Introduction

Status of Euclid

• Stéphanie ESCOFFIER-MARTORY (CPPM, Marseille, France)

Bayesian field-level inference of primordial non-Gaussianity using next-generation galaxy surveys

• Guilhem LAVAUX (IAP, CNRS INSU)

BAO results with DESI

• Etienne Burtin (CEA-Saclay)

Growth-rate measurement with type-Ia supernovae using ZTF survey simulations

• Julian Bautista

LSST in the starting blocks

• Cyrille DOUX (LPSC)

5σ tension between Planck cosmic microwave background and eBOSS Lyman-alpha forest and constraints on physics beyond ΛCDM

• Vivian POULIN (LUPM, CNRS & U. de Montpellier, France)

Restitution talk on the String-Cosmo day

• David ANDRIOT (LAPTh, CNRS)

Restitution atelier Analogue Cosmology and Gravitation

• Maxime JACQUET (Laboratoire Kastler Brossel, Sorbonne Université et CNRS)

Optimal Analysis of Galaxy Clustering Data to Test LCDM and Beyond

• Azadeh Moradinezhad

Restitution atelier Céphéides

• Alain Blanchard (IRAP)
• Alain BLANCHARD (IRAP)

A computing and statistical analysis task force ; ZTF as an LSST test case

• Mickael RIGAULT (IP2I (CNRS/IN2P3))

Slitless spectroscopy in Euclid and beyond

• Yannick COPIN (IP2I Lyon - Université Claude Bernard Lyon 1)

Unraveling cosmology with cosmic voids

• Alice Pisani

Current and forecasted constraints on $\Lambda$CDM for the SKAO intensity mapping surveys in cross-correlation with galaxy clustering

• Maria Berti

Prospectives & évolutions : INSU,CNES & PNCG

• Samuel BOISSIER (LAM)

Dans cette présentation non-scientifique, nous discuterons des prospectives en cours à l'INSU et au CNES, et de l'évolution du PNCG au sein de l'INSU du CNRS.

Cosmological parameters derived from the Planck PR4

• Matthieu Tristram (IJClab, CNRS, France)

candl: Cosmic Microwave Background Analysis with a Differentiable Likelihood

• Lennart Balkenhol

In this talk I present candl: a JAX-powered, differentiable, python-based likelihood for Cosmic Microwave Background (CMB) data. Ground-based CMB experiments will allow us to substantially improve on the cosmological constraints from the Planck mission in the immediate future. However, any result hinting at physics beyond the standard model can only be embraced with confidence if the underlying analysis pipeline is demonstrably robust. candl provides a flexible and easy-to-use likelihood framework, adhering to the mantra: with great data comes great responsibility. Thanks to JAX's automatic differentiation algorithm, calculating derivatives, and by extension Fisher matrices, of candl likelihoods is quick and easy. I demonstrate how the differentiation of candl likelihoods facilitates the construction of data robustness tests and aids in survey optimisation. Moreover, I show the use of gradient-based minimisers and samplers with candl likelihoods. candl comes with the latest primary CMB and lensing data from the South Pole Telescope and Atacama Cosmology Telescope collaborations. candl is pip-installable and publicly available on GitHub.

Can the splashback radius be an observable boundary of galaxy clusters?

• Theo Lebeau

The splashback radius was proposed as a physically motivated boundary of clusters as it sets the limit between the infalling and the orbitally dominated regions. However, galaxy clusters are complex objects connected to filaments of the cosmic web from which they accrete matter that disturbs them and modifies their morphology. In this context, estimating the splashback radius and the cluster boundary becomes challenging. We used a constrained hydrodynamical simulation of the Virgo cluster's replica embedded in its large-scale structure to investigate the impact of its local environment on the splashback radius estimate. We identify the splashback radius from 3D radial profiles of dark matter density, baryons density, and pressure in three regions representative of different dynamical states: accretion from spherical collapse, from filaments, and matter outflow. We also identify the splashback radius from 2D-projected radial profiles of observation-like quantities: mass surface density, emission measure, and Compton-y. We show that the splashback radius mainly depends on the dynamics in each region and the physical processes traced by the different probes. Consequently, caution is required when using the splashback radius as a boundary of clusters, particularly in the case of highly disturbed clusters like Virgo.

Digital twins for bias-free inference

• Jenny Sorce (CNRS)

According to the standard cosmological model, about 95% of the Universe is dark. Recent large survey analyses reveal tensions with this model. For instance, the local measurement of the expansion rate and the estimate of the Universe homogeneity differ by more than three standard deviations from those inferred with the cosmic microwave background. The cosmological debate is to work out whether these tensions are a signature of new physics or of systematic biases in the analyses. Part of the studies relies on cosmological simulations to act as the missing ground truth for inference. However, the simulations reproduce only statistically the cosmic web. A new type of simulations, qualified as constrained, is gaining interest. Initial velocity and density fields of such simulations stem themselves from inference based on observational constraints. This talk will present such digital twins, that I named CLONES (Constrained LOcal & Nesting Environment Simulations) and give a few study examples. CLONES appear as a promising tool to increase our capacity to evade biases in future survey analyses in order to disentangle systematics from real tensions.

Cosmological Measurement of the gravitational constant G using the latest Planck and DESI data releases

• Louis Mirouze

During the last two decades, a large amount of cosmological data with increasing precsion have came up. They contain a wealth of information that goes well beyond the basic cosmological parameters. In particular these datasets allow to make a precise inference of the Gravitational constant G at cosmological scales, complementary to local measurements made on Earth or in the solar system. In this talk, we present updated contraints on G using the recent final Planck data analysis (PR4), along with the Baryon Acoustic Oscillation (BAO) data from DESI. Our analysis demonstrates a one percent measurement of G, consistent with the local CODATA value within one standard deviation. Our analysis also takes into acount a modification of the primordial Helium fraction induced by a variation of G. Finally, we show that our result is robust against several assumptions about the cosmological model (spatial curvature or equation of state of dark energy).

Closing up the S_8 tension ?

• Alain BLANCHARD (IRAP)

I will show that several recent determinations of the amplitude of matter fluctuations at low redshift consistently converge towards values consistent with the CMB-normalized ΛCDM value.

Type Ia Supernovae standardisation and its dependence on environment with ZTF

• Madeleine GINOLIN (IP2I)

I will present new results on Type Ia supernovae standardisation, found in the ZTF Cosmo-DR2 sample in its volume limited version. I will focus on the dependence on environment of the stretch and colour standardisation parameters.

2.1% measurement of the Baryon Acoustic Oscillation scale using the Dark Energy Survey final dataset

• Juan Mena-Fernández

The Dark Energy Survey (DES) is a multi-probe experiment designed to constrain the nature of dark energy. One of the main dark energy probes it studies is galaxy clustering, focusing on the measurement of the Baryon Acoustic Oscillations (BAO) scale. In this work, we present new results from measuring the BAO signal using the final DES data set (DES Year-6). For this purpose, we have optimized the sample selection to maximize the BAO information in the $0.6<z<1.2$ redshift range. We have cross-calibrated the redshift distributions with three independent methods: one based on machine learning (DNF), a direct calibration using VIPERS, and clustering redshifts. We also present three analysis pipelines based on the angular correlation function (ACF), the angular power spectrum (APS) and the projected correlation function (PCF), respectively, which we validate with $\sim$2000 ICE-COLA mock catalogs. Finally, we present a consensus result coming from the statistical combination of the three analyses. Our measurement has a precision of 2.1\%, making it the tightest BAO measurement from a photometric survey ever, and the tightest overall for $z>0.75$ at the end of Stage III.

Stauts of the 4MOST Cosmological Redshift Survey

• Antoine Rocher

The 4-meter Multi-Object Spectroscopic Telescope (4MOST) is a fibre-fed spectroscopic instrument installed on the VISTA telescope in Chile. It will simultaneously measure ~2400 spectra of objects on the sky and aims to study a wide range of astrophysical sciences from galactic science cases to cosmology with large scale structures. In this talk, I will present the current status of 4MOST, which is scheduled to begin observations in early 2025, focusing on the 4MOST-Cosmological Redshidt Survey (CRS), which plans to map ~8 million galaxy quasars observed down to redshift z ~ 3.5.

Generative models of astrophysical fields with scattering transforms on the sphere

• Louise Mousset

"The quest of primordial B-modes in the Cosmic Microwave Background polarization requires to improve our comprehension and modeling of the Galactic foregrounds, in order to isolate the cosmological signal. Also, primordial B-modes are only accessible at very large angular scales on the sky, where the planar approximation is not valid and working with spherical maps is needed. In this context, we have adapted statistical tools, called Scattering Transforms, to a spherical geometry. These statistics, previously developed on planar maps, are able to capture the spatial structures of non-Gaussian fields and allow to build generative models. The adaptation to a spherical geometry has required the use of directional convolutions on the sphere computed with Wigner transforms. We validate the method by constructing generative models of homogeneous astrophysical and cosmological fields. From a single target image, we produce new random realizations and we compare usual statistics (power spectrum, pixel probability density function and Minkowski functionals) between the target and the new realizations. The comparison is very satisfying for most of the fields, both statistically and visually when looking at the maps."

B-mode generation of CMB in the Standard Model Extension

• Iman Motie

"According to standard cosmology, near the last scattering surface, the CMB photons scattered via Compton scattering predict that cosmological scalar perturbations at linear order are not able to source B polarization modes. In this work, we investigate the possibility that such CMB polarization modes are generated even in the presence of linear scalar perturbations by considering the Lorentz-violating operators in the Standard Model Extension (SME). Our results provide a useful tool to constrain new physics using CMB data."

Strong Mixing at the Cosmological Collider

• Arthur Poisson (IAP)

"Apart from its manifest interest in the understanding of the first moments of the universe, the framework of cosmic inflation is also the best way we know to probe fundamental physics at very high energies. In particular, the spontaneous production of massive particles due to the expanding background can leave potentially visible imprints in cosmological correlation functions known as the cosmological collider signal. Within the effective field theory of inflation (EFTI), it is possible to treat these exchange processes in a model-independent way, and explicit computations taking advantage of the conformal invariance of late-time observables have been carried out using various techniques such as the cosmological bootstrap. More recently, the full parameter space allowed by the EFTI has been explored allowing for boost-breaking setups leading to more striking phenomenological signatures, and the recently developed cosmological flow approach numerically gives us access to any correlation function. In this talk, I will expose a treatment of a parameter space region that remains analytically unknown: the strong mixing regime where the inflaton field and the massive particle can experience an infinite number of flavor transformations during the process. I will describe ongoing efforts to describe this regime based on extensions of standard single-field effective field theory techniques."

Impact of blending on weak lensing measurements with Rubin/LSST

• Manon Ramel

"Upcoming deep optical surveys, such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), will scan the sky to unprecedented depths, detecting billions of galaxies. This amount of detections will however cause the apparent superposition of galaxies on the images, called blending, thereby impacting the measurements of individual galaxy properties such as redshifts or shapes, as well as the number of detected galaxies. However, galaxy shapes are key quantities used to estimate the masses of large-scale structures, such as galaxy clusters, through weak gravitational lensing. This talk will present a new catalog matching algorithm, called friendly, for the detection and characterization of blends in simulated LSST data for the Dark Energy Science Collaboration (DESC) Data Challenge 2. The purpose of this matching algorithm is to combine several matching procedures, as well as a probabilistic method to quantify blended systems. By removing the resulted 27\% of galaxies impacted by blending from the data, we show that the amplitude of the excess surface mass density $\Delta\Sigma$ weak lensing profile, which could be biased low due to blending, may be partially corrected. This would also result in impacting clusters weak lensing mass estimates and cosmological parameters."

Cosmological parameters constraints from CMB data analysis with the South Pole Telescope

• Aline Vitrier

Observations of the cosmic microwave background (CMB) anisotropies in temperature and polarization are one of the most powerful probes of cosmology. The ESA Planck satellite provided high precision measurements of cosmological parameters, nonetheless a huge quantity of cosmological information is waiting to be uncovered from the E and B modes of polarization and from the temperature at small angular scales. This data will be crucial to address contemporary tensions of cosmology, such as the Hubble tension. Thus, ground based telescopes aim to improve our knowledge of the universe composition and evolution. The South Pole Telescope (SPT) observes the CMB with its 10m primary mirror from the South Pole. Its third generation camera SPT-3G started collecting data in 2018 and the unprecedented resolution of the final maps will allow cosmological parameters constraints to rival Planck’s. A new field of observation called the Wide Field has been recently defined and extends the survey region to cover 25% of the sky. In this talk, I will introduce this new field and how it complements current measurements of the CMB signal, and discuss how to best analyse it.

Cosmological constraints from the Chandra-Planck galaxy cluster sample

• Gaspard Aymerich (IAS, Université Paris-Saclay)

"Galaxy clusters are a powerful cosmological probe: they track the most recent evolution of large scale structure and therefore are fundamental for testing the cosmological model in the recent Universe. To compare the observations of galaxy clusters with theoretical predictions and thus constrain the cosmological parameters of the underlying model, precise knowledge of cluster masses and redshifts is required. Scaling relations between the cluster masses and  observables (like the richness in optical wavelength, $Y_{\text{SZ}}$ in the mm-band or $Y_X$ in X-rays) are usually used to compute the mass of clusters. We provide a new scaling relation using a sample of clusters from the Planck Early Sunyaev-Zeldovich catalogue that was observed in X-rays by Chandra, and compare it to the results of the Planck collaboration obtained from XMM-Newton observations of a subsample of the ESZ. We calibrate a mass bias for a subset of the Planck cosmological cluster sample with a novel method we propose to account for selection effects, using published weak-lensing data from the Canadian Cluster Cosmology Project (CCCP) and Multi Epoch Nearby Cluster Survey (MENeaCS). Applying this new bias parameter to the full Planck cosmological cluster sample, we obtain new constraints on the cosmological parameters."

Dark matter halo properties of intermediate-z star-forming galaxies

• Bianca-Iulia Ciocan

To address the core-cusp problem, which has been one of the major problems of the ΛCDM concordance model, we analyze the dark matter halo properties of a large sample of intermediate-redshift (0.3<z<1.5) star-forming galaxies spanning a wide range of stellar masses (6.5<log(M*/Msun)<11). For this, we employ integral field unit observations from the MUSE Hubble Ultra Deep Field Survey, as well as photometry from HST and JWST. We analyze the morpho-kinematics of our sample with a 3D modeling approach, using the Galpak3D tool (Bouché+15), which allowed us to measure individual rotation curves in the outskirts of galaxies. We performed disk-halo decompositions with a 3D parametric model, which includes a stellar, dark matter, and gas component, as well as corrections for pressure support. The dark matter halos of the sample were parametrized using six different halo models, including the generalized α, β, γ profile (Di Cintio +14), a Navarro-Frenk-White (Navarro, Frenk, White 1997), Dekel (Dekel et al. 2017, Freundlich et al. 2020a), Burkert (Burkert 1995), coreNFW (Read et al. 2016), and Einasto profile (Navarro et al. 2004). Our 3D methodology was validated using mock data cubes from idealized disk simulations. We performed a comparison between the different disk-halo models, finding that the Di Cintio+14 model is better preferred by the data compared to all the other models. We investigate the properties of the dark matter halos of our sample, such as the fractions of dark matter and its evolution with redshift, the stellar mass-halo mass relation, the concentration-halo mass relation, and the halo scale radius-density relation, as well as the link between core/cusp formation and other galaxy properties such as their star formation history.

Updated CMB Constraints on Reionization with the Planck PR4 Release

• Stephane Ilic (IJCLab)

The cosmic microwave background (CMB) provides a crucial window into the early universe's evolution, offering insights into the epoch of reionization. In this talk, we delve into the findings from the latest (and last) Planck data release, PR4, focusing on updated constraints on reionization derived from CMB observations. We explore the implications of these constraints for understanding the timeline, sources, and mechanisms driving the reionization process. By leveraging cutting-edge data and sophisticated analysis techniques, we aim to deepen our understanding of this pivotal phase in cosmic history and its implications for the broader cosmological framework.

The Inflationary Butterfly Effect

• Sébastien RENAUX-PETEL (IAP - CNRS)

"For the first time, we investigate the non-perturbative dynamics of single field inflation with a departure from slow-roll. Using simulations, we find that oscillatory features in the potential can drastically alter the course of inflation, with major phenomenological implications. In certain cases, the entire Universe gets trapped in a forever inflating de Sitter state. In others, only some regions get stuck in a false vacuum, offering an alternative channel for primordial black hole formation. Analogous to the flap of a butterfly, these results show that small-scale phenomena can have profound consequences on the evolution of the entire Universe. This demonstrates the necessity of a non-perturbative approach in the exploration of the small-scale physics of inflation, particularly in the regime relevant for gravitational-wave astronomy."

Updated Constraints on Hubble Tension Solutions

• Ali Rida Khalife

"Since its appearance almost a decade ago, the Hubble Tension received a great deal of proposals to solve it, with none being completely successful. However, new state of the art data improve our assessment of these models and better constrain their parameters. In this talk, which is based on the work in arXiv: 2312.09814, an evaluation of eleven cosmological models is presented. These models consist of five classical extensions of ΛCDM, Early Dark Energy, the Majoron and the varying electron mass models, along with three of the latter’s extensions. This evaluation, previously performed using Planck, ACT and SDSS data (up to DR-12), is now updated with recent SPT-3G, SDSS-DR16 and SH0ES data. Using a set of novel tension metrics, these models are ranked based on which one is able to reduce the tension, and which requires further study before potentially becoming the new concordance model of Cosmology."