Abstract

Up to now, the epoch between 400,000 years and 1 billion years after the Big Bang is still largely “terra incognita”. With the formation of the first sources of radiation, stars and Black Holes (BH) this era saw what is often referred to as the transition from the dark ages to cosmic dawn. Despite the still rather scarce observational data, impressive progress has been made in understanding the physical properties of the earliest galaxies, and specifically of those possibly responsible for the reionization of the Universe. UV spectroscopic and photometric data have suggested for some time that these early galaxies host very young and metal poor stellar populations.

However, recent observing campaigns targeting the rest-frame far-IR have started to reveal a much more nuanced and complex situation, showing that a fraction of these galaxies must be already mature in terms of metal and dust enrichment. This conclusion is further strengthened by the increasing number of quasars that are being identified in large surveys, with more than 200 detected at z > 6.The very existence of rapidly accreting SMBHs at these redshift points to an early start of star formation that sets the conditions for the early assembly. In this talk, I will present some recent work attempting to provide a coherent scenario for the early assembly of the first galaxies and black holes and to prepare for the coming and future observational facilities in the electromagnetic and gravitational wave domain.