Evidence for an old Galactic bulge from RR Lyrae stars in Baade's window - Implications for the formation of the Galaxy and the age of the universe

Recent abundance measurements of RR Lyrae variables in the Baade's window field of the Galactic nuclear bulge are examined, and the observed metallicity distributions of the RR Lyraes in different Galactic radial zones are compared with those predicted for the HB population models. It is shown...

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Bibliographic Details
Published in:The Astronomical journal 1992-11, Vol.104 (5), p.1780-1789
Main Author: Lee, Young-Wook
Format: Article
Language:English
Subjects:
Astronomy
Astrophysics
Characteristics and properties of the milky way
Earth, ocean, space
Exact sciences and technology
Stellar systems. Galactic and extragalactic objects and systems. The universe
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Summary:Recent abundance measurements of RR Lyrae variables in the Baade's window field of the Galactic nuclear bulge are examined, and the observed metallicity distributions of the RR Lyraes in different Galactic radial zones are compared with those predicted for the HB population models. It is shown that the observed systematic variation with Galactocentric distance is only explained if the age of the stellar population increases, in the mean, with decreasing R(G). Thus, the oldest stellar population, the RR Lyraes in the Galactic nuclear bulge, is indeed older than that in the halo.
ISSN:0004-6256
1538-3881
DOI:10.1086/116358