Bargraph plot of the integrated main-beam intensities for the six investigated methylamine transitions. values were calculated for a total column density of 3.4 × 10¹⁷ cm^-2 as inferred toward G31.41+0.31 from the 6₂ → 6₁ transition, assuming a rotational temperature of 120 K. The horizontal line shows the 0.077 K km s^-1 3σ value for G31.41+0.31. It is unlikely that the detection of the 236 408 feature (green) in this hot core is methylamine, since the main-beam intensities of other CH₃NH₂ transitions are above the 3σ value. Particularly the 4₂ → 4₁ and 2₂ → 2₁ transition (blue) should be visible in our spectra. The remaining transitions (red) are either below detection limit or not observed toward this source.

Blow-up of the spectral region around the 2₂→ 2₁ transition at 237143 MHz of all analysed hot cores. Despite being a particularly strong transition, it was not observed in any of the spectra.

211 to 373 GHz spectrum of methylamine, covering ALMA bands 6 and 7. A column density of 10¹⁵ cm^-2, T_rot and beam size of 1′′ are used.