Weak gravitational lensing create s coherent distortions in\nthe shapes of background galaxies around massiv e foreground galaxies\nand galaxy clusters\, allowing us to map the distri bution of matter\naround these objects. Standard analyses compress this ri ch\, spatially\nstructured signal into a circular average around each lens . This\ncompression is robust and convenient\, but throws together noise a nd\nsignal in a manner which is less than optimal. In this talk I present\ na method that instead models the full two-dimensional lensing pattern.\nI forward model the 2D signal and use simulation-based inference (SBI)\nto avoid restrictive Gaussian-likelihood assumptions on small to\nintermediat e scales. I will also discuss additional systematic checks\ntailored to tw o-dimensional lensing measurements\, and show where the\nmethod offers the largest gains over standard analyses.\n LOCATION:Salle des séminaires Évry Schatzman END:VEVENT BEGIN:VEVENT SUMMARY:Our Universe in Simulation DTSTART;TZID=Europe/Paris:20260224T110000 DTEND;TZID=Europe/Paris:20260224T120000 DTSTAMP:20260224T105100Z UID:2026-02-2411:00:00+00:09"OurUniverseinSimulation"_gobLHim1n4Ey1206f6El DESCRIPTION:Jia Liu (IPMU)\n\nAbstract:
Ongoing and upcoming cosmological surveys—including the Simons Observatory\, LiteBIRD\, Rubin LSST\, Euclid\, DESI\, PSF\, SPHEREx\, and the Roman Space Telescope—will deliver observations of unprecedented pr ecision. Joint analyses across these surveys will be essential for uncover ing fundamental physics\, including the nature of inflation\, dark energy\ , dark matter\, neutrino mass\, and more. In this talk\, I will discuss th e opportunities\, challenges\, and strategies for simulating our universe across multiple wavelengths to realize these goals.\n LOCATION:Salle des séminaires Évry Schatzman END:VEVENT BEGIN:VEVENT SUMMARY:Euclid Q1 galaxy clustering and its cross-correlations with CMB le nsing DTSTART;TZID=Europe/Paris:20260303T110000 DTEND;TZID=Europe/Paris:20260303T120000 DTSTAMP:20260303T105100Z UID:2026-03-0311:00:00+00:09"EuclidQ1galaxyclusteringanditscross-correlati onswithCMBlensing"_aTdYnBmeeCxOwKyplPUq DESCRIPTION:Margherita Lembo\n\nAbstract:
Combining Cosmic Microwave Ba ckground (CMB) observations with large-scale structure (LSS) surveys provi des a powerful lever arm to probe the growth of structure from recombinati on to the present epoch\, test gravity on cosmological scales\, and constr ain the properties of dark matter and dark energy.\n
In this talk\, I wi ll present the first cosmological analysis of galaxy clustering using the Euclid Q1 data release\, together with its cross-correlation with CMB lens ing convergence maps from Planck and the Atacama Cosmology Telescope. We d etect the cross-correlation signal at high significance and find excellent agreement with predictions from simulations and the Planck 2018 ?CDM cosm ology.\n
I will discuss a comprehensive set of robustness tests against observational systematics\, tomographic measurements across redshift bins\ , and initial constraints on galaxy bias and photometric redshift uncertai nties. These results highlight the strong potential of Euclid–CMB cross- correlations as a robust cosmological probe and as a powerful tool to cont rol systematics in forthcoming Euclid data releases.\n LOCATION:Salle des séminaires Évry Schatzman END:VEVENT BEGIN:VEVENT SUMMARY:Emergence and physical origin of environmental effect patterns in galaxy groups DTSTART;TZID=Europe/Paris:20260310T110000 DTEND;TZID=Europe/Paris:20260310T120000 DTSTAMP:20260310T105100Z UID:2026-03-1011:00:00+00:09"Emergenceandphysicaloriginofenvironmentaleffe ctpatternsingalaxygroups"_JnwnRFuvhsdBFgFzgleP DESCRIPTION:Jinsu Rhee (IAP)\n\nAbstract: The role of environments in gala xy evolution has traditionally been studied at the two extremes: galaxy cl usters and the field. In particular\, red and dead galaxies are preferenti ally found in high-density regions. However\, a substantial fraction of ga laxies reside in intermediate-density environments\, namely galaxy groups\ , highlighting the importance of groups in galaxy evolution. Despite this significance\, the dominant population of satellite galaxies in groups is low-mass and faint\, which has limited detailed investigations in both obs ervations and simulations. To address this\, we employ high-resolution cos mological zoom-in simulations to examine how satellite galaxies evolve in low-virial-mass systems. We find that satellite galaxies in groups exhib it distinct patterns of SF quenching and gas stripping compared to their c ounterparts in clusters. In clusters\, gas stripping is primarily driven b y strong ram pressure from the intracluster medium (ICM). In contrast\, gr oup satellite galaxies experience gas removal mainly through interactions with neighboring galaxies\, gas clumps\, and galactic outflows. In additio n\, group satellites display complex SF quenching behaviors\, with quenchi ng occurring near group centers and rejuvenation in the outskirts. Unlike the relatively simple delay-then-rapid quenching scenario often invoked fo r cluster galaxies\, satellite galaxies in groups follow a more diverse se t of gas-stripping and quenching pathways\, primarily driven by their weak er gravitational potentials and the milder environmental effects. These re sults point to the need for a more nuanced description of galaxy evolution across different host halo mass scales.\n LOCATION:Salle des séminaires Évry Schatzman END:VEVENT BEGIN:VEVENT SUMMARY:The golden era of weak gravitational lensing: from pixel to cosmol ogy\, from dark matter cartography to galaxy cluster detection and beyond DTSTART;TZID=Europe/Paris:20260317T110000 DTEND;TZID=Europe/Paris:20260317T120000 DTSTAMP:20260317T105100Z UID:2026-03-1711:00:00+00:09"Thegoldeneraofweakgravitationallensing:frompi xeltocosmology\,fromdarkmattercartographytogalaxyclusterdetectionandbeyond "_dfinBcSeTGGIWQZ76st5 DESCRIPTION:Gavin Leroy\n\nAbstract:
Gravitational lensing is a phenome non ingrained in the laws of gravity\, providing a direct route to mapping the distribution of matter (dark and visible) across cosmic scales. Upcom ing surveys\, such as Euclid\, Rubin LSST\, and Roman\, will\, for the fir st time\, map weak gravitational lensing over the entire sky from billions of sources. Simultaneously\, instruments such as JWST already observe the sky with unprecedented resolution and galaxy density. This unprecedented volume of data opens a noteworthy window for detecting galaxy clusters uni quely through their weak lensing signal\, motivating the development of ne w methods to analyse data faster and control their systematics more effici ently. \n
This talk will discuss key aspects of weak lensing\, starting at the level of the pixels\, with the control of the systematics (Charge Transfer Inefficiency) to ensure accurate weak lensing measurements\, and ending at the level of the largest structures in the universe\, galaxy clu sters. Through this journey\, we will present state-of-the-art methods ass embled for the first time to produce the highest resolution dark matter ca rtography with JWST. As we move from JWST to Euclid\, we will introduce a new multi-scale galaxy cluster detection algorithm based on the wavelet tr ansform. In particular\, we will demonstrate its performance in the contex t of the galaxy cluster detection challenge within the Euclid Consortium. This framework is paving the way for cluster samples as close as possibl e to being selected by total matter content.\n LOCATION:Salle des séminaires Évry Schatzman END:VEVENT BEGIN:VEVENT SUMMARY:Detection of cosmological dipoles aligned with transverse velociti es DTSTART;TZID=Europe/Paris:20260318T110000 DTEND;TZID=Europe/Paris:20260318T120000 DTSTAMP:20260318T105100Z UID:2026-03-1811:00:00+00:09"Detectionofcosmologicaldipolesalignedwithtran sversevelocities"_KNKv5ozF6YnPDdnrhU0b DESCRIPTION:Yan-Cuan Cai\n\nAbstract:
Non-Gaussianity in cosmology re fers to deviations from Gaussian statistics in cosmological observables an d is commonly probed through the three-point correlator\, the bispectrum. Primordial non-Gaussianity (PNG)\, i.e. the bispectrum of primordial fluct uations\, provides a powerful probe of inflationary physics and a means of discriminating between competing inflationary models.\n
I will present how our analysis of the Planck Release 4 (PR4) data has yielded the most s tringent constraints to date on scalar PNG. I will then discuss how future missions\, such as LiteBIRD\, will further enhance these measurements by accessing the tensor sector.\n
Next\, I will introduce a new formalism f or the Spectral Matching Independent Component Analysis (SMICA) method tha t incorporates higher-order statistical information from foregrounds. This framework enables direct bispectrum estimation from frequency-channel map s\, allowing for the simultaneous recovery of the bispectra of multiple co mponents. By shifting non-Gaussianity estimation from the cleaned-map stag e to the component-separation step\, this approach more effectively propag ates and controls foreground-related uncertainties.\n
Finally\, I will b riefly introduce my current research on novel probes of non-Gaussianity an d on studying correlations across different scales.\n LOCATION:Salle des séminaires Évry Schatzman END:VEVENT END:VCALENDAR