Radial temperature profile of dust core 1 in HMPO IRAS 18089. The profiles extracted from the HCN-to-HNC intensity ratio (Fig. 3), CH₃CN (Fig. 4), and (Fig. 5) temperature maps are shown by black circles, green squares, and blue diamonds, respectively. The inner unresolved region (one beam radius) is shown as a gray-shaded area. The vertical dashed purple line indicates the outer radius, rout, based on the continuum (Table C.1). A power-law fit and its 1σ uncertainty to resolved and radially decreasing profiles is shown by the solid and dashed red lines, respectively (Sect. 5.3). The figures for the remaining sources are shown in Fig. C.1.