A comparison of interstellar Na I, Ca II, and K I absorption.
Abstract
The column densities of interstellar Na I, Ca ii, and K I derived from interferometric scans of the optical absorption lines are compared comprehensively with each other, and with distance d, reddening E(B - V), and hydrogen column density N(H I) derived from the La line. The quantities N(Na I), N(K I), N(H I), and E(B - V) are mutually well correlated, to better than a factor of 2. In contrast, the quantity N(Ca ii) is discrepant, showing a much poorer correlation with each of the prior quantities. This result may indicate appreciable variations in the apparently large depletion of calcium from the interstellar gas. Quantitative, nonlinear mean relations are established among the well-correlated quantities, and the resulting Na, K, and Ca abundances are estimated. Ionization of Na I by charge exchange with C ii seems negligible compared with photoionization. Subject headings: abundances - interstellar matter - line profiles
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1974
- DOI:
- 10.1086/152976
- Bibcode:
- 1974ApJ...191..381H