WIDE FIELD NEAR-INFRARED PHOTOMETRY of 12 GALACTIC GLOBULAR CLUSTERS: OBSERVATIONS VERSUS MODELS on the RED GIANT BRANCH

Roger E. Cohen, Maren Hempel, Francesco Mauro, Douglas Geisler, Javier Alonso-Garcia, Karen Kinemuchi

Resultados de investigaciones: Article

9 Citas (Scopus)

Resumen

We present wide field near-infrared (near-IR) photometry of 12 Galactic globular clusters, typically extending from the tip of the cluster red giant branch (RGB) to the main sequence turnoff. Using recent homogenous values of cluster distance, reddening and metallicity, the resulting photometry is directly compared to the predictions of several recent libraries of stellar evolutionary models. Of the sets of models investigated, Dartmouth and Victoria- Regina models best reproduce the observed RGB morphology, albeit with offsets in J - KS color which vary in their significance in light of all sources of observational uncertainty. Therefore, we also present newly recalibrated relations between near-IR photometric indices describing the upper RGB versus cluster iron abundance as well as global metallicity. The influence of enhancements in alpha elements and helium are analyzed, and we find that the former affect the morphology of the upper RGB in accord with model predictions. Meanwhile, the empirical relations we derive are in good agreement with previous results, and minor discrepancies can likely be attributed to differences in the assumed cluster distances and reddenings. In addition, we present measurements of the horizontal branch (HB) and RGB bump magnitudes, finding a non-negligible dependence of the near-IR HB magnitude on cluster metallicity. Lastly, we discuss the influence of assumed cluster distances, reddenings and metallicities on our results, finding that our empirical relations are generally insensitive to these factors to within their uncertainties.

Idioma originalEnglish
Número de artículo176
RevistaAstronomical Journal
Volumen150
Número6
DOI
Estado de la publicaciónPublished - 1 dic 2015
Publicado externamente

    Huella digital

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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