Cluster kinematics and stellar rotation in NGC 419 with MUSE and
  adaptive optics
  We present adaptive optics (AO) assisted integral-field spectroscopy of the
intermediate-age star cluster NGC 419 in the Small Magellanic Cloud. By
investigating the cluster dynamics and the rotation properties of main sequence
turn-off stars (MSTO), we demonstrate the power of AO-fed MUSE observations for
this class of objects. Based on 1 049 radial velocity measurements, we
determine a dynamical cluster mass of 1.4+/-0.2x10^5 M_sun and a dynamical
mass-to-light ratio of 0.67+/-0.08, marginally higher than simple stellar
population predictions for a Kroupa initial mass function. A stacking analysis
of spectra at both sides of the extended MSTO reveals significant rotational
broadening. Our analysis further provides tentative evidence that red MSTO
stars rotate faster than their blue counterparts. We find average V sin i
values of 87+/-16 km/s and 130+/-22 km/s for blue and red MSTO stars,
respectively. Potential systematic effects due to the low spectral resolution
of MUSE can reach 30 km/s but the difference in V sin i between the populations
is unlikely to be affected.
