用球状星团推断宇宙年龄
Inferring the Age of the Universe with Globular Clusters
摘要：
利用全色星等图中恒星的分布，估算了68个银河系球状星团的绝对年龄。特别是，我们共同估计的绝对年龄，距离，红化，金属丰度（[Fe/H]）和[ $α$ /Fe]的每个集群，实施独立的观测动机先验，我们还估计可能的恒星建模的系统。我们推导出的球状星团样本的距离与GAIA使用主序星（如果可用）获得的距离一致，推断的年龄与以前发表的年龄一致。我们方法的新颖之处在于，利用所采用的先验知识，我们能够从球状星团色星等图中稳健地估计这些参数。在68%的置信水平下，我们发现最老的球状星团的平均年龄为$t_{\rm GC}=13.32 \pm 0.1 {\rm (stat.)} \pm 0.5 {\rm (sys.)}$，包括恒星模型的系统不确定性。这些测量可以用来推断宇宙的年龄，在很大程度上独立于宇宙学参数：我们发现宇宙的年龄$t_{\rm U}=13.5^{+0.16}_{-0.14} {\rm (stat.)} \pm 0.5 ({\rm sys.})$在68\%的置信水平，占球状星团的形成时间和它的不确定性。这个值与$13.8 \pm 0.02$ Gyr相容，后者是普朗克任务假设$Λ$ CDM模型推断出的宇宙学模型相关值。
英文摘要：
We present an estimate of the absolute age of 68 galactic globular clusters obtained by exploiting the distribution of stars in the full color-magnitude diagram. In particular, we jointly estimate the absolute age, distance, reddening, metallicity ([Fe/H]) and [$α$/Fe] of each cluster, imposing priors motivated by independent observations; we also estimate possible systematics from stellar modeling. Our derived distances for the globular cluster sample are in agreement with those obtained from GAIA using main-sequence dwarf stars (where available), and the inferred ages are in good agreement with those previously published. The novelty of our approach is that, with the adopted priors, we are able to estimate robustly these parameters from the globular cluster color-magnitude diagram. We find that the average age of the oldest globular clusters is $t_{\rm GC}=13.32 \pm 0.1 {\rm (stat.)} \pm 0.5 {\rm (sys.)}$, at 68\% confidence level, including systematic uncertainties from stellar modeling. These measurements can be used to infer the age of the Universe, largely independently of the cosmological parameters: we find an age of the Universe $t_{\rm U}=13.5^{+0.16}_{-0.14} {\rm (stat.)} \pm 0.5 ({\rm sys.})$ at 68\% confidence level, accounting for the formation time of globular clusters and its uncertainty. This value is compatible with $13.8 \pm 0.02$ Gyr, the cosmological model-dependent value inferred by the Planck mission assuming the $Λ$CDM model.
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