Thesis
I have done my thesis under the supervision of Drs Domique Fouchez, Benjamin Racine and Julian Bautista. My thesis subject was The determination of the growth rate of structures using Type Ia Supernovae from the ZTF photometric survey. I defended in September 2023 at Centre de Physique des Particules de Marseille
Abstract
The acceleration of the expansion of the Universe is modeled by the presence of dark energy, represented by a cosmological constant \(\Lambda\), for which there is no entirely satisfactory physical interpretation. The main alternatives to this constant are models of dynamic dark energy or modifications to the laws of general relativity. Measuring the growth rate of \(f \sigma_8\) structures through observations of the velocity field of galaxies is an effective way of detecting possible deviations from the standard model and discriminating between dynamical dark energy and modified gravity. In this thesis, I study the use of distance indicators such as type Ia supernovae to measure \(f \sigma_8\). My work focuses on developing a simulation of the ZTF survey to study the biases and systematics of \(f \sigma_8\) analysis. This analysis relies on the use of a velocity estimator that uses measurements of a distance modulus of an SN Ia and the redshift of the associated host galaxy. The velocities are then used in the maximization of a likelihood function with \(f \sigma_8\) as a free parameter. A simulation of 27 ZTF mocks, each one equivalent to six years of survey, shows that the magnitude limit for spectroscopic classification of SNe Ia leads to a selection bias after a redshift \(z\sim 0.06\). This bias is reflected in \(f \sigma_8\). Limiting the data with a cutoff at \(z\sim 0.06\) yields an unbiased measure of \(f \sigma_8\) with an accuracy of \(19 \%\). This result is already comparable to those obtained with low-redshift galaxies. In addtion, the use of a perfect bias correction to include SNe Ia at higher redshifts does not significantly reduce the error on\(f \sigma_8\).