Early Planet Formation in Embedded Disks (eDisk). XIX. Structures of molecular outflows

TL;DR

This study classifies and analyzes molecular outflows in 19 low-mass protostars using ALMA observations, revealing diverse structures, misalignments, and signs of outflow variability.

Contribution

It provides a detailed morphological and kinematical classification of outflows, including models for shell structures and evidence of time variability in protostellar outflows.

Findings

15 out of 19 sources show molecular outflows.

Outflows are classified into three types: wind-driven shell, bow shock, slow disk wind.

Evidence of outflow variability and ambient medium differences was found.

Abstract

As part of the ALMA Large Program "Early Planet Formation in Embedded Disks" (eDisk), 12CO (2 - 1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blue-shifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blue-shifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blue-shifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts.