MIT Investigates The Origins Of A Rare Type Of Dwarf Galaxy

Researchers at MIT, the University of California at Riverside, and other institutions have been investigating dwarf galaxies. As the name implies, a dwarf galaxy is small and very dim compared to a typical galaxy and contains only a fraction of the number of stars found in the Milky Way. While most dwarf galaxies are typically very small, there is a type called ultra-diffuse galaxies or UDGs that can be scattered over gigantic regions of space.

A UDG is difficult to detect because they are spread over such vast areas of space, but most have been discovered within clusters of larger galaxies. Astronomers from MIT and the other institutions are now using highly detailed simulations to detect quenched UDGs, a rare type of dwarf galaxy that no longer generates stars. Interestingly, the simulations discovered several systems of this type. Astronomers found the galaxies weren't in clusters. Instead, they were found in virtually empty regions of the universe.

Their isolation is contrary to predictions of how quenched UDGs should form. Researchers leverage their simulations to perform another task by using them to reverse the evolution of the UDGs to see how they were created. Simulations led the astronomers to believe quenched UDGs probably formed in dark matter halos with an unusually high angular momentum.

The momentum could have spun dwarf galaxies into unusually stretched-out patterns. The UDGs are believed to have evolved within the galaxy clusters as most do. However, interactions inside the cluster are believed to have ejected the dwarf galaxies out into the vastness of space. That ejection created a "backsplash" orbit that curves like a boomerang. The same process is also believed to have stripped the gas inside the galaxy away, leaving them unable to produce stars.