Stellar populations in Local Group dwarf elliptical galaxies. I: NGC 147
Stellar populations in Local Group dwarf elliptical galaxies. I: NGC 147
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本群矮椭圆星系中的恒星群。
DOI：
10.1086/161141
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
G. Costa
中科院分区：
文献类型：
--
作者：
J. Mould;J. Kristian;G. Costa
给出了NGC147到I星等23的彩色星等图。这个椭圆形星系外部的恒星数量与银河系球状星团的数量相似。对巨型星团和球状星系团的定量比较得出的平均金属丰度为-1.2+或-0.2，这使得NGC147成为椭圆星团中质量和金属丰度之间一般关联的一部分。巨大的分支看起来很宽，这表明金属丰度分散。在高于红巨星分支顶端的光度下没有渐近巨星分支恒星，这为NGC147场中年龄小于12 Gyr的恒星的比例设定了10%的上限。这一结果与一些相关但质量较小的矮球系统的情况形成了鲜明对比。如果选择假设，而不是确定NGC147的恒星含量，则得出的距离为630+或-50kpc，类似于M31的距离。
A color-magnitude diagram of NGC 147 to an I magnitude of 23 is presented. The stellar population in the outer parts of this elliptical galaxy resembles that of the globular clusters of the Milky Way. Quantitative comparison of the giant branch with those of globular clusters yields a mean metallicity of -1.2 + or - 0.2, making NGC 147 a part of the general correlation between mass and metallicity seen in ellipticals. The giant branch appears to be broad, which suggests a metallicity dispersion. The absence of asymptotic giant branch stars at luminosities above that of the red giant branch tip sets an upper limit of 10 percent for the fraction of stars in this NGC 147 field that have ages less than 12 Gyr. This result contrasts with the situation in some of the related, but less massive, dwarf spheroidal systems. If the choice is made to assume, rather than determine the stellar content of NGC 147, a distance of 630 + or - 50 kpc is derived, similar to that of M31.