High-resolution Spectroscopic Studies of Diffuse Molecular Clouds
Steven FEDERMAN
Univ. of Toledo
Résumé :
High spectral resolution allows us to discern the number of clouds along the line of
sight, their kinematics, the relative importance of turbulent motions, and chemical
signatures, including isotope ratios. Three recently completed projects will be
described. Absorption from atomic and molecular gas toward stars in the Pleiades
provided details of the interaction between the cluster and interstellar material.
It appears that the UV radiation from the stars has heated the gas sufficiently that
CH+ was formed in observable quantitites. In another study based on UV measuremenrs
with HST on CO and with FUSE on H2, the trends between CO abundance and H2 were
examined, as was the fractionation between 12C16O and 13C16O. The third study
involved 12 and 13 isotopoloques of CH+ and CN and the rotational temperatures
12C14N and 13C14N. Here, we found that the 12CH+/13CH+ ratio appears to be
essentially constant within about a kpc of the Sun and that CN excitation
predomiantly arises from the Cosmic Background.
