The number of lenses found in the JVAS survey of flat-spectrum radio sources for gravitational lenses is consistent with statistical models of optical surveys for lensed quasars .
The 90 % confidence limit on \Omega _ { 0 } in flat cosmological models ( \Omega _ { 0 } + \lambda _ { 0 } = 1 ) is approximately 0.15 \mathrel { \raise 1.29 pt \hbox { $ < $ } \mkern - 14.0 mu \lower 2.58 pt \hbox { $ \sim$ } } % \Omega _ { 0 } \mathrel { \raise 1.29 pt \hbox { $ < $ } \mkern - 14.0 mu \lower 2.58 pt \hbox { $% \sim$ } } 2 .
Depending on the RLF model , we predict 2.4 to 3.6 lenses in the JVAS survey and in the first part of the fainter CLASS survey , and 0.3 to 0.6 lenses in the brighter PHFS survey for an \Omega _ { 0 } = 1 model .
The uncertainties are due to the small numbers of lenses ( there are only 4 compact JVAS lenses ) and the uncertainties in the radio luminosity function ( RLF ) caused by the lack of information on the redshift distribution of 10-300 mJy radio sources .
If we force the models to produce the observed number of JVAS lenses , the mean redshift of a 50 mJy source varies from z _ { s } = 0.4 for \Omega _ { 0 } = 0 , to 1.9 for \Omega _ { 0 } = 1 , to almost 4.0 for \Omega _ { 0 } = 2 when \Omega _ { 0 } + \lambda _ { 0 } = 1 .
The source fluxes and redshifts of the lenses in the JVAS and CLASS surveys are consistent with the statistical models .
The numbers of four-image lenses found in the JVAS survey and in surveys for lensed quasars are mutually consistent , but slightly larger than expected for models using the observed axis ratios of E and S0 galaxies .
The best fits to the lens data require a projected axis ratio of b / a = 0.50 with a 90 % confidence range of 0.25 < b / a < 0.65 .