• DOI:10.1051/0004-6361/202039778
• Corpus ID: 245117724

Disentangling the formation mechanisms of nuclear star clusters

@article{Fahrion2021DisentanglingTF,
  title={Disentangling the formation mechanisms of nuclear star clusters},
  author={Katja Fahrion and Ryan Leaman and Mariya Lyubenova and Glenn van de Ven},
  journal={Astronomy \& Astrophysics},
  year={2021}
}

• K. Fahrion, R. Leaman, +1 author G. Ven
• Published 6 December 2021
• Physics
• Astronomy & Astrophysics

Nuclear star clusters (NSCs) are massive star clusters found ubiquitously in the centres of galaxies, from the dwarf regime to massive ellipticals and spirals. The fraction of nucleated galaxies is as high as > 90% at M gal ∼ 10 9 M (cid:12) . However, how NSC formation mechanisms work in di ff erent regimes and what determines galaxy nucleation is still unclear. The dissipationless accretion of infalling globular clusters (GCs) and the in situ formation of stars directly at the galactic centre likely operate to grow NSCs in most galaxies; however, their e ffi ciency has been di ffi cult to assess observationally. Here, we provide, for the first time, a quantitative determination of the relative strength of these processes in the build-up of individual NSCs. Using a semi-analytical model of NSC formation based on the orbital evolution of inspiraling GCs, together with observed NSC and GC system properties, we derived the mass fraction of in situ born stars f in , NSC for 119 galaxies with masses from 3 × 10 7 to 3 × 10 11 M (cid:12) , in the Local Volume, the Fornax, and Virgo galaxy clusters. Our analysis reveals that the NSC mass, as well as the ratio of NSC to the total GC system mass, are strong indicators of the dominant NSC formation channel, and not the total galaxy stellar mass as previously suggested. More massive NSCs formed predominantly via the in situ formation of stars ( f in , NSC ∼ 0 . 9), while the lower-mass NSCs are expected to have formed predominantly through the merger of GCs ( f in , NSC ∼ 0 . 2). The results of this simple model are in agreement with recent independent estimates of the dominant NSC formation channel from recent stellar population analysis.