A Cosmic Miracle: A Remarkably Luminous Galaxy at $z_{\mathrm{spec}}=14.44$ Confirmed with JWST

Abstract

JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, $z>10$, where few such sources were expected. Here we present the most distant example of this class yet -- MoM-z14, a luminous ($M_{\mathrm{UV}}=-20.2$) source in the COSMOS field at $z_{\mathrm{spec}}=14.44_{-0.02}^{+0.02}$ that expands the observational frontier to a mere 280 million years after the Big Bang. The redshift is confirmed with NIRSpec/PRISM spectroscopy through a sharp Lyman-$\alpha$ break and $\sim 3\sigma$ detections of five rest-UV emission lines. The number density of bright $z_{\mathrm{spec}}\sim 14-15$ sources implied by our "Mirage or Miracle" survey spanning $\sim 350$ arcmin${}^2$ is $>100\times$ larger ($182_{-105}^{+329}\times$) than pre-JWST consensus models. The high EWs of UV lines ($\sim 15-35$ Å) signal a rising star-formation history, with a $\sim 10\times$ increase in the last 5 Myr ($\mathrm{SF}{\mathrm{R}}_{5Myr}/\mathrm{SF}{\mathrm{R}}_{50Myr}=9.9_{-5.8}^{+3.0}$). The source is extremely compact (circularized $r_{\mathrm{e}}=74_{-12}^{+15}$ pc), and yet elongated ($b/a=0.25_{-0.06}^{+0.11}$), suggesting an AGN is not the dominant source of UV light. The steep UV slope ($\beta =-2.5_{-0.2}^{+0.2}$) implies negligible dust attenuation and a young stellar population. The absence of a strong damping wing provides tentative evidence that the immediate surroundings of MoM-z14 may be partially ionized at a redshift where virtually every reionization model predicts a $\sim 100\%$ neutral fraction. The nitrogen emission and highly super-solar [N/C]$>1$ hint at an abundance pattern similar to local globular clusters that may have once hosted luminous supermassive stars. Since this abundance pattern is also common among the most ancient stars born in the Milky Way, we may be directly witnessing the formation of such stars in dense clusters, connecting galaxy evolution across the entire sweep of cosmic time.

Published in the Open Journal of Astrophysics

Cited by in corpus (5)

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• Exploring Spatially-Resolved Metallicities, Dynamics and Outflows in Low-Mass Galaxies at $z\sim 7.6$
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• Back to basics: Little Red Dots as galaxies and dust-obscured AGNs in a synthetic NIRCam sky simulated with L-GalaxiesBH
• On the connection between nitrogen-enhanced field stars and the Galactic globular clusters