ATLAS lifts the Cup: discovery of a new Milky Way satellite in Crater
ATLAS lifts the Cup: discovery of a new Milky Way satellite in Crater
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DOI：
10.1093/mnras/stu626
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发表时间：
2014-03
影响因子：
4.8
通讯作者：
V. Belokurov;M. Irwin;Sergey E. Koposov;N. Evans;E. González-Solares;N. Metcalfe;T. Shanks
中科院分区：
文献类型：
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作者：
V. Belokurov;M. Irwin;Sergey E. Koposov;N. Evans;E. González-Solares;N. Metcalfe;T. Shanks
我们宣布在ESO VST ATLAS调查的数据中发现了一个新的银河系伴星，并随后在4米威廉赫歇尔望远镜上进行了深度成像。该卫星位于陨石坑星座（Cup），距离约170 kpc。其半光半径rh = 30pc，光度MV = - 5.5。它的大部分恒星人口年老且金属贫乏。我们很可能会把这颗新发现的卫星归类为一个扩展的球状星团，如果不是因为它有一些蓝色的环状恒星和一个稀疏的红色星团。核心氦燃烧人口的存在意味着，恒星形成可能发生在最近的400万年前。迄今为止，还没有球状星团完成了将恒星形成时间延长数光年的壮举。因此，如果我们关于陨石坑中蓝色明亮恒星是蓝环巨星的假设是正确的，那么这颗新卫星应该被归类为具有不同寻常属性的矮星系。请注意，在陨石坑以北仅10°处，两个超光速星系狮子座IV和狮子座V以大约相同的距离绕银河系运行。这暗示着这三颗卫星在一起落入银河系光晕之前可能曾经有过密切的联系。
We announce the discovery of a new Galactic companion found in data from the ESO VST ATLAS survey, and followed up with deep imaging on the 4-m William Herschel Telescope. The satellite is located in the constellation of Crater (the Cup) at a distance of ∼170 kpc. Its half-light radius is rh = 30 pc and its luminosity is MV = −5.5. The bulk of its stellar population is old and metal poor. We would probably have classified the newly discovered satellite as an extended globular cluster were it not for the presence of a handful of blue loop stars and a sparsely populated red clump. The existence of the core helium burning population implies that star formation occurred in Crater perhaps as recently as 400 Myr ago. No globular cluster has ever accomplished the feat of prolonging its star formation by several Gyr. Therefore, if our hypothesis that the blue bright stars in Crater are blue loop giants is correct, the new satellite should be classified as a dwarf galaxy with unusual properties. Note that only 10°to the north of Crater, two ultrafaint galaxies Leo IV and Leo V orbit the Galaxy at approximately the same distance. This hints that all three satellites may once have been closely associated before falling together into the Milky Way halo.