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UPDATE ON THE NATURE OF VIRGO OVERDENSITY

机译:处女座超自然现象的最新动态

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We use the Eighth Data Release of Sloan Digital Sky Survey catalog with its additional sky coverage of the southern Galactic hemisphere to measure the extent and to study the nature of the Virgo Overdensity (VOD). The data show that the VOD extends over no less than 2000 deg2, with its true extent likely closer to 3000 deg2. We test whether the VOD can be attributed to a tilt in the stellar halo ellipsoid with respect to the plane of the Galactic disk and find that the observed symmetry of the north-south Galactic hemisphere star counts excludes this possibility. We argue that the Virgo Overdensity, in spite of its wide area and cloud-like appearance, is still best explained by a minor merger. Its appearance and position are qualitatively similar to a near perigalacticon merger event and, assuming that the VOD and the Virgo Stellar Stream (VSS) share the same progenitor, consistent with the VSS orbit determined by Casetti-Dinescu et al.
机译:我们使用斯隆数字天空测量目录的第八次数据发布,以及其对银河半球南半球的附加天空覆盖范围,来测量范围并研究处女座高密度(VOD)的性质。数据显示,VOD的范围不小于2000 deg2,其真实范围可能更接近3000 deg2。我们测试了VOD是否可归因于恒星晕椭圆体相对于银河系盘平面的倾斜,并发现观测到的南北银河半球恒星对称性排除了这种可能性。我们认为,处女座的密度过大,尽管其面积大且呈云状,但最好还是通过小规模合并来解释。它的外观和位置在质量上与近银河系合并事件相似,并且假设VOD和处女星流(VSS)共享同一祖细胞,这与Casetti-Dinescu等人确定的VSS轨道一致。

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