Unraveling the SMBH and its Nuclear Environment in NVSS J163547+362930 in the Early Universe

While there is a general consensus that active galactic nuclei (AGN) derive their power from a supermassive black hole (SMBH) accreting matter, the precise origins and evolution of these SMBHs in the first billion years after the Big Bang remain unclear. Detecting AGNs in this early cosmic epoch is challenged by their weak emission due to their remote distances. However, Blazars, a specific subset of AGN, exhibit an exceptional and fluctuating jet pointing towards us, detectable from radio frequencies to gamma-ray energies, making them invaluable tools for understanding the evolution of SMBHs and their host galaxies. One of these very rare sources, NVSS J163547+362930, at redshift z=3.65, allows us to study its emission processes, describing the physical mechanisms at work, and characterising its SMBH in the early universe. Using the particle propagation software JetSeT, employing a standard Shakura-Sunyaev disc (SSD), and assuming an initial particle distribution, we performed spectral energy distribution (SED) modelling, probing the effects of varying the black hole spin, ranging from non-rotating Schwarzschild black holes to the extreme Kerr variety. We found that a moderately spinning SMBH with a mass of M_BH~10^9 M_Sun governs the physics of the jet and that it likely evolved from a heavy seed. In the attempt of a consistency check, we verified the intrinsic correlation between the jet power and the accretion luminosity, in which the former appears to be weaker than the latter for high accretion efficiencies. Additionally, we properly related the gamma-ray emissions to external Comptonization processes related to a seed of photons in a dusty torus (DT) rather than a broad-line region (BLR). Finally, using the best-fit SED model, we find a consistent lower limit for the redshift of the source employing the Lyman alpha drop-out technique in a novel approach.