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Accueil > Le Laboratoire > Séminaires et conférences > Past Seminars > Résumés 2015-2016

 Résumés 2015-2016

8 Jul 2016 - 11h

  • Richard A. Frazin (Michigan, USA)
  • Direct Imaging of Exoplanets from the Ground

A new generation of telescopes with mirror diameters of 20 m or more, called extremely large telescopes (ELTs) has the potential to provide unprecedented imaging and spectroscopy of exo-planetary systems, if the difficulties in achieving the extremely high dynamic range required to differentiate the planetary signal from the star can be overcome to a sufficient degree. Here, I will argue that millisecond imaging, which freezes the atmospheric turbulence, could potentially provide a breakthrough in the field, in that allows simultaneous and self-consistent determination of both the planetary image and the confounding aberrations in the optical system.

30 Jun 2016 - 11h

  • Francois Menard (IPAG, Grenoble)
  • Recent Results on Protoplanetary disks with SPHERE and ALMA

I will start by showing a gallery of images of protoplanetary disks recently obtained by SPHERE at the VLT. SPHERE, built in a large part in France, is extremely efficient to study disks and the images it is providing are quickly changing our understanding of disk evolution and planet formation.
In the second part of the talk, I will focus on two examples where SPHERE and ALMA images are coupled : HL Tauri and TW Hydrae. I will discuss the data and the modelling required to extract new information. The results will be placed in the context of early planet formation.

24 Jun 2016 - 11h

  • Jessica Lu (Hawaii, USA)
  • Stars In Motion : Impact in Star Formation, Compact Objects, and Galactic Centers

High-precision infrared astrometry has enabled unique experiments in many fields of astronomy, especially the study of the disk and center of our Galaxy. I will present results from our astrometric experiments to (1) test theories of star formation and the universality of the initial mass function, (2) search for free-floating stellar mass black holes using astrometric microlensing, and (3) study the dynamics and origin of young stars around the supermassive black hole at the Galactic Center. I will also discuss adaptive optics (AO) development efforts that improve astrometric precisions and expand AO to larger fields of view needed for sparse field astrometry.

17 Jun 2016 - 11h

  • Mark Lacy (NRAO, USA)
  • The Scientific Legacy of the Spitzer Space Telescope

In this talk I will give an overview of the science achieved by the Spitzer Space Telescope. I will focus on extragalactic science, but also include a description of some of the advances it enabled in other fields of astronomy. Some of Spitzer’s achievements have been predictable, but others were a complete surprise. When Spitzer was launched, it was hoped that it might detect galaxies out to z=3. It has since detected them out to z=11. A few exoplanets had been discovered, but characterizing them seemed impossible until Spitzer did it. These, and other discoveries, have left legacy that has guided the next generation of telescopes, and will remain unique for many years to come.

10 Jun 2016 - 11h

  • Rita Tojeiro (St. Andrews, UK)
  • The latest results from BOSS, lessons learnt and the future in eBOSS

The Baryon Acoustic Oscillation Survey (BOSS) is now complete, after an incredibly successful 5-year campaign. I will give a summary of the survey, present the latest measurements of the baryon acoustic oscillation scale and redshift-space distortions from BOSS data, and discuss their cosmological implications. I will conclude with lessons learnt from BOSS, and with an outlook into the future, particularly the recently-started eBOSS survey.

3 Jun 2016 - 11h

  • Michele Cappellari (Oxford, UK)
  • Galactic archaeology using integral-field spectroscopy

I review the progress in our understanding of galaxy structure and evolution brought by the advent of two-dimensional spectroscopic observations

27 May 2016 - 11h

  • Gabriel Tobie (Univ. of Nantes)
  • Habitability of subsurface oceans on icy moons

The exploration of Jupiter’s and Saturn’s system respectively by Galileo (1996-2003) and Cassini-Huygens (2004-2017), has revealed that several moons around Jupiter (Europa, Ganymede, Callisto) and around Saturn (Titan, Enceladus, Mimas) harbor a subsurface salty ocean underneath their cold icy surface. The composition of these oceans probably results from complex aqueous processes involving interactions between water, rock, organics and volatile compounds from which these bodies were built. Such aqueous processes were presumably vigorous during the early stage of interior differentiation when water and rock separated, but they could be still active in some icy bodies at present, as witnessed by the intense activity observed at Enceladus’ south pole by the Cassini spacecraft. The analysis of icy grains emitted from Enceladus indicates the presence of salt and organics mixed with ice, thus providing crucial constraints on the oceanic composition and indirect information on aqueous processes at its origin. The co-existence of water, organics and salts together with a strong heat source associated to tidal friction may potentially lead to the first bricks of life. Even if there is no direct evidence yet, similar ingredients might also be present within Europa, Titan and Pluto. Assessing the astrobiological potential of these oceanic environments require a better understanding of their present-day structure of the satellite interior as well as their possible evolution since their formation. In this seminar, I will give an overview of the current knowledge about the interior of icy moons, with a particular focus on Enceladus, Europa, Ganymede and Titan. I will discuss the possible occurrence of active aqueous processes on these bodies and the implications for the habitability of their subsurface oceans.

20 May 2016 - 11h (canceled)

  • A. Sacha Brun (CEA Saclay)

18 May 2016 11h

  • Jean-Claude Courteille (CNES)
  • Géopolitique et coopération spatiale internationale

Le secteur spatial est aujourd’hui structuré dans un mode de coopération internationale soutenu. D’un côté, nous avons la coopération institutionnelle bilatérale ou multilatérale et de l’autre, une activité commerciale et industrielle conduite dans un cadre d’appels d’offres lancés par des agences spatiales ou des opérateurs commerciaux. Une très grande partie du secteur est largement financé par les Etats et conduit dans le cadre de politique nationale. La France mène depuis le début des années 60 une politique active et engage des programmes ambitieux pour le pays mais aussi dans un cadre européen et international. L’activité spatiale internationale est souvent encadrée par des considérations géopolitiques issues de la guerre froide. Le sentiment de puissance et le besoin de conserver des leaderships dans les décisions des programmes spatiaux n’est souvent pas loin.

13 May 2016 - 11h

  • Richard Binzel (MIT, USA)
  • Pluto Revealed ! Latest Results from NASA’s New Horizons Mission

After nearly two decades of struggling for approval, a NASA funded Pluto mission finally reached the launch pad in January 2006. Nine-and-a-half years later in July 2015, the piano-sized New Horizons spacecraft reached the Pluto system revealing an amazingly bizarre planetary world. Ice mountains as tall as the Alps and smooth plains of frozen carbon monoxide 500 km across are just some of the surprising features. Pluto appears to be a globally changing planet with seasonal cycles ranging from decades to millennia producing an evolving landscape of nitrogen ice glaciers and variable atmospheric pressure. Together with its largest satellite, Pluto and Charon form a “double planet” system orbiting a common center of gravity located outside of either body. Charon’s surface also shows regions that are relatively young and crater-free, implying some recent era of geologic activity. Completing the system are four small moons found to be irregularly shaped with complex spin patterns in their own regularly spaced orbits. As New Horizons continues its voyage out of the solar system, a close encounter with at least one newly discovered Kuiper Belt object is possible within the next four years.

22 April 2016 - 11h

  • Tom Broadhurst (UPV/EHU, Spain)
  • Comparing the latest Hubble data with the first simulations of bosonic dark matter for the "No-WIMP Era

Heavy particles are not the only interpretation for the observed coldness of dark matter. Our new cosmological simulations of a cold Bose-Einstein state reveal an unknown world of standing waves that distinguish this cold wave-like dark matter, ψDM, from standard particle-CDM. Key predictions are verified with the Hubble Frontier Fields, and with local dwarf galaxy cores, QSO flux anomalies and GRB evolution. This exploration is timely because of the continued laboratory absence of WIMPs, and may establish light bosons as the most viable interpretation of dark matter.

4 April 2016 - 11h

  • Willy Benz (Bern, Switzerland)
  • Comets, Rosetta and the origin of the solar system

Comets have always been thought as relics from the early days of the solar system. ESA’s Rosetta mission by following the comet 67P/Churyumov-Gerasimenko along its trajectory, delivered for the first time not just a snapshot in time of a comet nucleus but its full time dependent evolution as it approached the sun. Just like the stone that gave the name to the mission, the wealth of data recorded provides a unique opportunity to help decipher the 4.5 billion yearlong story of the solar system. It turns out that the book is not so easy to read ! In this talk, we will show that when these data are coupled with the many progresses made over the past few years in particular due to the discovery of exoplanets, a consistent scenario reconciling many aspects of the problem is slowly emerging.

25 March 2016 - 11h

  • Gilles Chabrier (CRAL, ENS-Lyon)
  • Understanding the stellar Initial Mass Function and its possible variations ?

Understanding the origin of the IMF and finding out whether it is universal or varies with the environment remains one of the most fundamental problems of astrophysics. In this talk, I will present the analytical theory of the IMF, and its time-dependent extension, the star formation rate, derived recently by Hennebelle and Chabrier in the context of the modern gravo-turbulent scenario of star formation. The theory, which generalises the well-known Press-Schechter formalism of structure formation used in cosmology to the domain of star formation, naturally explains most of the observed properties of the IMF. Even more interestingly, the theory provides a physically grounded explanation for the bottom-heavy IMF inferred in the high redshift progenitors of massive early-type galaxies.

18 March 2016 - 11h

  • Richard Ellis (ESO and UCL)
  • Spectroscopic Studies of Galaxies in the Heart of the Reionization Era

Deep exposures with the Hubble Space Telescope (HST) have provided the primary evidence that star-forming galaxies were present in the first billion years of cosmic history. Sometime during this early period the intergalactic medium transitioned from a neutral gas to one that is fully ionized. How did this `cosmic reionization’ occur and were star-forming galaxies responsible ? Imaging of deep fields with HST’s Wide Field Camera 3 in conjunction with Spitzer photometry and Keck spectroscopy has provided important new insight into understanding when reionization occurred and the role of early galaxies in the process. Recent Planck results on the optical depth of electron scattering to CMB photons provide complementary information. A major question is to understand the properties and ionizing output of early galaxies for which spectroscopic studies are essential. I will review the progress in understanding the last missing piece in our overall picture of cosmic history and discuss the remaining challenges ahead of future facilities such as JWST and E-ELT.

11 March 2016 - 11h

  • François Boulanger (IAS, Orsay)
  • The polarization from interstellar dust and the cosmic microwave background

Planck, balloon and ground based experiments are measuring the polarization of the sky at sub-mm and mm wavelengths with unprecedented sensitivity. The observations are revealing a new sky we are discovering. The data analysis involves research in cosmology and Galactic astrophysics, which may be lead to a major discovery for fundamental physics. The main drive of the data gathering is to characterize CMB anisotropies in polarization, with sufficient accuracy and confidence to detect the expected signature from primordial gravity waves. At the same time, we are getting the data needed to characterize the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence, in the diffuse interstellar medium and molecular clouds. I will introduce these two research fields that have become interconnected, present current results and future perspectives.

2 March 2016 - 11h

  • Frederique Marion (LAPP, Annecy)
  • GW150914 : Observation d’un signal d’ondes gravitationnelles émis lors de la coalescence de deux trous noirs

Les ondes gravitationnelles sont d’infimes oscillations de la courbure de l’espace-temps prédites par la théorie de la relativité générale d’Einstein et engendrées lors de phénomènes violents dans l’Univers. Les collaborations LIGO et Virgo en ont fait la première détection directe le 14 septembre 2015. La source à l’origine du signal GW150914, la fusion de deux trous noirs environ 29 et 36 fois plus massifs que le Soleil, représente également une découverte majeure qui marque le début d’une nouvelle ère, celle de l’astronomie des ondes gravitationnelles. Le séminaire exposera cette découverte de manière pédagogique et accessible à tous : Le phénomène des ondes gravitationnelles sera expliqué avant de présenter le signal détecté et sa source, ainsi que les implications pour l’astrophysique et l’étude de la gravitation.

29 January 2016 - 11h

  • Chris Evans (Edinburgh, UK)
  • Near-IR spectroscopy of red supergiants : From the VLT to the ELTs

I will introduce a new technique to determine the metallicities of nearby galaxies using near-IR spectroscopy of red supergiant stars and massive super-star clusters. Following recent studies in the Galaxy and Magellanic Clouds to test this technique, I will present results from VLT-KMOS which demonstrate the potential of this method to establish the mass-metallicity relationship in the local Universe. I will conclude by presenting simulations of observations with the future Extremely Large Telescopes, with which it should be possible to obtain direct stellar abundances out to distances of tens of Mpc.

22 January 2016 - 11h

  • Alessandro Sozzetti (INAF)
  • Extrasolar Planets and Gaia : an Astrometry Revolution in the Making

Astrometry as a technique has so far proved of limited utility when employed as either a follow-up tool or to independently search for planetary mass companions orbiting nearby stars. However, this is bound to change by the end of this decade. I will briefly review the status of the Gaia mission, now in its third year of routine science operations. I will then outline the planet-finding capabilities of present and future astrometric observatories aiming at microarcsecond precision, with a particular focus on Gaia. Finally, I will put astrometry and Gaia in context, illustrating their potential for important contributions to exoplanetary science, as a complement to other indirect and direct methods for the detection and characterization of planetary systems.

15 January 2016 - 11h

  • Thierry Contini (IRAP)
  • The growth of galaxies along cosmic time : the MUSE perspective

Understanding the main processes of galaxy growth and how star formation is regulated over cosmic time is still a major challenge. I will present some results obtained so far with MUSE, a new generation and powerful 3D spectrograph on the ESO/VLT, mainly related to the growing processes of (low-mass) galaxies at intermediate and high redshift galaxies, and to the exchange of baryons between galaxies and their surrounding medium.

8 January 2016 - 11h (canceled)

  • Anne-Marie Lagrange (IPAG)

18 December 2015 - 11h

  • Masahiro Tadaka (IPMU, Japan)
  • SuMIRe : Subaru Measurements of Images and Redshifts

The Subaru telescope is one of the cutting-edge telescopes in the world, thanks to its 8.2m aperture, image quality and wide-field view. We, being led by the Kavli IPMU, are now working on further strengthening the unique capability of the Subaru telescope : we built the even wider field-of-view imaging camera, Hyper Suprime-Cam (HSC) and are also building the Prime Focus Spectrograph (PFS) based on the international collaborations including LAM as one of key institutes. This is the SuMiRe project. We will use these unique instruments to reveal the origin and fate of the Universe by elucidating the nature of dark matter and dark energy via precision imaging using the HSC as well as precision wide-field spectroscopy using the PFS. In this talk, I would like to tell what the SuMiRe project is and how we can tackle the scientific objectives by using these unique imaging and spectroscopy instruments. I also look forward to hearing inputs/ideas from expertises of wide-field galaxy surveys at LAM, as the HSC and PFS are such an amazing combination that offers the great potential to advance our understanding of the Universe.

11 December 2015 - 11h (canceled)

  • Rita Tojeiro (St. Andrews, UK)

4 December 2015 - 11h

  • Sylvie Vauclair (Toulouse)
  • La nouvelle musique des sphères (Un Livre un Auteur)

Dans le cadre des rencontres "Un Livre, un Auteur", organisées par le centre de documentation de l’OSU PYTHEAS et le LAM : conférence par Sylvie Vauclair sur le thème de son livre La nouvelle musique des sphères.

27 November 2015 - 11h

  • Olivier Mousis (LAM)
  • Cosmochemical constraints on the solar system formation and evolution

Formation scenarios of the solar nebula invoke two main reservoirs of water ice that may have taken part concurrently into the production of solids. In the first reservoir, which is located within the heliocentric distance of 30 AU, water ice infalling from the Interstellar Medium (ISM) initially vaporized into the hot inner part of the disk and condensed in its crystalline form during the cooling of the solar nebula. The second reservoir, located at larger heliocentric distances, is composed of water ice originating from ISM that did not suffer from vaporization when entering into the disk. In this reservoir, water ice remained mainly in its amorphous form. From these considerations, we discuss here the trapping conditions of volatiles in planetesimals produced within the outer solar nebula and their implications for the origin and composition of gas giant planets, their surrounding satellite systems and comets. In particular, we show that the formation of icy planetesimals agglomerated from clathrate hydrates in the solar nebula can explain in a consistent manner the volatiles enrichments measured at Jupiter and Saturn, as well as the composition of Titan’s atmosphere.

20 November 2015 - 11h

  • Silvia Bonoli (CEFCA, Spain)
  • The J-PAS survey : a picture of the sky in 56 colors

J-PAS is a planned large photometric survey which will scan 8000 deg^2 of the northern sky with 56 contiguous narrow-band filters that cover the entire optical range. The survey will be conducted from a dedicated 2.5m telescope recently built at the Observatorio Astrofisico de Javalambre, and equipped with a 4.7 deg^2, 1.2 Gpixel camera. Given its unique filter configuration and large field of view, the survey will effectively and efficiently provide a low-resolution spectra for every observed pixel, allowing an unprecedented precision in object classification and photometric-redshift estimation. The wealth of data that the survey will deliver are expected to provide significant contributions in many areas of astrophysics.
In this talk I will give a broad overview of the survey, from its technical description to its expected scientific impact, focusing in particular on cosmological experiments and galaxy evolution studies.

13 November 2015 - 11h

  • Suzanne Ramsay (ESO)
  • Studying feedback from massive stars using integral field spectroscopy

This seminar will describe two aspects of our work on the impact of massive stars on their surroundings. We will present a survey for massive outflows in regions where high mass candidates have been identified and the implication of this work for our understanding of the formation mechanism of massive stars. Recent results with KMOS on the Very Large Telescope (VLT) will be described. At the later stages of their evolution, massive stars disrupt their surroundings with the potential to either promote or to suppress on going star formation. Via observations with MUSE and KMOS, we are attempting make a quantitative comparison of models of feedback from massive stars with high quality, unbiased observations of star forming clouds. Results from MUSE observations of M16, the "Pillars of Creation" will be shown.

6 November 2015 - 11h

  • Florent Renaud (Surrey, UK)
  • Star formation in its context

Recent improvements of observational and numerical techniques have permitted to unveil the wide diversity of star forming clouds, in the Milky Way but also in other nearby galaxies. The variety in the morphology and dynamics of these clouds, as a function of their galactic environment, strongly suggests a complex interplay between global (kpc-scale) and local (pc-scale) processes, that remains to be fully understood. The coupling between large-scale structures, turbulence, self-gravity, magnetic fields and feedback makes this problem one of the most challenging of modern astrophysics, and has major implications for both the smaller and larger scales. Using a set of (sub)parsec-resolution hydrodynamical simulations of galaxies including local spirals, mergers and high redshift disks, I will illustrate the diversity of star formation in simulations and compare to what is observed. I will emphasise the role of the variation of physical conditions within a single disk galaxy, particularly focussing on star formation in galactic bars. I will then address the topic of starbursts by proposing a new theory to explain the intense star formation activity in interacting galaxies, and discuss the implication on fundamental aspects like the universality (or not) of the stellar initial mass function.

16 October 2015 - 11h

  • Melville (Mel) Ulmer (Northwestern, USA)
  • The Athena Mission : The Scientific Treasure Trove Brought about by Reaching the Golden Quadrant

The Athena mission will be the most ambitious ESA lead X-ray telescope ever launched in terms of collecting area focused onto a high resolution (baseline goal 2 eV at 6 keV) imaging detector. The detector is called the “Integral Field Unit” or IFU. The mission promises to revolutionize our knowledge of the “Hot Universe,” and the IFU coupled with the collecting area will be able to measure directly redshifts, infer plasma temperatures from line ratios, and bulk motion turbulences and more. Thus the mission will enable unique studies of the Hot Universe. A few examples detection and redshifts the first luminous black holes (AGNs) , track the chemical evolution of the Universe, tell us about the evolution on the intracluster medium, and the physics flaring objects from far (gamma ray burst after glow) to near (galactic) flare stars that could affect the habitability of rocky planets in the otherwise habitable zone. We will show how the complementary instrument the Wide Field Imager will play a key role in finding static (in time) targets of special interest as well as transient but rare phenomena that will de discovered when the WFI monitors hundreds to thousands of targets at once.

9 October 2015 - 11h

  • Stephanie Walch (Cologne, Germany)
  • The violent ISM in Milky Way-like disk galaxies

Molecular clouds are cold, dense, and turbulent filamentary structures that condense out of the multi-phase interstellar medium. They are also the sites of star formation. The minority of new-born stars is massive, but these stars are particularly important for the fate of their parental molecular clouds as their feedback drives turbulence and regulates star formation.
I will present results from the SILCC project (SImulating the Life Cycle of molecular Clouds), in which we study the formation and dispersal of molecular clouds within the multi-phase ISM using high-performance, three-dimensional simulations of representative pieces of disk galaxies. Apart from stellar feedback, self-gravity, an external stellar potential, and magnetic fields, we employ an accurate description of gas heating and cooling as well as a small chemical network including molecule formation and (self-)shielding from the interstellar radiation field. We study the impact of the supernova rate and the positioning of the supernova explosions with respect to the molecular gas in a well defined set of simulations. This allows us to draw conclusions on structure of the multi-phase ISM, the amount of molecular gas formed, and the onset of galactic outflows. Furthermore, we show how important stellar wind feedback is for regulating star formation in these disks.

2 October 2015 - 11h

  • Debora Sijacki (Cambridge, UK)
  • A new look at galaxy - black hole co-evolution

In this talk I will discuss which feedback mechanisms are needed to reproduce realistic stellar masses and galaxy morphologies in the present day Universe and argue that the black hole feedback is necessary for the quenching of massive galaxies. I will then demonstrate how black hole - host galaxy scaling relations depend on galaxy morphology and colour, highlighting the implications for the co-evolutionary picture between galaxies and their central black holes. In the second part of the talk I will present a novel method that permits to resolve gas flows around black holes all the way from large cosmological scales to the Bondi radii of black holes themselves. I will demonstrate that with this new numerical technique it is possible to estimate much more accurately gas properties in the vicinity of black holes than has been feasible before in galaxy and cosmological simulations, allowing to track reliably gas angular momentum transport from Mpc to pc scales. Finally, I will also discuss if AGN-driven outflows are more likely to be energy- or momentum-driven and what implications this has for the redshift evolution of black hole - host galaxy scaling relations.

25 September 2015 - 11h

  • Jean-Pierre LUMINET (LAM)
  • L’astronome de Samarcande (Un livre un auteur)

Dans le cadre des rencontres "Un Livre, un Auteur", organisées par le centre de documentation de l’OSU PYTHEAS et le LAM : conférence par Jean-Pierre Luminet sur le thème de son livre L’astronome de Samarcande.

18 September 2015 - 11h

  • Charles Bonatto (UFRGS, Brazil)
  • Star Clusters and the Star Formation Rate in the Milky Way

Star clusters usually form due to gravitational instabilities at the high-density parts (filaments) of giant molecular clouds. After formation, star clusters evolve driven both by internal and external dynamical mechanisms. At the earliest phases, most of the embedded star clusters dissolve into the field on a time-scale of a few 10^7 Myr. Later on, star clusters continue to lose mass by tidal interactions with Galactic substructures, shocks with giant molecular clouds, mass segregation and evaporation, and stellar evolution. As a consequence, the majority of the star clusters dissolve in the Galactic stellar field on a time scale of 10^8 Myr, leading to a nearly exponential-decay Age-Distribution Function (ADF). In this talk I’ll discuss how the star cluster dissolution mechanisms - coupled to the star-formation rate - shape the present-day ADF.

4 September 2015 - 11h

  • Lisa Hunter (UCSC)
  • Preparing the Next Generation of Scientists and Engineers for the Astronomy Workforce

The Institute for Scientist & Engineer Educators (ISEE, has been preparing graduate students, postdoctoral researchers, and professionals to be effective and inclusive educators for fifteen years. Each year, approximately 75 early career scientists and engineers enroll in an intensive program that complements research training by building skills that are often overlooked in graduate and postdoctoral programs, such as teaching, mentoring, leadership, and collaboration skills. ISEE now has alumni throughout the United States, and internationally, including a significant fraction working in astronomy related fields. To meet the needs of alumni, partners, and the workforce, ISEE has established regional “chapters” and is exploring mechanisms to expand internationally. This talk will include a discussion of how ISEE is addressing current gaps in American graduate and postdoctoral training, and more recent efforts to expand training to include international collaboration, project management, and other ways of supporting large scientific projects and facilities.

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