Radial temperature profiles. 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, r_out, of the continuum (Table C.1). A power-law fit and its 1σ uncertainty to resolved and radially decreasing profiles are shown by the solid and dashed red lines, respectively (Sect. 5.3). The radial temperature profile of dust core 1 in HMPO IRAS 18089 is shown in Fig. 6.