Epoch of star formation of VIPERS passive galaxies

I would like to present studies over the epoch of star formation for passive galaxies observed by the VIMOS Public Extragalactic Redshift Survey (VIPERS). VIPERS is an ongoing Large Programme to map in detail the large-scale distribution of galaxies at 0.5 < z < 1.2 with a unique volume (24 square deg) and sampling density. The final sample of this survey is going to reach nearly 100,000 galaxies. As the VIPERS sample contains ~15% of the passive galaxies with known spectroscopic redshift and good quality spectra, it is a perfect sample to study the redshift of formation based on the spectroscopic features. We used the 4000 Å break strength Dn(4000) and Balmer absorption line strength HδA and compare them with a theoretical models to estimate the epoch of star formation of passive galaxies.