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2026.05.22

Time Delay cosmography and the Hubble tension

Strongly lensed quasars can be used to measure the Hubble constant, provided the time delays between the lensed images can be measured. The method depends on a model for the lensing galaxy but is fully independent of any other method to measure H0. It is therefore crucial to confirm (or not) the Hubble tension. The method comes however with its own systematics that are currently addressed by th...

2026.06.18

Physics-Informed Machine Learning for precise and accurate weak lensing shear estimation

Weak gravitational lensing has served as an important probe for large-scale structure and cosmology for decades. Stage-IV surveys require both sub-percent calibration accuracy and high statistical precision for WL shear estimation, yet traditional estimators struggle with realistic galaxy complexity while machine-learning methods often introduce biases. I will introduce a physics-informed machi...

2026.05.12

A model independent Alcock–Paczynski test using the profiles of voids and clusters

Robust inference with minimal dependence on uncertain models of physical processes is increasingly essential for precision cosmology. We present a geometrical test based on a null statistic constructed from the distribution of galaxies around cosmological voids and clusters of galaxies. The key idea is to form crossed density contrasts whose leading linear redshift-space distortion terms cancel...

2026.05.12

SPT-selected protoclusters and the early emergence of the hot intracluster gas

The South Pole Telescope (SPT) has discovered a large sample of millimetre point sources in the 2500 deg^2 SPT-SZ survey. Follow-up observations with ALMA show that about 90% of these sources are strongly lensed dusty star-forming galaxies (DSFGs), while the remaining ~10% are compact groups of DSFGs at z~3-7, representing protocluster cores caught during their most intense phase of star format...

2026.04.23

Could we detect the hot CGM in X-ray?

Extended, diffuse soft X-ray emission has been widely detected around individual galaxies and is commonly attributed to either galactic feedback processes or gravitational heating, with the latter expected to be efficient primarily in massive systems. However, in most galaxies the observed X-ray radiation efficiency—defined as the fraction of feedback energy emitted in X-rays—is far below uni...

2026.04.24

A 3D view of the Milky Way spiral arms with Gaia DR3

Due to Gaia’s outstanding astrometric capabilities, the field of Galactic cartography is currently undergoing a revolution, reaching a level of detail and precision that has not been seen before. In this talk I will present some of the recent results in this field: imprints of major mergers in the Galaxy, chemical inhomogeneities in the Galactic disk, and disequilibrium features in stellar dis...

2026.04.23

Chemical enrichment from individual stars in ultra-faint galaxies

Modern galaxy formation simulations routinely reach the scales necessary to self-consistently capture the internal structure of molecular clouds while simultaneously accounting for galactic-scale gas flows. Furthermore, individual stars can be treated as resolved objects, even in cosmological environments. I will present such a suite of simulated dwarf galaxies, in which I systematically explor...

2026.04.22

Metallicity as an Astrophysical Diagnostic

Metallicity is one of the most powerful diagnostics of galaxy formation and evolution, encoding the cumulative history of gas accretion, star formation, feedback, and assembly. In this talk, I will begin with two basic mass-continuity equations governing gas and metal evolution in galaxies, showing how their analytic behaviour naturally explains a wide range of observed scaling relations. I wil...

2026.03.31

Dark Energy and Neutrino Mass – the Latest Hints from DESI Using Baryon Acoustic Oscillations

The DESI collaboration (Dark Energy Spectroscopic Instrument) confirmed its groundbreaking results on dynamical dark energy through the largest 3-dimensional Universe map it observed. This talk highlights how DESI’s Baryon Acoustic Oscillation (BAO) measurements from Data Release 2 further challenge the ΛCDM paradigm, the standard cosmology for the past 30 years. The second part of this talk ...

2026.03.25

4MOST-Cosmology Redshift Survey: Overview

In this talk, I will present the 4-metre Multi-Object Spectroscopic telescope as well as the recent news related to the on-going Science Phase Verification which aims to make different tests for all 4MOST science cases. I will in a second time present in more details the Cosmology Redshift Survey, especially the Bright Galaxies and Luminous Red Galaxies samples, as well as the quality checks an...