CSST Large-Scale Structure Analysis Pipeline: I. Constructing Reference Mock Galaxy Redshift Surveys

In this paper, we set out to construct a set of reference mock galaxy redshift surveys (MGRSs) for the future Chinese Space-station Survey Telescope (CSST) observation, where subsequent survey selection effects can be added and evaluated. This set of MGRSs is generated using the dark matter subhaloes extracted from a high-resolution Jiutian N-body simulation of the standard lambda-cold dark matter cosmogony with Omega(m) = 0.3111, Omega(Lambda) = 0.6889, and sigma(8) = 0.8102. The simulation has a box size of 1 h(-1) Gpc, and consists of 6144(3) particles with mass resolution 3.723 x 10(8) h(-1) M-circle dot. In order to take into account the effect of redshift evolution, we first use all 128 snapshots in the Jiutian simulation to generate a light-cone halo/subhalo catalogue. Next, galaxy luminosities are assigned to the main and subhalo populations using the subhalo abundance matching (SHAM) method with the DESI (Dark Energy Spectroscopic Instrument) z-band luminosity functions at different redshifts. Multiband photometries, as well as images, are then assigned to each mock galaxy using a 3D parameter space nearest-neighbour sampling of the DESI LS (Legacy Imaging Survey) observational galaxies and groups. Finally, the CSST and DESI LS survey geometry and magnitude limit cuts are applied to generate the required MGRSs. As we have checked, this set of MGRSs can generally reproduce the observed galaxy luminosity/mass functions within 0.1 dex for galaxies with L > 10(8) h(-2) L-circle dot (or M-* > 10(8.5) h(-2) M-circle dot) and within 1 sigma level for galaxies with L < 10(8) h(-2) L-circle dot (or M-* < 10(8.5) h(-2) M-circle dot). Together with the CSST slitless spectra and redshifts for our DESI LS seed galaxies that are under construction, we will set out to test various slitless observational selection effects in subsequent probes.