SPECTRAL ENERGY OF FIRST PROTOSTELLAR CORES - DETECTING CLASS-I PROTOSTARS WITH ISO AND SIRTF

Radiative hydrodynamical models of protostellar collapse are used to c alculate the spectral energy distributions of single and binary protos tars at the phase of formation of the first (outer) protostellar core. In accordance with the established nomenclature, where classes 0, I, II, and III form a sequence in time, we term these pre-class 0 objects to be class-I (''class minus one'') objects. These class -I objects a re characterized by central core temperatures of similar to 200 K, env elope temperatures of similar to 10 K, and substantial far-infrared an d submillimeter-wave fluxes. While undetectable by IRAS, these objects should be detectable by ISO and SIRTF at 60 mu m and longer wavelengt hs. First protostellar cores exist for times on the order of a few per cent of the total collapse time, implying that a small fraction of all protostellar objects should be class -I objects.