Gravitational Lensing of the supernovae from the Supernova Legacy Survey (SNLS)

TL;DR

This paper investigates gravitational lensing effects on Type Ia supernovae from the SNLS, finding a positive correlation between lensing magnification and Hubble residuals, which supports the detection of lensing signals in supernova data.

Contribution

It presents the first measurement of the correlation between lensing magnification and Hubble residuals using SNLS data, confirming previous findings with a larger dataset.

Findings

Detected a positive correlation ( ho=0.177) at 2.51 sigma significance.

Results are consistent with previous SNLS lensing analyses.

Supports the presence of gravitational lensing effects in supernova observations.

Abstract

The presence of mass inhomogeneities along the line of sight of propagation of light fromdistant objects can induce deflection in the flight path of the photon. This phenomenon is called as gravitational lensing. Lensing can have both distortion (shear) and isotropic magnification effects on the source. We studied the effect of lensing magnification on supernova (SN) Ia in this thesis. Presence of lensing would introduce a source of contamination to the brightness distribution of the source (SN Ia in our case). Thus it also enables one to compute the lensing effect indirectly from the Hubble diagram (i.e. from the residual to the Hubble diagram). In this thesis we computed the correlation between these two effects : the Hubble residual and the computed lensing magnification for the SN by the line of sight foreground dark matter haloes. A detection of positive correlation between these two would signify the positivity of lensing signal detection. The data sample is the spectroscopic SNe Ia sample from the five years full SNLS data and the Hubble residuals are those of the preliminary cosmology analysis performed on SNLS5 data. We obtain a signal of \rho = 0.177 at 2.51 \sigma. This result is consistent with the previous SNLS three years data lensing analysis results.