Metallicity Gradient of Barred Galaxies with TYPHOON

TL;DR

This study investigates how bars influence metallicity gradients in five nearby galaxies using TYPHOON/PrISM data, revealing diverse effects of bars on gas mixing and star formation across different galactic regions.

Contribution

It provides detailed observational evidence of the complex impact of bars on metallicity gradients and star formation in nearby galaxies, highlighting the need for larger samples and simulations.

Findings

Bars can flatten or steepen metallicity gradients inside the bar region.

Metallicity gradient breaks can be caused by gas accretion rather than bars.

Metallicity variations correlate with star formation rate fluctuations.

Abstract

Bars play an important role in mixing material in the inner regions of galaxies and stimulating radial migration. Previous observations have found evidence for the impact of a bar on metallicity gradients but the effect is still inconclusive. We use the TYPHOON/PrISM survey to investigate the metallicity gradients along and beyond the bar region across the entire star-forming disk of five nearby galaxies. Using emission line diagrams to identify star-forming spaxels, we recover the global metallicity gradients ranging from -0.0162 to -0.073 dex/kpc with evidence that the galactic bars act as an agent in affecting in-situ star formation as well as the motions of gas and stars. We observe cases with a `shallow-steep' metallicity radial profile, with evidence of the bar flattening the metallicity gradients inside the bar region (NGC~5068 and NGC~1566) and also note instances where the bar appears to drive a steeper metallicity gradient producing `steep-shallow' metallicity profiles (NGC~1365 and NGC~1744). For NGC~2835, a `steep-shallow' metallicity gradient break occurs at a distance $\sim$ 4 times the bar radius, which is more likely driven by gas accretion to the outskirt of the galaxy instead of the bar. The variation of metallicity gradients around the bar region traces the fluctuations of star formation rate surface density in NGC~1365, NGC~1566 and NGC~1744. A larger sample combined with hydrodynamical simulations is required to further explore the diversity and the relative importance of different ISM mixing mechanisms on the gas-phase metallicity gradients in local galaxies.