LERMA UMR8112

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



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Molecules in the Universe


Molecules, ubiquitous in our atmosphere and in space, are providing powerful tools for probing the physics and chemistry of many different environments. They provide important clues for major scientific objectives such as climatology and planetology, star and planet formation and the question of the origin of life.


The analysis of molecular radiation under various extreme conditions requires nowadays, a high level of knowledge in molecular science which has to support a wealth of observational data arising from new generation of telescopes, satellites and probes. In addition, molecular processes are at the cornerstone in the evolution of matter in space.

The thematic pole “Molecules in the Universe” aims at pushing forward the current theoretical and experimental limits in molecular science in order :
(1) to obtain fundamental molecular parameters with high degree of accuracy that are essential for probing and modelling complex media and
(2) to understand and predict - at atomic and molecular levels - an increasing number of unknown molecular processes.

This pole brings together research groups leader in quantum physics/chemistry, low temperature physics, chemical physics as well as surface science researchers. It includes complementary theoretical and experimental teams based at Paris (Jussieu Campus), Meudon and Cergy-Pontoise.

The pole aims at playing a major role at the interface between molecular and astrophysics & atmospheric sciences while being fully invested in fundamental molecular and chemical physics science.

This reserach group has long standing experience in multi-disciplinary approaches and is a major actor of “Laboratory Astrophysics” (http://www.labastro.eu/), a new European Networks engaged in fundamental experimental, interpretative and computational research and modelling.
The pole contributes to the establishment and management of widely-used atomic and molecular databases and data centres (http://www.vamdc.eu/).

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Séminaires à venir

Vendredi 22 janvier 2021, 14h00
via Zoom , Paris
Dark matter halo response to baryons
Jonathan FREUNDLICH
Observatoire astronomique de Strasbourg
résumé :
While cold dark matter numerical simulations predict steep, `cuspy' density profiles for dark matter halos, observations favour shallower `cores'. The introduction of baryonic physics alleviates this discrepancy, notably as feedback-driven outflow episodes contribute to expand the dark matter distribution for stellar masses between 10^7 and 10^10 Msun. I will first present a parametrization of dark matter halo density profiles with variable inner slope and concentration that enables to describe the variety of halo responses to baryons and has analytic expressions for the gravitational potential, the velocity dispersion, and lensing properties. This parametrization provides a useful tool to study the evolution of dark matter haloes, to model rotation curves of galaxies and gravitational lenses, and to be implemented in semi-analytical models of galaxy evolution. I will then present two theoretical models describing core formation in dark matter haloes. In the first one, sudden bulk outflows induced by stellar feedback reorganise the halo mass distribution while it relaxes to a new equilibrium. In the second one, small stochastic density fluctuations induce kicks to collisionless particles that progressively deviate them from their orbits. Both models are tested against numerical simulations and provide a simple understanding of the transition from cusps to cores by feedback-driven outflows.
 
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