The Masses, Ancestors, and Descendants of Extremely Red Objects: Constraints from Spatial Clustering

Wide field near-infrared (IR) surveys have revealed a population of galaxies with very red optical-IR colors, which have been termed ``Extremely Red Objects'' (EROs). Modeling suggests that such red colors (R-K > 5) could be produced by galaxies at z>~1 with either very old stellar populations or very high dust extinction. Recently it has been discovered that EROs are strongly clustered. Are these objects the high-redshift progenitors of present day giant ellipticals (gEs)? Are they already massive at this epoch? Are they the descendents of the z3 Lyman Break Galaxies (LBG), which have also been identified as possible high redshift progenitors of giant ellipticals? We address these questions within the framework of the Cold Dark Matter paradigm using an analytic model that connects the number density and clustering or bias of an observed population with the halo occupation function (the number of observed galaxies per halo of a given mass). We find that EROs reside in massive dark matter halos, with average mass > 1E13/h100 Msun. The occupation function that we derive for EROs is very similar to the one we derive for z=0, L>L* early type galaxies, whereas the occupation function for LBGs is skewed towards much smaller host halo masses (~ 1E11 to 1E12/h100 Msun. We then use the derived occupation function parameters to explore the possible evolutionary connections between these three populations.