Robust Data-driven Metallicities for 175 Million Stars from Gaia XP Spectra

Understand

We derive and publish data-driven estimates of stellar metallicities [M/H] for 175 million stars with low-resolution XP spectra published in Gaia DR3.

• The [M/H] values, along with Teff and logg, are derived using the XGBoost algorithm, trained on stellar parameters from APOGEE, augmented by a set of very metal-poor stars.
• XGBoost draws on a number of data features: the full set of XP spectral coefficients, narrowband fluxes derived from XP spectra, and broadband magnitudes.
• In particular, we include CatWISE magnitudes, as they reduce the degeneracy of Teff and dust reddening.