Formamide (NH2<\/sub>CHO) is the simplest amide containing a peptide bond, which is important to form proteins from amino acids. Formamide has been regarded as a prebiotic molecule for a long time. The formation and destruction processes of NH2<\/sub>CHO are important to understand how prebiotic molecules can form from simple molecules in the Universe. However, its formation process in the Universe is controversial. Several possible formation pathways of NH2<\/sub>CHO have been considered; e.g., successive hydrogenation reactions of HNCO on dust surfaces, and the gas-phase reaction between H2<\/sub>CO and NH2<\/sub>. One of the possible solutions to investigate the formation processes of molecules is to investigate correlations among molecules, which are likely pairs of parent species and daughter species. The methods that have been used for the investigation of correlations among COMs formed on dust surfaces suffer from a third variable that the interpretation of the observed correlations difficult. Thus, statistical studies need to be revisited.<\/p>\n\n\n\n
Dr. Sanhueza leads the Digging into the Interior of Hot Cores with ALMA (DIHCA) survey project, which covers 30 high-mass star-forming regions with ALMA Band 6. In Taniguchi et al. (2023) published in ApJ, we have analyzed the NH2<\/sub>CHO, HNCO, H2<\/sub>CO, and CH3<\/sub>CN lines obtained by the DIHCA project. In general, NH2<\/sub>CHO and HNCO show more spatially compact emission compared to that of CH3<\/sub>CN and H2<\/sub>CO (Figure 1). We have derived molecular abundances at each hot molecular core (HMC) and investigated correlations among the previously mentioned molecules. We have found strong correlations between NH2<\/sub>CHO and HNCO and between NH2<\/sub>CHO and H2<\/sub>CO (Figure 2). In order to confirm their chemical links, we have applied a partial correlation test so that we can exclude the temperature effect. These pairs of molecules show high correlation coefficients (\u03c1=0.89 and 0.84 for pairs of NH2<\/sub>CHO-HNCO and NH2<\/sub>CHO-H2<\/sub>CO, respectively). Thus, we have clearly shown that these three species are tightly chemically linked in the hot dense gas around high-mass protostars. We propose that partial correlation tests are useful to investigate correlations among COMs formed on dust surfaces.<\/p>\n\n\n\n We have run chemical simulations to find out how they are linked. The HNCO molecules convert to NH2<\/sub>CHO molecules by hydrogen-addition reactions, and NH2<\/sub>CHO can go back to HNCO by hydrogen abstraction reactions. This mechanism is called the dual-cyclic hydrogen addition and abstraction reactions. In addition, NH2<\/sub>CHO can be formed by the gas-phase reaction between H2<\/sub>CO and NH2<\/sub> in the hot dense gas. Figure 3 shows the schematic view of relationships among these three species around high-mass protostars.<\/p>\n\n\n\n Related Links:<\/p>\n\n\n\n arXiv: http:\/\/arxiv.org\/abs\/2304.00267<\/a><\/p>\n\n\n\n![\"\"](\"https:\/\/sci.nao.ac.jp\/main\/wp-content\/uploads\/2023\/04\/fig1.png\")
![\"\"](\"https:\/\/sci.nao.ac.jp\/main\/wp-content\/uploads\/2023\/04\/fig2.png\")
![\"\"](\"https:\/\/sci.nao.ac.jp\/main\/wp-content\/uploads\/2023\/04\/fig3.png\")
![\"\"](\"https:\/\/sci.nao.ac.jp\/main\/wp-content\/uploads\/2023\/04\/dihca_logo-1024x332.png\"){kind=logo}
<\/figure>\n\n\n\n