Far-infrared photometry of deeply embedded outflow sources

We present far-infrared maps and spectroscopy for a number of deeply embedded protostellar objects (Cep E, HH 211-MM, IC 1396 W, L 1157, L 1211, and RNO 15 FIR) from data that we acquired with the Infrared Space Observatory (ISO) photopolarimeter (PHOT) and Long Wavelength Spectrometer (LWS). Several previously undetected deeply embedded sources are found in the vicinity of our targets. We determine temperatures and luminosities of seven objects and locate them on an L b o l -T b o l diagram - the equivalent of a Hertzsprung-Russell diagram for protostars. Their masses and ages, according to their location on tracks taken from our evolutionary model, are derived. L 1211 and Cep E appear to be intermediate-mass objects which will reach final masses of about 3 M O ., whereas the other sources are in or below the solar mass range. The derived ages of 15 000 to 30000 yr are consistent with their current Class 0 state. A comparison of the luminosity of the associated outflows in the 1 - 0 S(1) line of molecular hydrogen with the source properties (bolometric luminosity, bolometric temperature and envelope mass) of 16 Class 0 sources shows no statistically significant correlations. Nevertheless, the data are consistent with a scheme in which the outflow strength and protostar evolve simultaneously. We show that the relationship is partially disguised, however, by the local properties of the surrounding material, the extinction and by short-term flux variability.