Several New Galaxies Discovered Bathed In Dark Matter

Scientists have used the Atacama Large Millimeter/submillimeter Array (ALMA) at the European Southern Observatory, to find number of extremely large, albeit young galaxies, at distance of about 11 billion light years away from Earth. What’s particularly interesting about the discovery is that all of the young galaxies are bathed in dark matter. The ALMA offers 60 times better resolution and 10 times better sensitivity as astronomers peer deep into the universe. As such, the scientists have been able to detect three distinct galaxies bound together in a group, residing at the junction of gigantic filaments in a web of dark matter. Astronomers believe the discovery of these new dark matter-bathed galaxies will assist them in understanding the formation of certain galaxies and how they evolve to form huge elliptical clusters of stars and planets.

As large as galaxies are, finding them in the undefinable depths of the universe can be difficult. Up to now, larger galaxies have been discovered aplenty. These smaller, dark matter-bathed galaxies, however, are a bit harder to find. Before our sun and Earth were formed, scientists believe that so-called “monstrous galaxies” existed with star formation rate hundreds of thousands of times quicker than we observe today in our own Milky Way Galaxy. Currently, no monstrous galaxies exist in modern world, but astronomers believe that these young galaxies have matured to form giant elliptical galaxies seen in the modern universe. Existing galaxy formation theories predict that these monstrous galaxies form in special environments with the concentration of dark matter.

The research team that discovered the new galaxies was led by Hideki Umehata, a postdoctoral fellow of the Japan Society for the Promotion of Science staying at the European Southern Observatory, Germany, Kotaro Kohno, a professor at the University of Tokyo, and Yoichi Tamura, an assistant professor at the University of Tokyo. The three scientists used ALMA to make extensive observations of a small part of the sky called SSA22 in the constellation Aquarius. The shape of the cluster found by the astronomers indicates the presence of a huge 3D web of invisible dark matter, which is thought to be a progenitor of large scale structures in the universe.

Current galaxy formation theories predict that these monstrous galaxies form in special environments where dark matter is concentrated. But up until now, it has been difficult to determine the positions of active star forming galaxies with enough precision to actually test this prediction. Part of the problem is that monstrous star-forming galaxies are often obscured in dust, making them difficult to observe in visible light. Dusty galaxies do emit strong radio waves with submillimeter wavelengths, but radio telescopes typically have not had the resolution needed to pin-point individual galaxies.

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.

The researchers have determined that since modern galaxies are monstrous ones, their origination must also have been in the nexuses in large structures. Using this supposition, the gravitational location of the massive dark matter intersection was revealed by ALMA where the galaxies are found to be inside a knot of this dark matter, as filaments intersect with each other. The scientists now hope that they will be able to find more of the dark matter-bathed galaxies to further study the phenomena.

The research team has published their discovery of the dark matter-bathed galaxies in the The Astrophysical Journal.