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

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LERMA Detailed Presentation

5 November 2014

LERMA presentation

LERMA (Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres) is a research entity operated by CNRS and 4 higher education institutions: Observatoire de Paris (OP), École (...)

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29 October 2014

Main partners and collaborations

LERMA develope numerous collaborations both national and international
Major agencies and institutions in charge of space missions and major ground-based facilities having collaborations with (...)

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4 October 2014

Management team

Director: Darek LIS directeur.lerma @ obspm.fr
Deputy Directors : Jean-Hugues FILLION jean-hugues.fillion @ upmc.fr Franck LE PETIT franck.lepetit @ obspm.fr
Technical Director : (...)

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4 October 2014

Administrative team

The LERMA administrative team consists of 7 members, who work closely with the CNRS (INSU and Ile de France Ouest & Nord Delegation (DR5)) administrative services, the Observatoire de Paris (...)

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Séminaires à venir

Vendredi 23 mars 2018, 14h00
Salle de l'atelier, Paris
New Statistical Evidence for AGN-Feedback Giving Rise to ‘Mass-Quenching’ in Central Galaxies
ETH, Zurich
résumé :
One of the most striking features of the population of local galaxies is that the distributions of several key galaxy properties are highly bimodal (e.g. color and star formation rate). In general, high mass galaxies in dense environments, with bulge-dominated morphologies and pressure supported kinematics are more frequently passive (non-star forming) than lower mass galaxies in low density environments, with disc-dominated morphologies and rotationally supported kinematics. Understanding which, if any, of these correlations is causally related to the ‘quenching’ of star formation in galaxies remains an active and hotly debated area of investigation in modern astrophysics. Theoretically, a wealth of physical processes have been evoked to account for central galaxy quenching, including halo mass quenching from virial shocks, feedback from active galactic nuclei (AGN; in either the quasar or radio mode), stabilizing torques from central mass concentrations, or even magnetic fields interacting with the hot gas halo. I will present strong new statistical evidence which suggests that the quenched fraction of local central galaxies is primarily related to their central kinematics (Bluck et al. 2016; 2018 in prep.). I will show that this is broadly consistent with quenching from AGN feedback, through a detailed comparison with a semi-analytic model and a cosmological hydrodynamical simulation.

Vendredi 6 avril 2018, 14h00
Salle de l'atelier, Paris
Realistic dust properties for dust growth in dense cores
Charlène Lefèvre
IRAM, Grenoble
résumé :
Grain growth is expected from far infrared observations but the emission process implies a degeneracy between dust properties and temperatures. On the contrary, the scattering phenomenon does not depend on temperature but relies on dust geometry (size and shape). Nowadays, no dust grain model is able to reproduce consistently the multi-wavelength observations of dense cores including both scattering and emission. Recent laboratory works show the impact of dust composition on emissivities. Dust grain models from the literature suffer from a lack of flexibility: either the dust composition is fixed and too constraining for dense cores (with a magnesium over iron ratio too low) or the dust size distribution is set for given density, porosity, and coagulation time, that likely differ from one core to the other.

Based on methods used to derive aggregate properties for protoplanetary disks, I calculate dust properties for dense cores that take into account dust composition, size distribution and shape. I will present a fast method used to derive realistic dust properties for dense cores in a short computation time. In particular, I will illustrate the impact of porosity on scattering efficiency and dust emissivity. I will also review the consequences on dust amount, and show that grain growth requests cold dust in starless cores. Finally, I will discuss the coagulation time needed to build large dust aggregates.
Vendredi 25 mai 2018, 14h00
Bâtiment B (Salle RdC proche cantine), Paris
Closing the gap between simulations and observations
résumé :
In this talk I will give an overview over my latest results to compare
current observations with latest 3D radiation MHD simulations of turbulent
protoplanetary disks. I will focus on the dust thermal emission in
protoplanetary disks, covering the outer regions which emit in the sub/mm.

In the talk I will present comparisons between the expected dust scale
height from simulations and observations
and how we could use this results to learn about the gas disk dynamics.
I will also show the possibility to explain mm polarization by dust grains
which are aligned by the magnetic field.

Finally I will draw conclusion on the results and discuss about the
possibility to observe MRI activity with current telescope facilities.
Vendredi 1 juin 2018, 14h00
Salle de l'atelier, Paris
Structures in protoplanetary disks: what do they tell us about planet formation ?
résumé :

Vendredi 8 juin 2018, 14h00
Salle de l'atelier, Paris
University of Michgan
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