Lundi 21 Novembre

10h – 10h20 Météores : à la recherche de ce qui n’existe déjà plus Auriane Egal - IMCCE

D’où proviennent les pluies de météores que nous avons la chance d’observer tout au long de l’année ? Pourquoi est-ce si difficile de retrouver les corps parents à l’origine de ces phénomènes ? La réponse à cette question repose en majeure partie sur l’imprécision de la détermination de la vitesse des météores dans l’atmosphère. Depuis la simple utilisation de témoignages visuels jusqu’au développement de réseaux de caméras ultra-sophistiquées, tout est mis en oeuvre pour tenter de contraindre davantage ce paramètre indispensable. Et vous, en seriez-vous capable ?

10h20 – 10h40 Kinematics of Class 0 protostellar envelopes from the CALYPSO survey : the L1527 case study Mathilde Gaudel, Anaëlle Maury and CALYPSO collaboration - SAp/AIM

One of the main challenges to the formation of Sun-like stars is the “angular momentum problem” : if the angular momentum of the gas contained in a typical star-forming core is totally transfered to the star during the main accretion phase, called Class 0 phase, the star can not be stable. The gas needs to loose most of its angular momentum. At the end of this accretion phase, a large disk ( 100 AU) of dust, where planets will form later, surrounded the protostar. Can the disk formation is the solution to the angular momentum problem ? Studying the kinematics and understanding the distribution of the angular momentum in Class 0 protostellar envelopes (10 - 10 000 AU) is of uttermost importance to find a solution to this problem. In order to tackle this issue, the CALYPSO (Continuum and Lines in Young Protostellar Objects) IRAM large program provides observations with Plateau de Bure Interferometer and the IRAM 30m telescope of the dust continuum and a dozen molecular lines emission from a large sample of 17 Class 0 protostars. We used the C18O(2- 1) and N2H+(1- 0) molecular lines for tracing envelope’s kinematics. We chose L1527, a borderline Class 0/I object located in the Taurus molecular cloud at 140pc, as a pilot source to ensure our methods are reliably reproducing results from the literature, abundant for this source. Our results are consistent with previous studies and for the first time, we have an estimation of the angular momentum for a single source at different scales in the envelope. We are now ready to do a similar analysis for the other 16 Class 0 protostars from the CALYPSO sample.

10h40 – 11h High-redshift major mergers weakly enhance star formation Jérémy Fensch, Renaud F., Bournaud F., Duc P.-A. et al. - SAp AIM

Galaxy mergers are believed to trigger strong starbursts. This is well assessed by observations in the local Universe. However the efficiency of this mechanism has poorly been tested so far for high redshift, actively star forming, galaxies. We present a suite of pc-resolution hydrodynamical numerical simulations to compare the star formation process along a merging sequence of high and low z galaxies, by varying the gas mass fraction between the two models. We show that, for the same orbit, high-redshift gas-rich mergers are less efficient than low-redshift ones at producing starbursts : the star formation rate excess induced by the merger and its duration are both around 10 times lower than in the low gas fraction case. The mechanisms that account for the star formation triggering at low redshift are only mildly, if not at all, enhanced for high gas fraction galaxy encounters. Our results are consistent with the observed increase of the number of major mergers with increasing redshift being faster than the respective increase in the number of starburst galaxies. 11h30 – 11h50 Validation de l’étoile laser allongée Lisa Bardou - LESIA

En optique adaptative, pour pouvoir corriger la turbulence atmosphérique, on a besoin de s’aider d’une étoile brillante. Cette étoile guide sert à mesurer le front d’onde turbulent, mais cette mesure est valable uniquement près de ladite étoile. Une large portion du ciel reste alors inaccessible aux observations à haute résolution angulaire. Pour palier ce problème, on utilise des lasers qui créent des étoiles guides artificielles où l’on veut dans le ciel. Aujourd’hui ces étoiles laser sont en service sur les plus grands télescopes (Keck, VLT, Gemini South, etc.). L’Europe a pour projet de construire un nouveau télescope géant de 40m de diamètre. Avec un télescope aussi grand, de nouveaux problèmes apparaissent lors de l’utilisation de ces étoiles artificielles, qui sont pourtant nécessaires pour pouvoir exploiter au maximum le pouvoir de résolution exceptionnel de ce futur télescope. Je vais présenter ici quels sont ces problèmes et l’expérience que l’on a mise en place pour déterminer comment y remédier.

11h50 – 12h10 Decimetre-scaled spectrophotometric properties of the nucleus of comet 67P/Churyumov- Gerasimenko from OSIRIS observations Clément Feller, S. Fornasier, P.H. Hasselmann, A. Barucci, F. Preusker et al. - LESIA

We present the results of the photometric and spectrophotometric properties of the 67P/Churyumov- Gerasimenko nucleus derived with the OSIRIS instrument during the closest fly-by over the comet, which took place on 14 th February 2015 at a distance of 6 km from the surface. Several images covering the 0°-33° phase angle range were acquired, and the spatial resolution achieved was 11 cm/pxl. The flown-by region is located on the big lobe of the comet, near the borders of the Ash, Apis and Imhotep regions. Our analysis shows that this region features local heterogeneities at the decimetre scale. We observed difference of reflectance up to 40% between bright spots and sombre regions, and spectral slope variations up to 50%. The spectral reddening effect observed globally on the comet surface by Fornasier et al. (2015) is also observed locally on this region, but with a less steep behaviour. We note that numerous metre-sized boulders, which exhibit a smaller opposition effect, also appear spectrally redder than their surroundings. In this region, we found no evidence linking observed bright spots to exposed water-ice-rich material. We fitted our dataset using the Hapke 2008 photometric model. The region overflown is globally as dark as the whole nucleus (geometric albedo of 6.8%) and it has a high porosity value in the uppermost-layers (86%). These results of the photometric analysis at a decimetre scale indicate that the photometric properties of the flown-by region are similar to those previously found for the whole nucleus.

12h10 – 12h30 Three-dimensional turbulence-resolving modeling of the Venusian cloud layer and induced gravity waves. Maxence Lefèvre - LMD

The impact of the cloud convective layer of the atmosphere of Venus on the global circulation remains unclear. The recent observations of gravity waves at the top of the cloud by the Venus Express mission provided some answers. These waves are not resolved at the scale of global circulation models (GCM), therefore we developed an unprecedented 3D turbulence-resolving Large-Eddy Simulations (LES) Venusian model using the Weather Research and Forecast terrestrial model. The forcing consists of three different heating rates : two radiative ones for solar and infrared and one associated with the adiabatic cooling/warming of the global circulation. The rates are extracted from the Laboratoire de Météorlogie Dynamique (LMD) Venus GCM using two different cloud models. Therefore we are able to characterize the convection and associated gravity waves in function of latitude and local time. To assess the impact of the global circulation on the convective layer, we ran simulation using heating rates from a 1D radiative-convective model.

12h30 – 12h50 Can we see neutrino flares ? Exploring the source parameter space for detectability. Claire Guépin, Kumiko Kotera - IAP

The new generation of powerful instruments are reaching sensitivities and temporal resolutions that will allow a multi-messengers detection of transient phenomena. In this study, we explore the parameter-space of flaring sources (in particular in terms of luminosity, time-variability or emission energy band) that would enable the detection of transient neutrino signatures. We consider neutrinos produced by photo-hadronic interactions on various photon fields in the source. We give robust necessary conditions on the photon flux from the sources to ensure the detection of neutrinos from current and upcoming experiments.

14h – 14h40 Revue

14h40 – 15h Prédire les ondes gravitationnelles de binaires compactes grâce à la théorie post-newtonienne Tanguy Marchand, Blanchet, Faye - IAP

Grâce à la récente détection d’ondes gravitationnelles par l’expérience LIGO, une nouvelle fenêtre sur l’univers s’ouvre en astrophysique. Il est maintenant possible d’observer directement l’empreinte sur l’espace-temps de la fusion de deux trous noirs. Cette nouvelle physique offre d’immenses perspectives aussi bien pour etudier nos modèles astrophysiques que pour tester au niveau fondamental la theorie de la relativité générale. Cependant, il est nécessaire de pouvoir prédire avec précision les signaux emis par les sources attendues afin de pouvoir les détecter et les analyser. Dans ce contexte, la théorie post-newtonienne, consistant à résoudre de façon pertubative les équations d’Einstein, joue un rôle crucial et permet, utilisé de pair avec des simulations numériques, de construire des patrons d’ondes précis des signaux émis par la coalescence de deux objets compacts. Après avoir expliqué les fondements du post-newtonien, nous verrons les récents développements et les nouveaux défis de ce domaine. En particulier, nous verrons comment cette théorie prend en compte les non-linéarités de la relativité générale à un ordre très élevé lors de l’émission et de la propagation des ondes gravitationnelles.

15h – 15h20 Searching for high-redshift galaxy clusters Benjamin Clarenc - IAS

Les galaxies sont des objets à la frontière entre astrophysique et cosmologie. Leur formation et leur évolution sont encore mal connues, en particulier celles des galaxies au sein des amas. En effet, les amas locaux sont matures et leur galaxies vieilles, ne produisant (presque) plus d’étoiles, alors que les galaxies isolées (dites de champ) sont en partie dans leur phase de formation stellaire. Tout porte donc à croire que l’environnement d’une galaxie est un paramètre fondamental dans son évolution et qu’il l’accélère. Pour comprendre le rôle de cet environnement, il est indispensable d’observer des amas au sein desquels les galaxies sont en formation, c’est-à-dire des amas jeunes, eux-mêmes en cours de formation, et donc à grand redshift. Mais leur observation est difficile, seule une poignée a été confirmée à z>1.5, et les méthodes de sélection biaisent sans nul doute les propriétés statistiques que l’on peut tirer pour le moment. Je présente ici un échantillon de quelques dizaines de candidats (proto-)amas de galaxies à grand redshift, issus d’une sélection Planck/HFI + Herschel/SPIRE + Spitzer/IRAC, dont certains ont été confirmés spectroscopiquement, ainsi que quelques résultats de photométrie en infrarouge proche.

15h20 – 15h40 Post-coronagraphic wave-front sensing for the direct detection of exoplanets: taking atmospheric turbulence into account. Olivier Herscovici-Schiller - ONERA

Context: Direct detection of exoplanets is limited by the presence of speckles on scientific images. The origin of these speckles is quasi-static aberrations in the optical system. In a high-contrast imaging system without residual turbulence, or for a ground-based adaptive optics-corrected telescope recording short exposures, the on-axis coronagraphic point spread function of the system can easily be computed as a function of the instantaneous aberrations (quasi- static and turbulence-induced).

Point of the presentation: In the case of a ground-based telescope, with typical exposure times of several tens of seconds to minutes, turbulence, even in the form of residual turbulence of an extreme adaptive optics system, must be taken into account. In this presentation, we present an exact analytic expression for the long exposure coronagraphic point spread function in the presence of residual turbulence. We use this expression to extend a wave front sensing technique called coronagraphic phase diversity to be able to measure and correct quasi-static aberrations during the scientific exposure.

16h10 – 16h30 Collisional streaming instability in astrophysical plasmas Loïc Nicolas- LPP/LERMA

L’instabilité faisceau-plasma se produit lorsqu’un plasma en traverse un autre le long d’un champ magnétique. Des ondes sont alors générées et des échanges d’énergie sont possibles entre les plasmas. L’ajout de collisions entre les ions dans les plasmas introduisent un nouvel élément responsable d’échanges d’énergies, qui peut affecter le développement de l’instabilité selon les conditions dans lesquelles on se place. On peut alors observer les régimes dans lesquels chaque phénomène domine.

16h30 – 16h50 Evolutions, climats et observations possibles de Proxima b, l’exoplanète la plus proche de la Terre Martin Turbet - LMD

Le 24 Août dernier, une équipe internationale de chercheurs a annoncé la découverte d’une planète orbitant autour de Proxima du Centaure. C’est et ce sera par définition l’exoplanète la plus proche de nous jamais découverte. Mieux encore, cette exoplanète est 1. très probablement rocheuse et 2. située dans la Zone Habitable de son étoile, là où l’eau liquide peut exister en surface. Après avoir brièvement rappelé en quoi consiste cette découverte, je présenterai les résultats de récents travaux (Ribas et al. 2016 ; Turbet et al. 2016) étudiant l’ « habitabilité » de la planète Proxima b. Dans un premier temps, j’aborderai la question de l’évolution de la planète depuis sa formation, il y a 4.8 milliards d’années. L’histoire de Proxima b et de son étoile a été radicalement différente de celle de la Terre et du Soleil. La formation de Proxima b, son irradiation par son étoile, les forces de marées qu’elle subit et qui affectent sa structure interne et sa rotation, n’ont pas d’équivalent dans l’histoire de notre planète. Dans un deuxième temps, je présenterai les résultats de simulations numériques 3D du climat de la planète pour différents scénarios d’évolution. J’expliquerai également en quoi ces simulations sont importantes pour préparer et prédire les résultats de futures observations par photométrie à partir de 2018 avec le James Webb Space Telescope ou par imagerie directe avec les grands télescopes de prochaine génération (ELT, GMT, TMT ...) dont la mise en service va débuter d’ici dix ans. Ces observations pourront nous dire si Proxima b possède ou non de l’eau, une atmosphère et un climat habitable.

17h – 18h Conférence :

La relativité du mouvement Jan Lacki - UNIGE

Si l’on se réfère aux anniversaires et aux lieux communs, la relativité est vieille d’environ un siècle (les articles historiques d’Einstein, 1905 – 1915). En fait, l’examen historique du cours d’idées qui conduira à la formulation de la relativité générale par Einstein montre qu’il faut faire commencer cette histoire bien plus tôt et remonter en tout cas jusqu’à Galilée. Pour comprendre et apprécier à sa juste valeur la trame conceptuelle sous-jacente, il faut avant tout restaurer au terme de « relativité » sa juste signification. C’est celle de la relativité du mouvement, dont les relativisations des déterminations spatiales et temporelles, emblématiques de l’œuvre d’Einstein, ne sont que des retombées. Mon intervention se propose d'examiner les points saillants de cette aventure intellectuelle, qui, à travers la thématique de la relativité du mouvement, permet de reconstruire un grand pan de la physique contemporaine.

Mardi 22 Novembre

9h30 – 10h10 Revue The origin of solar eruptive events Sophie Masson, F. Zuccarello, G. Aulanier, S. K. Antiochos and C. R. DeVore - LESIA

Solar eruptions are one of the most spectacular and violent phenomena that occur in the Sun’s atmosphere. Together with solar flares they are the most impulsive and energetic manifestation of solar activity. Coronal mass ejections (CMEs) are magnetized bubble of coronal plasma ejected into the interplanetary medium. Sometimes, they propagate up to the Earth and interact with the magnetosphere triggering various phenomena that directly affect the human activity (e.g. Communication, spacecraft trajectory, power outage…). Understanding how those CMEs are triggered is of course important in the context of space weather, but it can also improve our basic understanding of energy release in natural plasma. Before erupting, a CME consists of a magnetic flux tube that is more or less twisted and/or sheared, hereafter called flux rope. This flux rope is usually confined in a larger multipolar magnetic field and can be stable for hours or even days before suddenly erupting. Even though observational criteria have been defined, the triggering mechanism of CMEs is still under debate. The two main candidates are: 1) an ideal magnetohydrodynamic (MHD) instability, which depends on the global properties of both the flux rope and the ambient magnetic field and 2) a resistive MHD instability which develops locally allowing magnetic reconnection to occur eventually leading to a change of force balance. While those two mechanisms are very different, it is very challenging to determine which one is responsible of the eruption. Mainly investigated using MHD simulations, the initial conditions (boundaries, ambient magnetic field and plasma), the energy injection process (photospheric flows, insertion of unstable flux rope) and the MHD code used lead to very different results which are not directly comparable, and so far, it did not allow the community to firmly identify the triggering mechanism. I will first present these models and detail the results. I will show how observations may help to constrain these models and finally I will discuss their significance and how further advances can be achieved to answer this long-lasting outstanding question of the CME’s trigger.

10h10 – 10h30 Deriving comprehensive error breakdown for wide field adaptive optics systems using end-to-end simulations Florian Ferreira - LESIA

The future European Extremely Large Telescope (E-ELT) adaptive optics (AO) systems will aim at wide field correction and large sky coverage. Their performance will be improved by using post processing techniques, such as point spread function (PSF) deconvolution. The PSF estimation involves characterization of the different error sources in the AO system. Such error contributors are difficult to estimate : simulation tools are a good way to do that. We have developed in COMPASS (COMputing Platform for Adaptive opticS Systems), an end-to-end simulation tool using GPU (Graphics Processing Unit) acceleration, an estimation tool that provides a comprehensive error budget by the outputs of a single simulation run.

10h30 – 10h50 APSIS ou la photochimie atmosphérique Titan en laboratoire Sarah Tigrine, Nathalie Carrasco, Ludovic Vettier, Guy Cernogora – LATMOS/synchrotron SOLEIL

Titan, le plus grand satellite de Saturne, possède une atmosphère dense dont les couches supérieures sont majoritairement composées de méthane (CH4) et de diazote (N2). Grâce à la mission Cassini (NASA), nous savons maintenant que l’interaction entre ces molécules et le rayonnement solaire VUV ouvre la voie à une chimie organique complexe, même à des altitudes supérieures à 800 km. Cette physico-chimie très efficace fait de Titan un laboratoire naturel pour observer et mieux comprendre des réactions de type pré-biotique ; mais malgré toutes les données collectées par les instruments de Cassini, tous les processus photochimiques possibles dans un environnement riche à la fois en composés azotés et en hydrocarbures ne sont pas connus avec précision. C’est pourquoi les expériences de labo qui recréent des conditions type atmosphère de Titan sont très appréciées, en complément des données spatiales et/ou obtenues depuis le sol (avec ALMA par ex.). Au LATMOS, nous avons mis au point l’expérience APSIS qui couple un réacteur photochimique avec une source plasma VUV. Le diagnostic s’effectue par spectrométrie de masse. Notre source VUV permet de tester les réactions photochimiques à des longueurs d’onde différentes, ce qui permet de mieux cerner les paramètres clé gouvernant un tel système, notamment à la lumière des données Cassini ou d’autres expériences de laboratoire.

10h50 – 11h10 Etude des anneaux de Chariklo par occultation stellaire Diane Bérard - LESIA

On pensait que les anneaux n’existaient qu’autour des planètes géantes gazeuses. En 2013, des anneaux ont été découvert autour du plus gros centaure : Chariklo, astéroïde de 250 km de diamètre. Grâce à la méthode des occultations stellaires il nous est possible de les caractériser et donc de mieux comprendre leur formation et leur origine. Je présenterai les résultats des occultations de 2014 et 2015 qui nous apporte une première caractérisation de ces anneaux.

11h30 – 11h50 Formation of pseudo-bulges in giant local spiral galaxies via gas-rich major mergers Tabatha Sauvaget, François Hammer, Mathieu Puech - GEPI

Spiral galaxies represent about 70% of the intermediate-mass galaxies (typically with a mass between 3 and 8 x 10^10 solar masses) in the local Universe. The widely accepted scenario for their formation is a gradual accretion of gas to form a disk structure. But over the past decade, observations and simulations have suggested that most present-day spiral galaxies could have formed via gas-rich major mergers (gas fraction of progenitors > 50%) in the past 10 Gyr, during which the gas inherits its angular momentum from the orbital momentum of the merger. This process allows the gas to redistribute itself in a disk structure after the merger. Gas-rich mergers can change dramatically the properties of the merger remnant because gas can damp the violent relaxation occuring in the stellar phase. This high gas fraction in progenitors plays a significant role in the formation of bulges, which is still debated. While classical bulges have been associated to the result of major mergers, pseudo-bulges have been rather associated to secular evolution. However, the cosmological Λ-CDM model predicts a hierarchical growth of galaxies via mergers but pseudo- bulges are found in > 50% of large nearby spiral galaxies. So could we build pseudo-bulges with gas-rich major mergers ? Thanks to N-body/SPH simulations (GADGET-2) of gas-rich major mergers, we reproduce spiral local intermediate-mass galaxies with pseudo-bulges or bulgeless. Now we are exploring the parameter space to see what is the influence of parameters on results. We also study several observational samples to determine the exact proportion of this type of galaxies in the local Universe and to compare with simulations.

11h50 – 12h10 Turbulent heating over the Sun. Victor Montagud - LPP

Witnessed for the first time by a lonely satellite more than forty years ago, the heating of the solar wind remains as an unsolved mystery in the field of astrophysics. Nevertheless, evidences accumulated over the years point towards one particular suspect that might have been able to cause the anomalous slow down of the proton temperature cooling with distance : the turbulence. In hydrodynamics, turbulence is the process by which the energy of big structures, like eddies, is used to produce smaller and smaller eddies until they reach the molecular scales, where the energy of the structures is transferred into heat, by collisions or other ways. Consequently, this process increases the energy dissipation and consequently the heating of the system. A similar phenomenon takes place in the interplanetary plasma although with a more complex phenomenology than that of neutral fluids. Via a 3D MHD numerical model that accounts for the radial expansion of the solar wind, I try to reproduce the conditions of the plasma that develop a turbulence able to produce the same heating observed in observational data of the solar wind at 1 AU. To this end and based on the results of studying the spectral spectral anisotropy of the solar wind that have been done in my group, I choose initial energy spectra with a different shape for slow and for fast winds. As a result of this choice of parameters, we are close to be able to reproduce the turbulent heating observed in the data. Further work concerning new simulations at higher Reynolds and Mach numbers will be done to achieve the same large heating rate in a turbulent regime comparable to that of the solar wind.

12h10 – 12h30 Grooving to SKA Noise Evan Eames, Benoît Semelin - LERMA

It is difficult to look at things that are far away because it is noisy. Is it too noisy ? Current research suggests : maybe.

12h30 – 12h50 Electron-Positron pair creation on a soft photon background revisited and consequences on the gamma ray Universe transparency Guillaume Voisin, Fabrice Mottez, Silvano Bonazzola - LUTh

Creations of electron-positron pairs on a soft photon background and subsequent destruction of the two progenitor photons are important elements in various astrophysical contexts. In particular, pair cascades in pulsar and magnetar magnetospheres and annihilation of gamma-rays on the extragalactic background light (EBL) are two active topics. We show that the usual formula giving the rate of this process is flawed and present our own derivation. Moreover we present semi- analytical derivations of the pair spectrum that was never done before to our kowledge. We then proceed to estimate the consequences on the propagation of gamma rays on the different radiationbackgrounds, in particular the cosmic microwave background and the EBL. We show that gamma ray horizons might be up to a factor of two larger than expected.

14h – 14h40 Revue Objets compacts et phénomènes associés Frédéric Daigne – IAP, UPMC

Les objets compacts (naines blanches, étoiles à neutrons et trous noirs) sont parmi les astres les plus fascinants rencontrés dans l'Univers. L'étude de la structure de l'espace-temps à leur voisinage, et de leur structure interne dans le cas des étoiles à neutrons, permet de sonder des conditions extrêmes en terme de gravité ou de densité de la matière. Leur formation libère une énergie gravitationnelle énorme qui les associe à des phénomènes explosifs spectaculaires tels les supernovae ou les sursauts gamma. Une fois formés, les étoiles à neutrons et les trous noirs sont dessources de rayonnement puissantes, en particulier dans le domaine des rayons X et gamma : rayonnement « pulsar » des étoiles à neutrons, rayonnement associé à l’accrétion de matière arrachée à une étoile compagnon ou à l'environnement, … Dans certains cas, ces sources sont mêmes capables d'éjecter de la matière à des vitesses très proches de celle de la lumière. Enfin, les étoiles à neutrons et les trous noirs sont au coeur des sources discutées dans le cadre de l’émergence de l’astronomie multi-messagers, avec en particulier la première détection directe d’ondes gravitationnelles en 2015. Cet exposé passera en revue ces différents sujets en mettant l'accent sur les questions reliées aux observations les plus récentes.

14h40 – 15h Lidar and Satellite Measurements of Mesospheric Temperature Robin Wing - LATMOS

A brief summary of the lidar techniques employed by two co-located NDACC lidars at Observatoire de Haute Provence (44°N, 6°E) will be given. The measurements made using these two lidars allow us to infer a nightly temperature profile in the stratosphere and mesosphere. We use a 30 year record of these lidar temperatures to make a systematic comparison with temperatures derived from MLS and SABER satellite observations. The ground-based lidars and satellites show good agreement in temperature estimates below 70 km altitude but, have significant differences in the upper mesosphere.

15h – 15h20 HST Grism Confirmation Results of the 20 Densest CARLA Candidate Galaxy Clusters at 1.4 < z < 2.8 Gaël Noirot - LERMA

Galaxy clusters form in the densest regions of the universe and are unique laboratories for studying growth of structures over cosmic time. The most distant galaxy clusters are particularly interesting to test different models of structure formation and evolution. Indeed, transition from high-redshift, star-forming, loose overdensities (aka proto-clusters at z>2) to lower-redshift (z<1) massive, collapsed clusters dominated by passive galaxies is still elusive due to the lack of well-studied sample-size confirmed clusters at z>1.4. I will present the results of our 40-orbit Hubble Space Telescope program on the 20 densest CARLA cluster candidates at 1.4

15h20 – 15h40 Interstellar 3D maps Letizia Capitanio - GEPI

Using more and more precise stellar distances - thank you GAIA ! - we are able to re-design the 3D local interstellar medium maps . This maps use different extinction proxy : colour excess, DIB, statistical survey. We want to understand if we can use them together, how huge surveys could reinforce our maps, how our inversion techniques could improve to use larger amount of data. 16h10 – 16h30 Development of a multiple component analysis approach for the characterization of matrices of primitive chondrites Pierre-Marie Zanetta - UMET

Chondrites are made of two main components : chondrules, which are coarse-grained solidified droplets of magmatic material, and a matrix composed of very fine-grained minerals (sub- micrometer to micrometer). The matrix is a complex assemblage of different phases showing heterogeneous compositions, grain size distribution and densities. Matrix bulk composition is therefore difficult to analyze by conventional techniques such as defocused beam electron microprobe microanalysis. Providing an improved estimate of the bulk chemistry of the matrix, in association with mineralogy, would enable a direct comparison of matrices from different groups of chondrites and could provide constraints on their processes of formation and later alteration in their parent body. We propose a new method for sample analysis adapted from techniques of multiple component analysis. We first acquire chemical maps by EDS (energy dispersive spectroscopy) on a FESEM (Field Emission Scanning Electron Microscope) at low accelerating voltage (5 kV). This allows an analytical spatial resolution of ≈ 250 nm. From these chemical maps, compositions fields are plotted as a function of the main elements (Mg, Si, Fe or S). Clusters distribution allow us to infer grain sizes, modal abundances, densities and chemistry of each phase, along with associated uncertainties. The endmembers of the compositions fields correspond to the larger minerals, whose composition are measured separately by electron microprobe in order to calibrate our EDS-SEM data. The bulk chemistry is obtained by the combination of modal abundances, compositions and density of different phases. We were thus able to determine the bulk chemistry of the matrix of Orgueil (the reference chondrite for the solar composition) and our results are in agreement with Lodders and Fegley (1998) who have analyzed Orgueil using wet chemistry. Further studies are in progress on other primitive chondrites.

16h30 – 16h50 Hot gas in the largest structures of the Universe Victor Bonjean - IAS

Numerous studies have focused on galaxy-cluster pairs using X-ray to characterize and study the hot ionized intra-cluster gas together with the gas in between clusters. The objective of such studies is to disentangle between cases of interacting clusters and cases of cosmic filamentary gas. An additional observational probe of hot ionized gas is the Sunyaev-Zeldovich (SZ) effect. It allows us to detect a more diffuse gas and thus study with greater details the outer parts of galaxy clusters and in filaments in between clusters. We have performed an analysis of cluster pairs selected from the Planck SZ cluster catalogue. We have focused on two pairs with significant excess of SZ signal in between the clusters, S/N>2, in the Planck MILCA SZ map. We have modeled the intra-cluster gas with a general Navarro Frenk & White model and the filament in between clusters with a beta- model. We performed the analysis of the SZ maps using an MCMC approach and determined the physical parameters of each component. With SZ only data, we obtained for the pair A399-A401 GNFW parameters for clusters and a pressure for the bridge in agreement with results from Planck Collaboration VIII, 2013. In our analysis, we also present the first study of the pair A21-PSZ2 G114.90-34.35 detected in Planck. We show that it is possible to characterize the gas in galaxy clusters and in less dense parts around them using only the Sunyaev-Zeldovich effect.

17h – 18h Conférence : la science dans les films Roland Lehoucq - CEA

Mercredi 23 Novembre

9h30 – 10h10 Revue L'étude de l'atmosphère des géantes gazeuses par l'exploration spatiale et la modélisation Aymeric Spiga - LMD

A l'heure où la mission Cassini entre dans sa phase "Grand Final" dans le système de Saturne, et où la mission Juno vient de commencer ses mesures scientifiques en orbite autour de Jupiter, les besoins en modélisation des atmosphères des géantes gazeuses sont plus que jamais d'actualité. Je détaillerai les défis qui se posent dans cet axe de recherche et les méthodes qui permettent de les relever. Des résultats de modélisation climatique globale pour Saturne seront décrits, des perspectives pour l'étude de Jupiter seront dressées et ces travaux seront mis en perspective avec les observations de Cassini, Juno et des télescopes.

10h10 – 10h30 De l’espace au labo : comment fabriquer une comète à partir des observations VIRTIS/Rosetta de 67P/Churyumov-Gerasimenko Batiste Rousseau - LESIA

La sonde Rosetta vient tout juste de terminer sa mission autour de la comète 67P/Churyumov- Gerasimenko mais le travail continu ! Bien que les données nous apportent des connaissances approfondies sur ces reliques du système solaire la comète renferme encore quelques secrets. Notamment la composition exacte de la surface du noyau, faute d’analyse de prélèvements et de retour d’échantillon. Cependant, grâce aux indices donnés par différents instruments de Rosetta, et notamment ceux de VIRTIS le spectro-imageur sur lequel mon travail est basé, il est possible d’essayer de retrouver cette composition. En utilisant des matériaux analogues à ce que l’on pourrait trouver sur une comète, je réalise des mélanges de poudres très fines (≤ µm) et j’en mesure la réflectance dans la même gamme spectrale que VIRTIS. Il devient alors possible de retrouver les caractéristiques spectrales de 67P et donc potentiellement sa composition !

10h30 – 10h50 The gas in and around high redshift galaxies Siwei Zou, Patrick Petitjean, Pasquier Noterdaeme – IAP

We study a complete sample of neutral atomic carbon quasar absorption systems, observed with the Very Large Telescope. Such absorbers probe highly shielded gas in which molecules are expect to form. We will get information on the depletion of the dust, metallicity, molecular content and star formation in the ISM of high redshift. Galaxies. 10h50 – 11h10 Wiener Filter Reloaded : Fast Signal Reconstruction without Preconditioning Doogesh Kodi Ramanah - IAP

The Wiener filter has emerged as a standard tool for the inference of high dimensional signals, such as the quintessential large scale structure and CMB problems. We present a new robust and fast iterative solver, based on the recently developed messenger technique, to efficiently calculate the Wiener filter solution of large and complex data sets. Like its predecessor, this new dual-messenger algorithm does not require the use of preconditioners and can account for inhomogeneous noise distributions and arbitrary noise geometries. We demonstrate the capabilities of this scheme in signal reconstruction by applying it on a simulated cosmic microwave background (CMB) data set to investigate the effectiveness of reconstruction and convergence properties. The dual-messenger algorithm outperforms the standard messenger and the popular preconditioned conjugate gradient (PCG) schemes in terms of execution time, being roughly a factor of 5 and 3 times faster than the respective methods.

11h30 – 11h50 Mesurer la rotation du cœur des géantes rouges grâce à l’astérosismologie Charlotte Gehan - LESIA

L’astérosismologie fonctionne sur le même principe que la sismologie terrestre : les ondes sismiques qui se propagent au sein des étoiles provoquent des oscillations stellaires, et leur détection permet d’étudier l’intérieur des étoiles. Les géantes rouges sont des étoiles en fin de vie qui sont des cibles de choix pour l’astérosismologie. En effet les conditions dans leur intérieur sont réunies pour qu’un couplage ait lieu entre les ondes de gravité du cœur et les ondes de pression de l’enveloppe externe, donnant naissance à des modes mixtes. Contrairement aux étoiles de la séquence principale comme le Soleil, l’existence de modes mixtes permet d’étudier le cœur des géantes rouges, notamment la rotation de leur cœur. La rotation est connue pour avoir un impact important sur l’évolution des étoiles, mais il reste difficile d’inclure la rotation dans les modèles d’évolution stellaire : ces derniers prédisent des vitesses de rotation du cœur des géantes rouges au moins dix fois supérieures aux mesures obtenues par l’astérosismologie. Ces résultats impliquent qu’un transport de moment cinétique très efficace est à l’œuvre dans les intérieurs stellaires, dont les mécanismes physiques ne sont pas encore entièrement compris. Il est ainsi capital de connaître la façon dont la rotation interne des géantes rouges évolue au cours du temps, afin de mieux caractériser les processus physiques qui opèrent dans les intérieurs stellaires profonds. Dans ce contexte, j’ai validé une méthode permettant d’obtenir des mesures automatiques de la rotation du cœur des géantes rouges présentant différents stades évolutifs à partir des données du satellite Kepler. De telles mesures automatiques préparent également le terrain pour l’analyse des centaines de milliers de spectres d’oscillations que le satellite PLATO devrait fournir d’ici quelques années.

11h50 – 12h10 Etude de molécules organiques avec le Cosmorbitrap dans un contexte de future mission spatiale Laura Selliez, Christelle Briois, Nathalie Carrasco - LPC2E

Les instruments de spectrométrie de masse embarqués à bord des missions spatiales ont permis de mettre en évidence la présence de molécules d’intérêt dans de nombreux environnements planétaires et interplanétaires. La mission Cassini-Huygens, par exemple, a permis la détection d’ions positifs et négatifs à des masses très élevées. Cependant, leur étude est limitée par la résolution des instruments embarqués. En effet, en raison du temps inhérent à la programmatique et des contraintes liées aux missions spatiales, les instruments spatiaux ont des performances bien plus limitées que les instruments de laboratoire. Développer les performances des instruments analytiques pour les futures missions en préparation est un des enjeux des diverses équipes engagées dans ces missions afin de compléter et d’augmenter l’acquisition de données commencée par les missions et études précédentes. Parmi les nouveaux analyseurs en masse utilisés en laboratoire, offrant une ultra haute résolution en masse et permettant la discrimination d’interférences entre diverses molécules, il en est un basé sur la technologie OrbitrapTM. Intégré à un instrument complet de spectrométrie de masse, il deviendrait un instrument de choix pour l’exploration de Titan mais également de multiples objets du Système Solaire. Un consortium de laboratoire français (soutenu par le CNES) développe, depuis 2009, un analyseur en masse spatial avec cette technologie : le Cosmorbitrap. Cette présentation vise à présenter les résultats obtenus sur des molécules organiques (dans un contexte Titan) avec le prototype de laboratoire intégrant le développement Cosmorbitrap.

12h10 – 12h30 L’étonnante magnétosphère d’Uranus, résultats de simulations numériques en 3D Léa Griton & Filippo Pantellini - LESIA

Les magnétosphères du système solaire sont encore relativement peu comprises. Celle de la Terre constitue une référence, à partir de laquelle les grandeurs caractéristiques des magnétosphères sont définies. Jupiter et Saturne, dont le champ magnétique tourne avec la planète comme une toupie, sont également décrits par des cycles définis en fonction de la rotation de la planète et de la vitesse du vent solaire. Le cas d’Uranus, cependant, reste mystérieux car peu de données sont disponibles, et la seule simulation numérique actuellement publiée (Toth et al., 2004) inclut un vent solaire sans champ magnétique, ce qui prive le modèle d’un phénomène important dans la structure d’une magnétosphère : la reconnexion avec le champ magnétique interplanétaire (transporté par le vent solaire). Or la rotation rapide de la planète, dont l’axe du champ magnétique est écarté de l’axe de rotation d’un angle d’environ 70°, façonne une magnétosphère très différente de celles modélisées pour Jupiter ou Saturne. Nous présentons ici des résultats inédits de simulations numériques MHD (magnétohydrodynamique) de la magnétosphère d’Uranus ainsi qu’une première interprétation de ces résultats. En bonus, je vous donnerai des nouvelles de la mission BepiColombo, qui partira explorer la magnétosphère de Mercure. La magnétosphère de Mercure, par sa très petite taille et sa proximité au Soleil, constitue elle aussi un cas particulier de l’interaction du vent solaire avec un corps magnétisé.

12h30 – 12h50 Improved representation of gravity waves in the Mars Climate Database and perspective on the study of their distribution and propagation Margaux Vals, F. Forget, E. Millour, A. Spiga, L. Montabone - LMD

The Mars Climate Database (MCD), developped by the Laboratoire de Météorologie Dynamique (LMD, Paris), provides a complete set of atmospheric statistics computed from the LMD’s martian GCM. Data of various fields (temperature, winds, pressure) together with atmospheric composition are stored from the surface up to a 300 km altitude over 12 months and 12 local times of day. Although fundamental information on diurnal and annual cycles are kept by the software, there is a need to simulate the intra-month or day-to-day variations, which are averaged out, and then provide a set of realistic range of variability for the fields the user wants to reproduce. The so-called large scale perturbations, added as input argument in the MCD, aim at simulating this variability based on a storage through Empirical Orthogonal Functions over the different simulated years. Another particular source of atmosphere variability are the gravity waves. The current MCD simulates this phenomenon, the so-called small-scale perturbations, by modelling a vertical wave propagation. However, longitudinal propagation of the gravity waves was also revealed by instruments Mars Global Surveyor (MGS), then Mars Odyssey (ODY) and Mars Reconnaissance Orbiter (MRO) during aerobraking operations. Especially density variations were measured by the respective accelerometers and have provided observable longitudinal small-scale gravity wave spectra. More recently, the Mars Atmosphere and Volatile Evolution Mission (MAVEN) has also provided accurate measurements of the perturbed density leading to further observations of the gravity waves. Relying on these observations, the MCD has been improved to take the longitudinal variations of the gravity waves into account. Some ongoing work, which aims at further exploring GW mechanisms and improving their modeling, based on all data gathered from the different instruments, so from wide ranges of latitudes, longitudes and seasons, will also be introduced.

14h – 14h40 Revue

14h40 – 15h The birth of a supermassive black hole binary Hugo Pfister, Capelo, Lupi, Volonteri - IAP

Supermassive black holes (SMBHs), which can be found in the center of most of the most massive galaxies today, are thought to play a crucial role in galaxy evolution. However their growth and dynamics is still poorly understood. In this presentation we focus on how, in galaxy mergers, SMBHs reach small separation to form a bound binary. The main difficulty in tackling this issue is the range of scales involved : from sub-pc scales for BHs to hundreds of kpc scales for galaxies. We zoom on an already very high resolution (10 pc) simulation of major mergers and reach pc resolution, allowing us to understand what drives the dynamics of BHs from kpc to pc scales.

15h – 15h20 PicSat : un nanosatellite pour l’observation du transit de beta Pic b Mathias Nowak - LESIA

Beta Pictoris, son disque circumstellaire, ses exocomètes, et sa géante gazeuse beta Pic b : sans doute l’un des systèmes les plus célèbres de toute l’astronomie, et déjà observé par les plus grands noms du domaine (Hubble, Keck, Gemini, le VLT, etc.). Alors que peut-il se passer lorsque l’on sait que la géante gazeuse du système (et/ou sa sphère de Hill) transite devant l’étoile, et que l’on connait même la date de l’évènement ? Le début d’une aventure, sans aucun doute. Sauf que l’évènement en question a lieu dans moins d’un an, et qu’il ne sera pas visible depuis le sol. Alors oubliez les colosses de 8 m : l’aventure en question s’appelle PicSat, et elle tient dans une boite a chaussure (spatiale, tout de même). Actuellement en développement au LESIA, PicSat est un nanosatellite dont l’objectif principal est l’observation constante de beta Pictoris afin de détecter le transit de la géante gazeuse, prévu pour septembre 2017. Le satellite doit être lancé au deuxième trimestre 2017, sur une orbite a 600 km d’altitude. Je présenterai les grandes lignes de la mission, et notamment ses objectifs scientifiques. Je m’attacherai aussi a présenter la charge utile opto- mecanique embarquée, spécialement conçue pour la photométrie de précision (oui, il y aura sûrement quelques sordides détails d’ingénierie spatiale, voire peut-être même d’électronique embarquée...). Je finirai par quelques mots sur le satut actuel de la mission, et sur son avenir à relativement court terme. ... D’ailleurs, quelqu’un aurait-il une fusée ?

15h20 – 15h40 Space and ground based tests of Lorentz invariance within the SME framework Hélène Pihan-Le Bars, C. Guerlin , P. Wolf - SYRTE

The Lorentz invariance principle is a cornerstone of the two major theories describing the modern physics : General Relativity and Standard Model. Despite their respective success, they fail to give a unified description of all the known physical interactions. To address this issue several alternative theories of unification have been developed over the last decades. Some of them, such as Loop Quantum Gravity, predict that Lorentz invariance could be violated at high energy scale. Although such energies far exceed our technological capacities, residual signatures of this Lorentz violation are expected to appear at low energy scale.\par In the purpose of testing the limits of actual theories on one hand and the predictions of alternative theories on the other hand, a large range of experimental set-ups have been used to search for these weak signatures on Earth. The low energy scale at which the effects are expected require experiments with high precision and long term stability, such as atomic clocks.\par I will present a recent analysis performed on the F01 Cs-Rb fountain data (hosted at SYRTE), which can be used to test Lorentz invariance by monitoring the frequency of hyperfine Zeeman transitions over months and looking for time varying deviation from the expected frequency. We used an improved SME model for hyperfine Zeeman transitions together with an advanced model for the 133Cs nuclei developed by the IPN theory team (Univ. Paris Saclay), to improve the present limits on several SME coefficients by up to 13 orders of magnitude, which challenges suppressions generally expected e.g. from quantum gravity phenomenology.

16h10 – 16h30 A search for the molecular counterpart of high velocity ionized outflows in nearby BAL QSOs Anelise Audibert ; Combes, F. ; .Dasyra, K. ; Salomé, P. - LERMA

Feeding and feedback in Active Galactic Nuclei (AGN) play a very important role to gain a proper understanding of galaxy formation and evolution. The nature of the interaction between the activity mechanisms in the nucleus and its influence in the host galaxy are related to the physical processes involved in feedback, including star formation, energetic and chemical recycling in the interstellar (ISM) and the feeding process, which account for the gas fuelling of the black hole (BH). The discovery of many massive molecular outflows in the last few years have been promoting the idea that winds may be major actors in galaxy evolution. Also, the widely observed winds from the central regions of AGN are promising candidates to explain the link of scaling relations under the AGN feedback scenario. Observationally, with terminal velocities of order 1000-30000 km/s, the ionized gas outflows in Broad Absorption Line (BAL) quasars could constitute a source of high ram pressure that could accelerate molecular gas to high velocities, as long as the molecular clouds have the time to (re)form in the flow. Our aim is to test if these QSOs could be hosting outflows that are most efficient in expelling molecular gas outside of galaxies, since massive outflows driven by stars and AGN are a key element in many current models of galaxy evolution. A detailed analysis of nearby BAL QSOs will serve as a prototype for subsequent studies of high-momentum outflows in high-z QSOs at the peak of the star formation history of the Universe.

16h30 – 16h50 Remote sensing of the Venus night atmosphere by SPICAV onboard the Venus Express orbiter Daria Evdokimova, Montmessin F., Belyaev D., Fedorova A. - LATMOS

Venus has a dense CO2 atmosphere with an optically thick cloud layer consisting of concentrated H2SO4 droplets. In addition to CO2 several trace gases such as H2O, SO2, O3, HCl, etc. affect the chemistry of the entire atmosphere. The research is based on the data obtained from the SPICAV experiment onboard the Venus Express orbiter in 2006-2014. SPICAV had a UV and a NIR spectral channels. Stellar occultations performed by SPICAV UV allow the study of the vertical structure of the nighttime mesosphere (60-120 km). Nadir observations by SPICAV NIR investigate Venus thermal emission in spectral transparency windows on the night side. Sulfur dioxide is a product of volcanic activity and its oxidation leads to formation of H2SO4 clouds at 50-70 km. Ozone layer was discovered by SPICAV in 2006-2010 at altitude about 100 km in nighttime atmosphere. It is produced by reactions with oxygen and chlorine atoms near the anti-solar point of the Sub-Solar to Anti-Solar circulation. OH- and Cl- radicals involved in this circulation are responsible to SO2 dissipation on the Venus night side. SO2 content varies a lot, as revealed by long-term day-side monitoring. O3 behavior shows episodic bursts of mixing ratio with a few tens ppb. Analyzing the temporal and spatial fluctuations of these gases in the night-time mesosphere may be a key for understanding the global regime of SSAS circulation on Venus. The other topic of this work deals with the cloud layer, which is the major reason for the great greenhouse effect on the present climate of Venus. Variations of Venus clouds do influence the processes of radiative transfer leading to changes in dynamics and composition of the entire atmosphere. Remote measurement of the Venus thermal emission in the 1.28-transparency window can be used to study changes of clouds structure. Further comparison of these changes with SO2 behavior will clarify our understanding of the chemistry leading to formation of H2SO4 droplets as well as processes of circulation in the lower mesosphere.

17h – 18h Conférence :

L’épopée de Rosetta et de Philae Lucie Maquet – IMCCE

Lancée en 2004, la sonde européenne Rosetta accompagnée de son atterrisseur Philae ont vécu une véritable épopée jusqu’à septembre dernier. D’abord prévus pour analyser la comète 46P/Wirtanen, ils ont été réorientés vers la surprenante 67P/Churyumov-Gerasimenko. Au cours de son périple dans le Système solaire pour rejoindre sa cible principale, la sonde survola deux astéroïdes Steins et Lutetia. La sonde fut ensuite placée en sommeil durant 31 mois pour être finalement réveillée en janvier 2014 pour la phase d’approche de la comète. Au cours de cette conférence, nous reviendrons sur ce périple et sur les découvertes qui en découlent.

Jeudi 24 Novembre

9h30 – 10h10 Revue HESS - Un réseau de télescope gamma dédié à l'etude de l'Univers Thermique de Très Haute Energie. Mathieu de Naurois – CNRS - IN2P3 - Ecole Polytechnique

Le réseau de télescopes à effet Cherenkov H.E.S.S., installé sur les hauts plateaux du Khomas, en Namibie, observe depuis 2012 les phénomènes violents de l'Univers à très haute énergie. Équipé de caméra ultra-rapide, il détecte la lumière Cherenkov ténue produite dans l'atmosphère lors qu'un rayon cosmique, interagissant avec cette dernière, produit une cascade de particules. Le réseau a ouvert une nouvelle fenêtre sur l'Univers à très haute énergie, en rayons gamma d'énergie comprise entre ~ 20 GeV (gigaelectronvolt) et la centaine de TeV (téralectronvolt), plus de douze ordre de grandeur en énergie au dessus de la lumière visible. L'Univers ainsi dévoilé est constitué de dizaines d'accélérateurs cosmiques de type variés, tels que les reste de supernova, les nébuleuses à vent de pulsars, les interactions de vents stellaires dans des système binaires, le trou noir central de la Voie Lactée, mais aussi les noyaux actifs de galaxie et certaines galaxies à flambée d'étoile. Un panorama de cette nouvelle astronomie sera présenté.

10h10 – 10h30 AGN-driven winds are hotter than you might have expected Tilman Hartwig - IAP

Black holes (BHs) of billions of solar masses power very luminous quasars, which are observable out to z > 6. The quasar feedback can prevent further gas accretion by clearing out the galaxy of gas and directly influences galaxy formation. Consequently, feeding and feedback must eventually be studied together. Simple models of these AGN-driven outflows succeed in reproducing various observed correlations between the BH and its host galaxy’s properties. However, these analytical models are 1-dimensional and do not account for direction-dependent effects such as the lower density and optical depth perpendicular to the galactic disk I will present a new 2-dimensional analytical model of AGN-driven outflows that takes into account the direction-dependant column densities of the gas. This 2D model is of special interest in the era of ALMA, which enables a comparison of my model predictions to velocity maps of high redshift galaxies based on their rest- frame far-infrared continuum, [CII], and CO emission. For a gas-rich galaxy with a proto-disk, we expect to see strong outflows of gas perpendicular to the disk plane and from the outflow rate and opening angle we can derive further properties such as accretion efficiency and duty cycle based on my model.

10h30 – 10h50 IR Micro-tomographie of paris meteorite Zélia Dionnet, A. Aleon-Toppani , F. Borondics, R. Brunetto, Z. Djouadi, D. Troadec - IAS

Primitive extraterrestrial materials (meteorites, IDPs) are characterized by a large mineralogical and compositional heterogeneity which witnesses the complexity of the pre-accretional and post- accretional. This heterogeneity has been observed by different techniques such as micro infrared (IR) spectroscopy mapping but with a limited resolution (> 5 μm). IR spectroscopy is a powerful tool as it is (a) totally non-destructive ; (b) able to characterize the molecular vibrations, and in particular to access both to the mineral and carbonaceous phases and (c) comparable to astronomical observations of primitive Solar System small bodies (asteroids, comets, TNOs) and ISM dust. With the development of a new detector (Focal Plan Array (FPA)), IR mapping with high spatial resolution and IR tomography is now possible. Here, we report the results of high-resolution Fourier Transform IR spectral imaging experiments at micron scale using FPA and synchrotron radiation of the Paris meteorite (carbonaceous chondrite, class CM ). We measure the spatial distribution of chemical/mineralogical components (organic materials, anhydrous silicates, hydrated silicates, carbonates) of the Paris meteorite and the correlation between the organic and silicate phases down to a scale of 3 μm. Mapping using FPA detectors is powerful as it allows a high spatial resolution in a very limited acquisition time (less than 20 min for a grain of 50x40μm).

10h50 – 11h10 Gamma-Ray Bursts as a tool for cosmology : population models. Jesse Palmerio - IAP

Gamma-Ray Bursts (GRBs) are short, intense bursts of electromagnetic radiation in the hard X-rays and soft gamma-rays originating from space. They are associated with ultra-relativistic jets produced by a newborn accreting stellar mass black hole. There are two classes of GRBs : long GRBs (if their duration is longer than 2 seconds) which have observational evidence tying them to the gravitational collapse of some massive stars, and short GRBs (if their duration is shorter than 2 seconds) which are believed to be associated with the coalescence of compact objects. Because of their detectability up to very high redshift (z > 9) and their transient nature, GRBs and their associated phenomena offer a unique tool to probe the distant universe. However, there are still today uncertainties about the underlying short and long GRB populations. In this talk I will first give a quick overview of the current paradigm for GRBs, then I will present some preliminary results of my work on a Monte Carlo population code which aims to measure the parameters of the luminosity function, the redshift distribution and the spectral model of the different classes of GRBs and ultimately to constrain the underlying progenitors.

11h30 – 11h50 Détection d’émissions décamétrique joviennes controllées par Europe et Ganymede Corentin Louis, L. Lamy, P. Zarka, B. Cecconi, S. Hess - LESIA

Les émissions radio aurorales Joviennes produites par la magnétosphère de Jupiter s’étendent de quelques kHz à 40 MHz. Une partie des émissions décamétriques (typiquement de 1 à 35 MHz) est contrôlée par la lune Io (Io-DAM), et je me suis intéressé à la recherche d’émissions décamétriques contrôlées par les autres lunes Galiléennes. J’ai utilisé le code SERPE (Simulateur d’Émissions Radio Planétaires et Exoplanétaire) pour simuler les spectres dynamiques (cartes temps-fréquence) attendus pour les émissions radio de Jupiter contrôlées par chacune des quatre lunes Galiléennes. J’ai ensuite comparé ces simulations aux observations acquises par Voyager (PRA) et Cassini (RPWS) lors de leur survol de Jupiter (en 1979 et entre 2000 et 2003, respectivement). J’ai pu identifier de nombreuses structures en forme d’arcs similaires aux habituels arcs Io-DAM, mais seulement compatibles avec les simulations Europe ou Ganymede. L’analyse statistique de ces détections (130 pour Europe et 96 pour Ganymede) m’a permis de décrire les propriétés moyennes des émissions Europe-DAM et Ganymede-DAM (spectre, variabilité temporelle, occurence dans un diagramme Phase VS CML (Central Meridian Longitude)).

11h50 – 12h10 Numérisation rapide d’un système synchronisé d’antennes radio multi-réparties tel que le Radiohéliographe de Nançay Ait Mansour El Houssain, Karl-Ludwig Klein, Bruno Da Silva, Stéphane Bosse - LESIA

Le Radiohéliographe de Nançay est le seul instrument dédié à l’imagerie du Soleil en ondes décimétriques-métriques. Il fonctionne sur le principe de l’interférométrie, en utilisant 47 antennes essentiellement réparties sur des axes est-ouest (3,2 km) et nord-sud (2,5 km). Cette étude a pour but d’explorer un nouveau concept technique propre à la radioastronomie du futur, appliqué à l’interférométrie solaire. Elle porte sur la numérisation rapide d’un système synchronisé en sortie d’antennes. Ces aspects numérisation rapide et synchronisation sont d’une importance capitale pour les prochains radiotélescopes du futur. Ils permettent de simplifier les chaînes de réception radiofréquences et d’en diminuer la consommation électrique ainsi que les coûts d’entretien et de maintenance. L’application à l’observation du Soleil comporte cependant des contraintes originales, comme la grande dynamique des signaux, qui ne sont pas prises en compte dans les études en cours pour les radiotélescopes futurs. Le radiohéliographe actuel a une chaîne de réception analogique avec une numérisation centralisée. La commutation entre les différentes fréquences dans la bande 150-450 MHz est réalisée d’une façon analogique et temporelle. Ceci nécessite beaucoup de calibrations analogiques et oblige de figer la gamme des fréquences (9 fréquences de largeur 1 MHz). De plus, en interférométrie métrique, les très grandes longueurs de câbles coaxiaux onéreux dans lesquels le signal est transporté des antennes au récepteur sont toujours sources d’erreurs et de fluctuations importantes des chaines de réception radiofréquence. Apporter une numérisation complète de la bande (300 MHz) permet d’avoir de la souplesse dans le traitement et l’analyse des données (résolution fréquentielle et la possibilité d’observer plusieurs bande simultanément). Ceci engendre la nécessité d’avoir une très grande précision des horloges (0.7 ps d’erreur de phase) pour cadencer des ADC (Analog-to-Digital-Converter) large bande (1 GHz d’horloge). L’objectif principal de la thèse est donc de synchroniser le réseau d’antennes multi-réparties. Le saut technologique ainsi induit est un enjeu grandissant dans des grands projets européens et internationaux.

12h10 – 12h30 Où en sont les nuages modélisés de Vénus ? Sabrina Guilbon, Anni Määttänen, Jérémie Burgalat, Aurélien Stolzenbach, Franck Montmessin, Slimane Bekki - LATMOS

Vénus est une planète terrestre entièrement recouverte de nuages. Ces derniers sont composés d’acide sulfurique et d’eau. Malgré les diverses missions spatiales qui on été envoyées pour étudier Vénus, ses nuages et leur formation constituent un mystère. C’est pourquoi nous nous tournons vers la modélisation afin d’y voir un peu plus clair. Mon travail consiste donc à développer un module de microphysique pour compléter le modèle de climat global mis en place par le Laboratoire de Météorologie Dynamique et le LATMOS. Cette présentation portera sur l’avancement de ce travail.

12h30 – 12h50 Asteroseismic modelling and orbital analysis of the triple star system HD 188753 Frédéric Marcadon, T. Appourchaux and J. P. Marques - IAS

HD 188753 (HIP 98001, HO 581 or KIC 6469154) is known as a close visual binary discovered by Hough in 1895 and characterized by an orbital period of 25.7 years. In the late 1970s, it was established that the secondary is itself a spectroscopic binary with a period of 155 days. HD 188753 is therefore a hierarchical triple star system consisting of a close pair (Ba and Bb) in orbit at a distance of 12.3 AU from the primary (A). The triple star system was observed by Kepler in short- cadence mode during quarters Q13 and Q14. We report in this study the detection of solar-like oscillations for the brightest star HD 188753A. We perform the first asteroseismic analysis of HD 188753A using state-of-the-art stellar models in order to derive its fundamental parameters. We obtain the age and initial chemical composition of the star, which are assumed to be the same for the three members of the system, as well as a precise but model-dependent estimate of its mass. We then combine micrometric, interferometric and radial velocity measurements from almost a century of observations to determine the orbital masses of the three stars. We get direct constraint on the mass of HD 188753A which allows us to test different input physics in our stellar models. The full characterization of the triple stars HD 188753 is essential for better understanding the formation mechanisms and evolutionary processes of binaries and multiple stellar systems in our Galaxy.

14h – 14h40 Revue

Adaptive Optics for retinal imaging

Serge Meimon - ONERA The eye is the only optical window to a neuro-vascular network in our body, located in the retina. Probing this retinal network at the scale of optical wavelengths (typically a micron) provides insight not only on the major eye diseases (Age-related Macular Degeneration, Glaucoma, Diabetic retinopathy), but also on the state of the brain neuro-vascular network and on the related pathologies (Alzheimer, Parkinson, Traumatic brain injuries). These developments have been triggered by the adaptation of adaptive optics to ophthalmology since 1997. Three main retinal imaging modalities have been equipped with AO : Flood- illumination Ophtalmoscopes, Scanning Laser ophtalmoscopes and Opical Coherence Tomography. Several commercial AO retinal imaging systems are now on the market. These instruments have been able to document the structure of the retina with unprecedented resolution. However, the medical benefit of such observations often emerges when structure is related to function, such as color vision or edge detection. The new era of AO instruments will have to provide in real time functional imaging of the structures of the retina.

14h40 – 15h H2 emission from magnetised non-stationary bow-shock LE Ngoc Tram - LERMA

When a fast moving star meets a diffuse interstellar cloud, the surrounding gas gets heated and illuminated. As a result, a bow-shock is born which delineates the wake of the star. In the process, new molecules are generated and excited and they become accessible to observations. When the star emits a wind, the wind material itself is shocked. Here, we revisit models of H2 emission in these bow-shocks. We approximate the bow-shock by a statistical distribution of planar shocks computed with a state-of-the-art magnetised shock model (the Paris-Durham shock code). We improve on previous studies by considering the effect of the age of non-steady C-shocks on the H2 excitation diagram and H2 emission line shapes. We examine how the line shapes depend on the shock velocity and the viewing angle. We demonstrate the observational biases which can occur when the number of H2 lines observed is too small. Finally, we present recent developments in the shock model which allow it to describe stellar winds. This enable a detailed description of the chemistry and the cooling and heating processes which take place in stellar winds.

15h – 15h20 XUV Disk Galaxies Isadora Bicalho, Combes, F ; Rubio, M. ; Verdugo, C. Salome, P. - LERMA

The spatially resolved star formation law has been studied in great detail in galaxies in recent years and it has been established at high surface density, when most of the gas is molecular, that the Kenniicutty-Schmidt law is almost linear providing a constant gas consumption time-scale of about 3Gyr (e.g Bigiel et al. 2011, Saintonge et al 2011). However the star formation efficiency (SFE) 2 falls very quickly as soon the surface density drops below 10 MSOL pc , and the gas is mainly atomic. The star formation rate (SFR) law is then highly non-linear, and the gas consumption time- scale several Gyrs up to Hubble time. This is just the case for several dwarfs galaxies and the most external parts of disk galaxies (Bigiel et al 2010), where the environments make star formation more difficult due to the low gas density, low temperature and low metallicity conditions, resembling an earlier stage of the universe. Recent star formation within such environments was detect in $H_*\alpha*$ (the principal star formation trace over the years). However,the Galaxy Evolution Explorer (GALEX) data demonstrate that Hα observations still fail to detect a significant population of moderate-age stars in the outermost disks of spiral galaxies, since Hα traces more recent star formation episodes. Our aim is to detect the molecular gas expected in the outskirt of spiral galaxies. One remarkable example is M83, a nearby galaxy with an extend XUV disk reaching 2 times the optical major radius (Gil da Paz et al. 2007). However, our progress in understanding these XUV disks has been halted by the difficulty of detecting molecular gas via CO emission. In particular, no highly significant (> 5σ) CO was detect in ALMA maps of the XUV disk of M83 when we expected to detect 20-30 molecular clouds with SNR> 17. We hypothesize that the molecular clouds in the ALMA data are CO-dark, caused by the strong UV radiation field, which dissociates CO preferentially, due to small size of the star forming clumps in the outer regions of galaxies.

15h20 – 15h40 Investigating the present and past glacial and frost activity on Pluto with a volatile transport model Tanguy Bertrand, F. Forget - LMD

The high obliquity and eccentricity of the orbit of Pluto induce seasonal cycles of condensation and sublimation of the main volatile ices : N2, CH4, and CO. The New Horizons spacecraft, which flew by Pluto in July 2015, revealed a complex surface composition including a thousand-kilometre nitrogen glacier in the « Sputnik Planum » plain near the Anti-Charon longitude, extensive methane frosts at mid and high latitudes, and equatorial ice-free regions. We present numerical simulations designed to model the evolution of Pluto’s volatiles over thousands of years on the basis of straightforward universal physical equations. Our results explain the observed distribution of ices on the surface and the quantities of volatiles in the atmosphere. In particular the model predicts the N2 ice accumulation in the deepest low-latitude basin and the 3-fold increase of pressure observed to occur since 1988. This points to atmospheric-topographic processes at the origin of the Sputnik Planum’s nitrogen glacier. The same simulations also show frosts of methane, and sometimes nitrogen, that seasonally cover the mid and high latitudes, explaining the bright northern polar cap reported in the 1990s and the observed ice distribution in 2015. The model also predicts that most of these seasonal frosts should disappear in the next decade, and thus could be tested observationally in the near future. Using prior orbital parameters of Pluto and a realistic glacial flow parametrization, we also simulate past climates of Pluto. The results show that Pluto undergoes cycles of glacial activity (over timescales of few million years) that may explain the rugged eroded- mountain landscapes surrounding Sputnik Planum and the “bladed” methane terrains east of “Tombaugh Regio”.

16h10 – 16h30 Stop hating statistics ! Julien Dassa-Terrier - LERMA

Whether you need to find a break in the linearity of the Period-Luminosity relation of Cepheids or simply want to fit properly a straight line, statistics will be necessary at some point in your research. Unfortunatly, we are often misguided when it comes to our interpretation of statistical parameters. Through the example of the identification of breaking points in the Period-Luminosity relation, we give a concise overview of the loopholes we should avoid at all cost when it comes to statistics.

16h30 – 16h50 E-ELT : Does the size really does matter ? Clément Perrot, Anthony Boccaletti, Pierre Baudoz, Yann Clenet and the MICADO Consortium - LESIA

À l’ère des ELT - Extremely Large Telescopes - (enfin, dans une petite décennie), la conception des instruments qui permettront leur exploitation est un challenge. Dans le contexte de l’imagerie haut- contraste pour la détection et caractérisation de systèmes planétaire, les dimensions et la complexité de ces ELT est d’autant plus contraignante. Dans le cadre de la caméra MICADO, l’instrument proche Infrarouge de première lumière de l’E-ELT, nous verrons comment les contraintes techniques, scientifiques mais également politiques, influencent le design d’une voie dédiée à la coronographie et quelles solutions peuvent être apporté pour obtenir un instrument complémentaire aux systèmes dédiés à l’imagerie d’exoplanètes actuellement en service tel que SPHERE.

17h – 18h Conférence :

Gaia, mille jour après Frédéric Arenou - GEPI

Pierre Angulaire de l'Agence Spatiale Européenne, Gaia, lancé fin 2013, commence à donner ses premiers résultats. Après avoir décrit le fonctionnement de la mission, et ce qu’on en attend comme futurs apports scientifiques, le contenu de la première publication sera décrit, du point de vue de son contenu ainsi que de ses limites connues.

Vendredi 25 Novembre

14h – 14h20 Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko in the context of OSIRIS images Prasanna Deshapriya, M A Barucci et al. - LESIA

This work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument data of Rosetta space mission. Despite the variety of geological features of this region, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of > 40% of normal albedo and suggest that they are associated to H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential subsurface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in August 2015, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 +0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units (Deshapriya et al., 2016).

14h20 – 14h40 Using ALMA to disentangle starbursts and AGN contribution at 1.2mm in massive radio galaxies Theresa Falkendal, Matt Lehnert, Carlos De Breuck, Joël Vernet, Guillaume Drouart - IAP/ESO

High-redshift radio galaxies are unique markers of the most powerful galaxies in the early Universe, showing signature of both powerful AGN and extreme starbursts. To better understand how the starburst in these massive galaxies related to the AGN host it is necessary to spatially re- solve the far-IR emission from heated dust. We have observed a sample of 18 radio galaxies at redshift 1

14h40 – 15h Simulating Titan’s Ionosphere : An Infrared Characterization of the Organic Gas Phase David Dubois, Nathalie Carrasco, Marie Petrucciani, Sarah Tigrine, Ludovic Vettier – LATMOS/JPL

Titan’s gas phase atmospheric chemistry leading to the formation of solid organic aerosols can be simulated in laboratory simulations. Typically, plasma reactors can be used to achieve Titan-like conditions. The discharge induces photodissociation and photoionization processes to the N2-CH4 mixture. It faithfully reproduces the electron energy range of magnetospheric electrons entering Titan’s atmosphere and it can also approximate the solar UV input at Titan’s ionosphere. In this context, it is deemed necessary to apply and exploit such a technique in order to better understand the chemical reactivity occurring in Titan-like conditions. In the present work, we use the Pampre cold dusty plasma experiment with an N2-CH4 gaseous mixture under controlled pressure and gas influx, hence, emphasizing on the gas phase which we know is key to the formation of aerosols on Titan. An internal cryogenic trap has been developed to accumulate the gas products during their production and facilitate their detection. Those are identified and quantified by in situ mass spectrometry and infrared spectroscopy. We present here results from this experiment in an 90-10% N2-CH4 mixing ratio, using a quantitative approach on nitriles and polycyclic aromatic hydrocarbons.

15h – 15h20 Numerical and experimental study of magnetized accretion phenomena in young stars Benjamin Khiar, A.Ciardi, G.Revet , J.Fuchs, S. Pikuz, S. Orlando - LERMA

Newly formed stars accrete mass from the circumstellar disc via magnetized accretion funnels that connect the inner disc regions to the star. The ensuing impact of this free-falling plasma onto the stellar surface generates a strong shock, whose emission is used as a proxy to determine the accretion rates. In general, the existence of a range of mass accretion rates and the presence of strong magnetic fields (> kG) on the stellar surface [1] entail a variety of behaviors for the post- shock plasma, with important repercussions on its dynamics, stability and detection. Observations show that the X- ray luminosity arising from the shock heated plasma at the base of accretion columns is largely below the value expected on the basis of optical/UV observations [2]. As a result, current 2D numerical simulations matching X-ray accretion rates cannot reproduce optical accretion rates [3]. To understand the impact of accretion flows on the stellar surface in the presence of a strong magnetic field we have developed laboratory experiments reproducing crucial aspects of the accretion dynamics in Young Stellar Objects. As a model of accretion columns, we use laser- produced super-Alfvenic magnetically confined jets [4,5] to collide them on solid targets. Here we present results from these experiments and from multi-dimensional MHD simulations. Specific efforts are made to capture the fundamental differences between 2D and 3D simulations, in particular the existence of instabilities, the importance of radiation transport as well as the influence of plasma thermal/dynamic beta. We also present recent results aiming to control the time- variability of the laser-produced jets.

15h20 – 15h40 IGOSat - a 3U CubeSat for measuring the radiative content in Low-Earth Orbit and Ionosphere Hien PHAN - APC

IGOSat (Ionospheric Gamma-ray Observations SATellite) is a student satellite project aimed to develop a 3U nanosatellite for measuring the Total Electronic Content (TEC) and the Gamma- ray radiation at low Earth orbit and in Earth’s ionosphere. The IGOSat areas of interest are the auroral zones and the South Atlantic Anomaly (SAA). The IGOSat project is proposed by the LabEx UnivEarthS, funded by CNES/JANUS program for educational cubesat, in collaboration with the APC and IPGP laboratories from Paris-Diderot University. The project has started in 2012, and will finish in 2019. The satellite is planned to be launched in 2019. There are 2 scientific payloads on the IGOSat satellite platform which are being developed : a dual frequency GPS receiver for the measurement of the TEC, and a Scintillator payload for gamma-rays and electrons detection. These payloads will be hosted in a 3U cubesat platform in a near polar orbit (with the inclination of about 97°) at the altitude of about 650 km. My works are focusing on the Scintillator payload. I am working with simulations (GEANT4) of the interactions between particles and scintillators. We are also setting up a test bench for confirmation of the simulations.

16h – 16h20 L’Astronomie en France à la Belle Epoque : une science ‘populaire' Florian Mathieu - GHDSO

16h20 – 16h40 Modelling the seasonal variations of Titan’s atmosphere to interpret Cassini/Huygens observations Jan Vatant d’Ollone, Sébastien Lebonnois - LMD

The season in the Saturnian system has been moving from northern winter at Cassini’s arrival in 2004 into northern summer in 2016. That way, Cassini brought many information about seasonal evolution within the atmosphere of Saturn’s largest moon, Titan, therefore enlightening phenomenons (composition variations, formations of polar vertices) that remain not fully understood. For this purpose, Global Climate Models (GCM) such as the one developed at LMD/IPSL are very powerful tools. After a short review of the unexplained features of Titan’s atmosphere and the operational principle of a GCM I’ll present the capacities and limits of the IPSL Titan GCM when I started working on it and I’ll show the improvements I’ve brought him through the implementation of a new radiative transfer scheme that now enables a correct modelling of the climate in the stratosphere and mesosphere. Finally I’ll discuss the first so acquired 3D simulations and the future tracks to explore such as the use of different dynamical cores.

16h40 – 17h Comprendre et simuler la polarisation Lucas Grosset - LESIA

Les données de polarimétries sont extrêmement riches en informations mais en contre partie elles sont également assez difficile à appréhender et analyser. Les simulations et notamment via des transferts radiatifs sont des outils très puissant afin de les comprendre. Suite aux données obtenues avec SPHERE sur des galaxies, j’essaye maintenant de reproduire à l’aide de simulations de modèles de structure actuellement acceptés les observations, en particulier de NGC 1068.

17h – 18h Conférence :

La decouverte des ondes gravitationnelles Marie Anne Bizouard - LAL

Un siècle après leur prédiction dans le cadre de la relativité générale, les ondes gravitationnelles ont finalement été découvertes en 2015 dans les données des détecteurs LIGO. Ce qui a été observé sont les ondes gravitationnelles émises lors de la fin de la coalescence de deux trous noirs qui ont fusionné il y a plus d'un milliard d'années. Dans ce séminaire, on expliquera les principaux resultats obtenus et pourquoi on parle de la naissance d'une nouvelle astronomie.