Disks and outflows in the S255IR area of high mass star formation from ALMA observations

TL;DR

This paper uses ALMA observations to analyze the structure of the S255IR high mass star forming region, revealing the different roles of clumps SMA1 and SMA2 in outflow activity and challenging previous assumptions about their driving sources.

Contribution

It provides new insights into the physical relation of clumps and the origin of outflows, identifying SMA2 as the likely driver of the main outflow, contrary to earlier beliefs.

Findings

SMA2 drives the main high velocity bipolar outflow.

SMA1 hosts a young star but does not drive the main outflow.

No outflow detected from SMA3 (NIRS1).

Abstract

We describe the general structure of the well known S255IR high mass star forming region, as revealed by our recent ALMA observations. The data indicate a physical relation of the major clumps SMA1 and SMA2. The driving source of the extended high velocity well collimated bipolar outflow is not the most pronounced disk-like SMA1 clump harboring a 20 M$_\odot$ young star (S255 NIRS3), as it was assumed earlier. Apparently it is the less evolved SMA2 clump, which drives the outflow and contains a compact rotating structure (probably a disk). At the same time the SMA1 clump drives another outflow, with a larger opening angle. The molecular line data do not show an outflow from the SMA3 clump (NIRS1), which was suggested by IR studies of this region.