U-band photometry of 17 WINGS clusters
  This paper belongs to a series presenting the WIde Field Nearby
Galaxy-cluster Survey (WINGS). The WINGS project has collected wide-field,
optical (B,V) and near-infrared (J,K) imaging, as well as medium resolution
spectroscopy of galaxies in a sample of 76 X-ray selected nearby clusters (0.04
< z < 0.07), with the aim of establishing a reference sample for evolutionary
studies of galaxies and galaxy clusters. In this paper we present the U-band
photometry of galaxies and stars in the fields of 17 clusters of the WINGS
sample. We also extend to a larger field of view the original B- and V-band
photometry (WINGS-OPT) for 9 and 6 WINGS clusters, respectively. We use both
the new and the already existing B-band photometry to get reliable (U-B) colors
of galaxies within three fixed apertures in kpc. To this aim, in the reduction
procedure we put particular care in the astrometric precision. Since not all
the observations have been taken in good transparency conditions, the
photometric calibration was partly obtained relying on the SDSS and WINGS-OPT
photometry for the U- and optical bands, respectively. We provide U-band (also
B- and V-band, where possible) total magnitudes of stars and galaxies in the
fields of clusters. Just for galaxies, the catalogs also provide geometrical
parameters and carefully centered aperture magnitudes. The internal consistency
of magnitudes has been checked for clusters imaged with different cameras,
while the external photometric consistency has been obtained comparing with the
WINGS-OPT and SDSS surveys. The photometric catalogs presented here add the
U-band information to the WINGS database for extending the SED of the galaxies,
in particular in the UV wavelengths which are fundamental for deriving the SFR
properties.
