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



by nicolas.moreau@obspm.fr - published on , updated on


Virtual Atomic and Molecular Data Centre Consortium

The "Virtual Atomic and Molecular Data Centre Consortium" (VAMDC Consortium) is a worldwide consortium which federates Atomic and Molecular databases through an e-science infrastructure and an organisation to support this activity (http://www.vamdc.org/structure/how-to-join-us/).

About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for the modeling in media of many fields of astrophysics. The VAMDC Consortium has connected databases from other fields such as the radiation damage and the plasma communities.

The infrastructure is composed of several key components :

  • The Portal is a central access point to look for data. It provides a graphical user interface where users can build queries that are distributed to all the relevant databases at the same time.
  • The species database is a repository of all the atomic and molecular species available in VAMDC. It is populated by gathering daily the chemical species available from each database composing the infrastructure. The species database provides a fast and convenient way to discover where data are located.
  • Each database in the infrastructure is queryable through a web service. They are registered in the VAMDC registry

As a major actor in the field of atomic and molecular physics, the LERMA laboratory is a central element in both the governance and the technical maintenance and evolution of the infrastructure. A team of a senior astronomer and 3 software engineers is involved on different aspects :

  • Marie-Lise Dubernet Tuckey (Astronomer) : current chair of the board of director, scientific coordination.
  • Yaye Awa Ba (computer engineer) : development of the Spectcol software and the Basecol VAMDC node, web manager of the VAMDC website
  • Nicolas Moreau (computer engineer) : development of the VAMDC portal and species database, evolution of standards (convergence with IVOA standards), interface with node managers, co-chair of the technical board
  • Carlo-Maria Zwolf (computer engineer ) : executive director of VAMDC, development of the VAMDC querystore, co-chair of Group of European Data Experts in the Research Data Alliance (RDA) and co-chair of the Federation Identity Management Interest Group in the RDA

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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