A core in a star-forming disc as evidence of inside-out growth in the early Universe
William Baker, Sandro Tacchella, Benjamin D. Johnson, Erica J. Nelson, Katherine A. Suess, Francesco D’Eugenio, Mirko Curti, Anna de Graaff, Zhiyuan Ji, R. Maiolino, Brant Robertson, Jan Scholtz, Stacey Alberts, Santiago Arribas, Kristan Boyett, Andrew J. Bunker, Stefano Carniani, S. Charlot, Zuyi Chen, Jacopo Chevallard, Emma Curtis-Lake, A. Lola Danhaive, Christa DeCoursey, Eiichi Egami, Daniel J. Eisenstein, Ryan Endsley, Ryan Hausen, Jakob M. Helton, Nimisha Kumari, Tobias J. Looser, Michael V. Maseda, Dávid Puskás, Marcia Rieke, Lester Sandles, Fengwu Sun, Hannah Übler, Christina C. Williams, Christopher N. A. Willmer, Joris Witstok
Abstract
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 400 million solar masses consists of three components: a highly compact core with a half-light radius of less than 100 pc, an actively star-forming disc with a radius of about 400 pc and a star-forming clump, all of which show distinctive star-formation histories. The central stellar mass density of this galaxy is within a factor of 2 of the most massive present-day ellipticals, while being globally 1,000 times less massive. The radial profile of the specific star-formation rate is rising towards the outskirts. This evidence suggests a detection of the inside-out growth of a galaxy as a proto-bulge and a star-forming disc in the epoch of reionization.