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Title: THE GLOBULAR CLUSTER NGC 6402 (M14). I. A NEW BV COLOR-MAGNITUDE DIAGRAM

We present BV photometry of the Galactic globular cluster NGC 6402 (M14), based on 65 V frames and 67 B frames, reaching two magnitudes below the turnoff level. This represents, to the best of our knowledge, the deepest color-magnitude diagram (CMD) of NGC 6402 available in the literature. Statistical decontamination of field stars as well as differential reddening corrections are performed in order to derive a precise ridgeline and hence physical parameters of the cluster. We discuss previous attempts at deriving a reddening value for the cluster, and argue in favor of a value E(B - V) = 0.57 {+-} 0.02, which is significantly higher than indicated by either the Burstein and Heiles or Schlegel et al. (corrected according to Bonifacio et al.) interstellar dust maps. Differential reddening across the face of the cluster, which we find to be present at the level of {Delta}E(B - V) Almost-Equal-To 0.17 mag, is taken into account in our analysis. We measure several metallicity indicators based on the position of the red giant branch (RGB) in the cluster CMD. These give a metallicity of [Fe/H] = -1.38 {+-} 0.07 on the Zinn and West scale and [Fe/H] = -1.28 {+-} 0.08 on themore » new Carretta et al. (UVES) scale. We also provide measurements of other important photometric parameters for this cluster, including the position of the RGB luminosity function ''bump'' and the horizontal branch morphology. We compare the NGC 6402 ridgeline with that of NGC 5904 (M5) derived by Sandquist et al., and find evidence that NGC 6402 and M5 have approximately the same age to within the uncertainties, although the possibility that M14 may be slightly older cannot be ruled out.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. Pontificia Universidad Catolica de Chile, Departamento de Astronomia y Astrofisica, Av. Vicuna Mackenna 4860, 782-0436 Macul, Santiago (Chile)
  2. Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)
  3. Gemini Observatory, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
  4. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
Publication Date:
OSTI Identifier:
22136568
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 146; Journal Issue: 3; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COLOR; COSMIC DUST; DIAGRAMS; GALAXIES; LUMINOSITY; MORPHOLOGY; PHOTOMETRY; STAR CLUSTERS