Beginning of the rotation of galaxies in the early universe

(ORDO NEWS) — In a new study, a team of scientists analyzed the motions of gas and stars in the very distant galaxy MACS1149-JD1 (JD1 for short), providing a deeper understanding of the formation and evolution of galaxies, including the beginning of their rotation in the early evolutionary stages.

The formation of galaxies begins with the accumulation of gas and then proceeds as stars form from this gas. Over time, stars begin to form in more and more distant regions of the galaxy, the galactic disk develops, and the galaxy takes on a specific shape.

As stars continue to form, new stars predominantly form in the rotating disk, while older stars remain in the central part of the galaxy. By studying the age of stellar objects, together with the movement of stars and gas in the galaxy, one can get an idea of ​​the evolutionary stage that the galaxy has reached.

After conducting a series of observations over a two-month period, astronomers led by Tsuyoshi Tokuoka of Waseda University, Japan, were able to successfully measure small changes in the redshift of material within the galaxy’s boundaries and found that JD1 satisfies the criteria for a rotation-dominated galaxy.

At the next stage of the study, they produced a simulation of a galaxy in the form of a rotating disk and found a high accuracy of agreement with the observations.

The calculated rotation speed was approximately 50 kilometers per second, which is comparable to the rotation speed of the Milky Way disk, estimated at 220 kilometers per second. The team also measured the diameter of the JD1 galaxy, which, according to this estimate, was only about 3,000 light-years. For comparison,

The significance of the results obtained is that the JD1 galaxy is by far the most distant and, therefore, the earliest source, in the study of which it was possible to distinguish a rotating disk of gas and stars.

Combining these findings with similar studies of nearby systems reported in the scientific literature allowed the team to model the gradual evolution of rotating galaxies over more than 95 percent of the history of the cosmos.

Moreover, the mass calculated from the estimate of the rotational speed of the galaxy showed a good agreement with the mass of the stars of the galaxy, obtained earlier from the spectral data, and most of it is “mature” stars that formed about 300 million years ago.

“This shows that the stellar population in the JD1 galaxy formed at an even earlier epoch in the history of the universe,” said study co-author Dr. Takuya Hashimoto of the University of Tsukuba.

Since the rotation rate of the JD1 galaxy is much lower than the rotation rate of galaxies observed in later epochs of the evolution of the Universe, including our Galaxy, it is quite possible that the JD1 galaxy is at the initial stage of development of rotational motion, the authors suggest.


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