Archives Séminaires 2013-2014

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Séminaire IPAG de Heloise Meheut (CEA/DSM/IRFU), jeudi 5 septembre 2013 à 11h00, IPAG seminar room

Vortices on Earth are known to concentrate solid particle in the eye of the vortex. A similar process is proposed to concentrate solids in protoplanetary disks and participate to planet formation by explaining one of the most challenging step in planet formation theory : the formation of planetesimals of kilometre size. Vortex scenario is especially in vogue since the asymmetries observed in protoplanetary disks by the Atacama Large Millimeter Array (ALMA) are proposed to be observational (...)

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Séminaire IPAG de Pierre Vernaza (LAM), jeudi 12 septembre 2013 à 11h00, IPAG seminar room

Ordinary chondrite meteorites (OCs) are by far the most abundant meteorites (80% of all falls). Their study along with that of other chondrite classes has provided numerous constraints on the formation and early evolution of the solar system, including a) the migration processes that occurred in the protoplanetary disk prior to primary accretion (i.e. planetesimal formation) and their associated timescales, b) the post- (and syn-) accretional heating events, and c) the collisional events (...)

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Séminaire IPAG de Benjamin Schmitt (University of Pennsylvania), jeudi 19 septembre 2013 à 11h00, IPAG seminar room

We discuss considerations for the design and characterization of ACTPol, a new millimeter-wavelength, polarization-sensitive receiver for the Atacama Cosmology Telescope (ACT). ACT is a six-meter telescope located in northern Chile, dedicated to enhancing our understanding of the structure and evolution of the universe through observations of the Cosmic Microwave Background (CMB) with arcminute resolution. We describe the design of the ACTPol focal plane at full deployment, consisting of (...)

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Séminaire IPAG de Stéphane Corbel (CEA), jeudi 26 septembre 2013 à 11h00, IPAG seminar room

Radio astronomy is at the beginning of a major revolution, thanks to the advent of new large radio telescope arrays. The main step currently planned will be the definition of the Square Kilometer Array (SKA, with a collecting area of one km^2) within a few years. Meanwhile, the construction of SKA precursors is progressing rapidly (ASKAP in Australia and MeerKAT in South Africa), while other networks such as LOFAR in Europe are already producing first scientific results. Radio astronomy (...)

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Séminaire IPAG de Ian Crossfield (MPIA/Heidelberg), jeudi 3 octobre 2013 à 11h00, IPAG seminar room

Surveys for new extrasolar planets reveal that smaller planets with shorter periods occur more frequently than more massive planets located farther from their host stars. Mass and radius measurements alone typically cannot constrain these planets’ bulk internal composition, so many unanswered about their formation and evolution remain unanswered. Atmospheric studies offer the best hope for addressing these questions, but only a few of these smaller planets have been studied in sufficient (...)

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Séminaire IPAG de Kumiko Kotera (IAP), jeudi 10 octobre 2013 à 11h00, IPAG seminar room

The origin of ultrahigh energy cosmic rays (UHECRs, particles arriving on the Earth with energy 10^17- 10^21 eV) is still a mystery. Candidate sources range from the birth of pulsars to explosions related to long-duration gamma-ray bursts or to events in active galactic nuclei. Young pulsars have been scarcely discussed as sources of UHECRs in the literature. However, the production of UHECRs in these objects could give a picture that is surprisingly consistent with the latest data measured (...)

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Séminaire IPAG de Suzanne Aalto (Chalmers), jeudi 17 octobre 2013 à 11h00, IPAG seminar room

Molecular gas plays a fundamental role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei and is therefore a primary evolutionary parameter in starburst and AGN activity. Probing the nature and evolution of the molecular interstellar medium requires tracers that penetrates vast columns of dust while enabling unique investigations of chemical and physical conditions in the molecular gas. In this talk I will present methods of studying (...)

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Séminaire IPAG de Olivier Berné (IRAP), jeudi 7 novembre 2013 à 11h00, IRAM seminar room

The mid-infrared (5-15 um) spectrum of most astronomical objects is characterized by broad spectral bands observed in emission. The "PAH model", introduced in the mid 80’s by Leger & Puget and Allamandola et al., postulates that these bands are due to the fluorescence of large carbonaceous molecules. At the same time, while trying to reproduce the physical and chemical conditions present in the envelopes of evolved stars, Harold Kroto and his collaborators synthesized serendipitously a (...)

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Séminaire IPAG de Matthew Kenworthy (Leiden Obs.), jeudi 14 novembre 2013 à 11h00, IPAG seminar room

From exoplanet radial velocity and transit surveys, the diversity in extrasolar planetary systems is being revealed to us at scales out to 5 to 10 AU. In order to understand their formation mechanisms, we also need to study the composition of exoplanets through direct imaging and spectroscopy. I present results for our searches around nearby early type stars including Fomalhaut, and recent observations confirming the protoplanetary nature of HD 100546b, obtained using the APP coronagraph on (...)

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Séminaire IPAG de Nicolas Martin (Strasbourg Obs.), jeudi 21 novembre 2013 à 11h00, IPAG seminar room

The salience of satellite dwarf galaxies for understanding galaxy formation in a cosmological context has been made all the more evident in the past decade with the discovery of numerous faint Local Group galaxies. These faint systems are not only important to understand the faint end of galaxy formation but also their distribution around their host can test the hierarchical formation induced by the favored cosmological paradigm. I will review our successful effort to mine the two most (...)