Giovanni Gandolfi, G. Rodighiero, M. Castellano, A. Fontana, Paola Santini, Mark Dickinson, Steven Finkelstein, Michele Catone, Antonello Calabrò, E. Merlin, L. Pentericci, Laura Bisigello, A. Grazian, Lorenzo Napolitano, Benedetta Vulcani, Anthony J. Taylor, Pablo Arrabal Haro, Allison Kirkpatrick, Bren E. Backhaus, Benne W. Holwerda, Marika Giulietti, A. Bianchetti, P. Cassata, N. J. Cleri, E. Daddi, H. C. Ferguson, G. Girardi, M. Hirschmann, A. M. Koekemoer, A. Lapi, F. Pacucci, P. G. Pérez-González, A. de la Vega, A. Vietri, S. Wilkins, L. Y. Aaron Yung, M. Bagley, R. Bhatawdekar, J. Kartaltepe, C. Papovich, N. Pirzkal
Context. The James Webb Space Telescope (JWST) has uncovered a diverse population of extreme near-infrared dropouts, including ultra-high-redshift ( z > 15) galaxy candidates, dust-obscured galaxies challenging theories of dust production, sources with strong Balmer breaks (possibly compact active galactic nuclei in dense gas-rich environments), and cold, substellar Galactic objects. Aims. This work presents Capotauro , a F356W-dropout identified in the CEERS survey with a F444W AB magnitude of ∼27.68 and exhibiting a sharp flux drop by > 3 mag between 3.5 and 4.5 μm, being nondetected below 3.5 μm. We investigated its nature and constrained its properties, paving the way for follow-up observations. Methods. We combined JWST/NIRCam, MIRI, and NIRSpec/MSA data with HST/ACS and WFC3 observations to perform a spectrophotometric analysis of Capotauro using multiple SED-fitting codes. Our setup is tailored to test z ≥ 15 as well as z < 10 dusty, Balmer-break or strong-line emitter galaxy solutions, and the possibility of Capotauro being a Milky Way substellar object. Results. Among extragalactic options, our analysis favors interpreting the sharp flux drop of Capotauro as a bright ( M UV ∼ −21.5) Lyman break at z ∼ 32, consistent with the formation epoch of the first stars and black holes, with only ∼0.5% of the redshift posterior volume lying at z < 25. Lower-redshift solutions struggle to reproduce the extreme break, suggesting that if Capotauro resides at z < 10, it must show a nonstandard combination of high dust attenuation and/or prominent Balmer breaks, making it a peculiar interloper. Finally, our analysis indicates that Capotauro ’s properties could be consistent with it being a very cold (i.e., Y2-Y3 type) brown dwarf or a free-floating exoplanet with a record-breaking combination of low temperature and large distance ( T eff ≤ 300 K; d ≳ 130 pc, up to ∼2 kpc). Conclusions. While present observations cannot determine Capotauro ’s nature, our analysis points to a remarkably unique object in all plausible scenarios. This makes Capotauro stand out as a compelling target for follow-up observations.