Astron. Astrophys. Suppl. Ser. 145, 451-465

Photometric catalog of nearby globular clusters

II. A large homogeneous (V,I) color-magnitude diagram data-base

A. Rosenberg ¹, A. Aparicio², I. Saviane³, and G. Piotto³

Send offprint request: A. Rosenberg, e-mail: alf@ll.iac.es

1 - Telescopio Nazionale Galileo, vicolo dell'Osservatorio 5, I-35122 Padova, Italy
2 - Instituto de Astrofisica de Canarias, Via Lactea, E-38200 La Laguna, Tenerife, Spain
3 - Dipartimento di Astronomia, Univ. di Padova, vicolo dell'Osservatorio 5, I-35122 Padova, Italy

Received February 24; accepted June 6, 2000

Abstract:

In this paper we present the second and final part of a large and photometrically homogeneous CCD color-magnitude diagram (CMD) data base, comprising 52 nearby Galactic globular clusters (GGC) imaged in the V and I bands.

The catalog has been collected using only two telescopes (one for each hemisphere). The observed clusters represent $75\%$ of the known Galactic globulars with $(m-M)_{V}\leq 16.15$ mag, cover most of the globular cluster metallicity range ( $-2.2 \leq {\rm [Fe/H]}\leq -0.4$), and span Galactocentric distances from $\sim1.2$ to $\sim18.5$ kpc.

In particular, here we present the CMDs for the 13 GGCs observed in the Northern hemisphere. The remaining 39 Southern hemisphere clusters of the catalog have been presented in a companion paper (Rosenberg et al. 2000). We present the first CCD color magnitude diagram for NGC 6779 (M 56).

All the CMDs extend from at least $\sim2$ magnitudes below the turn-off (i.e. $V_{\rm lim}\geq22$) to the tip of the red giant branch. The calibration has been done using a large number of standard stars, and the absolute calibration is reliable to a $\sim0.02$ mag level in both filters.

This catalog, because of its homogeneity, is expected to represent a useful data base for the measurement of the main absolute and relative parameters characterizing the CMD of GGCs.

Key words: astronomical data base: miscellaneous -- catalogs -- stars: Hertzsprung-Russell (HR) and C-M diagrams -- stars: population II -- globular clusters: general