Azimuthal variations of gas-phase oxygen abundance in NGC 2997

¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
e-mail iting@mpia.de
² Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
³ University Observatory Munich, Scheinerstr. 1, 81679 Munich, Germany
⁴ Research School of Astronomy and Astrophysics, Australian National University, Canberra 2600, ACT, Australia
⁵ Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101, USA
⁶ Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK

Received: 19 April 2018
Accepted: 5 July 2018

Abstract

The azimuthal variation of the H II 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 H II region oxygen abundance in NGC 2997, a spiral galaxy at approximately 11.3 Mpc. Using 3D spectroscopic data from the TYPHOON Program, we have studied the H II region oxygen abundance at a physical resolution of 125 pc. Individual H II 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.