We have derived ages , metallicities and enhanced-element ratios [ \alpha /Fe ] for a sample of 83 early-type galaxies essentially in groups , the field or isolated objects .
The stellar population properties derived for each galaxy corresponds to the nuclear r _ { e } /8 aperture extraction .
The median age found for Es is 5.8 \pm 0.6 Gyr and the average metallicity is +0.37 \pm 0.03 dex .
For S0s , the median age is 3.0 \pm 0.6 Gyr and [ Z/H ] = 0.53 \pm 0.04 dex .
We compare the distribution of our galaxies in the H \beta - [ MgFe ] diagram with Fornax galaxies .
Our elliptical galaxies are 3-4 Gyr younger than Es in the Fornax cluster .
We find that the galaxies lie in a plane defined by [ Z/H ] = 0.99 log \sigma _ { 0 } - 0.46 log Age - 1.60 , or in linear terms Z \propto \sigma _ { 0 } \cdot Age ^ { -0.5 } .
More massive ( larger \sigma _ { 0 } ) and older galaxies present , on average , large [ \alpha /Fe ] values , and therefore , must have undergone shorter star-formation timescales .
Comparing group against field/isolated galaxies , it is not clear that environment plays an important role in determining their stellar population history .
In particular , our isolated galaxies show ages differing in more than 8 Gyr .
Finally we explore our large spectral coverage to derive log ( O/H ) metallicity from the H \alpha and [ N ii ] \lambda 6584 Å and compare it with model-dependent [ Z/H ] .
We find that the O/H abundances are similar for all galaxies , and we can interpret it as if most chemical evolution has already finished in these galaxies .