[News] Impossible ? James Webb découvre du carbone dans l'Univers primitif
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[News] Impossible ? James Webb découvre du carbone dans l'Univers primitif
Le Télescope Spatial James Webb (JWST) bouleverse notre compréhension de l'évolution chimique de l'Univers en détectant un élément clé pour la vie dans les premiers âges de l'Univers. Cette découverte promet de réécrire les théories sur la formation des premières galaxies et la création des éléments.
Les connaissances actuelles sur la formation des métaux dans l'Univers reposent sur l'idée que les éléments plus lourds que l'hydrogène et l'hélium, appelés métaux par l...
Re: [News] Impossible ? James Webb découvre du carbone dans l'Univers primitif
Pour ceux qui sont intéressés, l'article (pdf en anglais) : https://arxiv.org/pdf/2311.09908
Et la synthèse / executive summary :
Finding the emergence of the first generation of metals in the early Universe, and identifying their origin, are some of the most important goals of modern astrophysics. We present deep JWST/NIRSpec spectroscopy of GS-z12, a galaxy at z=12.5, in which we report the detection of C iii]λλ1907,1909 nebular emission. This is the most distant detection of a metal transition and the most distant redshift determination via emission lines. In addition, we report tentative detections of [O ii]λλ3726,3729 and [Ne iii]λ3869, and possibly O iii]λλ1661,1666. By using the accurate redshift from C iii], we can model the Lyα drop to reliably measure an absorbing column density of hydrogen of NHi ≈ 10^22 cm−2 – too high for an IGM origin and implying abundant ISM in GS-z12 or CGM around it. We infer a lower limit for the neutral gas mass of about 10^7 M⊙ which, compared with a stellar mass of ∼ 4 × 10^7 M⊙ inferred from the continuum fitting, implies a gas fraction higher than about 0.1–0.5. We derive a solar or even super-solar carbon-to-oxygen ratio, tentatively [C/O] > 0.15. This is higher than the C/O measured in galaxies discovered by JWST at z = 6–9, and higher than the C/O arising from Type-II supernovae enrichment, while AGB stars cannot contribute to carbon enrichment at these early epochs and low metallicities. Such a high C/O in a galaxy observed 350 Myr after the Big Bang may be explained by the yields of extremely metal poor stars, and may even be the heritage of the first generation of supernovae from Population III progenitors.
Et la synthèse / executive summary :
Finding the emergence of the first generation of metals in the early Universe, and identifying their origin, are some of the most important goals of modern astrophysics. We present deep JWST/NIRSpec spectroscopy of GS-z12, a galaxy at z=12.5, in which we report the detection of C iii]λλ1907,1909 nebular emission. This is the most distant detection of a metal transition and the most distant redshift determination via emission lines. In addition, we report tentative detections of [O ii]λλ3726,3729 and [Ne iii]λ3869, and possibly O iii]λλ1661,1666. By using the accurate redshift from C iii], we can model the Lyα drop to reliably measure an absorbing column density of hydrogen of NHi ≈ 10^22 cm−2 – too high for an IGM origin and implying abundant ISM in GS-z12 or CGM around it. We infer a lower limit for the neutral gas mass of about 10^7 M⊙ which, compared with a stellar mass of ∼ 4 × 10^7 M⊙ inferred from the continuum fitting, implies a gas fraction higher than about 0.1–0.5. We derive a solar or even super-solar carbon-to-oxygen ratio, tentatively [C/O] > 0.15. This is higher than the C/O measured in galaxies discovered by JWST at z = 6–9, and higher than the C/O arising from Type-II supernovae enrichment, while AGB stars cannot contribute to carbon enrichment at these early epochs and low metallicities. Such a high C/O in a galaxy observed 350 Myr after the Big Bang may be explained by the yields of extremely metal poor stars, and may even be the heritage of the first generation of supernovae from Population III progenitors.