Sub-millimetre galaxies reside in dark matter halos with masses greater
  than 3x10^11 solar masses
  The extragalactic background light at far-infrared wavelengths originates
from optically-faint, dusty, star-forming galaxies in the universe with
star-formation rates at the level of a few hundred solar masses per year. Due
to the relatively poor spatial resolution of far-infrared telescopes, the faint
sub-millimetre galaxies are challenging to study individually. Instead, their
average properties can be studied using statistics such as the angular power
spectrum of the background intensity variations. A previous attempt at
measuring this power spectrum resulted in the suggestion that the clustering
amplitude is below the level computed with a simple ansatz based on a halo
model. Here we report a clear detection of the excess clustering over the
linear prediction at arcminute angular scales in the power spectrum of
brightness fluctuations at 250, 350, and 500 microns. From this excess, we find
that sub-millimetre galaxies are located in dark matter halos with a minimum
mass of log[M_min/M_sun ]= 11.5^+0.7_-0.2 at 350 microns. This minimum dark
matter halo mass corresponds to the most efficient mass scale for star
formation in the universe, and is lower than that predicted by semi-analytical
models for galaxy formation.
