Column densities for the six methylamine transitions plotted versus temperature. This plot is made for a 3σ limit of 0.1 K km s^-1, as found for W3(H₂O). This figure demonstrates that the 8₂ − 8₁ transition (green) gives the most sensitive limits on column density for the relevant range of excitation temperatures in hot cores, when observed. The other five transitions (4₂→ 4₁, black; 7₂→ 7₁, gold; 10₂→ 10₁, cyan; 2₂→ 2₁, blue and 6₂→ 6₁, red) clearly imply higher column densities. Only below 40 K does the 2₂→ 2₁ line give lower column density limits.