Copyright © 1996 by Annual Reviews. All rights reserved
|
| Annu. Rev. Astron. Astrophys. 1996. 34:
749-792 Copyright © 1996 by Annual Reviews. All rights reserved |
For a PDF version of the article, click
here.
KEY WORDS: luminosity function, starbursts, active galactic nuclei,
molecular gas, dust emission
ABSTRACT. At luminosities above 1011 L
, infrared
galaxies become the dominant population of extragalactic objects in the
local
Universe (z 
0.3),
being more numerous than optically
selected starburst and Seyfert galaxies and quasi-stellar objects
at comparable bolometric luminosity. The trigger for the intense infrared
emission appears to be the strong interaction/merger of molecular gas-rich
spirals, and the bulk of the infrared luminosity for all but the most
luminous objects is due to dust heating from an intense starburst within
giant molecular clouds. At the highest luminosities
(Lir > 1012 L),
nearly all objects appear to be advanced mergers powered by a mixture
of circumnuclear starburst and
active galactic nucleus energy sources, both of which are fueled by
an enormous concentration of molecular gas that has been funneled into the
merger nucleus. These ultraluminous infrared galaxies may represent an
important stage in the formation of quasi-stellar objects and
powerful radio galaxies. They may also represent a primary stage
in the formation of elliptical galaxy cores, the formation of globular
clusters, and the metal enrichment of the intergalactic medium.
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