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Accueil > Le Laboratoire > Séminaires et conférences > Résumés

 Résumés

Remarque : les enregistrements des séminaires sont disponibles sur seminars.lam.fr.



28 June 2019 - 11h

  • TBD
  • TBD

TBD

21 June 2019 - 11h

  • Hendrik Hildebrandt (Alfa-Bonn)
  • TBD

TBD

14 June 2019 - 11h

  • Vianney Lebouteiller (Laboratoire AIM - CEA Saclay)
  • TBD

TBD

7 June 2019 - 11h

  • Nicolas Prantzos (IAP)
  • TBD

TBD

24 May 2019 - 11h

  • Lutz Wisotzki (Leibniz Institut für Astrophysik Potsdam AIP)
  • TBD

TBD

17 May 2019 - 11h

  • TBD
  • TBD

TBD

10 May 2019 - 11h

  • Serena Viti (UCL)
  • Characterizing the dense gas in galaxies

It is now well established that chemistry in external galaxies is rich
and complex. In this talk I will give an
overview of the field of Astrochemistry, with special emphasis on its
relevance to extragalactic studies.
I will show how molecules play a key role in the formation and shaping
of galaxies. By using examples from different
regions of space, from starburst regions, to gas surrounding AGNs, I
will demonstrate how
important molecules are for the characterization of galaxies. Finally I
will present a new approach for the
interpretation of molecules using Bayesian and Machine Learning
techniques.

3 May 2019 - 11h

  • TBD
  • TBD

TBD

26 April 2019 - 11h

  • Peter Capak (Caltech)
  • TBD

TBD

5 April 2019 - 11h

  • Roser Juanola-Parramon (NASA Goddard /UMBC)
  • Detecting exoplanets with the next generation of space telescopes : a technical perspective

Direct imaging of exoplanets in their habitable zone is extremely challenging due to two main factors : the proximity of the planet to the parent star and the flux ratio between the planet and the parent star, usually to the order of 10^-10 in the visible. In January 2016, NASA commissioned four Mission Concept Studies for the next Decadal Survey, which will decide which kind of mission will follow the steps of extremely successful telescopes like Hubble, and the future JWST and WFIRST. Of these four studies, two of them have as a primary scientific goal to detect and characterize exoplanets in their habitable zone.
These two missions are the Large UV-Optical-Infrared (LUVOIR) Surveyor and the Habitable exoplanet Imaging Mission (HabEx), which require large apertures and coronagraphs with active wavefront control to be able to suppress the starlight so faint planets can be detected and characterized adjacent to their parent star. The Extreme Coronagraph for Living Planet Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept. It is split into three channels : UV (200 to 400 nm), optical (400 nm to 850 nm), and NIR (850 nm to 2.0 microns), with each channel equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and separate science imagers and spectrographs.
The Apodized Pupil Lyot Coronagraph (APLC) is one of the baselined mask technologies to enable 10^-10 contrast observations in the habitable zones of nearby stars. The LUVOIR concept uses a large, segmented primary mirror (8- 15 meters in diameter) to meet its scientific objectives. For such an observatory architecture, the coronagraph performance depends on active wavefront sensing and control and metrology subsystems to compensate for errors in segment alignment (piston and tip/tilt), secondary mirror alignment, and global low-order wavefront errors. For the LUVOIR-A architecture (15m obscured telescope), we evaluate the sensitivity to segment-to-segment tip/tilt, piston, power (focus), astigmatism, coma, trefoil and spherical errors, and to errors induced by misalignment of the secondary mirror. I will present the latest results of the simulation of these effects and discuss the achieved contrast for exoplanet detection and characterization under these circumstances.

29 March 2019 - 11h

  • David Ehrenreich (U. Geneva)
  • Exoplanetary atmospheres at high spectral resolution

Observing transits of exoplanets with the Hubble Space Telescope in the ultraviolet has revealed spectacular atmospheric escape of strongly irradiated gas giants. This atmospheric photo-evaporation could explain the dearth of intermediate-mass planets close to their stars, as well as the valley separating two populations of super-Earths. The deposition of a tremendous amount of high-energy irradiation in the outer atmospheric layers of exoplanets should also impact their physical and chemical properties. I will review recent observations obtained wh ground-based, high-resolution spectrographs, that unveil the extreme conditions reigning in the upper atmospheres of exoplanets.

22 March 2019 - 11h

  • Coralie Neiner (LESIA, Observatoire de Meudon, France)
  • Space UV spectropolarimetry

In many domains of astrophysics, the study of magnetism and polarized light has become a new and essential tool. This has however never been done in the UV as it requires to go into space. I will present recent R&D work on UV polarimeters and current studies of space mission projects equipped with a high-resolution UV spectropolarimeter, such as Pollux for LUVOIR, Arago, or Lodestar.

15 March 2019 - 11h

  • Sebastian Kamann (Liverpool John Moores University)
  • Dynamical clues to the formation of star clusters

The star cluster population of the Milky Way provides a unique window to study the formation history of our Galaxy. The conditions of the epochs when the Milky Way built up most of its stellar mass are preserved in the star clusters we observe to date. However, the physics governing the formation of star clusters are still not entirely understood. For example, ancient globular clusters show subtle differences in the chemical compositions of their stars which appear to be absent in the clusters forming today. Does this suggest that cluster formation varies with mass or cosmic age ? In my presentation, I want to show how we can use the stellar dynamics of the clusters to answer such questions. Thanks to satellites such as Hubble or Gaia and powerful spectrographs we can nowadays study the motions of representative samples of stars in clusters of all ages. Using data from the MUSE spectrograph, we could already show that rotation played a crucial role in the formation of globular clusters and that they harbour larger populations of black holes than previously thought. We are further using the data to search for differences in the kinematics of their stellar populations. If detected, such differences put stringent constraints on the mechanisms that led to the formation of multiple populations in globular clusters.

8 March 2019 - 11h

  • Martin Crocce (IEEC-CSIC)
  • Accelerated Cosmic Expansion and the Dark Energy Survey

The striking discovery that the Cosmic expansion is not slowing down but accelerating has turned into one of the puzzles in Cosmology sparking large observational campaigns to map the Large Scale Structure and geometry of the Universe across cosmic time. I will briefly review this effort and then discuss The Dark Energy Survey (DES), a state-of-the-art large-scale galaxy survey designed to understand such acceleration by mapping 5000 deg2 measuring the positions and shapes for 300 million galaxies up to redshift 1, the light-curves of several thousand supernovae, and the masses of tens of thousands of galaxy clusters. I will present the latest cosmological results from the first year of observations, in particular those related to the combination of large-scale structure and weak gravitational lensing, how they compare with those from other datasets, and what to expect in the near future.

1 March 2019 - 11h

  • NISP Team (LAM)
  • NISP/EUCLID technical presentation and status

The NISP (Near Infrared Spectrometer and Photometer) is one of the two instruments to fly on the ESA Euclid spacecraft mid 2022. It operates in the near-IR spectral region (900-2000nm) as a photometer and spectrometer. The instrument is composed of :

  • a cold (135K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly, a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control system
  • a detection system based on a mosaic of 16 H2RG with their front-end readout electronic.
  • a warm electronic system (280K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the spacecraft via a 1553 bus for command and control and via Spacewire links for science data

We will present :

  • the Euclid spacecraft
  • the NISP final architecture, the different subsystems and the main performances
  • the NISP development plan, the test plan and the schedule
  • the NISP EM and FM integration

8 February 2019 - 11h

  • Erika Hamden (U. Arizona)
  • The FIREBall-2 UV balloon telescope and 2018 flight

In this talk, I will describe the telescope, instrument, and
flight of the Faint Intergalactic medium Redshifted Emission Balloon
(FIREBall-2). FIREBall-2 is a UV multi-object spectrograph fed by a 1
meter parabola mirror designed as a joint project between France and the
United States, with key components made at LAM (French PI- Bruno
Milliard). The instrument was designed to observe 4 pre-selected fields
and uses a UV optimized delta-doped EMCCD. The telescope flew on
September 22, 2018 from Fort Sumner, NM, as part of the fall CSBF
balloon campaign. The telescope collected data for several night hours
before being cut down. I will describe the testing, flight, and hardware
performance, along with some preliminary results and steps for the future.

1 February 2019 - 11h

  • Sera Markoff (API/GRAPPA, University of Amsterdam)
  • Imaging (and imagining) Black Holes

Black holes are one of the most exotic consequences of Einstein’s General Relativity, yet they are also very common players in the Universe, existing on scales ranging from the stellar up to beasts over a billion times more massive than our sun. Contrary to their reputation as cosmic vacuum cleaners, they actually serve as engines for extremely energetic processes, playing a major role in regulating the growth of galaxies. Some black holes also launch enormous jets of relativistic plasma that accelerate particles to energies millions of times higher than the Large Hadron Collider at CERN. Astronomers, astrophysicists and physicists all have reasons for wanting to understand black holes, yet we have been limited by the resolution of our telescopes from actually seeing one directly. This situation has changed dramatically with the coming of the Event Horizon Telescope, an Earth-sized array operating in the millimeter wavelength regime, that can actually make pictures of a couple of nearby supermassive black holes such as the one in our Galactic centre, Sgr A*, and the active galactic nucleus M87. I will briefly introduce the phenomenology of black hole accretion, and discuss some of the key problems we are still facing in terms of building a working model for these processes, and show some examples of the current cutting edge in modelling and interpretation. Along the way I will explain what the Event Horizon Telescope is, and how we anticipate the groundbreaking data from the first full run in April 2017 (note : I will not be able to show the results yet !) will help revolutionise our field and shed light on these complex environments.

25 January 2019 - 11h

  • Licia Verde (ICCUB)
  • The importance of bias

In cosmology bias is used in two different contexts. In one case it refers to systematic errors in a measurement or a determination of model’s parameters. In the other case it refers to the relation between the clustering of mass and that of observable tracers such as galaxies.
I will touch upon both aspects. I will highlight the importance of considering and modelling the effect of systematic errors and I will present a model of the halo bias in massive neutrinos cosmologies

18 January 2019 - 11h

  • Mark Sargent (Sussex)
  • Environment and interactions - How (not) to produce a starburst galaxy

Over the last 10 billion years the typical activity level of star-forming galaxies has decreased by more than an order of magnitude. Observations reveal that, at both low and and high redshift, there is a population of ’starburst’ galaxies that are significantly more active than the bulk of the rest of the population. Despite being comparatively rare, these starbursts are among the most popular targets for detailed studies of astrophysical processes, by virtue of being bright and thus readily observable. But what does it take to produce a starburst event during the peak epoch of galaxy formation at z 2, when even the average star-formation rate of the star-forming galaxy population was as high as locally observed only for the most extreme starbursting systems ?
In my talk I will present new measurements of the composition of the starburst population at z<2, in terms of its split into ’normal’ and interacting or merging galaxies. I will also review how a high star-formation efficiency - one of the trademarks of starburst events - is linked to galaxy environment based on the increasing body of literature on the interstellar medium in high-z galaxy clusters. Finally, I will discuss how measurements of host galaxy star-formation efficiency can provide clues on the interplay between starburst and AGN activity.

7 December 2018 - 11h

  • Pierre Beck (IPAG)
  • Shedding light on the darkest Solar System objects

Comets and most asteroids are extremely dark objets. They typically reflect only a few percent of the incoming light. I will discuss the nature of dark Solar System small bodies based on ground-based observations, in situ observation (i.e. VIRTIS / ROSETTA) and laboratory measurements. I will discuss in particular the case of C-type near-Earth asteroids, which are being targetted by two sample-return missions and how they might (or not) be representative of the main-belt population. Finally, I will discuss the case of cometary nuclei, possessing a peculiar absorption around 3-µm as observed by VIRTIS/ROSETTA. I will discuss how cometary nuclei relate to asteroid spectral-type and the nature of this spectral feature.

30 November 2018 - 11h

  • Chiara Caprini (APC Paris)
  • Cosmology with LISA

Gravitational waves can constitute a unique probe of both the early and late-time universe. After a general introduction to the subject, this seminar focuses on the potential of the space-based interferometer LISA to test cosmology. In particular, two aspects will be discussed : the stochastic gravitational wave background generated by sources in the very early universe, and the use of compact binaries, emitting gravitational waves, as standard sirens, i.e. to probe the energy content and the acceleration of the late-time universe.

23 November 2018 - 11h

  • Andrea Ferrara (SNS, Pise)
  • The Interstellar Medium of High Redshift Galaxies

In the last decade we have explored the cosmic depths and found a statistically significant number of galaxies well into the Epoch of Reionization. However, our physical knowledge of these pristine objects remains very scant. Investigating the internal structure, interstellar medium and evolution of early galaxies is the next challenge to understand key processes as the cosmic history of baryons, feedback, reionization and metal enrichment of the intergalactic medium, This ambitious plan can be tackled by combining a new generation of physically-rich, high resolution, zoom simulations with data in the sub-mm bands provided by ALMA. This approach will be soon strengthened by the forthcoming JWST power. I will review the present status and the open questions in the field.

16 November 2018 - 11h

  • Joel Vernet (ESO)
  • A multi-phase study of the Circum Galactic Medium in High-z radio galaxies with MUSE and ALMA

Radio galaxies (radio loud type-2 AGN) are among the most massive and luminous galaxies known at any redshift. They are found in high density environments (proto-clusters) and since the 1990s, it is known that they are surrounded by massive haloes extending to 150-200 kpc. These emission-line haloes extend well beyond the boundaries of the host galaxy, and form the link between its inter-stellar medium and the intra-cluster gas in the proto-cluster environment, i.e. the Circum Galactic Medium (CGM). They may well represent the accretion flows feeding the host galaxies with primordial gas from filamentary large-scale structures. The AGN is the flashlight illuminating and revealing these structures which play a crucial role in the galaxy formation process.
In this talk, I will present the results of an on-going VLT/MUSE and ALMA study of a sample of radio galaxies at 3<z<4.5 aimed at drawing a complete picture of the nature of these giant haloes in all possible phases : ionized, molecular, atomic, neutral.

9 November 2018 - 11h

  • Coralie Neiner (LESIA)
  • TBD

TBD

26 October 2018 - 11h

  • TBD
  • TBD

TBD

19 October 2018 - 11h

  • Vanessa Bailey (JPL)
  • Status and Potential Scientific Capabilities of the WFIRST Coronagraph Instrument

The Coronagraph Instrument (CGI) for NASA’s Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current direct imaging facilities by 2-3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime, and by validating instrument and telescope models at unprecedented levels of precision. I will discuss the status of the instrument design, some of its key new technologies, and its potential science yield.

12 October 2018 - 11h

  • TBD
  • TBD

TBD

5 October 2018 - 11h

  • Benoit Neichel (LAM)
  • HARMONI au LAM : science, optique adaptative, designs, réalisations et intégrations

HARMONI est l’un des 3 instruments de première lumière qui équipera l’Extremely Large Telescope Européen, le futur télescope Européen de 39m de diamètre. HARMONI est un spectrographe à intégral de champ (IFU), mono-objet, qui observera dans la gamme visible et proche infra-rouge (de .5 à 2.4 microns). HARMONI fournira une résolution spectrale de R=3000 à R=20000, et une résolution angulaire de 60 à 4 mas. Pour exploiter pleinement la limite de diffraction de l’E-ELT, HARMONI sera équipé de deux systèmes d’Optique Adaptative (OA). Le premier est un système d’OA classique (SCAO) et le deuxième sera un système d’OA grand champ, assisté par étoiles lasers (LTAO). HARMONI s’inscrit dans la lignée d’instruments qui équipent le VLT, tels que SINFONI ou MUSE, et la première lumière est prévue pour 2025. Les cas scientifiques principaux d’HARMONI couvrent un large spectre, depuis l’étude et la caractérisation des exo-planètes, l’étude des populations stellaire dans les galaxies proches, et jusqu’aux galaxies à grand décalage vers le rouge. HARMONI regroupe un consortium de 6 laboratoires, dont 2 Français (LAM et CRAL). Les équipes du LAM sont en charge de la réalisation de plusieurs sous-systèmes, dont les analyseurs de surface d’onde pour l’optique adaptative.
Dans cette présentation, nous donnerons un statut du projet HARMONI et des développements actuellement en cours au LAM. En particulier, on détaillera quelques cas scientifiques d’intérêt pour les chercheurs du LAM, on présentera le concept d’instrument et son Optique Adaptative, on développera les designs réalisés par les équipes techniques du LAM et on abordera le planning de l’instrument, et les phases de tests qui se réaliseront au LAM. HARMONI est l’un des grands projets développé au LAM, et ce séminaire, à l’attention de tous les personnel du laboratoire, sera l’occasion de mettre en avant les contributions du LAM et d’échanger avec les personnels impliqués dans le projet.

28 September 2018 - 11h

  • Bernard Marty (CRPG Nancy)
  • TBD

TBD

14 September 2018 - 11h

  • Caroline Dorn (Univ Zurich)
  • Interior characterization in multiplanetary systems : TRAPPIST-1

I will start with a general introduction to the interior characterization of exoplanets. There are two kinds of data available for interior characterization. There are astrophysical observations that provide us planetary mass and radius for example, and there are data informed from theory or experiments. Both kinds of data are generally few with large uncertainties. By using Bayesian inference analysis, these uncertainties can be formally taken into account.
In a second part, I will focus on the specific case of TRAPPIST 1. Interior characterization traditionally relies on individual planetary properties, ignoring correlations between different planets of the same system. We explore such correlations and data specific to the multiplanetary-system TRAPPIST-1 and study their value for our understanding of their formation and evolution.



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