LERMA UMR8112

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



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About LERMA

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

The laboratory is organized in four Research Poles:

  • "Galaxies and Cosmology": studies of the early universe, inflation, cosmic microwave background; epoch of reionization; galaxy clusters; dynamics of galaxies, dark matter; galaxy formation and evolution; black holes, AGN, star formation and feedback in local and high-redshift galaxies.
  • "Dynamics of the Interstellar Medium and Stellar Plasmas": observational characterization of the ISM cycle; star and planet formation; ISM modeling, from diffuse gas to stars and disks, chemical diagnostics of the ISM dynamics; modeling the transport mechanisms in circumstellar plasmas; laboratory plasma experiments.
  • "Molecules in the Universe": studies of gas-phase collisional and reactive processes; VUV spectroscopy and photophysics, exobiology; gas-solid interactions and heterogeneous catalysis, laboratory astrophysics.
  • "Instrumentation and Remote Sensing": development of THz heterodyne instrumentation for large instrumental projects, Herschel/HIFI and JUICE/SWI; research and development activities: HEB and SIS mixers, Schottky diodes for applications in tunable local oscillators; Earth and planetary remote sensing, instrument software development.

These research poles are complemented by a transverse structure, dedicated to:
Technology and Research Support

Séminaires à venir

Vendredi 15 novembre 2019, 14h00
Salle de l'atelier, Paris
Excitation mechanisms in the intracluster filaments around the Brightest Cluster Galaxies
Fiorella POLLES
LERMA
résumé :
In the center of galaxy clusters lie giant elliptical galaxies, the Brightest Cluster galaxies (BCGs). These galaxies are often surrounded by a system of filaments (e.g. Salomé & Combes 2003) that emit in a wide range of wavelengths, illustrating the multi-phase nature of these streams. Many of these filaments do not have strong on-going star formation and the photoionization by stellar emission cannot reproduce their emission (Johnstone et al. 2007): what is preventing these structures to create stars and what heating mech- anisms are involved, are still open questions. I have investigated cosmic rays and X-rays as likely heating sources, combining multi-wavelength line emission (?23 lines: from optical to far-infrared) with Cloudy models (Polles et al in prep.). I have fully constrained the model of the ionized phase combining for the first time optical-to-infrared emission and self-consistent multi-phase models, pushing the analysis to the molecular phase on three off-nuclear regions of NGC 1275, the central giant elliptical galaxy of the Perseus Cluster. We showed that using X-ray emission as the main heating sources, all of the ionized line emission can be reproduced. We found that to reproduce [OI]63?m line, a small filling factor of the photodissociation phase is necessary. We also showed that adding an additional dense phase or an extra pressure component is required to robustly re- produce the H2 line emission.
 
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 ?
Pierre GUILLARD
IAP
 
Vendredi 13 décembre 2019, 14h00
Salle de l'atelier, Paris
Falsifying the concordance of cosmology with the large-scale structures
Benjamin L'HUILLIER
Yonsei University, Seoul
 
Vendredi 24 janvier 2020, 14h00
Salle de l'atelier, Paris
The accretion-ejection connection in planet-forming disks. New perspectives from high angular resolution observations
Benoît TABONE
Leiden
 
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