Stellar populations of galaxies in the ALHAMBRA survey up to $z \sim 1$. II. Stellar populations of quiescent galaxies within the stellar mass- and the $UVJ$ colour-colour diagrams

L. A. Díaz-García, A. J. Cenarro, C. López-Sanjuan, I. Ferreras, M. Cerviño, A. Fernández-Soto, I. Márquez, M. Pović, I. San Roman, K. Viironen, M. Moles, D. Cristóbal-Hornillos, E. Alfaro, T. Aparicio-Villegas, N. Benítez, T. Broadhurst, J. Cabrera-Caño, F. J. Castander, J. Cepa, R. M. González Delgado, C. Husillos, L. Infante, J. A. L. Aguerri, J. Masegosa, A. Molino, A. del Olmo, J. Perea, F. Prada, J. M. Quintana, V. J. Martínez

Published 2017-11-28Version 1

We aim at discerning the distribution of stellar population parameters (extinction, age, metallicity, and sSFR) of quiescent galaxies within the rest-frame stellar mass- and $UVJ$ colour-colour diagrams up to $z\sim1$ and down to $I=23$ AB, as well as the development of new diagrams to reduce the contamination from dust-reddened galaxies in samples of quiescent galaxies. By use of the photometric data from ALHAMBRA, we determine stellar population parameters of quiescent galaxies using the SED-fitting code MUFFIT and different SSP models. Through the extinctions retrieved by MUFFIT, we remove dusty star forming galaxies from the sample. The distribution of all the stellar populations parameters is also fitted by a bidimensional and locally weighted regression method (LOESS) across the rest-frame diagrams to reduce the impact of uncertainties and provide the distribution of stellar population parameters. Quiescent galaxies selected via $UVJ$ diagrams are typically contaminated by a ~20% fraction of dusty star forming galaxies. A significant part of the galaxies that reside in the green valley are actually obscured star-forming galaxies (~65%). Therefore, the transition of galaxies from the blue cloud to the red sequence, and hence the related mechanisms for quenching, seems to be much more efficient and faster than previously considered. There are well defined correlations in both the rest-frame stellar mass- and $UVJ$ colour-colour diagrams that allow to constrain the ages, metallicities, extinctions, and sSFR of quiescent galaxies with only their rest-frame colours, redshifts and stellar masses. Dust corrections play an important role in understanding how quiescent galaxies are distributed in these diagrams. To perform a pure non-biased selection of quiescent galaxies from these diagrams is key to include dust corrections of the involved colours and also the galaxy stellar mass.