Molecular outflows: Explosive versus protostellar
  With the recent recognition of a second, distinctive class of molecular
outflows, namely the explosive ones not directly connected to the
accretion-ejection process in the star formation, a juxtaposition of the
morphological and kinematic properties of both classes is warranted. By
applying the same method used in Zapata et al. (2009), and using
$^{12}$CO(J=2-1) archival data from the Submillimeter Array (SMA), we contrast
two well known explosive objects, Orion KL and DR21, to HH211 and DG Tau B, two
flows representative of classical low-mass protostellar outflows. At the moment
there are only two well established cases of explosive outflows, but with the
full availability of ALMA we expect that more examples will be found in the
near future. Main results are the largely different spatial distributions of
the explosive flows, consisting of numerous narrow straight filament-like
ejections with different orientations and in almost an isotropic configuration,
the red with respect to the blueshifted components of the flows (maximally
separated in protostellar, largely overlapping in explosive outflows), the very
well-defined Hubble flow-like increase of velocity with distance from the
origin in the explosive filaments versus the mostly non-organized CO velocity
field in protostellar objects, and huge inequalities in mass, momentum and
energy of the two classes, at least for the case of low-mass flows. Finally,
all the molecular filaments in the explosive outflows point back to
approximately a central position i.e. the place where its "exciting source" was
located, contrary to the bulk of the molecular material within the protostellar
outflows.
