JWST UNCOVER: Extremely Red and Compact Object at z phot ≃ 7.6 Triply Imaged by A2744

Lukas J. Furtak, Adi Zitrin, Adèle Plat, Seiji Fujimoto, Bingjie Wang, Erica J. Nelson, Ivo Labbé, Rachel Bezanson, Gabriel B. Brammer, Pieter van Dokkum, Ryan Endsley, Karl Glazebrook, Jenny E. Greene, Joel Leja, Sedona H. Price, Renske Smit, Daniel P. Stark, John R. Weaver, Katherine E. Whitaker, Hakim AtekJacopo Chevallard, Emma Curtis-Lake, Pratika Dayal, Anna Feltre, Marijn Franx, Yoshinobu Fudamoto, Danilo Marchesini, Lamiya A. Mowla, Richard Pan, Katherine A. Suess, Alba Vidal-García, Christina C. Williams

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Recent JWST/NIRCam imaging taken for the ultra-deep UNCOVER program reveals a very red dropout object at z phot ≃ 7.6, triply imaged by the galaxy cluster A2744 (z d = 0.308). All three images are very compact, i.e., unresolved, with a delensed size upper limit of r e ≲ 35 pc. The images have apparent magnitudes of m F444W ∼ 25−26 AB, and the magnification-corrected absolute UV magnitude of the source is M UV,1450 = −16.81 ± 0.09. From the sum of observed fluxes and from a spectral energy distribution (SED) analysis, we obtain estimates of the bolometric luminosities of the source of L bol ≳ 1043 erg s−1 and L bol ∼ 1044–1046 erg s−1, respectively. Based on its compact, point-like appearance, its position in color–color space, and the SED analysis, we tentatively conclude that this object is a UV-faint dust-obscured quasar-like object, i.e., an active galactic nucleus at high redshift. We also discuss other alternative origins for the object’s emission features, including a massive star cluster, Population III, supermassive, or dark stars, or a direct-collapse black hole. Although populations of red galaxies at similar photometric redshifts have been detected with JWST, this object is unique in that its high-redshift nature is corroborated geometrically by lensing, that it is unresolved despite being magnified—and thus intrinsically even more compact—and that it occupies notably distinct regions in both size–luminosity and color–color space. Planned UNCOVER JWST/NIRSpec observations, scheduled in Cycle 1, will enable a more detailed analysis of this object.
Original languageEnglish
Article number142
Pages (from-to)1-14
Number of pages14
JournalThe Astrophysical Journal
Issue number2
Early online date25 Jul 2023
Publication statusPublished - 1 Aug 2023


  • Reionization
  • Low-luminosity active galactic nuclei
  • High-redshift galaxies
  • Strong gravitational lensing


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