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    Laboratoire d’Astrophysique de Marseille

    JWST

    LAM seminar: Guillaume Mahler – SLICE – Strong LensIng and Cluster Evolution from the largest JWST galaxy cluster survey

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    Clusters of galaxies are powerful cosmological probes sampling the high-mass end of gravitationally bound systems, providing stringent tests of the structure formation paradigm. A well-understood selection function based on Sunyaev-Zeldovich and X-ray-selected clusters provides an ideal framework for investigating key features of their evolution and the prevalence of self-similarity. Furthermore, the frequency of strong lensing evidence within these structures makes them an ideal target for studying the co-evolution of baryonic and dark matter. The JWST NIRCam program SLICE samples this parameter space over 8 Gyr of cluster formation history (0.2 < z < 1.9), demonstrating the unique ability of deep high-resolution NIR imaging to reveal lensing evidence and cluster-core morphology.

    With the first few tens of cluster lens models in hand, I will present an early analysis of these data. I will first show how new lensing constraints contribute to cluster mass modelling, and how the presence of newly discovered dusty lensed galaxies and new substructures in previously recognised lensed background galaxies affects it. In the second part, I will demonstrate how cluster properties evolve over cosmic time — including the dark matter core profile, the morphology of the brightest cluster galaxy, the intra-cluster light distribution, and the globular cluster population.

    LAM seminar by Andy Bunker: The high redshift frontier with JWST – studying the most distant galaxies with NIRSpec

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    Title: The high redshift frontier with JWST – studying the most distant galaxies with NIRSpec

    Abstract:

    I will give an overview of results on the highest redshift galaxies from the Guaranteed Time Observations of the NIRSpec Instrument Science Team, including those co-ordinated with the NIRCam Team as part of the JWST Advanced Deep Extragalactic Survey (JADES). We have used the multi-object microshutters on NIRSpec to target several thousand galaxies in the GOODS fields, including several hundred at redshifts beyond 6 (within the epoch of reionization) and have spectroscopically confirmed galaxies beyond redshift 14 for the first time (including a very UV-luminous galaxy at z=14, where bursty star formation or potentially a top-heavy initial mass function may be brightening the UV). NIRSpec spectroscopy at 1-5microns is sensitive to rest-optical emission lines over a wide range of redshifts and means that we can study the evolution of dust attenuation, star formation rates, metallicity, chemical abundances, ionization and excitation mechanism in galaxies out to high redshifts. Highlights include discovery of a nebular-dominated Balmer jump galaxy at z~6 with possibly a top-heavy IMF, and GNz11 at z=10.6 with Ly-alpha in emission and elevated N/O.

    LAM seminar by Guido Roberts-Borsani: “Between the extremes: JWST insights into the physics of the first stars, galaxies, and black holes”

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    Title: Between the extremes: JWST insights into the physics of the first stars, galaxies, and black holes

    Abstract:

    The emergence of the first sources ~13.6 billion years ago had a profound effect on the Universe, initiating its last major phase-change and ending the so-called cosmic Dark Ages. Unlocking the physics of those primordial sources thus represents a fundamental step towards a comprehensive understanding of the initial conditions that formed the building blocks for the Universe we see today. While Hubble painted a fairly straight forward picture, early JWST data revealed an infant Universe far more remarkable and exotic than previously thought, with hyper-luminous galaxies detected out to z~14, chemically-enriched interstellar media and peculiar elemental abundances out to z~12, and apparently over-massive black holes to z~10. Are these sources representative of the global population, or do they reflect peculiar objects at a particular evolutionary phase? In this talk, I will present efforts to address these questions through the spectroscopic study of statistical samples of high-redshift (z>5-14) galaxies with JWST/NIRSpec, establishing a benchmark for their chemical enrichment journeys, ISM conditions, (re)ionizing capabilities, and spectroscopic fingerprints. Additionally, I will showcase the importance of utilizing unbiased samples of galaxies to gain representative insight into the ISM conditions and evolutionary pathways of the most luminous populations uncovered by JWST.

     

    LAM seminar: Franz Erik Bauer – Little Red Dots Near and Far

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    So-called ‘Little Red Dots’ appeared in the very first deep extragalactic JWST surveys and their unusual properties have confounded astronomers ever since. They appear to be dominated by luminous point-like emission comprised of broad hydrogen emission lines and a continuum which rises both to the rest-frame UV and NIR, with an inflection around 4000A. They have generally ascribed to obscured AGN, but exhibit few other traits typically of accreting SMBHs. I will review what we know about these objects thus far and discuss potential origins.

    LAM seminar: Max Franco – Unveiling Galaxy Formation and Evolution in the First Billion Years of the Universe with the James Webb Space Telescope

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    The James Webb Space Telescope (JWST) is revolutionizing our understanding of galaxy formation and evolution in the early Universe. In this seminar, I will discuss how JWST has reshaped our view of the first billion years of cosmic history, from the emergence of the earliest galaxies to their role in cosmic reionization. In particular, I will highlight the crucial contribution of large-area surveys like COSMOS-Web in detecting rare and distant objects, mitigating cosmic variance, and establishing connections between galaxy properties and their environment. Finally, I will provide an overview of the latest insights enabled by JWST in the COSMOS field.