Speaker
Description
The chemical enrichment state of galaxies is a result of a complex interplay between several mechanisms that (i) accrete pristine gas onto galaxies, (ii) cool down, fragment, and convert this pristine gas into stars, (iii) produce the heavy elements in the cores of massive stars, and (iv) release the newly formed heavy elements into the interstellar medium through stellar winds and supernovae. As such, scaling relations between gas-phase metallicity and other galaxy properties such as stellar mass and star-formation rate provide some of the most readily testable predictions of theoretical models and hydrodynamical simulations that can be directly calibrated against observational data. This has placed the measurements of gas-phase metallicity at the forefront of galaxy formation and evolution studies. The full array of faint emission lines required for precise gas-phase metallicity measurement is only available for a prohibitively small subsample (<1%) of spectroscopically targeted galaxies. Instead, strong emission-line ratios are used as proxies for gas-phase metallicity in large samples. For over three decades, the state-of-the-art has consisted of fitting polynomials to two-dimensional projections of the intrinsically multi-dimensional relation between gas-phase metallicity and strong emission-line ratios; this calibration is commonly carried out on samples where faint emission lines, and hence precise gas-phase metallicities, are available. This approach comes with several caveats, including (i) losing information as a result of projecting the complex parameter space onto two-dimensional planes, and (ii) saturation points where the gas-phase metallicity has a ~0.5-1.0 dex spread for little variation in the emission-line ratio. In this talk, I will present a novel approach where the full multi-dimensional relation between gas-phase metallicity and strong emission-line ratios is captured non-parametrically through kernel density estimation. This kernel density estimation is calibrated on the largest compilation of observational data to date, spanning distant galaxies in the early-universe to present-day galaxies. I will show that this approach achieves competitive accuracy in comparison to traditional techniques. Genesis-Metallicity is publicly available at: https://github.com/langeroodi/genesis_metallicity