PRISMS/U13151. A Glimpse into the Earliest Phases of Galaxy Formation through an Ultra-Faint System ≈ 500 Myr after the Big Bang

@misc{rinaldi2026prismsu13151,
  title = {{PRISMS/U13151. A Glimpse into the Earliest Phases of Galaxy Formation through an Ultra-Faint System $\approx$ 500 Myr after the Big Bang}},
  author = {Pierluigi Rinaldi and Javier Álvarez-Márquez and Alejandro Crespo Gómez and Luis Colina and Stefano Carniani and Sarah Kendrew and Edoardo Iani and Angela Adamo and Abdurro'uf and Marianna Annunziatella and Stacey Alberts and Leindert A. Boogaard and Karina I. Caputi and Marco Castellano and Michele Catone and Rui Marques-Chaves and Ryan Cooper and Seiji Fujimoto and Mahmoud Hamed and Yuichi Harikane and Santosh Harish and Takuya Hashimoto and Jakob M. Helton and Tiger Y. -Y. Hsiao and Vasily Kokorev and Álvaro Labiano and Jens Melinder and Ikki Mitsuhashi and Göran Östlin and Lorenzo Napolitano and Borja Pérez-Díaz and Pablo G. Pérez-González and Carlota Prieto Jiménez and Giulia Rodighiero and Paola Santini and Ana Varo-O'Ferrall and Jorge A. Zavala and Yongda Zhu},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.26560},
  eprint = {2610.26560},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.26560},
  note = {CC0},
}

TY  - UNPB
TI  - PRISMS/U13151. A Glimpse into the Earliest Phases of Galaxy Formation through an Ultra-Faint System ≈ 500 Myr after the Big Bang
AU  - Pierluigi Rinaldi
AU  - Javier Álvarez-Márquez
AU  - Alejandro Crespo Gómez
AU  - Luis Colina
AU  - Stefano Carniani
AU  - Sarah Kendrew
AU  - Edoardo Iani
AU  - Angela Adamo
AU  - Abdurro'uf
AU  - Marianna Annunziatella
AU  - Stacey Alberts
AU  - Leindert A. Boogaard
AU  - Karina I. Caputi
AU  - Marco Castellano
AU  - Michele Catone
AU  - Rui Marques-Chaves
AU  - Ryan Cooper
AU  - Seiji Fujimoto
AU  - Mahmoud Hamed
AU  - Yuichi Harikane
AU  - Santosh Harish
AU  - Takuya Hashimoto
AU  - Jakob M. Helton
AU  - Tiger Y. -Y. Hsiao
AU  - Vasily Kokorev
AU  - Álvaro Labiano
AU  - Jens Melinder
AU  - Ikki Mitsuhashi
AU  - Göran Östlin
AU  - Lorenzo Napolitano
AU  - Borja Pérez-Díaz
AU  - Pablo G. Pérez-González
AU  - Carlota Prieto Jiménez
AU  - Giulia Rodighiero
AU  - Paola Santini
AU  - Ana Varo-O'Ferrall
AU  - Jorge A. Zavala
AU  - Yongda Zhu
PY  - 2026
DA  - 2026/10/19
PB  - arXiv
DO  - 10.48550/arxiv.2610.26560
UR  - https://arxiv.org/abs/2610.26560
AB  - Detailed UV-to-optical studies of galaxies at z >= 10 have largely focused on bright systems (MUV <= -20 mag), leaving intrinsically faint galaxies virtually unexplored to date. Combining NIRCam, NIRSpec, and MIRI imaging and spectroscopy, we investigate UNCOVER-ABELL2744-13151 (U13151), an ultra-faint galaxy at z = 9.7995 (MUV = -17.44 mag), magnified by Abell 2744 (μ = 12.8). U13151 is very blue (β ~ -2.64), ultra-low mass (log10(M*/Msun) ~ 6.68), young (~ 5.5 Myr), metal-poor (Z ~ 3-6% Zsun), and compact (Re ~ 122 pc). It exhibits negligible dust attenuation, extreme ionization conditions, and intense star formation (sSFR(Ha) ~ 94 Gyr-1, or equivalently M*/SFR(Ha) ~ 10.6 Myr). Despite similarities with much brighter galaxies, its low C/O, approximately solar Ne/O, and undetected nitrogen emission suggest enrichment dominated by core-collapse supernovae, in stark contrast with similar nitrogen-enhanced systems. U13151 might be undergoing its first major episode of star formation, assembling most (if not all) of its M* through five unresolved clumps. Its high ionizing photon production efficiency (log10(ξ_ion/ (Hz erg-1)) ~ 25.64) suggests, through a simple toy model, suggests, through a simple toy model, that similarly short-lived episodes could contribute significantly to the ionizing photon budget of low-mass galaxies during Cosmic Reionization. We explore different evolutionary scenarios, from U13151-like galaxies potentially representing the progenitors of Blue Monsters at higher redshifts to the possibility that such systems could be the early building blocks of present-day Milky Way-like galaxies. Our results highlight the fundamental role of MIRI in studying galaxies in the early Universe and the urgent need to investigate the faintest, lowest-mass systems to shed light on the fundamental physics driving the earliest phases of galaxy formation.
ER  -