The BoRG-$JWST$ Survey: Analogs at $z\sim8$ to the UV-luminous Galaxy Population at $z\gtrsim10$

Fuente: arXiv
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Autori principali: Rojas-Ruiz, Sofía, Roberts-Borsani, Guido, Morishita, Takahiro, Calabrò, Antonello, Bagley, Micaela B., Treu, Tommaso, Finkelstein, Steven L., Stiavelli, Massimo, Trenti, Michele, Yung, L. Y. Aaron
Natura: Preprint
Pubblicazione: 2025
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author Rojas-Ruiz, Sofía
Roberts-Borsani, Guido
Morishita, Takahiro
Calabrò, Antonello
Bagley, Micaela B.
Treu, Tommaso
Finkelstein, Steven L.
Stiavelli, Massimo
Trenti, Michele
Yung, L. Y. Aaron
author_facet Rojas-Ruiz, Sofía
Roberts-Borsani, Guido
Morishita, Takahiro
Calabrò, Antonello
Bagley, Micaela B.
Treu, Tommaso
Finkelstein, Steven L.
Stiavelli, Massimo
Trenti, Michele
Yung, L. Y. Aaron
contents The population of bright galaxies at $z\gtrsim10$ discovered by JWST, including the so-called "blue monsters", has been difficult to reconcile with standard galaxy evolution models. To shed light on this extraordinary population, we study the $z\sim8$ galaxies discovered by the BoRG-$JWST$ survey. These slightly-lower redshift analogs are comparable in UV luminosity to the blue monsters, and their lower redshift makes it much easier to access key rest frame optical diagnostics with NIRspec. We find that BoRG-$JWST$ galaxies are consistent with being dust-poor based on their blue UV slopes and Balmer decrement ratios. We find no strong evidence for dominant active galactic nuclei contribution to the UV brightness, based on line-ratio diagnostics, though some contribution cannot be excluded. We further infer the stellar mass, star formation and UV-brightness history of the BoRG-$JWST$ galaxies by fitting their rest-frame UV-optical spectra. We see evidence for stochastic episodes of star formation for all the BoRG-$JWST$ galaxies, providing a temporal boosting of UV luminosity in short timescales. The UV-bright blue monsters at $z\gtrsim10$ can be explained by the presence of stars with ages below 100 Myr.
format Preprint
id arxiv_https___arxiv_org_abs_2507_01014
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The BoRG-$JWST$ Survey: Analogs at $z\sim8$ to the UV-luminous Galaxy Population at $z\gtrsim10$
Rojas-Ruiz, Sofía
Roberts-Borsani, Guido
Morishita, Takahiro
Calabrò, Antonello
Bagley, Micaela B.
Treu, Tommaso
Finkelstein, Steven L.
Stiavelli, Massimo
Trenti, Michele
Yung, L. Y. Aaron
Astrophysics of Galaxies
The population of bright galaxies at $z\gtrsim10$ discovered by JWST, including the so-called "blue monsters", has been difficult to reconcile with standard galaxy evolution models. To shed light on this extraordinary population, we study the $z\sim8$ galaxies discovered by the BoRG-$JWST$ survey. These slightly-lower redshift analogs are comparable in UV luminosity to the blue monsters, and their lower redshift makes it much easier to access key rest frame optical diagnostics with NIRspec. We find that BoRG-$JWST$ galaxies are consistent with being dust-poor based on their blue UV slopes and Balmer decrement ratios. We find no strong evidence for dominant active galactic nuclei contribution to the UV brightness, based on line-ratio diagnostics, though some contribution cannot be excluded. We further infer the stellar mass, star formation and UV-brightness history of the BoRG-$JWST$ galaxies by fitting their rest-frame UV-optical spectra. We see evidence for stochastic episodes of star formation for all the BoRG-$JWST$ galaxies, providing a temporal boosting of UV luminosity in short timescales. The UV-bright blue monsters at $z\gtrsim10$ can be explained by the presence of stars with ages below 100 Myr.
title The BoRG-$JWST$ Survey: Analogs at $z\sim8$ to the UV-luminous Galaxy Population at $z\gtrsim10$
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2507.01014