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arXiv · 2506.22540

A systematic search for dormant galaxies at z~5-7 from the JWST NIRSpec archive

Alba Covelo-Paz·Corentin Meuwly·Pascal A. Oesch·Callum Witten·Andrea Weibel·Cristian Carvajal-Bohorquez·Laure Ciesla·Emma Giovinazzo·Gabriel Brammer
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Abstract

JWST has revealed a population of ``dormant'' galaxies at $z>5$ that have recently halted their star formation and are characterized by weak emission lines and significant Balmer breaks. Until now, only four such galaxies have been reported at $z>5$, three with low stellar masses, $M_*<10^9M_\odot$ (so-called mini-quenched galaxies), and one massive quiescent galaxy with $M_*=10^{10.2}M_\odot$; no such galaxy had been reported at intermediate masses. Here, we present a systematic search for dormant galaxies at $5 1.4$). We find 14 dormant galaxies with stellar masses ranging from $10^{7.6}-10^{10.5}$, revealing an intermediate-mass population. By construction, these 14 sources are located about 1 dex below the star-forming main sequence. Their star formation histories suggest that they halted star formation between 10 and 25 Myr before the time of observation which, according to models, is comparable with the timescales of internally regulated bursts driving a ``breathing'' mode of star formation. Our results show that $\sim1\%$ of the galaxies in the DJA are in a dormant phase of their star formation histories, and they span a wide stellar mass range. These galaxies can be empirically selected using only their spectral features in NIRSpec prism data.

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Alba Covelo-Paz, Corentin Meuwly, Pascal A. Oesch, Callum Witten, Andrea Weibel, Cristian Carvajal-Bohorquez, Laure Ciesla, Emma Giovinazzo, Gabriel Brammer. 2025-06-27. A systematic search for dormant galaxies at z~5-7 from the JWST NIRSpec archive. https://doi.org/10.1051/0004-6361%2F202556119

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