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Resonant Trapping of the Moving Groups G18-39 and G21-22 in the Galactic Halo

Published online by Cambridge University Press:  30 October 2019

W. J. Schuster
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 106, Ensenada, B.C., 22800, México
E. Moreno
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, Ciudad Universitaria, CDMX, 04510, México emails: schuster@,
J. G. Fernández-Trincado
Institut Utinam, CNRS UMR 6213, Université Bourgogne-Franche-Comté, OSU THETA Franche-Comté, Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France.
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Orbital resonances in the Galactic halo have been studied using the Galactic mass model of Pichardo et al. (2003, 2004), including a Galactic bar. For the two moving groups of the Galactic halo, G18-39 and G21-22 (Silva et al. 2012), the majority of stars in both groups appear trapped in two resonances over the Galactic plane, generated by the bar. We have taken the rotation speed of the bar, Ωb, as 45-55 km s-1 kpc-1. So, these two moving groups are part of stellar supergroups which populate these two resonances. The position of these two groups in the Bottlinger diagram can be explained by the mean (U,V) field generated by these two resonances crossing the solar vicinity, in contrast with the alternate explanation of Silva et al. (2012), based on the simulations of Meza et al. (2005), that these two groups, seen as two peaks in the U Galactic velocity, have been created by the accretion of a dwarf galaxy by the Milky Way, such as that of Ω Centauri.

Contributed Papers
© International Astronomical Union 2019 


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