ALMA High-resolution Spectral Survey of Thioformaldehyde (H2CS) toward Massive Protoclusters

Abstract

Investigating the temperature and density structures of gas in massive protoclusters is crucial for understanding the chemical properties therein. In this study, we present observations of the continuum and thioformaldehyde (H _2 CS) lines at 345 GHz of 11 massive protoclusters using the Atacama Large Millimeter/submillimeter Array telescope. High spatial resolution and sensitivity observations have detected 145 continuum cores from the 11 sources. H _2 CS line transitions are observed in 72 out of 145 cores, including line-rich cores, warm cores, and cold cores. The H _2 column densities of the 72 cores are estimated from the continuum emission, which are larger than the density threshold value for star formation, suggesting that H _2 CS can be widely distributed in star-forming cores with different physical environments. The rotation temperature and column density of H _2 CS are derived using the XCLASS software. The results show that the H _2 CS abundances increase as temperature rises and higher gas temperatures are usually associated with higher H _2 CS column densities. The abundances of H _2 CS are positively correlated with its column density, suggesting that the H _2 CS abundances are enhanced from cold cores, warm cores, and line-rich cores in star-forming regions.

Keywords

• Astrochemistry
• Spectral line identification
• Chemical abundances