  We present $^{12}$CO(2-1) line and 1300 $\mu$m continuum observations made
with the Submillimeter Array (SMA) of the young star DG Tau B. We find, in the
continuum observations, emission arising from the circumstellar disk
surrounding DG Tau B. The $^{12}$CO(2-1) line observations, on the other hand,
revealed emission associated with the disk and the asymmetric outflow related
with this source. Velocity asymmetries about the flow axis are found over the
entire length of the flow. The amplitude of the velocity differences is of the
order of 1 -- 2 km s$^{-1}$ over distances of about 300 -- 400 AU. We interpret
them as a result of outflow rotation. The sense of the outflow and disk
rotation is the same. Infalling gas from a rotating molecular core cannot
explain the observed velocity gradient within the flow. Magneto-centrifugal
disk winds or photoevaporated disk winds can produce the observed rotational
speeds if they are ejected from a keplerian disk at radii of several tens of
AU. Nevertheless, these slow winds ejected from large radii are not very
massive, and cannot account for the observed linear momentum and angular
momentum rates of the molecular flow. Thus, the observed flow is probably
entrained material from the parent cloud. DG Tau B is a good laboratory to
model in detail the entrainment process and see if it can account for the
observed angular momentum.
