关于所谓的星系晕的二元性
On the alleged duality of the Galactic halo
摘要：
我们基于SDSS/SEGUE数据研究了星系晕的运动学。我们发现，他们声称的反向旋转的光环是距离估计的实质性偏差（约50%）的结果：声称的逆行分量，它只占整个样本的一小部分，容易受到污染，被确定为距离高估的尾部。强烈的高估也导致垂直速度分量的提升，这解释了这些物体声称达到的高度。对于金属丰度最低的恒星，误差最大，这解释了人造成分的金属贫乏性质。我们还认为，测量误差没有得到适当的考虑，并使用高斯拟合本质上非高斯银河系的组件调用的组件是扭曲的，甚至是人为的识别。我们的数据评估导致修订的估计速度椭球，并没有产生任何可靠的证据，反向旋转的晕组件。如果一个明显的反向旋转晕分量存在，它必须远远弱于声称的Beillo等人。最后，我们注意到，他们的修订分析在Beers等人。（2011）并没有减轻我们的主要关注。
英文摘要：
We examine the kinematics of the Galactic halo based on SDSS/SEGUE data by Carollo et al. (2007, 2010). We find that their claims of a counter-rotating halo are the result of substantial biases in distance estimates (of order 50%): the claimed retrograde component, which makes up only a tiny fraction of the entire sample, prone to contaminations, is identified as the tail of distance overestimates. The strong overestimates also result in a lift in the vertical velocity component, which explains the large altitudes those objects were claimed to reach. Errors are worst for the lowest metallicity stars, which explains the metal-poor nature of the artificial component. We also argue that measurement errors were not properly accounted for and that the use of Gaussian fitting on intrinsically non-Gaussian Galactic components invokes the identification of components that are distorted or even artificial. Our evaluation of the data leads to a revision of the estimated velocity ellipsoids and does not yield any reliable evidence for a counterrotating halo component. If a distinct counterrotating halo component exists it must be far weaker than claimed by Carollo et al. Finally we note that their revised analysis presented in Beers et al. (2011) does not alleviate our main concerns.
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