The Chemical Evolution Carousel of Spiral Galaxies: Azimuthal Variations of Oxygen Abundance in NGC1365

I-Ting Ho, Mark Seibert, Sharon E. Meidt, Rolf-Peter Kudritzki, Chiaki Kobayashi, Brent A. Groves, Lisa J. Kewley, Barry F. Madore, Jeffrey A. Rich, Eva Schinnerer, Joshua D'Agostino, Henry Poetrodjojo

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The spatial distribution of oxygen in the interstellar medium of galaxies is the key to understanding how efficiently metals that are synthesized in massive stars can be redistributed across a galaxy. We present here a case study in the nearby spiral galaxy NGC1365 using 3D optical data obtained in the TYPHOON Program. We find systematic azimuthal variations of the HII region oxygen abundance imprinted on a negative radial gradient. The 0.2 dex azimuthal variations occur over a wide radial range of 0.3 to 0.7 R25 and peak at the two spiral arms in NGC1365. We show that the azimuthal variations can be explained by two physical processes: gas undergoes localized, sub-kpc scale self-enrichment when orbiting in the inter-arm region, and experiences efficient, kpc scale mixing-induced dilution when spiral density waves pass through. We construct a simple chemical evolution model to quantitatively test this picture and find that our toy model can reproduce the observations. This result suggests that the observed abundance variations in NGC1365 are a snapshot of the dynamical local enrichment of oxygen modulated by spiral-driven, periodic mixing and dilution.
Original languageUndefined/Unknown
Article number39
Number of pages15
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 30 Aug 2017


  • astro-ph.GA

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