Cosmological Prediction of the Void and Galaxy Clustering Measurements in the CSST Spectroscopic Survey

Abstract The void power spectrum is related to the clustering of low-density regions in the large-scale structure (LSS) of the Universe and can be used as an effective cosmological probe to extract information on the LSS. We generate galaxy mock catalogs from a Jiutian simulation and identify voids using the watershed algorithm for studying the cosmological constraint strength of the China Space Station Telescope spectroscopic survey. The galaxy and void autopower spectra and void−galaxy cross-power spectra at z = 0.3, 0.6, and 0.9 are derived from the mock catalogs. To fit the full power spectra, we propose to use the void average effective radius at a given redshift to simplify the theoretical model, and we adopt the Markov Chain Monte Carlo technique to implement the constraints on the cosmological and void parameters. The systematic parameters, such as galaxy and void biases and noise terms in the power spectra, are also included in the fitting process. We find that our theoretical model can correctly extract the cosmological information from the galaxy and void power spectra, which demonstrates its feasibility and effectivity. The joint constraint accuracy of the cosmological parameters can be improved by ∼20% compared to that of the galaxy power spectrum only. The fitting results of the void density profile and systematic parameters are also well constrained and consistent with the expectation. This indicates that the void-clustering measurement can be an effective complement to the galaxy-clustering probe, especially for the next-generation galaxy surveys.