χ² plots of H₂O over the different regions of the disk (top left: region 1, top right: region 2, bottom left: region 3, bottom right: region 4). The red, yellow, and green lines indicate the 1σ, 2σ, and 3σ confidence contours, respectively. The white contours show the emitting radii in astronomical units (0.1 to 2.0 au). The black cross corresponds to the best fit. The black dotted line corresponds to the upper limit of the column density based on the H₂¹⁸O and H₂¹⁶O flux ratio as described in Sect. 3.1.