Genesis-Metallicity: Universal Non-Parametric Gas-Phase Metallicity Estimation

Abstract

We introduce genesis-metallicity, a gas-phase metallicity measurement python software employing the direct and strong-line methods depending on the available oxygen lines. The non-parametric strong-line estimator is calibrated based on a kernel density estimate in the 4-dimensional space of O2 = [O II]$\lambda\lambda 3727,29$/H$\beta$; O3 = [O III]$\lambda 5007$/H$\beta$; H$\beta$ equivalent width EW(H$\beta$); and gas-phase metallicity $12 + \log$(O/H). We use a calibration sample of 1510 galaxies at $0 < z < 10$ with direct-method metallicity measurements, compiled from the JWST/NIRSpec and ground-based observations. In particular, we report 122 new NIRSpec direct-method metallicity measurements at $z > 1$. We show that the O2, O3, and EW(H$\beta$) measurements are sufficient for a gas-phase metallicity estimate that is more accurate than 0.09 dex. Our calibration is universal, meaning that its accuracy does not depend on the target redshift. Furthermore, the direct-method module employs a non-parametric ${\rm T}_{\rm e}$(O II) electron temperature estimator based on a kernel density estimate in the 5-dimensional space of O2, O3, EW(H$\beta$), ${\rm T}_{\rm e}$(O III), and ${\rm T}_{\rm e}$(O II). This ${\rm T}_{\rm e}$(O II) estimator is calibrated based on 1004 spectra with detections of both [O III]$\lambda 4363$ and [O II]$\lambda\lambda 7320,30$, notably reporting 20 new NIRSpec detections of the [O II]$\lambda\lambda 7320,30$ doublet. We make genesis-metallicity and its calibration data publicly available and commit to keeping both up-to-date in light of the incoming data.