IISER MOHALI

Abstract: The gravitational collapse of the overdense regions in the initial densityfield leads to the formation of large scale structures in the Universe. Asignificant fraction of the diffuse gas is in the "Intergalactic Medium" (IGM)that is not associated with collapsed objects (galaxies). The IGM fills mostof the volume and exhibits a distinct filamentary structure that has imprintsof cosmological initial conditions and astrophysical processes of galaxyformation, reionization. High resolution Ly-alpha forest seen in the spectra ofdistant quasars together with the cosmological high resolution hydrodynamicalsimulations allow one to constrain cosmological and astrophysical parametersthat govern the physics of the IGM.\n\nIn this talk, I will outline our investigation into the thermal and ionizationstate of the IGM. Utilizing the observations of quasar absorption spectra fromthe UV (Hubble Telescope), the optical (Keck Telescope), and the near-infrared(Magellan II telescope), we have measured key parameters governing the physics of the IGM. Our analysis involves comparing the statistical properties of the Ly-alpha forest derived from observations with output of advanced hydrodynamical and radiative transfer simulations that I developed over several years. Our findings represent the most robust and consistent measurements to date, carefully accounting for all modeling and observational uncertainties. Notably, our results provide compelling evidence for late reionization, challenging earlier models proposing early reionization. These measurements hold significance in elucidating the free streaming length of dark matter. Finally,I will address currently unresolved issues within the IGM field and discuss theprospective roles of forthcoming telescopes such as WEAVE, TMT, and SKA inadvancing our understanding of both cosmology and astrophysics.\n\nMeeting ID: 990 2130 3795\nPasscode: 835769\n