CO (2-1) emission towards B15-10. The cube used for the analysis was imaged with natural weighting and with a smoothing of four channels (i.e. resulting in a spectral resolution of ∼90 km/s). We present the detection spectrum in the top panel, and the velocity-integrated flux map (moment-0, M0) and the velocity map (moment-1, M1) are shown in the bottom left and right panels, respectively. Both maps have the same size (i.e., 3.4″ wide, or ∼29 kpc). The moment-0 contours are overlaid on both maps (solid black contours indicate levels at $3\times \sqrt{(}{2)}^n\times$ RMS, where n = 0,  1, …,  and the dashed white contours indicate −3σ). The maps are centred at the position reported by Bacon et al. (2015). The top panel with the spectrum displays a filled spectrum within which the flux was integrated and the moments were obtained. The vertical dashed red line at zero velocity assumes the light-weighted centre frequency, and the dotted vertical red line shows the expected frequency assuming the MUSE-derived redshift. The horizontal shaded grey region shows ±1 times the STD. The thick line shows the single-component Gaussian best fit for the raw spectral resolution (∼24 km/s) cube, and the dashed line shows this for the four-channel-smoothed cube.