VLT-ISAAC spectroscopy of H_2 pure rotational lines: a new tool for investigating protostellar jets

摘要

We report 3-5 μm IR spectroscopy obtained with VLT-ISAAC on several protostellar jets. Together with H_2 emission lines from the v=1 rovibrational state, the spectra show several pure rotational lines of the fundamental state with excitation temperature up to ～ 22000 K. These observations represent the first detection from the ground of pure rotational (v=0) H_2 lines in jets. We show how theoretical rotation diagrams indicate these lines as unique both to probe the presence of collisionally excited gas in NLTE conditions and to infer the gas density.