A self-consistent data-driven model for determining stellar parameters from optical and near-IR spectra

Abstract: Data-driven models, which apply machine learning to infer physical properties from large quantities of data, have become increasingly important for extracting stellar properties from spectra. In general, these methods have been applied to data in one wavelength regime or another. For example, APOGEE Net has been applied to near-IR spectra from the SDSS-V APOGEE survey to predict stellar parameters (Teff, log g, and [Fe/H]) for all stars with Teff from 3,000 to 50,000 K, including pre-main sequence stars, OB stars, main sequence dwarfs, and red giants. The increasing number of large surveys across multiple wavelength regimes provides the opportunity to improve data-driven models through learning from multiple datasets at once. In SDSS-V, a number of spectra of stars will be observed not just with APOGEE in near-IR, but also with BOSS in optical regime. Here we aim to develop a complementary model, BOSS Net, that will replicate the performance of APOGEE Net in these optical data through label transfer. We further improve the model by extending it to brown dwarfs, as well as white dwarfs, resulting in a comprehensive coverage between 1700<Teff<100,000 K and 0<log g<10, to ensure BOSS Net can reliably measure parameters of most of the commonly observed objects within this parameter space. We also update APOGEE Net to achieve a comparable performance in the near-IR regime. The resulting models provide a robust tool for measuring stellar evolutionary states, and in turn, enable characterization of the star forming history of the Galaxy.