Formation of ω Centauri from an ancient nucleated dwarf galaxy in the young Galactic disc |
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| Authors: | K Bekki K C Freeman |
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| Institution: | School of Physics, University of New South Wales, Sydney 2052, NSW, Australia;Research School of Astronomy &Astrophysics, Mt Stromlo Observatory, The Australian National University, Cotter Road, Weston Creek, ACT 2611, Australia |
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| Abstract: | We first present a self-consistent dynamical model in which ω Cen is formed from an ancient nucleated dwarf galaxy merging with the first generation of the Galactic thin disc in a retrograde manner with respect to the Galactic rotation. Our numerical simulations demonstrate that during merging between the Galaxy and the ω Cen host dwarf with M B??14 mag and its nucleus mass of 107 M⊙ , the outer stellar envelope of the dwarf is nearly completely stripped, whereas the central nucleus can survive from the tidal stripping because of its compactness. The developed naked nucleus has a very bound retrograde orbit around the young Galactic disc, as observed for ω Cen, with apocentre and pericentre distances of ～8 and ～1 kpc, respectively. The Galactic tidal force can induce radial inflow of gas to the centre of the dwarf and consequently triggers moderately strong nuclear starbursts in a repetitive manner. This result implies that efficient nuclear chemical enrichment resulting from the later starbursts can be closely associated with the origin of the observed relatively young and metal-rich stars in ω Cen. Dynamical heating by the ω Cen host can transform the young thin disc into the thick disc during merging. |
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| Keywords: | globular clusters: individual: ω Centauri |
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