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H. W. Yorke (Jet Propulsion Laboratory)
The detections and silhouetted imaging of disks around young objects in the visible and NIR have demonstrated the common occurrence of protostellar disks and their associated jets and outflows in star forming regions. In order to obtain quantitative information pertaining to earlier evolutionary phases of (proto-)stars and their disks, studies at longer wavelengths are necessary. Further progress in understanding the formation of stars + disks + planets is inhibited by our inability to make high spectrally and spatially resolved images in the principal cooling transitions: low excitation fine structure lines and molecular rotational transitions - many atmospherically blocked - as well as dust continuum emission in the FIR and submillimeter spectral regimes. Of particular interest for uniquely identifying and studying PAHs and the `pre-biotic' conditions in protoplanetary disks are the bending modes of large molecules which lie in the FIR/submillimeter regime.
The interactions of the (proto-)stars, possible close companions, mass infall, gaseous and dusty debris disks, jets and interstellar material in their close vicinity guarantee the occurrence of structure over a wide spectrum of spatial scales. Newly formed massive stars illuminate and begin to modify their immediate environment in a manner that is observable as the `PDR' phenomenon. Not only will the FIR/submillimeter continuum and line radiation from PDRs supply vital quantitative information on global star formation in extragalactic sources, but the careful analysis of observations of local PDRs on a much smaller scale - protostellar disks being photoionized and UV-photoheated by a nearby hot star - also tells us about the structure and evolution of these disks.
Using values (sensitivity, spectral and spatial resolution) believed attainable for space-based FIR/submillimeter interferometers within the next decade as well as on a longer time scale, the observability of these structures is discussed. It is concluded that there is a high potential for key scientific discoveries by instruments currently under consideration.
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