Jets and outflows are ubiquitous in accreting young stars of all ages, with universal collimation and connection between accretion and ejection. A fundamental issue yet to be resolved is the launching point of the jet. Clarifying the jet launching region is crucial to understand its role in solving the excess angular momentum problem and its dynamical and chemical feedback on disk and planet formation. However, observing the launching region is extremely challenging due to the high extinction and the size of the emitting region.
Studying the chemical content of jets presents a powerful tool to study the launching zone ?molecules found in the jet are a product of the initial composition and processing of the launched material. Following a puzzling discovery of H2CO in the Ser-emb-8N protostellar jet, we targeted this source with high angular resolution (~0.2”) and high sensitivity ALMA Band 6 observations to detect multiple transitions of methanol (CH3OH) and formaldehyde (H2CO).
These observations reveal the presence of methanol in the high-velocity protostellar jet, spatially resolved for the first time. We find that the excitation temperature decreases as a function of distance from the launching source and we find an anti-correlation between SiO and CH3OH line intensity, revealing that those jets are subject to time-sensitive chemistry at the scales of <100 years. We suggest that the methanol emission detected in the high velocity knots is a result of sputtering of dust grains launched within the jet while still covered by icy mantles. This suggests that the jet launching zone extends beyond the dust sublimation radius, or that a significant amount of grains has been carried away from the disk atmosphere. Overall, studies of the chemical composition of jets prove to be a powerful tool to investigate the innermost regions of the disk which remain difficult to resolve.