I will present briefly the ZTF DR2 sample. I will then present the SNe stretch and colour distributions, as well as the standardisation process used to make SNe cosmology ready, and how those depend on SN host.
The unprecedented statistic provided by the ZTF DR2 allows us to investigate the interplay between SNIa and the Large-scale structure at low redshift. This interplay is twofold. On the one hand, the LSS provides specific density local environments for the SNIa and their host. On the other hand, the increased statistic allows us to investigate directly the peculiar velocities of SNIa at low...
The distribution of galaxies provides an ideal laboratory to test deviations from General Relativity. In particular, constraints on gravity modifications are commonly obtained by measuring the growth of cosmic structures through redshift-space distortions. However, such constraints rely on the validity of the weak equivalence principle, which has never been tested for the dark matter...
We present methodological advances to perform implicit likelihood inference of cosmology from any forward model of galaxy surveys, while efficiently checking for systematics. The approach is based on a two-steps framework, and does not require any inner knowledge of the forward data model. First, we use SELFI (Simulator expansion for likelihood-free inference) to infer the initial matter power...
We present constraints on cosmological parameters using maps from the last Planck data release (PR4). In particular, we detail an upgraded version of the cosmic microwave background likelihood, HiLLiPoP, based on angular power spectra and relying on a physical modelling of the foreground residuals in the spectral domain. This new version of the likelihood retains a larger sky fraction (up to...
I will discuss various methods for determining the amplitude of matter fluctuations in the recent universe. I will demonstrate that the combination of RSD (Redshift Space Distortions) and Pantheon+ data leads to a high amplitude within the ΛCDM (Lambda Cold Dark Matter) model, consistent with the CMB (Cosmic Microwave Background) data. I will present several independent datasets pointing to...
In this presentation, I will give a status report on the Dark Energy Spectroscopic Instrument (DESI) and focus on the Early Data Release that happened in April 2023. I will present the results of a selection of the papers that were published with some emphasis on the HOD characterisation of DESI tracers.
DESI is a Large scale redshift survey of 40 million galaxies and quasars over 14000...
I will present a method to mitigate the effect of fiber collisions on galaxy clustering in DESI first year of data. Fiber collisions happen because the physical size of the fibers prevents us from observing two galaxies with small angular separation at the same time. Thus, for the first year of DESI observation, we are missing some galaxy pairs at small transverse separation. By removing all...
Small-scale correlations measured in the Lyman-α (Lyα) forest encode information about the intergalactic medium and the primordial matter power spectrum. I my talk, I will introduce a simple and fast method for measuring the 3D Lyman-alpha forest power spectrum at small scales. This measurement approach builds upon the well-established Fast Fourier Transform method used for P1D. I will present...
We present the first CMB-lensing galaxy cluster mass measurement using a combination of ground and space-based surveys (SPT-SZ and Planck). We measure the signal at 4.8 sigma, a significant gain with respect to measurements performed on the two individual datasets. In particular, we show that we take advantage of correlations between the scales observed by SPT-SZ and the scales observed by...
Shear estimation began in 1995 with the KSB proposal which essentially consists of using a combination of the second moments of the observed image of the galaxy and the PSF. Numerous other methods have been proposed over the years, and in most cases, the measurements derived from these methods have to be corrected using simulations, and therefore depend on the assumptions of these simulations,...
In this talk, I will present the latest improvements on the use of field level inference for near field cosmology. We notably investigated accuracy requirements for the Hamiltonian integrator inside the BORG framework. We compare the results to an ensemble of well studied local clusters, and test the adequacy of the cluster abundance in a $\Lambda$CDM scenario.
Trying to obtain dark energy from string theory models is a challenge. An important activity has taken place recently: attempts to obtain a positive cosmological constant (de Sitter spacetime) have mostly failed, and the community has turned to quintessence-like scenarios. Those derived from string theory remain so far difficult to accomodate with observations.
Cosmic birefringence (CB) angle refers tothe rotation of the linear polarization plane of Cosmic Microwave Background(CMB) radiations when parity-violating theories areconsidered. Weanalyze the Quantum Boltzmann equation for an ensemble of CMB photonsinteracting with axion and neutrinos (active and sterile) in the presence of ascalar metric perturbation. After calculating the C_l^{EB} to drive...
Abstract
The phenomenon of light deflection due to the presence of massive objects is called gravitational lensing, which leads to the distortion of the observed images of these distant galaxies. These distortions are usually very small and can be detected only by averaging over a huge number of galaxies. This regime is what we call weak lensing. Weak gravitational lensing serves as a...
