Astron. Astrophys. 363, 415-424 (2000)

Asphericity of galaxy clusters and the Sunyaev-Zel'dovich effect

D. Puy ^1,2, L. Grenacher ^1,2, Ph. Jetzer ^1,2 and M. Signore <sup>3

1</sup> Paul Scherrer Institute, Laboratory for Astrophysics, 5232 Villigen PSI, Switzerland
² University of Zürich, Institute of Theoretical Physics, Winterthurerstrasse 190, 8057 Zürich, Switzerland
³ Observatoire de Paris, Département de Radioastronomie Millimétrique, 61, Avenue de l'Observatoire, 75014 Paris, France

Received 27 July 2000 / Accepted 31 August 2000

Abstract

In this paper we investigate the Sunyaev-Zel'dovich (SZ) effect and the X-ray surface brightness for clusters of galaxies with a non-spherical mass distribution. In particular, we consider the influence of the shape and the finite extension of a cluster, as well as of a polytropic thermal profile on the Compton parameter, the X-ray surface brightness and on the determination of the Hubble constant. We find that the non-inclusion of such effects can induce errors up to 30% in the various parameters and in particular on the Hubble constant value, when compared with results obtained under the isothermal, infinitely extended and spherical shape assumptions.

Key words: galaxies: clusters: general cosmology: diffuse radiation

Send offprint requests to: puy@physik.unizh.ch

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Contents

• 1. Introduction
• 2. Basic equations of the SZ effect and the X-ray surface brightness for an ellipsoidal geometry
  • 2.1. Isothermal profile
• 3. Errors obtained in the quantities and
  • 3.1. Finite extension of clusters
  • 3.2. Polytropic index
  • 3.3. Geometrical effect
  • 3.4. Projection effect
• 4. Discussion and conclusions
• Acknowledgements
• Appendices
  • A: structure integral for the parameter
    • -ray surface brightness
  • B: projection effects on the parameter
    • -ray surface brightness
• References

© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000
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