Evolution of Protostellar Outflow around Low-mass Protostar

TL;DR

This study uses advanced simulations to explore how protostellar outflows evolve from early to later stages, revealing their impact on star formation efficiency and outflow characteristics consistent with observations.

Contribution

It provides a comprehensive simulation-based analysis of protostellar outflow evolution across different stages, linking outflow properties with star formation processes.

Findings

Outflows are driven by the first core before protostar formation.

Large outflow opening angles in the Class 0 stage reduce star formation efficiency.

Outflow properties match observed correlations and evolve from Class 0 to I.

Abstract

The evolution of protostellar outflow is investigated with resistive magneto-hydrodynamic nested-grid simulations that cover a wide range of spatial scales (\sim 1AU - 1pc). We follow cloud evolution from the pre-stellar core stage until the infalling envelope dissipates long after the protostar formation. We also calculate protostellar evolution to derive protostellar luminosity with time-dependent mass accretion through a circumstellar disk. The protostellar outflow is driven by the first core prior to protostar formation and is directly driven by the circumstellar disk after protostar formation. The opening angle of the outflow is large in the Class 0 stage. A large fraction of the cloud mass is ejected in this stage, which reduces the star formation efficiency to \sim 50%. After the outflow breaks out from the natal cloud, the outflow collimation is gradually improved in the Class I stage. The head of the outflow travels more than \sim 10^5AU in \sim 10^5 yr. The outflow momentum, energy and mass derived in our calculations agree well with observations. In addition, our simulations show the same correlations among outflow momentum flux, protostellar luminosity and envelope mass as those in observations. These correlations differ between Class 0 and I stages, which is explained by different evolutionary stages of the outflow; in the Class 0 stage, the outflow is powered by the accreting mass and acquires its momentum from the infalling envelope; in the Class I stage, the outflow enters the momentum-driven snow-plough phase. Our results suggest that protostellar outflow should determine the final stellar mass and significantly affect the early evolution of low-mass protostars.