Abstract
We have detected absorption lines from the high-velocity cloud (HVC) complex WB in the spectrum of the star HE 1048+0231. This detection sets an upper limit on the distance to the cloud of 8.8-1.3+2.3 kpc. Nondetection (at greater than 3 σ confidence) in the star HE 1138-1303 at 7.7 ± 0.2 kpc sets a probable lower limit. The equivalent width of the Ca II K line due to the HVC [Wλ(Ca II K) = 114.6 ± 4.4 mÅ] corresponds to a column density of N(Ca II) = (1.32 ± 0.05) × 1012 cm-2. Using an H I spectrum from the Leiden/Argentine/Bonn survey, we calculate N(Ca II)/N(H I) = (81 ± 16) × 10-9. These distance limits imply an H I mass limit of 3.8 × 105 M⊙ < MHI < 4.9 × 105 M⊙. The upper distance limit imposed by these observations shows that this HVC complex has a probable Galactic or circumgalactic origin. Future metallicity measurements will be able to confirm or refute this interpretation.
Original language | English |
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Pages (from-to) | L97-L100 |
Journal | Astrophysical Journal |
Volume | 638 |
Issue number | 2 II |
DOIs | |
State | Published - Feb 20 2006 |
Bibliographical note
Funding Information:We are grateful to Rebecca Bernstein, Ian Thompson, and Steve Shectman for help with the MIKE spectrograph. We thank Scott Burles and Jason Prochaska for help with the MIKE Redux package. Thanks to Peter Kalberla for providing the LAB survey data before publication. Nathan DeLee participated in the WIYN observations, for which we are grateful. C. T. would like to thank Tuorla Observatory for its support and acknowledges travel support from the Australian Nuclear Science and Technology Organisation Access to Major Research Facilities Program. The financial support of the Australian Research Council is greatly appreciated. T. C. B. acknowledges partial support from NSF grants AST 04-06784 and PHY 02-16783.
Keywords
- Galaxy: Evolution
- Galaxy: Halo
- ISM: Clouds
- ISM: Individual (HVC complex WB)
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science