Left: moment-zero map (primary beam corrected) of the H I emission of HCG 16 calculated using a 3σ_rms mask in each channel (this mask is intended only for visual purposes, the whole analysis uses the SoFiA-generated mask shown in the right panel). The black ellipse in the lower right corner indicates the beam size (37.2″ × 30.3″ or 10.0 kpc × 8.1 kpc) and the small red cross shows the centre of the GBT pointing from Borthakur et al. (2010). The extended features that we separated from the galaxies are indicated by arrows, with the exception of the emission joining galaxies HCG 16c and d. The filled black circle and the white plus sign indicate the pointing centres of the VLA D and C array data respectively. Right: moment -zero contours (uncorrected for primary beam) overlaid on a DECaLS r-band image. In this case the map was generated using the SoFiA-generated mask described in Sect. 3.1, which includes more extended emission. The galaxies in the main band of H I emission going from top-right (NW) to bottom-left (SE) are: HCG 16b, a, c, d, NGC 848, and the single galaxy to the lower right of the group is PGC 8210. Contour levels: −2.45, 2.45, 9.80, 24.4, 49.0, 73.5, and 98.0 × 10¹⁹ cm⁻², where 2.2 × 10¹⁹ cm⁻² corresponds to the 3σ sensitivity in one channel. In order of increasing flux the contours are coloured: black (dashed), black, blue, purple, red, orange, and yellow.