A Search For Warm-Hot Intergalactic Matter in the Local Sheet of Galaxies
Deneault, Ryan Scott
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30-40% of all baryons in the Universe are thought to reside in the warm-hot intergalactic medium (WHIM) at temperatures in the range of 10^5-10^7 K. If the oxygen abundance is comparable to expectations, then OVI absorption from the WHIM associated with the Local Sheet of galaxies should have been detected in background sources observed by the Far-Ultraviolet Spectroscopic Explorer (FUSE). FUSE spectra of targets spanning the entire sky have been examined to distinguish the WHIM in the Sheet from other sources. These observations suggest that the Sun is offset from the plane of the Local Sheet WHIM, defining a theoretical framework against which the data was compared. By looking for a correlation of the OVI absorption equivalent widths with latitude and comparing the results to hydrodynamical simulations, strong constraints have been placed on the properties of the WHIM. With a hydrogen number density equal to that predicted by the simulations, the upper limit to the oxygen abundance for the WHIM in the Local Sheet must be 0.05 ± 0.01 Z⊙. If instead a metallicity of 0.1 Z⊙ is adopted for the WHIM, the upper limit to the hydrogen number density must be 0.64 ± 0.02 times that predicted by the simulations.