Although over the last two decades there has been an explosion in the detection of faint dwarf galaxies in the Local Group, the group of galaxies to which the Milky Way belongs, their number is still not in agreement with theoretical predictions. .
Now, an unusual ultrafaint galaxy has been discovered on the fringes of Andromeda, and its finding opens the possibility that the problem of these “lost” satellite galaxies is due to limitations in the detection capabilities of currently available instruments. . It has been called Pegasus V, it contains very few heavy elements.
It is likely to be a fossil of the first galaxies
“We have found an extremely faint galaxy, Pegasus V, whose stars formed very early in the history of the universe. This is the first time that such a faint galaxy has been found around the Andromeda galaxy by an astronomical survey that was not designed specifically for the task,” said Michelle Collins, an astronomer at the University of Surrey, UK, and first author. from the article.
“Our search is based on visual inspection of deep images from the DESI Legacy Surveys , which has enabled us to locate more than a dozen satellite galaxy candidates of Andromeda or its companion galaxy M33 so far. Due to their distance and low stellar density, these galaxies appear partially resolved in the images, and have gone unnoticed by the automatic search algorithms of similar projects. To confirm them, we need deep images taken with eight-meter telescopes, such as the Gemini North in Hawaii”, explains David Martínez-Delgado, Talentia Senior researcher at the IAA-CSIC who heads the dwarf galaxy detection project.
Deeper observations taken with the Gemini North telescope revealed old, faint stars in the newly found Pegasus V, and confirmed that it is an ultra-faint dwarf galaxy with few elements heavier than hydrogen and helium compared to larger galaxies. similar, so it is probably a fossil of the first galaxies in the universe.
“We hope that further study of the chemical properties of Pegasus V will provide clues about the earliest periods of star formation in the universe. This small fossil galaxy from the early universe may help us understand how galaxies form and whether our understanding of dark matter is correct ,” Collins concludes.
Referencia: Michelle L. M. Collins1et al. “Pegasus V – a newly discovered ultra-faint dwarf galaxy on the outskirts of Andromeda”. Monthly Notices of the Astronomical Society, 2022. https://arxiv.org/abs/2204.09068
