Infrared fine-structure lines at high redshift

Understand

Infrared (IR) fine-structure line (FSL) emission arises from the radiative de-excitation of collisionally-excited electrons in atoms and ions.

• Thanks to their high luminosities and relatively simple physics, IR FSLs have quickly become the workhorse for studying the formation and evolution of galaxies in the nearby and distant Universe.
• In this review, we introduce the physics of FSL emission and the diagnostics of the ISM that we can derive from them via first principle arguments.
• We summarize the history of FSL observations with a focus on the far-IR wavelengths and a particular emphasis on the on-going efforts aimed at characterizing galaxies at cosmic noon and beyond.