  We present surface photometry for the central regions of a sample of 48
spiral galaxies (mostly unbarred and barred of types Sbc or Sc) observed with
the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope.
Surface brightness profiles were derived and modeled with a Nuker law. We also
analyzed archival Wide Field Planetary Camera~2 images with a larger field of
view, available for 18 galaxies in our sample. We modeled the extracted bulge
surface brightness profiles with an exponential, a de Vaucouleurs or a Sersic
profile. In agreement with previous studies, we find that bulges of Sbc
galaxies fall into two categories: bulges well described by an exponential
profile and those well described by an de Vaucouleurs profile. Only one galaxy
requires the use of a more general Sersic profile to properly describe the
bulge. Nuclear photometrically distinct components are found in ~55% of the
galaxies. For those that we classify as star clusters based on their resolved
extent we find absolute magnitudes that are brighter on average than those
previously identified in spiral galaxies. This might be due to a bias in our
sample toward star forming galaxies, combined with a trend for star forming
galaxies to host brighter central clusters.
