Formation of the First Black Holes: Current observational status

TL;DR

This paper reviews the current observational evidence for the earliest supermassive black holes, highlighting key detections at high redshift and constraints from various surveys to inform formation theories.

Contribution

It provides a comprehensive overview of observational results on first black holes, including detections and upper limits across multiple wavelengths, aiding understanding of their formation.

Findings

Detection of z~6 supermassive black holes in major surveys

Constraints on early black hole populations from X-ray data

Summary of observational techniques and results

Abstract

In this chapter, we review the current observational status of the first supermassive black holes. It is clear that such a review can hardly be complete, due to the wealth of surveys that has been pursued, including different wavelengths and different observational techniques. This chapter will focus on the main results that have been obtained, considering the detections of z~6 supermassive black holes in large surveys such as SDSS, CFHQS and Pan-STARRS. In addition, we will discuss upper limits and constraints on the population of the first black holes that can be derived from observational data, in particular in the X-ray regime, as these provide additional relevant information for the comparison with formation scenarios.