基于HST NICMOS测光的球状星团Terzan 5，Liller 1，UKS 1和Terzan 4的距离
Distances of the bulge globular clusters Terzan 5, Liller 1, UKS 1 and Terzan 4 based on HST NICMOS photometry
摘要：
在球状星团中发现了大量的双星和X射线源。为了理解这些集群的结构和内容，需要精确的距离。我们利用NGC 6528最近的距离测定作为参考，基于HST/NICMOS和NTT/SOFI红外测光，推导出Terzan 5，Liller 1和UKS 1的距离。贫金属团簇Terzan 4的距离是通过与M92在NICMOS波段的比较而得出的。富金属团簇的距离是通过比较团簇的水平分支（HB）能级，相对于通过NGC 6528的HB的红化线获得的。我们使用的方法的基础上NICMOS波段和转换到J和H的幅度与不同的假设。Liller~1和Terzan~4位于星系核的中央，UKS~1位于银河系中心之外，而Terzan ~ 5比其他4个星团更靠近太阳。泰山5号的距离是至关重要的，因为它有21颗恒星，这与高集群密度有关。泰山5的距离被发现是d $_{\odot}$ =5.5 $\pm$ 0.9 kpc到太阳，因此更接近我们比在泰山5的恒星研究中给出的值。因此，更高的星团密度更有利于最近在该星团中发现的毫秒双星的形成。
英文摘要：
A large number of pulsars and X-rays sources are detected in globular clusters. To understand the structure and content of these clusters, accurate distances are required. We derive the distances of Terzan 5, Liller 1 and UKS 1 using as a reference a recent distance determination of NGC 6528, based on HST/NICMOS and NTT/SOFI infrared photometry. The distance of the metal-poor cluster Terzan 4 was derived from a comparison with M92 in NICMOS bands. Distances of the metal-rich clusters are obtained by comparison of the Horizontal Branch (HB) level of the clusters, relative to the reddening line passing through the HB of NGC 6528. We use methods based on NICMOS bands and transformations to J and H magnitudes with different assumptions. Liller~1 and Terzan~4 are found to be at the central bulge distance, UKS~1 is beyond the Galactic center, while Terzan 5 is closer to the Sun than the other four clusters. The distance of Terzan 5 is of paramount importance, given the impact of its population of 21 pulsars, which is related to the high cluster density. The distance of Terzan 5 is found to be d$_{\odot}$=5.5$\pm$0.9 kpc from the Sun, thus closer to us than values given in studies of pulsars in Terzan 5. As a consequence, the higher cluster density is even more favourable for formation of the millisecond pulsars recently detected in this cluster.
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