This study by Guilherme Limberg investigates an intermediate-mass black hole (IMBH) in Omega Centauri (ωCen), the largest star cluster in the Milky Way. ωCen is considered a stripped nuclear star cluster (NSC) from a dwarf galaxy, likely the captured Gaia-Sausage/Enceladus (GSE) dwarf. This research connects the IMBH in ωCen with broader galactic evolution, extending known relationships between black holes and their host galaxies into the realm of dwarf galaxies.

Data

Limberg draws from a wide array of observational and theoretical resources. The study uses data from Milky Way-like galaxies, AGNs, and simulations to place ωCen within the mass and velocity dispersion relations. Information on stellar mass, velocity dispersion, and black hole mass estimates further frames ωCen’s role as a relic of galactic evolution.

Extending the MBH–M⋆ Relation

One key finding is that the IMBH in ωCen aligns with the scaling relation between black hole mass (MBH) and host galaxy stellar mass (M⋆). This suggests that the relationship, well-documented for massive galaxies, can be extended to dwarf galaxies. Importantly, this implies that galaxies similar in size to the GSE may host central black holes following the same evolutionary patterns as their larger counterparts.

Linking to the MBH–σ⋆ Relation

In addition to mass, ωCen’s black hole follows the MBH–σ⋆ relation, where σ⋆ represents the velocity dispersion of stars. This connection is shared by similar systems, such as ultracompact dwarf galaxies and NSCs with candidate IMBHs. These results strengthen the hypothesis that NSCs and ultracompact dwarfs evolve through similar processes, tying small systems to larger galaxy dynamics.

Implications for Black Hole Seeding

The study explores possible origins of the ωCen black hole. Two main theories—light seeds from early supernovae and heavy seeds from direct collapse—are considered. Limberg argues that the IMBH in ωCen could represent a lower bound for heavy seeds or an example of halted growth due to environmental stripping. This contrasts sharply with high-redshift galaxies hosting rapidly growing, overmassive black holes.

Additional Accreted NSCs

Limberg identifies other stripped NSCs in the Milky Way, such as NGC 6751 and NGC 6273, as potential hosts for IMBHs. However, challenges like tidal stripping and obscured fields make observations difficult. Expanding the search for IMBHs in similar systems is crucial for refining our understanding of black hole demographics.

Conclusion

This study highlights the significance of ωCen and similar systems in understanding the coevolution of black holes and galaxies. By extending established scaling relations into the dwarf galaxy regime, the findings encourage future observations and theoretical work on intermediate-mass black holes, their formation, and their role in shaping galaxies. The results suggest that both light and heavy seeding mechanisms may contribute to black hole diversity.

Source: Limberg