The evolution of the warm-hot intergalactic medium in a hierarchically evolving Universe
Final Report Abstract
Using cosmological simulations and quasar absorption-line spectroscopy we have investigated the properties of the warm-hot intergalactic medium (WHIM) and its evolution from high to low redshifts. Cosmological simulations indicate that this high-temperature gas phase of the intergalactic medium (IGM) contains about 30 percent of the total baryon budget in the local Universe. The WHIM further may represent a reservoir of the metals produced in galaxies at high redshift. In this project we have studied the distribution of baryons and metals in the WHIM from z = 3 to z = 0 and have investigated the relation between warm-hot intergalactic gas and galactic structures at different epochs of the Universe. From a detailed analysis of synthetic absorption-line spectra from a set of cosmological simulation from the OWLS project we conclude that intervening O VI absorbers and broad Lyman α absorbers (BLAs) do not trace the bulk of the baryons in the WHIM, but rather indicate metal-enriched hot gas associated with (and probably ejected by) galaxies. In addition, absorption-line measurements of intervening O VI absorbers and BLAs at low and high redshift indicate the multi-phase nature of this circumgalactic hot gas component. These observational studies, that are based on data from the HST and the VLT, underline that a detailed understanding of the physical properties of this gas requires a careful ionization modeling of the individual gas phases and their tracer ions. In summary, our project has contributed to a better understanding of the absorption signatures of warm-hot gas in the intergalactic and circumgalactic medium and its role in the context of a hierarchically evolving Universe.
Publications
- (2007): Physical Properties, Baryon Content, and Evolution of the Lyα Forest: New Insights from High‐Resolution Observations at z ≲ 0.4. In: ApJ 658 (2), S. 680–709
Lehner, N., Savage, B.D., Richter, P., Sembach, K.R., Tripp, T.M., & Wakker, B.P.
(See online at https://doi.org/10.1086/511749) - (2008): A High‐Resolution Survey of Low‐Redshift QSO Absorption Lines: Statistics and Physical Conditions of O vi Absorbers. In: ApJS 177 (1), S. 39–102
Tripp, T.M., Sembach, K.R., Bowen, D.V., Savage, B.D., Jenkins, E.B., Lehner, N., & Richter, P.
(See online at https://doi.org/10.1086/587486) - 2008, SSRv 134, 405
Richter, P., Paerels, F.B.S., Kaastra, J.
- (2011). Absorption signatures of warm-hot gas at low redshift: O VI. Monthly Notices of the Royal Astronomical Society, 413(1), 190-212
Tepper-García, T., Richter, P., Schaye, J., Booth, C.M., Dalla Vecchia, C., Theuns, T., & Wiersma, R.P.C.
(See online at https://doi.org/10.1111/j.1365-2966.2010.18123.x)
