ALMA Reveals A Collision Between Protostellar Outflows in BHR71

TL;DR

This study uses ALMA observations to provide the first clear evidence of collision between protostellar outflows in the BHR71 system, revealing complex interactions and 3D geometry.

Contribution

It presents the first resolved images showing colliding protostellar outflows, advancing understanding of outflow interactions in binary systems.

Findings

Detected increased CO brightness in the interaction zone

Observed velocity dispersion indicating flow collision

Revealed 3D geometry of the binary system

Abstract

For a binary protostellar outflow system in which its members are located so close to each other (the separation being smaller than the addition of the widths of the flows) and with large opening angles, the collision seems unavoidable regardless of the orientation of the outflows. This is in contrast to the current observational evidence of just a few regions with indications of colliding outflows. Here, using sensitive observations of the Atacama Large Millimeter/Submillimeter Array (ALMA), we report resolved images of carbon monoxide (CO) towards the binary flows associated with the BHR71 protostellar system. These images reveal for the first time solid evidence that their flows are partially colliding, increasing the brightness of the CO, the dispersion of the velocities in the interaction zone, and changing part of the orientation in one of the flows. Additionally, this impact opened the possibility of knowing the 3D geometry of the system, revealing that one of its components (IRS2) should be closer to us.