Tracing dark matter overdensities with dusty star-forming galaxies

It has been suggested that associations of high-redshift dusty star-forming galaxies (DSFGs) may serve as beacons of protoclusters because DSFGs are high-mass galaxies undergoing rapid assembly. We investigate this possibility using the Bolshoi cosmological N-body simulation and a model for populating the simulation with DSFGs. We find that DSFGs are incomplete tracers of protoclusters because of stochastic sampling effects, and at redshift <~ 2.5, because of ‘downsizing’, the highest dark matter overdensities are not well traced by DSFG associations. However, at high redshift, bright submm sources provide effective means for finding some of the most extreme dark matter overdensities in the Universe; I will discuss two such examples discovered with the South Pole Telescope.