COSMOLOGY WITH STRONG-LENSING SYSTEMS

Abstract

In this paper, we assemble a catalog of 118 strong gravitational lensing\nsystems from SLACS, BELLS, LSD and SL2S surveys and use them to constrain the\ncosmic equation of state. In particular we consider two cases of dark energy\nphenomenology: $XCDM$ model where dark energy is modeled by a fluid with\nconstant $w$ equation of state parameter and in Chevalier - Polarski - Linder\n(CPL) parametrization where $w$ is allowed to evolve with redshift: $w(z) = w_0\n+ w_1 \\frac{z}{1+z}$. We assume spherically symmetric mass distribution in\nlensing galaxies, but relax the rigid assumption of SIS model in favor to more\ngeneral power-law index $\\gamma$, also allowing it to evolve with redshifts\n$\\gamma(z)$. Our results for the $XCDM$ cosmology show the agreement with\nvalues (concerning both $w$ and $\\gamma$ parameters) obtained by other authors.\nWe go further and constrain the CPL parameters jointly with $\\gamma(z)$. The\nresulting confidence regions for the parameters are much better than those\nobtained with a similar method in the past. They are also showing a trend of\nbeing complementary to the supernova Ia data. Our analysis demonstrates that\nstrong gravitational lensing systems can be used to probe cosmological\nparameters like the cosmic equation of state for dark energy. Moreover, they\nhave a potential to judge whether the cosmic equation of state evolved with\ntime or not.\n