Survey Observation of CH${}_3$NH${}_2$ and Its Formation Process

Abstract

We present the observational result of a glycine precursor, methylamine (CH${}_3$NH${}_2$), together with methanol (CH${}_3$OH) and methanimine (CH${}_2$NH) towards high-mass star-forming regions, NGC6334I, G10.47+0.03, G31.41+0.3, and W51~e1/e2 using ALMA. The molecular abundances toward these sources were derived using the rotational diagram method and compared with our state-of-the-art chemical model. We found that the observed ratio of "CH${}_3$NH${}_2$/CH${}_3$OH" is in between 0.11 and 2.2. We also found that the observed "CH${}_3$NH${}_2$/CH${}_3$OH" ratio agrees well with our chemical model by considering the formation of CH${}_3$NH${}_2$ on the grain surface via hydrogenation process to HCN. This result clearly shows the importance of hydrogenation processes to form CH${}_3$NH${}_2$. NGC63343I MM3, where CH${}_3$NH${}_2$ was not detected in this study and showed "CH${}_3$NH${}_2$/CH${}_3$OH" ratio of less than 0.02, is clearly distinguished from the other cores.

Submitted to ApJ