Power spectra of the galaxy field, 21-cm brightness temperature field, their cross-power spectrum, and the signal-to-noise ratio of the cross-power spectrum as a function of k_∥ and k_⊥ for a fiducial scenario (left to right). Overlaid are various noise-dominated/excluded regions imposed by systematics and observational effects. The 21-cm brightness temperature power spectrum includes cuts showing the three foreground + instrument (i.e. wedge) contamination scenarios we considered. In this illustrative example, the galaxy survey footprint corresponds to ∼1 sq. deg. at z∼6, and the galaxy redshift uncertainty corresponds to δz∼0.01, which is characteristic of slitless spectroscopy.