Two Exciting High-redshift Galaxy Candidates Turn Out to Be Two Exciting Brown Dwarfs

@article{bradac2026exciting,
  title = {{Two Exciting High-redshift Galaxy Candidates Turn Out to Be Two Exciting Brown Dwarfs}},
  author = {Maruša Bradac and Chris Willott and Yoshihisa Asada and Loïc Albert and Gregor Rihtaršič and Anishya Harshan and Jon Judež and Nicholas S. Martis and Andrea Ferrara and Kevin Hainline and Abdurro’uf and Joseph F. V. Allingham and Volker Bromm and John Chisholm and Dan Coe and Guillaume Desprez and Jose M. Diego and Andreas L. Faisst and Seiji Fujimoto and Lukas J. Furtak and Tiger Yu-Yang Hsiao and Kohei Inayoshi and Anton M. Koekemoer and Vasily Kokorev and Brian C. Lemaux and Paulo A. A. Lopes and Ray A. Lucas and Danilo Marchesini and Vladan Markov and Gaël Noirot and Richard Pan and Scott W. Randall and Johan Richard and Luke Robbins and Ghassan T. E. Sarrouh and Marcin Sawicki and Tim Schrabback and Roberta Tripodi and Eros Vanzella and Rogier A. Windhorst},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = oct,
  doi = {10.3847/2041-8213/ae9085},
  url = {https://iopscience.iop.org/article/10.3847/2041-8213/ae9085},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Two Exciting High-redshift Galaxy Candidates Turn Out to Be Two Exciting Brown Dwarfs
AU  - Maruša Bradac
AU  - Chris Willott
AU  - Yoshihisa Asada
AU  - Loïc Albert
AU  - Gregor Rihtaršič
AU  - Anishya Harshan
AU  - Jon Judež
AU  - Nicholas S. Martis
AU  - Andrea Ferrara
AU  - Kevin Hainline
AU  - Abdurro’uf
AU  - Joseph F. V. Allingham
AU  - Volker Bromm
AU  - John Chisholm
AU  - Dan Coe
AU  - Guillaume Desprez
AU  - Jose M. Diego
AU  - Andreas L. Faisst
AU  - Seiji Fujimoto
AU  - Lukas J. Furtak
AU  - Tiger Yu-Yang Hsiao
AU  - Kohei Inayoshi
AU  - Anton M. Koekemoer
AU  - Vasily Kokorev
AU  - Brian C. Lemaux
AU  - Paulo A. A. Lopes
AU  - Ray A. Lucas
AU  - Danilo Marchesini
AU  - Vladan Markov
AU  - Gaël Noirot
AU  - Richard Pan
AU  - Scott W. Randall
AU  - Johan Richard
AU  - Luke Robbins
AU  - Ghassan T. E. Sarrouh
AU  - Marcin Sawicki
AU  - Tim Schrabback
AU  - Roberta Tripodi
AU  - Eros Vanzella
AU  - Rogier A. Windhorst
PY  - 2026
DA  - 2026/10/07
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8213/ae9085
UR  - https://iopscience.iop.org/article/10.3847/2041-8213/ae9085
AB  - From the onset of observations of JWST we have discovered unexpectedly luminous galaxies at redshifts z > 10 and as high as z = 14. With their discovery, the question immediately followed as to where their progenitors are, since such progenitors should be within reach of existing surveys. However, the discovery of several bright candidates at z > 15 may indicate further discrepancies between pre-JWST model predictions and current observations. Progenitors of the bright z ∼ 14 galaxies should be visible at redshifts as high as z ∼ 20–30, showing in the data as F277W and F356W dropouts. We identify two such candidates in the Bullet Cluster JWST data; however, subsequent NIRSpec follow-up data show spectra that can be well fit with Y dwarf templates with temperatures 272–351 K and and 445–525 K (using ATMO2020 and Sonora Elf Owl models) and distances of ∼150–650 pc. The first is one of the lowest-temperature brown dwarfs known, and the lowest-temperature brown dwarf detected spectroscopically outside the solar neighborhood. With additional NIRCam imaging taken ∼1 yr later, we also detect their proper motions of (49 ± 8) mas yr ⁻¹ and (24 ± 3) mas yr ⁻¹ , further indicating that at least some F277W and F356W dropouts are substellar cold Milky Way objects such as brown dwarfs.
SN  - 2041-8205
SN  - 2041-8213
ER  -