RAVE stars tidally stripped/ejected from $\omega$ Centauri globular cluster

Abstract

Using six-dimesional phase-space information from the Fourth Data release of the Radial Velocity Experiment (RAVE) over the range of Galactic longitude 240$^{\circ}< l <$ 360$^{\circ}$ and $V_{LSR} < -239$ kms$^{-1}$, we have computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to $\omega$ Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of $\omega$ 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 $\omega$ Centauri: (\textit{i}) 8 stars with relative velocities $V_{rel}< 200 $ kms$^{-1}$ may have been ejected $\sim$ 200 Myr ago from $\omega$ Centauri; (\textit{ii}) other group of 7 stars were identified with high relative velocity $V_{rel}> 200 $ kms$^{-1}$ during close encounters, and seems unlikely that they have been ejected from $\omega$ Centauri. We also confirm the link between J131340.4-484714 as potential member of $\omega$ Centauri, and probably ejected $\sim$ 2.0 Myr ago, with a relative velocity $V_{rel}\sim80$ kms$^{-1}$.