Radio emission from the first quasars

Over 200 quasars have now been discovered at z> 6, including nine at z> 7. They are thought to form from the collapse of supermassive primordial stars to 104 - 105 M⊙ black holes at z∼ 20 - 25, which then rapidly grow in the low-shear environments of rare, massive halos fed by strong accretion flows. Sensitive new radio telescopes such as the Next-Generation Very Large Array (ngVLA) and the Square Kilometer Array (SKA) could probe the growth of these objects at much earliest stages than is now possible. Here, we estimate radio flux from the first quasars at z∼ 6 - 15 at 1 - 10 GHz. We find that a quasar with properties similar to that of ULAS J1120+0641, a 2.1 × 109 M⊙ black hole at z= 7.1, could be detected at up to z∼ 16 by the SKA and at z∼ 14 by the ngVLA. The advent of these new observatories, together with the James Webb Space Telescope (JWST), Euclid, and the Roman Space Telescope (RST), will inaugurate the era of z≲ 15 quasar astronomy in the coming decade.