James Webb Space Telescope Feed Post

JADES: Carbon enrichment 350 Myr after the Big Bang in a gas-rich galaxy | GS-z12

Panel a; false-colour RGB image, highlighting the position of the NIRSpec/MSA shutters in PID 3215. The asterisk indicates the position of an interloper with low surface brightness, which was removed in the data reduction. Panel b; 2-d S/N map, showing the three central shutters (the asterisk is the position of the interloper). Panel c; 1-d boxcar-extracted prism spectrum, combining 3215 and 1210; the vertical dashed lines marking the position of strong emission lines at z = 12.48. Panels d–f; combined 3215 and 1210 data and model spectrum around the O iii], C iii], [O ii] and [Ne iii] lines, for the prism (panels d and e) and for the G395M grating (only 3215; panel f). Ciii] is detected at the 5-s level (7-s with the bootstrapping method). O iii] is not robustly detected (2.3- s significance); [O ii] and [Ne iii] are marginally detected only in the prism (4- and 3.5-s) but not in the grating, despite comparable sensitivity. The vertical dashed lines mark the wavelength of the emission lines at the redshift of the object, with the shaded region indicating the redshift uncertainty. Abstract: 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]??1907,1909 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]??3726,3729 and [Ne III]?3869, and possibly O III]??1661,1666. By using the accurate redshift from C III], we can model the Lya drop to reliably measure an absorbing column density of hydrogen of NHI˜1022 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 107 MSun which, compared with a stellar mass of ˜4×107 MSun 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.