Formation and evolution of stellar population based on the red passive galaxies observed up to z ∼ 1

    We would like to present the studies over the evolution and the star formation history of passive galaxies observed by the VIMOS Public Extragalactic Redshift Survey (VIPERS). We compare the 4000 Å break (D4000n) and the Hδ Lick index (HδA) measured on VIPERS stacked spectra with a grid of synthetic spectra to constrain the star formation epochs of these galaxies. Assuming a single burst formation, we find that high-mass passive galaxies formed their stars at zform~2, while low-mass galaxies formed their main stellar population more recently, at zform~1. The consistency of these results, obtained using two independent estimator of the formation redshift (D4000 and HδA), further strengthens a scenario in which star formation proceeds from higher- to lower-mass systems as time passes, i. e. what has become known as the 'downsizing' picture.

Serdecznie zapraszam,
Paweł Łuczak