Comparison of power spectrum with different halo mass threshold. On the left, we show the H I power spectrum. On the right, we show the ratio of the power spectrum of the sample with a halo mass threshold and the full sample. The solid curves show the results in real space and the dashed curves show the results in redshift space. Different colors denote different samples with different thresholds. We also include the linear matter power spectrum for reference in cyan color on the left.