it enhances the number of red bright galaxies, so that the color distribution of $M_r<-22$ objects is entirely dominated by red ($u-r>1.5$) galaxies; at $0.5\leq z\leq 2$ it yields rest-frame $U-V$ color distribution in agreement with existing observations. In the range $z\approx 1.5-2.5$, we find that $\approx 31 \%$ of galaxies contribute to the EROs population with $m_K<20$, in good agreement with the observed fraction $35\%$. In particular, at magnitudes $m_K=20$ (Vega system) the model yields an EROs surface density of $6.3\,10^{3}$ deg$^{-2}$ matching existing data. Extending our analysis to $z\approx 4$, the model matches the observed surface density $1.5\,10^3$ deg$^{-2}$ of DRGs at $m_K=20$; such a population is predicted to be dominated by galaxies with old stellar for $z\gtrsim 2.5$.'
author:
- 'N. Menci, A. Fontana, E. Giallongo, A. Grazian, S. Salimbeni'
title: 'THE ABUNDANCE OF DISTANT AND EXTREMELY RED GALAXIES: THE ROLE OF AGN FEEDBACK IN HIERARCHICAL MODELS'
---

INTRODUCTION
============

The color distribution of galaxies constitutes a key observable to constrain models of galaxy formation in a cosmological context. In fact, the most delicate sector of such models is that linking the age of stellar populations (closely related to the color) to the depth of the growing 