Forecasting the Cross-Correlation of the CSST galaxy survey with the FAST HI Intensity Map

Understand

The cross-correlation of optical galaxies with the neutral hydrogen (HI) radiation intensity can enhance the signal-to-noise ratio (SNR) of the HI intensity measurement.

• In this paper, we investigate the cross-correlation of the galaxy samples obtained by the spectroscopic survey of the China Space Station Telescope (CSST) with the HI Intensity mapping (IM) survey of the Five-hundred-meter Aperture Spherical Telescope (FAST).
• Using the IllusitrisTNG simulation result at redshift $0.2 \sim 0.3$, we generate mock data of the CSST survey and a FAST L-band drift scan survey.
• The CSST spectroscopic survey can yield a sample of galaxies with a high comoving number density of $10^{-2} (\unit{Mpc}/h)^{-3}$ at $z \sim 0.3$.