Interstellar CA II absorption towards early-type stars at high galactic latitudes.
Abstract
New high resolution AAT and INT observations of the Ca II 3933 Å interstellar line towards nine early-type stars at high galactic latitudes are presented. These are combined with the authors' earlier AAT data to investigate the distribution of Ca II in the galactic halo. A comparison of these results with Ca II equivalent widths for extragalactic sightlines implies that there is a significant amount of this ion out to z ≅ 1 kpc, but not much beyond z ≅ 2 kpc. No coincident high velocity Ca II absorption is detected in the spectra of stars near known high velocity clouds (HVC). Although this may indicate that the HVCs are either at greater distances than the stars or have angular extents smaller than the separations of the stellar and HVC sightlines, it is also possible that they are nearby but contain too little Ca II to produce an observable absorption line.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1988
- Bibcode:
- 1988A&A...192..295K
- Keywords:
-
- Astronomical Coordinates;
- Calcium;
- Early Stars;
- Interstellar Extinction;
- Interstellar Gas;
- Absorption Spectra;
- Astronomical Spectroscopy;
- B Stars;
- Halos;
- Stellar Spectra;
- Astrophysics