The Far-Infrared Luminosity Function from GOODS-North: Constraining the Evolution of Infrared Galaxies for z <= 1

We present the IR luminosity function derived from ultradeep 70 μm imaging of the GOODS-North field. The 70 μm observations are longward of the PAH and silicate features which complicate work in the MIR. We derive far-infrared luminosities for the 143 sources with S₇₀>2 mJy (S/N > 3 σ). The majority (81%) of the sources have spectroscopic redshifts, and photometric redshifts are calculated for the remainder. The IR luminosity function at four redshifts (z~0.28, 0.48, 0.78, and 0.97) is derived and compared to the local one. There is considerable degeneracy between luminosity and density evolution. If the evolving luminosity function is described as ρ(L, z)=(1+z)^qρ(L/(1+z)^p, 0), we find q=-2.19p+6.09. In the case of pure luminosity evolution, we find a best fit of p=2.78^+0.34_-0.32. This is consistent with the results from 24 μm and 1.4 GHz studies. Our results confirm the emerging picture of strong evolution in LIRGs and ULIRGs at 0.4<z<1.1, but we find no evidence of significant evolution in the sub-LIRG (L<10¹¹ L_solar) population for z<0.4.