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mai 2013
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Séminaire P. Vernazza : "Multiple and Fast : The Accretion of Ordinary Chondrite Parent Bodies"

Vendredi 3 mai 2013 11:00-12:00

Planetesimal formation in the early Solar System is a very complex process through which initially submicron-sized dust grains evolve into rocky and/or icy planetesimals. The physical growth is accompanied by chemical, isotopic, dynamical, and thermal evolution of the protosolar disk material, processes important to understanding how the initial conditions determine the properties of the forming planetary systems (Apai and Lauretta 2009). Here we report evidence for establishing new constraints on the planetesimal formation process from newly available spectral measurements and mineralogical analysis of asteroids and unequilibrated meteorites that distinguish whether a chondrite was formed near the surface or in the interior of a planetesimal. This study illustrates, for the first time, i) that large groups of compositionally similar asteroids (clones) are a natural outcome of planetesimal formation, which direct implication is that meteorites within a given class can originate from several parent bodies ii) that the formation process of the H chondrite parent bodies must have been instantaneous which might be generalized to all planetesimals, and iii) the importance of radial mixing of disk material, the size-sorting of chondrules in particular, on the actual compositional heliocentric gradient among asteroids with LL parent bodies having formed – surprisingly - closer to the Sun than H ones.

Workshop Planet Validation

Du 13 au 15 mai 2013 - LAM

Workshop Planet Validation

Séminaire de revue de Rodrigo Ibata : Galactic Archaeology : The Great Dig in the Sky

Vendredi 17 mai 2013 11:00-12:00

I will review the motivation for using nearby galaxies and in particular the
Local Group as a means to study galaxy evolution and test cosmological
models. Deep spectroscopy is providing the key to interpret several
state-of-the-art panoramic imaging surveys of the Milky Way, the Andromeda
galaxy and their satellites, opening up a uniquely detailed view of the
structure and dynamics of these closest galaxies. In the two giant spirals,
we are now able to study the large-scale trends of galactic components and
uncover a rich archaeological record of ancient accretions. I will analyze
the consequences of these findings for our understanding of galaxy formation
and discuss the bright future of this field in the era of the next
generation of observatories/experiments (TMT, GAIA, LSST, JCMT, ELT,

Séminaire de revue de Max Pettini "Near-pristine gas at intermediate redshifts : a window on early nucleosynthesis"

Vendredi 24 mai 2013 11:00-12:00

It has now become recognised that damped Lyman alpha system—
gas clouds of neutral hydrogen observed in the high redshift
Universe—play an important role in helping us unravel the
origin of chemical elements. In this talk, I will describe the main
results of a recently completed survey of the most metal-poor DLAs,
aimed at complementing and extending studies of the oldest stars in
the Galaxy. The survey has clarified a number of lingering issues
concerning the abundances of C, N, O in the low metallicity regime,
has revealed the existence of DLA analogues to Carbon-enhanced
metal-poor stars, and is providing some of the most precise
measures of the primordial abundance of Deuterium. I will
conclude with a forward look to the promise of the next
generation of optical-infrared telescopes for this area
of research.

CosmoLens Workshop

Du 27 au 30 mai 2013 - LAM Amphitheater

Since the first, accurate detections about 15 years ago of giant arcs, arclets in galaxy clusters and cosmic shear of galaxies detected over large scales, gravitational lensing has achieved a fundamental role in the panorama of cosmological probes. As geometric probe of the space-time curvature, strong and weak lensing techniques represent privileged means to investigate the purely gravitational interactions, allowing terrific insight on the distribution and properties of the dominant clustered component of the Universe, the dark matter. On large scales gravitational lensing offers also a clean way to probe the dark energy, or departures from general relativity. Combined with other probes of galaxy clustering, SZ distortions or CMB anisotropies, gravitational lensing provides also powerful tools to explore the baryonic properties of the large scale structures, galaxy clusters, galaxies, eventually allowing to investigate the light-to-mass bias on several scales. Finally, the use lenses as gravitational telescopes permits to reach high redshifts, possibly up to the so-called Dark Ages, providing therefore an important way to investigate the late-time reionization history of the Universe. Impressive instrumental and observational efforts are world-wide ongoing, promoting projects based on CFHT, HST, UKIDSS, VISTA, VST, DECam, LSST, EUCLID as well as CMB experiments like Planck, ACT or SPT. All that contributes to a massive activity and interest in gravitational lensing.
Pursuing the same strategy of the very successful, previous international Cosmo- meetings hosted at Marseille/LAM since 2008 (*), with only invited speakers and free attendants (mainly Ph.D. students) Cosmo-Lens – International Meeting on Cosmology with Gravitational Lenses is an informal workshop-like short meeting to discuss the most recent progresses in the field of gravitational lensing applied to cosmology, aiming at consolidating existing collaborations and fostering new ideas and collaborations.
Aiming at offering an informal and productive ambiance, the attendance is limited to 50 people. All the contributions will be available online in pdf format.
Detailled Information and program here

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