引力透镜系统CASSOWARY 5的X射线摄影观测
X-shooter Observations of the Gravitational Lens System CASSOWARY 5
摘要：
我们确认了CASSOWARY星表中的第八个引力透镜系统。VLT上的X-射手摄谱仪的探索性观测显示，CSWA 5系统至少包含三个图像，一个蓝色恒星形成星系的z = 1.0686，被一个明显的红色星系群所透镜，其中一个星系的z = 0.3877。透镜星系呈现出丰富的光谱，具有广泛的星际吸收线和丰富的星云发射线。对这些特征的初步分析表明，该星系是年轻的，年龄为2500万至5000万年。恒星形成速率约为20个太阳质量/年，银河系已经聚集了3 x 10^9个太阳质量的恒星，并达到半个太阳的金属丰度。它的蓝色光谱能量分布和巴耳末线比表明内部尘埃消光可以忽略不计。目前，由于缺乏可行的透镜模型，对该系统的特性进行更深入的分析受到阻碍。然而，已经很清楚，CSWA 5与红移z = 1-3的紫外选择星系的一般人口共享许多物理特性，激发了对引力透镜的来源和前景质量浓度的进一步研究。
英文摘要：
We confirm an eighth gravitational lens system in the CASSOWARY catalogue. Exploratory observations with the X-shooter spectrograph on the VLT show the system CSWA5 to consist of at least three images of a blue star-forming galaxy at z = 1.0686, lensed by an apparent foreground group of red galaxies one of which is at z = 0.3877. The lensed galaxy exhibits a rich spectrum with broad interstellar absorption lines and a wealth of nebular emission lines. Preliminary analysis of these features shows the galaxy to be young, with an age of 25-50 Myr. With a star-formation rate of approximately 20 solar masses/yr, the galaxy has already assembled a stellar mass of 3 x 10^9 solar masses and reached half-solar metallicity. Its blue spectral energy distribution and Balmer line ratios suggest negligible internal dust extinction. A more in-depth analysis of the properties of this system is currently hampered by the lack of a viable lensing model. However, it is already clear that CSWA5 shares many of its physical characteristics with the general population of UV-selected galaxies at redshifts z = 1-3, motivating further study of both the source and the foreground mass concentration responsible for the gravitational lensing.
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