Year: 2026
Type: article
Abstract: 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.
Authors: Maruša Bradac, Chris Willott, Yoshihisa Asada, Loïc Albert, Gregor Rihtaršič, Anishya Harshan, Jon Judež, Nicholas S. Martis, Andrea Ferrara, Kevin Hainline, Abdurro’uf, Joseph F. V. Allingham, Volker Bromm, John Chisholm, Dan Coe, Guillaume Desprez, Jose M. Diego, Andreas L. Faisst, Seiji Fujimoto, Lukas J. Furtak, Tiger Yu-Yang Hsiao, Kohei Inayoshi, Anton M. Koekemoer, Vasily Kokorev, Brian C. Lemaux, Paulo A. A. Lopes, Ray A. Lucas, Danilo Marchesini, Vladan Markov, Gaël Noirot, Richard Pan, Scott W. Randall, Johan Richard, Luke Robbins, Ghassan T. E. Sarrouh, Marcin Sawicki, Tim Schrabback, Roberta Tripodi, Eros Vanzella, Rogier A. Windhorst
Institutions: University of Ljubljana, University of California, Davis, Herzberg Institute of Astrophysics, National Research Council Canada, Université de Montréal, Scuola Normale Superiore, University of Arizona, Indiana University, Ben-Gurion University of the Negev, The University of Texas at Austin, Space Telescope Science Institute, Association of Universities for Research in Astronomy, Johns Hopkins University, University of Groningen, Instituto de Física de Cantabria, Infrared Processing and Analysis Center, University of Toronto, Peking University, International Gemini Observatory, Universidade Federal do Rio de Janeiro, Tufts University, Center for Astrophysics Harvard & Smithsonian, Lyon 1 Université, York University, Saint Mary's University, Universität Innsbruck, Astronomical Observatory of Rome, Institute for Fundamental Physics of the Universe, National Institute for Astrophysics, Osservatorio di Astrofisica e Scienza dello Spazio, Arizona State University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
Funders: National Science Foundation, National Aeronautics and Space Administration, Canadian Foundation for AIDS Research, Canarie, Space Telescope Science Institute, Ministerio de Ciencia, Innovación y Universidades, European Commission, National Natural Science Foundation of China, University of Toronto, Alliance de recherche numérique du Canada, Goddard Space Flight Center, Smithsonian Astrophysical Observatory, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Agencia Estatal de Investigación, HORIZON EUROPE European Research Council, NextGenerationEU
Awards: G103270039, G1055883707, G1390571956, G2271590008, G231133531, G256731684, G2648730778, Exploring Cosmic Dawn with James Webb Space Telescope, G3561758408, G3815726687, Exploring Cosmic Noon and Cosmic Dawn with JWST Guaranteed Time Observations, G4212894969, G4236146676, G5560469105, G5568641063, G5681601665, G5788056106, G579566091, G6043888741, G6608474652, G6722835988, G6909262500, G7328853082, THE PROPOSAL SEEKS TO ACCOMPLISH SEVERAL INVESTIGATIONS TO SIMULATE THE PERFORMANCE OF JWST DEEP FIELD SURVEYS, VARYING AS-YET-POORLY CHARACTERIZED P, IN 2002 WE WERE GRANTED 110 HOURS GTO TIME FOR A JWST MEDIUM-DEEP SURVEY. WITH HST AND SPITZER EXPERIENCE 14 YEARS LATER WE REDEFINE THIS SURVEY TO IMAGE~18 NIRCAM FIELDS IN 7 FILTERS TO AB<~ 29 29.3 MAG YIELDING 140 000 GALAXIES AT 0<~ Z<~ 12 15 IN 0.05 DEG2 (>~ 30 HUDFS!). WE WILL STUDY GALAXY ASSEMBLY + SUPER-MASSIVE BLACK-HOLE GROWTH AT Z 0 7 INCLUDING OBJECT VARIABILITY ON MONTHS YEARS TIMESCALES. WE STUDY THE REIONIZING POPULATION AT Z 2 8 AND USE THE BEST LENSING TARGETS TO OPTIMIZE OUR STUDY OF FIRST LIGHT OBJECTS AT Z 10 15. OUR SCIENCE GOALS ARE: 1. GALAXY ASSEMBLY; 2. SUPER-MASSIVE BLACK-HOLE GROWTH; 3. REIONIZATION; 4. FIRST LIGHT; 5. STUDY THE BEST LENSING CLUSTERS TO FIND JWST OBJECTS. MAP&REMOVE STRAYLIGHT GRADIENTS AND QUANTIFY SAMPLE COMPLETENESS IN RANDOM FIELD&CLUSTER IMAGES: WE WILL: A) USE HUDF AND HFF DATA TO SIMULATE MAP AND REMOVE A RANGE OF STRAYLIGHT AMPLITUDES AND GRADIENTS THAT COULD AFFECT RANDOM DEEP FIELDS (DFS) AND CLUSTER FIELDS WITH JWST; B) DETERMINE ACCURATE COMPLETENESS CORRECTIONS VS. GALAXY FLUX SIZE WAVELENGTH AND LOCATION IN JWST DFS OF VARIOUS DEPTH AND IN CLUSTER FIELDS WITH THEIR KNOWN GALAXY CLUSTER+ICL FOREGROUND; C) DETERMINE THE CLUSTER SELECTION FUNCTIONS BY FOLDING LENSING MAPS WITH SIMULATED BACKGROUND IMAGES YIELDING SIMULATED LENSED IMAGES AND THEIR COMPLETENESS CORRECTIONS FOR LENSED SOURCES WHICH WE SHOW CAN BE FACTORS 2 3; AND D) MODEL COSMIC VARIANCE IN HIERARCHICAL MODELS AT Z 6 15. WE WILL CORRECT THE LFS FOR THESE COMPLETENESS FUNCTIONS. WE WILL THEN USE A BAYESIAN CODE TO DETERMINE THE OPTIMAL SET OF LF EVOLUTION PARAMETERS FROM THE AVAILABLE JWST DATA TO QUANTIFY HOW GALAXIES ASSEMBLED SINCE Z<~ 15., G8684856318, Exploring Cosmic Noon and Cosmic Dawn with JWST Guaranteed Time Observations, G8865192224, G972786147
OpenAlex ID: W7220864480