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Ofer Lahav (University College London)06/11/2023 09:30Invité
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Claudia De Dominicis06/11/2023 10:00
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Dr Mickael Rigault (IP2I)06/11/2023 11:00Invité
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Madeleine Ginolin (IP2I/IN2P3/CNRS)06/11/2023 11:30
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.
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Leander Lacroix (LPNHE)06/11/2023 11:50
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Marie Aubert (LPC / CNRS / IN2P3)06/11/2023 12:10
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...
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Camille Bonvin (University of Geneva)06/11/2023 14:00Invité
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Sveva Castello (University of Geneva)06/11/2023 14:30
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...
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Tristan Hoellinger (Institut d'Astrophysique de Paris)06/11/2023 14:50
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...
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Martin Kaercher06/11/2023 15:10
Modified gravity (MG) as an alternative model to the cosmological constant is very appealing in resolving issues in the $\Lambda$CDM paradigm. To comply with general relativity (GR) in high density regions many MG theories exhibit a screening mechanism suppressing the fifth force to recover GR thereby imprinting an environmental dependency into the theory on a fundamental level.
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Recent... -
Yann RASERA (LUTH/Obs. de Paris/Univ. de Paris)06/11/2023 15:30Invité
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Martin Kunz06/11/2023 16:30Invité
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Matthieu Tristram (IJClab, CNRS, France)06/11/2023 17:00Invité
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...
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Dr Brodie Popovic (CNRS)06/11/2023 17:30
Future constraints of cosmological parameters from Type Ia supernovae (SNe Ia) will depend on the use of photometric samples, those samples without spectroscopic measurements of the SNe Ia. There is a growing number of analyses that show that photometric samples can be utilised for precision cosmological studies with minimal systematic uncertainties. To investigate this claim, we perform the...
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ALAIN BLANCHARD (IRAP , OMP)06/11/2023 17:50
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...
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philippe brax (IPHT Saclay)06/11/2023 18:10
Screening the dilaton
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Etienne Burtin (IRFU/CEA - Université Paris-Saclay)07/11/2023 09:00
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.
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DESI is a Large scale redshift survey of 40 million galaxies and quasars over 14000... -
Mathilde Pinon (CEA/Irfu/DPhP)07/11/2023 09:30
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...
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Pauline Zarrouk (LPNHE)07/11/2023 09:50
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Marie Lynn Abdul Karim (IRFU/DPhP CEA-Saclay)07/11/2023 10:10
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...
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M. Svyatoslav Trusov07/11/2023 11:00
I will present my contribution to the creation of realistic mocks for the DESI Bright Galaxy Survey. I will mainly focus on the BGS lightcones that I am producing using simulations created with the Parallel Particle-Mesh GLAM code (Klypin & Prada 2018). I will explain how I populate the dark matter halos with BGS galaxies and how I implement magnitudes and colour so that the mocks reproduce...
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M. Alexandre Huchet (CEA Saclay)07/11/2023 11:20
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...
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Mlle Enya Van den Abeele (LPNHE)07/11/2023 11:40
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,...
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Dr Guilhem Lavaux (Institut d'Astrophysique de Paris / CNRS)07/11/2023 12:00Contribué
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.
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Thibaut Louis (LAL)07/11/2023 14:00Invité
Between 2017 and 2022, the Atacama Cosmology Telescope observed 40% of the sky at arcminute resolution, approximately four times the angular resolution of the Planck satellite. In my presentation, I will discuss recent results based on this data, focusing particularly on the high signal-to-noise measurement of the Cosmic Microwave Background (CMB) lensing field. Additionally, I will elaborate...
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Dr David Andriot (LAPTh, CNRS)07/11/2023 14:30
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.
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Iman MOTIE (Universit de Toulouse, UPS-OMP, IRAP, CNRS, 14 Avenue Edouard Belin, F-31400 Toulouse, France)07/11/2023 14:50
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...
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Hugo Lévy (ONERA / IAP)07/11/2023 15:10
Scalar fields appear in most of the extensions beyond the standard models and are key ingredients in cosmology phenomenology to unveil the dark sector. Among the wide variety of scalar-tensor models proposed over the past decades, some are already ruled-out by lab experiments or astrophysical observations while others remain viable by means of screening mechanisms that dynamically suppress...
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Mlle Vilasini Tinnaneri Sreekanth (CosmoStat, CEA Paris-Saclay)07/11/2023 15:30
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...
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