Modeling the evolution of infrared luminous galaxies: the influence of   the Luminosity-Temperature distribution
  The evolution of the luminous infrared galaxy population is explored using a pure luminosity evolution model which incorporates the locally observed luminosity-temperature distribution for IRAS galaxies. Pure luminosity evolution models in a fixed $\Lambda$CDM cosmology are fitted to submillimeter (submm) and infrared counts, and backgrounds. It is found that the differences between the locally determined bivariate model and the single variable luminosity function (LF) do not manifest themselves in the observed counts, but rather are primarily apparent in the dust temperatures of sources in flux limited surveys. Statistically significant differences in the redshift distributions are also observed. The bivariate model is used to predict the counts, redshifts and temperature distributions of galaxies detectable by {\it Spitzer}. The best fitting model is compared to the high-redshift submm galaxy population, revealing a median redshift for the total submm population of $z=1.8^{+0.9}_{-0.4}$, in good agreement with recent spectroscopic studies of submillimeter galaxies. The temperature distribution for the submm galaxies is modeled to predict the radio/submm indices of the submm galaxies, revealing that submm galaxies exhibit a broader spread in spectral energy distributions than seen in the local IRAS galaxies. 
Geraint F. Lewis, Scott C. Chapman, George Helou