SIMBAD references

We present the observational results of a precursor of glycine, methylamine (CH₃NH₂), together with methanol (CH₃OH) and methanimine (CH₂NH) for the high-mass star-forming regions NGC 6334I, G10.47+0.03, G31.41+0.3, and W51 e1/e2 using the Atacama Large Millimeter/submillimeter Array. The molecular abundances of these sources were derived using the CASSIS spectrum analyzer and compared with our state-of-the-art three-phase chemical model NAUTILUS. We found that the observed abundance ratio of CH₃NH₂/CH₃OH is between 0.008 and 1.0 for all sources, except for NGC 6334I MM3, where a ratio less than 0.002 is found. This may be due to its later evolutionary stage relative to the other cores. We also found that the observed CH₃NH₂/CH₃OH ratio agrees well with the three-phase chemical model NAUTILUS, which includes the formation of CH₃NH₂ on the grain surface via a series of hydrogenation processes of HCN. This result clearly shows the importance of hydrogenation processes to form CH₃NH₂.