Abell 1689, shown in this composite image, is a massive cluster of galaxies located about 2.3 billion light years away that shows signs of merging activity. Hundred-million-degree gas detected by NASA's Chandra X-ray Observatory is shown as purple in this image, while galaxies from optical data from the Hubble Space Telescope are colored yellow. The X-ray emission has a smooth appearance, unlike other merging systems such as the Bullet Cluster or MACS J0025.4-1222. The temperature pattern across Abell 1689 is more complicated, however, possibly requiring multiple structures with different temperatures.
The long arcs in the optical image are caused by gravitational lensing of background galaxies by matter in the galaxy cluster, the largest system of such arcs ever found. Further studies of this cluster are needed to explain the lack of agreement ，between mass estimates based on the X-ray data and on the gravitational lensing. Previous work suggests that filament-like structures of galaxies are located near Abell 1689 along our line-of-sight to this cluster, which may bias mass estimates using gravitational lensing.
Abell 1689，在这张合成图里是一个位于23亿光年以外的巨大星系群并不断的互相合并着。几百万度的气体被NASA的钱德拉X射线探测器所捕捉到，在图中以紫色标记，哈勃拍摄的可见光波段图像是以黄色标记。X射线释放物，其外观看起来十分光滑，并不象其他合并系统，例如子弹星云或 MACS J0025.4-1222，Abell 1689的气温模型是非常复杂的，也许这是因为其具有多重带有不同温度的结构。
在可见光图像中巨长的弧线是由于背景巨大质量星系群的引力透镜所导致的，如此巨大系统中的弧线还从没见过。以后对于这个星系群的研究需要被用来解释关于基于用X射线数据和引力透镜估算质量的不协调问题。先前的工作组说那些星系的丝状结构位于靠近Abell 1689的一端，这结果可能会偏向[于使用引力透镜来估算质量。
信息来自钱德拉，自翻
[ 本帖最后由 江涛 于 2008-9-13 13:09 编辑 ] |
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