We analysed Washington CM T 1 photometry of star clusters located along the minor axis of the LMC, from the LMC optical centre up to ∼ 39 degrees outwards to the North-West. The data base was exploited in order to search for new star cluster candidates, to produce cluster CMDs cleaned from field star contamination and to derive age estimates for a statistically complete cluster sample. We confirmed that 146 star cluster candidates are genuine physical systems, and concluded that an overall ∼ 30 per cent of catalogued clusters in the surveyed regions are unlikely to be true physical systems. We did not find any new cluster candidates in the outskirts of the LMC (deprojected distance > ∼ 8 degrees). The derived ages of the studied clusters are in the range 7.2 < log(t yr −1 ) ≤ 9.4, with the sole exception of the globular cluster NGC 1786 (log(t yr −1 ) = 10.10). We also calculated the cluster frequency for each region, from which we confirmed previously proposed outside-in formation scenarios. In addition, we found that the outer LMC fields show a sudden episode of cluster formation (log(t yr −1 ) ∼ 7.8-7.9) that continued until log(t yr −1 ) ∼ 7.3 only in the outermost LMC region. We link these features to the first pericentre passage of the LMC to the MW, which could have triggered cluster formation due to ram pressure interaction between the LMC and MW halo.
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 Ca II triplet, from which we derived individual radial velocities (RVs) and metallicities. From cluster members we derived mean RVs of RV NGC 1928 = 249.58±4.65 km/s and RV NGC 1939 = 258.85±2.08 km/s, and mean metallicities of [Fe/H] NGC 1928 = −1.30±0.15 dex and [Fe/H] NGC 1939 = −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.
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