High-resolution far-infrared studies of intermediate-mass pre-main-sequence objects

We have obtained high-resolution far-infrared maps of nine regions with 10 Herbig Ae/Be stars (intermediate-mass pre-main-sequence stars). Similar map s were obtained for 10 embedded IRAS sources with S-v(100 mu m) > S-v(60 mu m) and L similar to 200 L., which are possible evolutionary precursors of Herbig Ae/Be stars. Single far-infrared sources were found in most maps. Th e embedded sources have positions in agreement with those of the IRAS PSC, but some of the Herbig Ae/Be stars are offset significantly from the positi on of peak far-infrared emission. For all objects where it was possible to obtain 100 mu m flux densities, they are consistent with those observed by IRAS, but derived 50 mu m Aux densities are larger than expected. The far-i nfrared maps reveal that objects in at least 17 of 19 emission regions are significantly extended at the 30 "-40 " resolution of the Kuiper Airborne O bservatory at 100 mu m. Only sources associated with AB Aur and possibly IR AS 05338-0624 have unresolved far-infrared emission. Detailed analyses of t he flux densities and positions from our maps suggest the far-infrared emis sion in regions with Herbig Ae/Be stars may not immediately surround these stars in all cases. Instead, far-infrared emission from these objects may o riginate from dust heated externally by the Herbig stars, or from dust heat ed internally by other sources. For other objects arguably surrounded by fa r-infrared emission, the Herbig stars or embedded IRAS objects have similar mean deconvolved sizes (i.e., 0.10-0.15 pc), but possibly have different m ean deconvolved shapes (i.e., aspect ratios). Thus, far-infrared emission h ere may originate from flattened dust envelopes; the appearance of a far-in frared object as either a Herbig Ae/Be star or an embedded IRAS source may be merely a matter of viewing orientation.