YSO jets in the Galactic Plane from UWISH2: V - Jets and Outflows in M17
  Jets and outflows are the first signposts of stellar birth. Emission in the
H2 1-0S(1) line at 2.122 micron is a powerful tracer of shock excitation in
these objects. Here we present the analysis of 2.0 x 0.8 square degrees data
from the UK Widefield Infrared Survey for H2 (UWISH2) in the 1-0S(1) line to
identify and characterize the outflows of the M17 complex. We uncover 48
probable outflows, of which, 93 per cent are new discoveries. We identified
driving source candidates for 60 per cent of the outflows. Among the driving
source candidate YSOs: 90 per cent are protostars and the reminder 10 per cent
are Class II YSOs. Comparing with results from other surveys, we suggest that
H2 emission fades very quickly as the objects evolve from protostars to
pre-main-sequence stars. We fit SED models to 14 candidate outflow driving
sources and conclude that the outflows of our sample are mostly driven by
moderate-mass YSOs that are still actively accreting from their protoplanetary
disc. We examined the spatial distribution of the outflows with the gas and
dust distribution of the complex, and observed that the filamentary dark-cloud
"M17SWex" located at the south-western side of the complex, is associated with
a greater number of outflows. We find our results corroborate previous
suggestions, that in the M17 complex, M17SWex is the most active site of star
formation. Several of our newly identified outflow candidates are excellent
targets for follow up studies to better understand very early phase of
protostellar evolution.
