The ALMA-ATOMS-QUARKS survey: Resolving a chemically rich massive protostellar outflow

TL;DR

This study uses high-resolution ALMA data to analyze the physical and chemical structures of a massive protostellar outflow, revealing complex interactions between dynamics and chemistry driven by shocks, entrainment, and thermal processes.

Contribution

It provides a detailed chemical and physical characterization of a high-mass star forming outflow, highlighting the multi-origin processes shaping its molecular composition.

Findings

Identification of 35 molecular transitions from 22 species in the outflow.

Outflow chemistry is influenced by entrainment, shocks, and thermal desorption.

Outflows act as active chemical factories during high-mass star formation.

Abstract

We present a comprehensive study on the physical and chemical structures of a chemically rich bipolar outflow in a high-mass star forming region IRAS 16272$-$4837 (SDC335), utilizing high-resolution spectral line data at 1.3 mm and 3 mm dual-bands from the ALMA ATOMS and QUARKS surveys. The high-velocity jet is enveloped by a lower-velocity outflow cavity, containing bright knots that show enhanced molecular intensities and elevated excitation temperatures. Along the outflow, we have identified 35 transitions from 22 molecular species. By analyzing the spatial distribution and kinematics of these molecular lines, we find that the molecular inventory in the outflow is regulated by three processes: (i) direct entrainment from the natal molecular core by the outflow; (ii) shock-induced release of molecules or atoms from dust grains; and (iii) thermal desorption and gas-phase reactions driven by shock heating. These results confirm that outflows are not only dynamical structures but also active chemical factories, where entrainment, shocks, and thermal processing jointly enrich the molecular content. Our findings confirmed that outflow chemistry has multi-origin nature, and provide critical insights into chemical evolution during high-mass star formation.