Annu. Rev. Astron. Astrophys. 2000. 38: 761-814 Copyright © 2000 by Annual Reviews. All rights reserved

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Abstract. More than a decade ago the IRAS satellite opened the realm of external galaxies for studies in the 10 to 100 µm band and discovered emission from tens of thousands of normal and active galaxies. With the 1995-1998 mission of the Infrared Space Observatory ¹, the next major steps in extragalactic infrared astronomy became possible: detailed imaging, spectroscopy, and spectrophotometry of many galaxies detected by IRAS, as well as deep surveys in the mid- and far-IR. The spectroscopic data reveal a wealth of detail about the nature of the energy source(s) and about the physical conditions in galaxies. ISO's surveys for the first time explore the infrared emission of distant, high-redshift galaxies. ISO's main theme in extragalactic astronomy is the role of star formation in the activity and evolution of galaxies.

Table of Contents

INTRODUCTION: From IRAS to ISO

NORMAL GALAXIES

Infrared Emission from Normal Galaxies

Mid-Infrared Emission: Unidentified Bands and Very Small Dust Grains

Far-IR Emission: Cold Dust and Galactic Extinction

Dark Matter in the Halos and Outer Parts of Disks

Early-Type Galaxies

ACTIVE GALAXIES

Analytical Spectroscopy and Spectrophotometry

Molecular Spectroscopy

Distinguishing AGNs and Starbursts: ISO Diagnostic Diagrams

Starburst Galaxies

The Dark Side of Star Formation

Properties and Evolution of Starbursts

The [CII] Line as Global Tracer of Star Formation Activity in Galaxies

Seyfert Galaxies and QSOs

UIB Features in Seyfert Galaxies: Confirmation of Unified Models

The Source of Far-Infrared Luminosity in Seyfert Galaxies and QSOs

Re-constructing the Big Blue (EUV) Bump

The Nature of Ultra-Luminous Infrared Galaxies

Signature for AGN versus Starburst Activity: The ISO Diagnostic Diagram

ULIRGs as a Class: The Starburst-AGN Connection

Hidden AGNs: The Role of Dust Obscuration in ULIRGs

Properties and Evolution of Star Formation in ULIRGs

Warm ULIRGs and QSOs

THE DISTANT UNIVERSE

Mid-Infrared Surveys

Source Counts: Evidence for Strong Evolution

Nature of ISOCAM Sources: Luminous Star-Forming Galaxies at z ~ 0.7

Far-Infrared Surveys

Star Formation at High Redshift: A Synthesis

CONCLUSIONS AND OUTLOOK

REFERENCES

¹ The Infrared Space Observatory (ISO) is a project of the European Space Agency (ESA). The satellite and its instruments were funded by the ESA member states (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of the Japanese Space Agency ISAS and NASA. Back.