Spectroscopic confirmation of two luminous galaxies at $z\sim14$

TL;DR

This paper reports spectroscopic confirmation of two extremely luminous galaxies at redshifts around 14, demonstrating that such galaxies existed just 300 million years after the Big Bang and challenging existing galaxy formation models.

Contribution

First spectroscopic confirmation of luminous galaxies at z~14, providing direct evidence of early galaxy formation and their properties, which were previously uncertain.

Findings

Galaxies at z~14 confirmed spectroscopically.

Both galaxies are dominated by stellar continuum emission.

Luminous galaxies are more common at high redshift than expected.

Abstract

The first observations of JWST have revolutionized our understanding of the Universe by identifying for the first time galaxies at $z\sim13$. In addition, the discovery of many luminous galaxies at Cosmic Dawn ($z>10$) has suggested that galaxies developed rapidly, in apparent tension with many standard models. However, most of these galaxies lack spectroscopic confirmation, so their distances and properties are uncertain. We present JADES JWST/NIRSpec spectroscopic confirmation of two luminous galaxies at redshifts of $z=14.32^{+0.08}_{-0.20}$ and $z=13.90\pm0.17$. The spectra reveal ultraviolet continua with prominent Lyman-$\alpha$ breaks but no detected emission lines. This discovery proves that luminous galaxies were already in place 300~million years after the Big Bang and are more common than what was expected before JWST. The most distant of the two galaxies is unexpectedly luminous and is spatially resolved with a radius of 260 parsecs. Considering also the very steep ultraviolet slope of the second galaxy, we conclude that both are dominated by stellar continuum emission, showing that the excess of luminous galaxies in the early Universe cannot be entirely explained by accretion onto black holes. Galaxy formation models will need to address the existence of such large and luminous galaxies so early in cosmic history.