Illuminating a tadpole's metamorphosis II: observing the on-going
  transformation with ALMA
  We present new Atacama Large Millimeter/submillimeter Array (ALMA)
observations of the tadpole, a small globule in the Carina Nebula that hosts
the HH 900 jet+outflow system. Our data include $^{12}$CO, $^{13}$CO, C$^{18}$O
J=2-1, $^{13}$CO, C$^{18}$O J=3-2, and serendipitous detections of DCN J=3-2
and CS J=7-6. With angular resolution comparable to the Hubble Space Telescope
(HST), our data reveal for the first time the bipolar molecular outflow in CO,
seen only inside the globule, that is launched from the previously unseen
jet-driving protostar (the HH 900 YSO). The biconical morphology joins smoothly
with the externally irradiated outflow seen in ionized gas tracers outside the
globule, tracing the overall morphology of a jet-driven molecular outflow.
Continuum emission at the location of the HH 900 YSO appears to be slightly
flattened perpendicular to outflow axis. Model fits to the continuum have a
best-fit spectral index of $\sim 2$, suggesting cold dust and the onset of
grain growth. In position-velocity space, $^{13}$CO and C$^{18}$O gas
kinematics trace a C-shaped morphology, similar to infall profiles seen in
other sources, although the global dynamical behaviour of the gas remains
unclear. Line profiles of the CO isotopologues display features consistent with
externally heated gas. We estimate a globule mass of $\sim 1.9$ M$_{\odot}$,
indicating a remaining lifetime of $\sim 4$ Myr, assuming a constant
photoevaporation rate. This long globule lifetime will shield the disk from
external irradiation perhaps prolonging its life and enabling planet formation
in regions where disks are typically rapidly destroyed.
