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 20 septembre 2019, 14h00
Atelier, 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.

Vendredi 11 octobre 2019, 14h00
Salle de l'atelier, Paris
Galaxy clusters and proto-clusters at z>1.5
Simona MEI
résumé :
We will give a short overview of the field and present recent results on galaxy stellar population and morphology in clusters and proto-clusters detected as overdensities around radio-loud AGN at z>1.5 from the CARLA (Clusters Around Radio-Loud AGN) survey. Galaxy clusters in the local Universe predominantly host a population of massive, passive early-type galaxies, which formed the bulk of their stellar populations at redshifts z~2-3. The progenitors of the present-day clusters are clusters and proto-clusters at z>1.5 that are still in the process of assembling. CARLA is the largest homogeneous sample of spectroscopically confirmed clusters and proto-clusters currently available, with 16 clusters and proto-clusters that cover the redshift range 1.6<z<2.8. At these redshifts, we can observe changes in the cluster and proto-cluster galaxy populations both in morphology and star formation quenching. Our results are based on observations with HST/WFC3 and observations of the cold gas around the AGN and in surrounding galaxies with IRAM/NOEMA, ALMA and Keck KWCI. We will compare our sample to samples observed at the same wavelengths and obtained with other selection criteria.
Vendredi 18 octobre 2019, 14h00
Salle de l'atelier, Paris
Fiorella POLLES
Vendredi 29 novembre 2019, 14h00
Salle de l'atelier, Paris
The size of galaxies in the era of ultra-deep imaging
Nushkia CHAMBA
Instituto de Astrofisica de Canarias
résumé :
While the effective radius is a robust parameter, its use to
characterise galaxy sizes has provided a counter-intuitive definition of
what the actual extent of a galaxy is. Current deep imaging therefore
offers a unique opportunity to critically review the convention that the
size of a galaxy is its effective radius and rethink how one best
measures the extent of galaxies using a physically motivated parameter.
We introduce a new definition of galaxy size based on the gas density
threshold for star formation in galaxies. Remarkably, our new size
definition not only captures what the human visual system identifies as
the edge of a galaxy, but also dramatically decreases the scatter in the
stellar mass - size plane by a factor of three. Our size parameter
unifies galaxies spanning five orders of magnitude in stellar mass on a
single mass-size relationship. To demonstrate the implications of our
results, we show that ultra-diffuse galaxies have the same sizes as
regular dwarfs when a size indicator that describes the global structure
of galaxies is used. This work may be extended for larger samples of
galaxies using upcoming wide, deep imaging surveys.
Vendredi 6 décembre 2019, 14h00
Salle de l'atelier, Paris
Is accretion-driven turbulence a key process for galaxy growth ?
Vendredi 13 décembre 2019, 14h00
Salle de l'atelier, Paris
Falsifying the concordance of cosmology with the large-scale structures
Yonsei University, Seoul
Vendredi 24 janvier 2020, 14h00
Salle de l'atelier, Paris
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