# The first Super Massive Black Holes: indications from models for future observations

## TL;DR

This paper uses advanced models and simulations to predict the detectability of early supermassive black holes and AGN during the Epoch of Reionization with upcoming telescopes like SKA and Athena.

## Contribution

It provides new estimates of SMBH and AGN detection rates at high redshifts and analyzes the impact of simulation parameters and SMBH spin on luminosity functions.

## Key findings

- Athena can observe over 5000 AGN per square degree at z=6-10.
- SKA can detect at least 400 AGN per square degree in the same redshift range.
- Detection of SMBHs at high redshift is influenced by simulation volume, initial conditions, and SMBH spin.

## Abstract

We present an exploration of the expected detection of the earliest Active Galactic Nuclei (AGN) in the Universe from state-of-art galaxy formation and evolution semi-analytic models and hydro-dynamical simulations. We estimate the number and radiative characteristics of Super Massive Black Holes (SMBHs) at $z\geq 6$, a redshift range that will be intensively explored by the next generation of telescopes, in particular in the radio through the Square Kilometre Array (SKA) and at high energies with ESA's Athena X-ray Observatory. We find that Athena will be able to observe over 5000 AGN/$\rm deg^2$ at the Epoch of Re-ionization (EoR), $6\leq z \leq 10$. Similarly, for the same redshift range the models/simulations suggest that SKA will detect at least 400 AGN/$\rm deg^2$. Additionally, we stress the importance of the volume of the simulation box as well as the initial physical conditions of the models/simulations on their effect on the luminosity functions (LFs) and the creation of the most massive SMBHs that we currently observe at the EoR. Furthermore, following the evolution of the accretion mode of the SMBHs in each model/simulation, we show that, while the quasar dominates over the radio mode at the EoR, detection at radio wavelengths still reaches significant numbers even at the highest redshifts. Finally, we present the effect that the radiative efficiency has on the LFs by comparing results produced with a constant value for the radiative efficiency and more complex calculations based on the spin of each SMBH.