James Webb Space Telescope Feed Post

Uncovering a Massive z~7.65 Galaxy Hosting a Heavily Obscured Radio-Loud QSO Candidate in COSMOS-Web

Selection of Postage Stamp Images of the Candidate z ~ 7.65 RL Quasar, COSW-106725. Top row, from left to right: HSC-g, ACS F814W, JWST F115W, JWST F150W, JWST F277W and, JWST F444W, JWST MIRI F770W, ALMA 343 GHz and VLA 1.4 GHz. The ALMA extent is overlaid on each image (in white). The 3s upper-limits are reported for the non-detections. The upper left source in the UV/Optical/NIR images is a low-z interloper Weaver et al. (2022). Abstract: In this letter, we report the discovery of the highest redshift, heavily obscured, radio-loud QSO candidate selected using JWST NIRCam/MIRI, mid-IR, sub-mm, and radio imaging in the COSMOS-Web field. Using multi-frequency radio observations and mid-IR photometry, we identify a powerful, radio-loud (RL), growing supermassive black hole (SMBH) with significant spectral steepening of the radio SED (f1.32GHz~2 mJy, q24µm=-1.1, a1.32-3GHz=-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 QSO contribution to the UV/optical/NIR data and thus infer heavy amounts of obscuration (NH>1023 cm-2). Using the wealth of deep UV to sub-mm photometric data, we report a singular solution photo-z of zphot = 7.65+0.4-0.3 and estimate an extremely massive host-galaxy (logM?=11.92±0.06M?). This source represents the furthest known obscured RL QSO candidate, and its level of obscuration aligns with the most representative but observationally scarce population of QSOs at these epochs.