Magnification as a Probe of Dark Matter Halos at high redshift
  We propose a new approach for measuring the mass profile and shape of groups
and clusters of galaxies, which uses lensing magnification of distant
background galaxies. The main advantage of lensing magnification is that,
unlike lensing shear, it relies on accurate photometric redshifts only and not
galaxy shapes, thus enabling the study of the dark matter distribution with
unresolved source galaxies. We present a feasibility study, using a real
population of z > 2.5 Lyman Break Galaxies as source galaxies, and where,
similar to galaxy-galaxy lensing, foreground lenses are stacked in order to
increase the signal-to-noise. We find that there is an interesting new
observational window for gravitational lensing as a probe of dark matter halos
at high redshift, which does not require measurement of galaxy shapes.
