Metal Enrichment in the Reionization Epoch

TL;DR

This paper reviews the role of early metal enrichment in the universe and its close connection to cosmic reionization, highlighting their combined importance in understanding the universe's evolution in the first billion years.

Contribution

It provides a pedagogical overview of how metal enrichment and reionization are interconnected during the early universe, emphasizing their significance in cosmic evolution.

Findings

Metal enrichment influences gas chemistry and star formation.

Early metals serve as tracers for energy deposition and environmental properties.

The joint study of metals and reionization is crucial for understanding the universe's evolution.

Abstract

The presence of elements heavier than helium ("metals") is of fundamental importance for a large number of astrophysical processes occurring in planet, star and galaxy formation; it also affects cosmic structure formation and evolution in several ways. Even a small amount of heavy elements can dramatically alter the chemistry of the gas, opening the path to complex molecules. Metals might enhance the ability of the gas to radiate away its thermal energy, thus favoring the formation of gravitationally bound objects; they can also condensate in a solid phase (dust grains), partly or totally blocking radiation from luminous sources. Finally, they represent useful tracers of energy deposition by stars and probe the physical properties of the environment by absorption or emission lines. Last, but certainly not least, life -- as we know it on Earth -- is tightly related to the presence of at least some of the heavy elements. In this pedagogical review I will concentrate on the connection between early metal enrichment and cosmic reionization. As we will see these two processes are intimately connected and their joint study might turn out to be fundamental in understanding the overall evolution of the Universe during the first billion years after the Big Bang, an epoch corresponding to redshifts z>6.