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    Laboratoire d’Astrophysique de Marseille

    Seminars

    LAM seminar: Martin Turbet

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    Temperate Rocky Exoplanets: First Results from the JWST and Future Perspectives

    The investigation of atmospheres and surfaces of temperate rocky planets has, until recently, been confined to bodies within our own solar system (e.g., Earth, Mars, Venus). Over the past 2.5 years, however, the James Webb Space Telescope (JWST) has markedly advanced this field by delivering unprecedented data on nearby rocky exoplanets.

    After a review of the first results obtained by JWST on rocky planets through transmission and emission observations, I will focus more specifically on two particularly promising systems: TRAPPIST-1 and LHS 1140b, which currently represent our two best opportunities for studying temperate rocky planets.

    Finally, I will discuss medium- and long-term perspectives to deepen our understanding of their atmospheres and, ultimately, assess their potential habitability.

    Grand public seminar: Antoine Hardy – Décarboner la recherche : pourquoi et comment ?

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    Seminar in French only !

    Depuis les années 2018-2020, des mobilisations scientifiques en lien avec le changement climatique ont lieu dans le milieu de la recherche en France. Ce sont à la fois des réseaux scientifiques à l’échelle locale (Atécopol, Ecopol), des réponses institutionnelles (le rapport du COMETS du CNRS concernant l’éthique environnementale de la recherche en 2022) ou des initiatives au niveau local et national pour quantifier les émissions de gaz à effet de serre des laboratoires et étudier les possibilités de décarboner ce secteur d’activité (l’initiative Labos 1point5 et les nombreux laboratoires engagés dans cette approche). Antoine Hardy vient d’achever quatre ans d’enquête sur ces questions dans le cadre de son doctorat en sociologie des sciences. Il souhaite aborder avec les équipes du LAM trois questions en particulier. D’où vient ce mot d’ordre de la décarbonation de la recherche ? Comment comprendre la décarbonation de la recherche par rapport aux autres politiques publiques environnementales ? Quelles sont les tensions suscitées par ces initiatives et les raisons qui les limitent ? Aborder ces questions permettra d’ouvrir enfin des perspectives sur ce que cela signifierait de faire de la recherche dans un monde réchauffé de + 3 degrés.

    LAM seminar: Yaël Nazé – The mysterious gamma Cas stars

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    Long thought to be a prototype of Be stars, the first detected case of such objects, gamma Cas, was found to be actually atypical amongst them!

    Indeed, it emits very bright and extremely hard X-rays with a luminosity intermediate between that of normal massive stars and that of high-mass X-ray binaries. Recent efforts in X-ray monitorings have revealed that such objects are not uncommon hence gamma Cas stars are important ionizing sources, particularly at low metallicities where Be stars abound. The properties of these stars will be reviewed using the latest observational results.

    LAM seminar: Laurent Lamy

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    The (spring) magnetosphere of Uranus probed by a decade of HST observations of its ultraviolet aurorae

    The re-detection and long-term monitoring of the ultraviolet aurorae of Uranus with the Hubble Space Telescope during the past decade has provided a new, so far unique, mean to remotely investigate from Earth the asymmetric magnetosphere of Uranus since its discovery by Voyager 2, while waiting for a future orbital mission. Various spectro-imagers have been used to collect instantaneous images and spectra of the aurorae and of the underlying atmosphere in the Far UV range under variable solar and solar wind conditions. The observations were obtained through a series of programs executed between 2011 and 2023, aimed at sampling various timescales ranging from a fraction of a planetary rotation (~17.24h) up to seasons. This time interval provided the opportunity to sample radically different magnetosphere/solar wind configurations between equinox and solstice. In this presentation, we review the properties of the auroral and airglow emissions, in terms of spatial distribution, energy budget, dynamics and new constraints brought onto the internal rotation period. We highlight how these results will help to prepare the observations to be acquired in orbit from a Uranus orbiter.

    Important : If enough time, the seminar will be followed by a 3D projection of movie of the terrestrial polar (borealis and australis) aurorae in the LAM amphitheater.

    LAM seminar: Henri Bonnet (ESO)

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    Wavefront architecture of the ELT

    The ELT Wavefront Control manages the 5 mirrors of the telescope in position and shape and delivers at the interface with the instruments a beam quality compatible with diffraction-limited performance after correction by post-focal AO systems. This is obtained if the spectral distribution of aberrations in the temporal and spatial domains lies within the dynamics of M4, the deformable mirror of the telescope. In this talk, I will present some properties of the ELT aperture, discuss the main components of telescope dynamic disturbances whose spectral distribution exceeds the envelope of the free atmosphere, and describe the elements of the telescope control strategy.

    Special LAM/ML seminar: Marc Huertas-Company – Deep learning the physics of galaxy formation

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    The availability of statistical samples of galaxies over the past decade has resulted in a global picture of galaxy formation which is successfully translated into modern cosmological simulations that reproduce realistic galaxies.

    However, most of the key physical processes that govern galaxy evolution are still largely unconstrained – as evidenced by the first JWST results at cosmic dawn – and, as such, are treated as subgrid physics in state of the art simulations. The data quality and complexity is progressing fast, which coupled with recent advances in AI, offers new opportunities to make progress in our understanding of the physics of galaxy formation.

    Following a general introduction, in my talk, I will discuss recent results from our group aiming at extracting information from large and multi-modal deep surveys and connecting cosmological simulations and observations using a variety of modern deep learning methods.

    LAM seminar: Akim Atek – Probing Cosmic Dawn and Cosmic Reionization with JWST

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    The JWST is revolutionizing our understanding of the early Universe by unveiling a wealth of bright galaxies at z>9 and faint AGNs at z>5. I will present the latest constraints on the overabundance of UV-bright galaxies at z>9, which is 10–100 times higher than galaxy formation models. I will discuss to what extent recent theoretical efforts can reproduce such observations, and how future wide-area surveys such as Euclid will help put stronger constraints on the bright-end of UVLF at z>8. On the other hand, faint galaxies, representing the building blocks of present-day galaxies, have eluded spectroscopic constraints, even with the deepest JWST campaigns so far. I will present the results of our UNCOVER survey, which combines ultra-deep NIRSpec spectroscopy with the strong lensing magnification of A2744 cluster. We characterize ultra-faint galaxies with intrinsic absolute magnitude between Muv=-17 and Muv=-15 at 6<z<8, and stellar masses down to 10^6 solar masses. I will discuss our plans to obtain the deepest observations on sky with the GLIMPSE program to the faintest galaxy population out to z=15 and beyond. 

    GRD Seminar Lucie LEBOULLEUX [IPAG]

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    Lucie Leboulleux researcher at IPAG will present her work about  “High-contrast imagers robust to segmentation-due errors and low-wind effect”. Here is an abstract of a presentation :

    Imaging and characterizing exoplanets down to Earth-like planets relies on instrument able to access objects with a contrast to their host star of the order of 10^(-10) to -10^(-8), at short angular separations (<0.1’’). However, such instruments are complex to design, extremely sensitive to optical aberrations and instabilities, and tend to be set on giant telescopes with a segmented mirror that increases the number of possible sources of instabilities: the Extremely Large Telescope (39m and 798 segments), the Thirty Meter Telescope (30m, 492 segments), the Giant Magellan Telescope (24m, 7 segments), possibly the Habitable World Observatory (ex-UVOIR) space telescope (6m)… Among other sources of errors, their coronagraphic instruments will be impacted by segment phasing errors: on LUVOIR, for instance, a 10^(-10) contrast implies phasing constraints down to 10pm RMS, which can currently not be accessed and maintained. During this seminar, I develop an innovative approach to this problematic, by telling the story of PASTIS (Pair-based Analytical model for Segmented Telescopes Imaging from Space), an analytical model first invented to characterize coronagraphic instruments and to set constraints on the telescope segment alignment, and then used to directly design instruments robust to segment phasing errors. This approach is also extended to two other types of aberrations expected on coming ground-based telescopes: post-adaptive optics system petaling effects and the low-wind effect, the latest already limiting VLT/SPHERE and Subaru telescope high-contrast performance.

    GRD seminar Laurie Paillier [ONERA]

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    Laurie Paillier research engineer at ONERA will present her work about optical links from ground to space. Here is an abstract of her presentation :

    Both the increasing imaging resolution of earth observation satellites and the advent of a space based globalized internet are currently urging for very high data rate transmissions between space and ground. With the promise to provide tens of Gbps per channel, optical links may become a major breakthrough technology, assuming that the
    technological assets developed for the fibered networks can be exploited. Especially, phase modulation techniques have demonstrated their tremendous efficiency for fibered networks. The aim of this work was to investigate the feasibility of their transposition to the case of satellite-to-ground optical links, accounting for their specificities: laser phase noise, Doppler effect, and the impact of propagation through the turbulent atmosphere and its correction by adaptive optics. We investigated for different turbulence conditions two architectures of digital receiver: one based on a phase-locked loop, and the other one based on an open loop approach. As expected, the importance of the quality of the adaptive optics correction is highlighted. This work opens prospects for a strong increase in the achievable bit rate for coherent telemetry links when using higher-order constellations (QPSK and beyond).

    GRD seminar Loïc Barbot [LAM]

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    Loïc Barbot PhD student will present his work on astronomical navigation. Here is the abstract of the presentation :

    Astronomical navigation is still studied in merchant or naval academies as a method to fix the position of a ship. Considered as an emergency technic, it is implemented by an observer measuring with the sextant the angle between the horizon line and a celestial body. After calculations and plots, the position is obtained with an accuracy of several nautical miles (1 NM = 1,852 km).
    Star tracking is used on satellites to measure their orientation in space in order to turn their solar panels towards the sun or their cameras and antennas towards the earth. This requires to identify several stars in the same field of view or in the fields of several star-trackers.
    To be reliable, a stellar positioning system must have an accuracy comparable to satellite positioning, should operate day and night, even at low altitude where the atmosphere is dense in aerosols. If the position of the stars and the algorithms are well mastered, the detection of stars by daylight remains a challenge.
    The MARIS STELLA project explores the potential of infrared cameras. The stars thus detectable are numerous but this technology has not yet reached its full maturity: the performances are improving over time. After a presentation of the current results, future tests will be described.

    LAM seminar: PRIMA: A space mission in the mid to far infrared

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    Denis Burgarella (LAM), Laure Ciesla (LAM) and Marc Sauvage (AIM).

    Abstract

    PRIMA (PRobe far-Infrared Mission for Astrophysics) is a NASA astrophysics probe project. This project is part of the APEX (Astrophysics Probe Explore), a space mission limited to the IR/far-IR and X-ray domains, which will be launched in July 2023.

    PRIMA consists of a 2-2.5m telescope, cooled to 6K, and will cover the 25-300 micron range. PRIMA has both spectroscopic (R~200 and R~5000) and imaging (R~10, also including polarised channels) capabilities.

    The objective of this webinar is to present the mission, its organisation, technical characteristics and capabilities, as well as its scientific objectives. The webinar will be an opportunity to describe the involvement of French laboratories (LAM, DAp) and CNES support in the mission, and to identify the interests of the community. The presentation will be given in English. It will last 40 minutes to allow time for discussion.

    Find the recording of this seminar here.