Azimuthal variations of gas-phase oxygen abundance in NGC 2997

TL;DR

This study reports significant azimuthal variations in gas-phase oxygen abundance within NGC 2997, revealing how oxygen disperses in spiral galaxies and highlighting the importance of high-resolution observations for understanding galactic chemical distributions.

Contribution

First detection of pronounced azimuthal oxygen abundance variations in NGC 2997 using high-resolution 3D spectroscopy, advancing understanding of chemical mixing in spiral galaxies.

Findings

Oxygen abundance varies by 0.06 dex azimuthally at fixed radius.

Higher oxygen levels are found in spiral arms compared to inter-arm regions.

Radial abundance gradient is consistent with other star-forming disks.

Abstract

The azimuthal variation of the HII region oxygen abundance in spiral galaxies is a key observable for understanding how quickly oxygen produced by massive stars can be dispersed within the surrounding interstellar medium. Observational constraints on the prevalence and magnitude of such azimuthal variations remain rare in the literature. Here, we report the discovery of pronounced azimuthal variations of HII region oxygen abundance in NGC 2997, a spiral galaxy at approximately 11.3 Mpc. Using 3D spectroscopic data from the TYPHOON Program, we study the HII region oxygen abundance at a physical resolution of 125 pc. Individual HII regions or complexes are identified in the 3D optical data and their strong emission line fluxes measured to constrain their oxygen abundances. We find 0.06 dex azimuthal variations in the oxygen abundance on top of a radial abundance gradient that is comparable to those seen in other star-forming disks. At a given radial distance, the oxygen abundances are highest in the spiral arms and lower in the inter-arm regions, similar to what has been reported in NGC 1365 using similar observations. We discuss whether the azimuthal variations could be recovered when the galaxy is observed at worse physical resolutions and lower signal-to-noise ratios.