The globular cluster system of NGC1316. I. Wide-field photometry in the
  Washington system
  NGC 1316 (Fornax A) is a prominent merger remnant in the outskirts of the
Fornax cluster. The cluster system has not yet been studied in its entirety. We
therefore present a wide-field study of the globular cluster system of NGC
1316, investigating its properties in relation to the global morphology of NGC
1316. We used the MOSAIC II camera at the 4-m Blanco telescope at CTIO in the
filters Washington C and Harris R. We identify globular cluster candidates and
study their color distribution and the structural properties of the system. In
an appendix, we also make morphological remarks, present color maps, and
present new models for the brightness and color profiles of the galaxy. The
cluster system is well confined to the optically visible outer contours of NGC
1316. The color distribution of the entire sample is unimodal, but the color
distribution of bright subsamples in the bulge shows two peaks that, by
comparison with theoretical Washington colors with solar metallicity,
correspond to ages of about 2 Gyr and 0.8 Gyr, respectively. We also find a
significant population of clusters in the color range 0.8 < C-R < 1.1 which
must be populated by clusters younger than 0.8 Gyr, unless they are very
metal-poor. The color interval 1.3 < C-R < 1.6 hosts the bulk of
intermediate-age clusters which show a surface density profile with a sharp
decline at about 4 arcmin. The outer cluster population shows an unimodal color
distribution with a peak at C-R=1.1, indicating a larger contribution of old,
metal-poor clusters. Their luminosity function does not show the expected
turn-over, so the fraction of younger clusters is still significant. Cluster
formation in NGC 1316 has continued after an initial burst, presumably related
to the main merger. A toy model with two bursts of ages 2 Gyr and 0.8 Gyr is
consistent with photometric properties and dynamical M/L-values.
