Astronomers discovered a nest of monstrous baby galaxies 11.5 billion light-years away and they speculate that the galaxies seem to reside at the junction of gigantic filaments in a web of dark matter. 

Since dark matter is the umbrella term for matter that inference says must exist but which has never been detected, how can they know the galaxies are surrounded by it? Read on. Thugh things are relatively quiet now, ten billion years ago, long before the Sun and Earth were formed, areas of the Universe were inhabited by monstrous galaxies with star formation rates hundreds or thousands of times what we observe today in our Milky Way galaxy.

Alas, they are no more, but astronomers believe that these young galaxies matured into giant elliptical galaxies which are seen in the modern Universe.

Current galaxy formation hypotheses say these monstrous galaxies form in special environments where dark matter is concentrated but there is no science until that prediction can be tested. Part of the problem is that monstrous star-forming galaxies are often obscured in dust, making them difficult to observe in visible light, and while dusty galaxies do emit strong radio waves with submillimeter wavelengths, radio telescopes typically have not had the resolution needed to pin-point individual galaxies. 


Example of Monstrous Galaxies. On the left is the image taken at sub-millimeter wavelengths with ASTE. It looks like there is one bright monstrous galaxy. In the center is an image taken at the same sub-millimeter wavelengths, but this time using the new radio telescope facility ALMA. With 60 times better resolution and 10 times better sensitivity, we can see that actually there are 3 monstrous galaxies close together. On the right is the same region photographed in visible light by the Subaru Telescope. We can see that not all of the monstrous galaxies show up in this picture, or at the least that some of them must be very faint. Credit: ALMA (ESO/NAOJ/NRAO), NAOJ, H. Umehata (The University of Tokyo)

To search for monstrous galaxies, the research team used the Atacama Large Millimeter/submillimeter Array (ALMA). The young These findings are important for understanding how monstrous galaxies like these are formed and how they evolve in to huge elliptical galaxies.  to make extensive observations of a small part of the sky called SSA22 in the constellation Aquarius (the Water-Bearer).

Before their ALMA observations, the team searched for baby galaxies in SSA22 with ASTE, a 10-m submillimeter telescope operated by NAOJ. While the sensitivity and resolution was not sufficient to be sure, in the ASTE images they could see indications that there might be a cluster of monstrous galaxies. With ten times better sensitivity and 60 times better resolution, ALMA enabled astronomers to pinpoint the locations of nine monstrous galaxies in SSA22.

The team compared the positions of these galaxies with the location of a cluster of young galaxies 11.5 billion light-years from Earth in SSA22 which had been studied in visible light by the Subaru Telescope, operated by the National Astronomical Observatory of Japan (NAOJ). 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 team found that their young monstrous galaxies seemed to be were 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. 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. 

source: National Institutes of Natural Sciences