Breaks in surface brightness profiles and radial abundance gradients in
  the discs of spiral galaxies
  We examine the relation between breaks in the surface brightness profiles and
radial abundance gradients within the optical radius in the discs of 134 spiral
galaxies from the CALIFA survey. The distribution of the radial abundance (in
logarithmic scale) in each galaxy was fitted by simple and broken linear
relations. The surface brightness profile was fitted assuming pure and broken
exponents for the disc. We find that the maximum absolute difference between
the abundances in a disc given by broken and pure linear relations is less than
0.05 dex in the majority of our galaxies and exceeds the scatter in abundances
for 26 out of 134 galaxies considered. The scatter in abundances around the
broken linear relation is close (within a few percent) to that around the pure
linear relation. The breaks in the surface brightness profiles are more
prominent. The scatter around the broken exponent in a number of galaxies is
lower by a factor of two or more than that around the pure exponent. The shapes
of the abundance gradients and surface brightness profiles within the optical
radius in a galaxy may be different. A pure exponential surface brightness
profile may be accompanied by a broken abundance gradient and vise versa. There
is no correlation between the break radii of the abundance gradients and
surface brightness profiles. Thus, a break in the surface brightness profile
does not need to be accompanied by a break in the abundance gradient.
