Abstract
Our goal is to study the interplay between star forming, AGN and passive phases of galaxy evolution. For that we need a wide database of galaxy spectra, binning the sample into stellar mass and redshift bins to deal with mass-dependent evolution and completeness. We extracted our galaxy sample from de SDSS/DR7 between 0.05<z<0.50. The stellar mass and the emission line measurements were taken from the STARLIGHT database and average values of galaxy properties were obtained for each bin. In order to distinguish star forming and AGN hosts, we first considered the BPT diagram as it is generally used. Higher stellar mass migrates to the right wing as redshift decreases and one can erroneously infer that the importance of AGN versus star formation increases with time for these objects. However the BPT diagram cannot distinguish retired galaxies from AGN hosts. For that purpose, the WHAN diagram can be used. Purely star forming galaxies dominates at low stellar mass bins while as the mass increases the AGN becomes more significant. Retired and lineless galaxies dominate the galaxy population at the highest stellar mass bins.
