Identification of pre-biotic molecules containing Peptide-like bond in a hot molecular core, G10.47+0.03

Abstract

After hydrogen, oxygen, and carbon, nitrogen is one of the most chemically active species in the interstellar medium (ISM). Nitrogen bearing molecules have great importance as they are actively involved in the formation of biomolecules. Therefore, it is essential to look for nitrogen-bearing species in various astrophysical sources, specifically around high-mass star-forming regions where the evolutionary history is comparatively poorly understood. In this paper, we report observation of three potential pre-biotic molecules, namely, isocyanic acid (HNCO), formamide (NH 2 CHO), and methyl isocyanate (CH 3 NCO), which contain peptide-like bonds (-NH-C(=O)-) in a hot molecular core, G10.47+0.03 (hereafter, G10). Along with the identification of these three complex nitrogen-bearing species, we speculate their spatial distribution in the source and discuss their possible formation pathways under such conditions. Rotational diagram method under LTE condition has been employed to estimate the excitation temperature and the column density of the observed species. Markov Chain Monte Carlo method was used to obtain the best suited physical parameters of G10 as well as line properties of some species. We also determined the hydrogen column density and the optical depth for different continuum observed in various frequency ranges. Finally, based on these observational results, we have constructed a chemical model to explain the observational findings. We found that HNCO, NH 2 CHO, and CH 3 NCO are chemically linked with each other.

Radiative transfer modeling of the observed line profiles in G31.41+0.31

“…Detailed chemical modeling has been carried out to study the abundances of the species observed in G31. Our Chemical Model for Molecular Cloud (CMMC) (Das et al, 2015a(Das et al, ,b, 2016Gorai et al, 2017a,b;Sil et al, 2018;Gorai et al, 2020;Sil et al, 2021;Das et al, 2021) is considered for this modeling. 2013) and infall velocity variation is derived from the Equation 1 by using v 1000 = 4.9 km s −1 .…”

“…The time evolution of the physical parameters (H 2 density and temperature) are considered in three significant steps: isothermal collapsing phase, warm-up phase, and post-warmup phase. This type of straightforward model is best suited to study the chemical evolution of hot cores (Gorai et al, 2020;Sil et al, 2021). As discussed in Section 2.2, the gas cloud envelope is divided into 23 spherical shells.…”

“…This is the first exclusive modeling result in explaining the observed abundance of CH 3 SH and CH 3 NCO in G31. Here, for the chemical evolution of CH 3 NCO and CH 3 SH, the pathways mentioned in Gorai et al (2020) and Gorai et al (2017a) are used. The peak abundance profile of CH 3 SH shows a similar trend as the CH 3 OH.…”

“…The peak and final abundance of CH 3 NCO show similar value because of its formation during the simulation's late stages by the reaction between HNCO and CH 3 in the gas phase (with a rate ∼ 5 × 10 −11 cm 3 s −1 ) cm 3 s −1 . Here, the activation barrier for the reaction between H and NH 2 CHO is used at its highest value (3130 K), as mentioned in Gorai et al (2020). A peak abundance of ∼ 3.3 × 10 −8 for CH 3 NCO is obtained at around 6000 AU.…”

“…These species can quickly transfer to the gas phase in the warmer region (temperature > 100 K). Significant production of gas-phase CH 3 NCO can be processed after the release of grain phase HNCO (Gorai et al, 2020). So the gas-phase abundance of these three species depends mainly on the chemical process related to the grain.…”