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 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.

Digging into the Interior of Hot Cores with ALMA: Spiral Accretion into the High-mass Protostellar Core G336.01–0.82

“…For the zeroth moment map we used a variable integration window of twice the line FWHM for data over 5σ rms with σ rms = 2.6 mJy beam −1 and the whole velocity range for the remaining pixels, while for first and second moment maps we consider only emission over 5σ rms . To determine the line central velocity, we use a systemic velocity of −47.2 km s −1 (determined from 13 CH 3 CN by Taniguchi et al 2023). As shown in Figure 2(b) this velocity is consistent with the velocity at the position of ALMA1.…”

The ALMA-QUARKS Survey. I. Survey Description and Data Reduction

“…The spectral resolution is better than that of the two wide-band SPWs (SPWs 7 and 8) of the ATOMS survey, ∼1.6 km s −1 (Liu et al 2020a). The velocity resolution of the QUARKS survey is high enough to spectrally resolve the emission lines of the outflows and ionized gas whose line wings or line widths are typically larger than 10 km s −1 (Liu et al 2021a(Liu et al , 2022cZhang et al 2022), and the emission of complex organic molecules (COMs) from hot cores (ΔV ∼ 5 km s −1 ; Qin et al 2022;Taniguchi et al 2023). The velocity gradients along the longest branches of HFSs were systematically revealed in the ATOMS survey to be 8.7 km s −1 pc −1 on average (Zhou et al 2022), corresponding to a velocity difference of ∼5 km s −1 at the maximum recovering scale (0.6 pc at a distance of 5 kpc) of the QUARKS survey.…”