Tidal Debris Candidates from the $ω$ Centauri Accretion Event and its Role in Building Up the Milky Way Halo
Tidal Debris Candidates from the $ω$ Centauri Accretion Event and its Role in Building Up the Milky Way Halo
Borja Anguiano, Arik Mitschang, Takanobu Kirihara, Yutaka Hirai, Danny Horta, Sten Hasselquist, Ricardo P. Schiavon, Steven R. Majewski, Andrew C. Mason, Adrian M. Price-Whelan, Carlos Allende Prieto, Verne Smith, Katia Cunha, David L. Nidever
AbstractWe identify stellar tidal debris from the $\omega$ Centauri ($\omega$ Cen) system among field stars in the APOGEE survey via chemical tagging using a neural network trained on APOGEE observations of the $\omega$ Cen core. We find a total of 463 $\omega$ Cen debris candidates have a probability $P > 0.8$ of sharing common patterns in their chemical abundances across a range of individual elements or element combinations, including [C+N], O, Mg, Al, Si, Ca, Ni, and Fe. Some debris candidates show prograde or retrograde disk-like kinematics, but most show kinematics consistent with the accreted halo, showing high radial actions, $J_{R}$, values. We find that a sample of Gaia-Sausage-Enceladus (GES) members are chemically distinct from the $\omega$ Cen core, suggesting that $\omega$ Cen is associated to an independent merger event shaping the Milky Way halo. However, a connection between GSE and $\omega$ Cen cannot be ruled out. A detailed comparison with $N$-body simulations indicates that the $\omega$ Cen progenitor was a massive dwarf galaxy ($\gtrsim 10^8 M_{\odot}$). The existence of a metal-poor high-$\alpha$ chemically homogeneous halo debris is also reported.