Protostellar Outflows at the EarliesT Stages (POETS) VI. Evidence of disk-wind in G11.92-0.61 MM1

Abstract

Magnetohydrodynamic disk-winds play a key role in the formation of massive stars by providing the fine-tuning between accretion and ejection, where excess angular momentum is redirected away from the disk, allowing further mass growth. However, only a limited number of disk-wind sources have been detected to date. To better constrain the exact mechanism of this phenomenon, expanding the sample is critical. We performed an analysis of the disk-wind candidate G11.92-0.61 MM1 by estimating the physical parameters of the system and constraining the wind-launching mechanism. Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations were conducted in September 2021 with ALMA's longest baselines, which provided a synthesised beam of $\sim$30 mas. We obtained high-resolution images of the CH${}_3$CN ($v_8=1$ and $v=0$), CH${}_3$OH, SO${}_2$, and SO molecular lines, and the 1.3 mm continuum. Our molecular data allowed us to refine the parameters of the disk-outflow system in MM1. The rotating disk is resolved into two regions with distinct kinematics: the inner region ($<$300 au) is traced by high-velocity emission of high-excitation CH${}_3$CN lines and shows a Keplerian rotation; the outer region ($>$300 au), traced by mid-velocity CH${}_3$CN emission, rotates in a sub-Keplerian regime. The central source is estimated to be $\sim$20 $M_{\odot }$, which is about half the mass estimated in previous lower-resolution studies. A strong collimated outflow is traced by SO and SO${}_2$ emission up to $\sim$3400 au around MM1a. The SO and SO${}_2$ emissions show a rotation-dominated velocity pattern, a constant specific angular momentum, and a Keplerian profile that suggests a magneto-centrifugal disk-wind origin with launching radii of $\sim$50-100 au. G11.92-0.61 MM1 appears to be one of the clearest cases of molecular line-traced disk-winds detected around massive protostars.

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