Homogeneous photometry VII. Globular clusters in the Gaia era
  We present wide-field, ground-based Johnson-Cousins UBVRI photometry for 48
Galactic globular clusters based on almost 90000 public and proprietary images.
The photometry is calibrated with the latest transformations obtained in the
framework of our secondary standard project, with typical internal and external
uncertainties of order a few millimagnitudes. These data provide a bridge
between existing small-area, high-precision HST photometry and all
sky-catalogues from large surveys like Gaia, SDSS, or LSST. For many clusters,
we present the first publicly available photometry in some of the five bands
(typically U and R). We illustrate the scientific potential of the photometry
with examples of surface density and brightness profiles and of
colour-magnitude diagrams, with the following highlights: (i) we study the
morphology of NGC 5904, finding a varying ellipticity and position angle as a
function of radial distance; (ii) we show U-based colour-magnitude diagrams and
demonstrate that no cluster in our sample is free from multiple stellar
populations, with the possible exception of a few clusters with high and
differential reddening or field contamination, for which more sophisticated
investigations are required. This is true even for NGC 5694 and Terzan 8, that
were previously considered as (mostly) single-population candidates.
