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Disentangling the outflow and protostars in HH 900 in the Carina Nebula

HH 900 is a peculiar protostellar outflow emerging from a small, tadpole-shaped globule in the Carina nebula. Previous Hα imaging with HST/ACS showed an ionized outflow with a wide opening angle that is distinct from the highly collimated structures typically seen in protostellar jets. We present new narrowband near-IR [Fe II] images taken with the Wide Field Camera 3 on the Hubble Space Telescope that reveal a remarkably different structure than Hα. In contrast to the unusual broad Hα outflow, the [Fe II] emission traces a symmetric, collimated bipolar jet with the morphology and kinematics that are more typical of protostellar jets. In addition, new Gemini adaptive optics images reveal near-IR H$_2$ emission coincident with the Hα emission, but not the [Fe II]. Spectra of these three components trace three separate and distinct velocity components: (1) H$_2$ from the slow, entrained molecular gas, (2) Hα from the ionized skin of the accelerating outflow sheath, and (3) [Fe II] from the fast, dense, and collimated protostellar jet itself. Together, these data require a driving source inside the dark globule that remains undetected behind a large column density of material. In contrast, Hα and H$_2$ emission trace the broad outflow of material entrained by the jet, which is irradiated outside the globule. As it get dissociated and ionized, it remains visible for only a short time after it is dragged into the H II region.