THE DIAGNOSTIC POTENTIAL OF Fe LINES APPLIED TO PROTOSTELLAR JETS

We investigate the diagnostic capabilities of iron lines for tracing the physical conditions of shock-excited gas in jets driven by pre-main sequence stars. We have analyzed the 3000-25000 A, X-shooter spectra of two jets driven by the pre-main sequence stars ESO-H alpha 574 and Par-Lup 3-4. Non-local thermal equilibrium codes solving the equations of the statistical equilibrium along with codes for the ionization equilibrium are used to derive the gas excitation conditions of electron temperature and density and fractional ionization. The physical conditions derived from the iron lines are compared with shock models suggesting that the shock at work in ESO-H alpha 574 is faster and likely more energetic than the Par-Lup 3-4 shock. This work demonstrates that a multiline Fe analysis can be effectively used to probe the excitation and inonization conditions of the gas in a jet without any assumption on ionic abundances.