Genesis-metallicity: Universal Nonparametric Gas-phase Metallicity Estimation

Abstract We introduce genesis-metallicity , a gas-phase metallicity measurement P ython software employing the direct and strong-line methods depending on the available oxygen lines. The nonparametric strong-line estimator is calibrated based on a kernel density estimate in the four-dimensional space of O2 = [O ii ] λλ 3727,29/H β ; O3 = [O iii ] λ 5007/H β ; H β equivalent width EW(H β ); and gas-phase metallicity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>12</mml:mn> <mml:mo>+</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">O/H)</mml:mi> </mml:math> . We use a calibration sample of 1510 galaxies at 0 &lt; z &lt; 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 &gt; 1. We show that the O2, O3, and EW(H β ) 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 nonparametric T e (O ii ) electron temperature estimator based on a kernel density estimate in the five-dimensional space of O2, O3, EW(H β ), T e (O ii ), and T e (O iii ). This T e (O ii ) estimator is calibrated based on 1004 spectra with detections of both [O iii ] λ 4363 and [O ii ] λλ 7320,30, notably reporting 20 new NIRSpec detections of the [O ii ] λλ 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.