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Fabian Hervas Peters (CEA/IRFU/DAp-AIM/Cosmostat)28/10/2024 14:00
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William D'Assignies Doumerg28/10/2024 14:30
The precision of cosmological constraints derived from key observations in imaging surveys hinges on accurately measuring the true redshift distributions of tomographic redshift bins, particularly their mean redshifts.
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Two approaches are commonly used. One involves using photometry with spectroscopic (or deep-photometry) counterparts. This approach is based on matching the fluxes of... -
Florent Leclercq (Institut d'Astrophysique de Paris)28/10/2024 14:50
Interpretability and accuracy are pivotal challenges in the application of machine learning to cosmology. If machines find something humans don't understand, how can we check (and trust) the results? In this presentation, I contend that addressing this concern is not always obligatory, when machine learning is used to build an emulator of an expensive model. I will elucidate this argument...
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Madeleine Ginolin (IP2I/IN2P3/CNRS)28/10/2024 15:10
With already more than 3,000 Type Ia supernovae (SNe Ia) ready for cosmology, ZTF will be in future years the state-of-the-art low-redshift sample needed to anchor Stage IV supernovae surveys, e.g. LSST.
I will first introduce the ZTF survey, as well as the DR2 SN Ia sample. I will then present an overview of DR2 results, which focuses on supernovae diversity and astrophysical biases. I...
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Anton Chudaykin (University of Geneva)28/10/2024 15:40
The Dark Energy Spectroscopic Instrument (DESI) collaboration has recently released measurements of baryon acoustic oscillation (BAO) from the first year of observations.A joint analysis of DESI BAO, CMB, and SN Ia probes indicates a preference for time-evolving dark energy. We evaluate the robustness of this preference by replacing the DESI distance measurements at $z<0.8$ with the SDSS BAO...
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Carlos Hernandez-Monteagudo (IAC)28/10/2024 16:30
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Simon Bouchard (LPNHE)28/10/2024 17:00
The Bright Galaxy Survey (BGS) is the densest galaxy sample of the DESI project, and the closest in redshift range (z<0.2). At such small redshift scales, the constraint on cosmological parameters is dominated by the "cosmic variance", a statistical error due to the small volume of universe considered. Alternative clustering analysis methods, such as Density-Split or Multi-Tracer analysis have...
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Michel-Andrès Breton (Laboratoire d'Astrophysique de Marseille)28/10/2024 17:20
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Arnaud de Mattia29/10/2024 09:30
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Dr Sandrine Pires (CEA Saclay)29/10/2024 10:00
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Prof. Naoki Yoshida (University of Tokyo)29/10/2024 11:00
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Dr Marie-Noëlle Célérier (Observatoire de Paris)29/10/2024 11:30
Despite its global successes, the LambdaCDM standard model of cosmology
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faces currently a number of tensions and anomalies, due to some
mismatch between early and late cosmic time physical representations. Indeed, in the era of precision cosmology, large scale inhomogeneities can no more be neglected. Fortunately, an exact GR solution exists, which is perfectly well suited for this purpose.... -
Anaïs Widmer29/10/2024 11:50
The Euclid spacecraft was launched in July 2023 to the Earth-Sun Lagrange point L2. The mission will produce one of the largest galaxy cluster catalogues with tens of thousands of clusters over the 15 000 square degrees of its extragalactic sky survey. This catalogue will need to be validated with external data, in order to check for newly discovered clusters, to prepare analyses of...
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Rafael Guzman29/10/2024 14:00
The "Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys" (ARRAKIHS) mission will explore the ultra-low surface brightness universe to investigate the nature of Dark Matter. ARRAKIHS was selected in November 2022 as the next F-class mission at ESA for Phases 0/A/B, with an estimated launch date in 2030. The ARRAKIHS science consortium, led by IFCA (Spain) in...
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Clément Stahl (ObAS)29/10/2024 14:30
Modifying the unconstrained small-scale initial conditions of the Universe could be a game changer for our understanding of cosmic structure formation and address challenges in small-scale galaxy formation. In this talk, I will present you my investigations of the effects of significant small-scale primordial non-Gaussianity (PNG). I have found that such PNGs introduce a distinct and...
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Céline Gouin (IAP)29/10/2024 14:50
Matter distribution around clusters is highly anisotropic from their being the nodes of the cosmic web.The number of filaments they are connected to, i.e., their connectivity, should reflect the level of anisotropy in the matter distribution and must be, in principle, related to their physical properties.
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In this presentation, I will first address the influence of the local connectivity of... -
Florian Ruppin (IP2I Lyon)29/10/2024 15:10
Understanding the impact of astrophysical environment on type Ia supernovae (SNe Ia) properties is crucial to minimize systematic uncertainties in cosmological analyses aiming at constraining the properties of Dark Energy using this probe. We investigated the dependence of the SN Ia SALT2.4 light-curve stretch on the distance from their nearest galaxy cluster to study a potential effect of the...
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Corentin Cadiou (IAP)29/10/2024 15:30
The sample size of galaxies used to probe the large-scale distribution of galaxies and thereby cosmology is ever growing thanks to data from Euclid or the upcoming LSST. However, the current generation of numerical codes (GADGET, RAMSES) that are key to generate mock catalogues to compare the observations to are seeing their limit.
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In this talk, I will present two routes, one clever and one... -
Mahmoud Ahmed Emam Osman (LPNHE)29/10/2024 16:30
We present the Lemaitre project, an independent effort to measure the Dark
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Energy equation of state (w,wa) using (1) a new set of type Ia supernovae (SNe
Ia) from the ZTF, SNLS (years 4 and 5), and Subaru/HSC surveys, covering the
redshift range 0.02 < z < 1.3, (2) a completely new cosmology inference
pipeline. The Lemaitre effort aims to address the tension between recent... -
Dylan KUHN29/10/2024 16:50
The LEMAITRE project (Latest Extensive Mapping of Acceleration with Independent Troves of Redshifted Explosions) seeks to deliver an independent measurement of the distance-redshift relation in the late universe through a previously unpublished set of Type Ia supernovae (SNeIa) from ZTF, SNLS years 4-5, and HSC. Within this framework, we are developing and testing a streamlined,...
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Théo Gayoux (LUTH - Observatoire de Paris-Meudon)29/10/2024 17:10
The galaxy cluster count is a particularly effective probe to constrain cosmological parameters and study the limits of the $\Lambda$CDM model. Indeed, the abundance of galaxy clusters is strongly correlated with cosmological parameters such as $\Omega_m$, $\sigma_8$, and the dark energy equation of state. Future surveys such as Euclid will enable us to acquire astrophysical data on a very...
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ALAIN BLANCHARD (IRAP , OMP)29/10/2024 17:30
The tension on the Hubble constant can be reformulated as a tension on the matter density parameter $\omega_M$. This has the advantage that $\omega_M$ is more directly connected to the CMB-derived parameters, unlike the Huble constant. With the recent DESI measurement, the tensoin is raised up to over6 $\sigma$, stronger than the tension on the Hubble constant.
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Nicolas Clerc (IRAP)30/10/2024 09:00
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Anand Raichoor (EPFL)30/10/2024 09:30
Spec-S5 (2035-2045), building on the success of the DESI experiment, will be a new platform dedicated to map hundreds of millions of stars and galaxies in three dimensions, to address the problems of inflation, dark energy, light relativistic species, and dark matter. The instrumental design consists in an upgrade of both the Mayall and the Blanco telescopes, with a twin design: each telescope...
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Christophe Yeche (CEA Irfu/SPP)30/10/2024 10:00
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Enya Van den Abeele30/10/2024 11:00
Since cosmic shear was first observed in 2000, it has become a key cosmological probe and promises to deliver exquisite dark energy constraints. Next-generation surveys like LSST will provide images with an unprecedented galaxy density, marking the dawn of the era of precision cosmology with cosmic shear. However, shear is inferred from coherent distortions of galaxy shapes, and the relation...
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Chloé Barjou-Delayre30/10/2024 11:20
The cosmological principle assumes the isotropy of our Universe. The high coverage of the Zwicky Transient Facility survey (ZTF) makes it possible to carry out an unprecedented study of the veracity of this principle by using observation of type Ia supernovae (SNe Ia).
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This unique low redshift ($z<0.15$) survey with more than 3000 SNe Ia in the second data release (ZTF-DR2-SNe Ia) which... -
13. Reevaluating the cosmological redshift: insights into inhomogeneities and irreversible processesDr Pascal Tremblin (CEA Paris-Saclay)30/10/2024 11:40
Understanding the expansion of the Universe remains a profound challenge in fundamental physics. The complexity of solving General Relativity equations in the presence of intricate, inhomogeneous flows has compelled cosmological models to rely on perturbation theory in a homogeneous FLRW background. This approach accounts for a redshift of light encompassing contributions from both the...
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CONSTANCE GANOT30/10/2024 12:00
Type Ia Supernovae (SNe Ia) are reliable standard candles for measuring cosmic distances due to their nearly constant maximum luminosity. Standardisation methods have been developed to reduce intrinsic scatter and improve distance estimates. Traditional photometric method reaches a 8% precision in distance, but the SNFactory (SNf) [1] survey has suggested that a spectroscopic approach can...
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Marie Aubert (LPC / CNRS / IN2P3)30/10/2024 12:20
The unprecedented statistics of detected Type Ia supernovae (SNe Ia) brought by the Zwicky Transient Facility (ZTF) enable us to probe the impact of the large-scale structure (LSS) on the properties of these objects. With a volume-limited selection of ZTF-Cosmo-DR2 SNe Ia overlapping with the SDSS-DR7 survey footprint, we investigated the distribution of their properties with regard to voids...
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Jenny Sorce
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Corentin Cadiou
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Damiano Rosselli (CPPM)
Type Ia supernovae (SNe Ia) are well-known distance indicators. Through the distance recovered from SNe, it is possible to recover their host galaxy's peculiar velocities (PVs). The PV field measured by SNe Ia enables us to constrain the growth rate of cosmic structure. Using a realistic simulation of SNe light curves, as expected from LSST, we have analyzed the sample bias due to selections...
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Prof. Benjamin L'Huillier (Sejong University)
With the increase in data quality and quantity, the concordance cosmological model is under increasing tension. Therefore, it has become necessary to test the various hypotheses underlying the model: is the metric Friedman-Robertson-Lemaître-Walker? Is the Universe flat? Is dark energy the cosmological constant? Using state-of-the-arts data and analysis methods, I will show litmus tests of...
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