Year: 2026
Type: preprint
Abstract: We report the identification of a UV attenuation bump in the Black Pearl, a galaxy at a spectroscopic redshift of 9.3335 observed with JWST/NIRSpec as part of the ZENITH and EMBER surveys. This is the highest-redshift UV bump reported to date, probing dust properties only approximately 500 Myr after the Big Bang. The feature is directly detected as a broad depression in the rest-frame UV continuum and is well described by a local Drude profile, with a central wavelength of 2132+/-17 Angstroms, an FWHM of 413+/-54 Angstroms, and a peak attenuation of 0.21+/-0.02 mag. Joint spectrophotometric modeling with a flexible attenuation law independently recovers a pronounced UV bump without imposing its presence a priori, regardless of the adopted star-formation history. The modeling indicates a relatively low-mass, actively star-forming galaxy, with a logarithmic stellar mass of 8.35 (+0.09/-0.08) in solar units, a star-formation rate of 2.36 (+0.54/-0.42) solar masses per year, and a visual attenuation of 0.34 (+0.12/-0.11) mag. Rest-frame optical emission-line diagnostics indicate a hard ionizing spectrum and allow for a moderate AGN contribution, but provide no evidence for a powerful AGN capable of dominating the observed UV continuum. The bump is blueshifted by 43+/-17 Angstroms (approximately 2.5 sigma) relative to the canonical Milky Way 2175 Angstrom feature and by 127 +/- 17 Angstroms relative to the few UV bumps currently known at redshift approximately 7, while its width is consistent with the broad distribution measured along Milky Way sightlines. The displaced central wavelength therefore provides the clearest evidence for a nonstandard UV-bump profile at redshift 9.3335, pointing to substantial diversity in the properties of UV-bump carriers at early cosmic times, with both PAHs and small graphite grains remaining plausible candidates.
Source: arXiv (Cornell University)
Authors: Rodighiero, Giulia, Álvarez-Córdoba, Santiago, Catone, Michele, Pérez-Díaz, Borja, Ferrara, Andrea, Girardi, Giorgia, Napolitano, Lorenzo, Santini, Paola, Akins, Hollis B., Casey, Caitlin M., Franco, Maximilien, Benotto, Pietro, Bhatawdekar, Rachana, Bianchetti, Alessandro, Bisigello, Laura, Calzetti, Daniela, Cassata, Paolo, Castellano, Marco, Conselice, Christopher J., Dam, Poulomi, Dayal, Pratika, Enia, Andrea, Esposito, Gaia Edes, Faisst, Andreas L., Gandolfi, Giovanni, Gillman, Steven, Grazian, Andrea, Gruppioni, Carlotta, Hirschmann, Michaela, Iani, Edoardo, Inayoshi, Kohei, Kartaltepe, Jeyhan S., Magdis, Georgios, Marconi, Alessandro, Martin, Crystal L., Milvang-Jensen, Bo, Puglisi, Annagrazia, Renzini, Alvio, Rich, R. Michael, Rinaldi, Pierluigi, Robertson, Brant E., Serjeant, Stephen, Shivaei, Irene, Toft, Sune, Vietri, Amelia, Vulcani, Benedetta, Walter, Fabian, Wilkins, Stephen M., Zavala, Jorge A.
Institutions: Universidad Nacional Autónoma de México, Astronomical Observatory of Rome, Scuola Normale Superiore, Accademia Nazionale dei Lincei, University of Padua, Osservatorio Astronomico di Padova, National Institute for Astrophysics, University of California, Santa Barbara, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Sorbonne Université, European Space Agency, European Space Astronomy Centre, University of Massachusetts Amherst, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, CEA Paris-Saclay - Etablissement de Saclay, CEA Paris-Saclay, Institut de Recherche sur les Lois Fondamentales de l'Univers, California Institute of Technology, Infrared Processing and Analysis Center, DTU Space, Technical University of Denmark, Osservatorio di Astrofisica e Scienza dello Spazio, Institute of Science and Technology Austria, Peking University, Rochester Institute of Technology, University of Copenhagen, Arcetri Astrophysical Observatory, University of Southampton, University of Florence, University of California, Santa Cruz, Max Planck Institute for Astronomy, University of Sussex, University of Malta
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: European Commission
Award: G972786147
OpenAlex ID: W7222618372