2023-11-16 07:00:04
Astronomers have discovered the remains of 100 dwarf galaxies, eroded and stripped of their peripheral stars by larger galaxies. This phenomenon sheds light on the evolution of an intriguing category of galaxies, ultra-compact dwarf galaxies (UCDs).
These UCDs, among the densest collections of stars in the Universe, are actually the fossilized remains of normal dwarf galaxies, destroyed during violent gravitational interactions with other galaxies. The existence of UCDs, discovered more than twenty years ago, posed a puzzle for astronomers. These galaxies, smaller and more compact than ordinary dwarf galaxies, but larger than star clusters, appeared to be relics of destroyed dwarf galaxies, but this theory (the word theory comes from the Greek word theorein, which means “to contemplate, observe,…) lacked intermediate evidence.
Diagram of the transformation of an ordinary dwarf galaxy into an ultra-compact dwarf galaxy.
Credit: NOIRLab/NSF/AURA/NASA/R. Gendler/K. Wang/M. Zamani
Astronomers, using the Gemini North telescope at Mauna Kea in Hawaii, searched around for these missing links. avian nomenclature in French (updated) gives…) of the Virgo cluster, a group of around 2000 galaxies located some 65 million light years from Earth. They spotted dozens of dwarf galaxies in full transformation.
Eric Peng, astronomer at NOIRLab and the Kavli Institute for Astronomy and Astrophysics at the University of Beijing (?? ; pinyin: B?ij?ng Listen to the pronunciation…), shares that these results offer a complete picture of the origin of these mysterious galaxies. The 106 small galaxies observed in The Virgo cluster has intermediate sizes between normal dwarf galaxies and UCDs, thus filling the “size gap” between star clusters and galaxies.
The recently identified galaxies appear to be in the early stages of UCD formation. All are located near massive galaxies, indicating that the gravitational influence of the latter has stripped the small cosmic objects of their stars and gas.
Image of the galaxy NGC 3628 or “Hamburger Galaxy”, captured by the VĂctor M. Blanco 4-meter telescope, showing its stellar tidal tail (Stellar Tide is a science fiction novel by American author David Brin… ) containing the ultra-compact dwarf galaxy NGC 3628-UCD1.
Credit: CTIO/NOIRLab/DOE/NSF/AURA
Laixiang Wang, researcher at Peking University, specifies that the analysis of Gemini observations made it possible to eliminate any background contamination. , revealing that these transitional galaxies exist almost exclusively near larger galaxies. This indicates that environmental transformation plays a key role.
By putting these observations in a temporal sequence, the researchers reconstructed the history of these galaxies stolen from stars. “It’s exciting to finally be able to see this transformation in action,” Peng concludes. “This tells us that many of these UCDs are visible fossil remains of ancient dwarf galaxies in galaxy clusters. , and our results suggest that there are likely still many low-mass remains to be discovered.”
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