  Long-slit spectra have been obtained with the Keck telescope for a sample of
11 early-type galaxies covering a wide range in luminosity and hence mass.
Rotation velocity and velocity dispersions, together with 19 Lick line-strength
gradients have been measured, to, on average, two effective radii. Stellar
population models have been used to derive ages, metallicities and alpha/Fe
abundances along the radius. We find that line-strength gradients are due,
mainly, to variations of the total metallicity with the radius. We also find
both, positive and negative, although small, variations in the [alpha/Fe] ratio
with radius. We do not find a correlation between the metallicity and the
[alpha/Fe] gradients, and the local metallicity is not correlated with the
local velocity dispersion for all the galaxies of our sample, which rules out
scenarios where the delay in the onset of the galactic winds is the only
mechanism producing the metallicity gradients. We found that metallicity
gradients are correlated with the shape of the isophotes and the central mean
age and metallicity of the galaxies, for galaxies younger than ~10 Gyr. We show
that the correlation between the gradients and the central values is not due to
the correlation of the errors and indicates that the same process that shaped
the gradient, also modified the structural parameters of the galaxies and
triggered star formation in their centres. This strongly supports the merger
scenario for the formation of these systems, where the degree of dissipation
during those mergers increases as the mass of the progenitor galaxies
decreases. Finally, we also find a dichotomy in the plane
grad[alpha/Fe]-[alpha/Fe] between galaxies with velocity dispersions below and
above ~200 km/s, which requires confirmation with larger samples.
