Reconstructing the history of star formation in rich cluster cores
Reconstructing the history of star formation in rich cluster cores
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重建丰富星团核心恒星形成的历史
DOI：
10.1046/j.1365-8711.2001.03981.x
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发表时间：
2000
影响因子：
4.8
通讯作者：
R. Bower
中科院分区：
文献类型：
--
作者：
T. Kodama;R. Bower
我们的研究首先利用来自7个CNOC星团的数据重新审视了布彻-欧姆勒光度效应。我们为这些星团构建了前景/背景校正的色星等图。我们的分析表明，CNOC星团再现了Butcher & Oemler观测到的蓝星系比例随着红移而增加的趋势。我们使用这些数据来研究星团中恒星形成的历史，通过将这些星团作为不同红移的快照连接起来。我们解决两个关键问题。首先，我们要问蓝色星系的简单衰落和被动演化是否与附近星系团（如后发星系团）中星系的性质一致。我们发现，恒星形成场星系向更红的颜色演化（一旦恒星形成在进入星团环境时停止）可以成功地重建本星团中星系的颜色和星等。没有必要对这些星系进行广泛的破坏。由于蓝色星系随着年龄的增长而褪色，因此在当今的色星等关系中，较暗的星系往往比明亮的星系有更长的恒星形成历史。然而，这种影响不足以引起星系沿颜色-星等关系的相当大的年龄变化，这意味着斜率主要是由金属丰度的变化决定的。
Our study begins by revisiting the photometric Butcher–Oemler effect using data from seven CNOC clusters at We construct the foreground/background-corrected colour–magnitude diagrams for these clusters. Our analysis shows that the CNOC clusters reproduce the trend of increasing blue galaxy fraction with redshift as seen by Butcher & Oemler. We use these data to investigate the history of star formation in clusters by connecting these clusters as snapshots at different redshifts. We address two key issues. First, we ask whether the simple fading and passive evolution of the blue galaxies is consistent with the properties of galaxies in nearby clusters, such as the Coma cluster. We find that the evolution of star-forming field galaxies towards redder colour (once the star formation ceases on entry into the cluster environment) can successfully reconstruct colours and magnitudes of galaxies in the local cluster. There is no requirement for widespread disruption of these galaxies. Since the blue galaxies fade as they age, the fainter galaxies on the present-day colour–magnitude relation tend to have more extended star formation histories than their bright counterparts. However, this effect is not sufficient to cause a sizeable age variation for the galaxies along the colour–magnitude relation, implying that the slope is dominated by variations in metal abundance.
Secondly, we address the nature of the Butcher–Oemler effect itself. We compare the distribution of galaxies in the colour–magnitude diagrams and hence infer the evolution of the rate at which galaxies have arrived in the cluster. Models in which star formation is abruptly truncated as galaxies are accreted by the cluster have difficulty in reproducing the observed colour distribution. In contrast, if star formation declines on a 1-Gyr time-scale after accretion, the galaxy accretion history we infer is consistent from cluster to cluster and matches well the distribution expected in simple theoretical models. The Butcher–Oemler effect is thus driven both by the declining star formation rates of field galaxies and by a decline in the rate at which fresh galaxies are accreted by the cluster.
Our study naturally leads to a comparison of the global star formation histories of galaxies in clusters and the field. We show that the star formation rate per galaxy mass for galaxies in cluster cores is significantly smaller than that of the field environment below due to the truncation of star formation. However, the factor by which star formation is suppressed is dependent on the cluster accretion history. High-quality observations of clusters at higher redshifts are needed to define this relation better.