LERMA UMR8112

Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères



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Séminaires à venir

Vendredi 13 décembre 2019, 14h00
Salle de l'atelier, Paris
Falsifying the concordance of cosmology with the large-scale structures
Benjamin L'HUILLIER
Yonsei University, Seoul
résumé :
Despite great predictive power and its successes in the last decades, the concordance LCDM cosmological model suffers from both observational and theoretical issues. On the theoretical side, while a dark energy component is needed to explain the late-time acceleration of the Universe, its nature is unknown, and the value of the cosmological constant has to be fine tuned. On the observational side, tensions between cosmic microwave background and late Universe measurements (H0, sigma8) are getting increasingly hard to alleviate.
Therefore, it is important to further test the model. Falsification is an important concept, and can possibly lead to paradigm changes. In this talk, I will focus on model-independent tests of different aspects of the concordance model such as the curvature, the metric, or gravity, in an attempt to falsify it using state-of-the-art cosmological data: type Ia supernovae, baryon acoustic oscillations, and redshift-space distortion. In particular, I will focus on model-independent methods such as iterative smoothing, Gaussian process regression, or crossing statistics, which are a powerful tool for model falsification. While having less constraining constraints than model-dependent approaches, they have more flexibility, are not biased towards a certain model, and can lead to the detection of unexpected features or reveal the presence of systematics in the data.
 
Vendredi 17 janvier 2020, 14h00
Salle de l'atelier, Paris
The role of feedback- and accretion-driven turbulence in galaxy build-up
Pierre GUILLARD
IAP
résumé :
Cosmological models describe accurately the growth of large scale, dark matter-dominated, structures, but largely fail to reproduce the baryon content and physical properties of galaxies. Why? Essentially because the build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation, for which we still miss a robust theory. The energy released by these processes has to dissipate for gas to cool, condense, and form stars. How gas cools is thus a key to understand galaxy formation and why it such an inefficient process. In this seminar, I will discuss a few examples where turbulence driven by gas accretion, feedback, and galaxy interactions, which is largely ignored in models of galaxy formation, and captured in current simulations only over a limited range of scales, may have a major impact on galaxy and halos properties.

 
Vendredi 24 janvier 2020, 14h00
Salle de l'atelier, Paris
The accretion-ejection connection in planet-forming disks. New perspectives from high angular resolution observations
Benoît TABONE
Leiden
 
Vendredi 7 février 2020, 14h00
Salle de l'atelier, Paris
Redistribution of angular momentum from core to disk scales in Class 0 stars
Mathilde GAUDEL
LERMA
 
Séminaires passés...

Séminaires à venir

Vendredi 13 décembre 2019, 14h00
Salle de l'atelier, Paris
Falsifying the concordance of cosmology with the large-scale structures
Benjamin L'HUILLIER
Yonsei University, Seoul
résumé :
Despite great predictive power and its successes in the last decades, the concordance LCDM cosmological model suffers from both observational and theoretical issues. On the theoretical side, while a dark energy component is needed to explain the late-time acceleration of the Universe, its nature is unknown, and the value of the cosmological constant has to be fine tuned. On the observational side, tensions between cosmic microwave background and late Universe measurements (H0, sigma8) are getting increasingly hard to alleviate.
Therefore, it is important to further test the model. Falsification is an important concept, and can possibly lead to paradigm changes. In this talk, I will focus on model-independent tests of different aspects of the concordance model such as the curvature, the metric, or gravity, in an attempt to falsify it using state-of-the-art cosmological data: type Ia supernovae, baryon acoustic oscillations, and redshift-space distortion. In particular, I will focus on model-independent methods such as iterative smoothing, Gaussian process regression, or crossing statistics, which are a powerful tool for model falsification. While having less constraining constraints than model-dependent approaches, they have more flexibility, are not biased towards a certain model, and can lead to the detection of unexpected features or reveal the presence of systematics in the data.
 
Vendredi 17 janvier 2020, 14h00
Salle de l'atelier, Paris
The role of feedback- and accretion-driven turbulence in galaxy build-up
Pierre GUILLARD
IAP
résumé :
Cosmological models describe accurately the growth of large scale, dark matter-dominated, structures, but largely fail to reproduce the baryon content and physical properties of galaxies. Why? Essentially because the build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation, for which we still miss a robust theory. The energy released by these processes has to dissipate for gas to cool, condense, and form stars. How gas cools is thus a key to understand galaxy formation and why it such an inefficient process. In this seminar, I will discuss a few examples where turbulence driven by gas accretion, feedback, and galaxy interactions, which is largely ignored in models of galaxy formation, and captured in current simulations only over a limited range of scales, may have a major impact on galaxy and halos properties.

 
Vendredi 24 janvier 2020, 14h00
Salle de l'atelier, Paris
The accretion-ejection connection in planet-forming disks. New perspectives from high angular resolution observations
Benoît TABONE
Leiden
 
Vendredi 7 février 2020, 14h00
Salle de l'atelier, Paris
Redistribution of angular momentum from core to disk scales in Class 0 stars
Mathilde GAUDEL
LERMA
 
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