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We spectroscopically confirm the M ₔₕ = -20. 5 mag galaxy GHZ2/GLASS-z12 to be at redshift z=12. 34. The source was selected via NIRCam photometry in GLASS-JWST Early Release Science data, providing the first evidence of a surprising abundance of bright galaxies at z 10. The NIRSpec PRISM spectrum is remarkable and unlike any local analog. It shows significant detections of N IV, C IV, He II, O III, C III, O II, and Ne III lines, and the first detection in a high-redshift object of the O III Bowen fluorescence line at 3133 rest-frame. The prominent C IV line with rest-frame equivalent width (EW) 46 puts GHZ2 in the category of extreme C IV emitters characterised by hard radiation fields. GHZ2 displays UV lines with EWs that are only found in active galactic nuclei (AGNs) or composite objects at low/intermediate redshifts, and UV line-intensity ratios that are compatible both with AGNs and star formation in a low-metallicity environment. The nondetection of the very high-ionization lines Ne IV and Ne V, and the remarkable similarity between GHZ2 and other known C IV emitters, favors a scenario in which the high ionizing output is due to very low metallicity, massive stars forming in a dense environment. We estimate a metallicity 0. 1 Z/ Z_, a high ionization parameter logU > -2, a N/O abundance 4--5 times the solar value, and a subsolar C/O ratio similar to the recently discovered class of nitrogen-enhanced objects at high redshift. Considering its abundance patterns and the high stellar mass density (10⁴ M_ pc^-2), GHZ2 is an ideal formation site for the progenitors of today's globular clusters. The remarkable brightness of GHZ2 makes it a "Rosetta stone" for understanding the physics of galaxy formation within just 360 Myr after the Big Bang.
Castellano et al. (Fri,) studied this question.