标题： Fornax星团中的球状星团的HST成像：颜色和亮度分布 显示英文标题

标题： HST Imaging of the Globular Clusters in the Fornax Cluster: Color and Luminosity Distributions

摘要： 我们利用哈勃空间望远镜宽视场/行星相机2的成像数据，研究了室女星系团内三个早期星系（NGC 1399、NGC 1404 和另一个未具体指明）的球状星团的光度和B-I色指数分布。我们得到的光度函数在大多数情况下在B = 26.6等亮度下至少有50%的完备性。 我们发现，NGC 1399及其附近的邻居NGC 1404的核心区域球状星团的颜色分布是双峰的，并且在统计学上无法区分。根据这两个星系的颜色分布推断出的金属丰度范围与M 87非常相似。 NGC 1399的光度函数也与M 87非常相似，通过比较它们各自的峰值大小，表明室女星系团距离本星系群的距离几乎与后发座星系团到本星系群的距离相同。由此得出H_0 = 82 ± 8 km/s/Mpc，其中不确定性仅反映了随机误差的影响。 我们在距离NGC 1399投影距离440 kpc处发现的未解析天体数量与紧凑背景星系一致，尽管WFPC2的小视场不允许我们对星系际球状星团的数量施加严格的限制。 在NGC 1316周围探测到的天体的光度函数更接近指数分布而非对数正态分布，这些天体的颜色和大小分布与环绕NGC 1399的星团明显不同。 我们认为这些天体更类似于银河系中的古老疏散星团，而不是典型早期型星系中的球状星团。 显示英文摘要

摘要： We examine the luminosity and B-I color distribution of globular clusters for three early-type galaxies in the Fornax cluster using imaging data from the Wide Field/Planetary Camera 2 on the Hubble Space Telescope. The luminosity functions we derive are in most cases better than 50% complete down to B = 26.6. We find that the color distributions of globular clusters in the central region of NGC 1399 and its nearby neighbor NGC 1404 are bimodal and statistically indistinguishable. The metallicity spread, as inferred from the color distributions in these two galaxies, is very similar to that of M 87. NGC 1399's luminosity function is also very similar to that of M 87, and comparing their respective peak magnitudes indicates that the Fornax cluster is at very nearly the same distance from the Local Group as is the Virgo cluster. From this we derive H_0 = 82 +/- 8 km/s/Mpc, where the uncertainty reflects only the effects of random errors. The number of unresolved objects we find at a projected distance of 440 kpc from NGC 1399 is consistent with nothing more than compact background galaxies, though the small field of view of the WFPC2 does not allow us to put strong constraints on the number of intergalactic globular clusters. The luminosity function of objects detected around NGC 1316 is more nearly exponential than log-normal, and both the color and size distribution of these objects distinguishes them from the clusters surrounding NGC 1399. We suggest that these objects are more akin to old open clusters in the Galaxy than they are to globular clusters in typical early-type galaxies.