Abstract

As the dominant reservoir of baryons in the Universe, the intergalactic medium (IGM) plays a crucial role in the history and evolution of cosmic structure. The stars and black holes in the first galaxies emitted copious amounts of ionizing radiation, singly ionizing hydrogen and helium at z~10, and later doubly ionizing Helium at z~3, thus reheating and reionizing the cosmos. The IGM evolves into the clumpy cosmic web, which is the source of gas that cools and accretes onto galaxies powering star-formation, and a sink for the metal enriched material, energy, and radiation which galaxies eject. The complex interplay of these processes determines the physical state of the intergalactic gas over cosmic time. Observations of absorption lines in quasar and galaxy spectra from the present until redshift 7 provide a thermal and chemical record of the IGM, enable precision measurements of density fluctuations and the geometry of the early Universe, and provide invaluable insights into the physical processes shaping galaxy formation. In the next few years, advances in telescope instrumentation, the emergence of massive spectroscopic surveys, as well as developments in theory and computation will deepen our understanding of the IGM as a probe of cosmology and the cosmic reionization events. This conference aims to bring together both theorists and observers working on the various astronomical passbands to discuss the latest developments in this exciting field.