SEARCH FOR H2 AND H3+ IR LINES ASSOCIATED WITH X-RAY SOURCES EMBEDDED IN MOLECULAR CLOUDS

we propose to study with the sws the interaction of xrays in the virgul 1 100 kev energy range with molecular gas. we use as xray candles welldefined xray sources recently discovered to be associated with molecular clouds: nearby (< 200 pc) lowmass pre main sequence stars (t tauri stars), without winds or outflows, and distant (virgul 10 kpc) microquasars. we want to detect 11 selected ir lines of h2 and h3+ in the 4 18 mum range. the expected line fluxes are proportional to the xray luminosity of the sources. they are typically low for embedded t tauri stars (virgul 10^17 w.m2), but detectable using the sws. for microquasars, provided they are also embedded in molecular clouds, the nominal expected fluxes are virgul 1000 times higher; even if fainter, the lines may be detected with a good snr in a few hundred seconds. we stress that to date little is known about the interaction of xrays with molecular gas. only a few h2 lines have been detected from the ground (e.g., in agns and molecular outflows), and h3+ has never been detected outside of the solar system. the h2 lines we select are predicted to be significantly stronger than those detectable on the ground. the general interest of the present proposal is threefold: (i) the h2 ir lines may be produced in a variety of conditions, but xray heating is predicted to carry a specific signature (line ratios) which has never been tested; (iii) even in welldefined physical conditions, the theoretical h2 line ratios are still uncertain; (iii) ionmolecule chemistry starts with h3+, and there is a lot of debate about its production rate from h2 with cosmic rays or xrays, and about its dissociative recombination rate. the proposed observations are expected to put for the first time clear constraints on these issues, and thus may have a strong impact on fundamental questions of interstellar chemistry. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]