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

¹ INAF – Osservatorio Astrofísico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
² INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy

^★ Corresponding author; olga.bayandina@inaf.it

Received: 1 November 2024
Accepted: 22 December 2024

Abstract

Context. Magnetohydrodynamic disk-winds are thought to 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 of a young protostar. 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.

Aims. We performed a detailed analysis of the disk-wind candidate G11.92-0.61 MM1 by estimating the physical parameters of the massive protostellar system and constraining the wind-launching mechanism.

Methods. Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations of G11.92-0.61 MM1 were conducted in September 2021 with ALMA’s longest baselines, which provided a synthesised beam of ~30 mas. We obtained high-resolution images of the CH₃CN (υ₈=1 and υ=0), CH₃OH, SO₂, and SO molecular lines, as well as the 1.3 mm continuum.

Results. Our high-resolution 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 CH₃CN lines and shows a Keplerian rotation; the outer region (>300 au), traced by mid-velocity CH₃CN emission, rotates in a sub-Keplerian regime. The central source is estimated to be ~20 M_⊙, which is about half the mass estimated in previous lower-resolution studies. A strong collimated outflow is traced by SO and SO₂ emission up to ~3400 au around MM1a. The SO and SO₂ 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 ~50–100 au.

Conclusions. G11.92-0.61 MM1 appears to be one of the clearest cases of molecular line-traced disk-winds detected around massive protostars.