Status and perspectives of the CRAFTS extra-galactic HI survey

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is expected to complete its commissioning in 2019. FAST will soon begin the Commensal Radio Astronomy FasT Survey (CRAFTS), a novel and unprecedented commensal drift scan survey of the entire sky visible from FAST. The goal of CRAFTS is to cover more than 20000 deg² and reach redshift up to about 0.35. We provide empirical measurements of the beam size and sensitivity of FAST across the 1.05 to 1.45 GHz frequency range of the FAST L-band array of 19-beams (FLAN). Using a simulated HI-galaxy catalogue based on the HI Mass Function (HIMF), we estimate the number of galaxies that CRAFTS may detect. At redshifts below 0.35, over 6 × 10⁵ HI galaxies may be detected. Below the redshift of 0.07, the CRAFTS HIMF will be complete above a mass threshold of 10^9.5M_⊙. FAST will be able to investigate the environmental and redshift dependence of the HIMF to an unprecedented depth, shedding light onto the missing baryon and missing satellite problems.