The VMC Survey - XLII. Near-infrared period-luminosity relations for RR Lyrae stars and the structure of the Large Magellanic Cloud
Clementini, G.; Ripepi, V.; Garofalo, A.; Marconi, M.; Cusano, F.; Cioni, M. -R. L.; de Grijs, R.; van Loon, J. Th; Groenewegen, M. A. T.; Subramanian, S.; Moretti, M. I.; Oliveira, J. M.; Rubele, S.; Sun, N. -C.
Italy, Germany, Australia, China, Belgium, United Kingdom, India
Abstract
We present results from an analysis of ~29 000 RR Lyrae stars located in the Large Magellanic Cloud (LMC). For these objects, near-infrared time-series photometry from the VISTA survey of the Magellanic Clouds system (VMC) and optical data from the Optical Gravitational Lensing Experiment (OGLE) IV survey and the Gaia Data Release 2 catalogue of confirmed RR Lyrae stars were exploited. Using VMC and OGLE IV magnitudes we derived period-luminosity (PL), period-luminosity-metallicity (PLZ), period-Wesenheit (PW), and period-Wesenheit-metallicity (PWZ) relations in all available bands. More that 7000 RR Lyrae were discarded from the analysis because they appear to be overluminous with respect to the PL relations. The $PL_{K_{\mathrm{s}}}$ relation was used to derive individual distance to ${\sim}22\, 000$ RR Lyrae stars, and study the three-dimensional structure of the LMC. The distribution of the LMC RR Lyrae stars is ellipsoidal with the three axis S1 = 6.5 kpc, S2 = 4.6 kpc, and S3 = 3.7 kpc, inclination i = 22 ± 4° relative to the plane of the sky and position angle of the line of nodes θ = 167 ± 7° (measured from north to east). The north-eastern part of the ellipsoid is closer to us and no particular associated substructures are detected and neither any metallicity gradient.