Accretion and Outflow in Orion-KL Source I

TL;DR

This study uses high-resolution ALMA observations to analyze the molecular outflow and disk structure of Orion Source I, revealing turbulent boundary layers, the impact of SrcI's proper motion, and shock-induced NaCl excitation.

Contribution

It provides detailed imaging of SrcI's outflow and disk at AU scales, highlighting the role of SrcI's motion and turbulence in outflow dynamics and molecular excitation.

Findings

Turbulent boundary layer in SrcI's outflow dissipates angular momentum.

SrcI's proper motion influences outflow structure and evolution.

Shocks near the disk surface excite NaCl molecules.

Abstract

We present ALMA observations of SiO, SiS, H$_2$O , NaCl, and SO line emission at ~30 to 50 mas resolution. These images map the molecular outflow and disk of Orion Source I (SrcI) on ~12 to 20 AU scales. Our observations show that the flow of material around SrcI creates a turbulent boundary layer in the outflow from SrcI which may dissipate angular momentum in the rotating molecular outflow into the surrounding medium. Additionally, the data suggests that the proper motion of SrcI may have a significant effect on the structure and evolution of SrcI and its molecular outflow. As the motion of SrcI funnels material between the disk and the outflow, some material may be entrained into the outflow and accrete onto the disk, creating shocks which excite the NaCl close to the disk surface.