A Discussion on astronomy in the ultraviolet - A study of interstellar lines in the rocket spectrum of δ Scorpii

Abstract

An analysis is made of ten interstellar lines in the vacuum ultraviolet spectrum of 8 Sco. The data were taken from a rocket spectrogram with wavelength coverage extending from 1177 to 1717 A with a resolution of approximately 0.15 A. Column densities of C°, C+, N°, 0°, A1+, Si+ and Fe+ are derived, from which abundances relative to atomic hydrogen are determined. Compared to corresponding solar abundances, silicon and iron are slightly overabundant whereas the remaining species are underabundant by factors of 1.8 to 8.6. It is shown that the relative Fe abundance may be made significantly less than the solar value by arbitrarily increasing the velocity dispersion of the Fe+ ions by a factor of 2. The relative populations of the carbon atoms ground state fine structure levels combined with two possible mean cloud temperatures of 47 and 76 K determined from the interstellar H 2 spectrum yield a mean cloud density of 250 and 150 cm-3 respectively. Using the appropriate column densities of neutral and singly ionized carbon atoms, the average ratio of the electron density at the hydrogen atom density for each temperature is found to be 2.1 x 10-4 and 4.8 x 10~2 *4 respectively.