High-resolution observations of the interstellar 3302 Na I doublet and a discussion of the resulting Na I/Ca II ratios
Open Access
- 1 November 1992
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 259 (1) , 47-62
- https://doi.org/10.1093/mnras/259.1.47
Abstract
High-resolution (6 km s−1 FWHM) observations of the interstellar λ3302 Na i doublet towards 11 southern early-type stars are presented. The analysis has resulted in much more accurate Na i column densities than those obtained from earlier studies of the (fully saturated) Na D lines. The λ3302 lines have low radial velocities (−15 ≲ υlsr ≲ + 10 km s−1) and are much simpler than the Na D and Ca ii profiles towards the same stars, generally occurring at those velocities previously identified with diffuse molecular clouds. Analysis of the Na i/Ca ii ratios in these components indicates that δCa ≈ −3 to −4 in the molecular clouds, implying that most of the Ca has been adsorbed on to the surfaces of interstellar grains. Lower Ca depletions are found in the less dense (non-molecular) clouds which are responsible for the additional absorption observed in the Na D and Ca K lines at both high and low velocities.Keywords
This publication has 0 references indexed in Scilit: