Integrated intensity maps for a spherically symmetric ring-shaped H¹³CO⁺ distribution. Emission simulated with the radiative transfer code Ratran is convolved with the observed beam (left panel), and simulated with the (u, v) coverage of the NOEMA observations (right panel). The southern peak in the simulations is probably not observed owing to presence of water in the outflow (see text for details). The continuum peak is denoted with a cross, and the beam is shown in the bottom left corner.