James Webb Space Telescope Feed Post

Arxiv: JWST NIRSpec Spectroscopy of the Remarkable Bright Galaxy GHZ2/GLASS-z12 at Redshift 12.34 Published: 3/15/2024 2:12:44 PM Updated: 7/3/2024 1:19:19 PM

Paper abstract: We spectroscopically confirm the M_{\rm UV} = -20.5 mag galaxyGHZ2/GLASS-z12 to be at redshift z=12.34. The source was selected via NIRCamphotometry in GLASS-JWST ERS data, providing the first evidence of a surprisingabundance of bright galaxies at z \gtrsim 10. The NIRSpec PRISM spectrumshows 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 lineat 3133 {\AA} rest-frame. The prominent C IV line with rest-frame equivalentwidth (EW) ~ 46 {\AA} puts GHZ2 in the category of extreme C IVemitters. GHZ2 displays UV lines with EWs that are only found in activegalactic nuclei (AGNs) or composite objects at low/intermediate redshifts. TheUV line-intensity ratios are compatible both with AGNs and star formation in alow-metallicity environment, with the low limit on the [Ne IV]/[N IV] ratiofavoring a stellar origin of the ionizing photons. We discuss a possiblescenario in which the high ionizing output is due to low metallicity starsforming in a dense environment. We estimate a metallicity <~ 0.1 Z/{\rmZ}_{\odot}, a high ionization parameter logU > -2, a N/O abundance 4--5times the solar value, and a subsolar C/O ratio similar to the recentlydiscovered class of nitrogen-enhanced objects. Considering its abundancepatterns and the high stellar mass density (10^4~M_{\odot}~pc^{-2}), GHZ2is an ideal formation site for the progenitors of today's globular clusters.The remarkable brightness of GHZ2 makes it a ``Rosetta stone'' forunderstanding the physics of galaxy formation within just 360 Myr after the BigBang.