James Webb Space Telescope Feed Post

JWST UNCOVER: Extremely red and compact object atz_{\mathrm{phot}}\simeq7.6 triply imaged by Abell 2744 Published: 12/20/2022 8:45:58 PM Updated: 6/7/2023 11:32:04 AM

Paper abstract: Recent JWST/NIRCam imaging taken for the ultra-deep UNCOVER program reveals avery red dropout object at z_{\mathrm{phot}}~eq7.6, triply imaged by thegalaxy cluster Abell 2744 (z_{\mathrm{d}}=0.308). All three images are verycompact, i.e. unresolved, with a de-lensed size upper-limit ofr_{e}<~35 pc. The images have apparent magnitudes ofm_{\mathrm{F444W}}~25-26 AB, and the magnification-corrected absolute UVmagnitude of the source is M_{\mathrm{UV},1450}=-16.81\pm0.09. From the sumof observed fluxes and from a spectral energy distribution (SED) analysis, weobtain estimates of the bolometric luminosities of the source ofL_{\mathrm{bol}}\gtrsim10^{43} \frac{\mathrm{erg}}{\mathrm{s}} andL_{\mathrm{bol}}~10^{44}-10^{46} \frac{\mathrm{erg}}{\mathrm{s}},respectively. Based on its compact, point-like appearance, its position incolor-color space and the SED analysis, we tentatively conclude that thisobject is a UV-faint dust-obscured quasar-like object, i.e. an active galacticnucleus (AGN) at high redshift. We also discuss other alternative origins forthe object's emission features, including a massive star cluster, PopulationIII, supermassive, or dark stars, or a direct-collapse black hole. Althoughpopulations of red galaxies at similar photometric redshifts have been detectedwith JWST, this object is unique in that its high-redshift nature iscorroborated geometrically by lensing, that it is unresolved despite beingmagnified -- and thus intrinsically even more compact -- and that it occupiesnotably distinct regions in both size-luminosity and color-color space. PlannedUNCOVER JWST/NIRSpec observations, scheduled in Cycle 1, will enable a moredetailed analysis of this object.