The thermal history of the intergalactic medium |
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| Authors: | Joop Schaye † Tom Theuns Michael Rauch George Efstathiou Wallace LW Sargent |
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| Institution: | ;1Institute of Astronomy, Madingley Road, Cambridge CB3 0HA;2Max-Planck-Institut für Astrophysik, Postfach 1523, 85740 Garching, Germany;3European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany;4Astronomy Department, California Institute of Technology, Pasadena, CA 91125, USA |
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| Abstract: | At redshifts z ?2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Ly α forest. This photoheated gas follows a tight temperature–density relation which introduces a cut-off in the distribution of widths of the Ly α absorption lines ( b -parameters) as a function of column density. We have measured this cut-off in a sample of nine high-resolution, high signal-to-noise ratio quasar spectra and determined the thermal evolution of the intergalactic medium in the redshift range 2.0–4.5. At a redshift z ～3, the temperature at the mean density shows a peak and the gas becomes nearly isothermal. We interpret this as evidence for the reionization of He ii . |
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| Keywords: | intergalactic medium quasars: absorption lines cosmology: miscellaneous |
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