A team of researchers led by Associate Professor Kazuhiro Nakazawa Nagoya University/KMI and graduate school of science doctoral student Yuki Omiya have made significant advances in understanding galaxy clusters. The National Astronomical Observatory of Japan collaborates with respected institutions such as Tokyo University of Science, Hiroshima University, and Saitama University. Jaxa Institute of Space and Astronautical Science, Tokyo Metropolitan University, and the Netherlands Institute for Space Sciences, Toho University, have succeeded in estimating the size and merger velocity of a newborn shock wave in the galaxy cluster CIZA J1358.9-4750. This effort allowed them to measure an astonishing 2.3 × 10 energies.38 W. Data for this research were obtained from the European X-ray Astronomy Satellite XMM-Newton.
Galaxy clusters and their significance
Known as the largest self-gravitating objects in the Universe, galaxy clusters are vast expanses of high-temperature gas. This gas emits brilliant X-rays, making these clusters visible. When these giant clusters merge, it results in an unparalleled astronomical event, creating a shock wave 3 million light-years across.
A complex measurement of astronomical objects
In astronomy in general, measuring the depth of celestial objects poses a major challenge. However, in this study, the team overcame this difficulty by capitalizing on the recent collision of the two clusters. This event made it possible to make reasonable calculations about the actual shape of the clusters. Using these figures, they determined the speed of the shock front by analyzing the temperature distribution of the high-temperature gas. They multiplied this value by the length, width, and depth of the clusters to calculate the amount of kinetic energy converted into heat, particle acceleration, and magnetic-field amplification at the shock front.
This research was published in the February 2023 issue of Publications of the Astronomical Society of Japan (PASJ).. In a related paper, Kurahara et al. (PASJ, December 2022) detected “synchrotron radio emission” using accelerated electrons and amplified magnetic fields around the shock front. Its luminosity is estimated to be ~3.5 × 1033 W. These results give us a conversion efficiency of about 10-5.
Understanding the distribution of transition efficiencies can help us elucidate what happens in the largest shock wave in a cluster merger.
Reference: Yuki Omiya, Kazuhiro Nakazawa, Kyoko Matsushita, Shogo B. Kobayashi, Nobuhiro Li Okabe, Kosuke Sato, Takayuki Tam, Takayuki, Takayuki, Takayuki Tam, Takayuki, Takayuki, Takayuki, Takayuki Tam, Takayuki Tam, Takayuki Ta Am, Takayuki, Takayuki Tam kuya Akahori, Kohei Kurahara, Tomohiro Yamaguchi, 1 December 2022, Publications of the Astronomical Society of Japan.