The <i>JWST</i> EXCELS survey: too much, too young, too fast? Ultra-massive quiescent galaxies at 3 &amp;lt; z &amp;lt; 5

ABSTRACT We report ultra-deep, medium-resolution spectroscopic observations for four quiescent galaxies with log$_{10}(M_*/\mathrm{M_\odot })\gt 11$ at $3 \lt z \lt 5$. These data were obtained with JWST NIRSpec as part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey, which we introduce in this work. The first two galaxies are newly selected from PRIMER UDS imaging, both at $z=4.62$ and separated by 860 pkpc on the sky, within a larger structure for which we confirm several other members. Both formed at $z\simeq 8-10$. These systems could plausibly merge by the present day to produce a local massive elliptical galaxy. The other two ultra-massive quiescent galaxies are previously known at $z=3.99$ and 3.19, with the latter (ZF-UDS-7329) having been the subject of debate as potentially too old and too massive to be accommodated by the $\Lambda$-CDM halo-mass function. Both exhibit high stellar metallicities, and for ZF-UDS-7329 we are able to measure the $\alpha -$enhancement, obtaining [Mg/Fe] = $0.42^{+0.19}_{-0.17}$. We finally evaluate whether these four galaxies are consistent with the $\Lambda$-CDM halo-mass function using an extreme value statistics approach. We find that the $z=4.62$ objects and the $z=3.19$ object are unlikely within our area under the assumption of standard stellar fractions ($f_*\simeq 0.1-0.2$). However, these objects roughly align with the most massive galaxies expected under the assumption of 100 per cent conversion of baryons to stars ($f_*$=1). Our results suggest extreme galaxy formation physics during the first billion years, but no conflict with $\Lambda$-CDM cosmology.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-09-12
DOI
https://doi.org/10.1093/mnras/stae2092
Citations
97
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
32.16

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article

The JWST EXCELS survey: too much, too young, too fast? Ultra-massive quiescent galaxies at 3 &lt; z &lt; 5

Adam C. Carnall, M. L. Hamadouche, R Begley, G. D. Illingworth et al.
97 citations
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
32.16
article

The JWST EXCELS survey: too much, too young, too fast? Ultra-massive quiescent galaxies at 3 &lt; z &lt; 5

Adam C. Carnall, M. L. Hamadouche, R Begley, G. D. Illingworth, Laia Barrufet, Kate Rowlands, Karla Z. Arellano-Córdova, T M Stanton, Norman A. Grogin, J. S. Dunlop, O. Almaini, Callum T. Donnan, Anton M. Koekemoer, Pablo G. Pérez‐González, D J McLeod, Fergus Cullen, Christopher C. Lovell, Ho-Hin Leung, Alice E. Shapley, Richard S. Ellis, P. Santini, A. Cimatti, Vivienne Wild, R. J. McLure
article en
97 citations

Abstract

ABSTRACT We report ultra-deep, medium-resolution spectroscopic observations for four quiescent galaxies with log$_{10}(M_*/\mathrm{M_\odot })\gt 11$ at $3 \lt z \lt 5$. These data were obtained with JWST NIRSpec as part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey, which we introduce in this work. The first two galaxies are newly selected from PRIMER UDS imaging, both at $z=4.62$ and separated by 860 pkpc on the sky, within a larger structure for which we confirm several other members. Both formed at $z\simeq 8-10$. These systems could plausibly merge by the present day to produce a local massive elliptical galaxy. The other two ultra-massive quiescent galaxies are previously known at $z=3.99$ and 3.19, with the latter (ZF-UDS-7329) having been the subject of debate as potentially too old and too massive to be accommodated by the $\Lambda$-CDM halo-mass function. Both exhibit high stellar metallicities, and for ZF-UDS-7329 we are able to measure the $\alpha -$enhancement, obtaining [Mg/Fe] = $0.42^{+0.19}_{-0.17}$. We finally evaluate whether these four galaxies are consistent with the $\Lambda$-CDM halo-mass function using an extreme value statistics approach. We find that the $z=4.62$ objects and the $z=3.19$ object are unlikely within our area under the assumption of standard stellar fractions ($f_*\simeq 0.1-0.2$). However, these objects roughly align with the most massive galaxies expected under the assumption of 100 per cent conversion of baryons to stars ($f_*$=1). Our results suggest extreme galaxy formation physics during the first billion years, but no conflict with $\Lambda$-CDM cosmology.

Monthly Notices of the Royal Astronomical SocietyVol. 534(1)
Space Telescope Science Institute (US), University of Nottingham (GB), Johns Hopkins University (US), University of California, Los Angeles (US), University of St Andrews (GB), University of California, Santa Cruz (US), Astronomical Observatory of Rome (IT), Royal Observatory (GB), Scottish Universities Physics Alliance (GB), Centro de Astrobiología (ES), Osservatorio di Astrofisica e Scienza dello Spazio, University College London (GB), University of Portsmouth (GB), National Institute for Astrophysics (IT), University of Bologna (IT), University of Edinburgh (GB)
National Aeronautics and Space Administration, Space Telescope Science Institute, UK Research and Innovation, European Space Agency, Institut sur la Nutrition et les Aliments Fonctionnels, Canadian Space Agency, Science and Technology Facilities Council
Openalex Percentile: Top 0%
Galaxies: Formation, Evolution, Phenomena
32.16
DOIOpen Access PDFOpenAlex
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