Polar plot showing the distribution of the H I-detected and optical galaxies in the RA – cz and Dec – cz planes. The z range of the survey is split in two for clarity. Large squares of different colour show galaxies with spectroscopic redshift from SDSS and with stellar mass M_⋆ ≥ 9.75 M_⊙ with the colour indicating their local density according to the colour bar. Small black points show optical galaxies with stellar mass below this limit. Small brown points mark potential optical counterparts without optical redshift. Certain H I detections are shown with empty, black squares, uncertain ones with empty, dark-grey circles. The light-grey shaded areas of the map show areas where the ability to detect H I signal is reduced (see text for details). The figure is meant to be viewed on a (large) screen. [Link]