An article published in the journal “Astronomy & Astrophysics” describes the discovery of a huge galaxy proto-supercluster with a mass close to that of the largest existing structures in the recent universe. A team led by Olga Cucciati of the Italian Institute for Astrophysics, Bologna discovered it thanks to the data collected by the VUDS (VIMOSUltra-Deep Survey) project and named it Hyperion after the titan because it’s really titanic. the researchers estimated that this structure dates back about 2.3 billion years after the Big Bang, the largest and most massive discovered dating back to such a remote era with a mass estimated at over a million billion times the Sun’s.
The VUDS project, led by Olivier Le Fèvre (Aix-Marseille Université, CNRS, CNES) produced a 3D spectroscopic map of over 10,000 very faint galaxies in the distant universe, and as a result we see them as they were billions of years ago. This is one of the uses thought for the VIMOS (VIsible Multi-Object Spectrograph) instrument, mounted on ESO’s VLT (Very Large Telescope) in Chile.
A new technique was developed at the University of California, Davis (UC Davis) to analyze the huge amount of data obtained from the VUDS project and was the one that allowed to discover Hyperion. This galaxy proto-supercluster has a complex structure with at least seven high-density regions that are connected by filaments of galaxies. Another reason of interest is that its size is comparable to that of superclusters close to the Earth but its structure is very different from theirs.
Brian Lemaux of UC Davis, one of the authors of this research, explained that the galaxy superclusters closest to Earth tend to have a much more concentrated mass distribution with clear structural features while in Hyperion the mass is distributed in a much more uniform way in a series of connected blobs populated by loose associations of galaxies. This difference was detected thanks to a comparison based also on the data collected by the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey led by cosmologist Lori Lubin, also from UC Davis and among the authors of the research, which uses telescopes of the Keck Observatory in Hawaii to study the superclusters close to Earth.
The most likely explanation for the difference between Hyperion and the superclusters close to Earth is that Hyperion is young so gravity had relatively little time to gather the matter in denser regions while the nearest superclusters are much older and that process went on for billions of years. In fact, according to Olga Cucciati, it’s surprising that such a large structure had already formed just over two billion years after the Big Bang because it takes a long time for gravity to gather so much material.
All this means that Hyperion must have evolved to become similar to the superclusters closer to Earth but it’s too far for us to see that. At the same time, billions of years ago the neighboring superclusters likely had structures similar to those we see now in Hyperion.
This research provides new information on the early stages of the evolution of galaxy superclusters and could improve current models. These are processes that can have a strong influence on what happens inside the galaxies that form them, and this is important considering that the Milky Way is part of the local supercluster, also known as the Virgo supercluster, which is part of an even larger structure known as the Laniakea supercluster. For this reason, Brian Lemaux and Lori Lubin are continuing the mapping of Hyperion and other such structures to get more details useful for this typer of research.