Infrared background constraints on the evolution of IRAS galaxies.

Source counts and redshift surveys at 60 microns provide clear evidence of cosmological evolution of the spiral galaxy population. Preliminary results from the COBE mission and recent reanalysis of the IRAS background data provide interesting constraints on these evolutionary models. For pure density evolution at the rate needed for consistency with the source counts and redshift surveys, the 60-500 micron background limits imply that there must be a redshift cut-off (Z_max_) at Z_max_<=2. For luminosity evolution, on the other hand, the predicted background is well below the currently available background limits for Z_max_ ~5.