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Evidence for an old galactic bulge from RR Lyrae stars in Baade's window: the inside-out picture of galaxy formation

Published online by Cambridge University Press:  07 August 2017

Young-Wook Lee
Young-Wook Lee*
Affiliation:
Yale Astronomy Department, 260 Whitney Avenue, New Haven, CT 06511

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In their recent, high-quality spectroscopic observations of 59 RR Lyrae stars in Baade's window field of the Galactic nuclear bulge, Walker and Terndrup (1991) found that the metallicity distribution for their whole sample is sharply peaked at [Fe/H] = −1.0. Comparison of their data with the sample of halo RR Lyraes (Suntzeff et al. 1991) suggests that the metallicity at which the stellar population is most likely to form RR Lyraes increases with decreasing galactocentric distance.

The horizontal-branch (HB) model calculations indicate that this is what one would expect if the radial variation in HB morphology observed in the halo continues to the very center of the Galaxy. In particular, the observed peak of the bulge RR Lyrae abundance distribution at [Fe/H] = −1.0 can only be reproduced by the unique relationship between the HB type and [Fe/H] that is shifted to the right of the mean relationship for inner halo globular clusters (see Fig. 7a of Lee 1991).

Type
Poster Papers
Information
Symposium - International Astronomical Union , Volume 149: The Stellar populations of Galaxies , 1992 , pp. 446
Copyright
Copyright © Kluwer 

References

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