Cosmology from gravitational lens time delays and Planck data
  Under the assumption of a flat Lambda-CDM cosmology, recent data from the
Planck satellite point toward a Hubble constant that is in tension with that
measured by gravitational lens time delays and by the local distance ladder.
Prosaically, this difference could arise from unknown systematic uncertainties
in some of the measurements. More interestingly -- if systematics were ruled
out -- resolving the tension would require a departure from the flat Lambda-CDM
cosmology, introducing for example a modest amount of spatial curvature, or a
non-trivial dark energy equation of state. To begin to address these issues, we
present here an analysis of the gravitational lens RXJ1131-1231 that is
improved in one particular regard: we examine the issue of systematic error
introduced by an assumed lens model density profile. We use more flexible
gravitational lens models with baryonic and dark matter components, and find
that the exquisite Hubble Space Telescope image with thousands of intensity
pixels in the Einstein ring and the stellar velocity dispersion of the lens
contain sufficient information to constrain these more flexible models. The
total uncertainty on the time-delay distance is 6.6% for a single system. We
proceed to combine our improved time-delay distance measurements with the WMAP9
and Planck posteriors. In an open Lambda-CDM model, the data for RXJ1131-1231
in combination with Planck favor a flat universe with Omega_k = 0.00+0.01/-0.02
(68% CI). In a flat wCDM model, the combination of RXJ1131-1231 and Planck
yields w = -1.52+0.19/-0.20 (68% CI).
