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

Accueil > en > About us > About us

Presentation of LERMA

par Elise blanchard - publié le

General presentation

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.

Séminaires à venir

Vendredi 22 janvier 2021, 14h00
via Zoom , Paris
Dark matter halo response to baryons
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.
Tous les séminaires...