Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Metal-Rich Globular Clusters of the Galaxy: Morphology of the Helium-Burning "Clump" and the Determination of Relative Ages Through the "Δ V" Method

M. Catelan and J. A. de Freitas Pacheco
Publications of the Astronomical Society of the Pacific
Vol. 108, No. 720 (1996 February), pp. 166-175
Stable URL: http://www.jstor.org/stable/40680699
Page Count: 10
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Metal-Rich Globular Clusters of the Galaxy: Morphology of the Helium-Burning "Clump" and the Determination of Relative Ages Through the "Δ V" Method
Preview not available

Abstract

Morphological aspects of the V, B-V diagram of metal-rich globular clusters are analyzed on the basis of stellar evolution models for horizontal-branch (HB) and red-giant-branch stars. These have been incorporated into detailed synthetic HB models, the influence of differential reddening upon which is also discussed. The synthetic HB models are found to be very clumpy in the color-magnitude diagram, though more extended structures occasionally result due to the effect of evolution away from the zero-age HB. In particular, "sloped" clumps may be naturally expected for sufficiently high helium abundances.Differential reddening is found to have a smaller influence than evolution itself upon the morphology of the clump. The synthetic HB models are also used to study the age difference between metal-rich clusters on the basis of the "Δ V" method. We emphasize the importance of knowing in advance the relative abundances of helium and metals in order to estimate this age difference quantitatively. We present chemical evolution models that serve to illustrate the effect, and show that, for two clusters of identical [Fe/H] and Δ V, the one enriched predominantly by ejecta from supernovae Type II explosions will appear younger than the other which also suffered enrichment from supernovae Type Ia ejecta. The implied locations of the red-giant-branch feature known as the "bump" are also discussed on the basis of recent observational and theoretical results. Our corresponding predictions should be checked against accurate observational data obtained with the Hubble Space Telescope.

Page Thumbnails

  • Thumbnail: Page 
166
    166
  • Thumbnail: Page 
167
    167
  • Thumbnail: Page 
168
    168
  • Thumbnail: Page 
169
    169
  • Thumbnail: Page 
170
    170
  • Thumbnail: Page 
171
    171
  • Thumbnail: Page 
172
    172
  • Thumbnail: Page 
173
    173
  • Thumbnail: Page 
174
    174
  • Thumbnail: Page 
175
    175