The FAST all sky H I survey (FASHI)

The FAST All Sky HI survey (FASHI) was designed to cover the entire sky observable by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), spanning approximately 22000 square degrees of declination between -14{deg} and +66{deg}, and in the frequency range of 1050-1450MHz, with the expectation of eventually detecting more than 100000 HI sources. Between August 2020 and June 2023, FASHI had covered more than 7600 square degrees, which is approximately 35% of the total sky observable by FAST.

It has a median detection sensitivity of around 0.76mJy/beam and a spectral line velocity resolution of ~6.4km/s at a frequency of ~1.4GHz. As of now, a total of 41741 extragalactic HI sources have been detected in the frequency range 1305.5-1419.5MHz, corresponding to a redshift limit of z<0.09. By cross-matching FASHI sources with the Siena Galaxy Atlas (SGA) and the Sloan Digital Sky Survey (SDSS) catalogs, we found that 16972 (40.7%) sources have spectroscopic redshifts and 10975 (26.3%) sources have only photometric redshifts.