Forrest, BenAnnunziatella, MariannaWilson, GillianMarchesini, DaniloMuzzin, AdamCooper, M.CMarsan, CemileMcConachie, IanC. C. Chan, JeffreyGomez, PercyKado-Fong, ErinLa Barbera, FrancescoLabbé, IvoDaniel, Langle -VagleJulie, NantaisNonino, MarioPeña, TheodoreSaracco, PaoloMauro, StefanonRemco van der Burg, F.J2021-09-202021-09-202020-02Astrophysical Journal Letters Open Access Volume 890, Issue 110 February 2020 Article number L120418205http://repositorio.unab.cl/xmlui/handle/ria/20308We present spectra of the most massive quiescent galaxy yet spectroscopically confirmed at z > 3, verified via the detection of Balmer absorption features in the H- A nd K-bands of Keck/MOSFIRE. The spectra confirm a galaxy with no significant ongoing star formation, consistent with the lack of rest-frame UV flux and overall photometric spectral energy distribution. With a stellar mass of 3.1-0.2-+0.1× 10-11\,M at z = 3.493, this galaxy is nearly three times more massive than the highest redshift spectroscopically confirmed absorption-line-identified galaxy known. The star formation history of this quiescent galaxy implies that it formed >1000 M o yr-1 for almost 0.5 Gyr beginning at z ∼ 7.2, strongly suggestive that it is the descendant of massive dusty star-forming galaxies at 5 < z < 7 recently observed with ALMA. While galaxies with similarly extreme stellar masses are reproduced in some simulations at early times, such a lack of ongoing star formation is not seen there. This suggests the need for a quenching process that either starts earlier or is more rapid than that currently prescribed, challenging our current understanding of how ultra-massive galaxies form and evolve in the early universe. © 2020. The American Astronomical Society. All rights reserved.enArtículo