# Inside-out growth in the early Universe: a core in a vigorously star-forming disc

**Authors:** William M. Baker, Sandro Tacchella, Benjamin D. Johnson, Erica Nelson, Katherine A. Suess, Francesco D'Eugenio, Mirko Curti, Anna de Graaff, Zhiyuan Ji, Roberto Maiolino, Brant Robertson, Jan Scholtz, Stacey Alberts, Santiago Arribas, Kristan Boyett, Andrew J. Bunker, Stefano Carniani, Stephane Charlot, Zuyi Chen, Jacopo Chevallard  
**arXiv:** [2306.02472](https://arxiv.org/abs/2306.02472)  
**Date:** 2023-06-04  
**Summary page:** https://www.summarizepaper.com/fr/paper/2306.02472v1/

## Abstract

The physical processes that establish the morphological evolution and the structural diversity of galaxies are key unknowns in extragalactic astrophysics. Here we report the finding of the morphologically-mature galaxy JADES-GS+53.18343-27.79097, which existed within the first 700 million years of the Universe's history. This star-forming galaxy with a stellar mass of $10^{8.6}$ solar masses consists of three components, a highly-compact core with a half-light radius of 144 pc, a strongly star-forming disc with a radius of 468 pc, and a star-forming clump, which all show distinctive star-formation histories. The central stellar mass density of this galaxy is within a factor of two of the most massive present-day ellipticals, while being globally 1000 times less massive. The radial profile of the specific star-formation rate is strongly rising toward the outskirts. This evidence strongly suggests the first detection of inside-out growth of a galaxy as a proto-bulge and a star-forming disc in the Epoch of Reionization.