James Webb Space Telescope Feed Post

JWST UNCOVER: Extremely red and compact object at Zphot=7.6 triply imaged by Abell 2744

JWST/NIRCam composite-color image of Abell 2744 (Blue: F115W+F150W, Green: F200W+F277W, Red: F356W+F410W+F444W) together with the critical curves from our SL model for sources at Zs = 1.69 (blue) and Zs = 7.5 (red ). The notable three point-like red multiple images in cyan squares are the images (and zoomed-in versions) of the quasar candidate reported here at a redshift of Zphot = 7.6. We refer to these as QSO1A, B and C. For comparison, we also show the three images (JD1A, B and candidate C image) of the Zitrin et al. (2014) z = 9.76 object recently confirmed in Roberts-Borsani et al. (2022) with JWST spectroscopy, in orange squares. All squares in the figure encompass about 2.4" x 2.4", and a 20" bar is given in the bottom left corner. Note that despite being at a lower redshift than JD, the faint quasar candidate is significantly redder. Also, the images of JD1 show significant structure, whereas the images of our object are point-like, implying a very compact de-magnified size of re < 35 pc, at most. Recent JWST/NIRCam imaging taken for the ultra-deep UNCOVER program reveals a very red dropout object at Zphot=7.6, triply imaged by the galaxy cluster Abell 2744 (zd=0.308). All three images are very compact, i.e. unresolved, with a de-lensed size upper-limit of re<=35 pc. The images have apparent magnitudes of mF444W-25-26 AB, and the magnification-corrected absolute UV magnitude of the source is MUV,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 Lbol>=1043ergs and Lbol-1044-1046ergs, 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 (AGN) 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. (From Paper)