Merging Galaxies in Groups
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Merging Galaxies in Groups

August 26, 2008
Composite colour-image of the brightest galaxies in four groups located about 4 billion light-years away. The galaxies are ordered in increasing stellar mass, i.e. a rough time sequence. The brightest galaxies in group 1 and 2 both have obvious bright, gravitationally bound companions (see the crosses in this image). The inset in this image obtained with the Hubble Space Telescope shows that the brightest galaxy in group 3 has also a double nucleus. Thus, these galaxies are currently in the process of merging. This discovery provides unique and powerful validation of hierarchical formation as manifested in both galaxy and cluster assembly.

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