Cosmological Implications of the Infrared Background Radiation

Abstract

We review some exciting new observational developments in the infrared background (1 – 1000 µm). The Nagoya-Berkeley collaboration have made accurate measurements of the infrared background intensity between 100 and 1000 µm and have detected excess radiation, compared to a 2.74 K blackbody, peaking at 700 µm. New detailed studies of the IRAS background data show the clear possibility of a cosmological background at 100 µm, though there is still not a concensus on the correct model for the foreground zodiacal emission. Finally, the Nagoya group claim a significant background intensity at 2 µm. Possible interpretations of the far infrared background as radiation from starburst galaxies undergoing strong cosmological evolution are discussed. The spectrum of the 700 µm excess does not agree well with such a model. More promising are models involving a pregalactic generation of stars which make dust and light. The expected infrared background from a variety of pregalactic sources (primeval galaxies, Population III stars, accreting black holes, large-scale structure formation, decaying elementary particles) are discussed in detail. These backgrounds would generally appear in the near infrared unless they have been absorbed by galactic or intergalactic dust, in which case they should have been reprocessed to the far infrared.