Observation of Complex Organic Molecules Containing Peptide-like Bonds Toward Hot Core G358.93$-$0.03 MM1

TL;DR

This study reports the first detection of peptide-like bond containing molecules, formamide and isocyanic acid, in a hot core, providing insights into their formation pathways and prebiotic chemistry in star-forming regions.

Contribution

First detection of NH2CHO and HNCO in G358.93-0.03 MM1, with analysis of their abundances and formation mechanisms in a hot molecular core.

Findings

Detected NH2CHO and HNCO with high-resolution ALMA observations.

Observed abundances closely match chemical model predictions.

Identified formation pathways for peptide-like molecules in star-forming regions.

Abstract

In star formation regions, the complex organic molecules (COMs) 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-CHNH$_{2}$$-$COOH). Over the past few decades, many COMs containing peptide-like bonds have been detected in hot molecular cores (HMCs), hot corinos, and cold molecular clouds, however, their prebiotic chemistry is poorly understood. We present the first detection of the rotational emission lines of formamide (NH$_{2}$CHO) and isocyanic acid (HNCO), which contain peptide-like bonds toward the chemically rich HMC G358.93$-$0.03 MM1, using high-resolution and high-sensitivity Atacama Large Millimeter/submillimeter Array bands 6 and 7. We estimate that the column densities of NH$_{2}$CHO and HNCO toward G358.93$-$0.03 MM1 are (2.80$\pm$0.29)$\times$10$^{15}$ cm$^{-2}$ and (1.80$\pm$0.42)$\times$10$^{16}$ cm$^{-2}$ with excitation temperatures of 165 $\pm$ 21 K and 170 $\pm$ 32 K, respectively. The fractional abundances of NH$_{2}$CHO and HNCO toward G358.93$-$0.03 MM1 are (9.03$\pm$1.44)$\times$10$^{-10}$ and (5.80$\pm$2.09)$\times$10$^{-9}$. We compare the estimated abundances of NH$_{2}$CHO and HNCO with the existing three-phase warm-up chemical model abundance values and notice that the observed and modelled abundances are very close. We conclude that NH$_{2}$CHO is produced by the reaction of NH$_{2}$ and H$_{2}$CO in the gas phase toward G358.93$-$0.03 MM1. Likewise, HNCO is produced on the surface of grains by the reaction of NH and CO toward G358.93$-$0.03 MM1. We also find that NH$_{2}$CHO and HNCO are chemically linked toward G358.93$-$0.03 MM1.