Temperature and density solutions from PyNeb for the spectrum extracted from the center region in Figure 3. Oxygen, sulphur, and nitrogen diagnostics are depicted in green, grey, and blue colors, respectively, with shades representing the 1-σ confidence regions. We note that the T_e [O II] diagnostic shown here might not be trustworthy, if indeed the [O II]λλ3727,3730 emission has a different region of origin than its auroral counterpart (see Section 3.2, Section 4.3). Similar figures for the surrounding regions are shown in Figure C.2.