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

January 2024 • 2024ApJ...961L..25L

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

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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2024ApJ...961L..25L
• PREPRINT http://arxiv.org/abs/2308.12823
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2024ApJ...961L..25L
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2024ApJ...961L..25L
• DATA https://doi.org/10.17909/ym93-d513
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2024ApJ...961L..25L
• ELECTR https://doi.org/10.3847%2F2041-8213%2Fad11ee