Impact of the Catastrophic Photo-z Error on the Dark Energy Equation of State Parameters by the Method of Baryon Acoustic Oscillations and Weak Lensing

The impact of the catastrophic photo-z errors on the constraints of dark energy equation of state(EOS) parameters and the complementarity of baryon acoustic oscillations(BAO) and weak lensing(WL) is studied in this paper.Targeting LSST(Large Synoptic Survey Telescope)-like survey projects,we construct a localized catastrophic photo-z error distribution in the upper-left(UL) and bottom-right(BR) of the z-z_ph plane.For the two parts of the catastrophic distribution,we use Fisher matrix to forecast the impact on dark energy EOS parameter constraints by the methods of BAO,WL and joint BAO and WL(BAO+WL).If the existing catastrophic photo-z errors are not included in the fitting model,systematic biases on EOS parameters could be presented.The constraints from UL and BR do not always have the same sign.BAO suffers the least from catastrophic photo-z errors.For total fraction of catastrophic outliers F_t=0.02,the biggest bias is on w₀ for BAO(UL+BR) which is about 30% statistical error.But for WL or BAO+WL,biases are always several times the statistical errors,which shows that the F_t=0.02 catastrophic photo-z errors can not be ignored.Moreover,the impacts of UL and BR on w₀ for WL are almost the same magnitude but different signs,which reduces the total impact.With the F_t=0.02 catastrophic photo-z errors included in the fitting model,the complementarity of BAO and WL is still very strong even though 45 degree of freedom are added into the photo-z error distribution model.Under this condition,the errors of EOS parameters do not increase much.In particular,the errors of EOS parameter from BAO increase by less than one percent compared to that without catastrophic photo-z errors.The errors of w₀ and w_a from WL increase by approximately 14 percent(UL+BR) and 6 percent(UL+BR),respectively.For BAO+WL,the errors of w₀ and w_a both increase about 5 percent(UL+BR).