Stirred, not shaken: Dislodging $ω$ Centauri from the Sausage galaxy through bar resonances
Year: 2026
Type: preprint
Abstract: We test the idea proposed by Laporte \& Orkney that $ω$ Centauri ($ω$Cen) is the central nuclear star cluster of the Gaia-Sausage-Enceladus galaxy (GSE) which got dislodged by the bar. We run a series of simulations in time-evolving bar potentials with present-day pattern speeds within Portail et al's $Ω_{b}=39\pm3.5\,\rm{km\,s^{-1}\,kpc^{-1}}$ and rate of slow-down $\dotΩ_{\rm b}= 4.5 \pm 1.4 \,\rm{km \,s^{-1}\,kpc^{-1}\, Gyr^{-1}}$ to study how bar resonances modulate the angular momentum and energies of both GSE-debris and $ω$Cen's location in $(E,L_{z})$ space. We find that the retrograde $3:2$ resonance is capable of inflicting changes of $ΔE\approx0.4\times10^{5}\,\rm{km^{2}\, s^{-2}}$, $ΔL_{z}\approx0.3-0.5\times10^{3}\, \rm{km \, s^{-1}\, kpc^{-1}}$ within timescales of $Δt\approx 0.5-1\,\rm{Gyr}$, well within the bar's lifespan $t_{\rm{bar}}\approx10-8\,\rm{Gyr}$. These results are independent of the choice of potential or modelling. We uncover a sample of N-rich stars with metallicities $-2.0<[\rm{Fe/H}]<-1.0$ and aluminium enrichments consistent with $ω$Cen. In ($E,L_{z}$) space, the map reveals a corridor of trailing N-rich stars clustered about the region connecting $ω$Cen to the GSE's debris centroid, matching $ω$Cen's past predicted track. This provides the best evidence yet that $ω$Cen is the nuclear star cluster of the GSE. Using M54 and $ω$Cen's chemistry we show that neither first nor second generations follow general galaxy-wide scale chemical enrichment trends. This is empirical evidence that GC chemical trends are a cluster-scale physics problem, not a galaxy-wide one.
Source: arXiv (Cornell University)
Institutions: Université Paris Cité, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Institut d'Estudis Espacials de Catalunya, Institut de Ciències del Cosmos, Universitat de Barcelona, Centre National de la Recherche Scientifique, University of Florence, Observatoire astronomique de Strasbourg, Université de Strasbourg
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220992256