Astronomers detect the most distant rotation of galaxies in history, suggesting an early stage of rotational motion development.
Astronomers have been able to detect more and more distant galaxies as telescopes have become more advanced and powerful. Since light travels at a finite speed and we see objects as they were when the light was emitted, the further away something is, the further back in time we are seeing. Therefore, these very distant galaxies are some of the first galaxies to form in our universe, which 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. East red shift it is similar to a phenomenon called the “Doppler shift”, where objects moving away from an observer emit light that appears shifted towards longer wavelengths (hence the term “redshift”) to the observer.
Located in the middle of the Atacama Desert in Chile, the Atacama Large Millimeter/submillimeter Array ([{” attribute=””>ALMA) telescope is especially well-suited for observing such redshifts in galaxy emissions. Recently, an international research team observed redshifted emissions of a distant galaxy, MACS1149-JD1 (hereafter JD1), which has led them to some fascinating conclusions. “Beyond finding high-redshift, namely very distant, galaxies, studying their internal motion of gas and stars provides motivation for understanding the process of galaxy formation in the earliest possible universe,” explains Ellis.
The team of international researchers included Professor Akio Inoue and graduate student Tsuyoshi Tokuoka from Waseda University, Japan, Dr. Takuya Hashimoto at the University of Tsukuba, Japan, Professor Richard S. Ellis at University College London, and Dr. Nicolas Laporte, a research fellow at the University of Cambridge, UK. The findings of their study have been published in The Astrophysical Journal Letters.
After the Big Bang came the earliest galaxies. Due to the expansion of the universe, these galaxies are receding 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 the galaxies as well as their distance. In a new study, astronomers at Waseda University have now revealed a likely rotational motion of one such distant galaxy. Credit: Waseda University
Galaxy formation starts with the accumulation of gas and proceeds with the formation of stars from that gas. Over time, star formation progresses from the center outward, a galactic disk develops, and the galaxy acquires a particular shape. As star formation continues, newer stars form in the rotating disk while older stars remain in the central part. It is possible to determine the stage of evolution the galaxy has reached by studying the age of the stellar objects and the motion of the stars and gas in the galaxy.
After conducting a series of observations over a period of two months, the astronomers successfully measured small differences in the “redshift” from position to position inside the galaxy. They found that JD1 satisfied the criterion for a galaxy dominated by rotation. Next, the scientists modeled the galaxy as a rotating disk and discovered that it reproduced the observations very well. The calculated rotational speed was about 50 kilometers per second (110,000 miles per hour), which was compared to the rotational speed of the
Furthermore, the mass estimated from the rotational speed of the galaxy was in line with the stellar mass previously estimated from the galaxy’s spectral signature, and came predominantly from that of “mature” stars that formed about 300 million years ago. “This shows that the stellar population in JD1 formed at an even earlier epoch of the cosmic age,” says Hashimoto.
“The rotation speed of JD1 is much slower than those found in galaxies in later epochs and our Galaxy and it is likely that JD1 is at an initial stage of developing a rotational motion,” says Inoue. With the recently launched DOI: 10.3847/2041-8213/ac7530