JWST study of the DG Tau B disk wind candidate: I – Overview and Nested H_2/CO outflows

The origin and impact of outflows on proto-planetary disks and planet formation are key open questions. DG Tau B, a Class I protostar with a structured disk and a striking rotating conical CO outflow, recently identified with ALMA as one of the best MHD disk wind candidate, is an ideal target for studying these phenomena. Our aim is to analyse the outflow components intermediate between the fast axial jet and the wider molecular CO outflow to discriminate between the different scenarios at their origin (irradiated/shocked disk wind or swept-up material). Using observations from JWST NIRSpec-IFU, NIRCam and SINFONI/VLT, we investigate the morphology, kinematics and excitation conditions of H_2 emission lines of the red-shifted outflow lobe. We find an onion-like structure of the outflows with increasing temperature, velocity and collimation towards the flow axis. The red-shifted H_2 emission reveals a narrow conical cavity nested inside the CO outflow and originating from the inner disk regions (< 6 au). The H_2 shell exhibits a constant vertical velocity (≃22 km/s), twice faster that of the CO flow and an average mass flux of Ṁ(H_2) = 3e-11 M_⊙/yr significantly lower than the jet and CO values, suggesting low H_2 abundance. The global layered structure of the H_2/CO outflows is consistent with an MHD disk wind scenario, with the hot H_2 possibly tracing an inner dense photodissociation layer of the wind coming from a launching radius in the disk of 0.2-0.4 au. Further analysis, including MIRI observations will provide additional insights into the H_2 excitation mechanisms and the origin of the layered outflows observed in DG Tau B.