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

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LERMA presentation

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LERMA (Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres) is a research entity operated by CNRS and 3 higher education institutions : Observatoire de Paris (OP), Sorbonne Université (SU), and Université de Cergy-Pontoise (UCP). These 3 institutions host the various research groups of LERMA.

Organisation of the laboratory and research topics
LERMA is organized in 4 Research Poles, complemented by 1 transverse structure dedicated to Technology and Research Support. Doctoral studies are principally conducted within École doctorale Astronomie et Astrophysique d’Île de France (ED 127), but about half of our PhD students belong to other doctoral schools in physics, engineering and environment (ED 129, 391, 389, Ed-PIF et 417).

"Galaxies and Cosmology" (OP)

  • Early Universe
  • Galaxy formation and dynamics
  • Clusters of galaxies
  • Dark matter
  • Active galactic nuclei, star formation and feedback in galaxies

"Dynamics of the Interstellar Medium and Stellar Plasmas" (ENS, OP, UPMC)

  • Observational characterization of the ISM cycle
  • Modeling ISM evolution from diffuse gas to stars and disks
  • Chemical diagnostics of ISM dynamics
  • Turbulent and radiative transport in (circum)stellar plasmas
  • Experimental studies of (circum)stellar plasmas

"Molecules in the Universe" (UCP, OP, UPMC)

  • Gas-surface interactions
  • Gas-phase molecular processes
  • Exotic isotopic spin ratios
  • Molecular parameters for planetary, terrestrial atmospheres and ISM

"Instrumentation Terahertz and Remote Sensing" (OP)

  • THz components and subsystems
  • THz heterodyne instruments
  • Characterization of clear, cloudy, and rainy atmospheres
  • Characterization of Earth, planets, and comets
  • Data processing, storage and diffusion

Personnel (as of January 2017)

  • 46 engineers and technicians (including 10 under contract)
  • 10 astronomers (including 2 emeriti)
  • 32 teaching researchers (including 3 emeriti and 3 under contract)
  • 21 researchers (including 7 emeriti) 7 post-doctoral fellows
  • 41 PhD students

Salient results

  • The earliest phase of star formation, captured through its bipolar ejection activity (Gerin et al. 2015 A&A 577, L2). La toute première étape de la formation d’une étoile, révélée par son éjection bipolaire (Gerin et al. 2015 A&A 577, L2).
  • New method for measuring the diffusion and desorption energy of atoms and (Minissale, M., Congiu, E., & Dulieu, F. 2016, A&A, 585 A146). Nouvelle méthode pour mesurer l’énergie de diffusion et de désorption des atomes et radicaux (Minissale, M., Congiu, E., & Dulieu, F. 2016, A&A, 585 A146).
  • First results on a 1200 GHz Schottky receiver prototype for JUICE-SWI (Maestrini, A., et al 2016). Les premiers résultats sur le prototype de récepteur Schottky à 1200 GHz pour JUICE-SWI (Maestrini, A., et al 2016).

Séminaires à venir

Vendredi 28 juin 2019, 14h00
Salle de l'atelier, Paris
Is accretion-driven turbulence a key process for galaxy growth ?
résumé :
Spitzer and Herschel infrared spectroscopy has revealed a population of nearby galaxies with weak star formation and unusually bright emission lines (e.g. [CII], H2), with very broad linewidths. The line luminosities are greatly in excess of that expected by photoelectric heating of the gas, suggesting that they are powered by the dissipation of turbulent kinetic energy. This discovery of large masses of gas not associated with star formation reveal the potentially important, but largely unexplored, role that turbulence plays in the energetics and formation of multiphase gas on galactic scales. Is this relevant for filamentary gas accretion onto halos of galaxies? I will discuss a toy model in which some of the gravitational potential energy is transferred into gas accretion streams as they penetrate deeper into halos of young galaxies, and part of that energy is dissipated through a turbulent cascade in the warm infalling gas. We have modeled the excitation of the [CII] line as gas is cooling isobarically during its transition from the warm ionized to cold neutral medium. We find that the contribution of [CII] to the total gas cooling rate is increased to 30% and that this [CII] luminosity fraction is largely independent of metallicity. This may explain the recent ALMA detections of [CII] line emission from very high-redshift galaxies, that is not co-spatial with their UV-continuum and have ratios of [CII] to infrared luminosity that are higher than that expected from star formation.
Vendredi 5 juillet 2019, 14h00
Salle de l'atelier, Paris
Self-generated UV in molecular shocks
Vendredi 20 septembre 2019, 14h00
----------, Paris
Challenging a Newtonian prediction through Gaia wide binaries
UNAM, Mexico
résumé :
Under Newtonian dynamics, the relative motion of the components of a binary star should follow a Keplerian scaling with separation. Once orientation effects and a distribution of ellipticities are accounted for, dynamical evolution can be modelled to include the effects of Galactic tides and stellar mass perturbers. This furnishes a prediction for the relative velocity between the components of a binary and their projected separation. After reviewing recent work evidencing the existence of a critical acceleration scale in Elliptical Galaxies and Globular Clusters, I will show new results showing such a phenomenology in Gaia wide binaries using the latest and most accurate astrometry available. The results are consistent with the Newtonian prediction for projected separations below 7000 AU, but inconsistent with it at larger separations, where accelerations are expected to be lower than the critical a0 value of MONDian gravity. This result challenges Newtonian gravity at low accelerations and shows clearly the appearance of gravitational anomalies of the type usually attributed to dark matter at galactic scales, now at much smaller stellar scales.

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