A pristine view of galactic globular clusters and their peripheries: Omega Centauri

Abstract

The central regions of the globular cluster Omega Centauri ($\omega$ Cen) have been extensively studied, but its outer regions and tidal structure have been less so. Gaia's astrometry uncovered substantial tidal substructure associated with $\omega$ Cen, yet the lack of chemical tagging makes these associations tenuous. In this paper, we utilize the Gaia-synthetic CaHK-band photometry, metallicities from the Pristine survey and Gaia's astrometry to explore up to a clustercentric radius of 5 deg from $\omega$ Cen. We identify $\omega$ Cen-like stars based on proper motion, colour-magnitude, and colour-colour space, exploring the morphology, and stellar populations of the outer regions. Our probabilistic approach recovers the tidal tails of $\omega$ Cen, and we investigate the metallicity distribution of $\omega$ Cen ranging from a radius of 15 arcmin to the tidal radius, and beyond into the tidal tails. We present (1) two components between 15 arcmin and tidal radius at -1.83 and -1.45 dex that are also the dominant populations within 15 arcmin, and (2) the first evidence that the same two populations in the outer regions of the cluster are present outside the tidal radius and into the tidal tails. These populations are mixed about the stream and are typically amongst the faintest stars in our sample, indicating that the tidal tails are made of tidally stripped $\omega$ Cen stars.