James Webb Space Telescope Feed Post

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

Paper 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 (f1.28 GHz ~ 2 mJy, q24 µm = -1.1, a1.28-3 GHz = - 1.2, ?a = - 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}_{-0.3}^{+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????? (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.