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 23 avril 2021, 14h00
Visioconférence, VIDEO
A stellar graveyard in the core of a globular cluster
résumé :
The ubiquity of supermassive black holes in massive galaxies suggests the existence of intermediate-mass ones (IMBHs) in smaller systems. However, IMBHs are at best rare in dwarf galaxies and not convincingly seen in globular clusters. We embarked on a search for such an IMBH in a very nearby core-collapsed globular cluster, NGC 7397. For this we ran extensive mass-orbit modeling with our Bayesian MAMPOSSt-PM code that fits mass and velocity anisotropy models to the distribution of observed tracers in 4D projected phase space. We used a combination of proper motions from HST and Gaia, supplemented with redshifts from MUSE. We found very strong Bayesian evidence for an excess of unseen mass in the core of the cluster amounting to 1 to 2% of the cluster mass. But surprisingly, we found rather strong evidence that this excess mass is not point-like but has a size of roughly 3% of that of the cluster. Our conclusion is robust to our adopted surface density profile and on our modeling of the velocity anisotropy, as the data suggest isotropic orbits throughout the cluster. It is also robust to our use of one or two classes of Main Sequence stars (given the mass segregation in collisional systems such as clusters), as well as on our filtering for quality data. The expected mass segregation suggests that the excess mass is made of objects heavier than Main Sequence stars: white dwarfs, neutron stars and possibly stellar black holes, all of which lost their orbital energy by dynamical friction to end up in the cluster core. I will discuss the evidence for and against the possibility that most of the unseen mass in the center is in the form of such black holes, as well as the consequences of this intriguing possibility.
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