Segue 2：萨省萨省人口的原型
Segue 2: A Prototype of the Population of Satellites of Satellites
摘要：
我们宣布在斯隆银河系理解和探索扩展（SEGUE）的数据中发现了一颗新的银河系卫星Segue 2。我们在多镜望远镜上进行了更深入的成像和光谱学研究。由此求得该星系的光度为M_v =-2.5，半光半径为34 pc，系统速度为-40 $km/s。我们的MMT数据还提供了证据，在一个类似的日心速度的Segue 2周围的流，和SEGUE数据显示，它也存在于邻近领域。我们将Segue 2的速度色散解析为3.4 km/s，可能的流约为7 km/s。这个物体显示了与其他最近发现的Segue 1，Boo II和Coma的比较点。我们推测，这四个物体可能代表了一群卫星的卫星--它们是吸积事件的幸存者，这些事件摧毁了它们更大但密度较低的父母。它们很可能是在红移z > 10时形成的，是再电离时代化石的良好候选者。
英文摘要：
We announce the discovery of a new Milky Way satellite Segue 2 found in the data of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope. From this, we derive a luminosity of M_v = -2.5, a half-light radius of 34 pc and a systemic velocity of -40$ km/s. Our MMT data also provides evidence for a stream around Segue 2 at a similar heliocentric velocity, and the SEGUE data show that it is also present in neighboring fields. We resolve the velocity dispersion of Segue 2 as 3.4 km/s and the possible stream as about 7 km/s. This object shows points of comparison with other recent discoveries, Segue 1, Boo II and Coma. We speculate that all four objects may be representatives of a population of satellites of satellites -- survivors of accretion events that destroyed their larger but less dense parents. They are likely to have formed at redshifts z > 10 and are good candidates for fossils of the reionization epoch.
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