“China’s Sky Eye” Spots Farthest Hydrogen Galaxies

China’s FAST Discovers Farthest Hydrogen Galaxies

By Lu Chengkuan, Science and Technology Daily Reporter

“China’s Sky Eye” (FAST) has made a new discovery. On the 10th, it was announced by the National Astronomical Observatory of China, Chinese Academy of Sciences, that based on the observation data from “China’s Sky Eye”, an international research team led by Chinese scientists has discovered a batch of the most distant neutral hydrogen galaxies. The relevant research results have been published online in the Astrophysical Communications journal.

Hydrogen is the earliest element formed in the universe, typically existing in the form of neutral hydrogen. Neutral hydrogen is also an important component of gas circulation in galaxies, providing fuel for star-forming regions and serving as a crucial probe for studying the dynamical structure of galaxies. The rotation curves of neutral hydrogen provide observational evidence for the existence of dark matter, laying a solid foundation for the establishment of the standard cosmological model.

The Parkes Radio Telescope in Australia searched for galaxies within a range of 600 million light-years in the southern hemisphere, detecting approximately 5,000 neutral hydrogen galaxies. The Arecibo Radio Telescope in the United States conducted a search for galaxies within a range of 800 million light-years in the northern hemisphere, detecting approximately 30,000 neutral hydrogen galaxies. These galaxy samples have provided the first distribution of neutral hydrogen galaxy masses, enabling astronomers to systematically study the relationship between neutral hydrogen gas and stellar mass, as well as the star formation rate in galaxies.

This time, the team of the “China’s Sky Eye” Ultra-Deep Sky Survey Project led by researcher Peng Bo from the National Astronomical Observatory of China carried out a deep “blind search” for distant and faint neutral hydrogen galaxies.

“In our survey, we discovered six neutral hydrogen galaxies located approximately 5 billion light-years away from Earth. These are the farthest neutral hydrogen galaxy samples directly detected by the 21-centimeter emission line to date. One of these galaxies has the largest neutral hydrogen mass observed so far,” said Peng Bo.

The project team estimated the density of high-mass neutral hydrogen galaxies in the sample and found that there were more high-mass neutral hydrogen galaxies in the universe 4.2 billion years ago. Through further observations with large optical telescopes in the United States and Russia, researchers successfully identified the optical counterparts of these six distant neutral hydrogen galaxies. This indicates that “China’s Sky Eye” has provided a new pathway for detecting distant neutral hydrogen galaxies.

China's National Astronomical Observatory

(Image source: China’s National Astronomical Observatory)

(Source: Science and Technology Daily)

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