LERMA UMR8112

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



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LERMA UMR8112

Observatoire de Paris LERMA - UMR8112
77 avenue Denfert Rochereau - 75014 Paris

5 place Jules Janssen - 92190 MEUDON

4 place Jussieu Tour 32-33 - 3eme ET - 75005 Paris

Université de Cergy-Pontoise

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Credits

This website uses a graphic template that is designed and produced as part of the project for the harmonization of CNRS websites.

Project manager

Marco Cucchi (Pôle-web, DirCom, CNRS)

Web template development (Web team, Communications Department, CNRS)

  • Pascal Verrier: web development
  • Eric Furlan: web design and integration

Development of the plugin "Seminar"

Amaury Adon

Development of the initial versions of the template

Frank de Albuquerque - Jean-Baptiste Pressac (CNRS) - Valérie Pierre (CNRS) - Benoît Chassigneux - Julien Barnier (GRS) - Jean-Christophe Monferran (LAHIC) - Stéphane Pouyllau (CRHST)

CSS drop-down menu

Eric Meyer - http://more.ericmeyeroncss.com/projects/06/

Photo credits for the default banner

© CNRS Photothèque

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5.3.15

Logo SPIPKit made with SPIP (Internet publication system), free software published under GPL licence

Séminaires à venir

Vendredi 21 décembre 2018, 14h00
Salle de l'atelier, Paris
Astrochemistry in star forming regions : new modeling approaches
Emeric BRON
LERMA
résumé :
Star-forming regions present rich infrared and millimeter spectra emitted by the gas exposed to the feedback of young stars. This emission is increasingly used to study the star formation cycle in other galaxies, but results from a complex interplay of physical and chemical processes : chemistry in the gas and on grain surfaces, (de)excitation processes of the atoms and molecules, heating and cooling balance,... Its understanding thus requires detailed astrochemical models that include the couplings between these processes. In this talk, I will present several examples where new modeling approaches of specific processes and their couplings proved crucial to solve persistent observational riddles : from the driving role of UV irradiation in the dynamics of photodissociation regions (PDR) to the efficient reformation of molecular hydrogen in these regions.
 
Mardi 15 janvier 2019, 11h00
Salle de l'atelier, Paris
ATTENTION jour ET heure inhabituels
Thresholds for Globular Cluster Formation and their Dominance of Star Formation in the Early-Universe
Bruce ELMEGREEN
IBM Research Division
résumé :
Young massive clusters (YMCs) are usually accompanied by lower-mass clusters and unbound stars with a total mass equal to several tens times the mass of the YMC. If this was also true when globular clusters (GCs) formed, then their cosmic density implies that most star formation before redshift ~2 made a GC that lasted until today. Star-forming regions had to change after this time for the modern universe to be making very few YMCs. Here we consider the conditions needed for the formation of a ~10^6 Msun cluster. These include a star formation rate inside each independent region that exceeds ~1 Msun/yr to sample the cluster mass function up to such a high mass, and a star formation rate per unit area of Sigma_SFR ~ 1 Msun/kpc^2/yr to get the required high gas surface density from the Kennicutt-Schmidt relation, and therefore the required high pressure from the weight of the gas. High pressures are implied by the virial theorem at cluster densities. The ratio of these two quantities gives the area of a GC-forming region, ~1 kpc^2, and the young stellar mass converted to a cloud mass gives the typical gas surface density of 500-1000 Msun/pc^2. Observations of star-forming clumps in young galaxies are consistent with these numbers, suggesting they formed today's GCs. Observations of the cluster cut-off mass in local galaxies agree with the maximum mass calculated from Sigma_SFR. Metal-poor stellar populations in local dwarf irregular galaxies confirm the dominant role of GC formation in building their young disks.
 
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