The ionized warped disk and disk wind of the massive protostar Monoceros
  R2-IRS2 seen with ALMA
  Theories of massive star formation predict that massive protostars accrete
gas through circumstellar disks. Although several cases have been found already
thanks to high-angular resolution interferometry, it remains unknown the
internal physical structure of these disks and, in particular, whether they
present warps or internal holes as observed in low-mass proto-planetary disks.
Here, we report very high angular resolution observations of the H21alpha radio
recombination line carried out in Band 9 with the Atacama Large
Millimeter/submillimeter Array (beam of 80 mas x 60 mas, or 70 au x 50 au)
toward the IRS2 massive young stellar object in the Monoceros R2 star-forming
cluster. The H21alpha line shows maser amplification, which allows us to study
the kinematics and physical structure of the ionised gas around the massive
protostar down to spatial scales of ~1-2 au. Our ALMA images and 3D radiative
transfer modelling reveal that the ionized gas around IRS2 is distributed in a
Keplerian circumstellar disk and an expanding wind. The H21alpha emission
centroids at velocities between -10 and 20 km s-1 deviate from the disk plane,
suggesting a warping for the disk. This could be explained by the presence of a
secondary object (a stellar companion or a massive planet) within the system.
The ionized wind seems to be launched from the disk surface at distances ~11 au
from the central star, consistent with magnetically-regulated disk wind models.
This suggests a similar wind launching mechanism to that recently found for
evolved massive stars such as MWC349A and MWC922.
