Journal Article

JWST NIRSpec Spectroscopy of the Remarkable Bright Galaxy GHZ2/GLASS-z12 at Redshift 12.34

Bakx, Tom J. L. C, Glazebrook, Karl, Filippenko, Alexei V, Wang, Xin, Napolitano, Lorenzo, Grillo, Claudio, Mascia, Sara, Dickinson, Mark, Calabrò, Antonello, Roberts-Borsani, Guido, Treu, Tommaso, Cupani, Guido, Fontana, Adriano, Merlin, Emiliano, Vanzella, Eros, Malkan, Matthew A, Castellano, Marco, Kelly, Patrick L, Sani, Eleonora, Santini, Paola, Rosati, Piero, Bergamini, Pietro, Mason, Charlotte A, Morishita, Takahiro, Llerena, Mario, Yoon, Ilsang, Pentericci, Laura, Zavala, Jorge A, Arrabal Haro, Pablo, Paris, Diego, Nanayakkara, Themiya

2024

Overview

We spectroscopically confirm the M UV = −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 shows detections of N iv, C iv, He ii, O iii, C iii, O ii, and Ne iii lines and the first detection at high redshift of the O iii Bowen fluorescence line at 3133 Å rest frame. The prominent C iv line with rest-frame equivalent width (EW) ≈ 46 Å puts GHZ2 in the category of extreme C iv emitters. GHZ2 displays UV lines with EWs that are only found in active galactic nuclei (AGNs) or composite objects at low/intermediate redshifts. The UV line-intensity ratios are compatible with both AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne iv]/[N iv] ratio favoring a stellar origin of the ionizing photons. We discuss a possible scenario in which the high ionizing output is due to low-metallicity stars forming in a dense environment. We estimate a metallicity ≲0.1 Z/Z ⊙, a high ionization parameter log U > −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. 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.

• Publisher: IOP Publishing
• Subject: Abundance / Active galactic nuclei / Emitters / Galactic evolution / Galaxies / Globular clusters / Ionization / James Webb Space Telescope / Metallicity / Nitrogen / Red shift / Spectroscopy / Star & galaxy formation / Star formation / Stellar mass