A Face-on Accretion System in High-Mass Star-Formation: Possible Dusty Infall Streams within 100 AU

Abstract

We report on interferometric observations of a face-on accretion system around the High-Mass young stellar object, G353.273+0.641. The innermost accretion system of 100 au radius was resolved in a 45 GHz continuum image taken with the Jansky-Very Large Array. Our spectral energy distribution analysis indicated that the continuum could be explained by optically thick dust emission. The total mass of the dusty system is $\sim$ 0.2 $M_{\sun}$ at minimum and up to a few $M_{\sun}$ depending on the dust parameters. 6.7 GHz CH${}_3$OH masers associated with the same system were also observed with the Australia Telescope Compact Array. The masers showed a spiral-like, non-axisymmetric distribution with a systematic velocity gradient. The line-of-sight velocity field is explained by an infall motion along a parabolic streamline that falls onto the equatorial plane of the face-on system. The streamline is quasi-radial and reaches the equatorial plane at a radius of 16 au. This is clearly smaller than that of typical accretion disks in High-Mass star formation, indicating that the initial angular momentum was very small, or the CH${}_3$OH masers selectively trace accreting material that has small angular momentum. In the former case, the initial specific angular momentum is estimated to be 8 $\times$ 10${}^{20}$ ($M_{\ast }$$/$10 $M_{\sun}$)${}^{0.5}$ cm${}^2$ s${}^{-1}$, or a significant fraction of the initial angular momentum was removed outside of 100 au. The physical origin of such a streamline is still an open question and will be constrained by the higher-resolution ($\sim$ 10 mas) thermal continuum and line observations with ALMA long baselines.

17 pages, 11 figures

References in corpus (16)

• Magnetic Fields in the Formation of Sun-Like Stars
• A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
• Signs of Early-Stage Disk Growth Revealed with ALMA
• A hot compact dust disk around a massive young stellar object
• Disk-Driven Rotating Bipolar Outflow in Orion Source I
• ALMA Observations of Infalling Flows toward the Keplerian Disk around the Class I Protostar L1489 IRS
• Direct Imaging of Bridged Twin Protoplanetary Disks in a Young Multiple Star
• Protostellar Jets Enclosed by Low-velocity Outflows
• A multiple system of high-mass YSOs surrounded by disks in NGC7538 IRS1
• ALMA Observations of Orion Source I at 350 and 660 GHz
• The Circumstellar Structure and Excitation Effects around the Massive Protostar Cepheus A HW 2
• Circumbinary Ring, Circumstellar disks and accretion in the binary system UY Aurigae
• Accelerating a water maser face-on jet from a high mass young stellar object
• ALMA band 8 continuum emission from Orion Source I
• Highly variable young massive stars in ATLASGAL clumps
• Position-Velocity Diagrams for the Maser Emission coming from a Keplerian Ring

Cited by in corpus (8)

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• Mid-Infrared and Maser Flux Variability Correlation in Massive Young Stellar Object G036.70+00.09
• A kinematic study of the disc-outflow system around a high-mass protostar G59.783+0.065 probed by methanol and water masers
• Periodic 6.7 GHz $\mathrm{C}{\mathrm{H}}_3\mathrm{OH}$ maser emission in G353.273+0.641: First candidate for a pulsating high-mass protostar