REBELS-IFU: evidence for metal-rich massive galaxies at <i>z</i> ∼ 6−8

ABSTRACT Metallicity is a crucial tracer of galaxy evolution, providing insights into gas accretion, star formation, and feedback. At high redshift, these processes reveal how early galaxies assembled and enriched their interstellar medium. In this work, we present rest-frame optical spectroscopy of 12 massive ($\log (M_*/\mathrm{{\rm M}_{\odot }})&amp;gt;9$) galaxies at $z\sim 6$–8 from the Reionization Era Bright Emission Line Survey (REBELS) Atacama Large Millimetre/submillimetre Array (ALMA) large program, observed with the James Webb Space Telescope (JWST) NIRSpec integral field unit spectroscopy in the prism mode. These observations span emission lines from [O ii]$\lambda\lambda$3727,9 to [S ii]$\lambda\lambda$6716,31, providing key information on nebular dust attenuation, ionization states, and chemical abundances. We find lower O32 ratios (average $\sim 3.7$) and [O iii]$\lambda$5007 equivalent widths (median EW${_{[\mathrm{ O\,{{\small III}}]}}}\sim 480$ Å) than are generally found in existing large spectroscopic surveys at $z&amp;gt;6$, indicating less extreme ionizing conditions. Strong-line diagnostics suggest that these systems are some of the most metal-rich galaxies observed at $z&amp;gt;6$ (average $Z_{\mathrm{gas}}\sim 0.4 Z_{\odot }$), including sources with near-solar oxygen abundances, in line with their high stellar masses (average $\log {M_*/\mathrm{{\rm M}_{\odot }}}\sim 9.5$). Supplementing with literature sources at lower masses, we investigate the mass–metallicity and fundamental metallicity relations (MZR and FMR, respectively) over a 4 dex stellar mass range at $6&amp;lt; z&amp;lt; 8$. In contrast to recent studies of lower mass galaxies, we find no evidence for negative offsets to the $z=0$ FMR for the REBELS galaxies. This work demonstrates the existence of chemically enriched galaxies just $\sim 1$ Gyr after the big bang, and indicates that the MZR is already in place at these early times, in agreement with other recent $z&amp;gt;3$ studies.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-01-05
DOI
https://doi.org/10.1093/mnras/staf2023
Citations
3
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
71.48

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article

REBELS-IFU: evidence for metal-rich massive galaxies at z ∼ 6−8

A. Pallottini, Ilse De Looze, Jacqueline Hodge, Sander Schouws et al.
3 citations
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
71.48
article

REBELS-IFU: evidence for metal-rich massive galaxies at z ∼ 6−8

A. Pallottini, Ilse De Looze, Jacqueline Hodge, Sander Schouws, Nina S. Sartorio, Thomas Herard-Demanche, Marco Palla, Mauro Stefanon, Hanae Inami, A. Ferrara, R. J. Bouwens, Rebecca Fisher, Lucie E. Rowland, Hiddo Algera, Katherine Ormerod, R. A. A. Bowler, Pascal A. Oesch, A. Laza-Ramos, Valentino González, Manuel Aravena, Renske Smit, Laura Sommovigo, Ryan Endsley, K. E. Heintz, Karin Cescon, Luca Graziani, Themiya Nanayakkara, J. R. Weaver, P. Dayal, D. P. Stark, Cindy Gulis, Sune Toft, Ivana van Leeuwen, Yoshinobu Fudamoto
article en
3 citations

Abstract

ABSTRACT Metallicity is a crucial tracer of galaxy evolution, providing insights into gas accretion, star formation, and feedback. At high redshift, these processes reveal how early galaxies assembled and enriched their interstellar medium. In this work, we present rest-frame optical spectroscopy of 12 massive ($\log (M_*/\mathrm{{\rm M}_{\odot }})&amp;gt;9$) galaxies at $z\sim 6$–8 from the Reionization Era Bright Emission Line Survey (REBELS) Atacama Large Millimetre/submillimetre Array (ALMA) large program, observed with the James Webb Space Telescope (JWST) NIRSpec integral field unit spectroscopy in the prism mode. These observations span emission lines from [O ii]$\lambda\lambda$3727,9 to [S ii]$\lambda\lambda$6716,31, providing key information on nebular dust attenuation, ionization states, and chemical abundances. We find lower O32 ratios (average $\sim 3.7$) and [O iii]$\lambda$5007 equivalent widths (median EW${_{[\mathrm{ O\,{{\small III}}]}}}\sim 480$ Å) than are generally found in existing large spectroscopic surveys at $z&amp;gt;6$, indicating less extreme ionizing conditions. Strong-line diagnostics suggest that these systems are some of the most metal-rich galaxies observed at $z&amp;gt;6$ (average $Z_{\mathrm{gas}}\sim 0.4 Z_{\odot }$), including sources with near-solar oxygen abundances, in line with their high stellar masses (average $\log {M_*/\mathrm{{\rm M}_{\odot }}}\sim 9.5$). Supplementing with literature sources at lower masses, we investigate the mass–metallicity and fundamental metallicity relations (MZR and FMR, respectively) over a 4 dex stellar mass range at $6&amp;lt; z&amp;lt; 8$. In contrast to recent studies of lower mass galaxies, we find no evidence for negative offsets to the $z=0$ FMR for the REBELS galaxies. This work demonstrates the existence of chemically enriched galaxies just $\sim 1$ Gyr after the big bang, and indicates that the MZR is already in place at these early times, in agreement with other recent $z&amp;gt;3$ studies.

Monthly Notices of the Royal Astronomical SocietyVol. 546(2)
Universidad de Santiago de Chile (CL), Hiroshima University (JP), University of Geneva (CH), Leiden University (NL), University of Copenhagen (DK), Pennsylvania State University (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Scuola Normale Superiore (IT), Chiba University (JP), Universitat de València (ES), University of Groningen (NL), University of Toronto (CA), University of Massachusetts Amherst (US), Arcetri Astrophysical Observatory (IT), University of Manchester (GB), Ghent University (BE), Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IT), DAWN Center for Independent Living (US), Canadian Institute for Theoretical Astrophysics (CA), Instituto de Física de Cantabria (ES), Flatiron Health (United States) (US), Millenium Nucleus for Planet Formation (CL), Istituto Nazionale di Fisica Nucleare, Sezione di Roma I (IT), National Astronomical Observatory of Japan (JP), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT), Flatiron Institute (US), Swinburne University of Technology (AU), Liverpool John Moores University (GB), University of Chile (CL), Sapienza University of Rome (IT), The University of Texas at Austin (US), National Institute for Astrophysics (IT), Universidad Diego Portales (CL), University of Bologna (IT), University of California, Berkeley (US)
National Aeronautics and Space Administration, Space Telescope Science Institute, European Commission, Universiteit Leiden, Rijksuniversiteit Groningen, National Astronomical Observatory of Japan, Agencia Nacional de Investigación y Desarrollo, Horizon 2020 Framework Programme, Comisión Nacional de Investigación Científica y Tecnológica
Openalex Percentile: Top 0%
Galaxies: Formation, Evolution, Phenomena
71.48
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