H I emission column densities at the positions of the continuum sources plotted against continuum peak flux. The column densities are not corrected for inclination. Red triangles indicate detections. Circles indicate non-detections towards unresolved non-Hα sources, with filled symbols for i < 70° and open symbols for i ≥ 70°. Small stars indicate Hα star-forming regions, and small circles indicate resolved sources not associated with Hα. Filled circles mark the ‘clean’ sample of unresolved non-Hα sources in low-inclination galaxies. The horizontal dashed line shows the 3σ over 16 km s⁻¹ column density limit of log(N_H I/cm⁻²) = 19.77.