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∼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(\unitMpc/h)−3 at z∼0.3. We cross-correlate the foreground-removed radio intensity with the CSST galaxies, including both the whole sample, and red and blue galaxy sub-samples separately. We find that in all cases the HI and optical galaxies are well correlated. The total HI abundance can be measured with a high precision from this correlation. A relative error of ∼0.6% for ΩHI could be achieved at z∼0.3 for an overlapping survey area of 10000\unitdeg2.
@article{arxiv.2207.14566,
title = {Forecasting the Cross-Correlation of the CSST galaxy survey with the FAST HI Intensity Map},
author = {Furen Deng and Yan Gong and Yougang Wang and Shuting Dong and Ye Cao and Xuelei Chen},
journal= {arXiv preprint arXiv:2207.14566},
year = {2022}
}