Observation of complex organic molecules containing peptide-like bonds towards hot core G358.93--0.03 MM1

Abstract

In the star formation regions, the complex organic molecules that contain peptide bonds (–NH–C(=O)–) play a major role in the metabolic process because –NH–C(=O)– is connected to amino acids (R-CHNH2–COOH). Over the past few decades, many complex organic molecules containing peptide-like bonds have been detected in hot molecular cores, hot corinos, and cold molecular clouds, however, their prebiotic chemistry is poorly understood. We present the first detection of the rotational emission lines of formamide (NH2CHO) and isocyanic acid (HNCO), which contain peptide-like bonds towards the chemically rich hot molecular core G358.93–0.03 MM1, using high-resolution and high-sensitivity Atacama Large Millimeter/submillimeter Array (ALMA) bands 6 and 7. We estimate that the column densities of NH2CHO and HNCO towards G358.93–0.03 MM1 are (2.80±0.29)×10^{15} cm^{−2} and (1.80±0.42)×10^{16} cm^{−2} with excitation temperatures of 165±21 K and 170±32 K, respectively. The fractional abundances of NH2CHO and HNCO towards G358.93–0.03 MM1 are (9.03±1.44)×10^{−10} and (5.80±2.09)×10^{−9}. We compare the estimated abundances of NH2CHO and HNCO with the existing three-phase warm-up chemical model abundance values and notice that the observed and modelled abundances are very close. We conclude that NH2CHO is produced by the reaction of NH2 and H2CO in the gas phase towards G358.93–0.03 MM1. Likewise, HNCO is produced on the surface of grains by the reaction of NH and CO towards G358.93–0.03 MM1. We also found that NH2CHO and HNCO are chemically linked towards G358.93–0.03 MM1.