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How variations in the N/O–O/H relation bias gas-phase metallicity gradient measurements in galaxies.

Published onJun 01, 2020
How variations in the N/O–O/H relation bias gas-phase metallicity gradient measurements in galaxies.

Using a sample of 1000 galaxies from the MaNGA survey, we show that variations in the N/O ratio at fixed O/H can have a dramatic impact on the estimation of gas-phase oxygen abundance gradients in galaxies. Radial variations in the N/O - O/H relation within galaxies can induce ~40% biases in their estimated abundance gradients. These biases trend with total stellar mass, such that higher-mass galaxies appear to have shallower gradients when nitrogen-sensitive abundance indicators are used. We show empirically that departures from the expected N/O-O/H relation are correlated with variations in the local star formation efficiency. While this has been predicted by recent models for galactic chemical evolution, we cannot rule out other processes such as radial migration also playing a role.

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