EGS-z11-R0: a red, dust-rich galaxy at Cosmic Dawn

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Hauptverfasser: Rodighiero, Giulia, Ferrara, Andrea, Catone, Michele, Napolitano, Lorenzo, Cassata, Paolo, Gandolfi, Giovanni, Merlin, Emiliano, Grazian, Andrea, Renzini, Alvio, Bisigello, Laura, Castellano, Marco, Pérez-González, Pablo G., Pérez-Díaz, Borja, Iani, Edoardo, Gruppioni, Carlotta, Finkelstein, Steven L., Koekemoer, Anton M., Bianchetti, Alessandro, Sinigaglia, Francesco
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Veröffentlicht: 2026
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author Rodighiero, Giulia
Ferrara, Andrea
Catone, Michele
Napolitano, Lorenzo
Cassata, Paolo
Gandolfi, Giovanni
Merlin, Emiliano
Grazian, Andrea
Renzini, Alvio
Bisigello, Laura
Castellano, Marco
Pérez-González, Pablo G.
Pérez-Díaz, Borja
Iani, Edoardo
Gruppioni, Carlotta
Finkelstein, Steven L.
Koekemoer, Anton M.
Bianchetti, Alessandro
Sinigaglia, Francesco
author_facet Rodighiero, Giulia
Ferrara, Andrea
Catone, Michele
Napolitano, Lorenzo
Cassata, Paolo
Gandolfi, Giovanni
Merlin, Emiliano
Grazian, Andrea
Renzini, Alvio
Bisigello, Laura
Castellano, Marco
Pérez-González, Pablo G.
Pérez-Díaz, Borja
Iani, Edoardo
Gruppioni, Carlotta
Finkelstein, Steven L.
Koekemoer, Anton M.
Bianchetti, Alessandro
Sinigaglia, Francesco
contents Context. Galaxies discovered by JWST at z > 10 are predominantly characterized by extremely blue rest-frame UV slopes. Conversely, the existence of dust-reddened systems at such early epochs has remained largely unconfirmed spectroscopically. Aims. We present the spectroscopic confirmation of EGS-z11-R0 at z = 11.45, the most distant red galaxy identified to date, discovered serendipitously through inspection of publicly available JWST/NIRSpec data. Methods. We analyze JWST/NIRSpec PRISM and G395M spectroscopy together with multiwavelength HST, NIRCam, and MIRI photometry. We identify significant detections of the C IV 1548,1551 and C III] 1908 transitions, yielding a redshift of zspec = 11.452 +/- 0.021. We measure rest-frame UV emission-line fluxes and equivalent widths and use these diagnostics to constrain the nature of the ionizing radiation field. Finally, we perform spectral energy distribution modeling with CIGALE, combining spectroscopy with photometry and including stellar, nebular, dust, and active galactic nuclei (AGN) components. Results. EGS-z11-R0 exhibits a red UV continuum slope (betaUV approximately -1.0), placing it well above the canonical MUV-betaUV relation at z~10-12 and making it the highest-z spectroscopically confirmed member of the emerging "red monster" population. Emission-line diagnostics reveal a hard ionizing spectrum consistent with extreme star formation and compatible with a composite stellar plus AGN scenario. The best-fit SED solution favors a stellar mass of log(M*/Msun) ~ 9.2-9.6, a SFR of 10-40 Msun yr^-1, and substantial dust attenuation (AV~1.2 mag). Conclusions. The confirmation of EGS-z11-R0 establishes that chemically evolved, dust-enriched galaxies were already in place at z approximately 11.5. [abridged]
format Preprint
id arxiv_https___arxiv_org_abs_2603_15841
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle EGS-z11-R0: a red, dust-rich galaxy at Cosmic Dawn
Rodighiero, Giulia
Ferrara, Andrea
Catone, Michele
Napolitano, Lorenzo
Cassata, Paolo
Gandolfi, Giovanni
Merlin, Emiliano
Grazian, Andrea
Renzini, Alvio
Bisigello, Laura
Castellano, Marco
Pérez-González, Pablo G.
Pérez-Díaz, Borja
Iani, Edoardo
Gruppioni, Carlotta
Finkelstein, Steven L.
Koekemoer, Anton M.
Bianchetti, Alessandro
Sinigaglia, Francesco
Astrophysics of Galaxies
Context. Galaxies discovered by JWST at z > 10 are predominantly characterized by extremely blue rest-frame UV slopes. Conversely, the existence of dust-reddened systems at such early epochs has remained largely unconfirmed spectroscopically. Aims. We present the spectroscopic confirmation of EGS-z11-R0 at z = 11.45, the most distant red galaxy identified to date, discovered serendipitously through inspection of publicly available JWST/NIRSpec data. Methods. We analyze JWST/NIRSpec PRISM and G395M spectroscopy together with multiwavelength HST, NIRCam, and MIRI photometry. We identify significant detections of the C IV 1548,1551 and C III] 1908 transitions, yielding a redshift of zspec = 11.452 +/- 0.021. We measure rest-frame UV emission-line fluxes and equivalent widths and use these diagnostics to constrain the nature of the ionizing radiation field. Finally, we perform spectral energy distribution modeling with CIGALE, combining spectroscopy with photometry and including stellar, nebular, dust, and active galactic nuclei (AGN) components. Results. EGS-z11-R0 exhibits a red UV continuum slope (betaUV approximately -1.0), placing it well above the canonical MUV-betaUV relation at z~10-12 and making it the highest-z spectroscopically confirmed member of the emerging "red monster" population. Emission-line diagnostics reveal a hard ionizing spectrum consistent with extreme star formation and compatible with a composite stellar plus AGN scenario. The best-fit SED solution favors a stellar mass of log(M*/Msun) ~ 9.2-9.6, a SFR of 10-40 Msun yr^-1, and substantial dust attenuation (AV~1.2 mag). Conclusions. The confirmation of EGS-z11-R0 establishes that chemically evolved, dust-enriched galaxies were already in place at z approximately 11.5. [abridged]
title EGS-z11-R0: a red, dust-rich galaxy at Cosmic Dawn
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2603.15841