Uncovering a Massive z∼7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web

Erini Lambrides*, Marco Chiaberge, Arianna S. Long, Daizhong Liu, Hollis B. Akins, Andrew F. Ptak, Irham Taufik Andika, Alessandro Capetti, Caitlin M. Casey, Jaclyn B. Champagne, Katherine Chworowsky, Tracy E. Clarke, Olivia R. Cooper, Xuheng Ding, Dillon Z. Dong, Andreas L. Faisst, Jordan Y. Forman, Maximilien Franco, Steven Gillman, Ghassem GozaliaslKirsten R. Hall, Santosh Harish, Christopher C. Hayward, Michaela Hirschmann, Taylor A. Hutchison, Knud Jahnke, Shuowen Jin, Jeyhan S. Kartaltepe, Emma T. Kleiner, Anton M. Koekemoer, Vasily Kokorev, Sinclaire M. Manning, Crystal L. Martin, Jed McKinney, Colin Norman, Kristina Nyland, Masafusa Onoue, Brant E. Robertson, Marko Shuntov, John D. Silverman, Massimo Stiavelli, Benny Trakhtenbrot, Eleni Vardoulaki, Jorge A. Zavala, Natalie Allen, Olivier Ilbert, Henry Joy McCracken, Louise Paquereau, Jason Rhodes, Sune Toft

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

2 Downloads (Pure)


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 (f1.28 GHz ∼ 2 mJy, q24 μm = −1.1, α1.28−3 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 (NH > 1023 cm−2). Using the wealth of deep UV to submillimeter photometric data, we report a singular solution photo-z of zphot = 7.7-+0.30.4 and estimate an extremely massive host galaxy (log M* = 11.92 0.5M) hosting a powerful, growing supermassive black hole (LBol = 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.

Original languageEnglish
Article numberL25
JournalAstrophysical Journal Letters
Issue number1
Number of pages9
Publication statusPublished - 2024


  • Active galactic nuclei (16)
  • High-redshift galaxies (734)
  • Radio loud quasars (1349)
  • Reionization (1383)
  • Supermassive black holes (1663)
  • Unified Astronomy Thesaurus concepts: Quasars (1319)


Dive into the research topics of 'Uncovering a Massive z∼7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web'. Together they form a unique fingerprint.

Cite this