2021ApJS..253....2H

We have selected 43 southern massive star-forming regions to study the spatial distribution of HNCO 4₀₄-3₀₃, SiO 2-1, and HC₃N 10-9 line emission and to investigate their spatial association with the dust emission. The morphology of HNCO 4₀₄-3₀₃ and HC₃N 10-9 agrees well with the dust emission. HC₃N 10-9 tends to originate from more compact regions than HNCO 4₀₄-3₀₃ and SiO 2-1. We divided our sources into three groups: those in the Central Molecular Zone (CMZ), those associated with bubbles (Bubble), and the remaining sources, which are termed "normal star-forming regions" (NMSFR). These three groups, subdivided into three different categories with respect to line widths, integrated intensities, and column densities, hint at the presence of different physical and chemical processes. We find that the dust temperature T_d, and the abundance ratios N_HNCO/N_SiO and N_HNCO/N_HC3N show a decreasing trend toward the central dense regions of CMZ sources, while N_HC3N/N_SiO moves in the opposite direction. Moreover, a better agreement is found between T_d and N_HC3N/N_SiO in Bubble and NMSFR category sources. Both outflow and inflow activities have been found in eight of the 16 bubble and NMSFR sources. The low outflow detection rate indicates either that in these sources the SiO 2-1 line wing emission is below our sensitivity limit or that the bulk of the SiO emission may be produced by the expansion of an H II region or supernova remnant, which has pushed molecular gas away, forming a shock and yielding SiO.