Mon. Not. R. Astron. Soc., 378, 893-900 (2007/July-1)
CaFe interstellar clouds.
BONDAR A., KOZAK M., GNACINSKI P., GALAZUTDINOV G.A., BELETSKY Y. and KRELOWSKI J.
Abstract (from CDS):
A new kind of interstellar cloud is proposed. These are rare (just a few examples among ∼300 lines of sight) objects with the Cai 4227-Å, Fei 3720-Å and 3860-Å lines stronger than those of Ki (near 7699 Å) and Nai (near 3302 Å). We propose the name `CaFe' for these clouds. Apparently they occupy different volumes from the well-known interstellar Hi clouds where the Ki and ultraviolet Nai lines are dominant features. In the CaFe clouds we have not found either detectable molecular features (CH, CN) or diffuse interstellar bands which, as commonly believed, are carried by some complex, organic molecules. We have found the CaFe clouds only along sightlines toward hot, luminous (and thus distant) objects with high rates of mass loss. In principle, the observed gas-phase interstellar abundances reflect the combined effects of the nucleosynthetic history of the material, the depletion of heavy elements into dust grains and the ionization state of these elements which may depend on irradiation by neighbouring stars.