Dense Outflowing Molecular Gas in Massive Star-forming Regions

TL;DR

This study uses submillimeter observations of dense gas tracers in 33 massive star-forming regions to detect outflows in 76% of cases, analyzing their properties and correlations with core mass.

Contribution

It provides the first large-scale mapping of dense outflows in massive star-forming regions using HCN 3-2 and HCO$^+$ 3-2 lines, establishing their properties and correlations.

Findings

Outflows detected in 76% of sources.

Strong correlation between outflow mass and core mass.

Quantitative estimates of outflow properties like momentum and energy.

Abstract

Dense outflowing gas, traced by transitions of molecules with large dipole moment, is important for understanding mass loss and feedback of massive star formation. HCN 3-2 and HCO$^+$ 3-2 are good tracers of dense outflowing molecular gas, which are closely related to active star formation. In this study, we present on-the-fly (OTF) mapping observations of HCN 3-2 and HCO$^+$ 3-2 toward a sample of 33 massive star-forming regions using the 10-m Submillimeter Telescope (SMT). With the spatial distribution of line wings of HCO$^+$ 3-2 and HCN 3-2, outflows are detected in 25 sources, resulting in a detection rate of 76$\%$. The optically thin H$^{13}$CN and H$^{13}$CO$^+$ 3-2 lines are used to identify line wings as outflows and estimate core mass. The mass $M_{out}$, momentum $P_{out}$, kinetic energy $E_{K}$, force $F_{out}$ and mass loss rate $\dot M_{out}$ of outflow and core mass, are obtained for each source. A sublinear tight correlation is found between the mass of dense molecular outflow and core mass, with an index of $\sim$ 0.8 and a correlation coefficient of 0.88.