# Mapping the Most Massive Cosmic Telescopes

Using Luminous Red
Galaxies (LRGs) as probes of dark matter, we have selected beams from
SDSS with the highest integrated LRG luminosities. We use
follow-up
galaxy spectroscopy to derive magnification maps for this sample.
Several have total virial masses exceeding 3 x 10

In deep Subaru Suprime-Cam imaging of beam 0850, we discover serendipitously a multiply-imaged V-dropout source at z = 5.03 (photometric). The location of the multiply-imaged arcs is consistent with the predicted critical curves for a source plane of z = 5.03 for our spectroscopically-derived mass model. Incorporating the position of the single multiply-imaged galaxy as a constraint on the critical curve location in 0850 gives a 68% confidence band on the lens plane area to a source redshift of 10 with μ > 10 of [1.8, 4.4] square arcminutes. The multiply-imaged galaxy (magenta circles) and its SED are shown below.

^{15}M_{ʘ}. Group catalogs constructed from the spectroscopy indicate a diversity of mass distributions - nearly half are single clusters that dominate the total mass at all redshifts and half are composed of 2-3 clusters more massive than 3 x 10^{14}M_{ʘ}. Magnification maps for two beams with total masses exceeding 3 x 10^{15}M_{ʘ}(source redshift of 2) are shown below.In deep Subaru Suprime-Cam imaging of beam 0850, we discover serendipitously a multiply-imaged V-dropout source at z = 5.03 (photometric). The location of the multiply-imaged arcs is consistent with the predicted critical curves for a source plane of z = 5.03 for our spectroscopically-derived mass model. Incorporating the position of the single multiply-imaged galaxy as a constraint on the critical curve location in 0850 gives a 68% confidence band on the lens plane area to a source redshift of 10 with μ > 10 of [1.8, 4.4] square arcminutes. The multiply-imaged galaxy (magenta circles) and its SED are shown below.