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Star Formation Feedback and Metal Enrichment History Of The Intergalactic Medium

Star Formation Feedback and Metal Enrichment History Of The Intergalactic Medium,Renyue Cen,Nora Elisa Chisari

Star Formation Feedback and Metal Enrichment History Of The Intergalactic Medium  
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Using the state-of-the-art cosmological hydrodynamic simulations we compute the metal enrichment history of the intergalactic medium (IGM). Overall, we show that galactic superwind feedback from star formation is able to transport metals to the IGM that matches a broad range of observations. We find (1) Evolution of mass densities contained in CIV and OVI lines is in agreement with observation. (2) The observed column density distributions for CIV and OVI in the range log N=12-15 are reproduced by the simulations. (3) Most CIV and OVI absorbers are located within shocked regions of elevated temperature (T>2E4K), overdensity (delta>=10), and metallicity ([Z]=[-2.5,-1.5]). (4) Most CIV and OVI absorbers, while clustered around galaxies on scales of <0.5Mpc, are transient and intergalactic in nature. (5) There is a trend that the population of CIV and OVI absorbers are more collisionally ionized at higher redshift. (6) While gravitational shocks from large-scale structure formation dominate the energy budget (80-90%) for turning about 50% of IGM to the warm-hot intergalactic medium (WHIM) by z=0, galactic superwind feedback shocks are energetically dominant over gravitational shocks at z>1-2. (7) Most of the so-called "missing metals" at z=2-3 are hidden in a warm-hot (T=10^{4.5-7}K) gaseous phase. (8) Approximately (37,46,10,7)% of the total metals at z=0 are in (stars, WHIM, X-ray gas, cold gas); the distribution stands at (23,57,2,18)% and (14,51,4,31)% at z=2 and z=4, respectively. (9) Neither CIV nor OVI absorbers coincide spatially with Lya clouds. (10) The mean metallicity of the IGM with moderate overdensities (1-10) shows a rapid increase with decreasing redshift, in direct conflict with the interpretation of observations at z=2-4 based on pixel optical depth (POD) method. We give an explanation for the disagreement.
Published in 2010.
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