Interpreting the Cosmic Infrared Background: Constraints on the Evolution of the Dust Enshrouded Star Formation Rate

Abstract

We present a detailed interpretation of the spectrum of the cosmic infrared background longwards of 5 microns and of galaxy counts from various surveys at mid-infrared, far-infrared and submillimeter wavelengths by evolving the mid-infrared local luminosity function with redshift. We find that all evolutionary models that fit the counts require a flattening at z~0.8 to avoid overproducing the CIRB. About 80% of the 140 micron CIRB is produced at 0 < z < 1.5 while only about 30% of the 850 micron background is produced within the same redshift range. The nature of the evolution is translated into a measure of the dust enshrouded star formation rate density as a function of redshift and compared with estimates from optical/near-infrared surveys. We find that the dust obscured star formation rate density appears to peak at z=0.8+/-0.1, much sooner than previously thought, with a value of 0.25+/-0.12 M_sun/yr and remains almost constant up to z~2. At least 70% of this star formation takes place in luminous infrared galaxies with L_IR > 10^11 L_sun. The long wavelength observations that constrain our evolutionary models do not strongly trace the evolution at z > 2 and a drop off in the dust enshrouded star formation rate is consistent with both the CIRB spectrum and the number counts. However, a comparison with the infrared luminosity function derived from extinction corrected optical/UV observations of the Lyman-break galaxy (LBG) population at z~3 suggests that the flat comoving star formation rate seen between redshifts 0.8 and 2, extends up to a redshift of z~4.