论文标题
目标选择和验证DESI类星体
Target Selection and Validation of DESI Quasars
论文作者
论文摘要
暗能量光谱仪器（DESI）的调查将使用类星体作为红移范围内的暗物质直接示踪剂0.9 <z <2.1的直接示踪剂测量大规模结构，并使用z> 2.1的类星体光谱中使用ly-alpha森林。我们提出了几种方法，可以从DESI传统成像调查中使用三个光节（G，R，Z）中的输入光度成像和两个来自广阔的红外红外探险家（WISE）中的两个红外带（W1，W2）中的输入光度成像（g，r，z）。在DESI的调查验证期间，对这些方法进行了广泛的测试。在本文中，我们报告了使用不同方法获得的结果，并介绍了我们针对DESI主调查进行了优化的选择。最终的类星体目标选择基于随机森林算法，并在16.5 <r <23的幅度范围内选择类星体。超深观测的视觉选择表明，主要选择包括71％的类星体，16％的星系，6％的恒星和7％的不确定光谱。使用基于此选择的光谱，我们构建了一个自动的类星体目录，该目录可在〜1000s的标称有效曝光时间内达到> 99％的纯度。每平方英度为310。目标密度，主要选择允许DESI每平方度选择超过200个QSO。 （包括60个具有Z> 2.1的类星体），超过项目要求的20％。所选类星体的红移分布与类星体光度函数预测非常吻合。
The Dark Energy Spectroscopic Instrument (DESI) survey will measure large-scale structures using quasars as direct tracers of dark matter in the redshift range 0.9<z<2.1 and using Ly-alpha forests in quasar spectra at z>2.1. We present several methods to select candidate quasars for DESI, using input photometric imaging in three optical bands (g, r, z) from the DESI Legacy Imaging Surveys and two infrared bands (W1, W2) from the Wide-field Infrared Explorer (WISE). These methods were extensively tested during the Survey Validation of DESI. In this paper, we report on the results obtained with the different methods and present the selection we optimized for the DESI main survey. The final quasar target selection is based on a Random Forest algorithm and selects quasars in the magnitude range 16.5<r<23. Visual selection of ultra-deep observations indicates that the main selection consists of 71% quasars, 16% galaxies, 6% stars and 7% inconclusive spectra. Using the spectra based on this selection, we build an automated quasar catalog that achieves a >99% purity for a nominal effective exposure time of ~1000s. With a 310 per sq. deg. target density, the main selection allows DESI to select more than 200 QSOs per sq. deg. (including 60 quasars with z>2.1), exceeding the project requirements by 20%. The redshift distribution of the selected quasars is in excellent agreement with quasar luminosity function predictions.
