2004ApJ...611..725B

Using accurate positions from very deep radio observations to guide multiobject Keck spectroscopy, we have determined a substantially complete redshift distribution for very luminous distant submillimeter-selected galaxies (SMGs). A sample of 73 redshifts for SMGs in seven fields contains a surprisingly large number of ``associations'': systems of SMGs with Mpc-scale separations and redshifts within 1200 km/s. This sample provides tentative evidence of strong clustering of SMGs at z≃2-3 with a correlation length of ~(6.9±2.1)h^–1 Mpc, using a simple pair-counting approach that is appropriate to the small, sparse SMG samples. This is somewhat greater than the well-determined correlation lengths for both z≃3 optical-UV color-selected Lyman break galaxies (LBGs) and z≃2 QSOs. This could indicate that SMGs trace the densest large-scale structures in the high-redshift universe and that they may either be evolutionarily distinct from LBGs and QSOs or subject to a more complex astrophysical bias.