Protostellar Outflows at the EarliesT Stages (POETS). III. H2O masers
  tracing disk-winds and jets near luminous YSOs
  The goal of the Protostellar Outflows at the EarliesT Stages (POETS) survey
is to image the disk-outflow interface on scales of 10-100 au in a
statistically significant sample (36) of luminous young stellar objects (YSO),
targeting both the molecular and ionized components of the outflows. The
outflow kinematics is studied at milliarcsecond scales through VLBI
observations of the 22 GHz water masers. We employed the JVLA at 6, 13, and 22
GHz in the A- and B-Array configurations to determine the spatial structure and
the spectral index of the radio continuum emission. In about half of the
targets, the water masers observed at separation <= 1000 au from the YSOs trace
either or both of these kinematic structures: 1) a spatially elongated
distribution oriented at close angle with the direction of collimation of the
maser proper motions (PM), and 2) a linear LSR velocity (Vlsr) gradient across
the YSO position. The kinematic structure (1) is readily interpreted in terms
of a protostellar jet, as confirmed in some targets via the comparison with
independent observations of the YSO jets, in thermal (continuum and line)
emissions, reported in the literature. The kinematic structure (2) is
interpreted in terms of a disk-wind (DW) seen almost edge-on on the basis of
several pieces of evidence: first, it is invariably directed perpendicular to
the YSO jet; second, it agrees in orientation and polarity with the Vlsr
gradient in thermal emissions (when reported in the literature) identifying the
YSO disk at scales of <= 1000~au; third, the PMs of the masers delineating the
Vlsr gradients hint at flow motions at a speed of 10-20 km/s directed at large
angles with the disk midplane. In the remaining targets, the maser PMs are not
collimated but rather tend to align along two almost perpendicular directions,
and could originate in DW-jet systems slightly inclined (<= 30 deg) with
respect to edge-on.
