Effect of gravitational lensing on supernova cosmology

Aim: As a measurement of distance modulus for type Ia supernovae becomes more stringent, it is important to study various systematics for the unbiased measurement of cosmological parameters. In this paper, the effects of gravitational lensing magnification on the measurement of supernovae distance modulus and estimation of cosmological parameters are presented. Method: We use Hyper Suprime-Cam survey data to estimate the interbening large-scale structure. Two distinct methods are applied; one based on weak lensing mass reconstruction and the other based on the galaxy distribution. Then those estimations are converted to predict the possible magnification of individual supernova. Results: We find a very weak correlation between the Hubble residuals and magnification and that the Omega_m and dark energy parameter w alters best fit values by O(1) level. Conclusion: The effect of magnification can be vanishingly small given the current SNLS supernovae sample; however, it becomes important in the era of LSST and WFIRST where the number of supernovae is dramatically increase.