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Issue A&A Volume 434, Number 3, May II 2005 Page(s) 801 - 809 Section Cosmology (including clusters of galaxies) DOI 10.1051/0004-6361:20040371

A&A 434, 801-809 (2005)
DOI: 10.1051/0004-6361:20040371

Constraining the thermal history of the warm-hot intergalactic medium

L. Zappacosta¹, R. Maiolino², A. Finoguenov³, F. Mannucci⁴, R. Gilli² and A. Ferrara<sup>5

1</sup>  Dipartimento di Astronomia e Scienza dello Spazio, Largo E. Fermi 2, 50125 Firenze, Italy
    e-mail: zappacos@nabhas.ps.uci.edu
²  Osservatorio Astrofisico di Arcetri Largo E. Fermi 5, 50125 Firenze, Italy
³  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
⁴  Istituto di Radioastronomia, Sezione di Firenze - CNR Largo E. Fermi 5, 50125 Firenze, Italy
⁵  SISSA/International School for Advanced Studies via Beirut, 4 34014 Trieste, Italy

(Received 2 March 2004 / Accepted 22 December 2004)

Abstract
We have identified a large-scale structure traced by galaxies at z=0.8, within the Lockman Hole, by means of multi-object spectroscopic observations. By using deep XMM images we have investigated the soft X-ray emission from the Warm-Hot Intergalactic Medium (WHIM) expected to be associated with this large-scale structure and we set a tight upper limit to its flux in the very soft 0.2-0.4 keV band. The non-detection requires the WHIM at these redshifts to be cooler than 0.1 keV. Combined with the WHIM emission detections at lower redshift, our result indicates that the WHIM temperature rapidly decreases with redshift, as expected in popular cosmological models.

Key words: cosmology: large-scale structure of Universe -- X-rays: diffuse background -- galaxies: intergalactic medium -- galaxies: distances and redshifts

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© ESO 2005

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