CLASSY XII: nitrogen enrichment shaped by gas density and feedback
ABSTRACT We investigate the chemical evolution of N/O using a sample of 45 local star-forming galaxies from the CLASSY survey. This sample spans a wide range of galaxy properties, with robust determinations of nitrogen and oxygen abundances via the direct-$T_{\rm e}$ method. We explore how N/O relates to density structure, stellar mass, star formation rate (SFR), stellar age, compactness, and gas kinematics. In addition, we compare our results with those of galaxies at $z =2\!-\!10$ where N/O ratios were derived from optical or UV nitrogen lines, aiming to identify chemical enrichment pathways across cosmic time. Our analysis shows that the N/O–O/H relation in CLASSY galaxies aligns with the trends seen in local galaxies and extragalactic H ii regions, and that galaxies at $z = 2\!-\!6$ exhibit similar N/O values, indicating no significant redshift evolution in N/O for a fixed metallicity. We identify a significant correlation between electron density $n_{\rm e}$([S ii]) and N/O, suggesting that density structure contributes to the scatter in the N/O–O/H relation. The CLASSY galaxies with high SFRs or compact star formation show elevated N/O, though no strong correlation with stellar mass is found. We also find that high-velocity outflows ($v_{\rm out}\gtrsim 350$ km s−1) and low mass-loading factors are linked to elevated N/O, indicating that feedback plays a significant role. These results highlight the importance of density, star formation, and feedback from young stellar populations in shaping N/O enrichment and provide key insights for interpreting high-$z$ galaxies observed with James Webb Space Telescope.
Authors
- Matthew Hayes (ORCID: https://orcid.org/0000-0001-8587-218X)
- Matilde Mingozzi (ORCID: https://orcid.org/0000-0003-2589-762X)
- Nimisha Kumari (ORCID: https://orcid.org/0000-0002-5320-2568)
- Crystal L. Martin (ORCID: https://orcid.org/0000-0001-9189-7818)
- Peter Senchyna (ORCID: https://orcid.org/0000-0002-9132-6561)
- Fiorenzo Vincenzo (ORCID: https://orcid.org/0000-0002-0743-9994)
- Aida Wofford (ORCID: https://orcid.org/0000-0001-8289-3428)
- Sophia R. Flury (ORCID: https://orcid.org/0000-0002-0159-2613)
- Timothy G. Heckman (ORCID: https://orcid.org/0000-0003-1127-7497)
- Karla Z. Arellano-Córdova (ORCID: https://orcid.org/0000-0002-2644-3518)
- Danielle A. Berg (ORCID: https://orcid.org/0000-0002-4153-053X)
- Bethan L. James (ORCID: https://orcid.org/0000-0003-4372-2006)
- Valentina Abril-Melgarejo (ORCID: https://orcid.org/0000-0002-2764-6069)
- Claus Leitherer (ORCID: https://orcid.org/0000-0003-2685-4488)
- Svea Hernández (ORCID: https://orcid.org/0000-0003-4857-8699)
- Chiaki Kobayashi (ORCID: https://orcid.org/0000-0002-4343-0487)
- Nicole H. Rogers
- Fergus Cullen (ORCID: https://orcid.org/0000-0002-3736-476X)
- Evan D. Skillman (ORCID: https://orcid.org/0000-0003-0605-8732)
- R. Amorín (ORCID: https://orcid.org/0000-0001-5758-1000)
- Kaelee S. Parker (ORCID: https://orcid.org/0000-0002-8809-4608)
- Claudia Scarlata (ORCID: https://orcid.org/0000-0002-9136-8876)
- John Chisholm (ORCID: https://orcid.org/0000-0002-0302-2577)
- Martha Stephenson
Institutions
- Northwestern University (US)
- Australian National University (AU)
- Centre National de la Recherche Scientifique (FR)
- Space Telescope Science Institute (US)
- University of Minnesota (US)
- University of Hertfordshire (GB)
- Johns Hopkins University (US)
- University of California, Santa Barbara (US)
- Stockholm University (SE)
- Carnegie Institution for Science (US)
- Observatoire de Paris (FR)
- Mount Stromlo Observatory (AU)
- Ensenada Institute of Technology (MX)
- University of Catania (IT)
- ASTRO-3D (AU)
- Royal Observatory (GB)
- Center for Astrophysics Harvard & Smithsonian (US)
- Carnegie Observatories (US)
- AlbaNova (SE)
- ARC Centre of Excellence for All-sky Astrophysics (AU)
- Instituto de Astrofísica de Andalucía (ES)
- Swinburne University of Technology (AU)
- University of Baltimore (US)
- The University of Texas at Austin (US)
- University of Edinburgh (GB)
Publication Details
- Journal
- Monthly Notices of the Royal Astronomical Society
- Published
- 2025-10-08
- DOI
- https://doi.org/10.1093/mnras/staf1723
- Citations
- 6
- Primary Topic
- Wastewater Treatment and Nitrogen Removal
- Type
- article
- Field-Weighted Citation Impact
- 3.02
Funders
- National Science Foundation
- U.S. Department of Defense
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Alfred P. Sloan Foundation
- Yale University
- Vanderbilt University
- Princeton University
- Ohio State University
- Harvard University
- University of Minnesota
- University of Washington
- Johns Hopkins University
- Carnegie Mellon University
- University of Portsmouth
- New Mexico State University
- Arizona Board of Regents
- Space Telescope Science Institute
- UK Research and Innovation
- European Space Agency
- York University
- European Southern Observatory
- Istituto Nazionale di Astrofisica
- Leibniz-Institut für Astrophysik Potsdam
- Office of Science
- College of Engineering, Michigan State University
- Leibniz-Gemeinschaft
- European Regional Development Fund
- Agencia Estatal de Investigación
- Brookhaven National Laboratory
- Lawrence Berkeley National Laboratory