Published in Physics Reports, Volume 427, Issue 1,
p. 1-39, 2006.
For a PDF version of the article, click here.
astro-ph/0512549
Abstract: We review the X-ray spectra of the cores of clusters of galaxies. Recent high resolution X-ray spectroscopic observations have demonstrated a severe deficit of emission at the lowest X-ray temperatures as compared to that expected from simple radiative cooling models. The same observations have provided compelling evidence that the gas in the cores is cooling below half the maximum temperature. We review these results, discuss physical models of cooling clusters, and describe the X-ray instrumentation and analysis techniques used to make these observations. We discuss several viable mechanisms designed to cancel or distort the expected process of X-ray cluster cooling.
Table of Contents
INTRODUCTION
CLUSTERS OF GALAXIES
PHYSICS OF THE INTRACLUSTER MEDIUM
X-ray Emission from Collisional Plasmas
Magneto-hydrodynamics
Cooling flows
X-RAY INSTRUMENTATION AND OBSERVATIONAL
TECHNIQUES
X-ray Telescopes and their Relevance to
Clusters
Analysis Techniques
X-RAY SPECTRA OF COOLING CLUSTERS
Early Work on Imaging Observations
Early Work on Low Resolution Spectroscopy
Focal Plane Crystal Spectrometer
Reflection Grating Spectrometer Observations
Recent Spatially-resolved Spectro-photometric
Observations
Observations of Cataclysmic Variables
Definition of the Cooling Flow Problem
ARE COOLING FLOWS RULED OUT?
Cooled gas and star formation
HEATING
Heat conduction
Heating by a central radio source
Is the ICM turbulent?
Multiphase flows
Role of Magnetic Fields and Cosmic Rays
Feedback
Other heat sources and mechanisms
DISCUSSIONS
FUTURE WORK
REFERENCES