Scientists Solve Astronomical Difficulties with One Rocket, Revealing the First Generation Galaxy and Dark Matter Array | Telescope | Galaxy
The picture shows the first antenna of a square kilometer array radio telescope.
How did the first generation of galaxies in the universe form? What are the properties of dark matter? Can these two mysteries be studied and revealed simultaneously through astronomical observations?
Recently, Chinese astronomers proposed that by measuring the one-dimensional power spectrum of a 21 centimeter forest, future square kilometer array radio telescopes will be able to simultaneously reveal the properties of the first generation galaxies and dark matter in the universe. The relevant research is published in the international academic journal Nature Astronomy.
Detecting 21 centimeter forests has always faced great challenges
There is a large amount of neutral hydrogen gas in the universe. The transition of hydrogen atoms in these gases between ground state energy levels and hyperfine structures generates electromagnetic wave length of 21 centimeters, which is the neutral hydrogen 21 centimeter line.
The 21 centimeter neutral hydrogen line provides a huge opportunity for astronomers to explore the universe. "The neutral hydrogen 21cm line provides a unique means for detecting the cosmic dawn and the first generation of galaxies. At the same time, using the neutral hydrogen 21cm line to detect the cosmic dawn and re ionization is also one of the most important scientific goals of the square kilometer array radio telescope." Chen Xuelei, co communication author of the paper and researcher of the National Astronomical Observatory of the Chinese Academy of Sciences, said.
At the same time, various structures in the early universe and their surrounding hydrogen atomic gases would generate dense 21 centimeter absorption lines in the spectrum of high redshift radio point sources. "These absorption line clusters are vividly referred to as 21 centimeter forests by astronomers," said Chen Xuelei. For many years, detecting 21 centimeter forests has been facing great challenges.
"There are two main reasons: one is that the 21cm forest signal is weak, and it is difficult to obtain the radio bright source in the dawn of the universe on which it depends; the other is that the 21cm forest signal is affected by the heating effect of the first generation galaxy and the nature of dark matter at the same time, so it is difficult for us to distinguish the two effects in observation. This makes it difficult for the 21cm forest detection to actually limit the heating effect of the first generation galaxy or the nature of dark matter." explained Xu Yidong, co corresponding author of the paper and associate researcher of the National Astronomical Observatory of the Chinese Academy of Sciences.
In recent years, a group of quasars with high redshift radio noise have been discovered, and the square kilometer array radio telescope has also entered the engineering construction stage. It is urgent to carry out 21 centimeter forest exploration.
In this study, Chinese astronomers proposed an innovative statistical measurement scheme that allows the 21 centimeter forest to not only limit the properties of the first generation galaxies in the universe, but also simultaneously measure the mass of dark matter particles.
New methods are expected to expand human understanding of the universe
"We realize that there are significant differences in the spectral scale distribution characteristics caused by the heating effect of the first generation galaxies and the signal changes caused by warm dark matter. Through one-dimensional power spectrum analysis, we can statistically distinguish these two in the future," Xu Yidong introduced.
"The one-dimensional power spectrum of a 21 centimeter forest can indeed be a win-win cosmological probe, providing a highly promising new way to unravel the mysteries of dark matter and first generation galaxies," emphasized Zhang Xin, a professor at Northeastern University and co author of the paper.
In response to this study, Professor Katherine Mack from the Canadian Institute of Circle Theory Physics commented, "This study proposes an interesting method that can use the 21 centimeter forest power spectrum to simultaneously limit the heating of cosmic X-rays on intergalactic media, as well as the possible effects of warm and dark matter. Although previous studies have examined the possibility of 21 centimeter forests as probes for intergalactic media, including the warm and dark matter effect as an independent signal provides a new scientific goal for future observations."
The editorial team of Nature Astronomy also commented on this study: "The farthest part of our universe is always extremely mysterious, difficult to observe directly due to being blocked by dust, light absorbing atoms, and gases in the intermediate medium. This study transforms absorption into an advantage, using it to break the degeneracy of different effects encountered by other methods and can be used to elucidate the structural formation of the early universe."
Researchers say that the development of this breakthrough method is of great significance for unraveling the mysteries of dark matter and the formation of early celestial bodies in the universe, and will further advance our understanding of dark matter, revealing the process of the formation and evolution of the universe's structure. Through deeper observation and analysis, we are expected to gain more insights into the properties of dark matter and early galaxy formation in the near future, further expanding our understanding of the universe.
