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Two kinematically different Large Magellanic Cloud old globular cluster populations unveiled from Gaia DR2 data sets

Published online by Cambridge University Press:  11 March 2020

Andrés E. Piatti
Affiliation:
Consejo Nacional de Investigaciones Cientficas y Técnicas, Godoy Cruz 2290, C1425FQB, Buenos Aires, Argentina Observatorio Astronómico de Córdoba, Laprida 854, 5000, Córdoba, Argentina email: [email protected]
Emilio J. Alfaro
Affiliation:
Instituto de Astrofsica de Andaluca, (CSIC), Glorieta de la Astronoma, S/N, Granada, 18008, Spain email: [email protected]
Tristan Cantat-Gaudin
Affiliation:
Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Mart i Franquès 1, E-08028 Barcelona, Spain email: [email protected]
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Abstract

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We derive mean proper motions of 15 known Large Magellanic Cloud (LMC) old globular clusters (GCs) from the Gaia DR2 data sets. When these mean proper motions are gathered with existent radial velocities to compose the GCs’ velocity vectors, we found that the projection of the velocity vectors onto the LMC plane and those perpendicular to it tell us about two distinct kinematical GC populations. Such a distinction becomes clear if the GCs are split at a perpendicular velocity of 10 km/s (absolute value). The two different kinematics groups also exhibit different spatial distributions. Those with smaller vertical velocities are part of the LMC disk, while those with larger values are closely distributed like a spheroidal component. Since GCs in both kinematic-structural components share similar ages and metallicities, we speculate with the possibility that their origins could have occurred through a fast collapse that formed halo and disk concurrently.

Type
Contributed Papers
Copyright
© International Astronomical Union 2020

Footnotes

This is an abridged version of the article published in extenso in MNRAS (2019), 484, L19.

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