Accretion Flows or Outflow Cavities? Uncovering the Gas Dynamics around Lupus 3-MMS

TL;DR

This study uses ALMA data to identify and characterize extended accretion flow structures around Lupus 3-MMS, challenging the idea that these are part of outflow cavities and providing new insights into early protostellar accretion.

Contribution

It uncovers and analyzes extended accretion flow-like structures in a young protostar, demonstrating they are consistent with infall rather than outflow cavities, using position-velocity analysis and modeling.

Findings

Four accretion-like structures follow outflow edges.

Most structures fit a simple infall model with high confidence.

Derived angular momenta and mass-infall rates for the structures.

Abstract

Understanding how material accretes onto the rotationally supported disk from the surrounding envelope of gas and dust in the youngest protostellar systems is important for describing how disks are formed. Magnetohydrodynamic simulations of magnetized, turbulent disk formation usually show spiral-like streams of material (accretion flows) connecting the envelope to the disk. However, accretion flows in these early stages of protostellar formation still remain poorly characterized due to their low intensity and possibly some extended structures are disregarded as being part of the outflow cavity. We use ALMA archival data of a young Class 0 protostar, Lupus 3-MMS, to uncover four extended accretion flow-like structures in C$^{18}$O that follow the edges of the outflows. We make various types of position-velocity cuts to compare with the outflows and find the extended structures are not consistent with the outflow emission, but rather more consistent with a simple infall model. We then use a dendrogram algorithm to isolate five sub-structures in position-position-velocity space. Four out of the five sub-structures fit well ($>$95%) with our simple infall model, with specific angular momenta between $2.7-6.9\times10^{-4}\,$km$\,$s$^{-1}\,$pc and mass-infall rates of $0.5-1.1\times10^{-6}\,M_{\odot}\,$yr$^{-1}$. Better characterization of the physical structure in the supposed "outflow-cavities" is important to disentangle the true outflow cavities and accretion flows.