Nuclear star cluster at 3pc from Sgr A*

We also constrained the metallicity of the stellar population, further refined by spectroscopic data from the literature. The NSC stellar population is predominantly old and metal-rich, with 75.6+/-9.5% of the stellar mass formed >~10Gyr ago and a median metallicity of [M/H]~+0.35. Significant contributions come from an intermediate-age population around 2-3Gyr (20.8+/-8.7%), while minor components appear at ~400Myr (0.9+/-0.8%) and 20Myr (3.6+/-1.4%), the latter representing a small but non-negligible young population.

Systematic uncertainties related to stellar evolution models, binning, photometric range, unresolved binaries, and filter selection are considered. Our findings indicate that the NSC formed predominantly in an early episode, with a substantial contribution from a star formation episode 2-3 Gyr ago and minor younger components. The metallicity estimates are consistent with spectroscopic measurements, and the results agree with the stellar population properties of the inner NSC and the inner nuclear stellar disc, providing useful constraints on the transition between these two structures.