Revealing the Early Stages of Protostellar Outflows with JWST: Insights from Molecular Emission in L1448 and HH46

Protostellar outflows are among the most notable phenomena during the early phases of star formation. Despite progress in understanding their origins and properties, many questions remain unresolved, primarily due to the challenges in observing the innermost regions where these outflows arise. These areas are still deeply embedded in dense, dusty envelopes, making it necessary to study them at infrared wavelengths. The James Webb Space Telescope has transformed our ability to explore the early stages of jet and outflow formation and their interaction with the surrounding medium. With its high angular resolution and sensitivity across infrared wavelengths, JWST provides an unprecedented view into these hidden regions. We here present the results of a JWST investigation on the molecular outflows from L1448 and HH46, two extensively studied protostellar sources representing Class 0 and Class I stages. These outflows are here mapped for the first time in several H2 transitions in a wide range of excitation levels, thus probing with unprecedented details the flow thermal structure and excitation conditions. We derive key physical and kinematical parameters of the H2 flows, and compare these results with predictions of shock and outflow launching models. In particular, the marked layered structure in temperature and radial velocity displayed by the L1448 outflow support the origin in a MHD disk-wind. The analysis shows a marked difference in the excitation structure displayed by the two outflows, that we attribute to the combination of the different evolutionary stage and interaction of multiple flows due to the binary system in HH46.