Ionized Gas Motions and the Structure of Feedback Near a Forming
  Globular Cluster in NGC 5253
  We observed Brackett $\alpha$ 4.05$\mu$m emission towards the supernebula in
NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe
feedback from its exciting embedded super star cluster (SSC). NIRSPEC's
Slit-Viewing Camera was simultaneously used to image the K-band continuum at
$\sim$$0.1''$ resolution. We register the IR continuum with HST imaging, and
find that the visible clusters are offset from the K-band peak, which coincides
with the Br $\alpha$ peak of the supernebula and its associated molecular
cloud. The spectra of the supernebula exhibit Br $\alpha$ emission with a
strong, narrow core. The linewidths are 65-76 km s$^{-1}$, FWHM, comparable to
those around individual ultra-compact HII regions within our Galaxy. A weak,
broad (FWHM$\simeq$150-175 km s$^{-1}$) component is detected on the base of
the line, which could trace a population of sources with high-velocity winds.
The core velocity of Br $\alpha$ emission shifts by +13 km s$^{-1}$ from NE to
SW across the supernebula, possibly indicating a bipolar outflow from an
embedded object, or linked to a foreground redshifted gas filament. The results
can be explained if the supernebula comprises thousands of ionized wind regions
around individual massive stars, stalled in their expansion due to critical
radiative cooling and unable to merge to drive a coherent cluster wind. Based
on the absence of an outflow with large mass loss, we conclude that feedback is
currently ineffective at dispersing gas, and the SSC retains enriched material
out of which it may continue to form stars.
