Collective outflow from a small multiple stellar system

TL;DR

This study uses 3D simulations to explore how multiple forming massive stars can produce a collective outflow, resembling observed high-mass star outflows, and assesses the accuracy of observational methods in deriving physical parameters.

Contribution

It introduces a simulation model that demonstrates collective outflow formation from multiple massive stars and evaluates the reliability of observational techniques.

Findings

Stars in a common accretion flow tend to have aligned outflows.

Simulated collective outflows resemble observed structures like Cepheus A and DR 21.

Standard observational methods recover actual physical quantities within a factor of 2-3.

Abstract

The formation of high-mass stars is usually accompanied by powerful protostellar outflows. Such high-mass outflows are not simply scaled-up versions of their lower-mass counterparts, since observations suggest that the collimation degree degrades with stellar mass. Theoretically, the origins of massive outflows remain open to question because radiative feedback and fragmentation of the accretion flow around the most massive stars, with M > 15 M_Sun, may impede the driving of magnetic disk winds. We here present a three-dimensional simulation of the early stages of core fragmentation and massive star formation that includes a subgrid-scale model for protostellar outflows. We find that stars that form in a common accretion flow tend to have aligned outflow axes, so that the individual jets of multiple stars can combine to form a collective outflow. We compare our simulation to observations with synthetic H_2 and CO observations and find that the morphology and kinematics of such a collective outflow resembles some observed massive outflows, such as Cepheus A and DR 21. We finally compare physical quantities derived from simulated observations of our models to the actual values in the models to examine the reliability of standard methods for deriving physical quantities, demonstrating that those methods indeed recover the actual values to within a factor of 2-3.