The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z~8

Mirko Curti (1, 2) , Francesco d'Eugenio (1, 2) , Stefano Carniani (3) , Roberto Maiolino (1, 2, 4) , Lester Sandles (1, 2) , Joris Witstok (1, 2) , William M Baker (1, 2) , Jake S. Bennett (1, 5) , Monika Joanna Piotrowska (1, 2) , Sandro Tacchella (1, 2) , Stephane Charlot (6) , Kimihiko Nakajima (7) , Gabriel Maheson (1, 2) , Filippo Mannucci (8) , Amirnezam Amiri (9, 8) , Santiago Arribas (10) , Francesco Belfiore (8) , Nina R. Bonaventura (11, 12) , Andrew J. Bunker (13) , Jacopo Chevallard (13) , Giovanni Cresci (8) , Emma Curtis-Lake (14) , Connor Hayden-Pawson (1, 2) , Gareth C Jones (13) , Nimisha Kumari (15) , Isaac Laseter (16) , Tobias J. Looser (1, 2) , Alessandro Marconi (9, 8) , Michael V. Maseda (16) , Jan Scholtz (1, 2) , Renske Smit (17) , Hannah Übler (1, 2) , Imaan E. B. Wallace (13)

1 KICC - Kavli Institute for Cosmology [Cambridge]
2 Cavendish Laboratory
3 SNS - Scuola Normale Superiore di Pisa
4 Department of Physics and Astronomy [UCL London]
5 Institute of Astronomy [Cambridge]
6 IAP - Institut d'Astrophysique de Paris
7 NAOJ - National Astronomical Observatory of Japan
8 OAA - INAF - Osservatorio Astrofisico di Arcetri
9 Dipartimento di Fisica e Astronomia [Firenze]
10 CAB - Centro de Astrobiologia [Madrid]
11 Cosmic Dawn Center (DAWN)
12 NBI - Niels Bohr Institute [Copenhagen]
13 Department of Physics [Oxford]
14 Centre for Astrophysics Research [Hatfield]
15 STSci - Space Telescope Science Institute
16 Department of Astronomy [Madison]
17 ARI - Astrophysics Research Institute [Liverpool]

We analyse the chemical properties of three z∼ 8 galaxies behind the galaxy cluster SMACS J0723.3-7327, observed as part of the Early Release Observations programme of the James Webb Space Telescope (JWST). Exploiting [O iii]λ4363 auroral line detections in NIRSpec spectra, we robustly apply the direct Te method for the very first time at such high redshift, measuring metallicities ranging from extremely metal poor (12+log(O/H)≈ 7) to about one-third solar. We also discuss the excitation properties of these sources, and compare them with local strong-line metallicity calibrations. We find that none of the considered diagnostics match simultaneously the observed relations between metallicity and strong-line ratios for the three sources, implying that a proper re-assessment of the calibrations may be needed at these redshifts. On the mass-metallicity plane, the two galaxies at z ∼ 7.6 (⁠log(M∗/M⊙)=8.1,8.7⁠) have metallicities that are consistent with the extrapolation of the mass-metallicity relation at z∼2-3, while the least massive galaxy at z ∼ 8.5 (⁠log(M∗/M⊙)=7.8⁠) shows instead a significantly lower metallicity . The three galaxies show different level of offset relative to the Fundamental Metallicity Relation, with two of them (at z∼ 7.6) being marginally consistent, while the z∼ 8.5 source deviating significantly, being probably far from the smooth equilibrium between gas flows, star formation and metal enrichment in place at later epochs.

Mots clés: Galaxies: ISM; Galaxies: evolution; Galaxies: general; Galaxies: abundances

Domaines: Physique [physics]; Astrophysique [astro-ph]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]

Mirko Curti, Francesco d'Eugenio, Stefano Carniani, Roberto Maiolino, Lester Sandles, et al.. The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z~8. Monthly Notices of the Royal Astronomical Society, 2023, 518, pp.425-438. ⟨10.1093/mnras/stac2737⟩. ⟨hal-03839214⟩