Stellar Parameters for over 50 Million Stars from SMSS DR4 and Gaia DR3

Abstract We present an updated catalog of stellar parameters, including effective temperature, luminosity classification, and metallicity, for over fifty million stars from the SkyMapper Southern Survey (SMSS) DR4 and Gaia DR3. The accuracy of the derived parameters remains consistent with those achieved with SMSS DR2 using the same methods. Thanks to the advancements in SMSS DR4, photometric-metallicity estimates are now available for an unprecedented number of metal-poor stars. The catalog includes over 13 million metal-poor ([Fe/H] ≤ −1) stars, nearly three million very metal-poor ([Fe/H] ≤ −2.0) stars, and approximately 120,000 extremely metal-poor ([Fe/H] ≤ −3.0) stars—representing an increase by a factor of 4–6 compared to SMSS DR2. This catalog, combined with other stellar parameters obtained through our efforts, will be made available at the China-VO and Zenodo.