Digging into the Interior of Hot Cores with ALMA (DIHCA). III: The Chemical Link between NH$_{2}$CHO, HNCO, and H$_{2}$CO

Abstract: We have analyzed the NH${2}$CHO, HNCO, H${2}$CO, and CH${3}$CN ($^{13}$CH${3}$CN) molecular lines at an angular resolution of $\sim 0.3''$ obtained by the Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 toward 30 high-mass star-forming regions. The NH${2}$CHO emission has been detected in 23 regions, while the other species have been detected toward 29 regions. A total of 44 hot molecular cores (HMCs) have been identified using the moment 0 maps of the CH${3}$CN line. The fractional abundances of the four species have been derived at each HMC. In order to investigate pure chemical relationships, we have conducted a partial correlation test to exclude the effect of temperature. Strong positive correlations between NH${2}$CHO and HNCO ($\rho=0.89$) and between NH${2}$CHO and H${2}$CO (0.84) have been found. These strong correlations indicate their direct chemical links; dual-cyclic hydrogen addition and abstraction reactions between HNCO and NH${2}$CHO and gas-phase formation of NH${2}$CHO from H${2}$CO. Chemical models including these reactions can reproduce the observed abundances in our target sources.