The fraction of quiescent massive galaxies in the early Universe

Aims. We attempt to compile a complete, mass-selected sample of galaxies with low specific star-formation rates, and compare their properties with theoretical model predictions. Methods. We use the f (24 mu m)/f(K) flux ratio and the SED fitting to the 0.35-8.0 mu m spectral distribution, to select quiescent galaxies from z similar or equal to 0.4 to z similar or equal to 4 in the GOODS-MUSIC sample. Our observational selection can be translated into thresholds in specific star-formation rate. M/M-*, which can be compared with theoretical predictions. Results. In the framework of the well-known global decline in quiescent galaxy fraction with redshift, we find that a non-negligible fraction similar or equal to 15-20% of massive galaxies with low specific star-formation rate exists up to z similar or equal to 4, including a tail of red and dead galaxies with. M/M-* < 10(-11) yr(-1). Theoretical models vary to a large extent in their predictions for the fraction of galaxies with low specific star-formation rates, but are unable to provide a global match to our data.