Survey Observations of a Possible Glycine Precursor, Methanimine (CH2NH)
Abstract
We conducted survey observations of a glycine precursor, methanimine or methylenimine (CH2NH), with the NRO 45 m telescope and the SMT telescope towards 12 high-mass and two low-mass star-forming regions in order to increase number of CH2NH sources and to better understand the characteristics of CH2NH sources. As a result of our survey, CH2NH was detected in eight sources, including four new sources. The estimated fractional abundances were ~108 in Orion KL and G10.47+0.03, while they were ~109 towards the other sources. Our hydrogen recombination line and past studies suggest that CH2NH-rich sources have less evolved HII regions. The less destruction rates by UV flux from the central star would be contributed to the high CH2NH abundances towards CH2NH-rich sources. Our gas-grain chemical simulations suggest that CH2NH is mostly formed in the gas-phase by neutral-neutral reactions rather than the product of thermal evaporation from the dust surfaces.
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