The Institute of Astrophysics of Andalusia discovers a possible galactic fossil near Andromeda

In the Local Group, which is the group of galaxies to the Milky Way and to which the neighboring Andromeda belongs, there has been a huge increase in the number of faint dwarf galaxies detected over the past two decades. However, the numbers are still not consistent with the theoretical predictions that would have predicted a higher number of these types of galaxies. A new, unusually faint galaxy was discovered at the fringes Of Andromeda. This discovery opens up the possibility that the "lost" satellite galaxies are due to limitations in current instruments' detection capabilities. .

Michelle Collins, an astronomer at University of Surrey, UK, and the first author of this paper, says that "we have found an extremely dim galaxy, PegasusV" (Pegasus V) was formed early in the history of our universe. An astronomical survey was not designed to find such a faint galaxies around the Andromeda Galaxy for the first time.

Amateur astronomer Giuseppe Donatiello discovered an intriguing "spot" near the Andromeda Galaxy's edges in archive data using the naked eye. A larger device was then activated. "Our search was based on the visual inspections of the DESI Legacy Surveys deep images, which have allowed us to locate more that a dozen candidates. -says David Martinez Delgado Talentia Senior researcher at IAA-CSIC, who is responsible for the dwarf galaxy detection program. These galaxies are partially resolved in the images due to their distance and low stellar densities. They have not been noticed by similar automatic search algorithms. We need 8-meter telescopes to confirm these galaxies.

This find is a great example of the positive relationship between amateur and professional Astronomy. Donatiello's systematic searches of the archives have already revealed six candidates for dwarf galaxies.

Deeper observations made with the Gemini North telescope revealed faint stars and old stars in the newly discovered Pegasus V. This confirmed that the galaxy is an ultrafaint dwarf located near the Andromeda galaxy. The data also showed that the galaxy is extremely low in elements heavier than hydrogen or helium, compared to other galaxies. This means that it could be very old.

These galaxies, which are the faintest of all galaxies, are thought to be fossils of the first galaxies that formed. They also provide clues about the formation of the stars. Although faint galaxies such as Pegasus V are believed to be abundant in the universe they have yet to discover as many as expected. David Martinez-Delgado (IAA–CSIC) says that if there are less faint galaxies than expected, it could be a problem in understanding cosmology or dark matter. It is therefore important to find examples of faint galaxies. They are difficult to spot because they appear as scattered stars in large images of the sky.

Michelle Collins (U. Surrey) says, "We hope that further analysis of the chemical characteristics of PegasusV will provide clues regarding the earliest periods in star formation in the universe." This tiny fossil galaxy can help us to understand how galaxies are formed and whether our knowledge of dark matter is accurate.

These types of faint galaxies will be more easily seen by future astronomical instruments. Pegasus V witnessed what is known as reionization in the history and evolution of the universe. Other objects from that time period will soon be viewed with NASA's James Webb Space Telescope. The Vera C. Rubin Observatory, NOIRLab-NSF, will also be conducting a decade-long survey to the sky and discover other faint galaxies similar to Pegasus V.