The temperature of the circumgalactic and intergalatic medium over cosmic time

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In the early Universe, the intergalactic medium (IGM) is largely filled with diffuse hydrogen and helium gas. The IGM is distributed in a cosmic web of sheets and filaments, separated by voids. Galaxies form at the intersections of these structures and are fed by IGM gas falling onto regions surrounding galaxies called the circumgalactic medium (CGM). Principal Investigators Kim and Wakker will analyze archival data to study the complex interaction between gas accretion from the IGM and galactic outflows in the CGM, which controls star formation efficiency and mediates galaxy evolution. To broaden participation the PIs will organize a series of research related public talks and develop an online exhibit through the University of Wisconsin Space Place. The PIs will also continue to work with local middle and high schools to increase student participation in the annual Science Olympiad tournament.The PIs will estimate the temperature and turbulence of the diffuse CGM/IGM at 2z4 by determining the absorption line widths and column densities of HI, CIV and SiIV ions based on Voigt profile fitting analysis of ~170 QSO spectra from publicly archived Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) and the Ultraviolet and Visual Echelle Spectrograph (UVES) Spectral Quasar Absorption Database (SQUAD). The quasars span the epoch when the cosmic star formation rate triples between z ~ 4 and z ~ 2, and when helium reionization heats the IGM significantly at z ~ 3. The PIs will use their results to test theoretical models of the temperature-density relation of the CGM and the evolution of gas temperature and turbulence of the IGM/CGM at high redshifts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.