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arXiv 1609.06304astro-ph.GA
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Milky Way的贝叶斯质量估计:包括分层贝叶斯的测量不确定性

Bayesian Mass Estimates of the Milky Way: including measurement uncertainties with hierarchical Bayes

Gwendolyn Eadie, Aaron Springford, William Harris

摘要:

我们提出了一个层次贝叶斯方法估计银河系的总质量和质量分布。新的分层贝叶斯方法进一步改进了Eadie,Harris,& Widrow(2015)和Eadie & Harris(2016)提出的框架,并建立在Eadie et al(2015a,c)的初步报告基础上。该方法使用分布函数$f(\mathcal{E},L)$来模拟星系和运动学数据从卫星物体,如球状星团(GC)跟踪银河系的引力势。该方法的一个主要优点是,它不仅包括完整和不完整的数据同时在分析中,而且还纳入了测量不确定性在一个连贯的和有意义的方式。我们首先使用Eadie & Harris(2016)中假设的相同数据和幂律模型测试了分层贝叶斯框架,其中包括测量不确定性,并发现结果相似但更强的约束。接下来,我们利用新的统计框架并结合所有可能的GC数据,找到具有贝叶斯可信区域的累积质量分布。该图谱表明$4.8\times10^{11}M_{\odot}$的质量在$125$ kpc内,具有$(4.0-5.8)\times10^{11}M_{\odot}$的95\%贝叶斯可信区域。我们的研究结果还提供了所有GC的真实比能的估计。通过将这些估计的能量与具有完整速度测量的GC的测量能量进行比较,我们观察到具有完整测量的(少数)远程示踪剂可能在确定银河系的总质量估计中发挥很大作用。因此,我们的研究强调需要更多的远程示踪剂与完整的速度测量。

英文摘要:

We present a hierarchical Bayesian method for estimating the total mass and mass profile of the Milky Way Galaxy. The new hierarchical Bayesian approach further improves the framework presented by Eadie, Harris, & Widrow (2015) and Eadie & Harris (2016) and builds upon the preliminary reports by Eadie et al (2015a,c). The method uses a distribution function $f(\mathcal{E},L)$ to model the galaxy and kinematic data from satellite objects such as globular clusters (GCs) to trace the Galaxy's gravitational potential. A major advantage of the method is that it not only includes complete and incomplete data simultaneously in the analysis, but also incorporates measurement uncertainties in a coherent and meaningful way. We first test the hierarchical Bayesian framework, which includes measurement uncertainties, using the same data and power-law model assumed in Eadie & Harris (2016), and find the results are similar but more strongly constrained. Next, we take advantage of the new statistical framework and incorporate all possible GC data, finding a cumulative mass profile with Bayesian credible regions. This profile implies a mass within $125$kpc of $4.8\times10^{11}M_{\odot}$ with a 95\% Bayesian credible region of $(4.0-5.8)\times10^{11}M_{\odot}$. Our results also provide estimates of the true specific energies of all the GCs. By comparing these estimated energies to the measured energies of GCs with complete velocity measurements, we observe that (the few) remote tracers with complete measurements may play a large role in determining a total mass estimate of the Galaxy. Thus, our study stresses the need for more remote tracers with complete velocity measurements.

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