The dynamically young outflow of the Class 0 protostar Cha-MMS1
  On the basis of its low luminosity, its chemical composition, and the absence
of a large-scale outflow, the dense core Cha-MMS1 located in the Chamaeleon I
molecular cloud was proposed as a first hydrostatic core (FHSC) candidate a
decade ago. Our goal is to test this hypothesis by searching for a slow,
compact outflow driven by Cha-MMS1 that would match the predictions of MHD
simulations for this short phase of star formation. We use the Atacama Large
Millimetre/submillimetre Array (ALMA) to map Cha-MMS1 at high angular
resolution in CO 3-2 and 13CO 3-2 as well as in continuum emission. We report
the detection of a bipolar outflow emanating from the central core, along a
(projected) direction roughly parallel to the filament in which Cha-MMS1 is
embedded and perpendicular to the large-scale magnetic field. The morphology of
the outflow indicates that its axis lies close to the plane of the sky. We
measure velocities corrected for inclination of more than 90km/s which is
clearly incompatible with the expected properties of a FHSC outflow. Several
properties of the outflow are determined and compared to previous studies of
Class 0 and Class I protostars. The outflow of Cha-MMS1 has a much smaller
momentum force than the outflows of other Class 0 protostars. In addition, we
find a dynamical age of 200-3000yr indicating that Cha-MMS1 might be one of the
youngest ever observed Class 0 protostars. While the existence of the outflow
suggests the presence of a disk, no disk is detected in continuum emission and
we derive an upper limit of 55au to its radius. We conclude that Cha-MMS1 has
already gone through the FHSC phase and is a young Class 0 protostar, but it
has not brought its outflow to full power yet.
