Cosmic Constraints to the wCDM Model from Strong Gravitational Lensing

We study the cosmic constraint to the wCDM (cold dark matter with a constant equation of state w) model via 118 strong gravitational lensing systems which are compiled from SLACS, BELLS, LSD and SL2S surveys, where the ratio between two angular diameter distances D^\rm obs=D_\rm A(z_\rm l,z_\rm s)/D_\rm A(0,z_\rm s) is taken as a cosmic observable. To obtain this ratio, we adopt two strong lensing models: one is the singular isothermal sphere model (SIS) and the other one is the power-law density profile (PLP) model. Via the Markov chain Monte Carlo method, the posterior distribution of the cosmological model parameters space is obtained. The results show that the cosmological model parameters are not sensitive to the parameterized forms of the power-law index \gamma. Furthermore, the PLP model gives a relatively tighter constraint to the cosmological parameters than that of the SIS model. The predicted value of \it \Omega_\rm m=0.31^+0.44_-0.24 by the SIS model is compatible with that obtained by Planck2015: \it \Omega_\rm m=0.313\pm0.013. However, the value of \it \Omega_\rm m=0.15^+0.13_-0.11 based on the PLP model is smaller and has 1.25\sigma tension with that obtained by Planck2015.