The VMC survey – XLVI. Stellar proper motions in the centre of the Large Magellanic Cloud

Abstract

ABSTRACT We present proper motion (PM) measurements within the central region of the Large Magellanic Cloud (LMC), using near-infrared data from the VISTA survey of the Magellanic Cloud system (VMC). This work encompasses 18 VMC tiles covering a total sky area of ∼28 deg2. We computed absolute stellar PMs from multiepoch observations in the Ks filter over time baselines between ∼12 and 47 months. Our final catalogue contains ∼6322 000 likely LMC member stars with derived PMs. We employed a simple flat-rotating disc model to analyse and interpret the PM data. We found a stellar centre of rotation ($\alpha _{0} = 79.95^{\circ }\,^{+0.22}_{-0.23}$, $\delta _0 = -69.31^{\circ }\,^{+0.12}_{-0.11}$) that is in agreement with that resulting from Hubble Space Telescope data. The inferred viewing angles of the LMC disc ($i=33.5^{\circ }\,^{+1.2}_{-1.3}$, $\Theta =129.8^{\circ }\,^{+1.9}_{-1.9}$) are in good agreement with values from the literature but suggest a higher inclination of the central parts of the LMC. Our data confirm a higher rotation amplitude for the young (≲0.5 Gyr) stars compared to the intermediate-age/old (≳1 Gyr) population, which can be explained by asymmetric drift. We constructed spatially resolved velocity maps of the intermediate-age/old and young populations. Intermediate-age/old stars follow elongated orbits parallel to the bar’s major axis, providing first observational evidence for x1 orbits within the LMC bar. In the innermost regions, the motions show more chaotic structures. Young stars show motions along a central filamentary bar structure.