FAR-INFRARED LINE EMISSION FROM SHOCK HEATED GAS IN CEPHEUS A FABRY PEROT OBSERVATIONS OF OI AND HIGH-J CO EMISSIONS

we propose to observe farinfrared line emissions of co and oi from hot, shockheated gas in cepheus a (w). cepheus a (w) is a particularly favorable object in which to study shockheated interstellar gas, because it shows a very high ratio of shockexcited line emission to infrared continuum emission. the proposed observations would followup on earlier iso studies of shockexcited water and molecular hydrogen in that source. while the h2 line strengths measured in cepheus a (w) can be successfully accounted for by our model for the emission properties of magnetohydrodynamic shock waves (kaufman and neufeld 1996), our preliminary analysis of a search for shockexcited water that was carried out during rev. 220 (obsid.propiddneufeld.hotwater) suggests that the water rotational line strengths are considerably smaller than expected. at present it remains unclear whether the absence of strong water emission argues against a high water abundance in the warm shocked gas contradicting an important prediction of chemical models or whether the shock parameters invoked to explain the h2 emission are in error. the observations of highj co line emission and oi fine structure emission proposed here will provide valuable constraints upon the admixture of shock velocities and preshock densities present in cepheus a, allowing more reliable shock models to be constructed for this source and the implications of the water observations to be assessed more critically. we request a total of 18767 seconds to carry out lws fabryperot observations of six farinfrared rotational lines of co (j1615, j2221, j2827, j3130, j3433, and j3736) and of the two fine structure lines of oi (at 63 and 146 microns). truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]