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

About us

22 December 2020

Presentation of LERMA

The LERMA (Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères) is a joint research unit (UMR 8112) between the CNRS and 3 higher education institutions, the Paris Observatory (OP), Sorbonne University (SU) and Cergy Paris University (CYU).

Geographic diversity

LERMA is a laboratory with the particularity of being located on 4 sites in the Paris region :


  • Paris Observatory
  • Observatory of Meudon
  • Sorbonne University - UPMC
  • Cergy Paris University - Neuville site

Complex structure

The LERMA has 4 supervisory bodies : the CNRS - Ile-de-France Meudon delegation (DR5), the Paris Observatory - PSL and the institutions Sorbonne University and Cergy Paris University.

In the laboratory there are 24 researchers (including 5 emeritus and 2 under contract), 7 astronomers (including 1 emeritus), 31 teacher-researchers (including 5 emeritus), 37 engineers and technicians (including 4 under contract), 22 PhD students and 6 post-docs (number of staff on 01/10/2020).

Not all members have the same employer. Indeed there are 7 different employers within the LERMA.

Its main doctoral school is ED 127, Astronomie et Astrophysique d’Île-de-France but its students also belong to 4 other doctoral schools (ED 129, 391, 564 PIF and 417).

An organization in poles

Research at LERMA is organized into 4 thematic research clusters and 1 support cluster.

Research teams conduct programs in the fields of cosmology and galaxies, dynamics of interstellar media and stellar plasmas, molecules in the Universe and instrumentation and remote sensing.

Research teams conduct programs in the fields of cosmology and galaxies, dynamics of interstellar media and stellar plasmas, molecules in the Universe and instrumentation and remote sensing.

  • "Galaxies and Cosmology" (OP)
    - Primordial universe (inflation, cosmic microwave background, reionization)
    - Galaxy formation and evolution (high redshift galaxies, secular evolution and galaxy fusion)
    - Cluster of galaxies
    - Dark matter (cold, warm or modified gravity)
    - Active nuclei, stellar formation and feedback in galaxies (efficiency, history and stellar populations)
    - Black holes and galaxies (AGN, starburst, symbiotic growth and feedback)

To learn more about Pole 1, click here or go to the "RESEARCH" tab.

  • "Dynamics of interstellar media and stellar plasmas" (OP, SU)
    - Observational characterization of the interstellar cycle
    - Formation of stars and planets
    - Modeling of interstellar medium condensation, from diffuse gas to stars and disks
    - Chemical diagnostics of interstellar dynamics
    - Turbulence and radiative transport in (circum-)stellar plasmas

To learn more about pole 2, click here or go to the "RESEARCH" tab.

  • "Molecules in the Universe" (SU, CYU, OP)
    - Gas-surface interactions (spin, photons and ice, reactivity on cold surfaces)
    - Gas phase collisional processes
    - Theory and simulations (collisional excitation and reactivity of interstellar molecules)
    - Abnormalities in nuclear spin and isotope ratios
    - Molecular parameters for terrestrial, planetary and interstellar atmospheres
    - Molecular spectroscopy experiments (molecular spectroscopy and laser instrumentation for the environment, high-resolution VUV spectroscopy of interstellar molecules)

To learn more about pole 3, click here or go to the "RESEARCH" tab.

  • "Instrumentation and remote sensing" (OP)
    - THz components and subsystems
    - Heterodyne THz instruments (for ground-based or on-board observatories (balloons, satellites) such as Herschel/HIFI and JUICE/SWI)
    - Research and development activity (HEB and SIS mixers, Schottky diodes)
    - Characterization of clear, cloudy and rainy atmospheres
    - Characterization of the surfaces of the Earth, planets and comets
    - Data processing, archiving and enhancement

To learn more about the pole 4, click here or go to the "RESEARCH" tab.

Read more

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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