RAVE stars tidally stripped or ejected from the ω Centauri globular cluster^⋆,⋆⋆

¹ Institut Utinam, CNRS UMR 6213, Université de Franche-Comté, OSU THETA Franche-Comté-Bourgogne, Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France
e-mail: jfernandez@obs-besancon.fr
² Centro de Investigaciones de Astronomía, AP 264, 5101-A Mérida, Venezuela
³ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70264, 04510 México D.F., Mexico
⁴ Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, 67000 Strasbourg, France
⁵ Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ap. 70-543, 04510 D.F., México, Mexico

Received: 20 May 2015
Accepted: 10 August 2015

Abstract

Using six-dimensional phase-space information from the Fourth Data release of the RAdial Velocity Experiment (RAVE) over the range of Galactic longitude 240°<l< 360° and V_LSR< −239 km s^-1, we computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to ω Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of ω Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V_rel>V_esc,0) from the cluster, we identified 15 stars as having close encounters with ω Centauri: (i) 8 stars with relative velocities V_rel< 200 km s^-1 may have been ejected ~200 Myr ago from ω Centauri; (ii) another group of 7 stars were identified with high relative velocity V_rel> 200 km s^-1 during close encounters, and it seems unlikely that they were ejected from ω Centauri. We also confirm the link between J131340.4-484714 as a potential member of ω Centauri, and probably ejected ~2.0 Myr ago, with a relative velocity V_rel ~ 80 km s^-1.