Faint galaxies lurking in the dark
Dark matter (red), gas (green), and stars (white) in a HESTIA simulation of the Local Group. The simulated counterparts of the Milky Way and Andromeda are near the center of the image, and the ultra-diffuse galaxies are marked with circles. | © Image: Dr. Noam Libeskind

Faint galaxies lurking in the dark

12. May 2023 | by Susanna Fischerauer

News from space: An international team led by Dr. Noam Libeskind has made a prediction using the most accurate cosmological simulations that sheds new light on our understanding of the universe: Several faint galaxies are waiting to be discovered in the immediate vicinity of the Milky Way!

The study focuses on ultra-diffuse galaxies. These are low-luminosity galaxies with masses of up to a billion suns - about one-thousandth the mass of the Milky Way. Because they span an area the size of our Milky Way, they are very faint and have been difficult to detect to date.

Researchers believe that within the so-called Local Group, great discoveries still await us. The Local Group is a small cluster of galaxies that currently includes about 60 known galaxies, including our home galaxy, the Milky Way, and neighboring galaxy Andromeda. So far, only two ultra-diffuse galaxies are known to exist in the Local Group. The team believes that knowing the total number of ultra-diffuse galaxies in the Local Group is critical to our understanding of the universe.

So how many more are lurking in our cosmic backyard? To find out, researchers have been studying state-of-the-art simulations of our cosmic neighborhood. The HESTIA simulations, named after the ancient Greek goddess of the house, are the most accurate simulations of the Milky Way and its immediate surroundings that currently exist. And the predictions of the simulations are promising: there could be as many as 12 ultra-diffuse galaxies in the Local Group just waiting to be discovered! After a first analysis of the properties of the faint galaxies, the team is certain: even more detailed observations of these galaxies are possible here! This could be accomplished using existing data from surveys such as the international collaborative Sloan Digital Sky Survey project.

The discovery of these new galaxies is promising! Thus, the new knowledge could have significant implications for our understanding of the formation and evolution of the universe. Current models suggest that up to half of the low-mass galaxies in the universe may be extended and diffuse. However, most of them will not be observable with current technical capabilities. This makes it all the more important to obtain more data on the faint galaxies to back up important predictions of various cosmological models.


Original publication:

Newton, O., Cintio, A.D., Cardona-Barrero, S., Libeskind, N.I., Hoffman, Y., Knebe, A., Sorce, J.G., Steinmetz, M., Tempel, E. (2022). The undiscovered ultra-diffuse galaxies of the Local Group. ApJL 946 L37