JWST UNCOVER: Extremely Red and Compact Object at z phot ≃ 7.6 Triply Imaged by A2744
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2023
- DOI:
- arXiv:
- arXiv:2212.10531
- Bibcode:
- 2023ApJ...952..142F
- Keywords:
-
- High-redshift galaxies;
- Low-luminosity active galactic nuclei;
- Reionization;
- Strong gravitational lensing;
- 734;
- 2033;
- 1383;
- 1643;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in ApJ. Considerable updates to the SED-fitting section, including the discussion of a heavily dust-obscured type 1 AGN as the most likely scenario