Constraints of the Formation and Abundances of Methyl Carbamate, a Glycine Isomer, in Hot Corinos

Abstract

Methyl carbamate CH 3 OC(O)NH 2 is an isomer of glycine. Quantum chemical analyses show that methyl carbamate is a more stable isomer than glycine. Because of this, there could be a higher chance for methyl carbamate to exist in the interstellar medium (ISM) as compared to glycine. Despite immense searches, until now glycine has not been detected in the ISM; therefore, it is worthwhile to search its isomer methyl carbamate. In this paper, we present the constraints of methyl carbamate formation under the interstellar conditions. Large complex organic molecules are favorably produced in hot-corino environments of low-mass protostars. We for the first time carried out astrochemical modeling focusing on the formation of methyl carbamate in physical conditions similar to hot-corino objects. Consequently, we examined ALMA archival data for existing spectral line observations toward hot corinos NGC 1333 IRAS 4A2 and IRAS 16293B. Within the common spectral range toward these sources, we found three features are possibly related to the spectral transitions of methyl carbamate and consequently estimate the upper limit of column densities. Results of chemical modeling are consistent with the observational upper limit of estimated column density/abundance toward the sources. This may hint the validation of the proposed formation mechanism. Future observations using a telescope like ngVLA may confirm the presence of MC toward the hot corinos.