The thermal history of the intergalactic medium
Abstract
At redshifts z ≳ 2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Lyα forest. This photoheated gas follows a tight temperature–density relation which introduces a cut-off in the distribution of widths of the Lyα 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 ɪɪ.
Additional Information
© 2000 RAS. Received: 08 May 2000. Accepted: 14 June 2000. Published: 01 November 2000. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We would like to thank Bob Carswell for letting us use the spectrum of Q11002264 and for helping us with vpfit. We are also grateful to Sara Ellison for letting us use the HIRES spectra of APM 0827915255. We thank Martin Haehnelt, Lam Hui, Jordi Miralda-Escude and Martin Rees for stimulating discussions. JS thanks the Isaac Newton Trust, St. John's College and PPARC for support, WLWS acknowledges support from NSF under grant AST-9900733 and GE thanks PPARC for the award of a senior fellowship. Research was conducted in cooperation with Silicon Graphics/Cray Research utilizing the Origin 2000 supercomputer COSMOS, which is a UK-CCC facility supported by HEFCE and PPARC. This work has been supported by the TMR network on 'The Formation and Evolution of Galaxies', funded by the European Commission.Attached Files
Published - 318-3-817.pdf
Accepted Version - 9912432.pdf
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Additional details
- Eprint ID
- 103448
- Resolver ID
- CaltechAUTHORS:20200526-104631514
- Isaac Newton Trust
- St. John's College, Cambridge
- Particle Physics and Astronomy Research Council (PPARC)
- NSF
- AST-9900733
- European Commission
- W. M. Keck Foundation
- Created
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2020-05-27Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field