RUBIES Reveals a Massive Quiescent Galaxy at <i>z</i>=7.3

Andrea Weibel, Anna de Graaff, David J. Setton, Tim B. Miller, Pascal A. Oesch, Gabriel Brammer, Claudia D. P. Lagos, Katherine E. Whitaker, Christina C. Williams, Josephine F. W. Baggen, Rachel Bezanson, Leindert A. Boogaard, Nikko J. Cleri, Jenny E. Greene, Michaela Hirschmann, Raphael E. Hviding, Adarsh Kuruvanthodi, Ivo Labbe, Joel Leja, Michael V. MasedaJorryt Matthee, Ian McConachie, Rohan P. Naidu, Guido Roberts-Borsani, Daniel Schaerer, Katherine A. Suess, Francesco Valentino, Pieter van Dokkum, Bingjie Wang

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21 Citations (Web of Science)

Abstract

We report the spectroscopic discovery of a massive quiescent galaxy at z(spec) = 7.29 +/- 0.01, just similar to 700 Myr after the big bang. RUBIES-UDS-QG-z7 was selected from public JWST/NIRCam and MIRI imaging from the PRIMER survey and observed with JWST/NIRSpec as part of RUBIES. The NIRSpec/PRISM spectrum reveals one of the strongest Balmer breaks observed thus far at z > 6, with no emission lines but tentative Balmer and Ca absorption features, as well as a Lyman break. Simultaneous modeling of the NIRSpec/PRISM spectrum and NIRCam and MIRI photometry (spanning 0.9-18 mu m) shows that the galaxy formed a stellar mass of log(M & lowast;/M-circle dot)=10.23(-0.04)(+0.04 )before z similar to 8 and ceased forming stars 50-100 Myr prior to the time of observation, resulting in log(sSFR/Gyr-1)<-1. We measure a small physical size of 209(-24)(+33)pc, which implies a high stellar-mass surface density within the effective radius of log(Sigma & lowast;,e/M(circle dot)kpc-2)=10.85(-0.12)(+0.11), comparable to the highest densities measured in quiescent galaxies at z similar to 2-5. The 3D stellar-mass density profile of RUBIES-UDS-QG-z7 is remarkably similar to the central densities of local massive ellipticals, suggesting that at least some of their cores may have already been in place at z > 7. The discovery of RUBIES-UDS-QG-z7 has strong implications for galaxy formation models: the estimated number density of quiescent galaxies at z similar to 7 is >100 <bold>x</bold> larger than predicted from any model to date, indicating that quiescent galaxies have formed earlier than previously expected
Original languageEnglish
Article number11
Number of pages16
JournalAstrophysical Journal
Volume983
Issue number1
DOIs
Publication statusPublished - 10 Apr 2025

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