An article published in the journal Nature reports the observations of a team of researchers who have studied the functioning and origin of so-called “ultra-diffuse” galaxies, far from any other galactic system. These little-known galaxies nestle in remote areas of the Universe and remain relatively unknown to this day.
They are unknown to the public but nevertheless arouse the curiosity of astronomers. The Ultra Diffuse Galaxies (in French ultra-diffuse galaxies or UDG) yet intrigue researchers, who have just unveiled the origins of these systems in a study published on September 6 in Nature Astronomy. Scientists, divided among the Massachusetts Institute of Technology (MIT) and the University of California, analyzed the functioning of UDGs thanks to a cosmological simulation called hydrodynamic. They thus determined that some of these galaxies, the most remote in theUniverse, originally came from galactic clusters or gravitated around more massive galaxies before leaving their environment to drift alone in the cosmos.
Mysterious dwarf galaxies
The discovery of the first ultra-diffuse galaxy took place in 1984. These UDGs bear this name because of their particular characteristics: if their galactic disc can reach the size of our Milky Way, they only have a limited number. ofstars within them and therefore a mass reduced stellate. These ultra-diffuse galaxies are devoid of gas allowing the formation ofstars, such as hydrogen, carbon monoxide or even molecules d’ammoniac. Some UDGs had already been talked about in 2018 and 2019, when the publication of studies on the halos of black matter encompassing galaxies. Astronomers then noted that certain ultra-diffuse galaxies “merged” with dark matter, this one infiltrating in the galactic disc.
MIT researchers looked at the most remote UDGs in the Universe, some being thousands of miles away. parsecs other systems or galactic clusters. The majority of these solitary galaxies are bluish in color, since they harbor young stars; other UDGs that are part of clusters or satellites of more massive galaxies tending to have a red color. This difference is linked to the interactions between the different systems in clusters: some galaxies can amputate gas necessary for the birth of stars at UDGs. Devoid of these precious components, ultra-diffuse red galaxies are because they only contain old stars, likeAntares and Betelgeuse.
A mystery with several megaparsecs
MIT researchers therefore expected to find “blue” UDGs by simulating the most isolated regions of the Universe. But, to everyone’s surprise, a large portion of the simulated galaxies turned out to be tending to red, about 25%. The cosmological simulation developed by American researchers, called TNG50, was therefore used to “go back in time” and understand how red UDGs could have found themselves so far away from other galaxies. Like others galaxies naines, the observed ultra-diffuse galaxies have extricated themselves from the attraction of clusters, but the violent process has robbed them of part of their gas and molecular clouds. Once solitary, the UDG will then enter a orbit into a boomerang and are therefore theoretically prepared to return to their starting point.
If the phenomenon explaining the ejection of these galaxies as well as the role of dark matter in the formation of diffuse galaxies remains unclear, MIT researchers should conduct new simulations to determine if a greater number of UDGs roam between galactic systems.
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