They are thought to originate in the haloes surrounding galaxies, which are probably too faint and can't be seen directly. However, light from quasars behind the cluster is absorbed by magnesium atoms in the halo gas of the galaxies. The scientists cautioned that these results still need to pass peer review. They must also be confirmed with a larger data sample, ideally toward other large quasar groups. This allows Williger, Campusano, Clowes and their collaborators to further study the relationship between galaxies and quasars in a large group.
Quasars can form from merging galaxies - common in the cores of clusters.
They may also develop from the compression of gas where the edges of clusters of galaxies meet. One model shows that quasars in the distant past should then be found both in the centers and on the edges of galaxy clusters. At later times, as gas in the center of the galaxy clusters forms into actual galaxies, most of the remaining gas should be found on the outskirts of galaxy clusters, and quasars should be found mostly on their peripheries. Information about the galaxies in the large quasar group will help to determine whether this view is correct. At the moment, computer simulations of the formation of large structures in the universe are just starting to deal with sizes as large as this large quasar group.