An Attenuation Bump at z=9.3: Probing Dust Diversity at Cosmic Dawn

@misc{rodighiero2026attenuation,
  title = {{An Attenuation Bump at z=9.3: Probing Dust Diversity at Cosmic Dawn}},
  author = {Giulia Rodighiero and Santiago Álvarez-Córdoba and Michele Catone and Borja Pérez-Díaz and Andrea Ferrara and Giorgia Girardi and Lorenzo Napolitano and Paola Santini and Hollis B. Akins and Caitlin M. Casey and Maximilien Franco and Pietro Benotto and Rachana Bhatawdekar and Alessandro Bianchetti and Laura Bisigello and Daniela Calzetti and Paolo Cassata and Marco Castellano and Christopher J. Conselice and Poulomi Dam and Pratika Dayal and Andrea Enia and Gaia Edes Esposito and Andreas L. Faisst and Giovanni Gandolfi and Steven Gillman and Andrea Grazian and Carlotta Gruppioni and Michaela Hirschmann and Edoardo Iani and Kohei Inayoshi and Jeyhan S. Kartaltepe and Georgios Magdis and Alessandro Marconi and Crystal L. Martin and Bo Milvang-Jensen and Annagrazia Puglisi and Alvio Renzini and R. Michael Rich and Pierluigi Rinaldi and Brant E. Robertson and Stephen Serjeant and Irene Shivaei and Sune Toft and Amelia Vietri and Benedetta Vulcani and Fabian Walter and Stephen M. Wilkins and Jorge A. Zavala},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.20722},
  eprint = {2610.20722},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.20722},
}

TY  - UNPB
TI  - An Attenuation Bump at z=9.3: Probing Dust Diversity at Cosmic Dawn
AU  - Giulia Rodighiero
AU  - Santiago Álvarez-Córdoba
AU  - Michele Catone
AU  - Borja Pérez-Díaz
AU  - Andrea Ferrara
AU  - Giorgia Girardi
AU  - Lorenzo Napolitano
AU  - Paola Santini
AU  - Hollis B. Akins
AU  - Caitlin M. Casey
AU  - Maximilien Franco
AU  - Pietro Benotto
AU  - Rachana Bhatawdekar
AU  - Alessandro Bianchetti
AU  - Laura Bisigello
AU  - Daniela Calzetti
AU  - Paolo Cassata
AU  - Marco Castellano
AU  - Christopher J. Conselice
AU  - Poulomi Dam
AU  - Pratika Dayal
AU  - Andrea Enia
AU  - Gaia Edes Esposito
AU  - Andreas L. Faisst
AU  - Giovanni Gandolfi
AU  - Steven Gillman
AU  - Andrea Grazian
AU  - Carlotta Gruppioni
AU  - Michaela Hirschmann
AU  - Edoardo Iani
AU  - Kohei Inayoshi
AU  - Jeyhan S. Kartaltepe
AU  - Georgios Magdis
AU  - Alessandro Marconi
AU  - Crystal L. Martin
AU  - Bo Milvang-Jensen
AU  - Annagrazia Puglisi
AU  - Alvio Renzini
AU  - R. Michael Rich
AU  - Pierluigi Rinaldi
AU  - Brant E. Robertson
AU  - Stephen Serjeant
AU  - Irene Shivaei
AU  - Sune Toft
AU  - Amelia Vietri
AU  - Benedetta Vulcani
AU  - Fabian Walter
AU  - Stephen M. Wilkins
AU  - Jorge A. Zavala
PY  - 2026
DA  - 2026/10/14
PB  - arXiv
DO  - 10.48550/arxiv.2610.20722
UR  - https://arxiv.org/abs/2610.20722
AB  - 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.
ER  -