Intermediate-age Galactic open clusters: fundamental parameters of NGC 2627

PIATTI, ANDRÉS E.; CLARIA OLMEDO, JUAN JOSÉ; AHUMADA, A.V.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Año: 2003 vol. 346 p. 390 - 402

0035-8711

Charge-coupled device (CCD) photometry in the Johnson V, Kron-Cousins I and Washington CMT1 systems is presented in the field of the poorly known open cluster NGC 2627. Four independent Washington abundance indices yield a mean cluster metallicity of [Fe/H]=-0.12 +/- 0.08, which is compatible with the existence of a radial gradient in the Galactic disc. The resultant colour-magnitude diagrams indicate that the cluster is an intermediate-age object of 1.4 Gyr. Based on the best fits of the Geneva group's isochrones to the (V, V-I) and (T1, C-T1) diagrams, we estimate E(V-I) = 0.25 +/- 0.05 and V-MV= 11.80 +/- 0.25 for logt= 9.15, and E(C-T1) = 0.23 +/- 0.07 and T1-MT1= 11.85 +/- 0.25 for logt= 9.10, respectively, assuming solar metal content. The derived reddening value E(C-T1) implies E(B-V) = 0.12 +/- 0.07 and a distance from the Sun of 2.0 +/- 0.4 kpc. Using the WEBDA data base and the available literature, we re-examined the overall properties of all the open clusters with ages between 0.6 and 2.5 Gyr. We identified peaks of cluster formation at 0.7-0.8, 1.0-1.1, 1.6-1.7 and 2.0-2.1 Gyr, separated by relative quiescent epochs of ~0.2-0.3 Gyr. We also estimated a radial abundance gradient of -0.08 +/- 0.02, which is consistent with the most recent determinations for the Galactic disc, but no clear evidence for a gradient perpendicular to the Galactic plane is found.