Resolving the baryon-fraction profile in lensing galaxies
  We show the radial dependence of stellar baryon fraction curves derived for
21 lensing galaxies from the CfA-Arizona Space Telescope LEns Survey by means
of stellar population synthesis and pixel-based mass reconstruction. The sample
covers a stellar mass range of Ms~2x10^9-3x10^11 Msol (solar masses) which
corresponds to a total mass range of ML~7x10^9-3x10^12 Msol on scales from 0.25
to 5 Re (effective radii). By examining the Ms-to-ML dependence on radial
distance to the center of each galaxy we find pairs of lenses on small to
intermediate mass scales which approach at large radii the same values for
their enclosed total mass but exhibit very different stellar masses and stellar
baryon fractions. This behaviour subsides for the most massive lenses. All
baryon fraction profiles show that the dark matter halo overtakes the stellar
content between 1.5 and 2.5 Re. We find evidence for a stellar baryon fraction
steadily declining over the full mass range. We shed light on the Fundamental
Plane puzzle by showing that the slope of the ML(<R)-to-Ms(<R) relation
approaches the mass-to-light relation of recent Fundamental Plane studies at
large radii. Less massive dark matter halos turn out to be influenced by the
distribution of stellar matter on resolved scales below 10 kpc. The ongoing
study of resolved baryon fraction profiles will make it possible to evaluate
the validity of star formation models as well as adiabatic contraction
prescriptions commonly used in simulations. [abridged]
