Mass segregation in globular clusters
Mass segregation in globular clusters
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球状星团中的质量偏析
DOI：
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发表时间：
1981
期刊：
影响因子：
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通讯作者：
M. Bappu
中科院分区：
文献类型：
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作者：
K. K. Scaria;M. Bappu
在u， B， V， R和i波段的光电孔径光度测定已经确定，在距离中心2至4角分之间的星团比在其他地方更蓝。中心和蓝区之间的b - I色差是≃0.45 mag。发现核心半径取决于所选择的观测波段，最小的核心半径为其波段。ω Cen在b、V和红外波段的等距测量结果表明，该星团在红外波段接近球形，具有波长依赖性。在距星团中心约3 arcmin处，椭圆度最大。该区域的蓝色贡献来自未解析恒星的漫射背景和水平分支（HB）恒星相对丰度的增加。漫射背景与HB星之间的相似性已被证明。利用照相减法技术研究了星团中HB星的分布。本研究得到的47tuc星团的等等距测量结果与先前的光电光度测量结果进行了比较。在这里，椭圆度的增加也与星团的蓝色增加有关。迄今为止所研究的所有球状星团的椭圆度都显示出椭圆度与离中心距离的依赖关系的相似性。椭圆度在中心附近和外围区域值较小，在中间区域值最大。我们认为球状星团中的红色恒星具有接近球形的分布。蓝色恒星在核心周围形成一个凸起，分布更椭圆，方向也不同。指出了球状星团和m31核心的旋转在椭圆性方面的相似性；因此，m31的核可能在旋转曲线显示峰值的区域周围显示出更蓝的颜色和更小的紫外线过剩。
Photoelectric aperture-photometry ofω Cen inU, B, V, R andI bands has established that the cluster is bluer between 2 arcmin and 4 arcmin from the centre, than it is elsewhere. The difference inB - I colour between the centre and this blue zone is ≃ 0.45 mag. The core radius is found to be dependant on the wavelength band chosen for observation, the smallest core radius being for theI band. Equidensitometry ofω Cen inB, V and infrared bands shows a wavelength dependence with the cluster being nearly spherical in the infrared band. It shows a maximum ellipticity around 3 arcmin from the cluster centre. The blue contribution in this zone comes from both a diffuse background of unresolved stars and an increase in the relative abundance of horizontal branch (HB) stars. The similarity between the diffuse background and the HB stars has been demonstrated. A photographic subtraction technique is used to study the distribution of HB stars in the cluster.Results of equidensitometry of the cluster 47 Tuc, obtained in the present study, are compared with the earlier results of photoelectric photometry. Here too an increase in ellipticity is associated with an increase in the blueness of the cluster. All globular clusters studied so far for ellipticity show a similarity in the dependence of the ellipticity on the distance from the centre. The ellipticity has small values near the centre and in the outer regions, with the maximum value in between. We suggest that the red stars in globular clusters have a nearly spherical distribution. The blue stars form a bulge around the core with a more elliptical distribution and a different orientation. A similarity between the ellipticity aspects of both the globular clusters and rotation in the nucleus of M 31 is pointed out; the M 31 nucleus may thus show a bluer colour and smaller UV excess around the region where the rotation curve shows a peak.