Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
2 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
3 Astrophysics Division - Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
Corresponding author: L. Prisinzano, firstname.lastname@example.org
Accepted: 18 December 2003
We present a photometric and astrometric catalogue of the open cluster NGC 3960, down to limiting magnitude , obtained from observations taken with the Wide Field Imager camera at the MPG/ESO 2.2 m Telescope at La Silla. The photometry of all the stars detected in our field of view has been used to estimate a map of the strong differential reddening affecting this area. Our results indicate that, within the region where the cluster dominates, the values range from 0.21 up to 0.78, with () at the nominal cluster centroid position; color excesses up to 1 mag have been measured in the external regions of the field of view where field stars dominate. The reddening-corrected color-magnitude diagram (CMD) allows us to conclude that the cluster has an age between 0.9 and 1.4 Gyr and a distance modulus of . In order to minimize field star contamination, their number has been statistically subtracted based on the surface density map. The empirical cluster main sequence has been recovered in the V vs. and in the J vs. planes, using optical and infrared data, respectively. From these empirical cluster main sequences, two samples of candidate cluster members were derived in order to obtain the luminosity distributions as functions of the V and J magnitudes. The Luminosity Functions have been transformed into the corresponding Mass Functions; for , the two distributions have been fitted with a power law of index and in V and in J, respectively, while the Salpeter Mass Function in this notation has index .
Key words: Galaxy: open clusters and associations: individual: NGC 3960 / techniques: photometric / astrometry / stars: luminosity function, mass function
Based on observations made with the European Southern Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility.
© ESO, 2004