Capturing the start of galaxy rotation in the early universe

July 1 () –

Astronomers have detected the most distant rotation of galaxies ever observed, which suggests an initial stage of development of the rotational movement.

After the Big Bang came the first galaxies. Due to the expansion of the universe, these galaxies are moving away from us. This causes their emissions to be redshifted (shifted towards longer wavelengths).

By studying these redshifts, it is possible to characterize the “motion” within galaxies, as well as their distance. In a new study, Waseda University astronomers have now revealed a likely rotational motion of one of those distant galaxies.

As telescopes have become more advanced and powerful, astronomers have been able to detect more and more distant galaxies. These are some of the earliest galaxies to form in our universe that began to move away from us as the universe expanded.

In fact, the greater the distance, the faster a galaxy appears to be moving away from us. Interestingly, we can estimate how fast a galaxy is moving and, in turn, when it formed based on how “redshifted” its emission appears. This is similar to a phenomenon called the “Doppler shift,” where objects moving away from an observer emit light that appears shifted toward longer wavelengths (hence the term “redshift”) to the observer.

The Atacama Large Millimeter/submillimeter Array (ALMA) telescope, located in the middle of the Atacama desert in Chile, it is particularly well suited to observing such redshifts in emissions from galaxies.

Recently, a team of international researchers has observed redshifted emissions from a distant galaxy, MACS1149-JD1 (hereafter JD1), which has led them to some interesting conclusions. “Beyond finding high redshift galaxies, that is, very distant, studying their internal movement of gas and stars provides motivation to understand the galaxy formation process in the earliest possible universe”, explains the author of the study. Richard S. Ellis of University College London. The findings have been published in The Astrophysical Journal Letters.

Galaxy formation begins with the accumulation of gas and continues with the formation of stars from that gas. Over time, star formation progresses from the center outward, a galactic disk develops, and the galaxy takes on a particular shape. As star formation continues, newer stars form in the spinning disk while older stars remain in the center. By studying the age of stellar objects and the movement of stars and gas in the galaxy, it is possible to determine the stage of evolution that the galaxy has reached.

Making a series of observations over a two-month period, the astronomers successfully measured small differences in “redshift” from one position to another within the galaxy and found that JD1 met the criteria for a galaxy dominated by the rotation. They then modeled the galaxy as a spinning disk and found that it reproduced the observations very well. The calculated rotational speed was about 50 kilometers per second, which was compared to the rotational speed of the Milky Way’s disk of 220 kilometers per second. The team also measured JD1’s diameter at just 3,000 light-years, much smaller than the Milky Way’s at 100,000 light-years across.

The significance of their result is that JD1 is by far the most distant source and thus the oldest found so far that has a rotating disk of gas and stars. Along with similar measurements of closer systems in the research literature, this has allowed the team to delineate the gradual development of rotating galaxies over more than 95% of our cosmic history.

Furthermore, the mass estimated from the galaxy’s rotation rate was in agreement with the stellar mass previously estimated from the galaxy’s spectral signature, and came predominantly from that of “mature” stars that formed a few years ago. 300 million years. “This shows that the stellar population of JD1 formed even earlier in the cosmic era,” Hashimoto says.

“JD1’s rotation rate is much slower than that found in galaxies of later epochs and in our galaxy, and JD1 is likely to be in an early stage of developing a rotational motion,” says Inoue. it’s a statement. With the recently launched James Webb Space Telescope, astronomers now plan to pinpoint the locations of young and oldest stars in the galaxy to verify and upgrade your galaxy formation scenario.