Published in Space Science Reviews, Volume 134, Issue 1-4, pp. 25-49
astro-ph/0801.0975

For a PDF version of the article, click here.

FUV AND X-RAY ABSORPTION IN THE WARM-HOT INTERGALACTIC MEDIUM

P. Richter 1, F.B.S. Paerels 2 and J.S. Kaastra 3


1 Institut für Physik, Universität Potsdam, Am Neuen Palais 10, D-14469 Potsdam, Germany
prichter@astro.physik.uni-potsdam.de
2 Department of Astronomy and Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027, USA
3 SRON, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands


Abstract. The Warm-Hot Intergalactic Medium (WHIM) arises from shock-heated gas collapsing in large-scale filaments and probably harbours a substantial fraction of the baryons in the local Universe. Absorption-line measurements in the ultraviolet (UV) and in the X-ray band currently represent the best method to study the WHIM at low redshifts. We here describe the physical properties of the WHIM and the concepts behind WHIM absorption line measurements of H I and high ions such as O VI, O VII, and O VIII in the far-ultraviolet and X-ray band. We review results of recent WHIM absorption line studies carried out with UV and X-ray satellites such as FUSE, HST, Chandra, and XMM-Newton and discuss their implications for our knowledge of the WHIM.


Key words:galaxies: intergalactic medium; quasars: absorption lines; cosmology: large-scale structure of the Universe


Table of Contents

INTRODUCTION

PHYSICAL PROPERTIES OF THE WHIM
WHIM ionisation conditions
WHIM absorption signatures in the UV and X-ray band
The baryon content of the WHIM as measured by UV and X-ray absorbers

UV MEASUREMENTS OF THE WHIM
Past and present UV instruments
Intervening WHIM absorbers at low redshift
The Milky Way halo and Local Group gas

X-RAY MEASUREMENTS OF THE WHIM
Past and present X-ray instruments
Intervening WHIM absorbers at low redshift
The Milky Way halo and Local Group gas

ADDITIONAL ASPECTS
Results from numerical simulations
WHIM absorbers at high redshift
Concluding remarks

REFERENCES

Next