Bar-induced migration of ω Centauri away from Gaia Sausage-Enceladus

Abstract The globular cluster ω Cen has been suggested to have originated in the Gaia Sausage-Enceladus (GSE) merger event, possibly as its nuclear star cluster. However, the present-day orbits of ω Cen and the GSE debris are very different. We investigate the scenario in which ω Cen originated in the GSE and migrated to its current position due to perturbations from the Galactic bar. The [α/M] distributions of stars located between the GSE debris and ω Cen in (Lz, E) space tentatively support this scenario, but are not conclusive. We run simulations of the GSE debris and ω Cen in a realistic Milky Way potential with a decelerating bar at various present-day pattern speeds. We find that ω Cen can indeed be traced back to the phase space region occupied by the GSE debris. However, this would likely require a pattern speed of Ωb ≲ 26 km s−1 kpc−1, which is much lower than most recent estimates. We conclude that a GSE origin for ω Cen is dynamically and chemically plausible, but only with a re-evaluation of the current consensus on the bar’s pattern speed.