Recovering age-metallicity distributions from integrated spectra: validation with MUSE data of a nearby nuclear star cluster

摘要: Current instruments and spectral analysis programs are now able to decompose the integrated spectrum of a stellar system into distributions ages metallicities. The reliability these methods have rarely been tested on nearby systems with resolved Here we derive age-metallicity distribution M54, nucleus Sagittarius dwarf spheroidal galaxy, from its MUSE spectrum. We find dominant old (8-14 Gyr), metal-poor (-1.5 dex) young (1 metal-rich (+0.25 component - consistent complex populations measured individual stars in same data set. There is excellent agreement between (mass-weighted) average age metallicity analyses. Differences only 3% 0.2 dex metallicitiy. By co-adding create M54's spectrum, show that recovered insensitive magnitude limit or contribution blue horizontal branch even when including additional wavelength coverage WAGGS survey. However, brightest can induce spurious recovery an ($>8$ population, which otherwise not expected our understanding chemical enrichment M54. overall derived mass-to-light ratio M54 M/L$_{\mathrm{V}}=1.46$ scatter 0.22 across field-of-view, attribute stochastic young, component. These findings provide strong evidence population be reliably spectra extragalactic systems.