Dwarf spheroidal galaxy in Draco. IV. On the mean metal abundance and metal-abundance range of the red giant stars

Stetson, P B

doi:10.1086/112688

Title: Dwarf spheroidal galaxy in Draco. IV. On the mean metal abundance and metal-abundance range of the red giant stars

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Abstract

Different observational techniques have yielded conflicting estimates of the metal abundance of red giant stars in the dwarf galaxy in Draco. Spectrophotometry of Draco giants by Zinn (Astrophys. J. 225, 790 (1978)) has been interpreted as implying not only a mean metallicity significantly higher than that found by a variety of other techniques, but also a range of a factor of 2 to 4 in the observed metal abundance within Draco. However, recent photographic photometry of stars in Draco (Stetson, Astron. J. 84, 1149 (1979)) has failed to find any evidence that subgiants in the system display the range of temperatures that would be expected from such a large spread of initial metal abundance. Therefore a reinvestigation of Zinn's spectrophotometry, in comparison with a large body of similar data obtained by Searle and Zinn (Astrophys. J. 225, 357 (1978)) for many globular clusters, has been undertaken to see whether such a high mean metallicity and such a large metallicity range are unambiguously required by these data. The two primary conclusions of this study are: (1) Draco probably differs from the clusters in some important, discrete manner. This means that secondary observational parameters which are correlated with metal abundance in normalmore »« less

Authors:: Stetson, P B

Publication Date:: Tue Apr 01 00:00:00 EST 1980

Research Org.:: Yale University Observatory, New Haven, Connecticut 06520

OSTI Identifier:: 5363903

Resource Type:: Journal Article

Journal Name:: Astron. J.; (United States)

Additional Journal Information:: Journal Volume: 85:4

Country of Publication:: United States

Language:: English

Subject:: 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; GALAXIES; ABUNDANCE; RED GIANT STARS; METALS; IRON; MAIN SEQUENCE STARS; SPECTROPHOTOMETRY; STAR CLUSTERS; STAR EVOLUTION; ELEMENTS; GIANT STARS; STARS; TRANSITION ELEMENTS; 640105* - Astrophysics & Cosmology- Galaxies

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                    Stetson, P B. Dwarf spheroidal galaxy in Draco. IV. On the mean metal abundance and metal-abundance range of the red giant stars.  United States: N. p., 1980. 
        Web.  doi:10.1086/112688.

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                    Stetson, P B. Dwarf spheroidal galaxy in Draco. IV. On the mean metal abundance and metal-abundance range of the red giant stars.  United States.  https://doi.org/10.1086/112688

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                    Stetson, P B. 1980.  
        "Dwarf spheroidal galaxy in Draco. IV. On the mean metal abundance and metal-abundance range of the red giant stars".  United States.  https://doi.org/10.1086/112688.

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@article{osti_5363903,

  title        = {Dwarf spheroidal galaxy in Draco. IV. On the mean metal abundance and metal-abundance range of the red giant stars},

  author       = {Stetson, P B},

  abstractNote = {Different observational techniques have yielded conflicting estimates of the metal abundance of red giant stars in the dwarf galaxy in Draco. Spectrophotometry of Draco giants by Zinn (Astrophys. J. 225, 790 (1978)) has been interpreted as implying not only a mean metallicity significantly higher than that found by a variety of other techniques, but also a range of a factor of 2 to 4 in the observed metal abundance within Draco. However, recent photographic photometry of stars in Draco (Stetson, Astron. J. 84, 1149 (1979)) has failed to find any evidence that subgiants in the system display the range of temperatures that would be expected from such a large spread of initial metal abundance. Therefore a reinvestigation of Zinn's spectrophotometry, in comparison with a large body of similar data obtained by Searle and Zinn (Astrophys. J. 225, 357 (1978)) for many globular clusters, has been undertaken to see whether such a high mean metallicity and such a large metallicity range are unambiguously required by these data. The two primary conclusions of this study are: (1) Draco probably differs from the clusters in some important, discrete manner. This means that secondary observational parameters which are correlated with metal abundance in normal globular clusters may not accurately predict the metallicity of Draco; the more direct measurements of metallic absorption features which are available for Draco giants suggest that the mean metallicity of Draco is more nearly that of M92 than that of M3. (2) There is indeed a spread of temperature and spectral properties on Draco's upper giant branch, but these resemble the differences found between the first-time giant and asymptotic giant stars in globular clusters, and thus do not necessarily imply a range of initial metal abundance. Other, more tentative conclusions about the physical properties of evolving stars in Draco are also briefly discussed.},

  doi          = {10.1086/112688},

  url          = {https://www.osti.gov/biblio/5363903},
  journal      = {Astron. J.; (United States)},
number       = ,

  volume       = 85:4,

  place        = {United States},

  year         = {Tue Apr 01 00:00:00 EST 1980},

  month        = {Tue Apr 01 00:00:00 EST 1980}

}

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