An Empirically Based Model for Predicting Infrared Luminosity Functions, Deep Infrared Galaxy Counts, and the Diffuse Infrared Background

Abstract

We predict luminosity functions and number counts for extragalactic infrared sources at various wavelengths using the framework of our empirically based model. Comparisons of our galaxy count results with existing data indicate that either galaxy luminosity evolution is not much stronger than Q = 3.1, where L ∝ (1 + z)Q, or that this evolution does not continue beyond a redshift of 2. However, a derivation of the far-infrared background from COBE Diffuse Infrared Background Experiment data suggests a stronger evolution for the far-infrared emission, with Q > 4 in the redshift range between 0 and 1. We discuss several interpretations of these results and also discuss how future observations can reconcile this apparent conflict. We also make predictions of the redshift distributions of extragalactic infrared sources at selected flux levels, which can be tested by planned detectors. Finally, we predict the fluxes at which various future surveys will become confusion-limited.