Confronting the Cosmological Principle: How secure are the foundations of the cosmos?

I will present our recent work using quasars and radio galaxies to confront the cosmological principle, the idea that sits at the heart of modern cosmological theories. Whilst the cosmological principle states that the universe is isotropic and homogeneous, our observations of the Cosmic Microwave Background (CMB) reveal a pronounced dipole, interpreted as our kinematic departure from the local Hubble flow.

Tests of gravity with DES Year 3 weak lensing

The new weak lensing measurements from the first three years of observation by the Dark Energy Survey offer a unique opportunity to constrain deviations from General Relativity, our theory of gravity. Weak gravitational lensing is indeed a powerful probe of the growth of structures. As such it offers a window on the laws of gravity on cosmological scales. We thus used DES Year 3 weak lensing data to test the validity of General Relativity (GR) to a new regime, and explore modifications to GR as an alternative to dark energy.

Soutenance de thèse: "L’évolution des galaxies dans les amas et les groupes jusqu’à z~3 "

C’est avec plaisir que je vous invite à suivre ma soutenance de thèse, le jeudi 29 septembre à 11:00, à Condorcet, salle 646A.

Durant cette soutenance, je présenterai les travaux de ma thèse, intitulée "L’évolution des galaxies dans les amas et les groupes jusqu’à z~3 ", sous la direction de Simona Mei.

Bien cordialement,

Transforming gas-rich low-mass disky galaxies into ultra-diffuse galaxies by ram pressure

Faint extended elliptically shaped ultra-diffuse galaxies and slightly brighter and more compact dwarf elliptical and lenticular stellar systems are common in galaxy clusters. Their poorly constrained evolutionary paths can be studied by identifying young ultra-diffuse galaxy and dwarf elliptical analogues populated with bright, massive stars. Using data mining we identified 11 such low-mass (2 × 10^8 M⊙ < M* < 2 × 10^9 M⊙) galaxies with large half-light radii (2.0 kpc < re < 5 kpc) and recently quenched star formation in the Coma and Abell 2147 galaxy clusters.

Results and open questions on two coasting cosmological models

The ΛCDM Model accurately reproduces most cosmological observations, including primordial nucleosynthesis, the cosmic microwave background radiation, and baryonic acoustic oscillations. However, standard baryonic matter constitutes only 5% of the total content of the ΛCDM universe, while the dominant components – cold dark matter (≈25%) and dark energy (≈70%) – are yet unobserved.


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