Discovering the origins of ultra-diffuse solitary galaxies

An article published in the journal Nature reports the observations of a team of scientists who have studied the function and origin of so-called “ultradiffuse” galaxies, far from any other galactic system. These little-known galaxies nestle in remote areas of the universe and remain relatively mysterious to this day.

If the general public does not know them, they still arouse curiosity astronomers. That Ultra diffuse Galaxies (in French ultra-diffuse galaxies or UDG), however, fascinates scientists who have just revealed the origin of these systems in a study published on September 6 in Nature astronomy. The researchers, divided between Massachusetts Institute of Technology (MIT) and the University of California, have analyzed the operation of UDGs using a so-called hydrodynamic cosmological simulation. They thus determined that some of these galaxies, the most distant in the universe, originally came from clusters galaxies or orbited more massive galaxies before leaving their centers to drift alone through 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 special characteristics: if their galactic disk can reach the size of our The Milky Waythey have only a limited number of stars in them and therefore one lot star reduced. These ultra-diffuse galaxies are devoid of gas, allowing the formation ofstarslikehydrogenof carbon monoxide or even molecules ofammonia. Some UDGs had already been talked about in 2018 and 2019, as studies of halos of black fabric includes the galaxies. Astronomers had then noticed that certain ultra-diffuse galaxies “merged” with dark fabricwhere the latter infiltrates the galactic disk.

MIT scientists looked at the most remote UDGs in the universe, some of which are thousands of miles away. parsecs other systems or galactic clusters. The majority of these solitary galaxies are Colour bluish because it contains young stars; other UDGs are part of clusters or satellites in more massive galaxies that tend to have a red color. This difference is related to the interactions between the different systems in clusters: some galaxies can amputate the gas needed for the birth of stars by UDGs. Without these precious components, ultra-diffuse red galaxies are because they contain only ancient stars, such as Antares and Betelgeuse.

A multi-megaparsec mystery

MIT scientists therefore expected to find “blue” UDGs by simulating the most isolated areas of the universe. But to everyone’s surprise, a large proportion of the simulated galaxies turned out to tend towards red, around 25%. The cosmological simulation developed by the American scientists, called TNG50, was therefore used to “go back in time” and understand how red UDGs could have been so far from other galaxies. Like other dwarf galaxies, the observed ultra-diffuse galaxies have detached from the attraction of clusters, but the violent process has deprived them of some of their gases and molecular clouds. When they are alone, the UDGs will then enter one orbit boomerang and are therefore theoretically willing to return to their starting point.

If the phenomenon explaining the expulsion of these galaxies as well as the role of dark matter in the formation of diffuse galaxies is still unclear, MIT researchers should perform new simulations to determine if multiple UDGs roam between galactic systems.

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