Discovery of an unusually compact lensed Lyman-break galaxy from the Hyper Suprime-Cam Survey
Discovery of an unusually compact lensed Lyman-break galaxy from the Hyper Suprime-Cam Survey
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DOI：
10.1093/mnras/staa583
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发表时间：
2019-08
影响因子：
4.8
通讯作者：
A. Jaelani;A. More;A. Sonnenfeld;M. Oguri;C. Rusu;Kenneth C. Wong;J. Chan;S. Suyu;I. Kayo
中科院分区：
文献类型：
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作者：
A. Jaelani;A. More;A. Sonnenfeld;M. Oguri;C. Rusu;Kenneth C. Wong;J. Chan;S. Suyu;I. Kayo
我们报告的偶然发现HSC J 0904 -0102，一个四重透镜莱曼break星系（LBG）的引力透镜天体在超超级凸轮成像调查（SuGOHI）。由于它的点状外观，这个来源被认为是一个透镜状的活动星系核。我们获得了后续的光谱数据与双子座南望远镜，这证实了这是一个透镜系统的双子座多目标光谱仪。偏转的前景星系是一个典型的早型星系，红移为z_{\ell}=0.957$，恒星速度色散为sigma_v=259\pm56$ km s−1。根据Lyα向蓝方向的急剧下降和其它吸收特征，确定透镜源为z_{\rms}=3.403$的LBG。一个简单的透镜质量模型，假设一个奇异的等温椭球体，得出爱因斯坦半径为$\theta_{\rm Ein}=1.23$ arcsec，爱因斯坦半径内的总质量为$M_{\rm Ein}=（5.55\pm0.24）\times10^{11}\rm M_{\odot}$对应于速度色散$\sigma_{\rm SIE}=283\pm3$ km s−1，这与光谱导出的值非常一致。最孤立的LBG透镜图像的放大倍率为$\sim 6.5$。与其他透镜LBG和典型LBG群体相比，HSC J 0904 -0102异常紧凑，在$> 2sigma $置信度下为离群值。再加上之前发现的SuGOHI透镜，HSC J1152+0047，这是类似的紧凑，我们相信，HSC的调查是扩大LBG研究到更小的星系大小。
We report the serendipitous discovery of HSC J0904–0102, a quadruply lensed Lyman-break galaxy (LBG) in the Survey of Gravitationally-lensed Objects in Hyper Suprime-Cam Imaging (SuGOHI). Owing to its point-like appearance, the source was thought to be a lensed active galactic nucleus. We obtained follow-up spectroscopic data with the Gemini Multi-Object Spectrographs on the Gemini South Telescope, which confirmed this to be a lens system. The deflecting foreground galaxy is a typical early-type galaxy at a high redshift of $z_{\ell}=0.957$ with stellar velocity dispersion $\sigma_v=259\pm56$ km s−1. The lensed source is identified as an LBG at $z_{\rm s}=3.403$, based on the sharp drop bluewards of Lyα and other absorption features. A simple lens mass model for the system, assuming a singular isothermal ellipsoid, yields an Einstein radius of $\theta_{\rm Ein}=1.23$ arcsec and a total mass within the Einstein radius of $M_{\rm Ein}=(5.55\pm0.24)\times10^{11}\rm M_{\odot}$ corresponding to a velocity dispersion of $\sigma_{\rm SIE}=283\pm3$ km s−1, which is in good agreement with the value derived spectroscopically. The most isolated lensed LBG image has a magnification of $\sim 6.5$. In comparison with other lensed LBGs and typical $z\sim4$ LBG populations, HSC J0904–0102 is unusually compact, an outlier at $>2\sigma$ confidence. Together with a previously discovered SuGOHI lens, HSC J1152+0047, which is similarly compact, we believe that the HSC survey is extending LBG studies down to smaller galaxy sizes.