a) Variation of derived CH₃OH column densities with respect to different rotational temperatures toward dM-1. The corresponding [CH₂DOH]/[CH₃OH] abundance (derived in population diagrams) ratios are shown in red. The best-fit result corresponds to a CH₃OH column density of 2.1 × 10¹⁸ cm^-2 and a temperature of about 60 K. For temperatures lower than 200 K, the differences in the derived column densities are clearly smaller than a factor of about 3. The [CH₂DOH]/[CH₃OH] abundance ratios derived from different temperatures are lower than 1.1 × 10^-3. b) Variation of the relative abundance (based on the ratio of two transitions of CH₂DOH and CH₃OD as seen in Fig. 3e of the two isotopologs toward dM-1 as a function of the adopted temperatures. Note that this ratio does not depend much on the temperature.