Digging into the Interior of Hot Cores with the ALMA (DIHCA). III. The Chemical Link between NH2CHO, HNCO, and H2CO

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 ∼0.″3 obtained by the Atacama Large Millimeter/submillimeter Array 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 ( ρ = 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.

Keywords

• Astrochemistry
• Interstellar molecules
• Massive stars
• Star formation