Substructures in the Disk-Forming Region of the Class 0 Low-Mass Protostellar Source IRAS 16293-2422 Source A on a 10 au Scale

TL;DR

This study uses high-resolution ALMA observations to reveal substructures, temperature variations, and chemical characteristics in the disk-forming region of the Class 0 protostar IRAS 16293-2422 A, highlighting complex dynamics at 10 au scales.

Contribution

First detailed high-resolution imaging of substructures and temperature distribution within the disk-forming region of a Class 0 protostar.

Findings

Identification of 5 intensity peaks within 100 au of the protostar.

Detection of temperature rising to over 300 K at 50 au, indicating shock or heating effects.

Observation of chemical enhancement linked to temperature rise, characteristic of hot corinos.

Abstract

We have observed the Class 0 protostellar source IRAS 16293-2422 A in the C17O and H2CS lines as well as the 1.3 mm dust continuum with the Atacama Large Millimeter/submillimeter Array at an angular resolution of ~0."1 (14 au). The continuum emission of the binary component, Source A, reveals the substructure consisting of 5 intensity peaks within 100 au from the protostar. The C17O emission mainly traces the circummultiple structure on a 300 au scale centered at the intensity centroid of the continuum, while it is very weak within the radius of 50 au from the centroid. The H2CS emission, in contrast, traces the rotating disk structure around one of the continuum peaks (A1). Thus, it seems that the rotation centroid of the circummultiple structure is slightly different from that of the disk around A1. We derive the rotation temperature by using the multiple lines of H2CS. As approaching to the protostar A1, the rotation temperature steeply rises up to 300 K or higher at the radius of 50 au from the protostar. It is likely due to a local accretion shock and/or the preferential protostellar heating of the transition zone from the circummultiple structure to the disk around A1. This position corresponds to the place where the organic molecular lines are reported to be enhanced. Since the rise of the rotation temperature of H2CS most likely represents the rise of the gas and dust temperatures, it would be related to the chemical characteristics of this prototypical hot corino.