Various H¹³CO⁺ abundance profiles (left panels) and the resulting simulated integrated emission along the northeastern part of the radial cut shown in Fig. 2 (right panels). The observed emission is shown in purple. The location of the abundance jumps (in Kelvin and AU) is indicated in the top right corners. Bottom panel: temperature (gray) and density (blue) profiles for the IRAS2A envelope from Kristensen et al. (2012) used in the top two models. The location of the H₂ O and CO snowlines (at 100 K and 20 K, resp.) are indicated by the dotted red and blue lines, respectively. The temperature profile increased by a factor of 2.2, used in the bottom two models, is shown in black. The resulting H₂ O snowline is indicated by the dashed red line while the CO snowline now falls outside the adopted radial range. For IRAS2A, 1′′ corresponds to ~250 AU.