Talks

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The Concurrence of Mega-Surveys
Wednesday, 05 August 2026
Time Speaker Title Resources
09:30 to 10:00 Martin Crocce (ICE-CSIC, Spain) Cosmology from Six years of Dark Energy Survey data

I will present legacy cosmology results from the final 6 years of the Dark Energy Survey (DES), primarily combining measurements of weak gravitational lensing and galaxy clustering, but also DES SNIa and Baryon Acoustic Oscillations (BAO). DES, one of the largest Stage III imaging weak lensing missions, has surveyed 5000 square degrees of the southern sky, leading to over 150 million galaxies with measured shapes for weak lensing analysis. I will provide an overview of methodological improvements with respect to previous analysis, how we constrain cosmological models using such late-universe datasets, and their consistency with completely independent early-universe measurements from the Cosmic Microwave Background (CMB). I will present implications for the LCDM model and dynamical dark-energy models.
10:00 to 10:30 Joseph Mohr (LMU, Munich, Germany) The Euclid Mission: Status Report and Prospects for the Joint Analysis of Euclid and Rubin Data

The first large scale Euclid public data release, which will include the ~2000 deg^2 of sky imaged near the ecliptic poles during the first year of the survey together with selected Deep and Auxiliary fields, is scheduled for this coming fall. In this talk I'll review the key operational milestones to date in addition to detailing the data products that will be released for scientific analysis of the full community. These include high resolution deep visible imaging, three band deep NIR imaging and NIR grism spectroscopy from Euclid together with a vast collection of ground based imaging-- primarily from the Dark Energy Survey in the south and the UNIONS survey in the north-- to support SED constraints on astrophysical sources. Within the Euclid Consortium there is already intense activity focused on weak gravitational lensing, galaxy clustering and a broad range of so-called (non-cosmological) legacy science, and the prospects for scientific breakthroughs are strong. With the start of the Rubin survey in the south, there is the opportunity to bring together to two leading Stage IV imaging datasets to enhance the scientific discoveries in both collaborations. I will review the Euclid focused effort and our plans for extracting Rubin photometry around Euclid selected objects. Our expectation is that already in Rubin's second survey year, the Rubin survey data will start to surpass the quality and depth of the DES and UNIONS surveys and also provide additional sky coverage of the Euclid dataset in both the northern and southern sky. The combination of these two survey datasets should set the standard for weak lensing cosmological studies, while enabling dramatic improvements also in a broad range of legacy science.
10:30 to 11:00 Arun Kannawadi (Duke University, Durham, USA) An overview of Rubin Data Preview 2

The NSF-DOE Vera C. Rubin Observatory has released an early Data Preview 2, which consists of coadded images and all the catalogs from the Science Validation surveys. I will provide an overview of the data processing steps and the science that even this early data can achieve, especially for cosmology. I will conclude the talk by pointing out the lessons learned from the commissioning phase and laying out the plans for the Data Release 1, expected in 2028.
11:45 to 12:25 - Short Talks

Elizabeth Krause - Kinematic Lensing with the Roman Space Telescope

Ayan Nanda - The Role of Mergers & Environments Affecting Halo Morphology and Morphology-dependent Clustering

Vikhyat Sharma - N-body simulations for cosmology with LiMRs

Ranjini Mondol - Dark Secrets of Baryons: Illuminating Dark Matter-Baryon Interactions with JWST
12:25 to 13:00 - Rapid Fire Poster talks Group A
14:30 to 15:00 Edward Taylor (Swinburne University of Technology, Melbourne, Australia) 4HS: Mapping Mass and Motion across the Southern Sky

I will give a brief overview of the 4MOST Hemisphere Survey (4HS), with particular emphasis on our cosmology science goals of mapping mass and motion on ~Gpc scales, and highlighting several key aspects of the 4HS experimental design relative to past and current surveys.
15:00 to 15:30 Shivam Pandey (University of Arizona, Tucson, USA) Building Accelerated Forward Models for the Large-Scale Structure of the Universe

Developing fast and efficient methods for simulating our observable Universe is a key challenge in maximizing information extraction from cosmological datasets. The current simulations are too slow to scale to the volume necessary to analyze even decade-old observations. I will discuss different machine-learning-based approaches (e.g., using a multi-modal, transformer-based architecture) to learn the mapping from approximate and cheap dark matter-only simulations to galaxies in high-resolution and expensive simulations, achieving an orders-of-magnitude acceleration and the ability to cheaply scale to a large volume. I will discuss how these approaches enable the first analysis of large-volume observations of approximately a million galaxies using simulation-based inference techniques to place precise constraints on cosmological models as well as their application to CMB sky simulations. Finally, I will discuss the potential of these approaches in the context of ongoing and next-generation large-scale cosmological surveys.
15:30 to 16:00 Pranjal R.S. (JPL, Pasadena, USA) Kinematic Lensing with the Roman Space Telescope
16:45 to 17:15 Supranto Boruah (UPenn, Philadelphia, USA) Enabling field-level inference for weak lensing and galaxy clustering

Traditional cosmological analyses rely on summary statistics, which may lead to lossy compression, discarding valuable information encoded in the full cosmological field. Field-level inference offers a path to optimal cosmological constraints by directly modeling the complete density field, but its success hinges critically on accurate forward models and realistic priors. This talk presents our efforts to unlock field-level inference for weak lensing surveys through advances in both methodology and applications to real observational data. First, I describe KaRMMa, our code for reconstructing Bayesian weak lensing mass maps with lognormal priors that capture non-Gaussian structure formation, which we have successfully applied to Dark Energy Survey Year 3 (DES-Y3) data. Second, I discuss how we enhance KaRMMa's forward model using improved analytical prescriptions for small-scale physics. Third, I demonstrate how generative machine learning models—including GANs and diffusion models—can learn data-driven priors that surpass analytical approximations. I will show that diffusion models applied to DES-Y3 enables smaller-scale reconstructions of cosmic structures from real survey data. Finally, I outline our roadmap toward joint field-level inference combining weak lensing and galaxy clustering, with particular emphasis on modeling galaxy bias at the field level. These advances, validated on current survey data, promise to extract maximal cosmological information from upcoming surveys like Rubin Observatory and Roman Space Telescope.
17:35 to 18:05 Suhail Dhawan (University of Birmingham, Birmingham, UK) Kinematic Lensing with the Roman Space Telescope
Thursday, 06 August 2026
Time Speaker Title Resources
09:30 to 10:00 Subha Majumdar (TIFR, Mumbai, India) Making sense of two billion stars - The GAIA view of the Milky Way Dark Matter Halo

I will present the 'best' rotation curve of the Milky Way till now, and what it tells us about the Milky Way dark matter halo (and if time permits, its impications for DM detection)
10:00 to 10:30 Azadeh Fattahi (Stockholm University, Stockholm, Sweden) Stellar-halo mass relation at the faintest end

Understanding the formation and evolution of lowest mass galaxies (ultra faint dwarfs) in low mass dark matter haloes have profound implications for galaxy formation and dark matter models. Addressing this question is challenging both from the theoretical and observational side. Indeed, there are energetic debates on the halo occupation fraction at the low mass end and halo mass threshold for galaxy formation. In this talk, I discuss current constraints on the stellar-halo mass relation at the faint end and present our latest results from a new suite of cosmological simulations, with an unprecedented resolution of solar mass.
10:30 to 11:00 Sushmita Adhikari (IISER Pune, India) The extent of Gas, Dark Matter and stellar light in halos.

I will talk about galaxy clusters, and their extents. In particular focussing on the evolution of the gas and dark matter component as tracers of the halo potential.
11:45 to 12:15 - Short Talks

Manush Manju - Physically Motivated Dust Emission Models for Far-Infrared forecasts

Suchira Sarkar - Exploring the large scale structure from the southern hemisphere using the 4MOST hemisphere survey of the Nearby Universe (4HS)

Swanith Upadhye - Patchy-kSZ modeling from 21cmFAST lightcones and Prospects of Cross correlations with LAEs
12:15 to 13:00 - Rapid Fire Poster talks Group B
14:30 to 15:00 David Alonso (University of Oxford, Oxford, UK) How can we use the Sunyaev-Zel'dovich effect robustly?

The thermal and kinematic Sunyaev-Zel'dovich effects contain vital information about the abundance and thermodynamics of the diffuse baryonic component, which could be vital to understand key astrophysical uncertainties in cosmological analyses as well as to derive cosmological constraints directly. In this talk I will discuss methods to extract these signals robustly in cross-correlation with galaxy survey data, and obtain complementary constraints on cosmology and astrophysics.
15:00 to 15:30 Gilbert Holder (UIUC, Champaign, USA) CMB probes of LSS: what is next?

There are already a lot of ways that current CMB data is measuring LSS. As measurements improve, what is coming next? I'll talk about a few applications from different ways data can improve. Deep polarization measurements will starts to dig out the screening (and scattering) effects of fluctuations in the electron density induced by LSS. Also, pushing CMB measurements to ultra-low frequencies opens up a new way to probe the dark ages and cosmic dawn.
15:30 to 16:00 Anoma Ganguly (University of Arizona, Tucson, USA) Mapping the baryons with kSZ-cosmic shear cross-correlations
16:45 to 17:15 Sharvari N. Ghosh (IIT Kanpur, India) Modelling the matter power spectrum at early epochs using Lagrangian Perturbation Theory Re-expansions

Current and future cosmological surveys aim to map the large scale structure with unprecedented accuracy. To make precise inferences about model parameters, accurate theoretical predictions are required. N-body simulations are usually employed for this task, however, they are slow but more significantly, they are shot-noise limited. Starting evolution at early epochs is computationally very expensive. Lagrangian Perturbation Theory (LPT) provides an alternative perturbative description for modelling structure and is mostly employed to set initial conditions [4]. However, LPT is known to have a finite time of validity for spherically expanding voids [5].

In this talk we will demonstrate a multi-step LPT re-expansion scheme that has been proposed to overcome this limitation [1,2,3]. This scheme involves re-expanding the LPT series solution iteratively, each step subject to a time-of-validity criterion. We present results that benchmark this method by comparing the predicted matter power spectra to GADGET-4 outputs for the same initial data. We also demonstrate the generality of this method by considering initial velocity perturbations that are not necessarily potential flows.

Talk based on
[1] Das and Nadkarni-Ghosh (in preparation)
[2] Nadkarni-Ghosh and Chernoff, MNRAS, 2011 [arXiv:1005.1217]
[3] Nadkarni-Ghosh and Chernoff, MNRAS 2013 [arXiv:1211.5777]

Other References:
[4] Crocce, Pueblas and Scoccimarro, MNRAS 2006 [arXiv:0606.505]
[5] Sahni and Coles, MNRAS 1996 [arXiv:9510142]
17:15 to 17:45 Aritra Kumar Gon (University of Edinburgh, Edinburgh, UK) Split and conquer : Extracting more information from galaxy redshift surveys and CMB experiments

Peculiar velocities of the large-scale structure are a direct consequence of structure formation. They encode valuable information about the growth of structure. The peculiar velocity field leaves its imprints through several cosmological observables. The most established of these is redshift-space distortions, which probe how peculiar velocities affect the clustering of galaxies in real observations. With the concurrence of mega CMB experiments and galaxy surveys, several additional probes are now accessible. The peculiar motion of galaxies introduces dipolar anisotropies in CMB maps. The line-of-sight component of the velocity field can be probed using the kinetic SZ effect, while the transverse component appears through the moving-lens effect, the large-scale ISW dipole, and the polarised kinetic SZ effect.

In this talk, I will mainly present new statistical tools, specifically density-split statistics, to improve the S/N in two key observables, the pairwise kSZ effect and redshift-space distortions. By splitting the halo/galaxy samples according to their density environments and measuring the streaming velocities separately, we find that the total S/N is several times larger than in conventional global measurements. Density-split statistics have already been shown to outperform the two-point correlation function for extracting cosmological information from galaxy redshift surveys. A key challenge with this approach is that the modelling naturally begins in real space, whereas observations are made in redshift space, and I will present ways to address this issue. These improvements can provide complementary information from existing datasets, leading to tighter constraints on cosmological parameters.
17:45 to 18:05 Sankarshana Srinivasan (CEICO, Praha, Czech Republic) Probing gravity using large scale structure: A model-agnostic approach
Friday, 07 August 2026
Time Speaker Title Resources
09:30 to 10:00 Emiliano Sefusatti (INAF-OATS, Trieste, Italy) Massive neutrinos and mixed cold-warm dark matter models from galaxy clustering

I will review some basic assumptions in the perturbative description of the galaxy power spectrum in models with massive neutrinos, providing some tests of full-shape analysis on numerical simulations. I will show how degeneracies among parameters can easily lead to systematic biases in the recovered neutrino mass and how, rather than priors on nuisance parameters, a detection will require strong priors on cosmological parameters. I will then consider a more general class of models characterised by a fraction of non-cold dark matter and show how currents observations from BOSS and DESI can provide important constraints on the energy density of an ultra-light axion component.
10:00 to 10:30 Arka Banerjee (IISER Pune, India) Lagrangian bias in a Gaussian Random Field

Halo bias is typically treated as a set of coefficients in a perturbative expansion. In this talk, I will show that every point in a Gaussian density field has a well-defined scale-independent Lagrangian bias, thereby defining a bias field. This property can be extended to any linear operator acting on the Lagrangian density field, generating secondary bias fields. Halo bias then arises from geometric selection of Lagrangian patches within this pre-existing field, rather than being generated by collapse. I will discuss how this language provides a natural framework for understanding assembly bias and other secondary biases of halo populations. Finally, I will discuss how a forward model built on the bias field idea can extend the reach in k_max of current modeling approaches.
10:30 to 11:00 Aseem Paranjape (IUCAA, Pune, India) Model-agnostic cosmological inference from the redshift-space BAO feature

The baryon acoustic oscillation (BAO) feature in the 2-point clustering of biased tracers in redshift space is a primary science driver for cosmological inference from current and upcoming galaxy surveys. Traditional BAO analyses typically build on templates derived from assuming a cosmological model such as Lambda-CDM. I will argue that the BAO feature can, instead, also be described in a model-agnostic manner, relying only on the assumption that nonlinear growth approximately smears this feature with a Gaussian kernel sourced by gravitationally driven bulk flows as in the Zel'dovich approximation. I will then describe a programme for systematically incorporating various ingredients in this model-agnostic inference scheme, resulting in an accurate, template-free inference tool for a full-shape analysis in the vicinity of the BAO feature.
11:45 to 12:15 Jingjing Shi (University of Tokyo, Tokyo, Japan) Subaru PFS Cosmology - Survey and Science

The Subaru Prime Focus Spectrograph (PFS) is opening a new window on wide-field spectroscopic cosmology. With its highly multiplexed fiber system and broad optical-to-near-infrared wavelength coverage, PFS will map the three-dimensional distribution of galaxies across a large cosmic volume, enabling precise measurements of large-scale structure, cosmic expansion, and the growth of structure. In this talk, I will give an overview of the PFS cosmology survey, including its survey design, target selection, observing strategy, and key science goals. I will discuss how PFS measurements of galaxy clustering, baryon acoustic oscillations, redshift-space distortions, and related probes will contribute to our understanding of dark energy, gravity, neutrino physics, and the evolution of the Universe. I will also highlight the broader scientific legacy of PFS as a major spectroscopic complement to current and upcoming imaging surveys.
12:15 to 12:45 Yogesh Wadadekar (NCRA, Pune, India) Pencil-beam and large-area surveys for galaxy evolution
12:45 to 13:15 Nishikanta Khandai (NISER, Bhubaneswar, India) Multiwavelength Observations of Low Redshift Gas-Rich Galaxies

98% of galaxies detected blindly in the 21cm line of atomic hydrogen (HI) by the ALFALFA survey have optical counterparts in SDSS. We use the 100% ALFALFA catalog and their optical counterparts in SDSS, GALEX and WISE to accurately determine stellar masses, colors of gas rich galaxies. This allows us to constrain the various abundances of gas rich galaxies, e.g. the HI mass function, the HI velocity width function, the Galaxy Stellar Mass Function and Luminosity function, to name a few. These abundances are marginalised distributions of the underlying multiwavelength
distribution of galaxies which we directly constrain. We also use an optically selected sample from SDSS in the ALFALFA footprint and a joint optical-HI samples. After accounting for the selection function these three samples: The HI-selected sample, the optically sample and the joint optical-HI sample are used to constrain the HI Mass - Stellar Mass relation in an unbiased way. We discuss the application of our results in predicting the clustering ofgas rich galaxies.
14:30 to 15:00 Priyamvada Natarajan (Yale University, New Haven, USA) Stress-testing the standard cold dark matter paradigm

Large astronomical surveys, and measurements of the Hubble constant from the near and far Universe have started to reveal hints of tensions of the data with the standard cold dark matter paradigm. The Hubble tension and hints of time evolution in dark energy are causing us to interrogate LCDM more stringently. Gravitational lensing by clusters offers an alternate astrophysical laboratory to stress-test the model. New results using high resolution lensing data and state of the art cosmological simulations show that  small-scale substructure might offer insights as a key diagnostic. We report new tensions with LCDM that call into question the nature of cold dark matter.
15:00 to 15:30 Hironao Miyatake (Nagoya University, Nagoya, Japan) HSC-Niji

I will introduce a new survey using newly fabricated medium-band filters mounted on the Subaru Hyper Suprime-Cam (HSC), HSC-Niji. HSC-Niji will enable us to measure cosmology with high-redshift (high-z) large-scale structure (LSS) by detecting more than a million Lyman-alpha emitters (LAEs) at 2<z<4. With the high-zLSS, we can perform extensive tests of LambdaCDM and explore the primordial Universe. I will also discuss follow-up programs of HSC-Niji, which will provide further precision measurements of high-z LSS.
15:30 to 16:00 Alexandre Refregier (ETH Zürich, Switzerland) Novel Approaches to Cosmological Constraints from Large Scale Surveys

Cosmology has made remarkable progress in the last decades, leading to the establishment of the standard model for cosmology as well as the recent appearance of tensions. We will describe novel approaches for cosmological analyses in the context of current and upcoming large scale cosmological surveys. These will include integrated cosmological probe combination, simulation based inference, field level analyses, and machine learning based inference. We will also discuss current efforts to generate large simulation suites needed for these approaches, as well as their future prospects.
16:45 to 18:05 - Discussion Session: What’s next? How do we go ahead? What is the best synergy?