Archives Séminaires 2011-2012

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Séminaire IPAG de Jean-Paul Kneib (LAM Marseille), jeudi 20 octobre 2011 à 11h00, IRAM seminar room

I will review the use of massive galaxy clusters to study the distant Universe. First I will recall the basics of cluster lensing. I will explain how we can build an accurate mass model, and how we can then use these calibrated awkward telescopes to probe distant galaxies. I will present some recent and new results from HST, Herschel and other related observations.

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Séminaire IPAG de Marco Padovani (CSIC-IEEC, Barcelona), jeudi 3 novembre 2011 à 11h00, IPAG seminar room

Cosmic-rays constitute the main ionising and heating agent in dense, starless, molecular cloud cores. The main goal of this work is the calculation of the ionisation rate in a cloud resulting from the collisions between cosmic-ray particles (protons and electrons) and the matter constituting the cloud, mainly molecular hydrogen. We reexamine the physical quantities necessary to determine the cosmic-ray ionisation rate (especially the cosmic ray spectrum at E < GeV and the ionisation cross (…)

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Séminaire IPAG de Wlodek Kofman (IPAG), jeudi 10 novembre 2011 à 11h00, IPAG seminar room

L’objectif de la mission ROSETTA est d’explorer la comète Churyumov-Gerasimenko. Cette mission a été lancée en mars 2004 et comporte un satellite et un atterrisseur. Après un long voyage (10 ans), le satellite sera placé en orbite autour de la comète et l’atterrisseur se posera sur la surface. L’objectif scientifique de cette mission est l’étude de la matière cométaire, de la surface et de la structure interne de la comète. Nous allons décrire les objectifs de cette mission, sa charge utile (…)

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Séminaire IPAG de Etienne le Coarer (IPAG), jeudi 17 novembre 2010 à 11h00, IPAG seminar room

D’un barbu d’un autre age en 1891, naissait la photographie en couleur interférentielle sans avenir. En 2005 un autre barbu en sandale au même age redonne une jouvence à cette technique d’enregistrement du spectre de la lumière dans un volume ridiculement petit. Ainsi le Stationary Wave Integrated Fourier Transform Spectrometer (SWIFTS) est un spectromètre de poche qui se comparerait à certains monstres que nous connaissons bien ... Vous êtes invités à un point d’étape après 6 ans de (…)

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Séminaire IPAG de Eduardo Ros (University of Valencia), jeudi 24 novembre 2011 à 11h00, IRAM seminar room

The gamma and radio extragalactic radio skies are dominated by blazars, active galactic nuclei with beamed relativistic jets oriented towards the observer. Those objects are being probed by the Fermi Gamma-Ray Space Telescope, and due to their high brightness temperatures, their jets can be also monitored and explored at parsec-scales via Very-Long-Baseline Interferometry. This is complemented by single-dish studies of their radio light curves from millimetre to decimetre wavelenghts, as (…)

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Séminaire IPAG de Nicolas Ponthieu (IAS), jeudi 1er décembre 2011 à 11h00, IPAG seminar room

The measure of polarization in the millimeter and submillimeter wavelength range has become a very active field, especially in the past 10 years or so. It is needed by cosmologists who map the Cosmic Microwave Background and by astrophysicists who study the interstellar medium. The former look for traces of primordial gravitationnal waves generated during inflation in the earliest stages of the Universe, the latter derive constraints on the Galactic magnetic field, on dust grain and (…)

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Séminaire IPAG de Alain Chelli (IPAG), jeudi 8 décembre 2011 à 11h00, IPAG seminar room

Phase closure nulling (PCN) is an interferometric mode consisting in observing around the visibility zero of a star. Doing so, the centro-symmetric stellar light is cancelled, revealing asymmetries like spots or companions. We present the very first results of a PCN observational campain in the K band, on Sirius A and a sample of late-type giants fully resolved by the AMBER instrument on the VLTI. At a spectral resolution of 1500, we measure the variations of the visibility zero location as (…)

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Séminaire IPAG de Anaëlle Maury (ALMA fellow, ESO, Garching), jeudi 15 décembre 2011 à 11h00, IPAG seminar room

The launch of the Herschel submillimeter space observatory and the beginning of ALMA science operations have recently opened new windows for our exploration of the early phases of star formation. In this talk, I will describe the two main projects we’ve been carrying out in the last year to try better understanding the physics at work during the Class 0 phase, which is believed to represent the very first step of protostellar formation.
First I will present a study aiming at improving our (…)

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Séminaire IPAG de Gaëlle Dumas (IRAM), jeudi 5 janvier 2012 à 11h00, IPAG seminar room

The Plateau de Bure Arcsec Whirlpool Survey (PAWS, PI : E. Schinnerer) has imaged the CO(1-0) emission in the central 8 kpc of the nearby spiral galaxy M51. Our final data is a combination of the IRAM 30m single-dish and Plateau de Bure interferometer observations, reaching a linear resolution about 45pc and with sensitivity to giant molecular clouds (GMCs) above 10^5 Msun. Thanks to such high quality data, we are able to study the structure of the molecular gas from galactic scales (e.g. (…)

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Séminaire IPAG de Sean Raymond (Obs. de Bordeaux), jeudi 19 janvier 2012 à 11h00, IPAG seminar room

The eccentric orbits of the known extrasolar giant planets provide evidence that most planet-forming environments undergo violent dynamical instabilities. Here, we numerically simulate the impact of giant planet instabilities on planetary systems as a whole. We find that populations of inner rocky and outer icy bodies are both shaped by the giant planet dynamics and are naturally correlated. The orbital distributions of outer planetesimal disks can be drastically altered by the giant planets (…)