Massive, red galaxies in a hierarchical universe-II Clustering of Extremely Red Objects

Abstract

We present predictions for the clustering of Extremely Red Objects (EROs) in a \Lambda cold dark matter Universe, using a semi-analytical galaxy formation model in combination with a cosmological N-body simulation. EROs are red, massive galaxies observed at 0.7< z < 3, and their numbers and properties have posed a challenge to hierarchical galaxy formation models. We analyse the halo occupation distribution and two-point correlation function of EROs, exploring how these quantities change with apparent magnitude, colour cut and redshift. Our model predicts a halo occupation distribution that is significantly different from that typically assumed. This is due to the inclusion of AGN feedback, which changes the slope and scatter of the luminosity-host halo mass relation above the mass where AGN feedback first becomes important. We predict that, on average, dark matter haloes with masses above 10^{13}h^{-1}Msun host at least one ERO at 1.5 < z < 2.5. Taking into account sample variance in observational estimates, the predicted angular clustering for EROs with either (R-K)>5 or (i-K)>4.5 is in reasonable agreement with current observations.