Abell 1703强透镜星系的Keck分光巡天：松弛单峰星系团的进一步证据
Keck spectroscopic survey of strongly lensed galaxies in Abell 1703: further evidence for a relaxed, unimodal cluster
摘要：
强引力透镜是精确模拟大质量星系团内部质量分布的独特工具。特别是，具有大爱因斯坦半径的星系团在星系团核心提供了丰富的多重成像系统，可以精确地确定中心暗物质轮廓的形状。本文介绍了对大质量星系团Abell 1703的光谱观测，发现它具有很大的爱因斯坦半径（z=2.8时为28”）和大量的强透镜系统，其中包括一个中心环状结构。我们使用凯克的LRIS瞄准多个图像和透镜星系候选者，并使用测量的红移来约束使用参数模型的集群的质量分布。这些数据使我们能够测量准确的红移与他们的光度红移很好的协议，并通过发现3个新的系统和径向计数器图像更新识别多成像系统。我们还报告了在我们的掩模中在z=5.827处发现了一个非常明亮的~3.6 L* i带丢失，它仅被集群适度放大（~3.0+/-0.08）。改进的参数质量模型包括16个多重系统和10个光谱红移，进一步约束了团簇尺度的质量分布，其广义NFW分布的最佳拟合对数斜率α =0.92+/-0.04，浓度c200=4.72+/-0.40，尺度半径rs=476+/-45 kpc.我们的强透镜模型预测了一个与斯巴鲁弱透镜测量结果一致的大尺度剪切信号，其强度可达4 Mpc h^-1。再加上强透镜模型需要一个单一的暗物质团，这表明阿贝尔1703是一个松弛的单峰星系团。这一独特的星系团可以进一步探测深X射线，SZ和动力学分析，在一个松弛的星系团的物理的详细研究。（节略）
英文摘要：
Strong gravitational lensing is a unique tool to model with great accuracy the inner mass distribution of massive galaxy clusters. In particular, clusters with large Einstein radii provide a wealth of multiply imaged systems in the cluster core allowing to determine precisely the shape of the central dark matter profile. This paper presents a spectroscopic survey in the massive cluster Abell 1703, displaying a large Einstein radius (28" at z=2.8) and a high number of strongly-lensed systems including a central ring-like configuration. We used LRIS on Keck to target multiple images and lensed galaxy candidates, and use the measured redshifts to constrain the mass distribution of the cluster using a parametric model. The data enable us to measure accurate redshifts in good agreement with their photometric redshifts, and to update the identification of multiply imaged systems by discovering 3 new systems and a radial counter image. We also report the discovery of a remarkably bright ~3.6 L* i-band dropout at z=5.827 in our mask which is only moderately magnified by the cluster (~3.0+/-0.08). The improved parametric mass model, including 16 multiple systems with 10 spectroscopic redshifts, further constrains the cluster-scale mass distribution with a generalized NFW profile of best-fit logarithmic slope alpha=0.92+/-0.04, concentration c200=4.72+/-0.40 and scale radius rs=476+/-45 kpc. Our strong-lensing model predicts a large scale shear signal consistent with Subaru weak-lensing measurements out to 4 Mpc h^-1. Together with the fact that the strong-lensing modeling requires a single dark matter clump, this suggests that Abell 1703 is a relaxed, unimodal cluster. This unique cluster could be probed further using deep X-ray, SZ and dynamics analysis, for a detailed study of the physics in a relaxed cluster. (abridged)
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