Illuminating the Tadpole's metamorphosis I: MUSE observations of a small
  globule in a sea of ionizing photons
  We present new MUSE/VLT observations of a small globule in the Carina H II
region that hosts the HH 900 jet+outflow system. Data were obtained with the
GALACSI ground-layer adaptive optics system in wide-field mode, providing
spatially-resolved maps of diagnostic emission lines. These allow us to measure
the variation of the physical properties in the globule and jet+outflow system.
We find high temperatures ($T_e \approx 10^4$ K), modest extinction ($A_V
\approx 2.5$ mag), and modest electron densities ($n_e \approx 200$ cm$^{-3}$)
in the ionized gas. Higher excitation lines trace the ionized outflow; both the
excitation and ionization in the outflow increase with distance from the opaque
globule. In contrast, lower excitation lines that are collisionally de-excited
at densities $\gtrsim 10^4$ cm$^{-3}$ trace the highly collimated protostellar
jet. Assuming the globule is an isothermal sphere confined by the pressure of
the ionization front, we compute a Bonnor-Ebert mass of $\sim 3.7$ M$_{\odot}$.
This is two orders of magnitude higher than previous mass estimates, calling
into question whether small globules like the Tadpole contribute to the bottom
of the IMF. Derived globule properties are consistent with a cloud that has
been and/or will be compressed by the ionization front on its surface. At the
estimated globule photoevaporation rate of $\sim 5 \times 10^{-7}$ M$_{\odot}$
yr$^{-1}$, the globule will be completely ablated in $\sim 7$ Myr. Stars that
form in globules like the Tadpole will emerge into the H II later and may help
resolve some of the temporal tension between disk survival and enrichment.
