Title: Détection d’exoplanètes froides dans toute la Voie Lactée avec les microlentilles gravitationnelles
Speaker: Etienne Bachelet
Abstract:
Depuis une vingtaine d’années, des dizaines d’exoplanètes « froides » ont été détectées à plusieurs kilo-parsecs de la Terre grâce aux microlentilles gravitationnelles. La grande majorité ont été observées en direction du bulbe galactique, ou la densité d’étoiles est la plus grande. Mais de nouveau grands relevés du ciel, tel que LSST, ouvrent la voie à la détection de microlentilles dans toute la Voie Lactée. En parallèle, la mission de la NASA Roman promet la détection de 1500 planètes à l’horizon 2035. Je présenterai le potentiel et les défis liés à ces nouvelles missions ainsi que les différentes synergies observationnelles.
Title: Unraveling stellar atmospheres and winds with Parker Solar Probe and Solar Orbiter
Speaker: Victor Reville (IRAP)
Abstract:
Speaker : Michel Blanc (astronome émérite à l’IRAP, directeur de l’Observatoire Midi-Pyrénées)
Title: Horizon 2061 perspectives for the future exploration of Giant Planets systems
Abstract : Giant Planet Systems offer four different examples of “small planetary systems” which are accessible both to in situ exploration and telescope observations inside our own planetary system. As described in the recently released report of the « Planetary Exploration, Horizon 2061 » foresight exercise ( https://horizon2061.cnrs.fr/publications/ ), exploration of these systems can address in depth six key science questions about planetary systems: exploring the diversity of their objects and the diversity of their architectures, understanding their formation scenarios and how they work, where to search for habitable worlds, and finally how to detect life. I will discuss how future space missions can address these questions in the decades to come. Finally, I will describe our current and future work on the coupling of giant planets atmospheres with their moons and magnetospheres, its current focus on the Jupiter System with Juno observations, and our plans to extend them to other giant planet systems and possibly to planet/moon/disk interactions.
Speaker : Anthony Boccaletti (LESIA)
Title: Observations of exoplanetary systems at high angular resolution and high contrast: from ground to space
The two-last decade advances in exoplanetary science have been strongly connected to technological breakthroughs, especially in high contrast imaging. The past few years have witnessed a revolution in the field with the implementation of specialized ground-based instruments, like SPHERE at the VLT, equipped with extreme adaptive optics, stellar coronagraphs and dedicated post-processing algorithms. A new revolution is now coming with the James Webb Space Telescope being commissioned, expecting the first science programs to start in a few months.
I’ll briefly summarize the main results obtained with SPHERE in the first years of operations in what concern exoplanets and exoplanetary systems at large. I will focus on two systems which I studied in more details from a disk science point of view, AU Microscopii and AB Aurigae. To push even further the performances of SPHERE we are considering an upgrade of the AO system to explore the very close-in regions around bright stars and to access faint and red targets yet unattainable in star-forming regions, reinforcing the synergy with ALMA. I’ll discuss the main modifications of the instrument and the science cases associated with that upgrade. Finally, I’ll present the coronagraphic system of the Webb’s Mid IR instrument, MIRI, and the expected performance in terms of contrast and the complementarity with SPHERE.
Speaker : Bertrand Lefloch (IPAG)
Title: Astrochimie des régions de formation d’étoile de type solaire – parcours d’un radioastronome
Les grands relevés systématiques de l’emission du gaz moléculaire dans le domaine (sub)millimétrique avec les intruments de l’IRAM et ALMA ont permis de grands progrès dans l’étude de l’ évolution de la matière interstellaire au cours des différentes phases de la formation des étoiles, depuis les condensations prestellaires jusqu’aux protoétoiles évoluées, et ainsi d’aborder la question de l’héritage chimique au cours de cette evolution. Cette question majeure de l’astrochimie a été au coeur des Grands Programmes ASAI et SOLIS que nous avons conduits avec IRAM 30m et NOEMA sur un échantillon de sources représentatives des différentes phases de la formation d’une étoile de type solaire. Malgré une statistique limitée sur le nombre de sources, les résultats obtenus éclairent l’évolution de la complexité moléculaire et la différentiation chimique dans les régions de formation d’étoiles, tout en améliorant notre compréhension des réseaux chimiques. Ces travaux ont également mis en évidence l’importance des phenomènes de perte de masse (jets) qui accompagnent la formation de la protoétoile, ainsi que leur impact sur les conditions physico-chimiques du milieu ambiant. Je terminerai en abordant quelques unes des questions posées après ASAI et SOLIS, sur l’évolution chimique des régions de formation d’étoiles, la différentiation chimique entre sources, l’influence des conditions environnementales. Celles-ci offrent de riches perspectives pour l’astrochimie et pour lesquelles une nouvelle approche dans l’analyse et la modélisation des données observationnelles est nécessaire.
Speaker : Thomas Lizee (Obs de Strasbourg)
Title: From molecular gas to stars: Constraining the properties of resolved gas and dust disks of local spiral galaxies
Milky Way observations have provided insight into the scaling relations of molecular clouds and their ability to form stars. However, these relations cannot be established in nearby galaxies due to the limited spatial resolution of available observations. Starting from the multiphase, multiscale analytical model of Vollmer et al. 2017, whose goal is to describe galaxies as clumpy turbulent accretion disks, we improved the model and applied it to a sample of 17 local spiral galaxies. We generated radial profiles of large-scale quantities (SFR, stars, total gas) as well as molecular line emissions of different species (CO, HCN, HCO+) and compared them to multi-wavelength observations. The model is then able to predict key properties of the ISM such as the Toomre parameter Q, the gas velocity dispersion, the characteristic timescales of molecular clouds (free fall, molecular gas formation and turbulent times) as well as the CO-to-H2 and HCN-to-H2(dense) conversion factors. We conclude our study by reproducing the radial profiles of a Virgo cluster galaxy, NGC 4654, affected by both ram pressure stripping and gravitational interactions to better understand how the ISM properties reacts to such perturbations.
Speaker : Jean-Marc Huré (LAB)
Title: Figures d’équilibres sphéroidales des fluides multicouches.
J’exposerai les principaux éléments d’un formalisme vectoriel résolvant approximativement O(c) les configurations d’équilibre d’un fluide autogravitant hétérogène composé de L couches homogènes en rotation rigide et bordées par des sphéroides parfaits. Cette approche, basée sur un développement du potentiel gravitationnel sur le paramètre confocal c (plutôt que sur l’ellipticité e), permet des configurations très oblates, prolongeant ainsi les travaux classiques fin XIXe de l’école française. Ces solutions analytiques sont validées par les résultats numériques obtenus par la méthode SCF du champ auto-cohérent, et par l’établissement de l’équation du Viriel associée. Quelques perspectives ainsi qu’une application à la détermination de structures internes pour la planète Jupiter réalisant les principales observables seront présentées.
The slides will be in English, the seminar will be given in French.
Speaker : David Cornu (Obs de Paris)
Title: Winning the SKA Science Data Challenge 2 with a fast Deep Learning object detector
Abstract:
With its 1 TB simulated data cube of HI line emission, the SKA Science Data Challenge 2 (SDC2) is getting closer to the difficulty of real upcoming SKA observation analysis. Even if the type of task to perform in the SKA SDCs are rather classical (detection, classification, parameter extraction, etc.) modern datasets have become heavily demanding for classical approaches due to size and dimensionality. It is not a surprise then, that many astronomers started to focus their work on Machine Learning approaches that demonstrated their efficiency in similar applications. However, hyperspectral images from astronomical interferometers are in fact very different from images used to train state-of-the-art pattern recognition algorithms, especially in terms of noise level, contrast, object size, class imbalance, spectral dimensionality, etc. As a direct consequence, these methods do not perform as well as expected when directly applied to astronomical datasets. In this context, the MINERVA (MachINe lEarning for Radioastronomy at obserVatoire de PAris) project has assembled a team to participate in the SDC2 with the objective of developing innovative Machine Learning methods that better suit the needs of astronomical images.
In this presentation, I will describe the work we have made on implementing a modern YOLO (You Only Look Once) CNN object detector inside our custom framework CIANNA (Convolutional Interactive Artificial Neural Networks by/for Astrophysicists) and describe the modifications and tuning that allowed us to reach the first place of the SKA SDC2. I will start by discussing the strengths and weaknesses of this type of method in comparison to more widely adopted Region-Based CNN detectors (Faster R-CNN, Mask R-CNN, …). I will also review the motivation and the effect of the numerous changes we made on the method (data quantization, 3D convolution, layer architecture, detection layout to manage blending, objectness decomposition, IoU selection, additional parameter inference, …) in order to apply it to both SDC1 and SDC2, and identify what are the present limits as well as some tracks for further improvements. I will detail the computational efficiency of the method (with GPU acceleration) and discuss its scaling capabilities for upcoming challenges or datasets. Finally, we will comment on how this methodology could be used to analyze the actual data from SKA pathfinders or any other similar astronomical dataset and how it could be used to merge knowledge and information from multiple datasets at the same time.
Speaker : Martin Turbet
Title: Le modèle « générique » de climats planétaires et panorama de ses applications
Abstract: Le modèle générique de climats planétaires ou « Generic PCM » est un code communautaire, développé principalement et historiquement au LMD, et dont l’objectif est de simuler l’ensemble des processus physiques et chimiques opérant dans les atmosphères planétaires. Ses applications sont nombreuses : étude de la dynamique atmosphérique de Jupiter, Saturne et des géantes glacées, formation de brumes photochimiques sur Titan, évolution couplée de l’atmosphère et des glaces sur Pluton et Triton, paléoclimats de Mars, la Terre et Vénus, climats et observabilité des exoplanètes (des plus froides et petites aux plus grandes et chaudes), etc.
Après un bref aperçu du modèle et des briques qui le constituent, je vous présenterai un panorama de ses applications, avec une attention toute particulière sur les planètes et exoplanètes telluriques.
Speaker : Louis Amard
Title: The evolution of young low-mass stars : focus on rotation and activity
Abstract: Between its formation stage as an active accreting seed and today, the Sun underwent large structural changes as well as variation in magnetic activity, rotation rate and its relation to the surrounding environment. I will go through the different processes that are responsible for these changes and present our latest results on the subject. We will go from the early interaction between the star and its proto-planetary disc bathing in UV radiations emitted from the massive neighbours, to the internal mixing happening in the inner layers of solar-like stars and probed by asteroseismology. Finally, I will try to review the possible applications of this work to other types of stars at different stages of the evolution in the context of the current or future surveys.