Ionization equilibrium inside the rho Ophiuchi cloud
Technological developments in detectors have begun to provide optical absorption line measurements of material toward stars deeply embedded in dark clouds. Because of the importance of measuring depletions in these regions, this paper examines in detail the ionization balance of several commonly observed elements inside a sample dark cloud, the one associated with the rho Ophiuchi cloud. In particular, the ionization conditions are assessed for HD 147889, a star deeply embedded in this cloud, for which interstellar line data are becoming available. Data on electron densities are summarized, and the radiation field intensity is derived from the rotational excitation of H/sub 2/ molecules in the sigma Sco line of sight. While these factors remain somewhat uncertain, stringent limits can be placed on the ionization fractions, with the conclusion that for many elements, including calcium, the dominant stage at great depths in the cloud is the singly ionized state. Therefore, Ca ii measurements now available can be taken as indicators of the total calcium abundance and of calcium depletions.
- Research Organization:
- Laboratory for Atmospheric and Space Physics, Department of Astrophysics, University of Colorado
- OSTI ID:
- 5759558
- Journal Information:
- Astrophys. J.; (United States), Vol. 266:2
- Country of Publication:
- United States
- Language:
- English
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