| Issue |
A&A
Volume 417, Number 3, April III 2004
|
|
|---|---|---|
| Page(s) | 945 - 960 | |
| Section | Galactic structure, stellar clusters, and populations | |
| DOI | https://doi.org/10.1051/0004-6361:20035618 | |
| Published online | 26 March 2004 | |
Parameter properties and stellar population of the old open cluster NGC 3960 *,**
1
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, loredana@astropa.unipa.it
Received:
3
November
2003
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
© ESO, 2004
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