All-sky map of the Galactic neutral hydrogen (H I) column density from the HI4PI survey, overlaid with the clean RRM sample (757 sources). Positive and negative RRMs are shown with red and blue circles, respectively, with the circle size proportional to |RRM|. The sky coverage of the sources is limited in declination by the SPICE-RACS upper limit of ∼ + 49°, and the lower limit of −18° is from DESI. In addition, the source scarcity in some low HI density regions is due to the patchy coverage in the DESI DR1 observations (see DESI Collaboration 2026, fig. 3, top panel).