SURVEY OBSERVATIONS OF A POSSIBLE GLYCINE PRECURSOR, METHANIMINE (CH₂NH)

Abstract

We conducted survey observations of a glycine precursor, methanimine, or methylenimine (CH 2 NH), with the Nobeyama Radio Observatory 45 m telescope and the Sub-Millimeter Radio telescope toward 12 high-mass and two low-mass star-forming regions in order to increase the number of known CH 2 NH sources and to better understand the characteristics of CH 2 NH sources. As a result of our survey, CH 2 NH was detected in eight sources, including four new sources. The estimated fractional abundances were ∼10 −8 in Orion KL and G10.47+0.03, while they were ∼10 −9 toward the other sources. Our hydrogen recombination line and past studies suggest that CH 2 NH-rich sources have less (this mean not so evolved) evolved H II regions. The lower destruction rates from UV flux from the central star would contribute to the high CH 2 NH abundances toward CH 2 NH-rich sources. Our gas-grain chemical simulations suggest that CH 2 NH is mostly formed in the gas phase by neutral-neutral reactions, rather than being the product of thermal evaporation from dust surfaces.

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

“…Peak abundance of gas phase methanimine is found to be around 1.81 × 10 −09 . Our obtained values can be compared with the recent hot-core observation of methanimine ∼ 7.0 × 10 −08 in G10.47+0.03 and 3.0 × 10 −9 in NGC6334F by Suzuki et al (2016).…”

“…The simplest amino acid, namely, glycine could have been formed by the reaction between methanimine and formic acid (Godfrey et al 1973). In that sense, methanimine is the precursor molecule for glycine (Suzuki et al 2016). Similarly, from the CH 5 N isomeric group, methylamine (CH 3 NH 2 ) was detected (Kaifu et al 1974;Fourikis et al 1974) in both Sgr B2 and Orion A.…”

“…1972). Recently, Suzuki et al (2016) pointed out that this species could be produced on the interstellar ice by other reactions (R1-R3) shown in Table 1.…”

“…In the ISM, methylamine may be formed via two successive hydrogen addition reactions of methanimine in the ice phase (Godfrey et al 1973;Suzuki et al 2016). Woon (2002) determined that the primary step of this hydrogen addition reaction may proceed in two ways.…”

Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

“…Small molecules such as CS, OCS, H 2 CO, HDCO, H 2 CS, and c-C 3 H 2 (cyclopropenylidene) have been observed in the centimeter band toward this cloud (Angerhofer et al 1978;Goldsmith & Linke 1981;Madden et al 1989;Chandler et al 1993;Richardson et al 1994;Mehringer et al 1995;Wootten & Mangum 2009 (Kalenskii et al 1997(Kalenskii et al , 2000a(Kalenskii et al , 2000bSlysh et al 1999Slysh et al , 2002van der Tak et al 2000;Ikeda et al 2001;Alakoz et al 2002;Charnley 2004;Kalenskii & Johansson 2010a;Wirström et al 2011;Zapata et al 2012;Girart et al 2013;Suzuki et al 2016). Kalenskii & Johansson (2010a) found low to moderate rotational temperatures, 9-56K, for most molecules detected.…”