Accurate radial velocity and metallicity of the Large Magellanic Cloud
  old globular clusters NGC 1928 and NGC 1939
  We present results obtained from spectroscopic observations of red giants
located in the fields of the Large Magellanic Cloud (LMC) globular clusters
(GCs) NGC 1928 and NGC 1939. We used the GMOS and AAOmega+2dF spectrographs to
obtain spectra centred on the CaII triplet, from which we derived individual
radial velocities (RVs) and metallicities. From cluster members we derived mean
RVs of RV_NGC1928=249.58+-4.65 km/s and RV_NGC939=258.85+-2.08 km/s, and mean
metallicities of [Fe/H]_NGC1928=-1.30+-0.15 dex and [Fe/H]_NGC1939=-2.00+-0.15
dex. We found that both GCs have RVs and positions consistent with being part
of the LMC disc, so that we rule out any possible origin but that in the same
galaxy. By computing the best solution of a disc that fully contains each GC,
we obtained circular velocities for the 15 known LMC GCs. We found that 11/15
of the GCs share the LMC rotation derived from $HST$ and $Gaia$ DR2 proper
motions. This outcome reveals that the LMC disc existed since the very early
epoch of the galaxy formation and experienced the steep relatively fast
chemical enrichment shown by its GC metallicities. The four remaining GCs
turned out to have circular velocities not compatible with an in situ cluster
formation, but rather with being stripped from the SMC.
