A Comparison of Cosmological Models Using Strong Gravitational Lensing
  Galaxies
  Strongly gravitationally lensed quasar-galaxy systems allow us to compare
competing cosmologies as long as one can be reasonably sure of the mass
distribution within the intervening lens. In this paper, we assemble a catalog
of 69 such systems, and carry out a one-on-one comparison between the standard
model, LCDM, and the R_h=ct Universe. We find that both models account for the
lens observations quite well, though the precision of these measurements does
not appear to be good enough to favor one model over the other. Part of the
reason is the so-called bulge-halo conspiracy that, on average, results in a
baryonic velocity dispersion within a fraction of the optical effective radius
virtually identical to that expected for the whole luminous-dark matter
distribution. Given the limitations of doing precision cosmological testing
using the current sample, we also carry out Monte Carlo simulations based on
the current lens measurements to estimate how large the source catalog would
have to be in order to rule out either model at a ~99.7% confidence level. We
find that if the real cosmology is LCDM, a sample of ~200 strong gravitational
lenses would be sufficient to rule out R_h=ct at this level of accuracy, while
~300 strong gravitational lenses would be required to rule out LCDM if the real
Universe were instead R_h=ct. The difference in required sample size reflects
the greater number of free parameters available to fit the data with LCDM. We
point out that, should the R_h=ct Universe eventually emerge as the correct
cosmology, its lack of any free parameters for this kind of work will provide a
remarkably powerful probe of the mass structure in lensing galaxies, and a
means of better understanding the origin of the bulge-halo conspiracy.
