Velocities and rotational excitation of interstellar H2 toward Pi Scorpii

Jenkins, E.B.; Lees, J.F.; Dishoeck, E.F. van; Wilcots, E.M. (1989)

Article / Letter to editor

A spectrum of Pi Sco showing numerous atomic lines and 70 absorption features from the Lyman and Werner transitions of interstellar H2 in rotational level J from zero to five is presented. Their shapes of the composite column density profiles are very nearly Gaussian with a one-dimensional rms velocity dispersion of 3 km/s. The behavior of shifts in the inferred N(H2) as a function of velocity are consistent with the overall profiles being composed of nearly symmetrical, tightly paced assemblies of about seven unresolved components. The relative overall column densities in the higher J levels of H2 are consistent with a model where these states are populated by optical pumping through the Lyman and Werner transitions, powered by UV radiation from nearby stars. The slight narrowing of the high-J profiles may be due to small clumps of H2 at radial velocities some 5-8 km/s from the core of the profile are exposed to a pumping flux about 10 times lower than that for the material near the profile's center.

• hydrogen
• interstellar gas
• molecular excitation
• rotational spectra
• absorption spectra
• line spectra
• stellar spectra
• ultraviolet spectra

• All authors: Jenkins, E.B.; Lees, J.F.; Dishoeck, E.F. van; Wilcots, E.M.
• Date: 1989
• Publisher: The American Astronomical Society