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FAST Telescope Unveils World’s Largest Extragalactic Hydrogen Catalogue
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New Release of the FASHI Survey
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Guizhou, China, has issued the second batch of data from its FAST All-Sky H I Survey (FASHI). The release adds 156,411 extragalactic neutral-hydrogen sources, a figure roughly five times the total detected by the former Arecibo survey. The catalogue is publicly accessible, giving astronomers a broad new pool for studies of galaxy formation and the cosmic web.
From Arecibo to FAST: Shifting the Reference Standard
For more than half a century, the 305-metre Arecibo dish in Puerto Rico served as the primary instrument for mapping neutral hydrogen, most notably through the ALFALFA survey conducted from 2005 to 2012. Arecibo’s collapse in 2020 ended its observational role. FAST, which surpassed Arecibo in aperture in 2016, now provides the leading reference, covering about three times the sky area of ALFALFA and detecting galaxies that are smaller, fainter, and more distant.
Scale of the New Dataset
- 156,411 extragalactic H I sources in the latest batch.
- Nearly five-fold increase over the total Arecibo detections.
- Three-times larger sky coverage than ALFALFA.
These figures illustrate the dramatic expansion of observable neutral-hydrogen data, bridging the gap between earlier surveys and the forthcoming Square Kilometre Array (SKA) projects in Australia and South Africa.
Scientific Implications
The enlarged sample enables more precise investigations of how the cosmic web formed, why some galaxies sustain star formation while others quench, and how gas flows shape galaxy evolution across cosmic time.
Official Outlook
The study reporting the FASHI release appeared in *Science China Physics, Mechanics & Astronomy* this month. The authors emphasize that the publicly available catalogue will support global collaboration, offering an unprecedented resource for both current analyses and future high-resolution observations with next-generation radio facilities.