KURVS: chemical properties from multiple strong line calibrations for star-forming galaxies at $z\sim1.5$

TL;DR

This study analyzes the gas-phase metallicity and its radial gradients in 43 star-forming galaxies at z~1.5 using multiple emission line calibrations, revealing mostly flat gradients consistent with galaxy evolution models.

Contribution

First application of N$_2$O$_2$ metallicity indicator at z~1.5, providing new insights into metallicity gradients and their relation to galaxy evolution processes.

Findings

Metallicity gradients are mostly flat at z~1.5.

N$_2$O$_2$ and N$_2$ indicators agree when accounting for dust.

Negative gradients suggest self-regulation; positive gradients imply mergers or fountains.

Abstract

Gas-phase oxygen abundance (metallicity) properties can be constrained through emission line analyses, and are of great importance to investigate galaxy evolution histories. We present an analysis of the integrated and spatially-resolved rest-frame optical emission line properties of the ionised gas in 43 star-forming galaxies at $z\sim1.5$ in the KMOS Ultra-deep Rotational Velocity Survey (KURVS). Using the [NII]$\lambda6584$/H$\alpha$ (N$_2$), ([OII]$\lambda\lambda3727,9+$[OIII]$\lambda\lambda4959,5007$)/H$\beta$ (R23), and for the first time [NII]$\lambda6584$/[OII]$\lambda\lambda3727,9$ (N$_2$O$_2$) indicators at this redshift, we measure the gas-phase metallicities and their radial gradients. On $\sim4$-kpc scales metallicity gradients measured from N$_2$O$_2$ and those measured from N$_2$ are in good agreement when considering the spatial distributions of dust in each galaxy, as parameterised by dust attenuation radial gradients. We report a nearly flat metallicity gradient distribution typically at $z\sim1.5$, with the 50th, 16th and 84th percentiles at $0.01$, $-0.03$, and $0.05$ dex kpc$^{-1}$, respectively. The findings agree well with previous observational studies and simulations at this epoch. We ascribe the observed negative metallicity gradients to a natural result from self-regulating systems, and the positive ones to potential galactic fountains and higher merger rates.