Uncovering a Massive z ∼ 7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web
Erini Lambrides, M. Chiaberge, Arianna S. Long, Daizhong Liu, Hollis B. Akins, A. Ptak, I.T Andika, A. Capetti, Caitlin M. Casey, Jaclyn B. Champagne, Katherine Chworowsky, T. E. Clarke, Olivia R. Cooper, Xuheng Ding, Dillon Dong, Andreas L. Faisst, Jordan Forman, Maximilien Franco, Steven Gillman, G. Gozaliasl, Kirsten Hall, Santosh Harish, Christopher C. Hayward, Michaela Hirschmann, Taylor A. Hutchison, K. Jahnkę, 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 Robertson, Marko Shuntov, J. D. Silverman, M. Stiavelli, Benny Trakhtenbrot, E. Vardoulaki, Jorge A. Zavala, Natalie Allen, O. Ilbert, H. J. McCracken, Louise Paquereau, Jason Rhodes, Sune Toft
Abstract
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 μ m = −1.1, α 1.28−3 GHz = − 1.2, Δ α = − 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 > 10 23 cm −2 ). Using the wealth of deep UV to submillimeter photometric data, we report a singular solution photo- z of z phot = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>7.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and estimate an extremely massive host galaxy <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>11.92</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.5</mml:mn> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> hosting a powerful, growing supermassive black hole ( L Bol = 4−12x × 10 46 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.