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arXiv 0710.3740astro-ph
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Local Group和Milky Way的质量

Masses for the Local Group and the Milky Way

Yang-Shyang Li, Simon D. M. White

备注：
11 pages, 6 figures, MNRAS accepted. Added a new discussion paragraph and a new figure regarding the relative transverse velocity but conclusions unchanged
发表信息：
Mon.Not.Roy.Astron.Soc.384:1459-1468,2008
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摘要：

我们使用非常大的千年模拟的和谐$Λ$ CDM宇宙起源校准的偏差和误差分布的定时参数估计的质量的本地组和银河系。从大量类似于银河系/仙女座星系的孤立螺旋-螺旋对中，我们发现计时质量与真实质量之比的四分位数范围是1.8倍，而这个比例分布的5%和95%点是由5.7倍分开的。在这里，我们将真质量定义为两个主要星系的“维里”质量$M_{200}$之和。对于仙女座的距离和接近速度的当前最佳值，这导致$5.27\times 10^{12}\msun$或$\log M_{LG}/M_\odot = 12.72$的本地组的真实质量的中值似然估计，具有$[12.58, 12.83]$的四分位数范围和$[12.26, 13.01]$的5%至95%的范围。因此，局部组真实质量的95%置信下限为$1.81\times 10^{12}\msun$。根据观测到的遥远卫星狮子座I的大衰退速度对银河系质量的时间估计也同样有效，尽管有更大的系统不确定性。它给出了银河系的位力质量估计值为$2.43 \times 10^{12}\msun$，置信下限为$0.80 \times 10^{12}\msun$的95%。

英文摘要：

We use the very large Millennium Simulation of the concordance $Λ$CDM cosmogony to calibrate the bias and error distribution of Timing Argument estimators of the masses of the Local Group and of the Milky Way. From a large number of isolated spiral-spiral pairs similar to the Milky Way/Andromeda system, we find the interquartile range of the ratio of timing mass to true mass to be a factor of 1.8, while the 5% and 95% points of the distribution of this ratio are separated by a factor of 5.7. Here we define true mass as the sum of the ``virial'' masses $M_{200}$ of the two dominant galaxies. For current best values of the distance and approach velocity of Andromeda this leads to a median likelihood estimate of the true mass of the Local Group of $5.27\times 10^{12}\msun$, or $\log M_{LG}/M_\odot = 12.72$, with an interquartile range of $[12.58, 12.83]$ and a 5% to 95% range of $[12.26, 13.01]$. Thus a 95% lower confidence limit on the true mass of the Local Group is $1.81\times 10^{12}\msun$. A timing estimate of the Milky Way's mass based on the large recession velocity observed for the distant satellite Leo I works equally well, although with larger systematic uncertainties. It gives an estimated virial mass for the Milky Way of $2.43 \times 10^{12}\msun$ with a 95% lower confidence limit of $0.80 \times 10^{12}\msun$.

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