Stellar mass-to-light ratio gradients in galaxies: correlations with
  mass
  We analyze the stellar mass-to-light ratio (M/L) gradients in a large sample
of local galaxies taken from the Sloan Digital Sky Survey, spanning a wide
range of stellar masses and morphological types. As suggested by the well known
relationship between M/L ratios and colors, we show that M/L gradients are
strongly correlated with colour gradients, which we trace to the effects of age
variations. Stellar M/L gradients generally follow patterns of variation with
stellar mass and galaxy type that were previous found for colour and metallicty
gradients. In late-type galaxies M/L gradients are negative, steepening with
increasing mass. In early-type galaxies M/L gradients are shallower while
presenting a two-fold trend: they decrease with mass up to a characteristic
mass of \M* \sim 10^10.3 M_sun and increase at larger masses. We compare our
findings with other analyses and discuss some implications for galaxy formation
and for dark matter estimates.
