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

Travis J. Thieme,Ka Ho Lam,Zhi-Yun Li,Pou-Ieng Cheong,Sheng-Jun Lin,Shih-Ping Lai,Chin-Fei Lee,Bo Zhao,Hsi-Wei Yen

doi:10.3847/1538-4357/ac382b

Abstract

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 C18O 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 substructures in position–position–velocity space. Four out of the five substructures fit well (>95%) with our simple infall model, with specific angular momenta between 2.7–6.9 × 10−4 km s−1 pc and mass-infall rates of 0.5–1.1 × 10−6 M ⊙ yr−1. Better characterization of the physical structure in the supposed “outflow cavities” is important to disentangle the true outflow cavities and accretion flows.

Highlights

Supported disks around the youngest protostars are essential for transporting the angular momentum of infalling material from the envelope to the protostar and for the development of proto-planetary systems
This leads to questions such as whether the material in the outflow cavity has a similar velocity structure with the outflow, whether material can be recycled from the outflow and accrete back onto the disk, or if large-scale material can fall along the outflow cavities
We uncover the dynamics of several accretion flows using the CMU model and demonstrate a case where accretion flows are hiding in the so-called “outflow cavity”

Summary

Introduction

Supported disks around the youngest protostars are essential for transporting the angular momentum of infalling material from the envelope to the protostar and for the development of proto-planetary systems. Observations of molecular lines trace the Keplerian rotation of these disks around Class 0 protostars and confirm that disks form in the earliest stages of star formation when the protostar is still deeply embedded in its parent core (e.g., Tobin et al 2012b; Murillo et al 2013; Ohashi et al 2014; Lee et al 2014; Codella et al 2014; Aso et al 2017; Yen et al 2017a). In order to better understand the formation and growth of these young disks, it is important to study how material accretes onto the disk from the surrounding envelope

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Conclusion