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

Radiative hydrodynamical models of protostellar collapse are used to calculate the spectral energy distributions of single and binary protostars 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 are characterized by central core temperatures of similar to 200 K, envelope temperatures of similar to 10 K, and substantial far-infrared and submillimeter-wave fluxes. While undetectable by IRAS, these objects should be detectable by ISO and SIRTF at 60 mu m and longer wavelengths. First protostellar cores exist for times on the order of a few percent of the total collapse time, implying that a small fraction of all protostellar objects should be class -I objects.