Detection of New Methylamine (CH$_3$NH$_2$) Sources: Candidates for Future Glycine Surveys

TL;DR

This study reports the detection of methylamine (CH₃NH₂) in interstellar space, identifying new sources and analyzing their abundance, which supports its role as a precursor to glycine, aiding future searches for amino acids in space.

Contribution

First detection of methylamine in the source G10.47+0.03 with hyperfine components observed, supporting theoretical predictions and advancing the search for glycine precursors.

Findings

G10.47+0.03 is the most abundant methylamine source known.

Detected hyperfine components of methylamine for the first time.

Observed abundance aligns with theoretical models.

Abstract

It has been a long-standing problem to detect interstellar glycine (NH$_2$CH$_2$COOH), the simplest amino acid, in studying a possible relation between the Universe and origin of life. In the last about 40 years all surveys of glycine failed, and it would be an alternative strategy to search for precursor(s) to glycine. Such studies of precursors would be crucial prior to conducting sensitive surveys by ALMA. Laboratory studies have suggested that CH$_3$NH$_2$ is a possible precursor to glycine. Further theoretical study also suggested that the CH$_2$NH$_2$ radical that can be formed from CH$_3$NH$_2$ through photodissociation can be a good precursor to glycine. Thus we observed CH$_3$NH$_2$ towards several hot core sources by using the Nobeyama 45m radio telescope, and succeeded in finding a new CH$_3$NH$_2$ source, G10.47+0.03, with its fractional abundance of 2.4+-0.6x10^{-8}; at the time of writing, this source is the most abundant source of CH$_3$NH$_2$ ever known. We also found another new source of CH$_3$NH$_2$, NGC6334F, however, the detection may be tentative since the signal-to-noise ratios are not sufficient to claim secure detection. Detailed analysis of the detected data revealed the detection of the hyperfine components of CH$_3$NH$_2$ for the first time. We found that the observed abundance of CH$_3$NH$_2$ agrees fairly well with the theoretically predicted value by Garrod (2013). Detectability of interstellar glycine is discussed.