# Effect of lensing magnification on type Ia supernova cosmology

## TL;DR

This study assesses gravitational lensing magnification's impact on type Ia supernova cosmology, finding negligible effects for current surveys but emphasizing its importance for future large-scale surveys like LSST.

## Contribution

It introduces two methods to estimate supernova magnification and evaluates their effect on cosmological parameter estimation, highlighting the minimal impact in current data.

## Key findings

- No significant correlation between magnification and Hubble residuals.
- Magnification correction slightly alters cosmological parameters but within uncertainties.
- Magnification effects are negligible for current surveys but relevant for future surveys like LSST.

## Abstract

Effect of gravitational magnification on the measurement of distance modulus of type Ia supernovae is presented. We investigate a correlation between magnification and Hubble residual to explore how the magnification affects the estimation of cosmological parameters. We estimate magnification of type Ia supernovae in two distinct methods: one is based on convergence mass reconstruction under the weak lensing limit and the other is based on the direct measurement from galaxies distribution. Both magnification measurements are measured from Subaru Hyper Suprime-Cam survey catalogue. For both measurements, we find no significant correlation between Hubble residual and magnification. Furthermore, we correct for the apparent supernovae fluxes obtained by Supernova Legacy Survey 3-year sample using direct measurement of the magnification. We find $\Omega_{\rm m0} = 0.287 ^{+0.104} _{-0.085}$ and $w = -1.161 ^{+0.595}_{-0.358}$ for supernovae samples corrected for lensing magnification when we use photometric redshift catalogue of Mizuki, while $\Omega_{\rm m0} = 0.253 ^{+0.113} _{-0.087}$ and $w = -1.078 ^{+0.498} _{-0.297}$ for DEmP photo-z catalogue. Therefore, we conclude that the effect of magnification on the supernova cosmology is negligibly small for the current surveys; however, it has to be considered for the future supernova survey like LSST.