Modelling the evolution of dusty starburst galaxies in multi-band deep surveys

We model the constraints set on the evolution of dusty starburst galaxies by the current deep extragalactic surveys performed in the far-infrared with Spitzer , and at radio wavelengths with the VLA. Our models fit the number counts in all the available spectral bands well, and also provide a reasonably close match to the redshift distribution of the Spitzer detections. We find: 1.) dusty starburst galaxies with infrared burst phases triggered by galactic interactions at redshift z ∼ 1− 2 are good candidates to fit the Spitzer results at 24μm, 70μm and 160μm, assuming plausible strengths for the PAH features for the infrared luminous sources. An Arp220-like spectral energy distribution (SED) for Ultraluminous Infrared Galaxies (ULIGs) of Lir > 10 L⊙ and one like that of M82 for Luminous Infrared Galaxies (LIGs) of Lir ∼ 10 11−12 L⊙ give a successful fit to the Spitzer 24μm and ISOCAM 15μm number counts at flux levels of Sν < 1mJy; 2.) the strong evolution of the number density of the ULIGs from redshift z ∼ 0 to ∼ 1 predicted by our models is consistent with the current deep 1.4GHz radio surveys and accounts for the upturn in the 1.4GHz differential counts at the submJy flux level; and 3.) comparing with number counts at near infrared bands, as well as the background measurements using DIRBE and 2MASS, shows that only a fraction of the stellar mass in the Universe is included in our models of dusty starburst mergers at z ∼ 1− 2. Subject headings: evolution-galaxies–interaction-galaxies–starburst-galaxies–Seyfert