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

TL;DR

This study uses ALMA observations to analyze the chemical relationships between NH₂CHO, HNCO, and H₂CO in high-mass star-forming regions, revealing strong correlations and chemical links supported by models.

Contribution

It provides the first detailed analysis of the chemical link between NH₂CHO, HNCO, and H₂CO in hot molecular cores using high-resolution ALMA data.

Findings

Strong correlations between NH₂CHO and HNCO, and NH₂CHO and H₂CO.

Evidence for direct chemical links via hydrogen addition and abstraction reactions.

Chemical models successfully reproduce observed abundances.

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.