A CURIOUS NEW MILKY WAY SATELLITE IN URSA MAJOR0
A CURIOUS NEW MILKY WAY SATELLITE IN URSA MAJOR0
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大熊座 0 中一颗奇怪的新银河系卫星
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
R. F. G. W
中科院分区：
文献类型：
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作者：
D. B. Z;V. B.;N. W. E;J. T. K;M. J. I;M. I. W;M. F;D. M. B;G. G;H. J. N;B. Y;J. A. S;P. C. H;E. F. B;H. R;O. Y. G;S. V.;R. F. G. W
在这封信中，我们研究了大熊座的局部恒星过密度，首先是在斯隆数字巡天(SDSS)数据中发现的，随后是斯巴鲁成像。它的颜色-震级图显示了一个明确的亚巨星分支、主序和转折，由此我们估计距离∼30kpc，投射大小为∼250×125pC。CMD表明了金属丰度和/或年龄有一定范围的复合种群。根据它的范围和恒星数量，我们认为这是一个以前未知的银河系卫星星系，他以其星座命名为熊大二号(Uma II)。利用SDSS数据，我们发现它的绝对星等数为mV∼−3.8，这将使其成为已知最暗的卫星星系。Uma II的等照线是不规则和扭曲的，有证据表明存在多个浓度；这表明卫星正处于分裂过程中。主题词：星系：矮星系：个体(大熊星团II)-局部星系群
In this Letter, we study a localized stellar overdensity in t he constellation of Ursa Major, first identified in Sloan Digital Sky Survey (SDSS) data and subsequently follo wed up with Subaru imaging. Its color-magnitude diagram (CMD) shows a well-defined sub-giant branch, main se quence and turn-o ff, from which we estimate a distance of∼ 30 kpc and a projected size of ∼ 250× 125 pc. The CMD suggests a composite population with some range in metallicity and /or age. Based on its extent and stellar population, we argue t hat this is a previously unknown satellite galaxy of the Milky Way, he reby named Ursa Major II (UMa II) after its constellation. Using SDSS data, we find an absolute magnitud e of MV ∼ −3.8, which would make it the faintest known satellite galaxy. UMa II’s isophotes are irr egular and distorted with evidence for multiple concentrations; this suggests that the satellite is in the p rocess of disruption. Subject headings: galaxies: dwarf — galaxies: individual (Ursa Major II) — Loc al Group