The ALMA image of the ringed proto planetary disk around HL Tau stands out as the iconic symbol of star and planet formation. HL Tau, however, possesses also powerful outflows, in the form of a collimated atomic jet surrounded by a wide angle H2 wind and by a conical molecular outflow revealed in CO lines. During a recent investigation conducted with ALMA at 0.”25 resolution in the ALMA-DOT project, we found that the molecular outflow shows peculiar features in the velocity channel maps, consisting in a series of arc-shaped structures whose position and size change continuously with radial velocity. From an analysis of such features we derived that the flow is arranged in nested, detached flow surfaces with decreasing velocity toward the outer layers. This distribution supports a scenario in which the outflow is the outermost portion of an extended magnetized disk wind. Under this hypothesis we derive that the launch radii on the disk of the flow surfaces are located between 4 and 20 au, with the outermost two layers launched from the regions immediately adjacent to the first gap. These results appear to support recent non-ideal MHD models according to which magnetic instabilities in the disk produce the ringed structure (alternatively to the action of yet elusive proto planets) and an inhomogeneous MHD wind, with denser layers arising from the rings. In such a scenario the outflow would be responsible for the removal of a large fraction of angular momentum also from the outer 10-20 au region of the disk where the effective turbulent viscosity is suppressed. Such outflows prove therefore to be a crucial element for the determination the initial conditions of the planet formation process.
[Poster PDF File]