SIMBAD references

We have analyzed the NH₂CHO, HNCO, H₂CO, and CH₃CN (¹³CH₃CN) molecular lines at an angular resolution of ∼0.″3 obtained by the Atacama Large Millimeter/submillimeter Array Band 6 toward 30 high-mass star-forming regions. The NH₂CHO 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 CH₃CN 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 NH₂CHO and HNCO (ρ = 0.89) and between NH₂CHO and H₂CO (0.84) have been found. These strong correlations indicate their direct chemical links; dual-cyclic hydrogen addition and abstraction reactions between HNCO and NH₂CHO and gas-phase formation of NH₂CHO from H₂CO. Chemical models including these reactions can reproduce the observed abundances in our target sources.