http://arxiv.org/abs/2303.12828
Nuclear star clusters (NSCs) are massive star clusters found in the innermost region of the majority of galaxies. While recent studies suggest that low-mass NSCs in dwarf galaxies form largely out of the merger of globular clusters and NSCs in massive galaxies have assembled most of their mass through central star formation, the formation channel of the Milky Way’s NSC is still uncertain. In this work, we use GigaEris, a very high resolution $N$-body hydrodynamical cosmological
zoom-in'' simulation, to investigate NSC formation in the progenitor of a Milky Way-sized galaxy, as well as its relation to the assembly and evolution of the galactic nuclear region. We study the possibility that bound, young, gas-rich, stellar clusters within a radius of 1.5~kpc of the main galaxy's centre at $z>4$ are the NSC predecessors (NSCPs). We identify 53 systems which satisfy our criteria, with a total baryonic mass of $10^{7.7}$~M$_{\odot}$. They have a relatively low mean stellar metallicity ($-0.47 \lesssim {\rm [Fe/H]} \lesssim -0.11$) in comparison to the present-day stars in the Milky Way's NSC. The NSCPs with a `born thin-disc' star fraction, $F_{\rm thin}$, higher than 0.5 are older and display slightly different properties than the clusters with $F_{\rm thin} \leq 0.5$. We demonstrate that both stellar cluster accretion and in-situ star formation will contribute to the formation of the NSC, providing evidence for an hybrid formation scenario for the first time in an $N$-body, hydrodynamical, cosmologicalzoom-in” simulation. Furthermore, we also identify a nuclear stellar ring in the simulation, with properties similar to those of the Milky Way’s nuclear stellar disc.
F. Donkelaar, L. Mayer, P. Capelo, et. al.
Fri, 24 Mar 23
40/56
Comments: 12 pages, 10 figures, submitted to MNRAS