Interstellar Depletion Anomalies and Ionization Potentials
Abstract
Satellite observations indicate that (1) most elements are depleted from the gas phase when compared to cosmic abundances, (2) some elements are several orders of magnitude more depleted than others, and (3) these depletions vary from cloud to cloud. Since the most likely possibility is that the ‘missing’ atoms are locked into grains, depletions occur either by accretion onto core particles in interstellar clouds or earlier, during the period of primary grain formation. If the latter mechanism is dominant, then the most important depletion parameter is the condensation temperature of the elements and their various compounds. However, this alone is not sufficient to explain all the observed anomalies. It is shown that electrostatic effects—under a wide variety of conditions—can enormously enhance the capture cross-section of the grain. It is suggested that this mechanism can also account for such anomalies as the apparent ‘overabundance’ of the alkali metals in the gas phase.
- Publication:
-
Astrophysics and Space Science
- Pub Date:
- November 1979
- DOI:
- 10.1007/BF00648368
- Bibcode:
- 1979Ap&SS..66..161T
- Keywords:
-
- Anomalies;
- Depletion;
- Gas Ionization;
- Interstellar Gas;
- Ionization Potentials;
- Vapor Phases;
- Abundance;
- Alkali Metals;
- Condensing;
- Metal Vapors;
- Oao 3;
- Satellite Observation;
- Thermodynamic Equilibrium;
- Astrophysics