Temperature-based radial metallicity gradients in nearby galaxies
Year: 2025
Type: article
Abstract: Context. Gas-phase abundances provide insights into the baryon cycle, with radial gradients and 2D metallicity distributions tracking how metals are built up and redistributed across galaxy disks over cosmic time. Aims. We use a catalog of 22 958 H II regions across 19 nearby spiral galaxies to examine how precisely the radial abundance gradients can be traced when using only the [N II ] λ 5755 electron temperature as a proxy for temperature-based, direct method metallicities. Methods. Using 534 direct detections of the temperature sensitive [N II ] λ 5755 auroral line, we measured gradients in 15 of the galaxies. Leveraging our large catalog of individual H II regions, we carried out a stacking procedure in bins of the H II region [N II ] λ 6583 luminosity and radius to recover stacked radial gradients. Results. We found a good agreement between the metallicity gradients from the stacked spectra and those gradients from individual regions and those from strong-line methods. In addition, particularly in the stacked T e [N II ] measurements, some galaxies show very low (< 0.05 dex) scatter in metallicities, indicative of a well-mixed ISM. We examined the individual high confidence (S/N > 5) outliers and identified 13 regions across nine galaxies with anomalously low metallicities, although this is not strongly reflected in the strong-line method metallicities. By stacking arm and interarm regions, we found no systematic evidence for offsets in metallicity between these environments, suggesting that enrichment within spiral arms is due to very localized processes. Conclusions. This work demonstrates the potential to systematically exploit the single [N II ] λ 5755 auroral line for detailed gas-phase abundance studies of galaxies. It provides strong validation of previous results, based on the strong-line calibrations, of a well-mixed ISM across typical star-forming spiral galaxies.
Source: Astronomy and Astrophysics
Authors: K. Kreckel, R. J. Rickards Vaught, O. V. Egorov, J. E. Méndez-Delgado, F. Belfiore, M. Brazzini, E. Egorova, E. Congiu, D. A. Dale, S. Dlamini, S. C. O. Glover, K. Grasha, R. S. Klessen, F.-H. Liang, H.-A. Pan, P. Sánchez-Blázquez, T. G. Williams
Institutions: Heidelberg University, Space Telescope Science Institute, Universidad Nacional Autónoma de México, Arcetri Astrophysical Observatory, National Institute for Astrophysics, University of Trieste, European Southern Observatory, European Southern Observatory, University of Wyoming, University of Cape Town, Australian National University, Harvard University, Center for Astrophysics Harvard & Smithsonian, Tamkang University, Universidad Complutense de Madrid, University of Oxford
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funder: Deutsche Forschungsgemeinschaft
Award: G3889686005
OpenAlex ID: W7083191262