Astronomers have found a rare encounter between two massive and gas-rich galaxies in a survey from Herschel. The event took place when the Universe was only about three billion years old and involved two galaxies forming stars with exceptional efficiency whilst in the process of merging. This galactic collision would go on to form a very massive elliptical galaxy with hardly any star formation activity. The discovery suggests a viable mechanism for the origin of the puzzling 'red and dead' galaxies that are seen in the young Universe.
A pair of merging galaxies in the young Universe discovered with Herschel (left panel) and imaged at higher resolution at near-infrared, sub-millimetre and radio wavelengths (right panel). Credit: ESA/NASA/JPL-Caltech/UC Irvine/STScI/Keck/NRAO/SAO
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"The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3", Hai Fu, et al., 2013, Nature. doi: 10.1038/nature12184.