James Webb Space Telescope Feed Post
JWST UNCOVER: Extremely Red and Compact Object at z phot ≃ 7.6 Triply Imaged by A2744
Paper abstract: 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.
