Interstellar Medium in High-Redshift Galaxies

The discovery of galaxies formed when the Universe was less than 1 Gyr old has been a major breakthrough of extragalactic astronomy. During this period, called Epoch of Reionization, the Universe experienced a dramatic change: from being a dark "sea" of neutral hydrogen and helium, it got completely reionized and polluted with elements heavier than helium. Thus, characterizing the bulk of galaxy population at these early epochs is pivotal because of their strong impact on the cosmic evolution.

Several fundamental questions are only partially answered: Are the first galaxies that appeared in the Universe similar to those observed at later epochs? What is the metal and dust content of high redshift galaxies? How much the metal abundance affects the physical conditions of the interstellar medium (ISM)? What are the thermal and dynamical properties of various gas phases of the ISM?

Theoretical models, building upon cosmological simulations (designed to follow, on Mpc scales, the galaxy formation) and including in post-processing the sub-kpc description of the heating, cooling and metal enrichment of the ISM, allow to answer these questions and to interpret observations with the state-of-the-art telescopes (e.g. ALMA, Hubble).