Color-Magnitude Sequence in the Clusters at z ~ 1.2 near the Radio Galaxy 3C 324
Color-Magnitude Sequence in the Clusters at z ~ 1.2 near the Radio Galaxy 3C 324
复制标题
射电星系 3C 324 附近 z ~ 1.2 处星团中的颜色幅度序列
DOI：
10.1093/pasj/52.1.61
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发表时间：
2000
影响因子：
2.3
通讯作者：
K. Sekiguchi
中科院分区：
文献类型：
--
作者：
M. Kajisawa;Toru Yamada;I. Tanaka;T. Maihara;F. Iwamuro;H. Terada;M. Goto;K. Motohara;H. Tanabe;T. Taguchi;R. Hata;M. Iye;M. Imanishi;Y. Chikada;Michitoshi Yoshida;C. Simpson;T. Sasaki;G. Kosugi;T. Usuda;K. Sekiguchi
我们利用斯巴鲁望远镜获得的图像和记录的HST数据，研究了射电星系3C324附近Z~1.2位置K‘选定星系的光学和近红外颜色。星系团区域中星系的颜色分布相当广泛，这可能意味着它们在恒星形成历史上发生了重大的散射，尽管场星系污染的影响尚不确定。R-K颜色与旧星系被动演化模型一致的红色星系序列在K‘~20 MAG处被截断，星系团区域内几乎没有较暗的红色星系。我们发现，通过定量形态分类所选择的以膨胀为主的星系在颜色-星等图上形成了一个广泛的序列，其斜率比被动演化的同世纪星系群体中金属丰度变化所预期的要陡峭得多。我们认为，观测到的色星等序列可以用金属丰度和年龄变化来解释，K‘>；20Mag较暗的星系可能比较亮的星系年轻1-2 Gyr。颜色和K‘波段光度在天空分布上存在一定的空间分离；较红和较亮的天体往往位于3C324附近。
We have investigated the optical and near-infrared colors of K'-selected galaxies in clusters at z ~ 1.2 near to the radio galaxy 3C 324 using images obtained with the Subaru telescope and archival HST data. The distribution of colors of the galaxies in the cluster region is found to be fairly broad, and it may imply significant scatter in their star-formation histories, although the effect of contamination of field galaxies is uncertain. The red sequence of galaxies whose R-K colors are consistent with passive evolution models for old galaxies is found to be truncated at K' ~ 20 mag, and there are few fainter galaxies with similar red colors in the cluster region. We find that the bulge-dominated galaxies selected by quantitative morphological classification form a broad sequence in the color-magnitude diagram, whose slope is much steeper than that expected from metallicity variations within a passively evolving coeval galaxy population. We argue that the observed color-magnitude sequence can be explained by metallicity and age variations, and the fainter galaxies with K' > 20 mag may be 1-2 Gyr younger than the brighter galaxies. Some spatial segregation of the color and K'-band luminosity is seen in the sky distribution; the redder and the brighter objects tend to be located near 3C 324.