Outflow activities in the young high-mass stellar object G23.44-0.18

TL;DR

This study observes outflow activities in the high-mass star-forming region G23.44-0.18, revealing a bipolar outflow with complex structure, shock chemistry, and differences in molecular abundances between cores, providing insights into high-mass star formation processes.

Contribution

First detailed observational analysis of outflow morphology and chemistry in G23.44-0.18, highlighting shock effects and molecular abundance variations in high-mass star formation.

Findings

Bipolar outflow from MM2 with wide-angle and collimated components

Molecular abundances higher in MM2 than MM1 by 3-4 times

Shock signatures detected in SO, OCS, CH3OH, and HNCO

Abstract

We present an observational study towards the young high-mass star forming region G23.44-0.18 using the Submillimeter Array. Two massive, radio-quiet dusty cores MM1 and MM2 are observed in 1.3 mm continuum emission and dense molecular gas tracers including thermal CH$_3$OH, CH$_3$CN, HNCO, SO, and OCS lines. The $^{12}$CO (2--1) line reveals a strong bipolar outflow originated from MM2. The outflow consists of a low-velocity component with wide-angle quasi-parabolic shape and a more compact and collimated high-velocity component. The overall geometry resembles the outflow system observed in the low-mass protostar which has a jet-driven fast flow and entrained gas shell. The outflow has a dynamical age of $6\times10^3$ years and a mass ejection rate $\sim10^{-3} M_{\odot}$ year$^{-1}$. A prominent shock emission in the outflow is observed in SO and OCS, and also detected in CH$_3$OH and HNCO. We investigated the chemistry of MM1, MM2 and the shocked region. The dense core MM2 have molecular abundances of 3 to 4 times higher than those in MM1. The abundance excess, we suggest, can be a net effect of the stellar evolution and embedded shocks in MM2 that calls for further inspection.