The Next Generation Virgo Cluster Survey XVI. The Angular Momentum of
  Dwarf Early-Type Galaxies from Globular Cluster Satellites
  We analyze the kinematics of six Virgo cluster dwarf early-type galaxies
(dEs) from their globular cluster (GC) systems. We present new Keck/DEIMOS
spectroscopy for three of them and reanalyze the data found in the literature
for the remaining three. We use two independent methods to estimate the
rotation amplitude (Vmax) and velocity dispersion (sigma_GC) of the GC systems
and evaluate their statistical significance by simulating non-rotating GC
systems with the same number of GC satellites and velocity uncertainties. Our
measured kinematics agree with the published values for the three galaxies from
the literature and, in all cases, some rotation is measured. However, our
simulations show that the null hypothesis of being non-rotating GC systems
cannot be ruled out. In the case of VCC1861, the measured Vmax and the
simulations indicate that it is not rotating. In the case of VCC1528, the null
hypothesis can be marginally ruled out, thus, it might be rotating although
further confirmation is needed. In our analysis, we find that, in general, the
measured Vmax tends to be overestimated and the measured sigma_GC tends to be
underestimated by amounts that depend on the intrinsic Vmax/sigma_GC, the
number of observed GCs (N_GC), and the velocity uncertainties. The bias is
negligible when N_GC>~20. In those cases where a large N_GC is not available,
it is imperative to obtain data with small velocity uncertainties. For
instance, errors of <2km/s lead to Vmax<10km/s for a system that is
intrinsically not rotating.
