The Extreme Low-mass End of the Mass–Metallicity Relation at z ∼ 7

Iryna Chemerynska; Hakim Atek; Pratika Dayal; Lukas J. Furtak; Robert Feldmann; Jenny E. Greene; Michael V. Maseda; Themiya Nanayakkara; Pascal A. Oesch; Seiji Fujimoto; Ivo Labbé; Rachel Bezanson; Gabriel Brammer; Sam E. Cutler; Joel Leja; Richard Pan; Sedona H. Price; Bingjie Wang; John R. Weaver; Katherine E. Whitaker

doi:10.3847/2041-8213/ad8dc9

The Astrophysical Journal Letters (Jan 2024)

The Extreme Low-mass End of the Mass–Metallicity Relation at z ∼ 7

Iryna Chemerynska,
Hakim Atek,
Pratika Dayal,
Lukas J. Furtak,
Robert Feldmann,
Jenny E. Greene,
Michael V. Maseda,
Themiya Nanayakkara,
Pascal A. Oesch,
Seiji Fujimoto,
Ivo Labbé,
Rachel Bezanson,
Gabriel Brammer,
Sam E. Cutler,
Joel Leja,
Richard Pan,
Sedona H. Price,
Bingjie Wang,
John R. Weaver,
Katherine E. Whitaker

Affiliations

Iryna Chemerynska: ORCiD; Institut d’Astrophysique de Paris, CNRS, Sorbonne Université , 98bis Boulevard Arago, 75014, Paris, France ; [email protected]
Hakim Atek: ORCiD; Institut d’Astrophysique de Paris, CNRS, Sorbonne Université , 98bis Boulevard Arago, 75014, Paris, France ; [email protected]
Pratika Dayal: ORCiD; Kapteyn Astronomical Institute, University of Groningen , 9700 AV Groningen, The Netherlands
Lukas J. Furtak: ORCiD; Department of Physics, Ben-Gurion University of the Negev , P.O. Box 653, Be’er-Sheva 84105, Israel
Robert Feldmann: ORCiD; Department of Astrophysics, University of Zurich , Zurich, CH-8057, Switzerland
Jenny E. Greene: ORCiD; Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA
Michael V. Maseda: ORCiD; Department of Astronomy, University of Wisconsin–Madison , 475 North Charter Street, Madison, WI 53706, USA
Themiya Nanayakkara: ORCiD; Centre for Astrophysics and Supercomputing, Swinburne University of Technology , PO Box 218, Hawthorn, VIC 3122, Australia
Pascal A. Oesch: ORCiD; Department of Astronomy, University of Geneva , Chemin Pegasi 51, 1290 Versoix, Switzerland; Cosmic Dawn Center (DAWN) , Copenhagen, Denmark
Seiji Fujimoto: ORCiD; Department of Astronomy, The University of Texas at Austin , Austin, TX, USA
Ivo Labbé: ORCiD; Centre for Astrophysics and Supercomputing, Swinburne University of Technology , Melbourne, VIC 3122, Australia
Rachel Bezanson: ORCiD; Department of Physics and Astronomy and PITT PACC, University of Pittsburgh , Pittsburgh, PA 15260, USA
Gabriel Brammer: ORCiD; Cosmic Dawn Center (DAWN) , Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, Copenhagen, Denmark
Sam E. Cutler: ORCiD; Department of Astronomy, University of Massachusetts , Amherst, MA 01003, USA
Joel Leja: ORCiD; Department of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Computational & Data Sciences, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Gravitation and the Cosmos, The Pennsylvania State University , University Park, PA 16802, USA
Richard Pan: ORCiD; Department of Physics and Astronomy, Tufts University , 574 Boston Avenue, Medford, MA 02155, USA
Sedona H. Price: ORCiD; Department of Physics and Astronomy and PITT PACC, University of Pittsburgh , Pittsburgh, PA 15260, USA
Bingjie Wang: ORCiD; Department of Astronomy & Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Computational & Data Sciences, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Gravitation and the Cosmos, The Pennsylvania State University , University Park, PA 16802, USA
John R. Weaver: ORCiD; Department of Astronomy, University of Massachusetts , Amherst, MA 01003, USA
Katherine E. Whitaker: ORCiD; Department of Astronomy, University of Massachusetts , Amherst, MA 01003, USA; Cosmic Dawn Center (DAWN) , Denmark

DOI: https://doi.org/10.3847/2041-8213/ad8dc9
Journal volume & issue: Vol. 976, no. 1
p. L15

Abstract

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The mass–metallicity relation provides crucial insights into the baryon cycle in galaxies and strong constraints on galaxy formation models. We use JWST NIRSpec observations from the UNCOVER program to measure the gas-phase metallicity in a sample of eight galaxies during the epoch of reionization at z = 6–8. Thanks to the strong lensing of the galaxy cluster Abell 2744, we are able to probe extremely low stellar masses between 10 ^6 and 10 ^8 M _⊙ . Using strong-line diagnostics and the most recent JWST calibrations, we derive extremely low oxygen abundances in the range of 12 + log(O/H) = 6.7–7.8. By combining this sample with more massive galaxies at similar redshifts, we derive a best-fit relation of 12 + log(O/H) = $-{0.076}_{-0.03}^{+0.03}\times {(\mathrm{log}({M}_{\star }))}^{2}+{1.61}_{-0.52}^{+0.52}$ × $\mathrm{log}({M}_{\star })-{0.26}_{-0.10}^{+0.10}$ , which becomes steeper than determinations at z ∼ 3–6 toward low-mass galaxies. Our results show a clear redshift evolution in the overall normalization of the relation, galaxies at higher redshift having significantly lower metallicities at a given mass. A comparison with theoretical models provides important constraints on which physical processes, such as metal mixing, star formation or feedback recipes, are important in reproducing the observations. Additionally, these galaxies exhibit star formation rates that are higher by a factor of a few to tens compared to extrapolated relations at similar redshifts or theoretical predictions of main-sequence galaxies, pointing to a recent burst of star formation. All these observations are indicative of the highly stochastic star formation and interstellar medium enrichment expected in these low-mass systems, suggesting that feedback mechanisms in high- z dwarf galaxies might be different from those in place at higher masses.

Published in The Astrophysical Journal Letters

ISSN: 2041-8205 (Print); 2041-8213 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/2041-8205

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