Archives Séminaires 2017-2018

Séminaire

Séminaire IPAG de Laurent Lamy (LESIA), jeudi 14 septembre 2017 à 11h00, IRAM seminar room

The redetection of ultraviolet Uranus’ aurorae with the Hubble Space Telescope (HST) in 2011, 4 years past equinox and during episodes of active solar wind, opened a new window in the study of the asymmetric Uranian magnetosphere, so far restricted to the single observations of Voyager 2 which flew by the planet in 1986. The atypical geometry of the magnetosphere (60° tilt between the rotation and magnetic axes) make it particularly sensitive to solar wind conditions (strength and (...)

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Séminaire IPAG de Amir Levinson (Tel Aviv University), jeudi 21 septembre 2017 à 11h00, salle Manuel Forestini IPAG

It is shown, based on recent numerical simulations and observations of quasar outflows, that the rate at which gas can be supplied to a supermassive black hole at the center of a young galaxy, is limited to about 20 (sigma/300 km/s)^4 solar mass, where sigma is the velocity dispersion of the host bulge, by action of winds expelled from the innermost regions of the accretion flow. This rate is independent of the BH mass and only weakly dependent on the accretion mode (super or sub (...)

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Séminaire IPAG de Michel Guelin et Michael Bremer (IRAM), jeudi 28 septembre 2017 à 11h00, salle Manuel Forestini IPAG

During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation : their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the (...)

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Séminaire IPAG de Melissa Trainer (NASA Goddard Space Flight Center), jeudi 5 octobre 2017 à 11h00, salle Manuel Forestini IPAG

The Sample Analysis at Mars (SAM) instrument onboard the Mars Science Laboratory Curiosity rover measures the chemical composition of major atmospheric species in the vicinity of the rover through dedicated atmospheric inlets. The SAM Quadrupole Mass Spectrometer (QMS) has monitored the volume mixing ratios of the major atmospheric components in Gale Crater over a period of nearly three Mars years (5 Earth years) from landing. The unprecedented seasonal coverage and precision in mixing (...)

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Séminaire IPAG de Benjamin Charnay (LESIA), jeudi 12 octobre 2017 à 11h00, salle Manuel Forestini IPAG

Clouds and haze play a major role in planetary atmospheres, affecting radiative transfer, thermal structure, atmospheric dynamics and composition, as well as observational spectra. Most exoplanets observed by direct imaging or transit spectroscopy seem to be cloudy or hazy. These clouds and hazes block molecular absorption features, making the inference of the atmospheric composition complicated. During this seminar, I will review recent observations of clouds on brown dwarfs and (...)

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Séminaire IPAG de Vincent Pelgrims (LPSC), jeudi 19 octobre 2017 à 11h00, IRAM seminar room

Large-scale correlations of the position angles of the polarization vectors of the light form quasars were discovered almost twenty years ago. These correlations take place over giga parsec scale distances. Due to their extreme-scale nature these observations have been recognized as potentially competing the isotropy of the well-accepted concordance cosmological model. Later these observations have been confirmed and the correlation signal enhanced by means of additional data. After a (...)

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Séminaire IPAG de Etienne Le Coarer (IPAG), jeudi 9 novembre 2017 à 11h00, salle Manuel Forestini IPAG

How and why the labex FOCUS allows a very promising development in european consortium held by Airbus for monitoring from a satellite greenhouse gases on Earth as well as on the planets of our solar system. This seminar (in french) will describe the history of this program and what perspectives it opens to quickly propose imaging micro spectrometers for new space missions of planetary explorations on orbits, rovers or (...)

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Séminaire IPAG de Eric Agol (University of Washington & IAP), jeudi 16 novembre 2017 à 11h00, salle Manuel Forestini IPAG

The TRAPPIST-1 system took the astronomical community by surprise when it revealed seven transiting planets during a 20-day observation with the Spitzer Space Telescope (Gillon et al. 2017). This system provides an excellent opportunity to measure the masses, radii (hence densities), and atmospheres of Earth-sized and Earth-temperature planets in the Solar neighborhood with existing and upcoming ground and space-based facilities. I will describe our recent progress in studying this system (...)

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Séminaire IPAG de Lisseth Gavilan (LATMOS), jeudi 23 novembre 2017 à 11h00, salle Manuel Forestini IPAG

Planets form in protoplanetary disks following a long process where icy dust grains collide and stick. The evolution of dust is integrated in the evolution of the star and disk, a complex system where radiative, dynamic and chemical processes intertwine. One of the critical drivers of disk evolution may be the vigorous X-ray emission of young stars, which irradiate their circumstellar disks. Chemical disk models have recently applied X-ray photochemical rates to the gas phase, but the (...)

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Séminaire IPAG de John Cannon (Macalester College), jeudi 30 novembre 2017 à 11h00, IRAM seminar room

Low-mass galaxies are the most numerous type of extragalactic system at all epochs of the universe. The population of low-mass galaxies in the local volume allows unique astrophysical and cosmological perspectives that are unavailable in more distant or more massive systems. The ALFALFA blind extragalactic HI survey has cataloged tens of thousands of gas-rich galaxies in the local universe and has populated the faint end of the HI mass function with statistical confidence for the first (...)