Hubble Space TelescopeStudies of the WLM Galaxy. I. The Age and Metallicity of the Globular Cluster
Hubble Space TelescopeStudies of the WLM Galaxy. I. The Age and Metallicity of the Globular Cluster
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哈勃太空望远镜对 WLM 星系的研究。
DOI：
10.1086/307595
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
M. Mateo
中科院分区：
文献类型：
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作者：
P. Hodge;A. Dolphin;T. Smith;M. Mateo
我们已经获得了属于矮本星系群不规则星系WLM的孤立球状星团的V和I图像。该星团的色星等图显示它是一个正常的老球状星团，有一个清晰的巨分支达到MV =-2.5，一个水平分支在MV =+0.5，还有一个亚巨分支延伸到我们的测光极限MV =+2.0。与理论等时线的最佳拟合表明，该星团的金属丰度为[Fe/H] = -1.52 ± 0.08，年龄为14.8 ± 0.6 Gyr，这表明它与我们银河系中正常的古老晕球状星团相似。从拟合中我们还发现，该星系团的距离模为24.73 ± 0.07，消光系数为AV = 0.07 ± 0.06，这两个值与其他人获得的星系本身的数据在误差范围内一致。我们的结论是，这个正常的大质量星系团能够在WLM的形成过程中形成，尽管母星系的内部质量和尺寸非常小。
We have obtained V and I images of the lone globular cluster that belongs to the dwarf Local Group irregular galaxy known as WLM. The color-magnitude diagram of the cluster shows that it is a normal old globular cluster with a well-defined giant branch reaching to MV = -2.5, a horizontal branch at MV = +0.5, and a subgiant branch extending to our photometry limit of MV = +2.0. A best fit to theoretical isochrones indicates that this cluster has a metallicity of [Fe/H] = -1.52 ± 0.08 and an age of 14.8 ± 0.6 Gyr, thus indicating that it is similar to normal old halo globulars in our Galaxy. From the fit we also find that the distance modulus of the cluster is 24.73 ± 0.07 and the extinction is AV = 0.07 ± 0.06, both values that agree within the errors with data obtained for the galaxy itself by others. We conclude that this normal massive cluster was able to form during the formation of WLM, despite the parent galaxy's very small intrinsic mass and size.