论文标题
来自黑暗能源调查数据版本2的南部光度测量结果目录2
A Southern Photometric Quasar Catalog from the Dark Energy Survey Data Release 2
论文作者
论文摘要
我们在$ \ sim 5000 \，{\ rm deg^2} $ Dark Energy Survey（DES）广泛的调查区域中，提出了南半球140万个光学固定的类星体候选目录。我们将来自DES第二个数据释放（DR2）的光学光度与可用的近红外（NIR）和选择中的全天空中红外光度法结合在一起。我们在相对通量的多维空间中构建具有多元偏度分布的类星体，星系和恒星模型，作为红移（或恒星的颜色）和幅度的功能。我们的选择算法为类星体，星系和星星分配了概率，同时计算了类星体和星系候选物的光度红移（照片-U Z $）。在光谱确认的对象上进行基准测试，我们成功对94.7％的类星体，99.3％的星系和96.3％的星星进行了分类，当所有IR频段（NIR $ yjhk $和Wise $ WISE $ W1W2 $）都可以使用。当较少的频段可用时，分类和照片回归成功率会降低。我们的Quasar（Galaxy）photo- $ z $质量，定义为对象的一部分，它们之间的差异为$ z $ $ z_p $和光谱红移$ z_s $，$ |Δz| = | z_s -z_p |/（1 + z_s）\ le 0.1 $，当所有IR频段可用时，为92.2％（98.1％），仅使用光学DED数据降至72.2％（90.0％）。我们的光度测量目录的估计完整性为89％，纯度为$ r <21.5 $（68万$ r <218亿美元），其完整性和纯度降低为$ 21.5 <r \ r \ lyssim 24 $。在140万种候选人中，有87,857名现有光谱，其中84,978（96.7％）是光谱证实的类星体。最后，我们为DES DR2共同光度目录中的所有（6.9亿）光度源提供了类星体，星系和星形概率。
We present a catalog of 1.4 million photometrically-selected quasar candidates in the southern hemisphere over the $\sim 5000\,{\rm deg^2}$ Dark Energy Survey (DES) wide survey area. We combine optical photometry from the DES second data release (DR2) with available near-infrared (NIR) and the all-sky unWISE mid-infrared photometry in the selection. We build models of quasars, galaxies, and stars with multivariate Skew-t distributions in the multi-dimensional space of relative fluxes as functions of redshift (or color for stars) and magnitude. Our selection algorithm assigns probabilities for quasars, galaxies, and stars, and simultaneously calculates photometric redshifts (photo-$z$) for quasar and galaxy candidates. Benchmarking on spectroscopically confirmed objects, we successfully classify (with photometry) 94.7% of quasars, 99.3% of galaxies, and 96.3% of stars when all IR bands (NIR $YJHK$ and WISE $W1W2$) are available. The classification and photo-$z$ regression success rates decrease when fewer bands are available. Our quasar (galaxy) photo-$z$ quality, defined as the fraction of objects with the difference between the photo-$z$ $z_p$ and the spectroscopic redshift $z_s$, $|Δz| = |z_s - z_p|/(1 + z_s)\le 0.1$, is 92.2% (98.1%) when all IR bands are available, decreasing to 72.2% (90.0%) using optical DES data only. Our photometric quasar catalog achieves estimated completeness of 89% and purity of 79% at $r<21.5$ (0.68 million quasar candidates), with reduced completeness and purity at $21.5<r\lesssim 24$. Among the 1.4 million quasar candidates, 87,857 have existing spectra and 84,978 (96.7%) of them are spectroscopically confirmed quasars. Finally, we provide quasar, galaxy, and star probabilities for all (0.69 billion) photometric sources in the DES DR2 coadded photometric catalog.
