H I moment maps of HCG 91. The left panels show all sources detected by SoFiA. The right panels show sources within the rectangular box shown on the left to better show the central part of the group. The top panels show the column density maps with contour levels of (4.6  ×  10¹⁸, 9.2  ×  10¹⁸, 1.8  ×  10¹⁹, 3.7  ×  10¹⁹, 7.4  ×  10¹⁹, 1.5  ×  10²⁰, 3.0  ×  10²⁰) cm⁻². The contours are overlaid on DECaLS DR10 I-band optical images. The bottom panels show the moment one map. Each individual source has its own colour scaling and contour levels to highlight any rotational component.