is a critical element in constraining ultraviolet (UV) photon budgets for ionizing the intergalactic medium (IGM) in the early universe. Here, we present quasar LF reaching $M_{1450} \sim -22.0$ AB mag at $z\sim5$, about one magnitude deeper than previous UV LFs. We select quasars at $z\sim5$ with a deep learning technique from deep data taken by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), covering a 15.5 deg$^2$ area. Beyond the traditional color selection method, we improved the quasar selection by training an artificial neural network for distinguishing $z\sim5$ quasars from non-quasar sources based on their colors and adopting the Bayesian information criterion that can further remove high-redshift galaxies from the quasar sample. When applied to a small sample of spectroscopically identified quasars and galaxies, our method is successful in selecting quasars at $\sim83 \%$ efficiency ($5/6$) while minimizing the contamination rate of high-redshift galaxies ($1/8$) by up to three times compared to the selection using color selection alone ($3/8$). The number of our final quasar candidates with $M_{1450} < -22.0$ mag is 35. Our quasar UV LF down to $M_{1450} = -22$ mag or even fainter ($M_{1450} = -21$ mag) suggests a rather low number density of faint quasars and the faint-end slope of $-1.6^{+0.21}_{-0.19}$, favoring a scenario where quasars play a minor role in ionizing the IGM at high redshift.
