Gravitational lensing in the supernova legacy survey

Abstract

The observed brightness of Type Ia supernovae is affected by gravitational lensing caused by the mass distribution along the line of sight introducing an additional dispersion into the Hubble diagram. We look for evidence of lensing in the SuperNova Legacy Survey (SNLS) 3-year data set by measuring the correlation between the residuals from the Hubble diagram and the gravitational magnification based on a modeling of the mass distribution of foreground galaxies. We find evidence of a lensing signal with a 2.3 s significance. The current result is limited by the number of SNe, their redshift distribution, and the other sources of scatter in the Hubble diagram. We show that for the full SuperNova Legacy Survey sample (~400 spectroscopically confirmed Type Ia SNe and ~200 photometrically identified Type Ia SNe), there is an 80% probability of detecting the lensing signal with a 3 s significance.