Observations of Orion Source I Disk and Outflow Interface

TL;DR

This study uses high-resolution imaging to analyze the structure, chemistry, and dynamics of the disk and outflow around Orion Source I, revealing detailed molecular distributions and their interactions.

Contribution

It provides the first detailed imaging of the disk and outflow interface at multiple frequencies, highlighting the chemical processes and velocity field within the high-mass protostar environment.

Findings

Salt emission traces disk velocity field.

Molecules originate mainly in the bipolar outflow.

Disk shows optically thick midplane and optically thin edges.

Abstract

We imaged the continuum and molecular line emission from Orion Source I (SrcI) with up to 30 mas (12 AU) resolution at 43, 99, 223, and 340 GHz in an attempt to probe the structure and chemistry of the circumstellar disk and bipolar outflow associated with this high mass protostar. The continuum spectral index ranges from $\sim$2 along the midplane of the disk to $\sim$3 along the edges, consistent with dust that is optically thick in the midplane but becomes optically thin at the periphery. Salt (NaCl) emission is visible where the dust is optically thin; it provides a unique tracer of the velocity field within the disk. All other molecules that we have mapped - H$_2$O, AlO, SiO, SiS, SO, and SO$_2$ - appear to originate primarily in the bipolar outflow. The base of the outflow is corotating with the disk. SiS shows a filamentary structure that is most prominent along the edges of the outflow. The molecular distributions suggest that Si and Al released from dust grains in the disk react with oxygen derived from H$_2$O to form SiO and AlO, and with SO and SO$_2$ to form SiS.