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Article Contents

TITLE PAGE

PREFACE

1.INTRODUCTION

2.OPTICAL OBSERVATIONS

2.1.Catalogs

2.2.Redshifts

2.3.Richness-the number of galaxies in a cluster

2.4.Luminosity function of galaxies

2.5.Morphological classification of clusters

2.6.Velocity distribution of galaxies

2.7.Spatial distribution of galaxies

2.8.Cluster masses-the missing mass problem

2.9.Dynamics of galaxies in clusters

2.9.1.Two-body relaxation

2.9.2.Violent relaxation

2.9.3.Ellipsoidal clusters

2.9.4.Dynamical friction

2.10.Galactic content of clusters

2.10.1.cD galaxies

2.10.2.Proportion of spiral, S0, and elliptical galaxies

2.11.Extensions of clustering

2.11.1.Poor clusters

2.11.2.Superclusters and voids

3.RADIO OBSERVATIONS

3.1.General radio properties

3.2.Correlations between X-ray and radio emission

3.3.Head-tail and other distorted radio structures

3.4.Cluster radio haloes

3.5.Cosmic microwave diminution (Sunyaev-Zel'dovich effect)

3.6.Faraday rotation

3.7.21 cm line observations of clusters

4.X-RAY OBSERVATIONS

4.1.Detections and identifications

4.2.X-ray luminosities and luminosity functions

4.3.X-ray spectra

4.3.1.Continuum features in the spectrum

4.3.2.Line features-the 7 keV iron line

4.3.3.Lower energy lines

4.4.The spatial distribution of X-ray emission

4.4.1.X-ray centers, sizes, and masses

4.4.2.X-ray images of clusters and the morphology of the intracluster gas

4.5.Individual clusters

4.5.1.Coma

4.5.2.Perseus

4.5.3.M87/Virgo

4.5.4.A1367

4.6.X-ray-optical correlations

4.7.Poor clusters

4.8.High redshift clusters and X-ray cluster evolution

5.THEORETICAL PROGRESS

5.1.Emission mechanisms

5.1.1.Inverse Compton emission

5.1.2.Individual stellar X-ray sources

5.1.3.Thermal bremsstrahlung from intracluster gas

5.2.Ionization and X-ray emission from hot, diffuse plasma

5.2.1.Ionization equilibrium

5.2.2.X-ray emission

5.2.3.Resulting spectra

5.3.Heating and cooling of the intracluster gas

5.3.1.Cooling

5.3.2.Infall and compressional heating

5.3.3.Heating by ejection from galaxies

5.3.4.Heating by galaxy motions

5.3.5.Heating by relativistic electrons

5.4.Transport processes

5.4.1.Mean free paths and equilibration time-scales

5.4.2.Thermal conduction

5.4.3.Effects of the magnetic field

5.4.4.Viscosity

5.4.5.Diffusion and settling of heavy ions

5.4.6.Convection and mixing

5.5.Distribution of the intracluster gas-hydrostatic models

5.5.1.Isothermal distributions

5.5.2.Adiabatic and polytropic distributions

5.5.3.More complicated distributions

5.5.4.Empirical gas distributions derived by surface brightness deconvolution

5.5.5.Total masses and mass distributions in clusters-the hydrostatic method

5.5.6.Chemically inhomogeneous equilibrium models

5.6.Wind models for the intracluster gas

5.7.Cooling flows and accretion by cDs

5.7.1.Cooling flows

5.7.2.Accretion by central galaxies

5.7.3.Thermal instability and optical filamentation

5.7.4.Accretion-driven star formation

5.7.5.Cooling flow models with star formation

5.7.6.Evolution of cooling flows and active galaxies

5.8.X-ray emission from individual galaxies

5.8.1.Massive haloes around M87 and other central galaxies

5.8.2.Other models for M87 and other central galaxies

5.8.3.X-ray emission from noncentral cluster galaxies

5.9.Stripping of gas from galaxies in clusters

5.10.The origin and evolution of the intracluster medium

5.10.1.Infall models

5.10.2.Ejection from galaxies

6.PROSPECTS FOR THE FUTURE AND AXAF

REFERENCES