A New Approach to Identifying the Most Powerful Gravitational Lensing
  Telescopes
  The best gravitational lenses for detecting distant galaxies are those with
the largest mass concentrations and the most advantageous configurations of
that mass along the line of sight. Our new method for finding such
gravitational telescopes uses optical data to identify projected concentrations
of luminous red galaxies (LRGs). LRGs are biased tracers of the underlying mass
distribution, so lines of sight with the highest total luminosity in LRGs are
likely to contain the largest total mass. We apply this selection technique to
the Sloan Digital Sky Survey and identify the 200 fields with the highest total
LRG luminosities projected within a 3.5' radius over the redshift range 0.1 < z
< 0.7. The redshift and angular distributions of LRGs in these fields trace the
concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one
known galaxy cluster and 56.0% contain multiple known clusters previously
identified in the literature. Thus, our results confirm that these LRGs trace
massive structures and that our selection technique identifies fields with
large total masses. These fields contain 2-3 times higher total LRG
luminosities than most known strong-lensing clusters and will be among the best
gravitational lensing fields for the purpose of detecting the highest redshift
galaxies.
