The role of the diffuse ionized gas in metallicity calibrations

TL;DR

This paper investigates how the diffuse ionized gas (DIG) affects metallicity estimates in galaxies, revealing that ignoring DIG leads to overestimations, and proposes correction methods using integral field spectroscopy data.

Contribution

It introduces a correction approach for DIG contamination in metallicity calibrations, improving the accuracy of gas-phase abundance estimates.

Findings

DIG causes overestimation of metallicities when ignored.

Correction methods reduce bias in the mass--metallicity--star formation rate relation.

Integral field spectroscopy enables effective DIG contribution correction.

Abstract

Estimates of gas-phase abundances based on strong-line methods have been calibrated for H~{\scshape ii} regions. Those methods ignore any contribution from the diffuse ionized gas (DIG), which shows enhanced collisional-to-recombination line ratios in comparison to H~{\scshape ii} regions of the same metallicity. Applying strong line methods whilst ignoring the role of the DIG thus systematically overestimates metallicities. Using integral field spectroscopy data, we show how to correct for the DIG contribution and how it biases the mass--metallicity--star formation rate relation.