TY - JOUR
T1 - BVRI photometry of the galactic globular cluster NGC 6779
AU - Hatzidimitriou, D.
AU - Antoniou, V.
AU - Papadakis, I.
AU - Kaltsa, M.
AU - Papadaki, C.
AU - Papamastorakis, I.
AU - Croke, B. F.W.
PY - 2004/3/11
Y1 - 2004/3/11
N2 - We present B, V, R and I photometry for NGC 6779 (M56), a metal-poor globular cluster in the galactic halo. The observations were performed using the 1.3-m telescope at Skinakas Observatory, in Crete. The reddening of the cluster was found to be E(B - V) = 0.32 ± 0.02 [E(V - I) = 0.43 ± 0.02], significantly higher than previous estimates. The metal abundance of the cluster was derived from various parametrizations of red giant branch characteristics and it was found to be [Fe/H]ZW = -2.20 ± 0. 12 dex on the Zinn-West metallicity scale, or [Fe/H]CG = -2.00 ± 0.21 dex on the Carretta-Gratton scale. The distance modulus of the cluster is estimated to be (m - M)V = 15.62 ± 0.26 (or 14.62, if we correct for the reddening to the cluster). The horizontal branch of NGC 6779 shows a clear gap at (B - V)o = 0.0. Finally, the revised value for the metallicity of NGC 6779 led to a revision of its age to 13 Gyr, using the age-index calibrations of Salaris & Weiss.
AB - We present B, V, R and I photometry for NGC 6779 (M56), a metal-poor globular cluster in the galactic halo. The observations were performed using the 1.3-m telescope at Skinakas Observatory, in Crete. The reddening of the cluster was found to be E(B - V) = 0.32 ± 0.02 [E(V - I) = 0.43 ± 0.02], significantly higher than previous estimates. The metal abundance of the cluster was derived from various parametrizations of red giant branch characteristics and it was found to be [Fe/H]ZW = -2.20 ± 0. 12 dex on the Zinn-West metallicity scale, or [Fe/H]CG = -2.00 ± 0.21 dex on the Carretta-Gratton scale. The distance modulus of the cluster is estimated to be (m - M)V = 15.62 ± 0.26 (or 14.62, if we correct for the reddening to the cluster). The horizontal branch of NGC 6779 shows a clear gap at (B - V)o = 0.0. Finally, the revised value for the metallicity of NGC 6779 led to a revision of its age to 13 Gyr, using the age-index calibrations of Salaris & Weiss.
KW - Galaxies: haloes
KW - Globular clusters: individual: NGC 6779 (M56)
UR - http://www.scopus.com/inward/record.url?scp=1642294744&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2004.07439.x
DO - 10.1111/j.1365-2966.2004.07439.x
M3 - Article
SN - 0035-8711
VL - 348
SP - 1157
EP - 1163
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -