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Is there a composition gradient in the halo?

Published online by Cambridge University Press:  14 August 2015

Robert P. Kraft ,
Charles F. Trefzger  and
N. Suntzeff
Robert P. Kraft
Affiliation:
Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz
Charles F. Trefzger
Affiliation:
Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz
N. Suntzeff
Affiliation:
Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz

Extract

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We define “metals” as consisting of the elements at and near the Fe-peak, and review several methods by which the metal-abundance gradient of stars in the halo can be obtained. In the inner halo (galactocentric distance R ≲ 8 kpc), the Basel RGU photometry should allow the derivation of the shapes and dimensions of the iso-abundance contours. For the outer halo to R ∼ 30 kpc, we review techniques based on Δs-measurements of RR Lyraes (Lick) and intermediate band-pass photometry of globular-cluster giants (Searle and Zinn, Palomar). Both methods suggest little change in mean [Fe/H] between 10 and 30 kpc; however, both may be biased against the discovery of very metal-poor objects. The conclusion that the outer halo has no abundance gradient may be somewhat premature.

Type
VIII. THE SPHEROIDAL COMPONENT
Information
Symposium - International Astronomical Union , Volume 84: The Large-Scale Characteristics of the Galaxy , 1979 , pp. 463 - 474
Copyright
Copyright © Reidel 1979 

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