重申了银河系恒星翘曲和大犬座过密之间的联系
Reaffirming the connection between the Galactic stellar warp and the Canis Major overdensity
摘要：
我们进行了一个关键的重新分析和讨论最近的结果在文献中解释的CMa过密度的吸积矮星系或一个新的子结构内的银河系的签名。讨论了若干问题。我们表明，反对“扭曲”的解释是基于对银河系的错误认识。在平均翘曲中平面的相对两侧的颜色-星等图是不同的，没有什么异常。我们目睹了蓝羽人口的兴衰，首先归因于一个分裂的矮星系中的年轻恒星，现在作为一个正常的圆盘人口被丢弃。类似地，在薄+厚盘的金属丰度较低（-1<[Fe/H]<-0.5）的外部没有异常，并且螺旋臂（作为薄盘的一部分）应该并且确实弯曲。最重要的是，我们毫不含糊地表明，与以前的说法相反，翘曲产生的恒星过密度是距离兼容的CMa.The CMa过密度仍然完全占在一个一阶方法的银河系模型没有新的子结构。考虑到内在的不确定性（关于翘曲，耀斑和盘截止的性质，消光和简并的作用），这些模型的微小偏差不足以支持银河系盘中吸积矮星系或新子结构的假设。
英文摘要：
We perform a critical re-analysis and discussion of recent results presented in the literature which interpret the CMa overdensity as the signature of an accreting dwarf galaxy or a new substructure within the Galaxy. Several issues are addressed. We show that arguments against the ``warp'' interpretation are based on an erroneous perception of the Milky Way. There is nothing anomalous with colour--magnitude diagrams on opposite sides of the average warp mid-plane being different. We witnessed the rise and fall of the blue plume population, first attributed to young stars in a disrupting dwarf galaxy and now discarded as a normal disc population. Similarly, there is nothing anomalous in the outer thin+thick disc metallicities being low (-1<[Fe/H]<-0.5), and spiral arms (as part of the thin disc) should, and do, warp. Most importantly, we show unambiguously that, contrary to previous claims, the warp produces a stellar overdensity that is distance-compatible with that observed in CMa.The CMa over-density remains fully accounted for in a first order approach by Galactic models without new substructures. Given the intrinsic uncertainties (concerning the properties of the warp, flare and disc cutoff, the role of extinction and degeneracy), minor deviations with respect to these models are not enough to support the hypothesis of an accreted dwarf galaxy or new substructure within the Milky Way disc.
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