Assigned ID: 378 ----- Attempting Submission 1 (Fri Feb 26 16:04:45 GMT 2010) ----- The total baryon content of the universe can be deduced both from observations of the cosmic microwave background, and the observed Deuterium to Hydrogen ratio (D/H) through the theory of big-bang nucleosynthesis. Though observations can account for all of the baryons at high redshift, roughly half the baryons are referred to as``missing'' in the low redshift universe since they are not observed in known baryonic structures like galaxies, clusters, and the Lyman-alpha forest. Cosmological simulations predict that the missing baryons can be found in a cosmic web of sheets and filaments that thread the halos, in the ``warm-hot intergalactic medium'' (WHIM) phase (10^5 - 10^7K). The WHIM gas should be detectable in Ly-alpha or Ly-beta (10^4 K gas) and in shock-heated gas (10^5 - 10^6 K) in Ly-alpha and OVI absorption. Ultraviolet (UV) spectroscopy with the Far Ultraviolet Spectroscopic Explorer (FUSE) and HST has detected IGM absorbers in various metal species and HI along lines of sight to bright quasars that are likely associated with gas in the WHIM phase. This gas may account for the bulk of the missing baryons in the low redshift universe. Using Enzo hydro/N-body grid-based cosmology simulations, we will determine whether there is a unique interpretation given the current IGM absorber observations, and how new observations may provide strong tests of these theories. We propose to, with a suite of high-resolution Enzo simulations and novel analysis techniques, characterize the UV absorbers, and to model observational metrics to compare with the data. In particular, we study the metal diffusion throughout the IGM using various prescriptions for star formation, galaxy formation and thermaland chemical feedback, and study the numerical convergence of these algorithms.

QUASAR ABSORPTION LINES AND IGM 12 90000 false 0.0 0.0 false false false true false false SUPPORTED