JADES: Carbon-enhanced, Nitrogen-normal compact galaxy at z=11.2
J. Scholtz, M. S. Silcock, E. Curtis-Lake, R. Maiolino, S. Carniani, F. D'Eugenio, X. Ji, P. Jakobsen, K. Hainline, S. Arribas, W. M. Baker, R. Bhatawdekar, A. J. Bunker, S. Charlot, J. Chevallard, M. Curti, Daniel J. Eisenstein, Y. Isobe, G. C. Jones, E. Parlanti, P. G. Pérez-González, P. Rinaldi, B. Robertson, S. Tacchella, H. Übler, C. C. Williams, C. Willott, J. Witstok
TL;DR
This study presents deep JWST/NIRSpec observations of GS-z11-1 at $z\approx11.28$, detecting multiple rest-frame UV–optical emission lines that enable a detailed assessment of metallicity, C/O abundance, ionisation, and dynamics in an early-Universe galaxy. Through emission-line fitting and Beagle/beagle-agn SED modeling, the authors find low metallicity ($\sim$5–20% $Z_\odot$), high ionisation parameter, and a carbon-enhanced ISM, with beagle-agn scenarios allowing a possible AGN contribution but SF-dominated interpretations remaining viable. The galaxy is extremely compact ($r_{\rm half}\approx73$ pc) and shows a steep UV slope ($\beta_{UV}\approx-2.8$), suggesting a high escape fraction and potential signatures of early chemical enrichment prior to second-generation globular-cluster stars. Dynamical mass estimates ($\log M_{\rm dyn}/M_\odot\approx9.0$) imply a substantial gas/dark-matter reservoir relative to the stellar mass, highlighting GS-z11-1 as a key laboratory for studying the first steps of galaxy assembly and chemical evolution. Overall, the work demonstrates the power of JWST in characterizing the ISM and enrichment pathways of galaxies during the epoch of reionization, with implications for Pop II/III enrichment and proto-globular cluster formation.
Abstract
Over the past few years \textit{JWST} has been a major workhorse in detecting and constraining the metal enrichment of the first galaxies in the early Universe and finding the source of the ionisation of their interstellar medium. In this work, we present new deep JWST/NIRSpec spectroscopy of GS-z11-1, a galaxy at z = 11.28, in which we report the detection of multiple rest-frame UV and optical emission lines: CIII]$λλ$1907,09, CIV]$λλ$1548,51, [OII]$λλ$3726,29, [NeIII]$λ$3869, H$γ$ and tentative evidence for HeII$λ$1640. The ionisation properties of GS-z11-1 are consistent with star formation, with potential contribution from an active galactic nucleus (AGN). We estimate a galaxy stellar mass of log(M$_{*}$/M$_{\odot}$) = 7.8$\pm$0.2 and log(SFR/(M$_{\odot}$ yr$^{-1}$))= 0.32$\pm$0.11 for the fiducial SF-only models. We measured C/O from the SED modelling of C/O = 1.20$\pm0.15 \times$ solar. This is one of the highest C/O abundances at z$>$10, and it is consistent with either PopII and PopIII enrichment paths. Despite this source being extremely compact, with a half-light radius of 73$\pm$10 pc, we see no increased equivalent width of NIV] and NIII] emission lines as seen in some other compact sources at similar redshifts, a potential signature of second-generation stars in GCs. Overall, this galaxy exhibits low metallicity and high ionisation parameter consistent with intense star-formation or AGN activity in the early Universe, possibly observed before the enrichment by the second generation of stars in proto-globular clusters in the core of the galaxy.