Lecture notes from the Summer School "Infrared Astronomy: Today and Tomorrow," held in Les Houches, August 1998. Editors F. Casoli and J. Lequeux.


NORMAL GALAXIES IN THE INFRARED

George Helou


Downs Lab, 320-47, California Institute of Technology, Pasadena, CA 91125, USA


Table of Contents

INTRODUCTION

THE STUDY OF NORMAL GALAXIES

GALAXIES IN THE INFRARED: THE IRAS ERA
Basic Parameters and Statistics
Infrared Luminosity
The Infrared-to-Blue Ratio
IRAS Colors
Other Estimators
Correlations
The Infrared-Radio Connection
The ``Two-Component Model''

ISO RESHAPES THE DUST CONTINUUM
ISO Surveys of Galaxies
Mid-Infrared Spectra
The Aromatic Features
The Mid-Infrared Continuum
High-Redshift Applications
Exceptions
The ISO-IRAS Color Diagram
The Global Infrared Spectrum
A Mid-Infrared Look Within Galaxies

A WALK IN THE LINE FOREST
Molecular Lines
Fine-Structure Lines
Interpreting the PDR Lines

MORE STUDIES

TOMORROW'S INFRARED GALAXIES
Challenges and Prospects
Suggestions

CONCLUSION

REFERENCES

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