Uncovering a Massive z 7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web
Casey, Caitlin M.; Chworowsky, Katherine; Hutchison, Taylor A.; Kartaltepe, Jeyhan S.; Koekemoer, Anton M.; Long, Arianna S.; Zavala, Jorge A.; Martin, Crystal L.; Stiavelli, Massimo; Rhodes, Jason; Ilbert, Olivier; Gillman, Steven; Robertson, Brant E.; McKinney, Jed; Toft, Sune; Hirschmann, Michaela; Liu, Daizhong; Hayward, Christopher C.; Nyland, Kristina; Chiaberge, Marco; Clarke, Tracy E.; Onoue, Masafusa; Champagne, Jaclyn B.; Trakhtenbrot, Benny; Lambrides, Erini; Capetti, Alessandro; Norman, Colin; Jahnke, Knud; Silverman, John D.; Jin, Shuowen; Kokorev, Vasily; Vardoulaki, Eleni; Shuntov, Marko; Allen, Natalie; Dong, Dillon Z.; Faisst, Andreas L.; Franco, Maximilien; McCracken, Henry Joy; Akins, Hollis B.; Cooper, Olivia R.; Ding, Xuheng; Gozaliasl, Ghassem; Harish, Santosh; Paquereau, Louise; Andika, Irham Taufik; Manning, Sinclaire M.; Ptak, Andrew F.; Hall, Kirsten R.; Forman, Jordan Y.; Kleiner, Emma T.
United States, Germany, Italy, Denmark, Japan, Finland, Switzerland, Netherlands, China, Israel, France
Abstract
In this Letter, we report the discovery of the highest redshift, heavily obscured, radio-loud (RL) active galactic nucleus (AGN) candidate selected using JWST NIRCam/MIRI, mid-IR, submillimeter, and radio imaging in the COSMOS-Web field. Using multifrequency radio observations and mid-IR photometry, we identify a powerful, RL, growing supermassive black hole with significant spectral steepening of the radio spectral energy distribution (f 1.28 GHz ~ 2 mJy, q 24 μm = -1.1, α 1.28-3 GHz = - 1.2, Δα = - 0.4). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/near-infrared (NIR) data and thus infer heavy amounts of obscuration (N H > 1023 cm-2). Using the wealth of deep UV to submillimeter photometric data, we report a singular solution photo-z of z phot = ${7.7}_{-0.3}^{+0.4}$ and estimate an extremely massive host galaxy $(\mathrm{log}{M}_{\star }=11.92\pm 0.5{M}_{\odot})$ hosting a powerful, growing supermassive black hole (L Bol = 4-12x × 1046 erg s-1). This source represents the farthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs.