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The origin of outflows and their exact impact on disk evolution and planetformation remain crucial open questions. DG Tau B is a Class I protostarassociated with a rotating conical CO outflow and a structured disk. Hence itis an ideal target to study these questions. We aim to characterize themorphology and kinematics of the DG Tau B outflow in order to elucidate itsorigin and potential impact on the disk. Our analysis is based on Atacama LargeMillimeter Array (ALMA) 12CO(2-1) observations of DG Tau B at 20 au angularresolution. We characterize three different types of substructures in thisoutflow (arches, fingers, and cusps) with apparent acceleration. Wind-drivenshell models with a Hubble law fail to explain these substructures. Incontrast, both the morphology and kinematics of the conical flow can beexplained by a steady conical magnetohydrodynamic (MHD) disk wind withfoot-point radii r0= 0.7-3.4 au, a small magnetic level arm parameter lambda <1.6), and quasi periodic brightness enhancements. These might be caused by theimpact of jet bow shocks, source orbital motion caused by a 25 MJ companion at50 au, or disk density perturbations accreting through the wind launchingregion. The large CO wind mass flux (four times the accretion rate onto thecentral star) can also be explained if the MHD disk wind removes most of theangular momentum required for steady disk accretion. Our results provide thestrongest evidence so far for the presence of massive MHD disk winds in Class Isources with residual infall, and they suggest that the initial stages ofplanet formation take place in a highly dynamic environment.

Modeling the CO outflow in DG Tau B: Swept-up shells versus perturbed MHD disk wind