Mid and Far Infrared Surveys with ISO

Abstract

We present the results of the extragalactic surveys performed at 15 and 175 microns using the ISOCAM and ISOPHOT instruments on-board the Infrared Space Observatory (ISO). The number counts at both wavelengths present a strong evolution. The preliminary study of the individual galaxies responsible for this evolution suggest that more star formation was hidden by dust at redshifts around z=1-2 and imply that the population of luminous IR galaxies detected by IRAS in the local universe must have played a major role in the formation and evolution of galaxies and cannot be considered anymore as extreme and rare cases.

10 pages, 4 figures: Proceedings of Rencontres de Moriond, 13-20 March 1999, ``Building Galaxies: from the Primordial Universe to the Present'', ed F. Hammer, T. X. Thuan, V. Cayatte, B. Guiderdoni and J. Tran Thanh Van (Ed. Frontieres)