The role of gas kinematics in setting metallicity gradients at high redshift

In this work, we explore the diversity of ionized gas kinematics (rotational velocity v(phi) and velocity dispersion sigma(g)) and gas-phase metallicity gradients at 0.1 <= z <= 2.5 using a compiled data set of 74 galaxies resolved with ground-based integral field spectroscopy. We find that galaxies with the highest and the lowest sigma(g) have preferentially flat metallicity gradients, whereas those with intermediate values of sigma(g) show a large scatter in the metallicity gradients. Additionally, steep negative gradients appear almost only in rotation-dominated galaxies (v(phi)/sigma(g) > 1), whereas most dispersion-dominated galaxies show flat gradients. We use our recently developed analytical model of metallicity gradients to provide a physical explanation for the shape and scatter of these observed trends. In the case of high sigma(g), the inward radial advection of gas dominates over metal production and causes efficient metal mixing, thus giving rise to flat gradients. For low sigma(g), it is the cosmic accretion of metal-poor gas diluting the metallicity that gives rise to flat gradients. Finally, the reason for intermediate sigma(g) showing the steepest negative gradients is that both inward radial advection and cosmic accretion are weak as compared to metal production, which leads to the creation of steeper gradients. The larger scatter at intermediate sigma(g) may be due in part to preferential ejection of metals in galactic winds, which can decrease the strength of the production term. Our analysis shows how gas kinematics play a critical role in setting metallicity gradients in high-redshift galaxies.

Automated summary

In this study, the relationship between ionized gas kinematics and gas-phase metallicity gradients in high-redshift galaxies is explored using data from 74 galaxies. The findings suggest a correlation between velocity dispersion and metallicity gradients, with rotation-dominated galaxies showing flat gradients. The analysis highlights the critical role of gas kinematics in shaping metallicity gradients in high-redshift galaxies.