© CAMBRIDGE UNIVERSITY PRESS 1999

1. INTRODUCTION

Clusters and superclusters of galaxies have been studied extensively both for their intrinsic properties and to investigate the dark matter in the universe, the baryon content of the universe, large-scale structure, evolution, and cosmology. For previous reviews see Zwicky (1957), Bahcall (1977, 1988, 1996), Oort (1983), Dressler (1984), Rood (1988), and Peebles (1993).

In these lectures I discuss the following topics and their implications for structure formation and cosmology.

Section 2:

Optical properties of galaxy clusters

Section 3:

X-ray properties of galaxy clusters

Section 4:

The baryon fraction in clusters

Section 5:

Cluster masses

Section 6:

Where is the dark matter?

Section 7:

The mass function of clusters

Section 8:

Quasar-cluster association

Section 9:

Superclusters

Section 10:

The cluster correlation function

Section 11:

Peculiar motions of clusters

Section 12:

Some unsolved problems

A Hubble constant of H₀ = 100h km s^-1 Mpc^-1 is used throughout.