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==> In this proposal, more time is being requested for DJAFFE.LVS.
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This proposal is a continuation of the OT proposal DJAFFE.LVS. The new proposal
focuses on very low-continuum outflows that had to be omitted from our earlier
observing program. The goals of this proposal are to characterize the physical
nature and emergent spectrum of low-velocity shocks (LVS), with shock speeds of
or below 20 km/s, in dense outflow-sources and to test models of MHD shocks in
the low-velocity range, where there are hitherto untested. High-velocity shocks
from protostellar outflows, HH objects, and SNR were subject of the Central
Programs. These observations, however, suffered in loss of sensitivity due to
the strong IR continuum of most sources, as they had to be performed with the
less sensitive Fabry-Perot (FP) or with low line-to-continuum (L/C) ratios in
the grating mode. There were, with exception of our proposal, no corresponding
plans to study shocks in the low-velocity range. LVS's are important as
signposts of injection and dissipation of turbulent energy in the dense ISM. The
current phase of our work concentrates on the issue of dissipation.
We shall examine a small sample of protostellar flows for which we selected a
set of diagnostic lines: the OI 63, 145 mu and some H2 rotational transitions.
H2 ro-vibrational lines and that of CII 157 mu will be observed to test for
high-velocity shock components and PDR contamination. We focus our attention on
oxygen-chemistry in shocked gas through observations of line emission of H2O,
OH, and O2. First ISO results showed that H2O, contrary to predictions, is NOT
always the most important coolant in shocks. We want to test this for LVS's. Our
targets have been chosen to avoid regions with high-velocity shocks, strong PDR
emission, or IR continuum radiation. They are far away from the driving sources.
Studies of the sources have shown they are nearby protostars with well-developed
outflows. We will point ISO at the snowplowed gas crashing into the ambient ISM
at modest shock speeds, far from the central sources. The results of our
previous proposal demonstrated that the proposed lines are detectable.