The First Bird’s-eye View of a Gravitationally Unstable Accretion Disk in High-mass Star Formation

Abstract

We report on the first bird's-eye view of the innermost accretion disk around the high-mass protostellar object G353.273+0.641, taken by Atacama Large Millimter/submillimeter Array long-baselines. The disk traced by dust continuum emission has a radius of 250 au, surrounded by the infalling rotating envelope traced by thermal CH 3 OH lines. This disk radius is consistent with the centrifugal radius estimated from the specific angular momentum in the envelope. The lower-limit envelope mass is ∼5-7 M ⊙ and accretion rate onto the stellar surface is 3 × 10 −3 M ⊙ yr −1 or higher. The expected stellar age is well younger than 10 4 yr, indicating that the host object is one of the youngest high-mass objects at present. The disk mass is 2-7 M ⊙ , depending on the dust opacity index. The estimated Toomre's Q parameter is typically 1-2 and can reach 0.4 at the minimum. These Q values clearly satisfy the classical criteria for the gravitational instability, and are consistent with the recent numerical studies. Observed asymmetric and clumpy structures could trace a spiral arm and/or disk fragmentation. We found that 70% of the angular momentum in the accretion flow could be removed via the gravitational torque in the disk. Our study has indicated that the dynamical nature of a self-gravitating disk could dominate the early phase of high-mass star formation. This is remarkably consistent with the early evolutionary scenario of a low-mass protostar.

Discs and outflows in the early phases of massive star formation: Influence of magnetic fields and ambipolar diffusion

“…They did not report the presence of a large (R > 1000 au) disc. Additional, spatially resolved compact discs have also been reported in recent literature (Fernández-López et al 2016;Motogi et al 2019). Multi-dimensional numerical simulations have also investigated disc formation and evolution in massive dense core collapse, either in the hydrodynamical case (e.g.…”

“…More recently, Motogi et al (2019) reported ALMA observation of a young high-mass protostellar object (10 M , no ultra-compact HII region), accreting at about 10 −3 M yr −1 , of which the characteristics are very consistent with the early evolutionary scenario of a low-mass protostar. From dust continuum emission, they report a disc mass of 2−7 M and a disc size of 250 au, which is associated with a lower limit of 0.4 for the Toomre parameter.…”

H II regions and high-mass starless clump candidates

“…This publication is based on the SEDIGISM and PPMAP data. models for HMSF have been discussed widely: (1) monolithic collapse (McKee & Tan 2003;Krumholz et al 2009;Csengeri et al 2018;Sanna et al 2019;Motogi et al 2019) and (2) competitive accretion Cyganowski et al 2017;Fontani et al 2018). It is possible that these models are not strongly and mutually incompatible as described by many current studies; these two models of HMSF are expected to be merged into a unified and consistent star formation model with the progress of observations and theories (Schilke 2015).…”

Mirror, mirror on the outflow cavity wall

“…In the sub-millimetre, millimetre, and radio regimes, we can analyse the molecules forming further away in the disc Based on observations collected at the European Southern Observatory Paranal, Chile, Programme ID 0101.C-0317(A) and 098.C-0636(A). and dust continuum (Cesaroni et al 2005(Cesaroni et al , 2006(Cesaroni et al , 2007Motogi et al 2019). However, if we want to probe the inner gaseous disc within a few astronomical units from the central source, namely where accretion and ejection take place, we need to observe in the near-infrared (NIR).…”