China's FAST telescope builds world's largest neutral hydrogen catalog

Chinese researchers have recently constructed the world’s largest-ever high-quality catalog of neutral hydrogen (HI) sources beyond our Galaxy using China’s home-developed Five-hundred-meter Aperture Spherical Radio Telescope (FAST). They have shared the observational data with researchers in the field of galaxies and cosmology worldwide, as reported by the media on Thursday.

The work is part of a project called the FAST All Sky HI Survey (FASHI), which took only three years, from August 2020 to June 2023, to complete a sky survey covering approximately 7,600 square degrees and discovering a total of 41,741 HI sources. The sum of samples exceeds similar ones around the world in both quantity and quality.

The current survey results are derived from about 35 percent of the total sky, and it is expected that more than 100,000 HI sources will be recorded over the next five years.

Hydrogen, the most abundant element in the universe, is a key component of galaxies. Within disk galaxies, HI is a significant part of the interstellar medium.

China's FAST is a powerful tool for detecting faint and weak HI in galaxies. Compared to previous HI surveys, FAST's survey has higher spectral and spatial resolution, broader coverage, and more reliable and comprehensive data quality.

The research team has already shared a variety of data acquired by FAST with other research fellows in the field. This data is significant in potentially addressing a number of astrophysical issues, such as the possible properties of dark matter, faint unknown galaxies, as well as cosmic structure and evolution.

The findings were recently published in the journal SCIENCE CHINA Physics, Mechanics and Astronomy. Researchers from Guizhou University, the National Astronomical Observatories under the Chinese Academy of Sciences, and Peking University all contributed to the study.

FAST is the world's largest single-dish radio telescope, with a reception area equal to 30 standard football fields. FAST officially began operating on January 11, 2020, in a naturally deep and round karst depression in Southwest China's Guizhou Province.