The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs
The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs
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DOI：
10.1093/mnras/staa652
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发表时间：
2019-12
影响因子：
4.8
通讯作者：
C. Lemon;C. Lemon;M. Auger;R. McMahon;T. Anguita;T. Anguita;Y. Apostolovski;G. C. Chen;C. Fas
中科院分区：
文献类型：
--
作者：
C. Lemon;C. Lemon;M. Auger;R. McMahon;T. Anguita;T. Anguita;Y. Apostolovski;G. C. Chen;C. Fas
我们报告了2017年末/2018年初暗能量调查(STRIDS)后续活动的强大透镜洞察的结果。我们在NTT和Keck的Echellette光谱仪和成像仪上用ESO暗星光谱仪和照相机2获得了65个透镜类星体的光谱，确认了10个新的透镜类星体和10个类星体对。八个透镜类星体被双重成像，源红移在0.99到2.9之间，一个是三重成像(DESJ0345DESJ0345DESJ2545，z=1.68)，一个是四重成像(四重成像：DESJ0053−2012，z=3.8)。基于南方天体物理研究望远镜上的SAMI或凯克上的近红外相机2的高分辨率成像，双星的奇异等温椭球模型给出了总放大倍数在3.2到5.6之间，爱因斯坦半径在0.49到1.97角秒之间。在光谱跟踪后，我们使用参数多波段模型从DES数据中提取了确认的透镜类星体和污染类星体+星对的多历元GrizY光度测量，并比较了每个系统组件的可变性。通过测量与将所有历元拟合到相同的星等相关联的减少的χ2，我们发现在保留所有已确认的透镜类星体的较少可变分量上存在简单的切割，同时去除94%的污染系统。根据我们的光谱跟踪，这种可变性信息将透镜类星体和类星体对的选择从34%-45%提高到51%-70%，剩余的大多数污染物是恒星形成星系。使用模拟的透镜类星体光曲线，我们证明了仅基于可变性的选择将在一个完整的DES幅值限制的样本中过度代表四元组分数10%，这可以用放大偏差来解释，从而在四元组中解释更低的光度/更多的可变来源。
We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager on Keck, confirming 10 new lensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ0345−2545, z = 1.68), and one is quadruply imaged (quad: DESJ0053−2012, z = 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near InfraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar + star pairs from DES data using parametric multiband modelling, and compare variability in each system’s components. By measuring the reduced χ2 associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51–70 per cent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.