2025ApJ...990L..58L

Although supermassive black holes (SMBHs) are found at the centers of most galaxies today, over 300 have now been discovered at z > 6, including UHZ1 at z = 10.1 and GHZ9 at z = 10.4. They are thought to form when 10⁴ to 10⁵M_⊙ primordial stars die as direct-collapse black holes (DCBHs) at z ∼ 20-25. While studies have shown that DCBHs should be visible at birth at z ≳ 20 in the near-infrared (NIR) to the James Webb Space Telescope (JWST), none have considered SMBH detections at later stages of growth down to z ∼ 6-7. Here, we present continuum NIR luminosities for a black hole (BH) like ULAS J1120+0641, a 1.35 × 10⁹M_⊙ quasar at z = 7.1, from a cosmological simulation for Euclid, Roman Space Telescope (RST), and JWST bands from z = 6 to 15. We find that Euclid and RST could detect such BHs, including others like UHZ1 and GHZ9, at much earlier stages of evolution, out to z ∼ 14-15, and that their redshifts could be confirmed spectroscopically with JWST. Synergies between these three telescopes could thus reveal the numbers of SMBHs at much higher redshifts and discriminate between their evolution pathways because Euclid and RST can capture large numbers of them in wide-field surveys for further study by JWST.