Saturday, December 5, 2015

Monstrous Baby Galaxies Found in Web of Dark Matter

A visualization of the proto-Great Wall and monstrous galaxies. Monstrous galaxies are thought to preferentially be born at the centers of the web like structures formed by young galaxies. Credit: ALMA (ESO/NAOJ/NRAO)

Japanese astronomers have discovered a nest of monstrous baby galaxies in a web of dark matter located 11.5 billion light-years away from Earth.

Researchers made the discovery by first searching for baby galaxies with ASTE, a 10-m submillimeter telescope operated by the National Astronomical Observatory of Japan, in a region named SSA22 located within the constellation Aquarius.

Although ASTE's sensitivity and resolution was not sufficient to be sure, astronomers could see in the images indications that there might be a cluster of monstrous galaxies. After this discovery, researchers turned to the Atacama Large Millimeter/submillimeter Array (ALMA) that has ten times better sensitivity and 60 times better resolution than ASTE to confirm the presence of the galaxies.

Astronomers then compared the positions of those galaxies with the location of a cluster of young galaxies in SSA22 that had been studied in visible light by the Subaru Telescope. Researchers found that the shape of the cluster observed by the Subaru Telescope indicates the presence of a huge 3D web of invisible dark matter. This dark matter filamentary structure is thought to be a progenitor of large scale structures in the Universe. One of the best known examples of large scale structure in the modern Universe is the cosmic Great Wall, a gigantic filamentary structure spanning over 500 million light-years. The filamentary structure in SSA22 could be called a proto-Great Wall.

The scientists found that their young monstrous galaxies seemed to be located right at the intersection of the dark matter filaments. This finding supports the model that monstrous galaxies form in areas where dark matter is concentrated, researchers concluded. And since modern large elliptical galaxies are simply monstrous galaxies which have mellowed with age, they too must have originated at nexuses in the large scale structure.

On the left is the image taken at sub-millimeter wavelengths with ASTE which appears as one bright monstrous galaxy. In the center is an image taken at the same sub-millimeter wavelengths using ALMA radio telescope which shows that there are actually three monstrous galaxies close together. On the right is the same region photographed in visible light by the Subaru Telescope. Credit: ALMA (ESO/NAOJ/NRAO), NAOJ, H. Umehata (The University of Tokyo).