Published in Space Science Reviews, Volume 134, Issue 1-4, pp. 51-70
astro-ph/0801.0977

For a PDF version of the article, click here.

SOFT X-RAY AND EXTREME ULTRAVIOLET EXCESS EMISSION FROM CLUSTERS OF GALAXIES

F. Durret 1, J. S. Kaastra 2, 3, J. Nevalainen 4, T. Ohashi 5 and N. Werner 2, 6


1 Institut d'Astrophysique de Paris, CNRS, UMR 7095, Université Pierre et Marie Curie, 98bis Bd Arago, F-75014 Paris, France durret@iap.fr
2 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, the Netherlands
3 Astronomical Institute, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
4
Observatory, P.O. Box 14, 00014 University of Helsinki, Finland
5 Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Tokyo 192-0397, Japan
6 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, NL - 3584 CA Utrecht, the Netherlands
Max Planck Institute für Astrophysik, Karl-Schwarzschild-Strasse 1, 85749, Garching, Germany


Abstract. An excess over the extrapolation to the extreme ultraviolet and soft X-ray ranges of the thermal emission from the hot intracluster medium has been detected in a number of clusters of galaxies. We briefly present each of the satellites (EUVE, ROSAT PSPC and BeppoSAX, and presently XMM-Newton, Chandra and Suzaku) and their corresponding instrumental issues, which are responsible for the fact that this soft excess remains controversial in a number of cases. We then review the evidence for this soft X-ray excess and discuss the possible mechanisms (thermal and non-thermal) which could be responsible for this emission.


Key words: Galaxies: clusters   X-ray: spectra


Table of Contents

INTRODUCTION

INSTRUMENTAL ISSUES
The Extreme Ultraviolet Explorer (EUVE) satellite
ROSAT PSPC
XMM-Newton EPIC
Chandra
Suzaku XIS

SOFT X-RAY EXCESS EMISSION BASED ON EUVE AND ROSAT PSPC DATA
The first objects with a soft X-ray excess discovered: Virgo (redshift z = 0.0038) and Coma (z = 0.0231)
Other clusters observed with EUVE and ROSAT

SOFT X-RAY EMISSION BASED ON XMM-NEWTON EPIC DATA
Continuum detections
Line emission detection

SOFT X-RAY EMISSION BASED ON SUZAKU OBSERVATIONS
Search for the soft excess in and around clusters
Abell 2218 (z = 0.1756)
Abell 2052
Other clusters

SOFT X-RAY EMISSION BASED ON CHANDRA OBSERVATIONS

DISCUSSION
Thermal models
Non-thermal models
Some problems and open questions

NOTE ADDED IN PROOF

CONCLUSIONS

REFERENCES

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