Planck's dusty GEMS. V. Molecular wind and clump stability in a strongly
  lensed star-forming galaxy at z=2.2
  We report the discovery of a molecular wind signature from a massive
intensely star-forming clump of a few $10^9$ Msun, in the strongly
gravitationally lensed submillimeter galaxy "the Emerald" (PLCK_G165.7+49.0) at
z=2.236. The Emerald is amongst the brightest high-redshift galaxies on the
submillimeter sky, and was initially discovered with the Planck satellite. The
system contains two magnificient structures with projected lengths of 28.5" and
21" formed by multiple, near-infrared arcs, falling behind a massive galaxy
cluster at z=0.35, as well as an adjacent filament that has so far escaped
discovery in other wavebands. We used HST/WFC3 and CFHT optical and
near-infrared imaging together with IRAM and SMA interferometry of the CO(4-3)
line and 850 $\mu$m dust emission to characterize the foreground lensing mass
distribution, construct a lens model with Lenstool, and calculate gravitational
magnification factors between 20 and 50 in most of the source. The majority of
the star formation takes place within two massive star-forming clumps which are
marginally gravitationally bound and embedded in a $9 \times 10^{10}$ Msun,
fragmented disk with 20% gas fraction. One of the clumps shows a pronounced
blue wing in the CO(4-3) line profile, which we interpret as a wind signature.
The mass outflow rates are high enough for us to suspect that the clump might
become unbound within a few tens of Myr, unless the outflowing gas can be
replenished by gas accretion from the surrounding disk. The velocity offset of
-200 km s$^{-1}$ is above the escape velocity of the clump, but not that of the
galaxy overall, suggesting that much of this material might ultimately rain
back onto the galaxy and contribute to fueling subsequent star formation.
