Astrophysics & Particle Physics-APPC 2026

The intergalactic medium (IGM) is the diffuse, vast matter found between galaxies throughout the universe. Made up predominantly of ionized hydrogen, helium, and small amounts of heavier elements, the IGM plays an important part in the formation of cosmic structure, galaxy evolution, and the distribution of baryonic matter.The IGM is organized along the web of the cosmos, creating filaments, sheets, and voids tracing out the dark matter's gravitational scaffolding.

Gas in these structures is the reservoir from which galaxies accrete material, driving star formation and galactic growth.The IGM plays an essential role in galaxy formation and evolution since it governs the inflow of gas, the cooling of baryons, and chemical enrichment of the universe. Measurements with quasar absorption spectroscopy, X-ray telescopes, and radio surveys establish the physical properties, temperature, and chemical composition of the IGM.Cosmological simulations illustrate how the IGM evolves through interactions with galaxies over cosmic time, which controls the rates of star formation, feedback mechanisms, and large-scale structure growth. The study of the IGM also offers information about reionization, cosmic baryon distribution, and cosmic web evolution.Overall, the intergalactic medium (IGM) is the diffuse, widespread gas that permeates the region between galaxies. It is critical to know about galaxy formation, evolution, and chemical enrichment as well as large-scale structure in the universe.