The Parameter-free Finger-of-God Model and Its Application to 21 cm Intensity Mapping

Abstract

© 2020. The American Astronomical Society. Using the galaxy catalog built from ELUCID N-body simulation and the semianalytical galaxy formation model, we have built a mock H i intensity mapping map. We have implemented the Finger-of-God (FoG) effect in the map by considering the galaxy H i gas velocity dispersion. By comparing the H i power spectrum in redshift space with a measurement from the IllustrisTNG simulation, we have found that the FoG effect can explain the discrepancy between current mock maps built from the N-body simulation and the IllustrisTNG simulation. Then we built a parameter-free FoG model and a shot-noise model to calculate the H i power spectrum. We found that our model can accurately fit both the monopole and quadrupole moments of the H i matter power spectrum. Our approach to building the mock H i intensity map and the parameter-free FoG model will be useful for upcoming 21 cm intensity mapping experiments, such as CHIME, Tianlai, BINGO, FAST, and SKA. It is also vital for studying nonlinear effects in 21 cm intensity mapping