Detection and chemical modelling of complex prebiotic molecule cyanamide in the hot molecular core G31.41+0.31

Abstract

In the interstellar medium (ISM), the complex prebiotic molecule cyanamide (NH${}_2$CN) plays a key role in producing adenine (C${}_5$H${}_5$N${}_5$), purines (C${}_5$H${}_4$N${}_4$), pyrimidines (C${}_4$H${}_4$N${}_2$), and other biomolecules via a series of reactions. Therefore, studying the emission lines of NH${}_2$CN is important for understanding the hypothesis of the pre-solar origin of life in the universe. We present the detection of the rotational emission lines of NH${}_2$CN with vibrational states $v$ = 0 and 1 towards the hot molecular core G31.41+0.31 using the high-resolution twelve-meter array of Atacama Large Millimeter/Submillimeter Array (ALMA) band 3. The estimated column density of NH${}_2$CN towards G31.41+0.31 using the local thermodynamic equilibrium (LTE) model is (7.21$\pm$0.25)$\times$10${}^{15}$ cm${}^{-2}$ with an excitation temperature of 250$\pm$25 K. The abundance of NH${}_2$CN with respect to H${}_2$ towards G31.41+0.31 is (7.21$\pm$1.46)$\times$10${}^{-10}$. The NH${}_2$CN and NH${}_2$CHO column density ratio towards G31.41+0.31 is 0.13$\pm$0.02. We compare the estimated abundance of NH${}_2$CN with that of other hot cores and corinos and observed that the abundance of NH${}_2$CN towards G31.41+0.31 is nearly similar to that of the hot molecular core G358.93$-$0.03 MM1, the hot corinos IRAS 16293-2422 B, and NGC 1333 IRAS4A2. We compute the two-phase warm-up chemical model of NH${}_2$CN using the gas-grain chemical code UCLCHEM, and after chemical modelling, we notice that the observed and modelled abundances are nearly similar. After chemical modelling, we conclude that the neutral-neutral reaction between NH${}_2$ and CN is responsible for the production of NH${}_2$CN on the grain surface of G31.41+0.31.

Accepted for publication in ACS Earth and Space Chemistry