The following document lists the file abstract/JBALUTEA_ISM_V.abs
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SCIENTIFIC ABSTRACT It is now well accepted that systematic observations (of the survey type) are of great interest for the general astrophysics outcome. ISO offers a unique opportunity to completely explore the spectrum between 2.5 and 200 um at both unprecedented high sensitivity and spectral resolution, especially in the still unexplored gaps between the atmospheric windows. This opportunity has to be fully used given that many unexpected lines are likely to be discovered in the far infrared spectra of astronomical objects. We cannot rely on observing only lines (atomic and molecular) and solid state features that we already know about or expect to be seen. In this context we propose to observe selected bright astronomical source(s) over the spectral range covered by the ISO/LWS, from 45 to 196 um, in the high resolution Fabry-Perot mode. The main goal of this proposal is to detect new spectral features or lines with unexpected strength. In order to get the full capability of the ISO/LWS, Fabry-Perot spectra should be taken towards some of the brightest known infrared sources. Furthermore, since the proposed goal impose to obtain a very high signal to noise ratio (at least 100 seems mandatory) it might well be wisest to select only a limited number of objects probing in the best possible way the different phases associated with the interstellar medium. The detection of unexpected spectral features will prompt subsequent studies for the identification of the feature first, but also will need to elaborate a strategy, depending on the strenght ot the new feature, for follow-up observations. OBSERVATION SUMMARY In order to probe the different phases associated with the interstellar medium in only a very few lines of sight, the source(s) selection procedure is made to get both: i. an "emission" spectrum: the line of sight should probe characteristic regions of the interstellar medium exposed to a strong radiation field and sampling at least regions of ionised hydrogen, of photodissociation and with shocked gas. ii. an "absorption" spectrum: the line of sight should also probe interstellar material (molecules or solids) which remains protected from the radiation field (at least from its visible and ultraviolet parts) and hence traces highly processed material such as organic mantles on dust grains or volatile species such as ices. The source(s) should be chosen, naturally, among the brigthest objects in the infrared sky. Therefore "off-source" position are not required for the proposed programme.