A BRIGHT, SPATIALLY EXTENDED LENSED GALAXY AT z = 1.7 BEHIND THE CLUSTER RCS2 032727-132623
A BRIGHT, SPATIALLY EXTENDED LENSED GALAXY AT z = 1.7 BEHIND THE CLUSTER RCS2 032727-132623
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RCS2 星团后面 z = 1.7 处的明亮、空间延伸的透镜星系 032727-132623
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发表时间：
2010
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通讯作者：
R. Muñoz
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作者：
E. Wuyts;L. Barrientos;M. Gladders;K. Sharon;M. Bayliss;M. Carrasco;D. Gilbank;H. Yee;B. Koester;R. Muñoz
我们展示了第二次红色序列星团巡天（RCS2）中发现的极其明亮且扩展的透镜源。 RCSGA 032727-132609 经光谱证实为 z = 1.701 处背景星系的巨大弧线和反像，被 z = 0.564 处前景星系团 RCS2 032727-132623 强烈透镜化。巨大的弧线延伸超过~38英寸，积分r波段星等为19.1，使其比典型的透镜星系MS1512-cB58大~20倍，亮~3.5倍。这是迄今为止已知的宇宙中最亮的遥远透镜星系。我们收集了从 u 到 Ks 的 9 个波段的光度测量数据，这些波段对静止帧紫外光和可见光进行了密集采样，包括对年龄敏感的 4000 Å 断裂。为该系统构建了一个透镜模型，并为反像提供了 2.04 ± 0.16 的稳定总放大倍数；根据弧线和天空上反像的相对物理尺度，我们估计巨型弧线的平均放大倍数为 17.2 ± 1.4。单分量光谱能量分布模型与光度测量的拟合结果是中等年轻的年龄，t = 80 ± 40 Myr，少量的尘埃，E(B − V) ⩽ 0.11，以及指数下降的恒星形成历史，e 折叠时间 τ = 10 − 50 Myr。校正透镜放大率后，我们发现恒星质量为 M* ∼ 1010 M☉，当前恒星形成率 (SFR) ⩽77 M☉ yr−1。考虑到偶发性的恒星形成，潜在的旧爆发可能包含最多两倍于单成分模型推断的质量。就其年龄和恒星质量而言，RCSGA 032727-132609 是该红移附近已知的典型恒星形成星系群。其巨大的放大倍率和空间范围为详细研究单个高红移恒星形成星系的物理特性提供了独特的机会，为了解 z = 1.7 和我们当地宇宙之间的星系演化过程打开了一个新窗口。
We present the discovery of an extremely bright and extended lensed source from the second Red Sequence Cluster Survey (RCS2). RCSGA 032727-132609 is spectroscopically confirmed as a giant arc and counterimage of a background galaxy at z = 1.701, strongly lensed by the foreground galaxy cluster RCS2 032727-132623 at z = 0.564. The giant arc extends over ∼38″ and has an integrated r-band magnitude of 19.1, making it ∼20 times larger and ∼3.5 times brighter than the prototypical lensed galaxy MS1512-cB58. This is the brightest distant lensed galaxy in the universe known to date. We have collected photometry in nine bands, ranging from u to Ks, which densely sample the rest-frame UV and optical light, including the age-sensitive 4000 Å break. A lens model is constructed for the system and results in a robust total magnification of 2.04 ± 0.16 for the counterimage; we estimate an average magnification of 17.2 ± 1.4 for the giant arc based on the relative physical scales of the arc and counterimage on the sky. Fits of single-component spectral energy distribution models to the photometry result in a moderately young age, t = 80 ± 40 Myr, small amounts of dust, E(B − V) ⩽ 0.11, and an exponentially declining star formation history with e-folding time τ = 10 − 50 Myr. After correcting for the lensing magnification, we find a stellar mass of M* ∼ 1010 M☉ and a current star formation rate (SFR) ⩽77 M☉ yr−1. Allowing for episodic star formation, an underlying old burst could contain up to twice the mass inferred from single-component modeling. RCSGA 032727-132609 is typical of the known population of star-forming galaxies near this redshift in terms of its age and stellar mass. Its large magnification and spatial extent provide a unique opportunity to study the physical properties of an individual high-redshift star-forming galaxy in great detail, opening up a new window to the process of galaxy evolution between z = 1.7 and our local universe.