Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint
Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint
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DOI：
10.1093/mnras/stz781
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发表时间：
2019-01
影响因子：
4.8
通讯作者：
C. Spiniello;A. Sergeyev;L. Marchetti;Crescenzo Tortora;N. Napolitano;V. Shalyapin;A. Agnello;Fedor I. Getman;Mattia Vaccari;S. Serjeant;L. Koopmans;A. Baker;T. Jarrett;G. Covone;G. Vernardos
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文献类型：
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作者：
C. Spiniello;A. Sergeyev;L. Marchetti;Crescenzo Tortora;N. Napolitano;V. Shalyapin;A. Agnello;Fedor I. Getman;Mattia Vaccari;S. Serjeant;L. Koopmans;A. Baker;T. Jarrett;G. Covone;G. Vernardos
四倍透镜类星体是极其罕见的天体，但却是极其强大的宇宙学工具。在整个天空中只有几十个已知的。在这里，我们提出了两个新的四胞胎WG 0214 -2105和WG 2100 -4452的光谱确认，这两个四胞胎是由Agnello和Spiniello（2018）在暗能量调查公共足迹中发现的。我们已经用南部非洲大望远镜对这些系统进行了光谱跟踪，作为旨在确认赤道和南半球最大可能数量的强引力透镜的计划的一部分。对于这两个系统，我们提出的源光谱，使我们能够估计它们的红移和明确地确认其透镜性质。对于较亮的偏转器（WG 2100 -4452），我们从光谱中的光学吸收线测量光谱红移和恒星速度色散。对于另一个系统，由于光谱的质量不够好，我们从测光中推断出透镜的红移。我们获得测光两个镜头，直接从多波段图像，隔离类星体的镜头。Pan-STARRS也观测到了其中一个四胞胎，WG 0214 -2105，使我们能够估计每个类星体图像在两个不同时期的视亮度，从而找到通量变化的证据。这一结果可能表明，最微弱的组件的微透镜事件，虽然内在的变化不能被排除只有两个时代。最后，我们提出了简单的透镜模型的四胞胎，获得爱因斯坦半径，奇异的等温椭球速度色散，椭圆率，和位置角的透镜，以及时间延迟的预测假设一个和谐的宇宙模型。
Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of strong gravitational lenses in the equatorial and Southern hemisphere. For both systems, we present the sources spectra that allowed us to estimate their redshifts and unambiguously confirm their lensing nature. For the brighter deflector (WG2100-4452) we measure the spectroscopic redshift and the stellar velocity dispersion from optical absorption lines in the spectrum. For the other system we infer the lens redshift from photometry, being the quality of the spectra not good enough. We obtain photometry for both lenses, directly from multiband images, isolating the lenses from the quasars. One of the quadruplets, WG0214-2105, was also observed by Pan-STARRS, allowing us to estimate the apparent brightness of each quasar image at two different epochs, and thus to find evidence for flux variability. This result could suggest a microlensing event for the faintest components, although intrinsic variability cannot be excluded with only two epochs. Finally, we present simple lens models for both quadruplets, obtaining Einstein radii, singular isothermal ellipsoid velocity dispersions, ellipticities, and position angles of the lenses, as well as time-delay predictions assuming a concordance cosmological model.